Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 11, 2002
Publication Date: June 1, 2002
Interpretive Summary: Poultry manure should be applied to crops that are rapidly growing to maximize uptake of nutrients that might leave the field where they are applied and negatively impact water quality. We conducted this study to determine when was the best time to apply poultry manure to bermudagrass, a tropical forage grass grown throughout the Southeast. We found that for both a low and high rate, grass yield and nutrient uptake were greatest when manure was applied in May or June rather than April. In April, temperatures are not optimum for bermudagrass growth. There was no benefit to splitting the quantity of manure applied at one time into two, smaller applications. At the higher application rate, only 17 to 23% of the phosphorus applied in the manure was removed by the bermudagrass.
Technical Abstract: Broiler litter application should be timed so that crop nutrient uptake is maximized and potential loss of nutrients to the environment is minimized. Our objective was to determine the influence of rate and date of litter application on yield and nutreint uptake of bermudagrass (Cynodon dactylon (L.)Pers.). Litter was applied at 9 and 18 Mg ha-1 to `Alicia' hybrid bermudagrass as a single application in April, May, and June, or was split-applied (equal division of the total) at the same rates in April and June, May and July, and June and August. The Savannah fine sandy loam (fine-loamy, siliceous, semiactive, thermic Typic Fragiudult) had a high P level (351 mg kg-1) in the upper 10cm due to previous litter application. Increasing application rate from 9 to 18 Mg ha-1 increased annual bermudagrass yield and P uptake when litter was applied in April (12.8 to 15.6 Mg DM ha-1; 43.3 to 49.9 kg P ha-1) or June (14.3 to 16.9 Mg DM ha-1; 45.4 to 51.3 kg P ha-1), but not in May (mean of 15.0 Mg DM ha-1 and 48.4 kg P ha-1). Delaying application of 9 Mg ha-1 until May or 18 Mg ha-1 until June increased annual yield and N,K, and Cu uptake compared to applications in April. Phosphorus uptake was generally unaffected by date of applicaton, due to high existing soil P levels or to the small quantity of P required by the grass relative to the amount applied in the litter. Despite aggressive harvest management (30-d harvest interval), efficiency of P uptake ranged from 0.31 to 0.51 at the 9 Mg ha-1 rate, and from 0.17 to 0.23 at the 18 Mg ha-1 rate. Because recovery of applied P was so low, it is important that producers apply broiler litter to bermudagrass after growth has begun to maximize DM and nutrient yield.