Abstract
Winter wheat (Triticum aestivum L.) productivity is frequently limited by water availability and degraded by wind erosion. Managers of harvest operations must balance soil and water‐conservation benefits of maintaining sufficient stubble height with the risk of losing grain yield due to unharvested spikes below the combine cutting height. This study calculated the relationship between expected harvest losses and conservation of soil and water at various combine cutting heights. Mature wheat spike height frequency distributions for 5 yr were collected for different tillage and residue‐cover levels. Wind‐velocity profiles were measured for different stem frequencies and heights at three sites with harvested wheat stubble. Potential evaporation of water was calculated by PENFLUX, a Penman‐type energy balance model. Potential soil loss was computed from the relative friction velocity (RFV). Stem heights were generally normally distributed, regardless of year or treatment. Quantifying RFVs at the soil surface and relative evaporation rates showed that combine cutting heights <0.1 m offered little protection from erosive winds for sparse stands with <280 stems m−2. Higher cutting heights of 0.3 or 0.5 m increased protection, especially for sparse stands, but the relative benefits of increasing stem frequencies declined with higher cutting heights. Under normal sowing rates and conditions, harvesting wheat with a cutting‐type header at two‐thirds of its height will give 80% of the maximum soil and water conservation protection. Harvesting with a stripper‐header combine attachment might be a potential new technology to further maximize soil and water conservation while minimizing harvest losses.
Published Version
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