A bioeconomic analysis of site-specific management and delayed planting strategies for weed control

The potential economic and environmental benefits of two emerging tools for low input weed management are examined in this research. Site-specific weed management (SSM) prescribes herbicide treatment for only the portion of a field exposed to weed infestations, rather than the entire field. Delayed planting allows weeds to emerge prior to planting. Since these weeds are eliminated during pre-plant tillage operations, the potential for subsequent weed problems is greatly reduced. The potential benefits of these instruments are simulated using a variant of WEEDSIM, a dynamic bioeconomic weed management model. Differences in model performance under SSM and delayed planting strategies as compared to performance under standard practices impute value to these weed control tools. Simulations with the model were conducted within a deterministic framework. Simulated results suggest that patchiness in weed distributions is the most crucial factor justifying the use of SSM. Other factors such as weed populations and weed species mixes only play secondary roles. There is a substantial environmental gain from SSM practices under a considerably high degree of weed pressure and aggregation. However, the impact of such practices on profit is generally modest. For this reason, it is doubtful if farmers will be willing to adopt this strategy without some public support, particularly when cost and risk considerations are factored in. Outcomes from static simulation experiments for delayed planting strategy suggest that the practice can be a valuable instrument for optimizing net income and herbicide use, especially at high weed populations. The practice may lead to an effective control of pre-plant weeds through mechanical means to the extent that the use of pre-emergence herbicides is not required. Furthermore, the economic benefits of delayed planting strategies are not sensitive to hybrid varieties and rotational practices in the short run. In view of the desirable environmental attributes of these two strategies, their use deserves support. Cheap and affordable technology, cheap and easy access to information on weed population dynamics and crop yield-planting date relationships are means of enhancing the adoption of these environmentally-friendly practices.