Plant and soil effects from the surface application of poultry litter to unmanaged pasture
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The poultry industry, a vital economic force in Virginia, must dispose of vast amounts of waste, mainly litter (PL) , generated during production processes. This study was conducted to investigate the shortterm effects of various rates of PL application, i.e., cumulative 2-year totals of 9.8, 19.5, 29.3, 39.0, and 48.8 mt ha-1, to unimproved pasture. Dry matter yield, N recovery and use efficiency, P recovery and use efficiency, and changes in botanical composition were measured on a mixed species, tall fescue (Festuca arundinacea) and bluegrass (Poa pratensis) pasture. Additionally. the accumulation and movement of P was measured in a Starr clay loam (fme-Ioamy mixed thermic Fluventic Dystrochrepts) by the Mehlich 3 (M3) and Bray 1 (Bl) soil tests. Dry matter yields increased curvilinearly with rate of PL application. This yield increase was attributed to correction of N deficiency in pasture by the PL application. Lower levels of PL increased forage yields in 1992 compared with 1991, due to residual effect of unmineralized N from PL applied in 1991. The PL application rate of 11.4 mt ha-1 in 1991, followed by 8.1 mt ha-1 in 1992 was the most environmentally and economically recommendable rate when compared with inorganic N and P recommended fertilizer rates. Forage yields on this treatment were 21.5 mt ha-1 versus 21. 7 mt ha-1 for the inorganic N and P fertilizer treatment. All rates of applied PL increased the percentage of tall fescue (from approximately 50 percent to > 80 percent) and decreased the percentage of bluegrass in this mixed pasture. Phosphorus from both PL and inorganic sources accumulated in the zone of application. In 1992, the highest rates of PL application had increased M3-extractable P levels by 20 fold over the control (192 mg P kg versus 11 mg P kg-1) and caused movement of P into the 10 to 15 cm soil depth. Levels of P extracted by the M3 and Bl soil tests were highly correlated for both years (r2 = 0.96 in 1991 and r2 = 0.99 in 1992) but the M3 extracted substantially more P from the surface 0 to 5 cm depth (21 percent in 1991 and 23 percent 1992) while the Bl soil test extracted more P from the 5 to 30 cm soil depth (50 to 66 percent more in 1991 and 20 to 57 percent in 1992). Differences in total acidity and F concentrations account for differences of P extracted by the two procedures. Poultry litter is a suitable source of fertilizer for pasture renovation and production in the Piedmont Region of Virginia.
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