Irrigation based on daily weighted evapotranspiration affects yield and quality of oriental melon

Abstract

Irrigating based on crop evapotranspiration is an important way to achieve precise and intelligent regulation of modern agriculture. But the relationship between irrigation and evapotranspiration is not clear, and how to use the evapotranspiration to decide irrigation also was not clear. To explore the relationship between irrigation and evapotranspiration, Oriental melons (Qianyu No. 6) was investigated, and daily weighted evapotranspiration (WET) was used to determine the quantity of water used to irrigate the plants. Supplemental irrigation treatment was carried out at the blooming/fruiting stage and fruit expansion stage as follows: treatment 1, 80 % WET + 110 % WET (T1); treatment 2, 100 % WET + 130 % WET (T2); treatment 3, 120 % WET + 150 % WET (T3); treatment 4, 100 % WET + 150 % WET (T4). Irrigation amount (x) was positively related to WET (Y) according to Y = 0.81x0.76 (R2 = 0.90). Performance index based on absorption of light energy(PiABS) increased with increased total irrigation. Irrigating with 100 % WET in the blooming/fruiting stage improved Brix index values and soluble sugar content compared to other treatments. NO3− accumulation was the highest for the T1 treatment, which featured the lowest irrigation amounts; irrigation water use efficiency (WUEI) and leaf intrinsic water use efficiency (WUEin) were also the highest but single-fruit weight declined by about 36 %. Yield was highest for the T3 treatment, which featured the highest total irrigation. The average weight of a single fruit increased by 5% and the irrigation amount increased by 14 % in T3 compared to T4. Overall, this study shows using weighted evapotranspiration to determine irrigation is feasible. In terms of yield and quality, our experiments showed that 120 % WET in the blooming/fruiting stage and 150 % WET in the fruit expansion stage shown to be reasonable for summer melon cultivation in northwestern China.