Effect of surface water and underground water drip irrigation on cotton growth and yield under two different...

To investigate the effect of surface water and underground water drip irrigation on cotton yield, dry matter accumulation and nutrients uptake, two consecutive field experiments were conducted. The first experiment (different mixing ratio irrigation) comprised of five ratios of underground water to surface water including; 1:0 (U), 0:1 (S), 1:1 (U:S = 1:1), 1:2 (U:S = 1:2) and 1:3 (U:S = 1:3). Whereas, the second experiment (round irrigation) comprised of eight treatments including: 1:3 (T1), 2:2 (T2), 3:1 (T3), {S:U 3:1 (T4)}, 2:2 {S:U (T5)}, 1:3 {S:U (T6)}, 4:0 (T7) and 0:4 (T8). The average concentration of leaves dry matter after 8th irrigation in different mixing ratio experiment was significantly increased by 131.2% (S), 34.4% (U: S = 1:1), 59.3% (U: S = 1:2), and 93.7% (U: S = 1:3), respectively, relative to U treatment. Likewise, the stem dry matter increased from 48.5 g (U), to 122.2 g (S) and 101.6 g (U:S = 1:3). The soil available N at 0-20 cm after 8th irrigation recorded an average increase rate of 40.1%, 6.6%, 13.5%, and 29.5%, respectively. However, at 20-40cm an average increase rate of 37.4% (S), 7.1% (U: S = 1:1), 20.0% (U: S = 1:2), and 21.9% (U: S = 1:3) were noted (p < 0.05). The highest cotton yield of 6571 kg h-1 was recorded in S treatment compared with the U treatment (5492 kg h-1), U: S = 1:1 (5502 kg h-1), U: S = 1:2 (5873 kg h-1) and U: S = 1:3 (6111 kg h-1). Contrastingly, in round irrigation experiment the highest leaves dry matter at various growth stages were recorded in T8 treatment. For instance, compared with T7 treatment an average increase rate of 50.6% (growth), 100.9% (boll) and 93.3% (boll opening), in stem dry matter were recorded in T8 treatment. Moreover, the concentration of N in round irrigation at 0-20 cm at different growth stages were 83.3±2.8 (growth stage), 79.01±1.84 (boll stage), and 96.16±3.83 (boll opening stage) in T8. Whereas, in T7 the concentration of N was 36.1±5.9 (growth), 54.51±2.81 (boll), and 53.9±3.83 (boll opening) (p < 0.05). Similarly, cotton yield were substantially higher in T8 applied treatment and follows the sequence of T8 > T1 > T4 > T2 > T5 > T3 > T6 > T7. Overall, our findings provide meaningful information to current irrigation practices in water scarce regions. Improving water use efficiency is a viable solution to the water scarcity. Therefore, surface water irrigation is recommended as an effective irrigation strategies to improve cotton yield and growth.