Digestibility and Lignocellulose Composition of Forage Corn Morphological Components

Abstract

Hot weather, limited rainfall during the growing season, and low soil fertility limit corn (Zea mays L.) production for silage in south central USA (e.g., Texas). Our objective was to examine the effects of supplemental irrigation, plant density, and N rate on quality of forage maize. Pioneer brand hybrid 3165 was planted at four densities (7 250, 14 500, 29 000, and 58 000 plants/acre) in rows spaced 3-ft apart in 1987, 1988, and 1989. Nitrogen was applied at 0, 160, or 320 lb/acre each year. Plots were either not irrigated or received supplemental irrigation when plants exhibited leaf rolling. Treatments were arranged as split-split plots randomized in four complete blocks. Water treatments were whole plots, N rates subplots, and plant densities were sub-subplots. Plots were harvested at dent stage of grain (33 to 37 % dry matter). Whole plants, leaf blades, and stalks were analyzed for in vitro true digestibility (IVTD), acid detergent fiber (ADF), cellulose, and acid detergent lignin (ADL; except leaf blades) via near infrared reflectance spectroscopy (NIRS). In 1987, concentrations of ADF, ADL, and cellulose increased by 20 to 40 %, whereas IVTD was reduced by 4 to 6 % in all components with increased plant density when 160 or 320 ld N/acre was applied, whereas under 0 N fiber concentrations and IVTD changed little, if any, with increased plant density. Supplemental irrigation did not affect whole-plant forage quality, whereas IVTD of leaf blades and stalks from irrigated plots was reduced by 3 to 5 %, respectively, with applied N in 1988 but not in 1987 or 1989. Quality of corn forage may have to be considered in plant density recommendations