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Shade Effects on Growth, Partitioning, and Yield Components of Peanuts¹

Peanut (Arachis hypogaea L.) may have one or more periods during development when low solar radiation intensity is particularly detrimental to high yield. The present studies were conducted in the field to determine the effect of shade on vegetative growth, partitioning of assimilates and yield components of peanut. In a 2-year experiment, 75% shade was applied for 7, 10, 14, or 21 day periods during flowering, pegging, podding, and maturing phases. The objective was to determine which reproductive phase was most sensitive to low solar radiation intensity. Flower number, peg development, pod formation, and dry matter accumulation and partitioning were measured at regular sampling intervals. Shade during the peak flowering period reduced the number of flowers per plant and inhibited peg formation. Shade during the pegging and podding phases reduced total peg and pod number and reduced pod dry weight. Shade during the maturing phase reduced seed fill as shown by reduced shelling percentage and a lower number of fruits achieving mature pod status. On the average, over all stages, 75% reduction of light intensity decreased the growth rate of vegetative parts by 85%, the reproductive growth rate by 67%, and the total biomass growth rate by 67%. Shade prior to podding increased partitioning to vegetative growth, by 20%, whereas shade during the podding phase (83 to 104 days) increased dry matter partitioning to pods by 127%. Seventy-five percent reduction in solar radiation intensity reduced yield of Florunner peanuts significantly only when the duration was for 14 or 21 day periods. Podding was the phase in which yield was most sensitive to shade with a 30% reduction in fruit yield from shade during 83 to 104 days of age. The maturing phase was next in sensitivity to shade, which decreased yield primarily by decreasing seed fill in existing fruits. Twenty-one days of shade at flowering did not reduce final fruit yield, since the plants had time to recover from the loss of active flowers and subsequently bear flowers and produce a normal pod load.

Key Words: Arachis hypogaea • Ground-nut • Shading • Flower number • Pegging • Podding • Maturing • Pod-filling • Pod number • Crop growth rate

² Former graduate assistant, Dep. of Agronomy, Univ. of Florida, now assistant agronomist, Irrigated Agriculture Research and Extension Center, Washington State University; professor, associate professor, and professor, Dep. of Agronomy, Univ. of Florida, respectively.

Received for publication February 17, 1983.