Response of Soybeans to End‐Trimming at Various Growth Stages1

Abstract

Two soybean (Glycine max (L.) Merrill) cultivars in each of maturity groups I to IV were end‐trimmed at seven growth stages, from the first trifoliolate stage to maturity. Seed yield and seed size were recorded on two .3‐m sections at the ends of plots and on a 3‐m section in the center of plots. Data indicated that significant border effects in maturity groups II to IV, grown at Lafayette, Ind., extended more than .3‐m from the ends of plots. Border effects could be adequately controlled by trimming .6 m from each end of the plots when the top pods on plants were fully extended with seeds approaching full size for cultivars in groups I to III. Trimming would have to be delayed until leaves on plants were 30 to 50% yellow with a few falling for group IV varieties or strains. Plot yields could be adjusted to those of 4.9‐m rows trimmed at maturity by end trimming to 4.9 m at or before the first trifoliolate stage and multiplying plot yields by .874, .840, .796, and .755 for cultivars in maturity groups I to IV, respectively. Size of seed on plants at the ends of rows was increased only when end trimming was done at full bloom or as soon as flowering ceased.