Global Warming Potential in an Intensive Vegetable Cropping System as Affected by Crop Rotation and Nitrogen Rate

Greenhouse gas emissions from vegetable production systems contribute to climate change, but the impact of nitrogen (N) rates and crop rotation on global warming potential (GWP) is not well documented. A field experiment was conducted to estimate the sum of GWP (mGWP) and yield-scaled GWP in an intensive vegetable cropping system. The study included the traditional rotation of celery-tomato-lettuce (Rt) and the modified rotation of bur clover-tomato-lettuce (Rm), and each with four fertilizer N options (control, manure-N, optimum, and conventional N). The nitrous oxide emission rates were 6.87 and 10.24 kg N ha(-1), and the mGWP values were 27.9 and 31.8 MgCO2-eq ha(-1) per year from the optimum and conventional N plots under the traditional rotation, respectively. The change from the traditional to modified rotation reduced N input by 25%, N2O emissions by 24%, and mGWP by 14% but increased the net economic benefit by 33% under the optimized N application rate in the intensive vegetable cropping system. The trends of yield-scaled GWP from different N rates and vegetable crop rotations were similar to the mGWP. This study proved that optimizing vegetable crop rotation by including legumes and adjusting N application rates simultaneously can reduce global warming potential while maintaining agricultural economic benefit.