Production Practices Improve Grain Sorghum and Pearl Millet Competitiveness with Weeds

Abstract

AbstractPearl Millet [Pennisetum glaucum (L.) R. Br.] is a new grain crop adapted to many grain sorghum [Sorghum bicolor (L.) Moench] production regions, but weed control is often difficult, due to slow initial crop growth and limited herbicide options. An experiment was conducted in 1994 and 1995 to compare the competitiveness of pearl millet topcross hybrid 79‐2068A/NPM‐1 and grain sorghum singlecross hybrid DK28 with velvetleaf (A butilon theophrasti Medik.) and foxtail (Setaria spp.) as influenced by crop row spacing and N fertilizer application. The experiment was conducted on a Sharpsburg silty clay loam (fine, smectitic, mesic, Typic Argiudoll) near Mead, NE. Crops were planted in rows 38 and 76 cm apart, and N rates were 0 and 78 kg ha−1. Weed levels were obtained by differential herbicide applications at 7 d after emergence and by hand weeding. Yield losses of grain sorghum in 1994 and 1995, and pearl millet in 1995, were described by a nonlinear model based on a rectangular hyperbola. As velvetleaf and foxtail biomass approached zero, grain yield reduction of both crops was similar. In 1994, as weed pressure increased, grain sorghum yield loss was less in 38‐cm than in 76‐cm row spacing. In 1995, row spacing had no effect on grain yield. In contrast, pearl millet grain yield loss was greater in 38‐cm than in 76‐cm row spacings as weed level increased in 1995. All yield components of both crops were affected by weed level: number of kernels per head was influenced the most. Nitrogen fertilizer application enhanced yield of both crops by an average of 1.15 Mg ha‐1 in the 1994 season, but did not increase yield in the dry 1995 season. Narrowing row spacings from 76 to 38 cm increased grain yield of both crops by an average of 1.06 Mg ha−1 in 1994 and 0.83 Mg ha−1 in 1995. Grain yields of both crops were enhanced by weed control, narrow row spacing, and N application with adequate seasonal precipitation.