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; chi(I1)) and N fertilization rates (112, 224, and 336 kg of N/ha; chi(I2)) in May 1996, 1997, and 1998, 72 steer calves (BW = 231 +/- 2.5 kg) were assigned randomly to one of 12 0.81-ha dallisgrass (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: gammai = beta0 + beta1chi(I1) + beta2chi(I2) + beta(11)chi2(I1) + beta(12)chi2(I2) + beta(12)chi(i1)chi(i2) + epsilonI, 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 returned 355.64 dollars. 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.
Gunter
S A
SA
Southwest Research and Extension Center, Division of Agriculture, University of Arkansas, Hope, 71801, USA. sgunter@uaex.edu
Beck
P A
PA
Hutchison
S
S
Phillips
J M
JM
D000704:Analysis of Variance; D000822:Animal Husbandry / Q000191:economics / Q000379:methods*; D000818:Animals; D002417:Cattle / Q000254:growth & development*; D005308:Fertilizers; D016018:Least-Squares Analysis; D008297:Male; D009584:Nitrogen / Q000502:physiology; D031781:Paspalum; D011156:Population Density; D011891:Rain; D011897:Random Allocation; D012621:Seasons; D013696:Temperature; D015430:Weight Gain / Q000502:physiology*
D005308:Fertilizers; D009584:Nitrogen