Intercropping is a key methodology used by farmers to improve economic benefits. However, in certain areas such as Xinjiang, China, limitations in available irrigation water make intercropping difficult to implement. Farmers are therefore challenged to improve economic benefits in water‐limited conditions. We evaluated the effectiveness of intercropped common jujube (Zizyphus jujuba Mill.) and cotton (Gossypium hirsutum L.) under different irrigation regimes. Using a factorial design, crops were planted individually and together (i.e., intercropping) under five different irrigation systems. We measured growth parameters and evaluated the temporal distribution of root system growth and fruit yield. Intercropped cotton displayed higher fitness metrics and outperformed the single‐cropped cotton in crop yield. Intercropping, however, had the opposite effect on jujube plants: the overall fitness and yield of jujube were significantly curtailed under the interspecific competition induced by this planting technique. Under low irrigation levels, cotton plants tended to invade the jujube niches that reduced jujube growth and development. Our findings suggest that in a jujube/cotton intercropping system, cotton is the dominant competitor, whose ability to inhibit the development of the less competitive jujube is exacerbated under water deficit situations. Although intercropping system affected jujube development, overall cotton yield, and therefore benefit to farmers was considerably higher using this system. However, the competitive ability of jujube gradually increases as the plant aged which could reduce the economic advantages of the intercropping system.

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Highlights Moderate water deficit will help reduce agricultural investment. Application of potassium fertilizer can alleviate the effect of water deficit on fruit trees. Reasonable ratio of water and fertilizer is helpful to improve economic benefits. Abstract . The jujube planting industry is a key agricultural industry in Xinjiang, China. With an arid climate and limited water resources, Xinjiang must implement more efficient water-saving irrigation systems to guarantee the sustainable development of jujube planting industry. A two-factor, three-level test was adopted to explore how regulated deficit irrigation and different potassium fertilizer levels affected the growth and yield of jujube under drip irrigation. The results of analysis of variance showed that water deficit significantly affected photosynthetic characteristics, growth parameters, evapotranspiration, and yield. The effect of K-application level was focused on fruit volume and yield. However, when the ratio of water to fertilizer is unbalanced (150% K-application + severe water deficit), the growth of jujube trees be inhibited, and the fruit volume and economic benefits reduced by 7% and 11%, respectively. Means comparison indicated that growth parameters, evaporation, and yield under minor water deficit was lower than that under the adequate irrigation by 7%, 13%, and 6%, respectively; and economic performance was higher by 12%. Severe water deficit reduced growth parameters and economic benefits by 33% and 55%, respectively. Thus, minor water deficit irrigation significantly inhibited luxury transpiration and growth redundancy, improved water-use efficiency and increased economic performance. Severer water deficit may damage trees and negatively affect the jujube industry. With economic benefit analysis, 150% K-application with adequate irrigation and minor water deficit, 100% K-application with adequate irrigation and minor water deficit, 50% K-application with minor water deficit all achieve high economic benefits (14074~17261 RmB ha-1). However, when taking water restrictions, the environmental and economic costs of fertilizer, and the long-term effects of tree development into account, application of 100% K-application with minor water deficit (irrigation, 75% ETc; fertilizer, 200 kg ha-1 compound fertilizer+360 kg ha-1 potassium fertilizer) is recommended. Keywords: Deficit irrigation, Economic benefit, Potassium fertilizer, Yield.

Accurate prediction of orchard evapotranspiration (ET) can optimize orchard water management. Based on the jujube (Zizyphus jujuba), ET was continuously measured from 2016 to 2019 using a large weighing lysimeter; the actual jujube ET was compared with the ET simulated with the Priestley–Taylor (P–T), Dual Crop Coefficient (Dual Kc), and Shuttleworth–Wallace (S–W) models, to verify the accuracy of the three models. The results showed that, from 2016 to 2019, the whole growth period of jujube ET was 532–592 mm and the crop coefficient was 0.85–0.93. The basal crop coefficients of the calibrated Dual Kc model were 0.4, 1.0, and 0.5 at the initial, middle, and ending growth stages, respectively. The overall simulation error of the Dual Kc model was low, and simulations were stable during the four years of the study. However, because of rough estimation the water stress coefficient (Ks) simulation accuracy will be reduced in the case of serious water shortage. The simulation error of the S–W model was greater than the simulation error of the Dual Kc model, and the simulations were unstable and vulnerable to interannual changes. The simulation error of the traditional P–T model was large. When the parameter “α” solution method was improved, the simulation accuracy was significantly improved, and the P–T model’s simulation accuracy was only slightly lower than that of the Dual Kc model. However, the model was easily affected by changes in net radiation and air temperature. Therefore, the Dual Kc model is recommended for estimating the ET of young jujube trees in arid areas.