Effects Of Density On Growth And Yield Of Spring Soybean Under Mulched Drip Irrigation

The effects of five densities 21.0×10⁴plants·hm^-2（D1）,27.0×10⁴plants·hm^-2（D2）,30.0×10⁴plants hm^-2（D3）,33.0×10⁴plants·hm^-2（D4）,36.0×10⁴plants·hm^-2（D5）on root growth,leaf area index,dry matter accumulation and dynamic changes of flowers and pods of Henong71were systematically studied in the field.（1）Under drip irrigation,the flowering time of D1 was 2 days longer than other treatments,and the podding time of D1 and D2 was 4 days longer than other treatments.With the increase of density,the number of flowers and pods in nodes 9–15 of main stem increased.Flower number per plant and pod number per plant decreased with the increase of density;the total flower number increased with the increase of density;the total pod number and total pod number increased first and then decreased with the increase of density.The total pod number of D2 treatment was larger,which increased by 5.48%–23.72%compared with other treatments.（2）Under mulched drip irrigation,the total root dry weight,total lateral root length and total lateral root surface area in 0–100 cm soil layers of each treatment showed a trend of first increase and then decrease in the growth period of soybean,with the highest value in D2treatment at the peak.Compared with other treatments,the total dry matter content of D2roots at R5 stage increased by 5.26%–26.95%.The roots of each treatment were mainly distributed in 0–40 cm,and the root dry mass density,lateral root length density and lateral root surface area density in 40–80 cm soil layer showed an increasing trend with the increase of density.（3）Under the condition of drip irrigation under mulch,the leaf area index of each treatment appeared peak in R5 stage,and increased with the increase of density.The photosynthetic potential and leaf area index of D2 treatment were higher than those of other treatments at the late filling stage,so the dry matter accumulation increased by 1.15%-21.29%compared with other treatments.At the same time,the grain yield of D2 treatment was 5636.67 kg·hm^-2,which was 9.03%–20.61%higher than other treatments.（4）Under mulched drip irrigation,root dry weight,lateral root length and lateral root surface area increment at flowering and podding stages were significantly positively correlated with pod number,with correlation coefficients of 0.9784**,0.9502*and 0.9690*,respectively.Root dry weight,lateral root length and lateral root surface area were significantly positively correlated with yield.The correlation coefficients are 0.8900*,0.7919*and 0.8123*,respectively.Therefore,the population structure of D2 treatment delayed leaf senescence,obtained a better leaf area index curve,increased plant dry matter accumulation,increased the formation of flowers and pods,increased the number of cavities and seed setting rate,so as to improve soybean yield.