See more from this Session: Nutrient Management in Forages
Monday, November 1, 2010
Long Beach Convention Center, Exhibit Hall BC, Lower Level
For the sustained, safe use of swine lagoon effluent spray fields, the annual management of nutrients is critical, not just the summer yields. This 2-yr study was conducted at a commercial swine to determine the effects of spring N fertilization (0, 50, 100, 150 kg N ha-1) on forage dry matter (DM) yield and nutrient uptake by fall-overseeded annuals, annual ryegrass, cereal rye, and berseem clover, as compared to bermudagrass-winter fallow. Our hypothesis was that even with repeated manure applications in summer (April–Oct.), N availability limits growth and uptake of other nutrients by winter forages. Nutrient uptake was analyzed based on a single spring harvest and on two summer harvests of bermudagrass. The relative yield in spring, defined as DM yield at a given N rate divided by the maximum observed DM yield, varied from 77 to 98%, suggesting N nutrition was not strongly limiting, even at the lowest N rate. Cover crop N concentration increased as N rate increased (P < 0.05), and averaged approximately 15.2, 17.2, 18.4, and 20.8 g kg-1 across N rates in 2000 (5% LSD = 7), and 21.6, 22.1, 25.4, and 27.1 g kg-1 in 2001 (5% LSD = 2.4), respectively. The N rate by crop interaction was significant for herbage N in 2000, as values increased linearly in ryegrass from approximately 10 to 20 g N kg-1 as N rate increased, and did not vary significantly in cereal rye and berseem clover. Averaged across 2000 and 2001, P uptake in spring was greater in annual ryegrass than the other species (23.2 vs. ~17.7 kg ha-1) and was associated with 27% greater DM yield. This data supports more accurate N management in double-cropping forage systems, which provide environmental and economic advantages to producers who regularly utilize manure as fertilizer.