6Minchin F R, Summerfield R J, Newes M C P. Carbon metabolism, nitrogen assimilation, and seed yield of cowpea ( Vigna unguiculata L. Walp. ) grown in an adverse temperature regime [ J ]. Journal of Experimental Botany , 1980,31 : 1327 - 1347.
7Spaeth S C, Sinelair T R. Variation in nitrogen aceumulation and distribution among soybean cultivars [ Glycine. max. genotypes ][J]. Field Crops Research. 1983,1:1 - 12.
8Kanshal T, Onda M, Ito S, et al. Effect of deep placement of slow release fertilizer (Lime nitrogen ) applied at different rates on growth,N2 fixation and yield of soybean[J]. Journal of Agronomy and Crop Science, 2006, 192(6) :417 -426.
