Water productivity, growth, and physiological assessment of deficit irrigated cotton on hyperarid desert-oases in northwest China

Critical water shortage and hyperaridity are the principal reasons, limiting cotton cultivation on desert-oases in northwest China. However, if water dearth is effectively managed then these terrains can also add significant contribution in regional and country's total cotton production due to favorable climate. In that perspective, a 2-years (2015-2016) field study was conducted on cultivable southern periphery of Taklamakan desert to optimize water productivity of deficit drip irrigated cotton through evaluating its water use (ETc), growth, and physiology based water relations. Treatments included four drip irrigation regimes based on 100 (D100), 80 (D80), 60 (D60), and 40% (D40) replenishment of depleted water from field capacity. Results revealed that average ETc ranged from 510 mm at 40% to 1079 mm at 100% water replenishment. Crop growth and pre-dawn leaf water potential (ψpd) successively declined with reducing irrigation amount. Photosynthesis (A), and stomatal conductance (gs) of D80 plants decreased by 15% at squaring and by only 8% at later stages while, this decline was more vigorous under 60 and 40% water replenishments. The 80% irrigated plants resulted in only 13% yield reduction from D100 whereas, the average seed cotton yield varied from 2433 kg ha−1 in 40% to 4376 kg ha−1 under 100% water replenishment. The maximum irrigation, and crop water use efficiencies (IWUE, WUE) were recorded 0.62 and, 0.48 kg m−3, respectively, which reduced with increasing irrigation amounts. In addition, crop growth and physiological attributes showed linear correlations with ETc and irrigation regimes during yield formation. Following economic evaluation, these results suggested that, irrigating cotton up to 80% field capacity would provide the optimum yield and net income with 20% water saving while, D60 could save 40% water but, subject to major yield and profit loss. However, if water is sufficiently available then 100% irrigation can be practiced for maximizing cotton productivity and net gains on desert-oases.