ANALYSIS OF THE GROWTH OF SOYBEANS AS AFFECTED BY PLANT POPULATION AND FERTILIZER

Abstract

Net assimilation rate (NAR), relative growth rate (RGR) and relative leaf growth rate (RLGR) of soybeans [Glycine max (L.) Merrill] declined throughout the season; much of this decline and most effects of plant population on growth could be attributed to a rise in leaf area index (LAI). Increase in LAI from 0.3 to 1.0 was associated with a marked decrease in NAR. Crop growth rate (CGR) increased for the first 50 to 60 days, falling sharply thereafter. There was no optimum value of LAI.Fertilizer increased final plant weight mainly by delaying the fall in NAR and CGR. LAI was increased slightly by fertilizer application, presumably because of a higher RLGR between 50 and 70 days.The classical and regression techniques of growth analysis gave similar results, but the lower standard errors obtained with the latter revealed additional treatment effects. In some circumstances, smoothed curves used to describe growth might conceal growth fluctuations due to environmental stress.