Straw management, crop rotation and nitrogen source effect on carbon and nitrogen dynamics: A laboratory study

Straw incorporation, crop rotation and organic fertilizer applications have been proposed to counter the negative effects of straw burning, inorganic N fertilizer application and intensive agriculture practices for wheat production in the state of Sonora (M,xico). A laboratory study was done to investigate how these alternative agriculture practices applied for 9 years affected carbon dioxide (CO2), nitrous oxide (N2O) and nitrogen (N-2) emissions and inorganic N in soil. Emission of CO2 decreased 1.2 times in soil burned compared to soil where residue was incorporated, but emissions of N-2 increased 4.1 times and the increase in inorganic N or the N mineralization rate 1.4 times. Including Sesbania spp. in the crop rotation reduced N mineralization rate 1.2 times when residue was burned, but increased it 1.5 times when it was incorporated compared to clean fallow or the cultivation of maize. Fertilizing soil with urea increased the N mineralization rate 4.9 times and the N2O emission 2 times while chicken manure increased it 11.4 times and 3.7 times, respectively, compared to the unamended soil when residue was burned. It was found that burning of crop residue increased N mineralization and N-2 emissions, but decreased microbial activity. Addition of chicken manure increased emissions of N2O and CO2 and concentrations of NO (3) (-) .