Effects of Plant Population on Photosynthetic Characteristics and Yield Components of Summer Soybean

To investiage the effects of plant population on the growth and physiological indexes of drip irrigated summer soybean,an field experiment was conducted by setting five different plant populations of 37. 5 × 104( A),45. 0 × 104( B),52. 5 × 104( C),60. 0 × 104( D) and 67. 5 × 104( E) plants·hm- 2under drip irrigation by using of randomized block experimental design in 2012 summer soybean growing season,and the leaf SPAD,leaf area index( LAI),photosynthetic characteristics and yield components of summer soybean were observed. Results showed that both the SPAD and LAI were improved along with the density increasing,but the leaf area per plant decreased with the density increasing. The net photosynthetic rate( Pn),transpiration rate( Tr) and stomatal conductance( Gs) were increased first,and then decreased with increasing density,Pn and Gs reached maximum in the R2 period,but Tr reached maximum in the R4 period,intercellular CO2concentration( Ci) was first decreased and then increased with increasing density. The differences in the yield between treatments were significant( P 0. 05),and Treamtment C had the highest yield of 3205. 04kg·hm- 2,which was higher 1. 42%,4. 09%,1. 42% and 5. 88% than Treatment A,B,D and E,respectively. The results can provide scientific and reasonable theory basis to the production practice for plant population of summer soybean under local conditions.