Huaiyu Long

Optimizing water and nitrogen (N) management is critical for enhancing crop productivity under water scarcity. This study aimed to determine if a high irrigation upper limit can compensate for a low lower limit and whether optimal N application can mitigate the impacts of a wide irrigation range in okra. A pot experiment was conducted with three irrigation ranges (defined by the lower and upper limits of soil field capacity, FC) and two N rates: W1 (45–55% FC), W2 (35–65% FC), W3 (25–75% FC) and N1 (110 kg ha⁻1), N2 (220 kg ha⁻1). Results demonstrated that a high upper limit could not compensate for the adverse effects of a low lower limit. The narrow irrigation range (W1) consistently outperformed wider ranges, increasing yield by up to 42.3% compared to the wide irrigation range (W3). Moderate N application (N1) effectively alleviated the impacts associated with W3, boosting its yield by 24.9%, whereas excessive N (N2) was often detrimental. The optimal W1N1 combination synergistically enhanced system performance, achieving the highest yield (56.7% greater than the poorest N2W3 treatment), improving fruit quality (e.g., 11.5% higher soluble sugar), and increasing soil urease activity by 25.9%. Conversely, N2 led to soil acidification and nutrient imbalance. These results demonstrate that coupling a narrow irrigation limit range with moderate N is an optimal strategy for enhancing okra productivity and soil health, providing a viable guide for sustainable cultivation.

Strawberry (Fragaria × ananassa Duch.) has a unique flavor and nutritional value. To investigate the effects of deficit irrigation on the growth, yield, quality, and water use efficiency of strawberries, “Zhangji” and “Hongyan” varieties were assessed in a greenhouse. Four irrigation levels were set as 95% (CK), 75% (LS), 55% (MS), and 35% (±5%) (SS) of the field capacity, respectively. Five successive plant growth stages were analyzed. The results indicate that the plants’ daily water consumption intensity, as well as fruit yield and titratable acidity, decreased with increasing water stress, while vitamin C (Vc), soluble sugar, soluble protein, the sugar–acid ratio, and water use efficiency increased. Yield significantly decreased under the MS and SS treatments compared with CK. Malondialdehyde, proline contents, and superoxide dismutase activity reached the highest values under SS. Our results indicate that the greatest effect of water restriction occurs during the seedling growth and fruit color-turning periods. Given the higher Vc, titratable acidity, soluble sugars, and soluble proteins, the “Zhangji” variety may be preferable to the “Hongyan” variety, and an irrigation level at 70~80% of field capacity is recommended for good strawberry yield and taste quality. Deficit irrigation can save water resources, improve water use efficiency, and promote agricultural sustainable development.

The aim of this study is to investigate the effect of soil water stability on maize (Zea mays L.) yield, water use, and its photosynthetic physiological mechanisms, and to innovate the relationship between maize and soil water, which currently only considers soil water content and neglects soil water stability. An organized water experiment was conducted on maize. The effects of stable soil water (SW) at two water content levels were examined, with fluctuating soil water (FW) as a control. The assessed effects included leaf water, chlorophyll, gas exchange, leaf water use efficiency (WUE), stable carbon isotope ratio (δ13C), and yield of maize. Soil water stability had a significant effect on maize yield, yet it was slightly smaller than soil water content. Compared with FW, SW increased the maximum net photosynthetic rate, saturated light intensity, stomatal conductance, SPAD, leaf water content, and leaf WUE, and decreased δ13C, promoting dry matter assimilation and conversion into grain yield, ultimately increasing yield by 100.8%. Under the same soil water stability, 55% FC versus 75% FC weakened photosynthetic capacity and exacerbated stomatal limitation of maize leaves, making them more susceptible to light inhibition, which decreased photoassimilate accumulation, resulting in a significant decrease in yield. And the δ13C under 75% FC conditions decreased by 4.7–7.7% compared with 55% FC. In conclusion, SW exhibits a positive effect on maize leaf water content, photosynthetic carbon assimilation, and grain yields, regardless of soil water content. Compared to FW, SW increased leaf WUE and maize yield by enhancing photosynthesis, and SW has stronger discrimination against 13C during photosynthetic CO2 assimilation, thus decreasing leaf δ13C. This study fills a gap in understanding how soil water stability influences maize yield and gas exchange, and provides a fresh perspective on how to improve crop yield and WUE by managing soil water stability.

Uneven rainfall, in the context of global warming, can cause soil moisture fluctuations (SMFs) that harm crop growth, and it is not yet known whether nitrogen (N) can mitigate the harm caused by a strong SMF. This paper uses okra as a test subject and sets three SMFs of 45–55% FC (W₁), 35–65% FC (W₂), and 25–75% FC (W₃) and three N applications of 0 kg hm⁻² (N₀), 110 kg hm⁻² (N₁), and 330 kg hm⁻² (N₂) to investigate the effects of SMF and N application on the physiological and biochemical aspects of okra. The results demonstrated that okra exhibited the highest values in stem diameter, number of leaves, photosynthesis characteristics, antioxidant enzyme activity, and yield under the N₁ treatment. The average yield in the N₁ treatment was 149.8 g, significantly surpassing the average yields of the N₀ (129.8 g) and N₃ (84.0 g) treatments. Stomatal density, antioxidant enzyme activity, malondialdehyde content, and proline content in okra leaves were highest in the W₃ treatment, indicating that plants experienced stress in the W₃ treatment. However, the agronomic traits and yields of okra in the N₁ treatment were higher than those in the N₀ and N₁ treatments, indicating that the crop damage caused by W₃ could be mitigated by an appropriate amount of N application. The N₁W₁ treatment emerged as the most suitable combination for okra growth in this study, exhibiting the highest stem diameter, leaf count, photosynthetic characteristics, and yield (201.3 g). Notably, this yield was 67.8% higher than the lowest treatment (N2W3), signifying a significant improvement.

Compared to fluctuating soil water (FW) conditions, stable soil water (SW) can increase plant water use efficiency (WUE) and improve crop growth and aboveground yield. It is unknown, however, how stable and fluctuating soil water affect root vegetables. Here, the effects of SW and FW were studied on cherry radish in a pot experiment, using negative pressure irrigation and conventional irrigation, respectively. The assessed effects included agronomic parameters, physiological indices, yield, quality and WUE of cherry radish. Results showed that under similarly average soil water contents, compared with FW, SW increased plant photosynthetic rate, stomatal conductance and transpiration rate, decreased leaf proline content by 13.7–73.3% and malondialdehyde content by 12.5–40.0%, and increased soluble sugars content by 6.3–22.1%. Cherry radish had greater biomass accumulation and nutrient uptake in SW than in FW. Indeed, SW increased radish output by 34.6–94.1% with no influence on root/shoot ratio or root quality. In conclusion, soil water stability affected directly the water physiological indicators of cherry radish and indirectly its agronomic attributes and nutrient uptake, which in turn influenced the crop biomass and yield, as well as WUE. This study provides a new perspective for improving agronomy of root crops and WUE through managing soil water stability.

Uneven rainfall in the context of global warming can cause soil moisture fluctuation (SMF) that harm crop growth, and it is not yet known whether nitrogen (N) can mitigate the harm caused by the strong SMF. This paper uses okra as a test subject and sets three SMFs of 45–55% FC (W₁), 35–65% FC (W₂), and 25–75% FC (W₃) and three N applications of 0 kg hm^− 2 (N₀), 110 kg hm^− 2 (N₁), and 330 kg hm^− 2 (N₂) to investigate the effects of SMF and N application on physiological and biochemical aspects of okra. The results showed that okra stem diameter, number of leaves, photosynthesis characteristics, antioxidant enzyme activity, and yield were the highest under N₁ treatment and considerably greater than under N₀ and N₂ treatments; stomatal density, antioxidant enzyme activity, malondialdehyde content, and proline content of okra leaves were the highest under W₃ treatment, indicating that the plants were subjected to duress under W₃ treatment; the N₁W₁ treatment had the highest okra stem diameter, leaf number, photosynthetic characteristics, and yield, including a yield of 201.3g, which was higher than the lowest treatment (N₂W₃), a significant increase of 67.8%; W₃ was detrimental to okra growth, while the agronomic traits and yields of okra in the N₁ treatment were higher than those in the N₀ and N₁ treatments, indicating that the crop damage caused by W₃ could be mitigated by the appropriate amount of N application.