This study was one of three similar studies conducted in 2001 and three others conducted in 2000 in Wisconsin.
Conducted by: Greg Roth and Mark Antle
Location: Russell Larson Agricultural Experiment Station, Rock Springs
Collaborators: Dr. Mark Zarnstorff, Director of Agricultural Research/Technology National Crop Insurance Services
To evaluate the effects of simulated hail damage on the yield and quality of corn silage.
Although many studies have documented the effect of simulated hail damage on corn harvested for grain, the effect of hail damage on corn silage yield is not well documented. Since loss of leaf tissue can have a greater impact on silage yields than grain yields and hail damage could affect silage forage quality, it was important to quantify these effects. Thus the objective of this study was to quantify the effects hail damage had on corn silage yield and quality. This study was one of three similar studies conducted in 2001 and three others conducted in 2000 in Wisconsin.
This study was conducted on the Russell Larson Ag Experiment farm about 10 miles west of State College, Pennsylvania. The soil was a Hagerstown silt loam that was cropped to corn the previous year, then chisel plowed and disked in the spring prior to planting. Urea fertilizer was applied to the field prior to the last disking at a rate to supply 150 pounds of N/acre. The trial was established on May 1, 2001 by planting the corn hybrid Pioneer 34G82 at a population of 32000 seeds/acre in 30-inch rows. A 7-21-7 liquid starter fertilizer was applied at planting at 11 gallons/acre. Force 3G insecticide was applied in a T-band application at the labeled rate for corn rootworm control. Weeds were controlled with a pre emergence application of Bicep herbicide followed by postemergence application of Accent and Pinnacle at the V5 stage of growth. Resulting weed control was excellent, however we did notice some crop injury, which may have reduced the height of the crop slightly.
Defoliation was simulated by clipping off the ends of leaves to represent the following conditions: 100% defoliation at V7, V10, silking and early dough; 50% defoliation at V10, silking, and early dough; 25% defoliation at silking and early dough. We also included a non-defoliated check treatment. This resulted in a total of 10 treatments. Each treatment was replicated four times in four row, 25 foot long plots.
At harvest on September 10, one of the interior 25-foot rows was removed and the resulting forage was weighed in the field. A 5-plant sub sample was chopped to obtain a 750 g sub sample for dry matter determination and for forage quality analysis. Samples were dried for 72 hours in an oven at 140 F to determine dry matter content. The dried samples were then boxed and shipped to Dan Wiersma at the University of Wisconsin for grinding and forage analyses. Yield, moisture, and quality data were analyzed with SAS. Mean separations were conducted using Fisher's LSD at the p=0.05 level.
Defoliation treatments caused significant effects on yields as expected (Table 1). Vegetative leaf stages were defined using the leaf collar method, which results in about two fewer leaves than the typical staging system used by hail adjusters. Thus, V7 corn would really be 9-leaf corn according to the hail adjusters growth staging system.
Forage yield losses due to defoliation were comparable to predicted grain yield losses from a commonly used chart. Averaged across all treatments, estimated forage losses were 26.9% compared to an average predicted grain yield loss of 27.3%. This compared to an average forage yield loss of 26.6% in 2000. Losses compared to 2000 were relatively similar for many treatments, the exception being that the 2001 yield losses were less for the V7 and V10 defoliations, but greater for the early dough defoliations.
|% Forage Yield Reduction||% Forage Yield Reduction in 2000||Predicted % Grain Yield Reduction**||% DM|
There was a large difference in forage quality among the different treatments. The forage was analyzed for crude protein (CP), neutral detergent fiber (NDF), neutral detergent fiber digestibility (NDFd), starch, and ash. Some of the largest quality differences were with the 100% defoliation treatment at silking. This treatment was significantly higher in CP, NDF and Ash, but lower in starch than all others. Due to the fact that the 100% defoliation at silking treatment completely stripped the plant of it's leaves at such a critical time, none of these plants produced any grain.
A summary of the quality analyses from the 2001 trial is shown in the table below.
|Growth Stage||% Defoliation||CP||NDF||dNDF||Starch||Ash||Milk/Acre||Milk/Ton|
This study supports the idea that silage yield losses due to hail damage are comparable to grain yield losses. There also is strong evidence that large forage quality differences are present among different levels of hail damage.