Field Modeling Study of Yield Response and Nitrate Leaching with Manure Application and Deficit Irrigation for Maize-Fallow-Wheat Rotation

Efficient nutrient and water management is crucial for enhancing crop productivity, soil health, and mitigating environmental losses in cereal cropping systems of semi-arid regions. A two-year field experiment was conducted to evaluate the effects of dairy manure annual application of 50 Mg ha-1 to maintain recommended fertilizer N, compared to sole urea application with two different irrigation regimes (100% and 75% ETc) on crop yield, water use efficiency, deep percolation, nitrate leaching, and soil quality within a wheat-fallow-maize rotation in Pakistan. Suction lysimeters installed at a depth of 1.2 m were used to collect nitrate-N leachates, while HYDRUS-1D was used to assess daily deep percolation losses. Results indicate that the interaction between manure and irrigation was significant for yield, nitrate-N leaching, and soil health. Manure with deficit irrigation showed wheat and maize yield of 4.36 and 7.80 Mg/ha, irrigation water use efficiency (WUEi) of 1.09 and 1.59 kg/ha/mm, respectively, with no significant increase observed with full irrigation; while a significant decrease was observed in the absence of manure, either with full irrigation or deficit irrigation. Manure with deficit irrigation averaged annual nitrate-N leaching of 17.45 kg/ha, while urea and manure with full irrigation averaged 11.46 and 55.59% increases in nitrate-N leaching losses, respectively, without any yield benefits. Our results indicate that deficit irrigation with manure produces optimum yield with reduced nitrate-N leaching risk and improved soil physical properties.