INFLUENCE OF SOLAR RADIATION AND SOIL MOISTURE ON GROWTH AND YIELD OF CHINOOK WHEAT

The influence of solar radiation on the growth and yield of Chinook wheat was determined in a 5-year field shading study, and a 1-year, 3 × 3 shading × soil moisture lysimeter experiment.In the field, shading with saran mesh reduced solar radiation and wind but had little effect on air or soil temperature. In moist years shade maintained soil moisture at a higher level than no shade. Generally, mean leaf area ratio decreased and mean net assimilation rate and relative growth rate increased linearly with increases in the log of light intensity. There were interactions between shading × years (weather) relative to dry matter yield. The efficiency with which solar energy was used for grain production increased with shading. The effect of shading on crude protein and soluble sugars in grain was variable.In the lysimeter shading study, regression equations were used to relate several plant characters to shading and soil moisture (in the available range). Plant height, stem diameter, days to head, number of til...