 |
Main Menu | Search | CD Help | Access the Technical Program
Note: Program subject to change without notice
Wednesday, November 7, 2007
327-6
Effect of Swine Effluent Rate and Timing on Nitrogen Utilization and Residual Soil Nitrogen in Common Bermudagrass.
John Read, P.O. Box 5367, USDA-ARS, Crop Science Research Lab, 810 Hwy 12 E, Mississippi State, MS 39762-5367, Geoffrey Brink, 1925 Linden Dr West, USDA-ARS, USDA-ARS, US Dairy Forage Research Center, Madison, WI 53706-1108, Steven Mcgowen, USDA-NRCS, USDA-NRCS, 4900 Oklahoma Avenue Suite 300, Woodward, OK 73801, and James G. Thomas, Agricultural and Biological Engineering, Mississippi State University, Box 9632, Mississippi State, MS 39762-9632.
Frequent summer precipitation in southeastern USA may delay applications of swine effluent to bermudagrass [Cynodon dactylon (L.) Pers.] hay fields until late summer or early fall. Due to declining growth of this warm-season forage in fall, there is potential for excessive soil N and nitrate (NO3) leaching. Studies were conducted on a Prentiss sandy loam to determine the effects of application rate and timing on forage dry matter (DM) yield, N uptake and postseason soil N concentrations in common bermudagrass. Effluent was applied at 10 and 20 cm ha-1 (about 260 and 480 kg ha-1 N, respectively) during four spray seasons: April to September (full season), April to May, June to July, and August to September. Plots were harvested every 7-9 wk beginning in mid-June, and soil sampled after a killing frost and the following spring. Doubling the effluent rate increased annual N uptake by forage from about 130 to 276 kg N ha-1 in 2000, and from 190 to 290 kg N ha-1 in 2001. Applying effluent in August-September led to lower DM yield and N uptake, as compared to other seasons, and for 20 cm ha-1 rate, to elevated levels of residual soil NO3 in fall 2000 and spring 2001. Increased soil N at 20 cm ha-1 rate was associated with lower DM yield in 2000 than 2001 (10.5 vs 16.4 Mg ha-1). Averaged across spray seasons, postseason soil NO3 at 5-cm depth was significantly (P<0.05) greater in 20 cm ha-1 treatment than unfertilized controls (means of 39.6 vs 8.5 mg kg-1). Results indicate effluent N applied late in the growing season, particularly at high rates, is less likely to be utilized by bermudagrass due to dry summer conditions or declining growth during the fall.