INFLUENCE OF POPULATION DENSITY AND HYBRID MATURITY ON PRODUCTIVITY AND QUALITY OF FORAGE MAIZE

Abstract

Nine maize hybrids, representing early, medium and late maturities (maximum 3000 corn heat units), were grown at 75 000 and 100 000 plants/ha for 2 yr at two locations in order to examine the in vitro digestible dry matter (DDM) yield and quality of whole-plant (shoot) and stover components. Early hybrids produced 90% as much DDM yield as medium or late hybrids. Comparing densities, the higher density resulted in a greater increase in DDM yield at Surrey than at Agassiz and it did not depress whole-plant dry matter (DM) content. Whole-plant DM digestibility (DMD) was 2% lower for early hybrids compared to mediums or lates. Density had no influence on whole-plant DMD at Surrey, but the higher density reduced it by 1% at Agassiz. Stover DDM yield was greater at Surrey than at Agassiz whereas whole-plant DDM yield was greater at Agassiz. Harvest index was positively, but not closely, correlated with whole-plant DMD (r = 0.28***) and was inversely correlated with stover DMD (r = − 0.45***). Thus, nutritive value of maize was only marginally dependent on the grain component. Results suggest that, in the marginal corn-growing environments of the region studied, it may be beneficial to use hybrids considerably later than those normally adapted and grow them at a density approaching 100 000 plants/ha to maximize digestible yields and quality. The harvested forage may have a DM content too low for direct ensiling, but this can be rectified by addition of dry high-protein supplements (e.g. alfalfa cubes) at ensiling time.