Submitted to: Proceedings of the Arkansas Water Research Center Conference
Publication Type: Abstract Only
Publication Acceptance Date: 4/10/2006
Publication Date: 4/18/2006
Citation: Pote, D.H., Way, T.R., Kingery, W.L., Aiken, G.E., Sistani, K.R., Han, F.X., Moore Jr, P.A. 2006. [CD-ROM] Incorporating poultry litter into perennial grassland to improve water quality. Proceedings of the Arkansas Water Research Center Conference.
Technical Abstract: Poultry litter provides a rich source of nutrients for perennial grasses, and it has greatly increased forage yields on land once considered marginal for agricultural production. However, the usual practice of spreading litter on the surface of hay meadows and pastures leaves it completely exposed to the atmosphere. This has raised serious water-quality concerns and may be limiting the potential benefits that poultry litter can provide because it allows surface runoff to transport dissolved metals and nutrients from the litter into streams and lakes, and much of the N is lost through ammonia volatilization before it can enter the soil. Producers need the option of better application methods that decrease volatilization and runoff losses from litter while making the valuable nutrients more available to perennial forages. For tilled cropping systems, incorporating litter into the soil has proven to be a successful technique for decreasing nutrient losses while enhancing plant growth, but existing farm implements can not be used to incorporate dry poultry litter into the soil of perennial pasture without seriously damaging the forage crop. Therefore, in our initial study of incorporating poultry litter into the root zone of perennial forages, we used a knifing technique to manually place dry litter below the surface of established grassland with minimal disturbance of the soil structure, forage crop, and thatch. Our primary objective was to determine effects of litter incorporation on water, soil, and nutrient losses in runoff, but we also investigated effects on the forage crop. Field plots were constructed on a silt loam soil with well-established bermudagrass (Cynodon dactylon L.) and mixed grass forage. Each plot had 8-10% slopes, borders to isolate runoff, and a downslope trough with sampling pit for runoff collection. Broiler litter was applied (5.6 Mg ha-1) by one of three methods: surface-applied, incorporated, or surface-applied on soil-aeration cuts. There were six treatment replications and three controls (no litter). Runoff samples from natural and simulated rainstorms showed that nutrient concentrations and mass losses from incorporated litter were significantly lower (generally 80-95% less) than in runoff from surface-applied litter. By the second year of treatment, litter-incorporated soils had greater rain infiltration rates, water-holding capacities, and sediment retention than soils receiving surface-applied litter. Litter incorporation also tended to increase forage yield and quality. In follow-up work to mechanize the knifing technique, we developed and tested a single-shank, tractor-drawn incorporator that applied dry, pre-treated (ground) poultry litter under the surface of perennial pasture. Field plots were marked with corner pins in a hillside pasture (bermuda and mixed grass forage) with 8-10% slopes on a silt loam soil. Early in the growing season, broiler litter from a commercial poultry house was applied to each plot (except 3 control plots) at a rate of 6.7 Mg/ha (dry weight) using one of two application methods: surface-applied manually or incorporated using the tractor-drawn implement, with 3 replications of each treatment. For surface applications, the litter was scattered uniformly over the plot surface. The mechanical incorporator sliced the soil surface (across the slope) to a depth of 8 cm, poured litter into the 5-cm-wide cut, and covered it with soil. This was repeated at 30-cm intervals up the slope to provide the full litter application for each incorporation plot. After litter applications were complete, each plot (2 X 2 m) was fitted with aluminum borders and a downslope trough with sampling pit for runoff collection. Two days after litter was applied, simulated rainfall (5 cm/h) was used to produce 20 minutes of runoff from each plot. Results showed that this mechan