Water Productivity and Yield Response of Deficit-Irrigated Kenaf (Hibiscus cannabinus L.) under Subhumid Climate Conditions

Kenaf has gained particular interest in the last decade as a fiber crop with several uses in the production of energy and paper pulp. In this study, the effects of different irrigation water levels on dry matter yield, yield components, water productivity and irrigation water productivity for dry matter (WP and IWP, respectively), dry core (WPc and IWPc, respectively), and dry bast (WPc and IWPc, respectively) yield of drip-irrigated kenaf plants (Tainung 2 variety) were investigated under subhumid climate conditions and crop water production functions of kenaf plants were determined. Field experiments were carried out using a completely randomized blocks design with three replications in 2019 and 2020. The experimental treatments consisted of the full irrigation treatment (T1), treatments in which 2/3 (T2) and 1/3 (T3) of the irrigation water quantity given to the T1 treatment were applied, and a rain-fed treatment (T4). The effects of different irrigation water levels applied to kenaf plants on plant height, basal stem diameter, fresh stem yield, dry stem yield, fresh core yield, dry core yield, fresh bast yield, dry bast yield, fresh biomass yield, and dry matter yield were found to be significant (p<0.01). The dry matter yield values varied between 12.01 (T4) and 22.24 (T1) t ha(-1) in 2019 and between 8.53 (T4) and 17.95 (T1) t ha(-1) in 2020. Yield response factor (k(y)) values were calculated to be 0.81 in 2019, 0.92 in 2020, and 0.86 for both years. The WP values for the experimental years were calculated to be 2.47-3.68 kg m(-3). The highest IWP value was obtained from the T1 treatment (1.72 kg m(-3)) in 2019 and from the T2 treatment (1.76 kg m(-3)) in 2020. The T1 and T2 treatments were statistically in the same group according to water productivity and irrigation water productivity values for both years. Based on k(y), water productivity, and irrigation water productivity values, the T2 treatment can be suggested as an appropriate irrigation schedule in terms of water conservation under limited water resources conditions.