6Guo J H, Liu X J, Zhang Y, et al. Significant acidification in major Chinese cropland [J]. Science, 2010,327: 1008-1010.
7Klebsadel L J. Chemical composition and yield of oats and peas separated from a forage mixture at successive stages of growth[J]. Agronomy Journal, 1969, 61: 713-716.
8Rusinamhodzi L, Corbeels M, Nyamangara J, et al. Maize- grain legume intercropping is an attractive option for ecological intensification that reduces climatic risk for smallholder farmers in central Mozambique[J]. Field Crops Research, 2012, 136(20): 12-22.
9Isaaca M E, Hinsingerc P, Harmanda J M. Nitrogen and phosphorus economy of a legume tree-cereal intercropping system under controlled conditions [J]. Science of the Total Environment, 2012, 434(15): 71-78.