Effects of stocking and nitrogen fertilization rates on steers grazing dallisgrass-dominated pasture.

To compare the performance of steer calves managed under different stocking rates (SR, 3.7, 6.2,8.6, and 11.1 steers/ha for 140 d, χ11) and N fertilization rates (112, 224, and 336 kg of N/ha, χ12) in May 1996, 1997, and 1998, 72 steer calves (BW = 231 ± 2.5 kg) were assigned randomly to one of 12 0.81-hadallisgrass (51%)/common bermudagrass (32%) pastures. One-third of the fertilizer was applied in the form of ammonium nitrate in May, June, and August to achieve the prescribed totals. Treatments were separated using a polynomial regression equation: &#x03B3_i = β₀% + β₁χ₁₁ + β₂χ₁₂ + β₁₁χ²₁₁ + β₁₂χ²₁₂ + β₁₂χ_i1χ_i2 + ϵI, with years as replicates. Within the range of the data, ADG and BW gain per steer were greatest at a stocking rate of 3.7 steers/ha and 336 kg/ha of N. Body weight gain per hectare peaked at 701 kg when cattle were stocked at 8.9 steers/ha and the pasture was fertilized with 336 kg/ha of N. The least cost of production was at a stocking rate of 3.7 steers/ha, with 112 kg/ha of fertilizer N applied, and the greatest cost of production was at a stocking rate of 11.1 steers/ha with 336 kg/ha of fertilizer N applied. Fertilization at 336 kg/ha of N produced the most profitable stocking rate at 7.3 steers/ha and re- turned $355.64. The optimal stocking rate for net return was 79, 81, and 82% of that for maximum BW gain per hectare for 112,224, and 336 kg/ha of N, respectively. Under the assumptions made in the financial analysis, these data show that the economically optimal carrying capacity of similar pastures can be increased with N fertilizer up to at least 336 kg/ha annually. [ABSTRACT FROM AUTHOR]