Yields, Nutrient Removal, and Nutrient Concentrations of Double-Cropped Corn and Small Grain Silage

Double-cropping corn (L.) and small grain silage has become an important practice but there is virtually no research information upon which to base fertility or management decisions. Consequently a double-cropping corn and small grain silage experiment was conducted at two locations in Kentucky. The study was initiated to determine production levels from doublecropped silage, the most compatible small grain species for double-cropped silage, and the rate and method of fertilizer application needed for high production. Field experiments were established on Huntington (fine-silty, mixed mesic fluventic Hapludoll) and Pope (coarse-loamy, mixed, mesic fluventic Dystrochrept) soils. Three fertility levels were tested with 392-128-280, 280-89-232, or 168-54-140 kg/ha of N-P-K being applied each year. Single and split applications of K were studied. Barley (L.) and oats (L.) were compared as small grain species. Double-cropped silage produced 26% more dry matter than single cropped silage. Since most of the total silage yield was due to corn, the harvesting management favored this crop so that its yield potential would not be reduced. As a result all small grain species were harvested on the same date and large differences in stage of maturity existed. The small grain species or its stage of maturity at harvest were found to affect the yield of the succeeding corn crop. Corn grown after barley, harvested in soft dough, averaged 25% more yield than that grown after oats, harvested at heading. Fertility rates above 280-89-232 kg/ha of N-P-K (250-180-250 lb/A of N-P0-KO) did not significantly increase the yield. The average nutrient removal at the foregoing rate of fertility was 241-54-260 kg/ha of N-P-K. The small grain accounted for 47% of the total K removed. Split applications of K increased the corn silage yield at the low application rate (140 kg/ha/yr). At one of the two locations the corn yields were 33% higher when one-half of the total annual K was added to each crop as opposed to adding all of the K at the time of small grain planting. This study indicates that double-cropped corn and small grain for silage can result in substantially higher dry matter production per unit land area than single-cropped corn. Large amounts of minerals are removed, however, particularly K, by the small grain component of the double-cropping system.