Responses of yield, quality and water-nitrogen use efficiency of greenhouse sweet pepper to different drip fertigation regimes in Northwest China

Abstract Given water resources scarcity in Northwest China and the urgent need for the integration and optimization of scientific and technological resources in facility agriculture, this experiment explored the appropriate water and fertilizer management measures for greenhouse sweet pepper under fertilization in Northwest China. A two-year drip fertigation sweet pepper experiment was conducted in a solar greenhouse, with four irrigation levels (W1: 105% ETC, W2: 90% ETC, W3: 75% ETC, W4: 60% ETC) and four nitrogen levels (N1: 300 kg/ha, N2: 225 kg/ha, N3: 150 kg/ha, N4: 75 kg/ha). The results showed that above-ground dry matter accumulation (DMA), yield, harvest index (HI), and water use efficiency (WUE) of sweet pepper increased first and then decreased with the increase of irrigation/nitrogen amounts under the same nitrogen/irrigation levels. The partial factor productivity of nitrogen (PFPN) decreased significantly with the increase of nitrogen application rate, while it increased first and then decreased with the increase of irrigation level. The PFPN reached a peak at W2 level, despite no significant difference between W2 and W3 levels. With the increase of nitrogen application rate, soluble sugar and vitamin C content increased first and then decreased with a maximum at N3 level; nitrate content increased with the increase of nitrogen application rate, and there was no significant difference between N4 and N3 levels. The contents of soluble sugar and nitrate nitrogen decreased with the increase of irrigation amount, and they did not differ between W1 and W3 levels at N3 level; the vitamin C content increased first and then decreased with the increase of irrigation amount, reaching the maximum in W2 or W3 treatments. Considering the shortage of water resources in the study area, the W3N3 treatment (75% ETC, 150 kg/ha) could be recommended as the optimal drip fertigation strategy. Results showed that the optimal value of sweet pepper (the best confidence intervals of 85%) was achieved at the irrigation water and nitrogen amount of 78.2–80.8% ETC and 164.5–189.5 kg/ha, respectively. This study provides scientific basis for water and nitrogen management of high yield, quality, and benefit planting of facility sweet pepper in Northwest China.