Narrow-Row Planting Systems for Furrow-Irrigated Soybean

Abstract

Narrow rows are often associated with soybean [Glycine mar (L.) Merr.] yield improvements but results have varied depending on environment, cultivars, and management practices. The effect of narrow rows in conjunction with furrow irrigation and the response of soybean cultivars with different growth habits to narrow-row planting systems or furrow irrigation spacings have received limited attention in the mid western USA. The objectives of this study were to: (i) determine if narrow- and twin-row planting systems offer yield advantages over the conventional wide-row planting system for furrow-irrigated soybeans; and (ii) determine the response of soybean cultivars with different growth habits to planting system and furrow spacing. During 1988, 1989, and 1990, we conducted experiments at South Central Research and Extension Center near Clay Center, NE, using three planting systems: wide, twin, and narrow; and two furrow-irrigation spacings: alternate- (or furrows spaced 60 in. apart) for the three planting systems and every-furrow irrigation (or furrows spaced 30 in. apart) for the wide- and the twin-row planting systems. Soybeans in narrow-and twin-row planting systems and determinate cultivars did not have yield advantages over the conventional wide-row planting system and indeterminate cultivars, respectively, in a year with yield-limiting conditions. However, in a year with no yield-limiting conditions and with a larger amount of total water available for soybean plants at early reproductive periods, narrow- and twin-row planting systems offered yield advantages over the wide-row planting system. Determinate cultivars yielded more than indeterminate cultivars only in the twin-row planting system and every-furrow irrigation. In a year with above average rainfall but unfavorable rainfall distribution pattern, there were no yield differences between either the narrow- and the wide-row planting systems or determinate and indeterminate cultivars. We recommend narrow and twin rows with determinate cultivars for south-central Nebraska only if the irrigation system has adequate capacity and is managed properly to provide adequate water early in the season. Research Question Narrow rows have increased soybean yields under certain conditions. The effect of narrow rows in conjunction with furrow irrigation has received limited attention in the Midwestern USA. The primary objective of this study was to determine if narrow- and twin-row planting systems can produce more yield than the conventional wide-row planting system for furrow-irrigated soybeans. The responses of determinate and indeterminate cultivars to planting systems and how spacings were also evaluated. Literature Summary Several workers have studied the effect of narrow rows on soybean yields in many regions and have found inconsistent results. Not all studies have shown soybean yield increases by using narrow rows since results have been dependent on environment, cultivar, and management practice. The effect of narrow rows in conjunction with furrow irrigation for soybean production has not been studied extensively because of the difficulty in establishing narrow-row planting systems with furrow irrigation. The use of alternate-furrow irrigation (furrows 60 in. apart) allows a wide bed between furrows that accommodates narrow rows. The response of soybean cultivars with different growth habits to planting systems and furrow spacings has not been documented. Study Description Experimental site: This 3-yr field study (1988–1990) was conducted at the South Central Research and Extension Center Farm near Clay Center, NE, on a Hastings silt loam soil (fine, montmorillonitic, mesic Udic Argiustoll). Seeding rates were 3.6 and 4.8 seeds/sq ft for the 3 indeterminate and the 2 determinate cultivars, respectively. Planting systems were: a) wide rows (30 in. between rows), b) twin rows (paired rows separated from each other by 10 in. and from other pairs by 20 in.), and c) narrow rows (10 in. between rows). Furrow spacings were: a) alternate (60 in. between irrigated hows) for all three planting systems and b) every (30 in. between irrigated furrows) for wide and twin rows only. Applied Questions Was the yield response in narrow and twin rows the same as in wide rows for furrow-irrigated soybean? No. In a year with yield-limiting conditions including potential early drought stress (1988), narrow and twin rows resulted in lower soybean yields than wide rows (Fig. 1). However, in a year with no yield-limiting conditions and with a larger amount of total water available for soybean plants at early reproductive periods (1989), narrow and twin rows resulted in greater soybean yield than did wide rows. In a year with above average rainfall but not an ideal distribution pattern (1990), there were no yield differences between wide and narrow rows. Was the yield response of determinate and indeterminate soybean cultivars the same across planting systems and furrow spacings? No. Indeterminate cultivars yielded more than determinate cultivars in both wide and twin rows and with both furrow spacings in 1988 (Fig. 2). However, in 1989, determinate cultivars yielded the same as indeterminate cultivars in wide rows and with alternate-hrrow irrigation but more than indeterminate cultivars in twin rows and with every-furrow irrigation. There were no yield differences between determinate and indeterminate cultivars in 1990. Recommendation We recommend narrow rows for alternate-furrow irrigation and twin rows for alternate- and every-furrow irrigation as long as the imgation system is able to provide enough water during early reproductive growth. If potential early drought stress is possible (e.g., limited irrigation or systems with water delivery restrictions), farmers should plant wide-row soybeans. We recommend determinate cultivars for any combination of the planting systems and furrow spacings studied here as long as the irrigation system is able to provide enough water during early reproductive growth. If there is any possibility of early drought stress, farmers should plant indeterminate cultivars or both determinate and indeterminate cultivars to minimize risk. Figure 1Open in figure viewerPowerPoint Soybean yields as affected by planting system with alternate-furrow irrigation 1988–1989. With every-furrow irrigation, the wide and twin rows followed a similar pattern to that shown in this figure. Figure 2Open in figure viewerPowerPoint Soybean yields as affected by furrow spacing and soybean growth habit, 1988–1990.