INTERNATIONAL JOURNAL OF BIO-RESOURCE, ENVIRONMENT AND AGRICULTURAL SCIENCES (IJBEAS) Vol. 2(4) :430-435, 2016 www.sbear.in // ISSN 2454-3551 LONG-TERM EFFECT OF CROP RESIDUES AND ZINC FERTILIZER ON CROP YIELDS, NUTRIENT UPTAKE AND FERTILITY BUILDUP UNDER RICE-WHEAT CROPPING SYSTEM IN CALCIORTHENTS Vipin Kumar and Bishnuprasad Dash Department of Soil Science, Dr. Rajendra Prasad Central Agricultural University, Pusa, Samastipur, Bihar Received: September 2016 Revised accepted: October 2016 ABSTRACT The effect of crop residues and Zinc fertilizer on grain yield and nutrient uptake by rice and wheat was studied after 18 years of crop cycles in a calciorthent. Long term application of crop residues along with zinc increased grain yield (3.63 to 4.73 t ha -1 rice and 3.12 to 4.13 t ha -1 wheat) and nutrient uptake by rice (205 to 462 g ha -1 Zn, 46to 93 g ha -1 Cu, 635 to 1031 g ha -1 Fe and 478 to 773 g ha -1 Mn) and wheat (182 to 391 g ha -1 Zn, 444 to 88 g ha -1 Cu, 521 to 936 g ha -1 Fe and 431 to 718 g ha -1 Mn). The highest grain yield in both the crops was recorded in the treatment receiving 10 kg Zn ha -1 along with 100% incorporation of the straw produced by both the crops. The treatment consisting of 5 kg Zn ha -1 + 100% of crop residues was the next promising treatment in enhancing the crop yields. Keywords: Crop residues, rice, wheat, soil fertility, calciorthents, zinc fertilizer. INTRODUCTION The wide scale adoption of rice-wheat system has ushered in an increase in agricultural production, but this intensive system over a period of time and nature of the crops has set declining yield trends as well as deterioration in soil productivity even with optimum use of fertilizers. Hence, for restoration of soil productivity, there is an urgent need to look forward to other options of supplying plant nutrient like crop residues incorporation. The adverse effect of incorporation of rice and wheat straw can be counteracted by integrating organic amendments with crop residues (Yadvinder-Singh et al., 2004). The continuous recycling of crop residue restores the organic matter content and also increases microbial population in the soil (Prasad, 2005). The present investigation was therefore undertaken to assess the long-term effect of crop residue incorporation along with zinc on crop yields and soil fertility build up in calciorthents under rice-wheat cropping system. MATERIALS AND METHODS A field experiment was conducted during 1993-94 in light textured highly calcareous soil deficient in available zinc (0.56 mg kg -1 ) at Research Farm, Dr.R.P.C.A.U., Pusa, Bihar. The experimental soil (0-15 cm) had pH (1:2) 8.5, EC 0.36 dSm -1 , organic carbon 0.62 g kg -1 , available N 236.1 kg ha -1 , available P 19.7 kg ha -1 , available K 100.0 kg ha -1 , available Zn 0.56 mg kg -1 , available Fe 15.82 mg kg -1 , available Mn 3.30 mg kg -1 and available Cu 2.28 mg kg -1 . Four levels of crop residues viz. no crop residue (CR 0 ), 25% of straw produced (CR 25 ), 50% of straw produced (CR 50 ) and 100% of straw produced (CR 100 ) were applied as treatment in main plots. The treatments were given to each crop in every year. The main plot was divided into 4 sub-plots in which treatments viz. no Zn (Zn 0 ), 2.5 kg Zn ha -1 (Zn 2.5 ), 5.0 kg Zn ha -1 (Zn 5.0 ) and 10 kg Zn ha -1 (Zn 10.0 ) were superimposed over crop residues levels. The experiment was laid out in a split plot design with three replications and plot size was 5.0 x 2.0 m. Rice and wheat crops were