Effects of water and nitrogen coupling on the yield, quality, and water and nitrogen utilization of watermelon under CO2 enrichment

Abstract

We conducted an experiment with 12 treatments to evaluate the effects of water and nitrogen coupling on the yield, quality, and irrigation water-use efficiency (IWUE) and nitrogen-use efficiency (NUE) of watermelon under CO2 enrichment in the morning. The treatments included three different irrigation levels, I1 (80%Ep), I2 (100%Ep), and I3 (120%Ep), two different nitrogen levels, N1 (6.876g/plant) and N2 (13.752g/plant), and two different CO2 concentration levels, C1 (400ppm) and C2 (800ppm). The enrichment of CO2 significantly promoted vitamin C and total sugar content of the quality indicators. The amount of irrigation water applied had a significant effect on the yield, quality, IWUE and NUE. The amount of nitrogen applied had an effect on NUE, IWUE and on some quality indicators. Increasing CO2 had no significant effect on yield; however, the interaction between CO2, nitrogen application and irrigation on yield was significant. The highest yield was observed under the treatment with high CO2, high water and high nitrogen. The coupling of CO2 and nitrogen application had a significant effect on both IWUE and NUE. Specifically, the addition of CO2 improved the IWUE and NUE under low nitrogen treatment. The coupling of CO2 and nitrogen application rate had a significant effect on all of the quality indicators.