Farm machinery management and the impact of conservation tillage systems on soil erosion and the sustainability of wheat production in rainfed areas of northern Jordan

Scope and method of study. The selection of the proper machinery size and ownership costs of common farm machinery used for wheat production in Irbid/Jordan was studied. The penalty cost of planting wheat at times earlier or later than the optimum time "timeliness cost" in Irbid was also determined. A crop yield-predicting model, CERES-Wheat was used to predict wheat yield at different planting dates in Irbid. The problem of soil erosion and its effect on wheat production in Irbid area was also studied. The Environmental Policy Integrated Climate model (EPIC) was used to simulate the wheat yield and the rate of soil erosion on the Red Mediterranean soils of Irbid. The amount of soil erosion and its impact on wheat yield was simulated under different tillage systems for the period of 100 years. The conventional and conservation tillage systems were used for a wheat fallow crop rotation in the model. The Net Present Value (NPV) method was used to measure the costs and benefits of each system. The system with the highest NPV could be selected.;Findings and conclusions. The results of the CERES-Wheat model simulations were used in determining the timeliness cost. Timeliness cost was minimized by planting wheat during the mid of November. Planting one month earlier (October 15--20) led to the loss of 292 kg/ha of wheat (JD44), while planting one month later (December 20--25) caused the loss of 359 kg/ha of wheat (JD54). The results for machinery selection showed that a tractor size of 65 to 70 hp is sufficient to do the required field operations for planting a 200 ha field on time. The NPV analysis showed that for the long run it is more beneficial to the farmer to use the conventional tillage system for deep soils (1.5 m) with 10% discount rate, while it is more beneficial to use the conservation system for shallow soils (0.7 m) with a discount rate of 5%.