|LANG, DAVID - Mississippi State University|
|OLDHAM, J. - Mississippi State University|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2016
Publication Date: 3/9/2017
Citation: Read, J.J., Adeli, A., Lang, D.J., Oldham, J.L. 2017. Nutritive value and nutrient uptake of summer-active and summer-dormant tall fescue under different broiler litter rates. Agronomy Journal. 109:473-482. 10.2134/agronj2016.08.0445.
Interpretive Summary: Using broiler litter (a mixture of manure, wasted feed and bedding material) as fertilizer on the farm requires knowledge of rates that can result in yields of biomass and nutrients comparable to inorganic fertilizer with N, P, and K, as well as soil testing to ensure balanced plant nutrition is provided. Tall fescue is the primary forage base for approximately 9 million beef cows in the east-central and southeastern United States. It produces high-quality hay early in the growing season, but does not grow during hot periods in midsummer; it can become semi-dormant in Mississippi most “hot and dry” years. Tall fescues that actively grow or are semi-dormant during summer are referred to as “Continental” ecotypes and include the cultivars Kentucky 31 and Jesup. Tall fescues that avoid summer drought and/or heat stress by invoking summer-dormancy, are referred to as “Mediterranean” ecotypes and include the cultivar Flecha. The summer dormancy trait will help plant persistence of tall fescue in warm, dry climates. But does this trait also reduce total forage yield, as compared with summer-active tall fescue? To answer this question, a three-year study was established in 2005 in northeast Mississippi on a soil mapped as Houston clay with no litter history. Objective was to determine broiler litter effects on Kentucky 31, Jesup, and Flecha tall fescue forage yield and nutritive value, as compared with inorganic NPK fertilizer, and associated changes in soil nutrients. Cultivar, year and cultivar x year interaction affected forage yield, which increased linearly with increasing rates of litter. Based on forage digestibility comparable to inorganic fertilizer, tall fescue nutritive value would not be substantially reduced when broiler litter is the sole nutrient source. Averaged across the early- and mid-season harvests, summer-dormant tall fescue had the greatest forage yield, the least crude protein (a key component in determining nutritive value in ruminants) and similar N and P uptake, as compared with summer-active tall fescue. Applying 9.0 Mg litter ha-1 appeared to be the best compromise for high forage yield and quality, but elevated soil P, Cu and Zn levels as compared to either inorganic fertilizer or 4.5 Mg litter ha-1 treatment. Summer-dormant tall fescue appeared to offer an early-season productivity benefit and annual nutrient uptake comparable to summer-active tall fescue. This knowledge is useful in developing an annual nutrient management plan for broiler litter applications in northeast Mississippi.
Technical Abstract: Tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] responds to broiler litter fertilization; however, data concerning the summer dormancy trait are not available. This 3-yr study (2006-2008) determined the nutrient value of broiler litter compared with commercial fertilizer (CF) in tall fescue production and associated changes in soil nutrients as affected by degree of summer dormancy. Litter rates of 0, 4.5, 9.0, 13.4, and 17.9 Mg ha-1 yr-1 (as-is moisture basis) and CF (2:1:2 ratio of N:P2O5:K2O, respectively) were split-applied in autumn and spring and forage was harvested at early-, mid- and late-season. Averaged across 2006 and 2007, forage digestibility exceeded 790 and 710 g kg-1 at early- and mid-season harvests, respectively, indicating high nutritive value for all treatments. At these times, summer-dormant ‘Flecha’ had the greatest dry matter (DM) yield, the least crude protein (CP) and similar N and P uptake, as compared with summer-active ‘Jesup’ and ‘Kentucky 31’ tall fescue. Phosphorus uptake increased linearly from 2 to 19 kg ha-1 across litter rates and was approximately 17 kg ha-1 with CF. Per Mg of applied broiler litter, ranking of slopes for cumulative DM and nutrient uptake in 2008 was Kentucky 31 > Flecha > Jesup, and slope for CP was least in Flecha. Soil test P ( 0- to 15-cm depth) in autumn 2008 was least with CF and 0 Mg litter ha-1 (33.5 mg kg-1), increased significantly with 4.5 and 9.0 Mg litter ha-1 (57.5 mg kg-1), and greatest with 17.9 Mg litter ha-1 (130 mg kg-1). Applying 9.0 Mg litter ha-1 appeared to be the optimum level to achieve high nutritive value and DM yield and avoid excessive soil P, Cu, and Zn amounts. Summer-dormant Flecha appeared to offer an early-season productivity benefit and annual nutrient uptake comparable to summer-active tall fescue.