The combined application of manure and mineral fertilizer represents an effective strategy for enhancing crop yield. However, the relationship between soil fertility and crop yield remains unclear in saline-alkaline soil. Here, a 9-year field experiment (2015–2023) was conducted to investigate the effects of manure application and crop rotations on crop yield and economic efficiency as well as potential associated mechanisms in the Hetao Irrigation District. The results showed that in the third cropping rotation cycle, combined application of manure and mineral fertilizers (NPKO) caused a 6.2%, 38.9%, 65.3%, and 132.2% increase in wheat, sunflower, wheat equivalent yield, and the economic income of sunflower, respectively. The average grain yield had a positive correlation with soil organic matter and nutrient supply. This suggested that the soil organic matter had a positive effect on the crop yield due to its impact on nutrient supply. Simultaneously, the sunflower seed setting rate increased by 65.2% under NPKO. The linear regression model revealed that each additional input of 20 Mg ha⁻¹ of manure resulted in an increase of 3.56 kg ha⁻¹ in crop phosphorus harvest and a 0.05 Kg ha⁻¹ increase in wheat equivalent yield compared to NPK. In conclusion, our results highlighted that manure application promotes soil properties and improves crop yield.

Crop diversification has been proposed as a promising strategy for transitioning towards sustainable agricultural systems. The Hetao Irrigation District faces multiple challenges in ensuring food security and farmer livelihood. A diversified green manure inclusive cropping system was designed to evaluate the influences of hairy vetch (Vicia villosa Roth) incorporation on soil nutrients, yield, and economic benefit compared to the existing wheat–maize–sunflower rotation system in the Hetao Irrigation District. The specific method was as follows: spring wheat (Triticum-durum L.)–vetch rotation in the first year, maize (Zea mays L.)/vetch intercropping in the second year, and sunflower (Helianthus annuus L.)/vetch relay intercropping in the third year. Over a 6-year experimental observation, green manure incorporation significantly increased soil alkaline hydrolyzed nitrogen and exchangeable potassium levels. Although the effect of green manure incorporation on the yield of rotated spring wheat and intercropped maize was not prominent, it improved sunflower yield in the second rotation cycle by 11%. Consequently, only the sunflower led to an increase in income of 235 CNY ha⁻¹ in the second rotation cycle. This indicates that the soil-property-building and yield-enhancing effects of green manure incorporation require time to accumulate. However, the benefits derived from increased yield were not sufficient to offset the production costs associated with green manure cultivation, resulting in less-than-desirable economic returns.

Leguminous green manure (LGM) has a reputation for improving crop productivity. However, little is known about the beneficial interactions with straw on crop yield and nutrient (N, P, K) use efficiency. Herein, a 9-year field experiment (from 2015 to 2023) containing three treatments—(1) chemical fertilizer as the control (CK), (2) NPK + straw return (Straw) and (3) NPK + straw return with LGM (Straw + LGM)—was conducted to investigate whether the combined application of LGM and straw can increase productivity and nutrient use efficiency in the wheat–maize–sunflower diversified cropping rotation. The results showed that in the third rotation (2021–2023), Straw + LGM significantly increased wheat yield by 10.2% and maize yield by 19.9% compared to CK. The total equivalent yield under Straw + LGM was the highest (26.09 Mg ha⁻¹), exceeding Straw and CK treatments by 2.7% and 12.3%, respectively. For each 2 Mg ha⁻¹ increase in straw returned to the field, sunflower yield increased by 0.2 Mg ha⁻¹, whereas for each 1 Mg ha⁻¹ increase in LGM yield from the previous crop, sunflower yield increased by 0.45 Mg ha⁻¹. Compared to CK, the co-application of LGM and straw increased the N use efficiency of maize in the first and third rotation cycle by 70.6% and 55.8%, respectively, and the P use efficiency by 147.8% in the third rotation cycle. Moreover, Straw treatment led to an increase of net income from wheat and sunflower by 14.5% and 44.6%, while Straw + LGM increased the net income from maize by 15.8% in the third rotation cycle. Combining leguminous green manure with a diversified cropping rotation has greater potential to improve nutrient use efficiency, crop productivity and net income, which can be recommended as a sustainable agronomic practice in the Hetao District, Northwest China.

The Hetao Irrigation District, situated in the Northwest of China, serves as a significant commercial grain base. Widespread use of atrazine, an herbicide in the region, has resulted in significant environmental issues, impacting the ecosystem equilibrium and sustainable agricultural development. The co-adsorption of the globally employed atrazine herbicide along with two nonionic surfactants, Tween-80 and Brij30, onto soils treated with HCl and H₂O₂ was investigated. The study revealed that the adsorption isothermal curves of surfactants on soil adhered to a two-stage adsorption model. Various types of adsorption isothermal curves, such as S-type or L-type, influenced the adsorption capacity of atrazine on the soil. Observations indicated that S-type or L-type isothermal curves of surfactants interconverted with alterations in soil polarity. Moreover, it has been uncovered that the adsorption properties of Tween 80 in the soil are intricately connected to its ability to elute atrazine within the same soil. This discovery provides theoretical support for a prudent reduction in herbicide usage in the Hetao Irrigation District in the upcoming years.