Impact of corn plant maturation and planting density on nutrient composition and potential milk yield

Abstract Text: Stage of maturity and planting density can alter weight and nutrient composition of corn plants within the silage harvest window and thereby alter both yield and the nutritional value of corn silage.  To appraise effects of maturity and plant density on yield and nutrient composition, nine Pioneer silage hybrids (109 to 115 day relative maturity) were planted in a single field near Lexington, IL with 69000 and 84000 plants per hectare.  Duplicate sets of five representative plants were harvested at 3 to 4 day intervals within the silage harvest window (28 to 42 percent DM), weighed and chopped.  Duplicate subsamples were dried (48 h at 15 C) and assayed by calibrated NIR procedures for CP, starch, sugars, NDF, and NDF digestibility.  Averaged across harvest dates, hybrids differed (P < 0.01) in all measurements.  The 21 percent increase in plant density decreased (P < 0.05) starch content of plant DM by 1.5 percentage points and milk per ton by 2.5 percent, but increased (P < 0.01) yields of DM, milk, NDF, digestible NDF, and indigestible NDF per hectare by 7.2, 7.0, 9.0, 8.0, and 10 percent.  Across hybrids, linear and quadratic regressions against harvest DM were significant (P < 0.05) for starch content, protein content, milk per ton (each increasing at a decreasing rate), and sugar content (decreasing to a plateau). As plant DM percentage increased, yield of DM increased but NDF digestibility declined (P < 0.01) slightly (0.09 points for each 1 percentage increase in plant DM.  In corn silage test plots, all hybrids typically are harvested on a single date regardless plant moisture content.  Among these nine hybrids, ranking for milk per hectare remained reasonably similar across this DM range; milk per ton ranking changed markedly, especially when plant DM was below 34 percent, although rank of the top (a BMR) and bottom hybrids remained similar.  In conclusion, increasing planting density increased corn silage yield with some sacrifice in starch percentage.  Hybrid ranking for milk per ton differed with harvest DM.  To prevent ranking bias, hybrids in silage test plots should be harvested at multiple moisture contents.

Keywords: Corn plant maturity, planting density, hybrid ranking