Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: June 11, 2001
Publication Date: N/A
Technical Abstract: Two snap bean cultivars, Strike and Carlos (Phaseolus vulgaris, L.), were planted into a Hebbronville sandy loam soil on 22 February and on 29 September 2000, and grown under 0, 30, and 70% of ambient daily light (shade) throughout the 65-day growing seasons. Fall cumulative light was about 60% that of the spring planting, and fall mean daily temperatures were 1 to 2 C lower. In both spring and fall, the reduced yield response was linear with respect to increased shading, although first harvest and final yields were not affected by a 30% incident light reduction. Light reduction had little effect on pod sieve size distribution, but did increase pod dry matter. Plant biomass was reduced by shading as was leaf greenness, but leaf area and chlorophyll content (dry wt. basis), as well as the incidence of powdery mildew late in the season, was increased by shading. Leaf, air, and soil (at 10 cm) temperatures were measurably reduced by increased shading in the spring, but not the fall planting. Leaf transpiration and stomatal conductance generally increased with shading, and were further reduced by lower ambient canopy temperatures. Pod yield, leaf chlorophyll content, and rhizobium nodulation were higher in the fall planting, but pod set was more concentrated in the spring planting. Pod mineral nutrients varied between cultivars, but generally were not affected by light intensity as were leaf nutrients.