Saturday, 15 July 2006

Long-Term Effects of Inorganic and Organic Inputs on Yield and Soil Fertility in the Rice-Wheat Cropping System in India.

D.S. Mehla1, J.P. Singh1, K.S. Sekhon2, D. Sihag3, and K.K. Bhardwaj1. (1) Dept of Soil Science, CCS Haryana Agricultural Univ, Hisar 125 004, India, (2) PAU Regional Research Station, Bhatinda, Panjab Agricultural Univ, Ludhiana, India, (3) Dept of Agriculture, Haryana, CCS Haryana Agricultural Univ, Hisar 125 004, India

In India, the rice-wheat is a dominant cropping system across the Indo-Gangetic Plains and in the Himalayan Foothills. Long-term manurial experiments are considered as valuable tools for providing information related to the issues of sustainability and resource management. In view of this, a field experiment on long-term basis was established in June, 1997 with two crops grown per year, rice (June October) and wheat (November April) at the CCS H.A.U., Regional Rice Research Station, Kaul, Haryana, India. Treatments for rice consisted of various combinations of N, P, K and Zn fertilizers levels with and with out organic materials. The organic materials applied to rice included farmyard manure (FYM), press mud (by product of sulphinated sugar factory), green manure (Sesbania aculeata) and burnt rice husk. For wheat, the treatments included various combinations of N, P and K fertilizers only. The soil of the experimental field was clay loam, mixed hyperthermic Typic Ustochrept. All the fertilized treatments significantly increased the rice yield relative to control in all the years. Grain yield and nutrient uptake (N, P and K) of rice increased significantly with the combined use of organic materials and inorganic fertilizers when compared with inorganic fertilizer application only treatment in all the years. Inorganic fertilizers along with 15 Mg FYM ha-1 produced significantly higher grain yield and nutrient uptake of rice than incorporation of green manure or addition of burnt rice husk and press mud along with inorganic fertilizers. Application of NPK lower than the optimal dose resulted in lower rice yield compared to that obtained with their balanced application. Application of N75P37.5K37.5Zn25 in green-manured plot produced rice grain yield almost equal to that obtained with N150P75K75Zn25 during all the crop growing periods. Thus green manuring with Sesbania aculeata before rice transplanting almost saved 50% of NPK fertilizers. The total annual productivity (rice + wheat yield) during eighth cycle was highest in FYM amended treatment followed by press mud, burnt rice husk and green manure amended treatments. The continuous cropping of rice and wheat for eight years with out addition of any inorganic fertilizer or manure (control) decreased the yield of rice but not significantly by 0.03 Mg ha-1 yr-1 and that of wheat significantly by 0. 04 Mg ha-1 yr-1. Application of sub-optimal levels of NPK fertilizers significantly decreased the yield of both rice and wheat crops with time. However, the magnitude of decrease was more in wheat as compared to rice. It ranged from 0.10 to 0.12 Mg ha-1 yr-1 for rice and from 0.11 to 0.15 Mg ha-1 yr-1 for wheat. Complete dose of NPKZn fertilizers with and with out organic amendments increased or maintained the sustainability of the rice-wheat cropping system. The residual effect of the organic materials applied to rice on the succeeding wheat crop during all the years was positive and the increase in wheat grain yield ranged from 4 to 8%. Continuous rice-wheat cropping for eight years without any fertilizer or organic material addition significantly decreased the organic carbon content of surface soil from its initial status. There was significant build up in soil organic carbon content in press mud and FYM amended treatments over green manured, burnt rice husk and inorganic fertilizers only treatments. Green manuring, burnt rice husk and inorganic fertilizers only treatments resulted in significant increase in organic carbon content of surface soil over control. Maximum build-up of soil carbon was observed in press mud followed by FYM, green manure and burnt rice husk amended treatments. Balanced application of NPKZn with and with out organic amendments increased the available N, P and K status of soil over their initial status.

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