Row Spacing and Seeding Rates for Soybean in Low and High Yielding Environments

Abstract

Response of soybean [ Glycine max (L.) Merr.] to changes in row spacing and seeding rate have been variable. Some researchers have reported grain yields to be higher with the use of narrow row spacings. Other investigators have found that wide row spacings provided grain yields equal to or greater than those obtained with narrow row spacings. This study was designed to determine the influence of environment on the optimum row spacing and seeding rate for soybean. Eleven field experiments were established in Kansas from 1991 to 1993. Four seeding rates in 1991 and five seeding rates in 1992 and 1993, ranging from 52 272 to 261 360 seeds/acre, were used in 8‐ and 30‐in. rows. At high yielding sites, maximum grain yields were higher with 8‐in. rows than with 30‐in. rows. If moisture stress reduced grain yields, maximum yields were greater with 30‐in. rows than with 8‐in. rows. Response to changes in seeding rate varied between row spacings depending upon environmental conditions. Under high‐yielding conditions, grain yields were maximized with 30‐in. rows at approximately 115 000 seeds/acre, whereas seeding rates of 203 000 to 232 000 seeds/acre were required to maximize grain yields with 8‐in. rows. Under conditions of limited soil moisture, grain yields were not affected by changing seeding rates. At sites with adequate soil moisture, mature plant heights increased as seeding rates increased. At moisture‐deficient sites, plant height was not significantly affected by increased seeding rates. Research Question Recommendations for soybean row spacing and seeding rate are generally constant within a geographical area regardless of yield goal or yield potential. This research was designed to determine the influence of environment on the optimum row spacing and seeding rate for soybean. Literature Summary Many researchers have reported that soybeans planted in narrow row spacings produced higher yields than did soybeans planted in wider row spacings. Other investigators found little or no yield increase with the use of narrow row spacings. Some researchers have reported that soybeans planted in narrow rows had greater water‐use efficiency than did soybeans planted in wider rows. Other investigators, however, found that, under conditions of severe water stress, water‐use efficiency was greater with wide rows than with narrow rows. Yield response to changes in plant population usually have been small and often inconsistent. Generally, increasing plant populations has increased plant height at maturity. It has been reported that higher plant mortality occurred with wide rows than with narrow rows. Study Description This research was conducted from 1991 to 1993 at 11 dryland locations in Kansas. In 1991, four seeding rates ranging from 52 272 to 209 088 seeds/acre were used in 8‐ and 3041‐1. rows. In 1992 and 1993, an additional seeding rate of 261 360 seeds/acre was added. Plant populations were determined 5 wk after planting. Plant lodging, mature plant heights, and grain yields were measured at maturity. Corsica was the cultivar used at eight environments, Resnik at two envirpnments, and Kunitz at one environment. Applied Question How did row spacing and seeding rate affect grain yields? The growing conditions at a site affected the yield response to changes in row spacing and seeding rate. Under high‐yielding conditions, maximum grain yields were higher with 8‐in. rows than with 30‐in. rows (Fig. ). If moisture stress limited grain yields, however, maximum yields were greater with 30‐in. rows than with 8‐in. rows. The response to increased seeding rates was dependent upon environmental conditions and row spacing. Under high‐yielding conditions, yield response to increases in seeding rates changed depending upon row spacing. Grain yields were maximized with 30‐in. rows at approximately 115 000 seeds/acre, whereas 203 000 to 232 000 seeds/acre were needed to maximize grain yields with 8‐in. rows. If soil moisture was limiting, grain yields were not affected by increased seeding rates. Soybean grain yields as affected by row spacing and seeding rate combined over site‐years with high yield levels. image How should yield potential affect recommendations for soybean row spacing and seeding rate? Seeding rate and row spacing recommendations should be adjusted depending upon expected environmental conditions. Under high‐yielding conditions where moisture is adequate, soybeans planted in narrow rows generally yield higher than soybeans planted in 30‐in. rows. If soybean growth is expected to be limited by moisture stress, however, grain yields may be higher with 30‐in. rows. Seeding rates should be substantially higher with narrow rows than with wide rows, especially if high‐yielding conditions are expected during the growing season.

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