Grain yield and water consumption of ethephon-treated corn under different irrigation regimes

Ethephon (2-chloroethyl phosphonic acid) has been widely studied under field conditions as a growth regulator to enhance yield in corn (Zea mays L.) by controlling lodging. However, few studies have examined the interaction between ethephon and soil water availability on grain yield and growth patterns of corn. The objective of this research was to study the effects of ethephon rates and timing of applications in combination with different irrigation levels on water use, yield and its attributes, total dry matter accumulation, LAI, and plant height. The 2-yr study (1993–1994) was carried out at the CNR Irrigation Institute experimental farm in southern Italy (14°50' E, 40°07' N; sandy-clay soil) using corn (cv. Aida, FAO class 500). Treatments consisted of four irrigation regimes and four and six ethephon treatments for 1993 and 1994, respectively, in a randomized complete block design with three replicates. Irrigation regimes were a rainfed control (T0) and three treatments replenishing the soil water profile to field capacity to a depth of 0.7 m at different frequencies: Tw, weekly irrigation; T2, irrigation at two growth stages (VT and R1); and T4, irrigation at four stages (V7, VT, R1, and R4). Ethephon was applied both years at the V5 stage at rates of 280, 560, and 840 g a.i. ha−1. In 1994, two additional treatments were included by applying, at the V9 stage, an additional 280 g ha−1 of ethephon to treatments that had previously received 280 or 560 g a.i. ha−1. Increasing ethephon rates caused a significant reduction in LAI, plant height, and dry matter accumulation, resulting in a reduction in water consumption. In the rainfed control, increasing the ethephon rate resulted in a linear increase in yield, with maximum increase of about 200% (1.6 t ha−1) and 75% (1.7 t ha−1) in 1993 and 1994, respectively. By contrast, treatments irrigated four times showed a linear decrease of about 13% in both years. Ethephon treatment had no effect on grain yield in the Tw and T2 treatments. Kernel number was the yield component with the greatest influence on grain production. Our results suggest that ethephon may increase grain yield when natural or artificial water supply is a limiting factor.