Water Deficit Effects on Water Potential, Yield, and Water Use of Cowpeas¹

Abstract

Previous studies report conflicting results regarding the sensitivity of cowpeas to growth stage water deficits. Our 2‐year field study was designed to monitor the effects of water deficit imposed at three growth stages on the yield and water use of cowpeas (Vigna ungiculata (L.) Walp.). Six irrigation treatments were used to impose the water deficit including a well watered control treatment (WWW) and five deficit treatments (DWW, WDW, WWD, DWD, WDD). Cowpeas were grown on a sandy loam soil (coarse‐loamy, mixed thermic Haplic Durixeralf) on the experimental farm in Riverside, California. The pre‐dawn leaf water potential, as measured by the pressure bomb technique, was a better indicator of crop water stress than was the midday leaf water potential. The pre‐dawn leaf water potential at any growth stage progressively decreased with time following cessation of irrigation, but completely recovered after soil water storage was recharged by irrigation or rain. The most sensitive growth stages to drought were flowering and podfilling, with yield reduction from 35 to 69% depending on the timing and length of the drought treatment. A soil water deficit during the vegetative stage had the least effect on crop yield. This, coupled with decreased evaporation, resulted in a water‐use efficiency which was greater than that of the control treatment, which was adequately watered throughout the season. The water‐use efficiencies of the other stage deficit treatments were decreased below that of the control because of large decreases in crop yield. Seed yield of cowpeas was found to be linearly related to an integrated water stress indicator based on the predawn measurement of leaf water potential. We found that the relative dry matter yield was linearly related to crop transpiration as determined by the difference between a water balance measurement of ET and modeled evaporation (T = ET meas. ‐ Emodeled).

Simulation of growth and development of irrigated cowpea in Piauí State by CROPGRO model

“…Thus, in 1998 the flowering time (about 43 days) of cowpea occurred during a period of high air temperatures (around 35 o C) (Figure 1), that contributed to reduce both observed and simulated grain yields by 12 and 19%, respectively. This was also noted by other authors (Roberts et al, 1978;Summerfield et al, 1978;Doto & Whittington, 1981;Shouse et al, 1981;Sivakumar et al, 1996;Craufurd et al, 1998).…”

Componentes de produção, produtividade e eficiência da irrigação do feijão-caupi no cerrado de Roraima

“…Para os efeitos observados com os cultivares BRS Guariba e BRS Pajeú verifica-se semelhança com a observação feita por Shouse et al (1981) os quais afirmam haver uma relação fonte dreno refletida por este componente de produção quando, no momento em que a massa de cem grãos é reduzida, indica que está ocorrendo limitação da produção na fonte. Este fato pode ocorrer em virtude do aumento no número de vagens, como no caso de tratamentos adequadamente irrigados ou pelo efeito do estresse hídrico sobre a fotossíntese ou, ainda, translocação de fotoassimilados em que, neste caso e segundo Costa et al (1997), o número de vagens por planta é inversamente proporcional à massa de cem grãos refletindo em uma compensação para limitações de tamanho do dreno, apesar do cultivar BRS Novaera se tenha mostrado totalmente contrário a esta observação apresentando o maior número de vagens por planta e, em contrapartida, maior massa de cem grãos.…”

Genetic Variability, Performance and Yield Potentials of Ten Varieties of Cowpea (Vigna unguiculata (L) Walp) under Drought Stress

“…The water stress effect showed small effect on relative water content, pod length, 100-seed weight, number of days to first flowering and number of days to first ripe pod, this was in agreement with Silva, 1978, who reported that seeds/pod and 100-seed weights were not significantly affected by either the water or the nitrogen fertilizer treatments. Babalola (1980) and Shouse et al (1980) observed similar effects during different phases of the crop's phenological cycle. Labanauskas et al (1981) reported that water deficiency during flowering and pod filling reduced productivity by 44% and 29%, respectively, but were not significantly affected by water stressed during vegetative period.…”

“…Yield increase in crops is a major objective of breeders; hence selecting for best genotypes in an environment where water stress is the most important factor limiting crop production. Cowpea suffer drought stress as a result of erratic rainfall due to climate change resulting in yield loss of up to 35-69% (Shouse et al, 1980;Fatokun et al, 2012). In general new cultivars are traditionally produced by plant breeders selecting directly for yield or yield components in specific environment.…”