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Wolfberry (Lycium barbarumL.) is important for health care and ecological protection. However, it faces problems of low productivity and resource utilization during planting. Exploring reasonable models for water and nitrogen management is important for solving these problems. Based on field trials in 2021 and 2022, this study analyzed the effects of controlling soil water and nitrogen application levels on wolfberry height, stem diameter, crown width, yield, and water (WUE) and nitrogen use efficiency (NUE). The upper and lower limits of soil water were controlled by the percentage of soil water content to field water capacity (θf), and four water levels, i.e., adequate irrigation (W0, 75%–85% θf), mild water deficit (W1, 65%–75% θf), moderate water deficit (W2, 55%–65% θf), and severe water deficit (W3, 45%–55% θf) were used, and three nitrogen application levels, i.e., no nitrogen (N0, 0 kg/hm2), low nitrogen (N1, 150 kg/hm2), medium nitrogen (N2, 300 kg/hm2), and high nitrogen (N3, 450 kg/hm2) were implied. The results showed that irrigation and nitrogen application significantly affected plant height, stem diameter, and crown width of wolfberry at different growth stages (P<0.01), and their maximum values were observed in W1N2, W0N2, and W1N3 treatments. Dry weight per plant and yield of wolfberry first increased and then decreased with increasing nitrogen application under the same water treatment. Dry weight per hundred grains and dry weight percentage increased with increasing nitrogen application under W0 treatment. However, under other water treatments, the values first increased and then decreased with increasing nitrogen application. Yield and its component of wolfberry first increased and then decreased as water deficit increased under the same nitrogen treatment. Irrigation water use efficiency (IWUE, 8.46 kg/(hm2•mm)), WUE (6.83 kg/(hm2•mm)), partial factor productivity of nitrogen (PFPN, 2.56 kg/kg), and NUE (14.29 kg/kg) reached their highest values in W2N2, W1N2, W1N2, and W1N1 treatments. Results of principal component analysis (PCA) showed that yield, WUE, and NUE were better in W1N2 treatment, making it a suitable water and nitrogen management mode for the irrigation area of the Yellow River in the Gansu Province, China and similar planting areas.

Crop residue returning (CRR) is known to improve the soil environment and thus increase crop production. However, the impacts of CRR on wheat (Triticum aestivumL.) yield have been contrary at times due to the differences in climatic conditions, soil traits, and management practices. These effects were evaluated using 351 paired observations published in 161 papers comprising studies conducted in 19 provinces (autonomous regions) of China. No publication bias or extreme values were found in the data, indicating that the analysis results are highly reliable. Compared with the practice of no crop residue returning (NCRR), the practice of CRR increased wheat yield significantly, on average by 8.29%, and proved more beneficial in Northwest China and in regions with average annual precipitation of 200 to 400 mm, average annual temperatures >11°C, sandy loam soil, and rotation with legumes (soybean [Glycine max(L.) Merr.]–wheat and pea [Pisum sativumL.]–wheat). The following aspects of CRR and crop management conferred greater benefits in yield: continuing the practice for 3 to 6 yr (compared with 1–2, 7–10, and ≥11 yr), using the residues at 3 to 6 t ha−1(compared with <3, 6–9, and > 9 t ha−1), chopped straw (compared with intact straw), rainfed conditions (compared with irrigated conditions), and applying N at 200 to 300 kg ha−1(compared with <100, 100–200, and >300 kg ha−1). The yield increase was significantly higher when the residues were returned in the form of mulch (12.56%) and for spring wheat (11.90%) than plowing them back into soil (4.53%) and for winter wheat (7.09%). The meta‐analysis thus confirms the benefits of CRR in higher wheat yields in China and also suggests that the benefits of CRR are site specific.