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CHAPTER II

REVIEW OF LITERATURE

The research work related with the topic of present investigation is reviewed and presented under suitable heads.

I. Effect of organic manures on growth and yield of rice

Reddy et al. (1972) found that application of gliricidia green manure @ 7.5 or 15 t ha-1 + 120 kg N, 60 kg P2O5 and 60 kg K2O ha-1 significantly increased plant height, number of tillers, filled grains per panicle of rice over control. The response to the addition of green leaf manure was quadratic. Jaggi and Russel (1973) observed that green manure significantly influenced the number of tillers per hill and leaf area index; however, it did not affect the height of main shoot significantly.

In the field trials carried out for six seasons on clay loam soil of Cuttack, Jha et al. (1980) noted that application of green manure @ 5-10 t ha-1 was very useful for improving the growth rate. They reported that application of green manure (Ipomea cornea) was very useful for improving the grain and straw yields of rice through increased number of ear bearing tillers m-2. Tiwari et al. (1980) opined that application of green manure was very useful for improving the grain and straw yield through increased number of ear bearing tillers. Bhardwaj et al. (1981) showed that green manuring of sunnhemp, dhaincha and Ipomea carnea @ 15 t ha-1 in combination with 0, 30, 60, 90 kg N ha-1 increased the number of tillers m-2 and dry matter accumulation. They also marked that the incorporation of Crotalaria juncea and Sesbania canabina significantly increased the grain yield of rice on irrigated land. The prediction equation perceived that there was saving of 49.9 and 23.3 kg N ha-1 by green manure with Crotalaria juncea and Sesbania canabina, respectively.

Khind et al. (1982) detected that irrespective of the use of green manure crops, the combined use of 60 kg N ha-1 as urea and green manure gave almost equal yield of rice as obtained with 120 kg N ha-1 through urea alone. This suggested that all green manures were equally effective and saved 60 kg N ha-1 or 130 kg urea in rice. Khind et al. (1983) spotted that, when 30, 45 and 60 days old crop with dhaincha (Sesbania aculeata) incorporated one day before transplanting of rice the amount of green matter, dry matter accumulation and nitrogen added increased progressively with the increase in age of Dhaincha. The increase in the yield with the incorporation of 60 days old dhaincha was equivalent to those obtained with application of 120 kg N ha-1 through urea.

Jamdade (1985) viewed that application of 40 kg N ha-1 + green manure of Sesbania aculeata and Gliricidia maculata @ 10 t ha-1 was comparable with a dose of 120 kg N ha-1 through fertilizer alone. Jamdade and Ramteke (1986) monitored that incorporation of dhaincha and gliricidia increased the number of tillers, dry matter accumulation, number of panicles, thousand grain weight, number of filled grains per panicle as compared to no green manure, which in turn produced the highest grain yield of 52.12 and 52.09 q ha-1, respectively. Antil et al. (1988) studied that the grain and straw yield of rice were significantly higher after application of green manure of dhaincha and moong compared to fallow and maize. The beneficial effect of green manure was mainly due to steady release of nitrogen during crop season.

Kolar and Grewal (1988) examined that burying sesbania, cowpea and sunnhemp resulted in significant increase in grain and straw yield of rice. Balasubramaniyan and Palaniappan (1989) judged a significant effect of green manure on leaf area index and numbers of panicles as compared to control, but the filled grains per panicle was not much affected due to green manure. The result of 2 years study scrutinized by Maskina et al. (1989) on the effect of integrated use of organic and inorganic sources of nitrogen on growth of rice showed that application of 120 kg N ha-1 was significantly superior over 60 kg N ha-1 in terms of dry matter accumulation and plant height. Halepyati and Sheelavantar (1990) and Rajput and Warsi (1992) stated that FYM was superior to that of wheat straw in increasing the grain yield of rice. Shivkant and Rajkumar (1992) concluded that application of FYM and green manure to rice increased the grain yield by 11 to 26% as compared to control.

Bal et al. (1993) registered that all the yield contributing characters viz., number of panicles per hill, length of panicle, number of filled grains per panicle, thousand grain weight were significantly influenced by the application of gliricidia and FYM @ 5 t ha-1 as compared to control ultimately resulting in increased grain and straw yield of rice. They further observed that incorporation of gliricidia green leaves 5 t ha-1 at the time of puddling resulted in 50% saving in recommended dose of fertilizer nitrogen and also increased organic carbon content of lateritic soils of Konkan compared to the application of FYM @ 5 t ha-1 and no organic manures. The superiority of gliricidia over FYM was mainly due to low C:N ratio i.e. 15:1 of gliricidia as compared to FYM (20:1).

Pandian and Perumal (1994) observed that incorporation of green manure alone (12.5 t ha-1) without mineral nitrogen recorded 11.9% more grain yield as compared to control. Verma and Bhagat (1994) found that plant growth parameters and yield contributing characters were affected positively by the incorporation of poultry manure and FYM resulting in the highest grain and straw yield of rice. Jaychandran and Veerabadran (1996) noted that the application of green manure i.e. Sesbania rostrata increased the plant height, leaf area index and total number of tillers compared to the other green manure crops such as Sesbania aculeata and Crotalaria juncea. Incorporation of gliricidia leaves @ 5 t ha-1 at the time of transplanting significantly increased the grain (31.43 q ha-1) and straw (59.82 q ha-1) yields of rice over no green manure by 8.68 and 11.21%, respectively (Turkhede et al., 1996). Talashilkar and Chavan (1997) reported that incorporation of 10 t ha-1 of gliricidia leaves just before transplanting of rice significantly increased growth parameters and produced as much rice yield as produced by the application of 100 kg N ha-1.

Talathi (2001) observed that the height of rice plant, number of leaves, number of tillers and dry matter accumulation per hill was significantly higher with application of 50% recommended NPK through fertilizers + 50% N through gliricidia, which was closely followed by 50% recommended NPK through fertilizers + 50% N through FYM. Rice supplied with 50% recommended NPK through fertilizers + 50% N through gliricidia produced higher number of panicles per hill, length of panicles, number of grains and weight of grains per panicle. They also observed that Application of 50% recommended NPK through fertilizers + 50% N through gliricidia, 50% recommended NPK through fertilizers + 50% N through FYM to rice recorded 105.41 and 103.33% higher grain yield compared to that of 100% recommended NPK, respectively, while 50% recommended NPK through fertilizers + 50% N through gliricidia produced higher straw yield of rice followed by 50% FYM substitution.

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II. Effect of inorganic fertilizers on growth and yield of rice

Jindal and Kalia (1971) opined that successive increase in fertilizer levels (0:0:0, 50:25:25, 100:50:50, 150:75:75 kg ha-1) produced significantly higher rice yield over the preceding level. Katyal (1978) observed no adverse effect on grain yield of transplanted rice grown during the wet season, when phosphorus application was delayed up to 3 weeks after transplanting. The high concentration (quantity factor) of phosphorus in the soil solution near the UB-DAP placement sites may have helped to ensure adequate phosphorus uptake by the rice plants and thus resulted in overall higher efficiency of the deep placed UB-DAP as a N and P source.

Purushothaman and Palaniappan (1978) from two years study at Tamil Nadu Agricultural University, Coimbatore showed that yield variation due to fertilizer levels was significant in both the years. Recommended dose of NPK to rice crop registered the highest grain yield and was significantly superior to rest of the treatments. Sawant and DeDatta (1980) and Gaudin (1987 & 1988) studied the working of UB-DAP and reported that rice roots develop and reach the placement sites, absorption of the nutrients begin from the periphery of the soil-urea reaction zones that are below the toxic concentration of ammonia. The steep ammonium concentration gradients near the placement sites seem to control the rate and to prolong the duration of availability of the deep placed nitrogen to the rice plants due to phosphate fixation by soil all the DAP-P stays in the sub-soil and diffuses only a few centimeters away from its placement sites (Gaudin, 1987 and Sawant and Stangel, 1990).

Menon et al. (1990) reported that minimum fixation of DAP-P occurs in soil due to its point placement therefore, more phosphorus remains in soil solution at the placement sites and more phosphorus becomes available to the rice plants. The incorporated SSP-P the fixation of phosphorus by soil is maximum resulting in less phosphorus in soil solution and eventually less phosphorus available to the rice plants. Sawant and Stangel (1990) observed that there are no losses of applied nitrogen (as surface runoff and ammonia volatilization) and phosphorus (as surface runoff) for the deep placed UB-DAP. The result of greenhouse experiment using 32P-tagged DAP and triple super phosphate suggested that the deep placement of UB-DAP can practically eliminate surface runoff loss of phosphorus. This delay in phosphorus availability seems to have no adverse effect on grain and straw yield.

Sawant and Friesen (1992) reported by a greenhouse study without rice plant, 32P as 2.7 g UB-DAP (N:P=4:1) deep placed at about 10 cm soil depth moved 3 cm away from its placement site in about 20 days and up to 4 cm in 30 days after placement. The spatial non-availability of DAP-P to the rice plants, due to the combined effect of fixation and very restricted movement of phosphate in soil could be overcome by reducing the distance between the UB-DAP tagged with 32P was deep placed immediately after transplanting, the shorter distance between its placement site and the rice hills of the modified 2020 cm spacing apparently enabled the rice roots to intercept DAP-32P about 10 days earlier than the distance of the regular 2020 cm spacing. This improvement in the spatial availability of fertilizer phosphorus could be more important in phosphorus deficient soils. Raju et al. (1993) marked that application of 50, 75 and 100% of the recommended NPK through inorganic fertilizer increased the yield by 29.8, 54.8 and 93.3%, respectively compared with control. Rana and Bhandari (1993) perceived from studies in rice-wheat system for 8 years that application of 100% recommended NPK fertilizer to both rice and wheat was essential for getting sustained productivity.

Sawant et al. (1993) reported that for 60 to 80 kg N ha-1 and 15-20 kg P2O5 ha-1, the deep placement of UB-DAP (1 UB-DAP per 4 hills) increased grain yields (11% to 86%), straw yield (9% to 62%) and total nitrogen uptake (but not phosphorus uptake) as compared with the SSP + PU. This attributed to the increased efficiency of deep placed UB-N and the adequate availability of DAP-P to the rice plants. The additional yields for the deep placed UB-DAP were obtained at 15 to 35 per cent low hill population than that for the SSP + PU. This saving in seed and other nursery related inputs can help the farmers to offset the additional labour cost of the UB placement. The estimated benefit cost ratio for the UB-DAP varied from 7.1 (without considering of seed saving) to 13.8 (with consideration of seed saving). Similar results were reported by Kumar et al. (1989) and Sawant and Stangel (1990).

Based on field experiment at Regional Research Station, Kanungo and Roul (1994) detected a significant increase in rice grain and straw yield with 100% recommended NPK. They further spotted that effective tillers per hill, panicle length, filled grains per panicle and thousand grain weight increased with increasing levels of fertilizers. Panda et al. (1995) viewed that grain and straw yield of rice increased significantly with increasing levels of inorganic fertilizers. The response was limited up to moderate dose on plant height. Application of 100% recommended dose of NPK recorded the highest plant height for two consecutive years. Sheela and Thomas (1995) also scrutinized similar findings.

Sawant (1995) noted 4.55 and 6.66 t ha-1 of grain and straw yield, respectively in the treatment receiving integrated use of deep placed UB-DAP and gliricidia green manuring @ 3 t ha-1, while a PU + SSP application resulting into 2.99 and 4.54 t ha-1 of grain and straw yield respectively with conventional method. Gangwar and Sharma (1996) monitored that yield components such as tillers m-2, panicle m-2 and thousand grain weight in rice and tillers m-2 and ear length in wheat were affected significantly due to use of recommended dose of NPK through chemical fertilizer along with management practices in rice-wheat system. This was because of the substantial boost to growth of rice and wheat provided by the integration of nutrients with different management practices such as weed control and plant protection measures.

Jana and Ghosh (1996) and Pathak and Ghosh (1996) studied that grain yield of rainy season rice was higher under 100% recommended dose of NPK supplied through inorganic source alone. Application of NPK at sub optimal dose i.e. 75% and 50% of the recommended dose reduced the grain yield. The total land productivity in rice-rice crop sequence was higher, when both rainy and winter season rice received 100% recommended dose of NPK. Chinnusamy et al. (1997) examined that rice grain and straw yield due to 75% NPK were comparable with 100% NPK because of combined use of chemical fertilizers and organic manures. Daftardar et al. (1997) recorded 4.55 t ha-1 of grain yield of rice with UB-DAP @ 56 kg N + 14 kg P2O5 ha-1), while they obtained 2.99 t ha-1 of grain yield with PU + SSP applied at same rate of nitrogen and phosphorus in 26 field trials conducted on the west coast of Maharashtra State.

Pradhan and Mondal (1997) and Turkhede et al. (1998) judged that there was corresponding increase in grain and straw yield of rice with every increase in the level of fertilizers and maximum yield was recorded with recommended dose of fertilizer i.e. Fertilizers 100:50:50 kg ha-1 compared to all the other levels. The grain yield decreased significantly with reduction in NPK dose. Similar results were also stated by Dungrani et al. (2000). A field experiment was conducted to study the effect of UB-DAP on nitrogen and phosphorus uptake in rice by Sawant (1998). He observed 101.9 and 22.9 kg ha-1 nitrogen and phosphorus uptake respectively in the treatment receiving UB-DAP (60 kg N + 30 kg P2O5 ha-1), while 39.0 and 9.7 kg ha-1 nitrogen and phosphorus uptake, respectively were observed in control treatment receiving no nitrogen and phosphorus.

Sawant and Daftardar (1998) conducted 165 adaptive research trials on farmers field in Konkan region with improved management consisting of deep placing (10 cm) urea briquettes containing diammonium phosphate (UB-DAP) by hand (56 kg N ha-1 and 14 kg P2O5 ha-1) after controlled transplanting using a modified 2020 cm hill spacing with two other practices, i) the current management system consisting of random transplanting and split application of prilled urea and a basal application of single super phosphate, and ii) the farmers traditional management practices involving random transplanting and broadcasting of fertilizers. In spite of marked variations of rainfall distribution pattern during the cropping season in different years, the improved management of UB-DAP placement (one briquette at centre of four hills) increased grain yield by an average of 1.5 t ha-1 (60%) over traditional management practice and by average of 0.6 t ha-1 (30%) over that of the current management system.

Dhamapurkar (1999) reported that deep placing of urea briquettes containing diammonium phosphate in transplanted rice using modified 2020 cm hill spacing, integrated with basal incorporation of 4 to 6 t ha-1 of calcium silicate slag containing 45 per cent SiO2 is an efficient management for increasing rice yields with less fertilizer, consistent with improvement in soil fertilizer. Gill et al. (2000) at Ludhiana concluded that there was consistent increase in the grain yield of rice with the increase level of fertilization and the highest yield was obtained, when 100% RDF was applied followed by 50% RDF.

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III. Effect of inorganic fertilizers on growth and yield of mustard

Singh and Moolani (1969) registered significant increase in height, number of branches and number of siliquae of brown sarson at 100 kg N + 25 kg P2O5 ha-1 as compared to control. Singh and Tomar (1971) found that the application of 70 and 140 kg N ha-1 in addition to the basal dressing of phosphorus and potassium gave seed yield of 845 and 963 kg ha-1, respectively compared with 562 kg ha-1 of plots that were given only phosphorus and potassium. Application of phosphorus and potassium alone showed little effect on yield. Bhan and Singh (1975) observed that the highest fertilizer level of 120 kg N + 60 kg P2O5 and 60 kg K2O resulted in the maximum yield (23.5 q ha-1) of mustard giving significant difference of 3.18 and 5.26 q ha-1 over half the dose viz., 60 kg N + 30 kg K2O ha-1 and unfertilized plots. They also noted that there was increase in number of branches, siliquae per plant, seeds per siliquae and siliquae length by fertilizer application. It helps to enhance yield of grain per hectare. The other favorable effect of fertilizer application was to hasten maturity of the crop.

Chundawat et al. (1975) from Jaipur reported that application of 60 kg N + 60 kg P2O5 + 30 kg K2O ha-1 showed higher results over other treatments. Vir and Verma (1979) opined that application of 50.6 kg N + 367 kg P2O5 ha-1 increased the number of primary and secondary branches, number of pods, weight of pods and total dry weight per plant. Mudholkar and Ahlawat (1981) showed that the plant height, dry weight, number of pods per plant, seed yield and thousand seed weight increased with increasing N (0 to 80 kg) and P2O5 (0 to 80 kg) rate. The optimum phosphorus rate was 68.9 kg ha-1. They further marked that response of phosphorus was better in the presence of nitrogen.

Roy et al. (1981) perceived that the average seed yield of Brassica juncea Cv. Varuna increased from 0.74 t ha-1 without nitrogen to 1.83-1.84 t with 180-240 kg N ha-1. Yield of crop was increased from 1.27 to 1.71 t ha-1 with an application of 52 kg P2O5 + 120 kg N ha-1, but difference was not significant. Yield did not increase with 100 kg K2O ha-1. The oil content in seed increased with NPK treatment interaction. Vaidya et al. (1981) in trials with mustard (Brassica juncea) grown on brown soil supplied with 0-80 kg N, 0-60 kg P2O5, 0-30 kg K2O and 0-50 kg sulphur detected that average and interactive effects of these fertilizers were significant in increasing seed yield.

Saini (1982) from Ludhiana spotted that Rai utilized more nitrogen. It also responded well to application of phosphorus, sulphur and micronutrients. Joarder (1983) viewed that Brassica compestris supplied with 100 kg N + 80 kg P2O5 + 60 kg K2O ha-1 showed increase in seed yield as compared to other treatments. Seed yield increased with irrigation and fertilizer rates, while oil contents were lower in irrigated plots. Roy and Tripathi (1983) scrutinized that the fertilizer level 80:40:40 kg ha-1 proved beneficial. The multiple correlations were highly significant, when yield was taken in terms of siliquae per plant, grain number per siliquae and test weight. The phosphorus and potassium concentration in the plant increased with increase in fertilizer level from 20:10:10 to 60:30:30 ha-1.

Dhillon and Vig (1985) from Ludhiana monitored that nitrogen application up to 120 kg N ha-1 significantly increased raya grain yield from 531 kg to 1382 kg ha-1 both with and without applied phosphorus, but with phosphorus application at the rate of 40 kg P2O5 ha-1 in conjunction with 120 kg N ha-1 grain yield increased from 1382 to 1543 kg ha-1. Zaman (1985) studied that seed yield of local cultivar grown conventionally was 0.95 t ha-1, when it was supplied with 60 kg N + 40 kg P2O5 + 40 kg K2O ha-1 with pest and weed control, yield increased from 0.95 t ha-1 to 1.70 t ha-1 under rainfed and irrigated conditions, respectively.

Chaudhary and Bose (1986) examined that the application of 75:37.5 kg N and P2O5 ha-1 and two irrigations given at 4 weeks after germination and pod formation noted higher yield over control and Fertilizers 25:12.5:12.5 kg ha-1 with same irrigation. Ilin (1986) judged that various combinations of NPK fertilization increased seed yield of spring rape by 0.17 to 0.5 q ha-1 as compared to control (0.08 t ha-1). The highest grain yield was achieved with Fertilizers 180:40:60 ha-1. NPK markedly increased nutrient uptake. Higher NPK dose decreased oil content compared with control and lower fertilizer doses. The total oil production was the highest with application of Fertilizers 180:40:60 ha-1. The treatment produced considerable biomass. Valero and Haq (1986) from Bangladesh stated that yield response and economic return in wheat-mustard followed the trend of application of NPK>NP>N>control. Patil et al. (1989) registered that the application of 90 kg N and 45 kg P2O5 ha-1 to mustard gave 3 years of average yield of 1.64 t as compared with 0.75 t without nitrogen and phosphorus.

Dongale et al. (1990) from Maharashtra found that mustard showed graded and significant response to increasing levels of nitrogen and phosphorus fertilizers. The crop should be fertilized with 90 kg N + 45 kg P2O5 ha-1 for the highest grain yield (16.38 q ha-1) and highest additional returns (Rs. 8993 ha-1). Fertilizers considerably enhanced the consumptive use efficiency and also water use efficiency. They observed that growth parameters like height, number of leaves per plant, number of grains per pod, branches per plant, dry matter accumulation per plant and flowering was also significantly influenced due to the application of 80 kg N + 45 kg P2O5 ha-1 under lateritic soils of Konkan region.

Narayanswamy (1990) noted that application of N120:P60:K15 gave seed yield of 8.11 q ha-1. Singh and Singh (1993) from Pantnagar reported that Fertilizers 90:90:60 kg ha-1 for Indian mustard would be the optimum fertilizer dose to get higher productivity. Arthamwar et al. (1996) from opined that each higher level of nitrogen significantly improved all the yield attributes. There was linear increase in seed yield and oil yield ha-1 due to nitrogen levels from 0 to 100 kg N ha-1. They also showed that every increase in the level of phosphorus significantly improved all the yield attributes, seed yield, oil content and yield of Indian mustard.

Tomar et al. (1996) marked that plant height, number of branches, dry matter accumulation, number of siliquae, thousand seed weight, seed and oil yields increased significantly with the increasing levels of fertilization up to 120:60:60 kg ha-1. Patel and Shelke (1998) from Maharashtra perceived that application of phosphorus up to 80 kg P2O5 ha-1 showed linear increase in growth, yield contributing characters and seed, as well as stover yields of Indian mustard.

Kumar and Bhogal (2000) detected that there was linear increase in seed yield of mustard due to increase in the nitrogen levels up to 120 kg N ha-1, which was due to increased branching, siliquae per plant and seeds per siliquae. The protein content also increased significantly with increasing levels of nitrogen per hectare. The oil content increased with increasing levels of nitrogen up to 40 kg N ha-1 and thereafter it decreased. Singh and Singh (2000) spotted that mustard yield increased significantly with each successive increment of 40 kg N up to 120 kg N ha-1. The highest level of nitrogen (160 kg N ha-1) produced highest seed yield ha-1, while the difference between 120 and 160 kg N ha-1 was not significant.

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IV. Effect of organic manures and fertilizers on physical properties of soil

Havangi and Mann (1970) based on long term studies stated that the bulk density was greatly decreased due to continuous application of FYM (1.43 Mg m-3) compared to control (1.45 Mg m-3) and 1.46 Mg m-3 in fertilizer treatments. Biswas et al. (1971) at Sabur registered that the application of potassic and phosphatic fertilizers either alone or in combination showed improvement in soil aggregation (35.5 to 49%) as compared to control. Application of nitrogenous fertilizers either alone (28%) or in combination with phosphate and potash decreased the structural properties of soil (28-32.4%). They further found that inorganic fertilizers increased the bulk density.

Bavaskar and Zende (1973) registered significant decrease in bulk density with the continuous application of organic manures in conjunction with chemical fertilizers. This may be due to application of additional quantity of organic manures destroying the development of hard pan in soil thus lowering down the bulk density. Gattani et al. (1976) noted that the continuous use of chemical fertilizers alone or in combination resulted in increase in bulk density whereas FYM alone and FYM + NPK through chemical fertilizers helped in keeping the bulk density value same as that of control. The water holding capacity (WHC) of soil was improved due to continuous use of FYM. Chatterjee et al. (1979) reported that green manure decreased the bulk density of soil significantly compared to control.

Prasad and Singh (1980) opined that continuous use of FYM and NPK fertilizers helped in maintaining physical properties of soil, but application of chemical fertilizers alone slightly deteriorated soil physical properties. Use of only chemical fertilizers increased the bulk density of soil compared to combined application of organic manures and chemical fertilizers. This may be attributed to deterioration of soil structure by inorganic fertilizers. Shanmugam and Ravi (1980) and Kapur et al. (1981) showed that incorporation of crop residue and FYM decreased the bulk density, where as hydraulic conductivity, porosity and aggregates stability were increased there by improving physical properties of soil. Helkaih et al. (1981) marked that application of FYM @ 30 t ha-1 with half dose of recommended NPK through chemical fertilizers significantly decreased the bulk density over control and fertilizer alone.

Bhatia and Shukla (1982) perceived that application of FYM @ 120 kg N ha-1 decreased the bulk density to 1.14 Mg m-3. They further noted that there was increase in the bulk density due to chemical fertilizer alone, which was mainly due to deterioration of structure by nitrogenous fertilizers. Prasad et al. (1983), Rabindra et al. (1985) and Gupta et al. (1986) detected that increasing dose of chemical fertilizers (50% to 150%) increased the bulk density of soil from 1.43 to 1.59 Mg m-3. On the other hand, Mahimairaja et al. (1986) spotted that the graded dose of NPK fertilizers had no significant influence on bulk density and pore space, but significantly influenced the hydraulic conductivity and soil aggregate parameters after the harvest of 27th maize crop.

Rabindra et al. (1985) and Bhatia and Ganguly (1984) based on long term experiment at Mandya (Karnataka) viewed that application of urea alone increased the bulk density from 1.84 to 1.92 Mg m-3 as compared to control, while there was significant reduction in bulk density of soil from 1.81 to 1.66 Mg m-3 with the normal dose of FYM + NPK. Gupta et al. (1986) scrutinized that the application of city compost caused significant decrease in bulk density from 1.37 to 1.32 g m-3 and increased the WHC from 25.2 to 27.8% there by improving the physical status of soil.

Rabindra and Gowda (1986) monitored significant increase in organic carbon content and total nitrogen in soil with the application of balance chemical fertilizers (NPK) after 12 years. Similar results of increase in organic carbon with the application of increasing dose of balanced fertilizer were also studied by Minhas and Mehta (1984) and Raghuwanshi et al. (1988). Sharma et al. (1988) and Sur et al. (1993) examined that green manure had favorable effect on all the soil physical properties. It decreased bulk density and increased WHC of soil. Garg et al. (1991) judged that the bulk density of soil decreased from 0.06 to 0.12 Mg m-3 under different organic amendments as compared to control and also there was improvement in WHC of soil. The effectiveness of different amendments followed the order i.e. FYM>Fly ash>wheat straw>control. Lomte et al. (1993) stated that increase in organic carbon content was 12.6 and 4% for the 100% NPK and 50% NPK, respectively over 25% NPK application.

A field experiment was conducted by Sharma and Sharma (1993) at the Research Farm of HPKV, Palampur on rice-wheat cropping system. The results revealed that there was a reduction in bulk density from the initial value of 1.32 to 1.28 Mg m-3 in the manured plots, while unmanured plots did not show any changes. Meelu et al. (1994) concluded that green manure, FYM and crop residue helped to improve the soil physical conditions through microbial cells, decomposition products and penetration of fine roots. More (1994) registered that by the application of different organic manures there was reduction in bulk density.

Prasad (1994) at Pusa conducted a trial on rice-wheat cropping system with different combinations of chemical fertilizers and organic manures. The lowest bulk density was observed due to NPK + FYM + BGA followed by NPK + FYM and the highest being in the control plot. These results suggested that organic manures and biofertilizers play important role in improving the physical environment of soil. Malewar and Hasnabade (1995) found that the combined application of chemical fertilizers and organic manures decreased the bulk density. They also observed that bulk density of soil decreased due to combined application of fertilizers with organic manure. The decrease in bulk density was partly attributed to the increase in porosity and high accumulation of organic matter. Kumar and Singh (1997) scrutinized the reduction in bulk density, when FYM was applied as compared to no FYM. Similar findings have also been reported by Yin-Po-Wang and Chen-Ching-Cho (1995).

Mishra and Sharma (1997) reported that the continuous addition of balanced fertilizers did not show any deteriorating effect on physical properties of soil rather it significantly reduced the bulk density. They also opined that the balanced use of fertilizers alone and in combination with organic sources did not show any deteriorating effect on physical properties of soil, but it significantly reduced the bulk density where as Dongre (1997) showed that continuous use of chemical fertilizers alone had adverse effect on soil properties viz., bulk density and WHC. Application of FYM and gliricidia (62.5 kg N ha-1) for 15 years resulted in significant reduction in bulk density and increased WHC.

Selviranganathan and Augistine (1997) and Bellakki et al. (1998) marked increase in WHC of lateritic soil by application of different organic manures. The increase was in the range of 19.3 to 27.4% over NPK alone. They also perceived that application of FYM recorded the highest WHC i.e. 46.4% followed by mushroom spent, rice straw compost and composted coir pith. Ramteke et al. (1998) detected that the application of FYM @ 10 t ha-1 significantly reduced the bulk density of soil as compared to the initial value after harvest of rice. There was remarkable increase in WHC by application of FYM followed by vermicompost @ 10 t ha-1 and gliricidia @ 10 t ha-1 along with 50% of recommended dose of chemical fertilizers.

Yadav (1998) viewed that 100% NPK applied through chemical fertilizers increased the bulk density significantly over the organic manure consisting of 50% substitution of NPK through vermicompost, gliricidia and FYM after harvest of rice, while later three treatments did not show any increase in bulk density over the initial value. Talathi (2001) recorded that application of 50% recommended NPK through fertilizer + 50% N through FYM significantly reduced the bulk density of the soil as compared to initial status after harvest of rice, whereas it increased with 100% recommended NPK through fertilizers after harvest of maize and groundnut. Application of 50% recommended NPK through fertilizers + 50% N through FYM showed remarkable increase in WHC of soil after harvest of rice, while 75% recommended NPK through fertilizers noted higher WHC after maize and groundnut.

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V. Effect of organic manures and fertilizers on chemical properties of soil

Kanwar and Prihar (1962) scrutinized that the continuous use of FYM and ammonium phosphate increased organic carbon and total nitrogen of soil. The increase in organic carbon ranged from 9 to 20% over control and from 8 to 12% over nitrogen alone in soils of Ludhiana. Biswas et al. (1971) in long term manurial experiment at Sabour monitored increase in organic carbon content of soil from 0.51 to 3.08% under FYM application @ 69.7 t ha-1 per crop, while application of only chemical fertilizers, the carbon content was close to control.

Gattani et al. (1976) examined low pH in the plots treated with 100% NPK applied through chemical fertilizers. Organic carbon content of the soil declined, when only potash was applied either alone or along with nitrogen, while application of NPK had either increased or maintained the initial status. They also judged significant increase in organic carbon content of soil from 0.19 to 0.24% due to FYM @ 40 t ha-1 in soil of Jaipur, Rajasthan. Formali and Prasad (1979), Singh et al. (1980) and Prasad and Singh (1980) stated that the application of FYM increased organic carbon, available NPK as compared to control. This may be due to decomposition and mineralization of organic matter. Mandal et al. (1982) after five years registered decrease in organic carbon content of soil to the extent of about 20% in the control plot. The minimum decrease was noticed due to 100% NPK + FYM @ 10 t ha-1. There was decrease in total nitrogen content by 12 to 18% in the soil. Similar trends were also registered by Mandal et al. (1984 & 1991) after 8 and 14 years of lapse period.

Prasad et al. (1983) and Prasad et al. (1986) concluded that available nitrogen significantly improved in all the treatments, where nitrogenous fertilizers were applied in combination with phosphatic and potassic fertilizers at higher levels as compared to control. 50% NPK showed depletion in nitrogen availability as compared to initial status (295 kg N ha-1) while 100% and 150% NPK showed enrichment in available nitrogen (333 to 368 kg N ha-1) as compared to initial value. Rayer (1984) found that FYM and poultry manure significantly increased the organic carbon content and WHC of soil as compared to swine manure. Kim et al. (1985) noticed that the application of cattle manure @ 10, 20 and 30 t ha-1 resulted in significant increase in organic carbon.

Singh and Brar (1985) observed that application of FYM along with urea significantly increased the organic carbon, available NPK over control. Kadam et al. (1986) and Singh and Singh (1987) noted that there was increase in available nitrogen in plots receiving gliricidia. Incorporation of gliricidia increased phosphorus availability more than that of dhaincha. Acharya et al. (1988) reported that FYM + 100% of the recommended NPK improved the organic carbon and available NPK status of soil. Incorporation of FYM in combination with 100% NPK maintained the available phosphorus at higher level compared to 100% NPK alone perhaps owing to the mineralization of organic phosphorus contributing to its accumulation in soil.

Jayaraman (1988) opined that chemical fertilizers and Leucaena leaf manure increased the available nitrogen, as well as organic carbon content of soil. Bhrigvanshi (1988), Blanc et al. (1989) and Udayasoorian et al. (1989) showed that addition of FYM had higher content of total nitrogen as compared to green leaf manure. On the other hand, Bhandari et al. (1992) and Bal et al. (1993) marked that incorporation of gliricidia @ 5 t ha-1 to rice increased organic carbon content in lateritic soils of Konkan indicating superiority of gliricidia green manure. Sharma et al. (1988) at Palampur perceived that application of Lantana as a green manure, rice husk and saw dust increased the organic carbon and also helped to increase the availability of NPK in soil as compared to control. Lantana as a green manure, rice husk and saw dust markedly increased the organic carbon by 29, 19 and 18%, respectively over control.

Kher (1991) detected that available NPK status increased under NPK treatment compared to control after 13 years of study. Agarwal et al. (1993) observed that available potassium content in plots receiving no potassic fertilizers ranged from 183 to 187 mg kg-1, which increased to 190, 201 and 212 mg kg-1 due to 50%, 100% and 150% NPK, respectively. Verma and Nandram (1994) also spotted improvement in available potassium status of soil due to balanced fertilization at higher level.

Kumar and Yadav (1993) carried out long term experiment at Faizabad with rice-wheat cropping system and viewed that organic carbon increased from initial value of 0.45 to 0.50-0.54% with high fertilizer level, however, unfertilized plot showed reduction (about 50%) in organic carbon after 12 years of cropping compared with initial value. It may be attributed to very poor crop growth and naturally poor root residues. Similar findings were also scrutinized by Subramaniam and Kumarswamy (1989).

Rana and Bhandari (1993) monitored that the balance fertilization not only proved beneficial for getting fairly high crop yield, but also maintaining the soil health in terms of organic carbon and available NPK. There was however a considerable build up of available phosphorus. Sharma and Sharma (1993) at Palampur worked on fertilizer management in rice-wheat cropping system and studied the build up of organic carbon in manured plots. There was increase in available NPK with increasing levels of fertilizers or organic manures, but the application of 50% NPK to both the crops registered a little depletion of all the three nutrients. Kumar et al. (1993) and Kolar and Gill (1994) also registered similar findings.

Bhardwaj and Omanwar (1994) judged that increasing doses of NPK (50 to 150%) increased the available NPK content of the soil. The nitrogen availability increased to a greater extent, when nitrogen was applied along with phosphorus and potassium fertilizers with higher doses. Hegde (1996) stated higher available nitrogen than unfertilized plots after 4 years of continuous cropping at Kharagpur. Application of 100% NPK through fertilizers in both the season resulted in higher available nitrogen. Jana and Ghosh (1996) concluded that application of 100% recommended dose of NPK through inorganic source increased the uptake of NPK by the plants in rice-rice sequence over 50% and 75% NPK. This higher uptake of NPK was due to greater release of nutrients and their ready availability in the soil.

Prasad et al. (1996) registered that the available NPK status declined after 6 years by 23, 44 and 16% in those either plots, where neither manures nor inorganic fertilizers were applied. Application of 50%, 100% and 150% NPK either in presence or absence of FYM showed on an average 10 and 23% increase in available nitrogen and phosphorus, respectively after 21 years of continuous cropping as compared to 6 years of cropping. The potassium status remained unchanged. On the contrary, the balanced fertilization and integrated nutrient supply system helped to enrich the available nutrient status of soil. The highest increase was in case of available phosphate (about 330% of average value) followed by available nitrogen (16%) and available potassium (8%) as compared to their initial status.

Sriramchandrasekharan et al. (1996) found higher availability of NPK and organic carbon due to green manure followed by FYM, composted coir pith and paddy straw. The maximum availability of nitrogen was due to green manure treated soil due to high nitrogen content i.e. 3%, whereas low values in paddy straw treated soil was due to wide C:N ratio i.e. 60:1, which retards mineralization. Basumantry and Talukdar (1997) at Assam Agricultural University studied the effect of integrated nutrient management in rice-rice sequence and observed that substitution of 25 or 50% N through FYM resulted in significantly high accumulation of available nitrogen and phosphorus than chemical fertilizers alone.

Kumar and Singh (1997) noted that application of FYM @ 10 t ha-1 to both rice and wheat crop increased available nitrogen and phosphorus status of soil over no application of FYM and initial value. The available potassium status found to be declined with FYM application as compared to initial values. Similar results of negative balance of available potassium were also reported by Prasad (1994) and Dongre (1997).

Ramteke et al. (1998) opined that there was a considerable decrease in soil pH due to chemical fertilizers alone, whereas FYM @ 10 t ha-1 helped in increasing soil pH and organic carbon after harvest of rice. Application of gliricidia @ 10 t ha-1 recorded the highest organic carbon content. Available NPK status increased by the application of vermicompost @ 10 t ha-1 + 50% recommended NPK followed by gliricidia and FYM combined with fertilizers. Turkhede et al. (1998) proved that incorporation of green foliage of gliricidia @ 5 t ha-1 improved fertility status, organic carbon and WHC and reduced the bulk density. Thakur et al. (1999) registered that continuous application of varying levels of nutrients (50%, 100% and 150% of recommended dose) maintained the available NPK content of the soil at higher level over the control.

Talathi (2001) recorded that application of 50% recommended NPK through fertilizer + 50% N through FYM registered the highest organic carbon content after rice, while there was slight decline in organic carbon content due to 100% recommended NPK after harvest of maize. In case of groundnut, there was improvement in organic carbon content of soil due to different treatments. Available nitrogen showed improvement with the highest availability under 50% recommended NPK through fertilizers + 50% N through gliricidia closely followed by 50% recommended NPK through fertilizers + 50% N through FYM after harvest of rice, while 50% recommended NPK through fertilizers + 50% N through FYM showed increase in available phosphorus followed by 50% RDF + 50% N through gliricidia. Available potassium showed slight depletion with 100% recommended NPK, but it increased with 50% recommended NPK through fertilizers + 50% N through FYM as compared to initial status followed by 50% recommended NPK through fertilizer + 50% N through gliricidia after harvest of rice. There was considerable decline in available NPK status of soil due to chemical fertilizers alone after harvest of maize, whereas there was improvement in nitrogen and phosphorus status after harvest of groundnut, but potassium status declined slightly due to application of chemical fertilizers alone.

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VI. Residual effect of organic manures and fertilizers applied to the preceding rice on growth and yield of succeeding crop

Ghosh (1980) reported that the residual effect of green manure may double the yield of succeeding cereal crop, but there was little benefit to the leguminous crop. Tiwari et al. (1980) observed increase in grain yield of succeeding wheat crop due to residual fertility retained after harvest of rice to, which green manure was applied. Maskina and Meelu (1984) found that the grain yield of wheat increased by about 0.9 t ha-1 due to favorable residual effect of applied FYM @ 12 t ha-1 to rice indicating a residual effect of 30 kg N and 13 kg P2O5 ha-1 for succeeding wheat crop. Mahapatra et al. (1987) noted a significant residual effect of applied dhaincha (60 kg N ha-1 + 30 kg N through Azolla inoculation) to preceding rice crop resulting in increased grain yield of succeeding wheat, which was mainly attributed due to increased organic carbon and total nitrogen status of soil. Sharma et al. (1988) showed that nutrient from organic sources did not prove beneficial to the rice, but their residual effect in increasing the grain yield of succeeding crop was clearly evident. FYM proved to be more beneficial in relation to its residual effect on wheat compared to the green manure.

Maskina et al. (1989) did not found any residual effect of green manure on succeeding wheat crop because most of the nitrogen mineralized from green manure during the rice crop season was used by rice itself. In wet land soil mineral nitrogen was almost readily lost through leaching and denitrification due to, which small amount of residual nitrogen was left after rice crop, which was beneficial to succeeding crop. There was no residual effect of gliricidia green manure and fertilizer application to rice on the succeeding groundnut crop, while fertilizer application to groundnut increased the pod yield significantly (Anon., 1989). On the other hand, application of 100% NPK combined with 10 t FYM ha-1 to rice produced the highest dry pod yield of groundnut (3419 kg ha-1) indicating notable residual effect of FYM (Anon., 1997). Balasubramanian and Palaniappan (1990) found no significant residual effect of green manure on succeeding green gram crop. There was marginal increase in grain yield of about 7% due to green manured plots. Panda et al. (1991) recorded substantial increase in organic carbon and total nitrogen in the soil after harvest of rice due to green manure, which benefited the succeeding rice crop. The nitrogen applied through chemical fertilizers alone did not show any residual effect.

Patil et al. (1991) reported that application of 10 t gliricidia alone and in combination with fertilizer to preceding rice increased the number of pods per plant, weight of dry pods per plant of succeeding groundnut. Application of 5 t ha-1 gliricidia with 12.5 kg N + 25 kg P2O5 ha-1 to preceding rice produced 16.92 q ha-1 dry pod yield of succeeding groundnut crop in lateritic soils of Konkan. Soni and Sikarwar (1991) observed the residual effect of applied FYM at varying fertilizer levels on succeeding wheat crop showing positive effect on yield of wheat. Similarly, Rajput and Warsi (1992) concluded that residual effect of FYM was more pronounced than wheat straw.

Rathore et al. (1995) reported that residual effect of FYM with inorganic fertilizers was significant on grain yield of succeeding wheat crop and NPK uptake, as well as the residual fertility builds up in terms of organic carbon and available phosphorus, but there was no impact on build up of available nitrogen and potassium in soil. Sharma et al. (1995) observed the beneficial residual effect of sesbania and mung straw applied to rice on succeeding wheat crop. There was increase in the wheat yield by 0.6 and 0.7 t ha-1, respectively as compared to the control. The sesbania green manure and mung straw substituted 43 and 30 kg N ha-1 in rice and subsequently showed beneficial effect on succeeding wheat equal to the extent of 89 and 112 kg N ha-1, respectively.

Ramamurthy and Shivashankar (1996) found that residual effect of organic manure and phosphorus applied to preceding soybean significantly improved the plant height, dry matter accumulation and yield contributing characters of maize like number of cobs per plant, shelling percentage during both the years of study. This might be due to enrichment of soil with nutrients. Samasundaran et al. (1996) observed a pronounced residual effect of green manure to preceding crop of rice followed by the succeeding rice crop at different fertilizer levels.

Dixit et al. (1997) conducted a field experiment with the objective to study the possibilities of economizing chemical fertilizers through organic manures in rice-sorghum sequence. The treatments applied in kharif containing manure to rice crop, generally, left a significant residual effect, especially when, part of nitrogen was applied as FYM. Kumbhar (1999) observed that green pod yield, as well as straw yield of dolichos bean was significantly affected due to residue of various organic manures applied to rice crop as compared to control. They further noted that the differences due to residual effects between FYM and gliricidia were of similar order.

Talathi (2001) showed that residual effect of 50% recommended NPK + 50% N through FYM was more pronounced resulting in increased dry matter accumulation, yield contributing characters and grain and kernel, as well as stover yield of succeeding maize and groundnut followed by 50% recommended NPK + 50% N through gliricidia as compared to control. Application of 50% recommended NPK + 50% N through gliricidia applied to rice and 75% recommended NPK to succeeding groundnut was found to be comparatively more beneficial for improving the fertility status of soil under rice-groundnut sequence closely followed by 50% recommended NPK + 50% N through FYM to kharif rice and 75% recommended NPK to succeeding rabi groundnut.

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VII. Integrated nutrient management in rice based crop sequence

Ramteke et al. (1982) investigated nitrogen management in cropping systems and reported that maize grown in sequence with legumes in general and berseem in particular recorded higher yields of maize compared to that of wheat as the preceding crop. Incorporation of legumes in cropping systems improved the fertility status of the soil and thereby reduced the fertilizer nitrogen requirement for the succeeding crop of maize. The yield of rabi crops did not increase appreciably due to the residual effect of graded doses of nitrogen applied to maize crop. Gopalswamy and Vidyashekharan (1987) revealed that green leaf manure and urea were effective in increasing the yield, but only green manure was responsible for improving the soil fertility. Hussain and Jilani (1989) observed that FYM in combination with 87 kg N ha-1 increased plant height, number of tillers m-2, grain and straw yield and nitrogen recovery in rice.

Malik and Jaiswal (1993) noted that grain yield obtained with 87 kg N ha-1 was equal to that obtained with 58 kg N ha-1 as urea and 29 kg N ha-1 as FYM. This showed that half to two third of chemical nitrogen can be substituted by organic nitrogen (FYM) without any yield loss depending upon the rate of nitrogen applied to rice. Deshmukh et al. (1994) observed that application of organic manure and fertilizer in different combinations significantly increased the grain yield over control (no fertilizer, no manure). The increase over 100% NPK due to FYM addition along with it was only 11.28% indicating that FYM addition at lower dose than 100% NPK may prove to be beneficial.

Gill et al. (1994) found that the yield obtained with 150% recommended dose of NPK was similar with green manuring + 100% recommended NPK and significantly more than all the other treatments. Matiwade and Sheelavanter (1994) reported the highest grain yield of 6585 kg ha-1 due to green manure with sesbania rostrata (10 t ha-1) + 100% recommended dose of fertilizer. Prasad (1994) in an experiment conducted at Pusa on integrated nutrient management observed that 10 t ha-1 FYM + 15 kg ha-1 BGA could substitute 25% NPK as chemical fertilizer in rice. Further, there was residual effect equivalent to 20% of NPK as chemical fertilizers on the yield of succeeding wheat and winter maize in rice-wheat and rice-maize cropping system. Integrated use of FYM 12 t ha-1 + 80 kg N ha-1 gave as much rice yield as 120 kg N ha-1 as fertilizer.

Rajkhowa and Baroova (1994) studied the effect of FYM in different combinations with urea such as 100:0, 75:25, 50:50, 25:75, 75:0 and 0:100. They observed maximum grain yield (2.2 t ha-1) with 100% N as urea followed by 100% N as FYM (2.10 t ha-1). Combined application of FYM with fertilizer (75:25) recorded yield (2.14 t ha-1) at par to that of 100% alone through fertilizer in case of transplanted rice. Peeran and Ramulu (1995) found that the application of green manure with urea produced taller plant of rice, higher number of tillers per hill as compared to combined application of FYM with urea and control indicating superiority of green manure over FYM.

Shinde (1995) in an experiment conducted on paddy Cv. Indrayani with two N levels 25 and 50 kg ha-1 and four gliricidia levels 2, 4, 6 and 8 t ha-1. The results revealed that application of 50 kg N ha-1 with 8 t ha-1 of gliricidia produced significantly higher grain yield (52 kg ha-1) and straw yield (58.6 kg ha-1) as compared to other treatments. It was noticed that every additional increase in gliricidia with 25 and 50 kg N ha-1 resulted significant increase in grain and straw yield. Incorporation of 8-10 t ha-1 of gliricidia save fertilizer N to the extent of 50-100% recommended dose of N without reduction in grain and straw yield. Working on integrated nutrient management in rice-rice crop sequence Jana and Ghosh (1996) observed that grain yield of rice was higher under 100% recommended dose of NPK fertilizers supplied through either inorganic source alone or 75% through inorganic and 25% through organic in the form of FYM in rice-rice crop sequence. Similar results of saving in 25% of chemical fertilizer (NPK) through FYM in rice-based crop sequence were observed by Hedge (1996).

Dixit et al. (1997) indicated that manure to kharif rice crop, generally, left a significant residual effect, especially when, part of nitrogen was applied as FYM in rice-sorghum crop sequence. It was possible to make marginal adjustments in fertilizer recommendation during rabi season thereby ensuring economy in fertilizer use. Devi et al. (1997) reported that application of 50% NPK through FYM during first season followed by 100% NPK through inorganic fertilizers during second season in rice-rice cropping sequence significantly increased grain yield in all the years of study. Use of organic source along with inorganic sources enhanced yield. Using an equal proportion of each source of nutrients would be optimum for producing higher and sustained yield over time.

An experiment carried out to study the integrated effect of organic manures and inorganic fertilizers on rice by Powar and Mehta (1997) indicated that application of gliricidia @ 10 t ha-1 and half the recommended dose of N + full recommended dose of phosphorus produced the highest grain yield followed by gliricidia application @ 10 t ha-1 + 25% of the recommended dose of N + full dose of phosphorus. Similar trend was observed in case of straw also. Chavan et al. (1990) and Macchi et al. (1991) also noted similar observations. Talashilkar and Chavan (1997) reported that incorporation of gliricidia leaves @ 10 t ha-1 just before transplanting of rice can produce as much rice yield as produced by the application of recommended dose of NPK.

Singh et al. (2001) conducted a field experiment on response of brown sarson to residual effect of organic manure, nitrogen and transplanting dates of rice during the rainy and winter seasons of 1995-96 and 1996-97 on silty clay loam soil. They found that seed yield, yield attributes, siliquae per plant, 1000 grain weight and nutrient uptake of brown sarson increased significantly as result of residual effect of application of organic manure and nitrogen on preceding rice crop.

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VIII. Effect of crop sequences on fertility dynamics of soil

It has been estimated that out of 100 M.T. of nitrogen fixed annually, the largest part comes from symbiotic sources particularly through the nodules of legume plant (Donald, 1960). The legumes included in a cropping system also help to ameliorate availability of phosphorus as observed by Chandrashekharan (1969). Intensive cropping with cereals without addition of organic manures leads to reduction in organic carbon and nitrogen (Chater and Gasser, 1970). Rao and Sharma (1978) reported that in Tarai soil of Pantnagar cereal-cereal (maize-wheat) system showed a deficit balance of 53 kg N ha-1 while build up of 81 kg ha-1 was recorded under maize-potato-green gram system at the end of two years. They further noted that cropping system particularly including legumes resulted in build up the nitrogen status of soil. The beneficial effect of legumes on soil nitrogen status was also reported by Subba (1979).

Purushothaman and Palaniappan (1978) noted that available nitrogen status was slightly reduced in rice-rice-rice system at the end of two years. This might be due to continuous cropping of rice without including any legume in the rotation either as a pure or intercrop. The percentage of maximum reduction in phosphorus was in rice-rice-maize + soybean system. This could be explained by the higher demand and removal of phosphorus by maize in rotation and by higher intensity of cropping resulting in increase in dry matter accumulation and phosphorus removal by system. Sonar and Zende (1984), Patil (1985) and Jadhav (1989) reported that inclusion of leguminous crops in sequence has improved the soil fertility status of soil after harvest. Nutrient removals by crops under different cropping sequences vary greatly, which in turn influence the fertility status of soils. Cereal crops have been reported to deplete the soil fertility to a relatively greater extent (Chakravarti, 1979). On the other hand, Nair (1977), Haines (1982) and Subbiah (1984) indicated that a restorative crop of legumes enriched it to some extent.

A comprehensive study of nutrients balance sheet made by Singh et al. (1988) at IARI, New Delhi proved that cereal-cereal sequence (Sorghum-wheat) exhausted the soil nutrients of nitrogen and phosphorus to the maximum and cluster bean-wheat to a minimum. They further showed the maximum contribution towards soil nitrogen was by cluster bean (75-76 kg ha-1) followed by black gram (63-68 kg ha-1) and groundnut (54-58 kg ha-1) whereas, Sorghum on an average removed 25.5 kg N ha-1 from the soil, which ultimately resulted in depletion of soil fertility.

George and Prasad (1989) reported that inclusion of fodder maize in rice-wheat system on alluvial soil of Bhopal accelerated the potassium removal compared to the system involving cowpea as a pulse crop. Kurlekar et al. (1993) noted that all the sequences tried exerted beneficial effect in maintaining the available NPK status of soil as compared to initial soil fertility. The sequence of cereal-cereal-green manure (sorghum-wheat-sunnhemp) with 100% recommended dose of fertilizer was found to be comparatively more beneficial for improving the soil fertility status. This was mainly attributed to the quantity and quality of biomass of sunnhemp incorporated into the soil, which might have added sufficient mineralizable nitrogen into the soil.

Thakur and Ramteke (1993) revealed that rice fertilized with Urea Super Granules recorded significantly higher grain yield (72.09 q ha-1) than other sources. Similarly, Nimin Coated Urea proved significantly superior (60.68 q ha-1) than Nimin Coated Urea and Neem Extract Coated Urea. An identical trend was also noted in case of paddy straw yield. The results further indicated that application of urea super granules to the preceding rice crop resulted in 18.7, 29.3, 31.0, 26.1 and 35.3 per cent higher grain yield of succeeding wheat crop than nimin coated urea, coal tar treated urea, Nimin Coated Urea, prilled urea and Neem Extract Coated Urea. Newaj and Yadav (1994) reported that the values of bulk density were lower under all the system at the end of study as compared with initial value. This reduction in bulk density was due to the systems inclusion of at least one pulse crop that increased the organic matter in the soil by adding crop residues and presence of crop throughout the year. There was increase in the organic carbon, available NPK content of soil compared to their initial level.

Working on the influence of various organic manures and graded levels of NPK fertilizers over two years cropping cycle, Chinnusamy et al. (1997) revealed that the application of organic manures to rice and graded levels of NPK fertilizers to each crop in rice-soybean-sunflower and rice-gingili-maize systems exerted considerable influence on the soil fertility status. Considerable increase in the post harvest available nutrients (NPK) status in soil after two years could be attributed to the build up of the fertility with application of enriched organic manures by addition of crop residues and organic matter to soil. Inclusion of leguminous crop like soybean in rice-soybean-sunflower system increased the net gain of nitrogen through the addition of residue and fixation of nitrogen compared to rice-gingili-maize system. They further noted that considerable quantity of nutrients could be returned to soil if the residues are incorporated in rice based cropping systems, which are gradually available to subsequent crops on decomposition.

Setty and Gowda (1997) indicated significant increase in soil fertility status due to incorporation of green manure or legumes under rice-based cropping system in coastal Karnataka. They further observed that organic carbon status remained in the same range in rice-rice-fallow system, while significant increase was observed in rice-groundnut-cowpea system. Similarly, significant increase in available potassium content was observed in rice-groundnut-cowpea system compared to rice-rice-fallow system.

Kanwar and Sekhon (1998) concluded that rice-wheat cropping system resulted in a depletion of organic matter content that is arrested only by regular incorporation of crop residues or FYM. On the contrary, Prasad (1999) noted that inclusion of dhaincha after wheat in rice-wheat cropping system increase the organic matter content, available plant nutrients and improvement in physical, chemical and biological properties of soil. According to Sakal et al. (1999) cropping systems significantly influenced the available nutrient status of soil. The maximum phosphorus and sulphur depletion was noted in rice-wheat (cereal-cereal) system whereas there was minimum depletion in rice-linseed system. In short, inclusion of oilseed in rice based system reduced the deficiency of micro-nutrients to a certain extent.

Singh et al. (2001) reported that in rice-mustard cropping sequence, there was a positive net gain of nitrogen at higher doses of nitrogen (N100 and N150) in combination with organic manure. Lower doses of nitrogen (N0 and N50) alone or in combination with manure resulted in negative nitrogen gain of available soil nitrogen. Prasad (1994) also reported similar results. Talathi et al. (2002) recorded that fertility dynamics of soil showed a deficient balance of 89.04 kg N, 10.11 kg P2O5, 82.51 kg K2O ha-1 in control under rice-maize crop sequence, but the extent of deficit was less in rice-groundnut crop sequence (58.60 kg N, 7.72 kg P2O5, 79.10 kg K2O ha-1).

Singh et al. (2002) reported that in rice-mustard cropping sequence, single super phosphate @ 250 kg ha-1 significantly augmented grain as well as straw yield of rice, whereas in mustard 333 kg SSP ha-1 significantly improved the values of yield trait and yield. SSP application @ 333 kg ha-1 in rice caused the highest sulphur uptake by rice, whereas the highest sulphur uptake in mustard was associated with 333 kg SSP ha-1.

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IX. Effect of crop sequences on economics

Ramteke et al. (1982) reported that economic analysis of cropping systems as a whole brought out the higher monetary returns from the crop sequences involving rabi legumes. Total net profit was the highest in berseem-maize system (Rs. 11280 ha-1) followed by pea-maize (Rs. 7815 ha-1) and lentil-maize (Rs. 6340 ha-1). Ramteke et al. (1986) revealed that growing legumes before maize was more remunerative than following wheat-maize cropping system, except gram-maize system. The total net profit was the highest in berseem-maize system (Rs. 11281 ha-1). Pea-maize (Rs. 7815 ha-1) and lentil-maize systems (Rs. 634 ha-1) were certainly more remunerative than wheat-maize system (Rs. 5883 ha-1). The net profit per rupee invested was maximum in berseem-maize system (1.68) followed by pea-maize (1.48) and lentil-maize (1.32) sequence. The maximum profit per rupee invested was obtained in berseem-maize crop sequence (1.68) followed by pea-maize (1.48) and lentil-maize system (1.32).

Gangwar and Katyal (2001) conducted field experiment at Kalyani and Bhubaneshwar during 1992-97. They reported that stability of the system was highest (0.74) in rice-Indian mustard [Brassica juncea (L.) Czernj. & Cosson]-ridge gourd [Luffa acutangula (Roxb.) L.] sequence. On the other hand, in terms of minimum risk of financial involvement, rice-Indian mustard-rice at Kalyani and rice-Indian mustard-ridge gourd at Bhubaneshwar were advisable.

Talathi et al. (2002) showed that amongst the two crop sequences tried, rice-groundnut was more remunerative than rice-maize sequence. In case of rice-groundnut sequence maximum net returns (Rs. 29101.76 ha-1) and benefit cost ratio (1.58) were observed due to application of 100% RDF to both the crops. It was closely followed by application of 50% RDF + 50% N either through gliricidia or FYM to rice and 75% RDF to groundnut. The maximum net returns (Rs. 22385.32 ha-1) and benefit cost ratio (1.49) were observed due to 100% RDF to both the crops in rice-maize sequence followed by application of 75% RDF + 25% N either through gliricidia or FYM to rice and 100% RDF to maize, 50% RDF + 50% N either through gliricidia or FYM to rice with 75% RDF to succeeding maize.

Singh et al. (2002) reported that in rice-mustard cropping sequence highest B:C ratio in rice was associated with 333 kg single super phosphate ha-1 to rice, which was closely followed by 250 and 125 kg SSP ha-1 with least B:C ratio from control treatment. When, SSP was applied to mustard the residual effect on B:C ratio was best associated with 333 kg SSP ha-1 followed by 166 kg SSP ha-1 and control. Increased B:C ratio in mustard was found with increasing SSP levels in rice the values being highest in control. SSP application to mustard also increased B:C ratio in mustard up to 333 kg SSP ha-1. Based on B:C ratio, rice and mustard in isolation and in sequence should be fertilized with 250 kg and 333 kg SSP ha-1, respectively.

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