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Impact of feedlot facility design, diet and cattle type on manure nutrient capture
Increased fertilizer prices have generated interest in capturing value through manure in integrated crop and cattle feeding systems. Manure nutrient analysis results for solid (n=689) and liquid (n=186) manure samples were collected over 4 yr to determine the impact of facility design (open lot, bed pack from confinement barn, stockpiled manure, pit under slatted floor or lagoon), cattle type (beef or dairy) and dietary energy value (grower or finisher) on manure nutrient concentrations. Manure nutrients were expressed as kg nitrogen (N), phosphate (P2O5) or potash (K2O)/T of as-is material (solid) or as kg of these nutrients/3785 L (liquid). A combined dataset (n = 483) was analyzed with projected annual cattle manure production values of 2.7 and 4.5 T/hd or 9463 L/hd, respectively, for open lot, bed pack or pit under slatted floor were estimated to compare effects of facility design on manure nutrient contributions per head space. Data were analyzed using the MIXED procedure of SAS, effects of year and month were determined to have no effect and were dropped from the model. Dietary energy value was not included in the analysis of the liquid data set because only finisher diets were represented. Nutrient concentration of liquid manure samples from indoor pits was greater (P < 0.05) than that from lagoons across all nutrients. Nitrogen concentration of liquid samples (kg/3785 L) was greater (P < 0.05; 16.42 vs. 13.0) for dairy type cattle, and P2O5 also tended to be greater (P < 0.10; 7.6 vs 6.3) for dairy type cattle. Nitrogen concentration in solid samples (kg/T) was not impacted by facility type (P > 0.10); however, P2O5 concentration was lower (P < 0.05) in bed packs (4.6) compared to open lots (5.5) and stockpiled manure (6.0). Concentrations of all nutrients in solid manure samples were greater (P < 0.05) for beef cattle as compared to dairy type cattle. Dietary energy value did not impact (P > 0.10) nutrient concentrations of solid manure samples. Estimated annual manure N yield (kg/hd) differed (P < 0.05) with feedlot design. Manure N yield (kg/hd/yr) was greatest for indoor pits (58.5), intermediate for bed packs (39.0) and least for open lots (24.0). Manure P2O5 yield (kg/hd) was greater (P<0.05) for bed pack (22.7) and indoor pit (24.9) facilities as compared to open lots (15.0). These results confirm that greater manure nutrients are captured by confinement feedlot facilities.
Keywords: manure nutrient, feedlot design, beef cattle