Jeff is a dairy farmer, and raises much of his own feed. He was interested in experimenting with a mixture of soya and corn for silage. Rather than growing the crops separately and mixing them after harvest however, he and Craig Altemose of the University of Vermont Cooperative Extension Service, who worked with him on this project, conceived the idea of interplanting the two crops together in the same field.
They modified a John Deere 7000 4-row planter by placing soybean cups on the middle two planter boxes, thus enabling them to plant two rows of corn simultaneously with two rows of soya on each pass over the field. Herbicide (Dual II Magnum) was applied at the rate of 1.33 pints per acre. It should be noted that there are few, if any, other options for chemical weed control on a mixed stand of corn and soya.
Corn was planted at a rate of 30,000 seeds per acre, soya at a rate of 200,000. The stand of soya that developed, however, was only about 80,000 plants per acre; germination was poor because the seeds were accidentally planted too deep. The crop was planted on May 18, 1999, and harvested on September 20 with a 2-row harvester. A row of corn and a row of soya were cut on each pass and blown together into the truck, so that they were already well mixed before loading into the silo.
The summer of 1999 was notoriously dry. Two fields were planted; the soil under one was a well-manured Hadley silt loam, and under the other, a not-so-well manured sandy loam. The crops on the sandy loam suffered badly, but on the silt loam moisture retention was adequate to produce respectable yields, which are presented here. A sample of the silage made from this corn-soya mix was taken on 2/2/2000 (at which time it was used for feed) and analyzed; pertinent data from this analysis are also presented. All figures (except for % moisture) are on a dry matter basis.
Soya yielded 3.24 tons per acre, and corn, 7.82 tons. Overall yield was the mean of these, or 5.53 tons per acre. Data for the silage are given below:
Moisture content – 61.5%
Crude protein – 10.9%
Acid detergent fiber – 21.1%
Neutral detergent fiber – 36.7%
Fat – 3.6%
Net energy of lactation – 0.77 Mcal/lb
Total digestible nutrients – 72.3%
Jeff summarizes the experiment as follows: “Soybean silage does seem to fit as a replacement for alfalfa haylage. The quality and yields do match well under normal growing conditions. There is more control of management in the field than there is with alfalfa, especially since you never know how much alfalfa will survive the winter.
“I was able to feed a lower protein grain and maintain the same milk production, and butterfat and protein content. The soybean silage fed out like alfalfa haylage and it did raise the protein of the ration to the dairy herd. Like alfalfa haylage the forage was wet and high in protein which I think causes the cows’ manure to be runny. Wilting the forage at harvest, in the field, to a lower moisture level, may be necessary.”
Craig did an economic analysis, which showed a profit of $319 per acre with the corn-soya mixture on the silt loam field, where it yielded well. On the sandy loam field, where the crop was severely impacted by drought, Craig’s figures show that Jeff just about broke even.