Physical, chemical, and biological properties of simulated beef cattle bedded manure packs

Manure including bedding material can be a valuable fertilizer, yet numerous, poorly characterized, environmental factors control its quality. The objective was to determine whether moisture content (MC), nutrient value (ammonium nitrogen (NH₄-N), total nitrogen (TN), total phosphorus (TP), total potassium (TK)), short-term nitrification activity potential (NAP), and denitrification enzyme activity (DEA) of simulated beef bedded manure packs (BP) were affected by temperature (10°C or 40°C), bedding type (corn stover or soybean stubble), storage time (age 0-3, 3-6, and 6-9 week), or sample depth. Thirty-six lab-scale BP were constructed (n = 3 per treatment) and then monitored over a three-week period with fresh feces, urine, and bedding additions weekly. The 0-3, 3-6, and 6-9 week old BP were on average 8, 17, and 23 cm deep. All ages were sampled approximately 2 cm below the surface (top zones), 3-6 and 6-9 week old BP were sampled approximately 2 cm above the bottom (bottom zones), and 6-9 week old BP were sampled from the approximate middle. At 40°C, TN (17.7 g kg^-1) and DEA (0.95 mmol g_bedpack^-1 h^-1) were lower compared to TN (18.6 g kg^-1) and DEA (3.01 mmol g_bedpack^-1 h^-1) at 10°C. In contrast, NAP was higher at 40°C (1.67 vs. 0.76 nmol g_bedpack^-1 h^-1 at 10°C). At 40°C, TP and TK concentrations increased toward the bottom of the BP and were higher in these bottom zones (9.9 and 27.8 g kg^-1, respectively) than at 10°C (7.2 and 23.0 g kg^-1, respectively). At 10°C, NH₄-N and TK concentrations increased with lower depth by 27% and 14%, respectively. At 40°C, upper zones of 3-9 week old BP had lower MC (30% to 50%) than at 10°C (48% to 70%); however, for both storage temperatures, bottom zones had similar MC (73%) and increased toward the bottom of BP. Additional interactions among factors were measured. Overall, temperature affected all properties, while most variables differed with age and sample depth. The findings suggest that management decisions on removal frequencies become more decisive in summer months with respect to the fertilizer value and the volume needed for bedded manure storage, while decisions on bedding material seem to be important year round. Nutrient sampling from top to the bottom of the bedded manure is important to ensure the accuracy of nutrient estimates.