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Crop residue effect on crop performance, soil N(2)O and CO(2 )emissions in alley cropping systems in subtropical China

Guo, Z. L., Cai, C. F., Li, Z. X., Wang, T. W., Zheng, M. J.
Agroforestry systems 2009 v.76 no.1 pp. 67-80
Triticum aestivum, wheat, Zea mays, corn, Vicia faba, faba beans, Amorpha fruticosa, Chrysopogon zizanioides, alley cropping, agroforestry, soil texture, crop yield, soil fertility, nitrous oxide, carbon dioxide, gas emissions, soil water content, nitrogen, mineralization, crop residues, greenhouse gases, soil organic carbon, China
Land management practices that simultaneously improve soil properties are crucial to high crop production and minimize detrimental impact on the environment. We examined the effects of crop residues on crop performance, the fluxes of soil N(2)O and CO(2) under wheat-maize (WM) and/or faba bean-maize (FM) rotations in Amorpha fruticosa (A) and Vetiveria zizanioides (V) intercropping systems on a loamy clay soil, in subtropical China. Crop performance, soil N(2)O and CO(2) as well as some potential factors such as soil water content, soil carbon, soil nitrogen, microbial biomass and N mineralization were recorded during 2006 maize crop cultivation. Soil N(2)O and CO(2) fluxes are determined using a closed-based chamber. Maize yield was greater after faba bean than after wheat may be due to differences in supply of N from residues. The presence of hedgerow significantly improved maize grain yields. N₂O emissions from soils with maize were considerably greater after faba bean (345 g N₂O-N ha⁻¹) than after wheat (289 g N₂O-N ha⁻¹). However, the cumulated N₂O emissions did not differ significantly between WM and FM. The difference in N₂O emissions between WM and FM was mostly due to the amounts of crop residues. Hedgerow alley cropping tended to emit more N₂O than WM and FM, in particular A. fruticosa intercropping systems. Over the entire 118 days of measurement, the N₂O fluxes represented 534 g N₂O-N ha⁻¹ (AWM) and 512 g N₂O-N ha⁻¹ (AFM) under A. fruticosa species, 403 g N₂O-N ha⁻¹ (VWM) and 423 g N₂O-N ha⁻¹ (VFM) under Vetiver grass. We observed significantly higher CO₂ emission in AFM (5,335 kg CO₂-C ha⁻¹) from June to October, whereas no significant difference was observed among WM (3,480 kg CO₂-C ha⁻¹), FM (3,302 kg CO₂-C ha⁻¹), AWM (3,877 kg CO₂-C ha⁻¹), VWM (3,124 kg CO₂-C ha⁻¹) and VFM (3,309 kg CO₂-C ha⁻¹), indicating the importance of A. fruticosa along with faba bean residue on CO₂ fluxes. As a result, crop residues and land conversion from agricultural to agroforestry can, in turn, influence microbial biomass, N mineralization, soil C and N content, which can further alter the magnitude of crop growth, soil N₂O and CO₂ emissions in the present environmental conditions.