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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.

As a cash crop, potato plays an important role in the economic development and ensuring food security. Reasonable management of irrigation and fertilization can promote the uptake of water and nutrients by potato, thereby improving the tuber yield and quality, and reducing fertilizer residues in the soil. A four-year field experiment was carried out to explore the effects of different irrigation amounts and fertilization rates on potato yield, economic benefit, tuber quality, water productivity (WP) and fertilizer use efficiency (FUE), and soil nutrient residues during 2016–2019. Multi-objective optimization of irrigation amount and fertilization rate was conducted based on data in 2018 and 2019 using the Analytic Hierarchy Process and Fuzzy Comprehensive Evaluation methods. In 2016 and 2017, three irrigation levels (W1, 60% ETC; W2, 80% ETC and W3, 100% ETC) and three fertilization (N-P-K) rates (F1, 100–17.5–124.5 kg/ha; F2, 150–26.2–186.7 kg/ha and F3, 200–34.9–248.9 kg/ha) were applied. The highest tuber yield was obtained under F3 in 2016 and 2017. Two fertilization rates (F0, 0 kg/ha and F4, 250–43.7–311.2 kg/ha) were further considered in 2018 and 2019. Results showed that the highest tuber yield, net income, WP, dry matter and the residues accumulation of nitrate nitrogen, available phosphorus, and available potassium were obtained under F4 in 2018 and 2019. However, the differences in tuber yield, net income and WP between F3 and F4 were not significant under W3. Deficit irrigation reduced tuber yield, ET, net income, shoot dry matter, tuber dry matter, LAI, relative chlorophyll content, starch and vitamin C content and FUE, and increased the residues of nutrient in the soil and reducing sugar content. Besides, W1 showed the highest irrigation water productivity, but the starch and vitamin C content of W3F2 were largest. The highest FUE was obtained under W3F3 (56.33% in 2018 and 53.33% in 2019). Increasing fertilization rate decreased the fertilizer partial factor productivity and sink/source. Based on the economic benefit, tuber quality, WP and FUE and soil environmental benefit, the multi-objective optimization was evaluated by the Analytic Hierarchy Process and Fuzzy Comprehensive Evaluation methods. When the irrigation amount was 100% ETC (W3) and the fertilization rate (N-P-K) was 200–34.9–248.9 kg/ha (F3), the multi-objective optimization was obtained. The results can provide a theoretical basis for the optimization of water and fertilizer regimes of potato in northern China and other regions with similar environments.

The scarcity of water resources has posed serious threats to the sustainable development of agriculture and promoted the need for water-saving technologies. Deficit irrigation has been widely used as a water-saving practice globally. Although it does facilitate the improvement in crop water productivity (WP), its influence on crop yield varies considerably. Therefore, a global meta-analysis was conducted to systematically and quantitatively analyze the responses of both WP and seed cotton yield to deficit irrigation, and explore the optimal conditions for the better application of deficit irrigation in practice. It was found that, although deficit irrigation averagely increased WP by 5.3% compared with full irrigation, it caused a significant decline in seed cotton yield by 20.2% on average. Overall, deficit irrigation performed best at the seedling+blooming stage of cotton under 80–100% full irrigation, in regions with seasonal precipitation ≥ 120 mm and average annual temperature ≥ 10 ℃. Cotton planted in medium textured soils with bulk density ≥ 1.35 g cm−3 obtained highest seed cotton yield and WP. Seed cotton yield and WP were increased by ridge planting with film mulching. Additionally, drip irrigation was most beneficial for seed cotton yield than sprinkler and furrow irrigations. Deficit irrigation throughout the whole growing season of cotton was the most undesirable measure. Seed cotton yield and WP were significantly affected by fertilization rate, and the appropriate nitrogen, phosphorus and potassium application rates were 300–400 kg N ha−1, 79–105 kg P ha−1 and 100–133 kg K ha−1, respectively. In conclusion, higher WP was obtained with acceptable reduction in seed cotton yield under deficit irrigation. However, to optimize deficit irrigation in practice, irrigation method and amount, deficit stage, climate condition, soil property, mulching mode and fertilization rate must be further considered.

Deficit irrigation (DI) and alternate partial root-zone irrigation (APRI) are widely recognized water-saving irrigation methods. This meta-analysis provided a systematic and quantitative result of the relative changes in yield and water use efficiency (WUE) of seven agricultural products (maize, wheat, cotton, potato, tomato, apple and grape) under conventional full irrigation (FULL), APRI and DI globally. Three comparisons were performed: (1) APRI by FULL, (2) APRI by DI and (3) DI by FULL. The results showed that the relative changes of yield and WUE differed among the three comparisons. Higher yield and WUE were achieved in fruits (apple and grape) under APRI compared with FULL or DI. However, the percentage changes in yield and WUE under APRI were not significantly different in vegetables (potato and tomato) and crops (maize, wheat and cotton). Compared with FULL, APRI performed better for acidic soils, clay loam or sandy loam, high bulk density (≥ 1.35 g cm−3), irrigation amount of 80–100% FULL, and was more appropriate for furrow irrigation in drier and colder environments. Compared with FULL, DI performed better for clay loam, low bulk density ( 200 mm. Yields under APRI and DI were remarkably lower than those under FULL, while the corresponding WUE were significantly higher. Compared with DI, fruits with furrow irrigation and in soils with clay and sandy loam were better under APRI. There was no significant difference in yield between APRI and DI, but WUE under APRI was higher. APRI increased both yield and WUE in regions with low average annual temperature (

Inappropriate water and fertilizer management can lead to unstable crop yield, and excessive irrigation and fertilization can potentially cause soil degradation and groundwater pollution. A two-year field experiment was conducted on drip-fertigated spring maize (Zea mays L.) in Ningxia of northwest China to explore the effects of four irrigation amounts (I75: 0.75ETc, I90: 0.90ETc, I105: 1.05ETc and I120: 1.20ETc, where ETc is the crop evapotranspiration) and four N-P2O5-K2O fertilization rates (F60-30-30, F120-60-60, F180-90-90 and F240-120-120 in 2016; F150-70-70, F225-110-110, F300-150-150 and F375-180-180 in 2017) on maize growth, grain yield, grain nitrogen accumulation, economic benefit and soil nitrate residue (NO3-N). Considering the goal of conserving both water and fertilizer while maintaining relatively high yields and minimizing soil NO3-N, a management strategy to optimize irrigation and fertilization regimes was developed based on the response surface methodology. The results showed that irrigation amount and fertilization rate significantly affected leaf area index, aboveground biomass, grain yield and harvest index. The irrigation-fertilization interaction significantly affected plant and grain nitrogen accumulation. In 2016 with lower fertilization range, grain yield and grain nitrogen accumulation were highest under I120F240-120-120, reaching 14,440 kg ha-1 and 184.50 kg ha-1, respectively. In 2017 with higher fertilization range, both grain yield and grain nitrogen accumulation initially increased and then decreased with increasing irrigation and fertilization regimes. Grain yield and grain nitrogen accumulation were highest under I90F300-150-150, reaching 16,884 kg ha-1 and 195.09 kg ha-1, respectively. Although plant nitrogen uptake was dramatically higher under I90F375-180-180 than those in the other treatments, grain yield was markedly lower under I90F300-150-150 and nitrogen harvest index was also lower. Soil NO3−-N increased with increasing fertilization rate, but it decreased with increasing irrigation amount. When irrigation amount and fertilization rate increased at the same time, the soil NO3−-N accumulation area moved deeper in the soil profile. Soil NO3--N content and distribution in the 60−100 cm soil layer showed an increasing trend, but this trend was less obvious than that in the 0−60 cm soil layer. When the irrigation amount was 447−452 mm and the N-P2O5-K2O fertilization rate ranged from 290−145-145 to-303−152-152 kg ha-1, grain yield, grain nitrogen accumulation and economic benefit (≥13,688 CNY ha-1) can reach 95 % confidence interval of their maximum values simultaneously. This study can provide a theoretical basis for high-efficient water and fertilizer utilization in sustainable spring maize (Zea mays L.) production in northwest China.

Crop yields are significantly restricted by the shortage of water resources in semi-arid and semi-humid regions around the world. Farming practices like ridge-furrow planting with plastic film mulching (RFFM) can effectively improve crop yield and crop water productivity (WP) by enhancing soil moisture and temperature availability. This meta-analysis study collected and analyzed the data of 964 observations published in 90 peer-reviewed papers to investigate the effects of various farming practices, i.e., RFFM, ridge-furrow planting without film mulching (RF) and flat planting with film mulching (FM) in comparison with conventional flat planting without film mulching (F), on yield and WP of three major crops (wheat, maize and potato) in China, in terms of planting region, climatic condition, altitude, soil type and seeding method. The results showed that RFFM, RF and FM improved mean crop yields by 33.8 %, 16.6 % and 27.0 %, and increased mean WP of crops by 35.8 %, 17.5 % and 27.8 % compared with F, respectively. Increases in crop yields under RFFM, RF and FM were greater in regions with seasonal rainfall 400 mm. RFFM, RF and FM performed better in Northwest China than in North-central and other regions of China. Among the three crops, potato obtained the greatest increases in yield and WP under ridge-furrow planting or film mulching. For clay soils and high altitude regions, the two film mulching practices (FM and RFFM) attained greater yield increases. With regards to the two ridge-furrow practices (RFFM and RF), it is better to plant crops in the furrow than on the ridge. In short, RFFM was most effective to improve yield and WP of wheat, maize and potato among the farming practices. These findings have important implications for choosing appropriate field management practices to improve crop yield and crop water productivity in China.