Milk prices have shrunk substantially in the last year. Because forages are much cheaper than concentrates, increasing the inclusion of forages in rations for dairy cows can help sustain margins and profitability. On the flip side, forage stocks could decrease faster as the inclusion of forages in dairy rations is increased. As a consequence of the limited forage stocks observed after drought seasons, increasing interest has emerged to replenish forage stocks of corn silage faster through greater corn planting population rates. Previous studies have shown that under non-extreme weather conditions forage biomass of corn for silage increases or does not change when planting population increases.
During the summer of 2015 we measured dry matter yields of corn for silage when planted at different populations in two different fields at a dairy farm in southern Virginia. Plant populations ranged from 22,000 to 40,000 plants/acre with 6,000-plant/acre intervals. As in previous studies, dry matter yields increased linearly when planting population increased (Figure 1).
This increase was not seen during the summer of 2014 when corn plant population trials were performed in the same fields.
We should remember that rainfalls were quite frequent in most regions of the Commonwealth during summer 2015, which would explain the beneficial effect of increasing planting population on dry matter yields.
One consistent observation during both years, which also agrees with previous published studies, is that increasing corn planting density has minimal (if any) effects on the nutritional composition of the corn plant. Even though it resulted in smaller plants with smaller ears, increasing planting population did not change the concentrations of ash (3.5%), crude protein (9.2%), neutral detergent fiber (40.1%), sugars (9.1%), and starch (36.1%) of the corn plants for silage. These results were also observed on several previous studies, therefore suggesting that corn planting population has no effect on the nutritional composition of corn for silage.
Corn planting season is around the corner, so we are in “planning mode” for our corn crops. Although still inconclusive for extreme weather conditions, increasing planting populations may increase dry matter yields of corn for silage.
This practice may also help to replenish forage stocks in farming systems feeding increasing proportions of silage in dairy rations. Fertilization strategies, as well as the potential benefits and risks associated with this practice, should be carefully discussed and evaluated with your agronomy consultant.
Virginia Cooperative Extension materials are available for public use, reprint, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.
Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; M. Ray McKinnie, Administrator, 1890 Extension Program, Virginia State University, Petersburg.
March 31, 2016