Submitted to: Journal of Environmental Quality
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/25/2009
Publication Date: 7/30/2009
Citation: Burns, J.C., Stone, K.C., Hunt, P.G., Vanotti, M.B., Cantrell, K.B., Fisher, D.S. 2009. Intake and digestibility of ‘Coastal’ bermudagrass hay from treated swine waste using subsurface drip irrigation. Journal of Environmental Quality. 38:1749-1756. Interpretive Summary: Swine lagoons in the Southeast are being viewed as a threat to the environment and are no longer an option for further expansion. A new technology, termed environmentally superior technology (EST), that processes raw swine waste directly out of the confinement barn has been developed and the use of the processed effluent needed evaluation. This study showed that the processed effluent, with reduced P and N concentrations, could be used in a subsurface drip irrigation system for the production of bermudagrass that was readily consumed by ruminants. Although sheep consumed the non-irrigated control fertilized with commercial N better than effluent irrigated treatments (1.94 vs. 1.77 kg/100 kg body weight) and the irrigated control better than the effluent treatments (1.81 vs. 1.71 kg/100 kg) the differences were rather small and in the latter case probably of little biological importance. This system worked well as the odor was reduced and the N loss from volatilization, both which occur with an overhead irrigation system was essentially avoided. This EST may be the future approach in handling waste from confined animals and the animal response data obtained from feeding bermudagrass hay from the treated effluent is positive.
Technical Abstract: Waste handling systems for confined swine production in the upper South depend mainly on anaerobic lagoons and application of the waste effluent to cropland. This study evaluates the quality of ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.] hay irrigated with effluent generated from a raw swine waste treatment system which removed excess N and P and the effluent delivered by subsurface drip irrigation (SDI). Eight treatments, consisting of commercial N fertilizer or effluent each irrigated at two (75 and 100% of estimated evapotranspiration) irrigation rates and two lateral spacings (0.6 and 1.2 m), were compared to a control of commercial N fertilizer without irrigation. Three harvests were taken each of 2 yr and five of the six evaluated for dry matter intake (DMI) and dry matter digestion (DMD) using wether sheep (30 to 45 kg). Greatest DMI per unit body weight (BW) occurred for fertilized, non-irrigated hay compared with the irrigated treatments (1.94 vs. 1.77 kg 100-1 kg). Within the irrigated treatments, DMI was more for the hay fertilized with commercial N compared with effluent (1.81 vs. 1.71 kg 100-1 kg). Hay from the 75% rate had DMI similar to the non-irrigated treatments (mean=1.87 kg 100-1 kg), whereas DMI from the 100% rate was reduced (1.94 vs. 1.72 kg 100-1 kg). Hay from the 75% rate had more DMD than at the 100% rate (527 vs. 508 g kg-1). The SDI system functioned well for the production of bermudagrass and lateral spacing did not alter forage quality.