NUTRIENT BALANCES AS AFFECTED BY INTEGRATED NUTRIENT AND CROP RESIDUE MANAGEMENT IN COTTON-WHEAT SYSTEM IN ARIDISOLS. I. NITROGEN

A five-year cotton–wheat rotation field experiment was conducted on two alkaline-calcareous soils, i.e., Awagat (coarse loamy) and Shahpur (fine silty), to investigate the impact of integrated nutrient and crop residue management on soil and crop productivity. Apparent nitrogen (N) balances were developed. Minimum five-year mean yield (Mg ha^?1), obtained with Farmers’ Fertilizer Use (FFU) treatment was: cotton – Awagat, 2.19; Shahpur, 2.45; wheat – Awagat, 3.03; Shahpur, 3.94. With Balance Nutrient Management (BNM), yields increased (P ≤ 0.05) for cotton, 24% in Awagat and 18% in Shahpur soil; and wheat, 37% in Awagat and 24% in Shahpur soil. Maximum crop yields were obtained with Integrated Nutrient Management (INM), i.e., 3–5% higher than with BNM. Crop residue recycling increased the yields further, cotton by 2?7% and wheat by 2–10%. All nutrient management treatments, except for FFU without crop residue recycling, resulted in positive apparent N balances. INM improved SOM and NO₃-N, contents.     

INFLUENCE OF NITROGEN AND SULFUR ON YIELD AND SEED QUALITY OF THREE CANOLA CULTIVARS

In order to investigate the effect of nitrogen (N) and sulfur (S) fertilizers on yield and seed quality of three canola cultivars, a factorial based on randomized complete block experiment was conducted during 2005–2006 in Iran. Treatments included four nitrogen rates (0, 75, 150, and 225 kg N ha^?1 source of urea), four sulfur rates (0, 100, 200, and 300 kg S ha^?1), and three cultivars (‘Pf’, ‘Option-500’, and ‘Hyola-401’). Results indicated cultivar had a significant effect on all studied traits. ‘Option-500’ and ‘Hyola-401’ cultivars had the highest seed yield, protein content, and N:S ratio in seed. The levels of 150 and 220 kg N ha^?1 resulted in the maximum protein content. Increasing N levels resulted in N content and decreased the oil content. The interaction effect between S and N levels showed the highest N content in seed was obtained with 300 kg S ha^?1 and 225 kg N ha^?1.