The effects of stomatal factors of plant leaves under partial root-zone drying (PRD) have been widely studied. However, the non-stomatal factors and the relationship between photosynthesis with soil moisture have not been explored. In this study, four treatments over-irrigation, full irrigation, moderate water deficit, and severe water deficit were investigated, aiming to evaluate the effects on the diurnal variation of alfalfa leaf photosynthesis under PRD and its relationship with stomatal and non-stomatal limitations, as well as soil moisture. The results showed that any levels of water deficit led to a decrease in the photosynthetic rate (P_n) of alfalfa leaves. Leaves under moderate and severe water deficit displayed a pronounced midday “photosynthetic lunch break,” while those under over- and full irrigation did not display this phenomenon. Before 11:30 a.m., the reduction in P_n was primarily due to stomatal limitations, as evidenced by reduced stomatal conductance (G_s) and decreased intercellular CO₂ concentration (C_i). After 11:30 a.m., non-stomatal limitations became the dominant factor, with both G_s and transpiration rate (T_r) continuing to decrease, while C_i increased, indicating a shift in the limiting factors. Under PRD with moderate water deficit, alfalfa experienced both stomatal and non-stomatal limitations within a single day, leading to a hay yield reduction of 18.6%. Additionally, over-irrigation helped to maintain higher P_n and T_r, increasing alfalfa yield and thus improving water productivity by 33.1%. The correlation coefficients between soil moisture content at 10 cm depths with alfalfa leaf P_n, T_r, and G_s on the photosynthetic measurement day were 0.9864, 0.8571, and 0.8462, respectively. At 20 cm, the correlation coefficients were 0.8820, 0.6943, and 0.6951, respectively. The study concluded that both stomatal and non-stomatal mechanisms contributed to reduced alfalfa P_n in water deficit of PRD. Furthermore, shallow soil moisture also played a crucial role in influencing photosynthetic performance.

Currently, the world is facing a serious agricultural water crisis, which also affects grassland areas. Alfalfa, a key perennial forage legume, consumes about 10% of China’s pastoral irrigation water. Reducing irrigation generally results in a loss of hay yield, but the effects on alfalfa quality and its relationship to water use are less clear. In this study, we explore alfalfa quality under different irrigation deficits and its relationship to water use in the Hexi Corridor of China. Alfalfa water use, quality yield (relative feeding value yield (RFV_yield) and crude protein yield (CP_yield)), and quality water use efficiency (relative feeding value water use efficiency (WUE_RFV) and crude protein water use efficiency (WUE_CP)) were measured in a field experiment. Alfalfa quality showed a negative correlation with the irrigation quota (the determination coefficient for relative feeding value was 0.375 and for crude protein was 0.289). There was a positive correlation between quality yield and irrigation quota (the determination coefficient for RFV_yield was 0.570 and for CP_yield was 0.631). The higher irrigation quota increased quality yield, which compensated for its negative effects on alfalfa quality. The mild and moderate water deficit treatments showed lower WUE_RFV than both the severe and no water deficit treatments. Moderate or mild water deficit is recommended to be used for one-year-old alfalfa treatment. No water deficit is beneficial to improve the quality water use efficiency of two-year-old alfalfa.

Leaves, as the primary “source” organ for photosynthesis, directly influence plant yield. However, it remains unclear whether leaf removal affects Jerusalem artichoke yield by altering rhizosphere nutrient availability. This study evaluated the effects of different leaf removal intensities on tuber yield and rhizosphere nutrient characteristics of Jerusalem artichoke (Helianthus tuberosus L.). Results from two consecutive field experiments demonstrated that removal of the lower leaves (Q2) significantly increased tuber yield in both years, with gains of 93.7% in 2022 and 282% in 2023 compared with the control. Although other leaf removal treatments also showed yield increases, these were not statistically significant. Principal component analysis revealed that rhizosphere soils associated with tubers and taproots contained higher concentrations of ammonium nitrogen, nitrate nitrogen, available phosphorus, and available potassium than bulk soils. Among these nutrients, tuber yield was significantly and positively correlated with available potassium (r = 0.57). These findings indicate that moderate removal of lower leaves enhances rhizosphere nutrient conditions and promotes higher tuber yield in Jerusalem artichoke.