Monday, November 13, 2006

Wheat productivity and water use in intensive cropping systems under drought.

Robert Aiken, K-State NWREC, 105 Experiment Farm Rd., Colby, KS 67701

Drought conditions may limit the water use benefits of intensive (e.g., annual) cropping systems in semi-arid regions, relative to wheat-fallow systems. The research objective was to determine effects of cropping intensity and sequence on crop water use, canopy formation and productivity of grain and above-ground biomass. Methods include water use by soil profile depletion plus precipitation, leaf area index at anthesis by radiation transmission, biomass and components of yield by sampling at physiological maturity. Year by sequence interactions preclude general conclusions of cropping intensity and sequence effects. Linear relationships were established among spring water use, canopy formation, above-ground biomass and grain productivity. Regression coefficients for grain yield threshold of 132 mm and response to spring water use of 14.4 kg ha-1 mm-1 are consistent with reported values. Prior knowledge of spring water use could support yield forecasts and selection of harvest alternatives.