Optimizing wheat harvest cutting height for harvest efficiency and soil and water conservation

Winter wheat (Triticum aestivum L.) productivity is frequently Limited bu w ater availability and degraded by wind erosion, Managers of harvest operati ons must balance soil and water-conservation benefits of maintaining suffic ient stubble height with the risk of Losing grain yield due to unharvested spikes below the combine cutting height. This study calculated the relation ship between expected harvest losses and conservation of soil and water at various combine cutting heights. Mature wheat spike height frequency distri butions for 5 yr were collected for different tillage and residue-cover lev els. Wind-velocity profiles were measured for different stem frequencies an d heights at three sites with harvested wheat stubble. Potential evaporatio n of water was calculated by PENFLUX, a Penman-type energy balance model, P otential soil loss was computed from the relative friction velocity (RFV), Stem heights were generally normally distributed, regardless of year or tre atment. 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 heigh ts of 0.3 or 0.5 m increased protection, especially for sparse stands, but the relative benefits of increasing stem frequencies declined with higher c utting heights. Under normal sowing rates and conditions, harvesting wheat with a cutting-type header at two-thirds of its height Rill 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 m aximize soil and water conservation while minimizing harvest losses.