INFLUENCE OF CROP WATER ENVIRONMENT AND DRY MATTER ACCUMULATION ON GRAIN YIELD OF NO-TILL WINTER WHEAT
The influence of crop water environment on the productivity of no-till winter wheat (Triticum aestivum L. ’Norstar’) was observed for 17 site-years of trials in Saskatchewan between 1984 and 1986. Growing season precipitation (P) averaged 212 mm (approximately 120% of average) and pan evaporation (E) averaged 749 mm for these trials. Precipitation was approximately evenly distributed across the growing season while E increased from a low of 6.5 mm d−1 in early May to a high of 8.3 mm d−1 immediately after anthesis. Consequently, water stress was highest after anthesis. Total evapotranspiration (ET) (soil water use to 130 cm plus growing season P) ranged from 171 to 364 mm and approximately 20% of the ET was derived from soil water reserves. The average ratio of ET before and after anthesis was 1:7:1 and in many instances water utilized after anthesis was almost exclusively derived from intermittent rainfall events. Several yield-water models were fit to the data in order to establish a relationship between the crop water environment and grain yield. Yields ranged from 1316 to 5003 kg ha−1 and were most closely associated with the water environment (soil water, E and P) during the time from stem elongation to anthesis (r2 = 0.71). Water use efficiency, expressed as kg ha−1 grain yield divided by ET, ranged from 6.3 to 18.8 kg ha−1 mm−1 and was positively correlated with spikes m−2 (r = 0.59*), kernel weight (r = 0.73**), dry matter at anthesis (r = 0.84**), and negatively correlated with E during the 30 days prior to anthesis (r = 0.75**). Both dry matter at anthesis and dry matter at maturity were linearly correlated with grain yield (r = 0.85** and 0.92**, respectively). Both observations suggested that high grain yields required high dry matter yields.Key words: Wheat (winter), precipitation, evaporation, soil water, water use efficiency, models