Evangelos D. Gonias1, Derrick M. Oosterhuis1, Androniki C. Bibi1, and Bruce Roberts2. (1) University of Arkansas, 1366 W. Altheimer Dr., Fayetteville, AR 72704, (2) Department of Plant Science, CSU-Fresno, 2425 E. San Ramon Ave., M/S AS 72, Fresno, CA 93740
The amount of intercepted radiation and the time allowed for growth determines the accumulation of dry matter (Sinclair and Muchow, 1999). Dry matter production (g) per unit of intercepted radiation (MJ) can be defined as the effectiveness of the crop to convert intercepted radiation to dry matter. This correlation has been described as linear (Monteith, 1977) and the slope is the RUE of the crop.
Yield variability in cotton (Gossypium hirsutum L.) from year to year in different environments (geographical locations) is a major production problem for farmers (Oosterhuis, 2002). Higher yields have been recorded in the drier environment of California, compared to the more humid environment of Arkansas. However, the effect of environmental factors, such as temperature, relative humidity and vapour pressure deficit on the radiation use efficiency in cotton have not been described for contrasting environments. Therefore, research was conducted in Arkansas and California to investigate differences in RUE of cotton.
Plant growth regulators (PGRs) are a common and widely used practice in cotton production for controlling plant growth, increasing yield and improving management efficiency. Most of the PGRs used have an effect on plant growth, both vegetative and reproductive, and dry matter partitioning. However, there have been no reports of effects of PGRs on radiation use efficiency (RUE). It is logical to assume that any chemical that affects canopy dynamics will change the RUE of the crop. The objective of this study was to quantify the effect of PGRs on the RUE of cotton.
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