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Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 9/30/2010 Publication Date: 2/1/2011 Citation: Zhang, X.J. 2011. Grazing initiation timing affects net return to dual-purpose wheat systems. Transactions of the ASABE. 27(1):51-62. Interpretive Summary: There is limited knowledge about the effects of grazing initiation timing on net returns to dual-purpose wheat systems. The goals of this work were to simulate the effect of grazing initiation dates on net returns to a wheat– cattle system, and to determine economically optimal dates of grazing initiation for selected grazing scenarios. A computer software mimicking wheat and steer growth was used to simulate the dual systems in north-central Oklahoma for six to eight grazing initiation dates (ranging from 10 October to 30 January), six stocking rates (0.5 to 3 head/ha), four planting dates (1 September to 1 October), three climate scenarios (dry, average, and wet), and an initial wet soil. Simulated beef weight gains and wheat yields were used to compute net returns using a budget calculator for the 1999 (favorable to grazing) and 2005 (neutral) markets. Based on this work, grazing should be initiated as soon as wheat plants are anchored or top dry biomass reaches approximately 1120 kg/ha, regardless of planting dates and climates. Pivotal dates pertaining to grazing initiation timing could be identified for most planting dates and climates. Generally, higher stocking rates of up to 3 head/ha were preferred when grazing began before pivotal dates (early), whereas a lower stocking rate of 0.5 was desired afterwards (for late grazing). For risk averters, lower stocking rates should be preferred option as for as grazing initiation is concerned. These results should be useful to extension professionals and producers for choosing grazing initiation date that has potential to maximize net returns. Technical Abstract: Limited experimental data are available to allow direct evaluation of the effects of grazing initiation timing on net returns to dual-purpose wheat systems. The objectives were to simulate the effect of grazing initiation dates on net returns to a wheat (Triticum aestivum L.) – cattle (Bos taurus) enterprise, and to determine economically optimal dates of grazing initiation for selected grazing scenarios. A wheat grazing model was used to simulate the dual systems in north-central Oklahoma for six to eight grazing initiation dates (ranging from 10 October to 30 January), six stocking rates (0.5 to 3 head/ha), four planting dates (1 September to 1 October), three climate scenarios (dry, average, and wet), and an initial wet soil with 75% plant available water. Net returns were further estimated using an enterprise budget approach for the 1999 (favorable to grazing) and 2005 (neutral) markets. For the wheat-cattle production scheme assumed in this work, grazing should be initiated as soon as wheat plants are anchored or top dry biomass reaches approximately 1120 kg/ha, regardless of planting dates and climates. Pivotal points or dates pertaining to grazing initiation timing could be identified for most planting dates and climates. Generally, higher stocking rates (SR) of up to 3 head/ha were preferred when grazing began before the pivotal points, whereas a lower SR of 0.5 was desired afterwards. Uncertainty in net return resulting from grazing timing decreased as SR decreased, suggesting lower SR be preferred options for risk averters. |
