Effects of Drought on Florunner Peanuts1

Abstract

AbstractDroughty conditions are implicated in causing low yields, poor grades and germination, and an increased incidence of aflatoxin in the peanut (Arachis hypogaea L.). However, very little is known as to when in the growth cycle drought is most critical. Effects of five drought treatments on peanut leaf diffusive resistance, yield, and quality characteristics were studied on rainfall‐protected plots of Tifton loamy sand, a member of the fine, loamy, siliceous, Thermic Plinthic Paleudults. Early, middle, and late drought periods of short duration (35 days) and extended early and midseason droughts (70 days) were imposed by withholding irrigation. Yield, percent sound mature kernels (SMK), germination, leaf‐water potential, and leaf diffusion resistances were measured. Under droughty conditions, leaf‐water potential was lowest during midseason when evaporative demand was greatest. Leaf diffusion resistances, however, in creased with lateness and severeness of drought, reflecting leaf age and plant‐water stress. Leaf‐water potentials of −30 bars were recorded for several treatments during midseason, and values as low as −40 bars were recorded for the 35‐day midseason drought. Although the leaf‐water potentials of control plants decreased as the season progressed, they never became lower than −12 bars. In both stressed and nonstressed plants the diffusion resistances were frequently less on the upper than on the lower surfaces of leaves. Much of the plant‐water stress that developed during drought was relieved the day after irrigation and leaf diffusion resistances also returned to near normal. Vine weight was not decreased by any 35‐day drought, but was significantly reduced by 70‐day droughts.In general, drought progressively decreased yields as duration and lateness of occurrence in the season increased. The 70‐day extended early season drought caused the greatest reduction is SMK. The late season 35‐day and extended midseason 70‐day droughts lowered subsequent germination 5 and 9% respectively. These studies validate the importance of full‐season irrigation for peanuts in the Southeast. When full‐season irrigation may not be possible because of demands on the system, scheduling irrigation the latter part of the season appears next in importance.