Plant density effects on tropical corn forage mass, morphology, and nutritive value

Tropical corn (Zea mays L.) has potential as a silage crop in double-crop systems,vith cool-season annual grasses in the southeastern USA. In a 3-yr study conducted in silt loam soils in southeast Louisiana, plots within stands of Pioneer hybrid X304C tropical corn planted at 89 000 plants ha(-1) were thinned to achieve harvested plant densities of 44 830, 52 150, 58 130, 65 150, and 72 920, plants ha(-1) to determine the effect of plant density on total forage mass, plant morphology, and forage nutritive value of tropical corn. Total forage mass was greater at higher plant densities than at lower plant densities, but forage mass was not different among plant populations that exceeded 58 130 plants ha(-1). Leaf concentration of dry matter did not differ among plant populations and averaged 300 g kg(-1). The sum of stem and grain concentrations was similar among treatments and ranged from 622 to 637 g kg(-1). Within the stem and grain components, grain concentration decreased and stem concentration increased in an almost one-to-one relationship as plant density increased. Forage nutritive value of tropical corn was similar among plant densities. In vitro true digestibility averaged 654 g kg(-1) across all plant densities. Increasing forage mass, coupled with stable forage nutritive values, indicates that, until some factor limits production of high-quality tropical corn. silage, high plant densities are desirable. Under the environmental conditions of this experiment, it appears that plant densities of about 58 000 plants ha(-1) are optimal.