Estimates of additional Maize (Zea mays) yields required to offset costs of tree-windbreaks in Midwestern USA

摘要

Field windbreaks can increase crop yield within a protected zone. However, they also take land out of crop production and compete with adjacent crops. Although the beneficial aspects are generally recognized, the question arises whether the windbreak will increase crop revenue enough to offset costs over time. Achieving additional yields to offset windbreak costs might be a sufficient incentive for a producer to plant a windbreak. Additional maize (Zea mays) yields necessary to break even with costs are calculated for four typical Midwestern USA field windbreaks: poplar (Populus spp.), mixed tree/shrubs (Populus spp., Acer saccharinum L./Physocarpus spp., Viburnum spp., Cornus spp.), and two and four-row spruce (Picea spp.) windbreaks. Five lifespans, two management and two cost scenarios, and three protected zone widths to account for changing sheltering effects are evaluated. Greatest additional yields are for a 4-row spruce windbreak with intensive management at high cost and a 10-year lifespan: 15.38 Mg ha–1 yr–1 within 6H, 7.69 Mg ha–1 yr–1 within 12H and 6.15 Mg ha–1 yr–1 within 15H. If a 50-year lifespan is implemented, the additional yields are about 11% of those in 10-year lifespan. Smallest additional yields are for a mixed tree/shrubs windbreak with extensive management at low cost and a 50-year lifespan: 0.56 Mg ha–1 yr–1, 0.28 Mg ha–1 yr–1 and 0.22 Mg ha–1 yr–1, respectively. The mixed windbreak is likely to have actual maize yield increases comparable to the added maize yields required to break even as long as the lifespan is 30 years or longer with a minimum protected zone of 12H.