NITROGEN DINAMICS IN RICE AT DIFFERENT STAGES OF CROP GROWTH UNDER RICE-WHEAT CROPPING SYSTEM

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1 NITROGEN DINAMICS IN RICE AT DIFFERENT STAGES OF CROP GROWTH UNDER RICE-WHEAT CROPPING SYSTEM Hrusikesh Patro*, S.C. Swain, S.C. Mohapatra 1, Lingaraj Patro 2, B.S. Mohapatra and Ajay Kumar 3 1. Krishi Vigyan Kendra, Gajapati, R. Udiyagiri Orissa, (INDIA) 2. Environmental Toxicology Lab, Department of Zoology and Biotechnology, K.B.D.A.V College, Nirakarpur , Orissa, (INDIA) 3. Govind Ballav Pant University of Agriculture and Technology, Pantnagar, (INDIA) Received September 14, 2007 Accepted July 4, 2008 ABSTRACT A field experiment was conducted at Govind Ballav Pant University of Agriculture and Technology, Pantnagar (India) during and to evaluate the effect of four organic sources viz. Sesbania aculeata, Crotalaria juncea Vigna unguiculata and wheat straw along with 4 levels of N to rice (Oryza sativa L) and 3 levels of N to wheat (Triticum aestivum L), on wet soil ammoniacal N, soil available N and grain yield in rice at different stages of crop growth under rice wheat cropping system. Wet soil ammoniacal N, soil available N content declined with time and reached minimum at during both the years. Sesbania green manure to rice recorded significantly higher soil ammoniacal N, soil available N and grain yield then any other organic sources applied to rice at all the stages of growth in both the years. Wet soil ammoniacal N, soil available N and grain yield increased significantly with increase in the level of nitrogen applied to rice even up to 180kg N ha -1 at all the stages of growth during both the years. Interactions between organic source and nitrogen level applied to rice were found significant at and and at during both the years as regards to all the three parameters under study. Key Words : Sesbania aculeata, Crotalaria juncea, Vigna unguiculata, Oryza sativa, Nitrogen, Grain yield. INTRODUCTION Rice wheat cropping system is the predominant cropping system in India which * Author for correspondence is ensuring food security presently. Integrated use of green manures and chemical fertilizers in rice-wheat cropping 82 system can save 50 and 25 percent of fertilizer - N in rice and wheat, respectively 1 As regards to N dynamics there are reports that significant changes in organic N fractions (95-98% of total soil N) occur in soil during flooding of (rice crop) and drainage (wheat crop) cycles of rice wheat system. The magnitude of ammonium

2 formation during rice growth stages under submerged conditions is mainly dependent on the sources and rate of applied N and organic matter content of the soil. Singh and Bajwa 1,2 observed that application of N either in the form of fertilizer N or organic N in rice increased the soil ammoniacal N and available N over control 6. They also observed that a decreasing trend up to for ammoniacal N and from 15 to for available N. Therefore proper understanding of N dynamics of native as well as applied N in rice-wheat system is essential for better scheduling of fertilizer N and sustainability in the productivity of these soils. The present investigation was undertaken to study the contribution of Sesbania, Crotalaria and Vigna green manure, wheat straw incorporation in rice and fertilizer N application to both rice and wheat towards wet soil ammoniacal N and soil available N content at different stages of rice crop growth. MATERIAL AND METHODS The experiment was carried out at Crop research Centre of Govind Ballav Pant University of Agriculture and Technology, Patnagar, during and The soil of the experimental fields was silty clay loam with p H 7.3 and 7.2, organic carbon and percent, available N 227 and 205 kg /ha, available P 20.5 and 18.5 kg /ha and available K 149 and 124 kg /ha in 0-20cm and 20-40cm depth respectively. Four organic sources of nutrients viz green manuring with Sesbania aculeata, Crotalaria juncea, Vigna unguiculata and wheat straw incorporation beside summer fallow with 4 levels of N viz., 0, 120 and 180 kg / ha were applied to rice; wheat was grown after rice and received 3 levels of N viz. 0,75 and 150 kg /ha. The trial was laid out in a split split plot design keeping organic sources in main plot, N levels to rice in sub plots and N levels to 83 wheat in sub-sub plots with 3 replications. The layout remains unchanged in the 2 nd year. Green manure crops were sown in beginning of May and were incorporated at 8 weeks stage. Chopped wheat straw 10.0 t/ha was incorporated during puddling. The plot size was 15m x 11m for main plot, 7m x 5m for sub-plot and 5mx 2m for sub-sub plots. N was applied in 3 splits to rice 50% at planting, 25% at tillering and 25% at panicle initiation and in 2 splits to wheat 50% at sowing and 50% after first irrigation. P 2 O kg /ha to both the crops and K 2 40kg /ha to rice only as basal dose was applied. Twenty five days old rice seedlings of variety Pant Dhan 4 were transplanted at a spacing of 20cm x 15cm on 2 July and 29 June during 2000 and 2001, respectively UP-2338 wheat was sown on 24 and 17 November in and , respectively at 23cm row spacing using 100kg seeds/ha. After initiation of the present study, soil samples from every plot were collected at 30, and and at of rice during both the years. Soil samples collected during rice growth stages were analyzed for ammoniacal N and Soil available N. Wet soil ammoniacal N was determined by Indophenol blue colour method. Available N was determined by alkaline KMnO 4 method 3, 4. RESULTS AND DISCUSSION Effect of Sources Wet soil ammoniacal N on dry weight basis gradual1y declined with time and reached minimum at rice during both the years (Table 1). Rate of decrease was rapid up to followed by a slower decrease at in while rate of decrease was slow at and gradually decreased up to in Variation in organic sources applied to

3 rice brought significant differences in soil ammoniacal N content at all the stages of rice growth. (Table 1) Sesbania green manure to rice recorded significantly higher soil ammoniacal N than any other organic sources applied to rice at all the stages of growth in both the years except in , in which it was at par with Crotalaria green manure to rice at 30. However, the differences in ammoniacal N in soil due to incorporation of wheat straw and Vigna as well as Vigna and Crotalaria at all the stages of growth during both the years were found non significant except at 30 in in which it was significant between Vigna and Crotalaria green mature. Table 1 : Wet soil ammoniacal N (kg ha -1 ) at various stages of rice as influenced by integrated nitrogen management Treatments Days after transplanting Sources Fallow Wheat straw Vigna Crotalaria Sesbania SE m CD(0.05) N level (kg ha -1 ) SE m CD (0.05) Soil available nitrogen content declined with time and reached minimum at during both the years (Table 2). Rate of decrease was rapid up to followed by slower decrease up to in both the years. Sesbania green manure to rice recorded significantly higher soil available nitrogen than any other organic sources 84 applied to rice at all the stages of growth except at 30 in which it was at par with Crotalaria in both the years. Differences in grain yield were significant due to organic source as well as nitrogen level applied to rice during both the years Table 3 rice grain yield was maximum

4 with Sesbania green manure and minimum with fallow during both the years (Table 3). In , rice grain yield obtained with Vigna being at par with wheat straw incorporation treatment, was significantly superior to fallow. Percent increase in grain yield due to Sesbania as compared to Crotalaria, Vigna, wheat straw incorporation and fallow was 14.1, 42.8, 58.5 and 116.3, respectively. In , rice yield with Sesbania green manure was significantly higher over the remaining sources. Percent increase in rice grain yield due to Sesbania green manure over Crotalaria, Vigna, wheat straw incorporation and fallow were 10.6, 24.0, 40.3 and 92.6, respectively. Different yield performance of rice grown with various organic sources and fallow can also be explained through the variation in available forms of N and ammoniacal N in the soil during crop growth stages. Sesbania green manuring increased the soil inorganic and available forms of N which in turn increased the yield of the rice crop 2. Similar results were also reported earlier by Bindra and Thakur 5-7. Table 2 : Soil available (mineralizable) nitrogen content (kg ha -1 ) at various stages of rice as influenced by integrated nitrogen management Treatments Sources Days after transplanting Fallow Wheat straw Vigna Crotalaria Sesbania SE m CD(0.05) N level (kg ha -1 ) SE m CD (0.05) Effect of N Levels Applied to Rice Wet soil ammoniacal N increased significantly with increase in level of nitrogen applied to rice even up to 180 kg N

5 all the stages of growth, however the difference between 0 and kg N ha -1 was not significant at 30 during improvement in rice grain yield up to 180 kg ha -1 during both the years. Percent increase in grain yield due to,120 and 180 kg N ha -1 Soil available nitrogen increased over control was 20.8, 46.9 and 54.2 during significantly with increase in level of nitrogen applied to rice even up to 180 kg N ha -1 at all the stages of growth during both the years (Table 2). Increasing each successive level of nitrogen applied to rice brought significant and 7.9, 32.0 and 39.5 during , respectively. Response to per kg of nitrogen applied at, 120 and 180 kg N ha -1 levels was 11.4, 12.9 and 9.9 kg grain during ; and and 9.15 kg grain during , respectively. Table 3 : Effect of integrated nitrogen management on grain yield of rice. ha -1 Sources Treatments Grain yield (kg ha -1 ) Fallow Wheat straw Vigna Crotalaria Sesbania SE m CD(0.05) N level (kg ha -1 ) SE m CD (0.05) Increase in rice yield with increasing N level were also conformed by significant positive correlation with soil ammoniacal N and available N at all stages during both the years. Similar beneficial effects of fertilizer N application on grain yield of rice due to increased soil ammoniacal N and available N were also reported 7 by Suresh et al. 8. Effect of interaction between organic source and nitrogen level applied to rice Effect of interaction between organic source and nitrogen level applied to rice Interaction between organic source and nitrogen level applied to rice were found significant at and and at during both the years as regards to wet soil 2

6 ammoniacal N and soil available N (Table 4, Table 5 and Table 6). Table 4 : Interaction effect of treatment on wet soil NH 4 +- H (Kg ha -1 ) at different stages of rice, Source Table 5 : Interaction effect of treatment on wet soil NH 4 +- H (Kg ha -1 ) at different stages of rice, Source Nitrogen level (Kg ha -1 ) Fallow Wheat straw Vigna Crotalaria Sesbania For two nitrogen levels at same level of organic source For two organic sources at same or different level of nitrogen Nitrogen level (Kg ha -1 ) Fallow Wheat straw Vigna Crotalaria Sesbania For two nitrogen levels at same level of organic source 87 For two organic sources at same or different level of nitrogen SE m CD (0.05) SEm CD (0.05) Table 6 : Interaction effect of treatments on soil available nitrogen content (kg ha -1 ) at various stages of rice growth

7 Nitrogen level (Kg ha -1 ), Treatments Fallow Wheat straw Vigna Crotalaria Sesbania Fallow Wheat straw Vigna Crotalaria Sesbania For two nitrogen levels at same level of organic source For two organic sources at same or different level of nitrogen SEm CD (0.05) Table 7 : Grain yield of rice (kg ha -1 ) as affected by organic source x nitrogen level interaction Sources Nitrogen level (Kg ha -1 ) Fallow Wheat straw Vigna Crotalaria Sesbania For two nitrogen levels at same level of organic source For two organic sources at same or different levels of nitrogen SEm CD (0.05) The data given in Table 4 and Table 5 nitrogen applied to rice up to 120kg N ha -1 revealed that soil ammoniacal N content being at par with 180 kg N ha -1 with different increased by increasing each level of organic sources except fallow at and 88

8 and at during both the years. In case of fallow treatment 120 kg N ha -1 was at par with 180 and kg N ha -1 but significantly superior to no nitrogen application at all the stages of rice growth studied during both the years. Plots incorporated with wheat straw and Vigna and Vigna and Crotalaria green manure at any nitrogen level showed no significant difference between them for wet soil ammoniacal N content at and and at during both the years. However, the maximum and significant soil ammoniacal N was obtained with Sesbania green manured rice along with 180 kg N ha -1 over crotalaria green manure at 180 kg N ha -1 and other combinations except Sesbania green manure along with 120 kg N ha -1 at and and at during both the years. The data given in Table 6 indicated that soil available nitrogen content increased significantly by increasing each level of nitrogen applied to rice even up to 180 kg N ha -1 being at par with 120kg N ha -1 at all the growth stages under any other organic source applied to rice except fallow during both the years. The differences between 0 and kg N ha -1 were not significant under fallow, wheat straw and Vigna green manure treatment at all the stages in both the years of experimentation. However, application of 180 kg N ha -1 along with Sesbania green manure applied to rice recorded the highest soil available nitrogen content as compared to any other treatment combination at all the stages of growth during both the years. Interaction between organic source and nitrogen level applied to rice was significant during both the years for rice grain yield (Table 7). Rice grain yield increased significantly only up to 120 kg N ha -1 being at par with 180kg N ha -1 with all the organic 89 sources in both the years. The differences in grain yield between 0 and kg N ha -l with wheat straw incorporation and between 0 and as well as and 120 Kg N ha -1 with fallow treatment were not significant. However, rice with Sesbania green manure and 180 kg N ha -l recorded the highest grain yield which was at par with Sesbania green manure with 120 kg N ha -l ; but significantly superior to any other treatment combination during both the years. Moreover, the difference in grain yield between Vigna and wheat straw at any level of nitrogen was not significant. Similarly at 0 as well as kg N ha -l, the grain yield recorded between Sesbania and Crotalana green manure were also found non-significant in both the years. The lowest grain yield was obtained under fallow with no nitrogen application. Application of nitrogen either in the form of fertilizer N or in the form of organic N increased ammoniacal N and available N in soil over no Nitrogen application 6. N compounds upon decomposition get splitted into simpler forms which resulted into release of ammoniacal N. A portion of it is adsorbed to cation exchange sites of the soil and remaining unabsorbed ammoniacal N is readily available to plant and there after a steady out flow from exchange complex indicates continuous supply of N to rice 7, 8. CONCLUSION Sesbania green manure incorporation to rice maintained wet soil ammoniacal N and available N at significantly, higher level throughout the rice the growth. Nitrogen either in the form of fertilizer N or in form of organic N increased ammoniacal and available nitrogen in soil but showed a decreasing trend as crop growth proceeds towards maturity in both the years. Thus, the study showed the beneficial and favourable effects of in situ Sesbania

9 green manuring at 8 weeks after sowing on following rice crop. Grain yield of rice recorded under Sesbania aculeata incorporation plots along with kg N ha -1 were significantly superior to application of 180 kg Nha -1 under Vigna, wheat straw incorporation and fallow, indicating a saving of more than 120kg N ha -1. REFERENCES 1. Aulakh M.S. ; Khera T.S.; Doran J.W.; Singh K. and Singh B., Yields and nitrogen dynamics in rice wheat system using green manure and in organic fertilizer, Soil Science society of American Journal, 64, , (2000) 2. Bindra A.D. and Thakar R.C., Influence of green manures along with fertilizers on Nitrogen, Phosphorus and Potassium contents in rice, Oryza 33, , (1996) 3. Keeney D.R. and Nelson D.W., Nitrogen in organic forms. In : Methods of soil analysis Part-II (Eds. Page, A.L.; miller, R.H. an d Keeney, D.R.), American society of Agronomy Inc. Soil Science Society of America Inc. Madison, Wisconsin, USA , (1982) 4. Mahapatra B. S. and Sharma G.L, Contribution of Sesbania species to yield and nitrogen nutrition in lowland rice, Indian Journal of Agronomy, 41, , (1996) 5. Nagarajah S., Transformation of green manure nitrogen in lowland rice soils. In : Proceedings of symposium on sustainable Agriculture The role of green manure crops in rice farming systems held from May, 1987 at IRRI, Phillipines , (1998) 6. Singh B and Bajwa M. S., Effect of gypsum, green manure and urea on ammonia volatilization from sodic soil grown with rice. Oryza, 26(4), , (1998) 7. Suresh S., Ramaswami P.P. and Kennedy R.R., Effect of Nitrogen sources on the avail ability of inorganic nitrogen forms in sandy clay wet land rice soil Madras Agricultural Journal, 82 (6,7,8), , (1995) 8. Wada G., Shoji S. and Mac T. Relationship between nitrogen absorption and growth and yield of rice plants. Journal of Agricultural Research Quarterly 20 (2), , (1986). Grow tree, Feel the Environment free