EFFECT OF SOYBEAN STEM GROWTH HABIT ON HEIGHT AND NODE NUMBER AFTER BEGINNING BLOOM IN THE MIDSOUTHERN USA

Abstract

There are two broad types of stem growth habit in soybean [Glycine max (L.) Merr.]: indeterminate [generally maturity group (MG) IV and earlier] and determinate (generally MG V and later). Field studies of irrigated April and May plantings were conducted on Sharkey clay soil (very‐fine, smectitic, thermic Chromic Epiaquert) at Stoneville, MS (lat. 33°26′N), to determine if current expectations for stem growth habit are valid in genetic backgrounds of indeterminate MG IV and determinate MG V cultivars that are used in the early soybean production system (ESPS) in the midsouthern USA. All cultivars increased height and node number between beginning bloom (R1) and stem termination (ST), but the increases were greater for MG IV cultivars. Height and node number were greater at R1 for MG V than for MG IV cultivars, and greater for MG IV cultivars at ST. Averaged across planting date and year, MG V cultivars increased height and node number after R1 by 23 cm and 3.7 nodes, respectively. These results indicate that determinate MG V cultivars are capable of producing significant increases in height and node number after R1.