Carbon dioxide (CO₂) is recognized as key part of evaluating the soil environment, and the soil respiration rate is an effective indicator of CO₂ emission. To explore the influence and coupling mechanism of irrigation on the soil respiration of millet farmland in the Northern Shanxi Province in China, conventional rainfed (CK) and supplementary irrigation (W1) at the late jointing stage were conducted. The soil respiration rate and carbon emission flux in millet farmland under different treatments were observed. The relationship between soil respiration rate and soil physical–chemical properties and the crop growth index was further analyzed. The result showed that the soil respiration rate and carbon emission flux of W1 were higher than those of CK treatment. The comparison of the linear regression correlation between soil respiration rate and soil physical–chemical properties revealed that the major regulating factors of the soil respiration rate were soil moisture (10.6%), soil temperature, and finally soil organic matter content. There are uncertainties regarding the soil moisture content variation range in soil respiration. Moreover, supplementary irrigation promoted the growth indexes, yield, and irrigation water use efficiency in millet farmland. Further research with less irrigation treatment is necessary for exploring an optimization model of water use efficiency and low carbon dioxide emissions in millet fields, which would be helpful to realize agricultural water utilization and a “carbon peak” in the sense of farmland.

Arundo donax L. (giant reed) is a perennial rhizomatous grass with high drought and salinity tolerance, making it a promising low-input bioenergy crop. However, the understanding of the combined effects of irrigation and nitrogen application in salinized soil on physiological adaptations and biomass allocation is still limited. In this study, we conducted a three-factor orthogonal pot experiment with four levels per factor in 2023 and 2024 as follows: salinity (S0: non-saline, S1: low salinity, S2: moderate salinity, S3: high salinity); irrigation amount (W0: 605, W1: 770, W2: 935, W3: 1100 mm); and nitrogen application (N0: 0, N1: 60, N2: 120, N3: 180 kg/ha). This resulted in 14 irrigation-nitrogen-salinity combined treatments. The results showed the following: (1) Irrigation, nitrogen and salinity significantly affected leaf dimensions, photosynthetic rate, plant height, biomass allocation and dry matter of the total plant (p < 0.05). (2) Significant coupling interactions were observed between salinity and irrigation, as well as between nitrogen and irrigation, affecting leaf morphology, plant height, leaf dry matter and total biomass accumulation; a coupling interaction of salinity and nitrogen was found to affect the leaf area, root, stem and leaf dry weight. (3) The S0N2W2 treatment produced the highest dry biomass, which was 2.2 times higher than for the S3N2W2 treatment. (4) Under moderate-salinity conditions (S2), biomass allocation favored stems and leaves, whereas under high-salinity conditions (S3) biomass allocation shifted towards leaves, followed by stems and roots. A combination of 935 mm irrigation amount and 120 kg/ha nitrogen (N2W2) under S1 and S2 is recommended to optimize biomass production. Our study provides practical irrigation and nitrogen management strategies to enhance A. donax cultivation on marginal saline lands, supporting climate-resilient bio-economy initiatives.

Agro-photovoltaics (APV) or agrivoltaic systems integrate crop cultivation with solar energy production, offering a promising solution through the dual-use of land. This two-year study (2023 and 2024) examined the effects of an APV system on rice production. The results indicated that APV arrays created spatially variable light environments, with shadow lengths following predictable solar azimuth patterns and cloudy conditions mitigating shading effects through enhanced diffuse light. Compared with CK (non-shadow area), inter-panel plots (BP) maintained 77% photosynthetic efficiency and 85.4% plant height, whereas the areas beneath the panel showed a significant decrease in the relative chlorophyll content (SPAD values), photosynthesis rates, and yield. BP plots preserved a 78% fruiting rate through adaptive stomatal regulation, whereas LP zones (directly under the low eave) exhibited 35% higher intercellular CO₂ because of the limited assimilation in shading. Rice yield losses were correlated with shading intensity, driven by reduced panicles and grain filling. Moreover, the APV system achieved a high land equivalent ratio of 148–149% by combining 65–66% rice yield with 82.5% photovoltaics output. Based on the microenvironment created by the APV system, optimal crop types and fertilisation are essential for enhancing agricultural yields and improving land use efficiency.

The water–zeolite amount–burial depth coupling regulation strategy of high-quality and high-yield tomatoes was explored with drip irrigation under mulch. Greenhouse planting experiments were performed to monitor and analyze the tomato growth, physiology, yield, quality, and water use efficiency (WUE). The suitable amounts of the water–zeolite amount–burial depth for the tomato growth were determined through the analytic hierarchy process (AHP). The results showed that the effects of increasing the water of the intercellular CO₂ concentration (Ci), nitrate content (NO), vitamin content (VC), and soluble solids (SS), increasing the WUE, increasing the zeolite amount of the NO, and increasing the zeolite burial depth of the Ci and SS, were inhibited. The effects of increasing the zeolite amount of the plant height (Kh), stem thickness (Kt), total root length (Rl), total root volume (Rv), root average diameter (Rd), net photosynthetic rate (Pn), stomatal conductivity (Gs), organic acid (OA), VC, yield (Ay), and WUE, and of increasing the zeolite burial depth of the Kh, OA, dry matter quality (Ad), and WUE, were promoted first and then inhibited. The other indicators showed a positive response to increasing the water, zeolite amount, and burial depth. The influence of the water (W), zeolite amount (Z), and zeolite depth (H) on the Kt, Tr, Rl, and Rd, was W > H > Z, and that of the Kh, Gs, Pn, Ci, Ra, Rv, OA, VC, NO, SS, Ad, Ay, and WUE was W > Z > H. The order of weight of each index, based on the AHP, is as follows: Ay > WUE > NO > OA > Ad > Kh > Kt > VC > SS > Pn > Rv > Rd > Tr. The highest comprehensive score was W_70–90Z₆H₁₅, and the most suitable water conditions for the tomato planting under drip irrigation were 70–90% field capacity, 6 t/hm² zeolite, and 15 cm depth of zeolite.

The study delves into the prevailing focal points and developmental trends within the international sphere of crop root research under drip irrigation. It leverages the Web of Science core database and employs VOSviewer for a systematic review of the literature spanning 2001 to 2022. The analysis encompasses publication counts, publishing journals, contributing authors, research institutions, and keywords. Findings indicate that research on root systems under drip irrigation has become a notable area of interest in the field of irrigation, attracting global scholarly attention. There is a marked upward trend in publication output, with institutions in China and the United States taking on central roles. Journals like Agricultural Water Management and Acta Horticulturae are key publication venues, with Vadose Zone Journal being notable for high-impact articles. The research primarily involves agronomy, water resources, and horticulture, focusing on yield enhancement through drip irrigation, root distribution under various techniques, crop quality in response to partial root-zone drying, and irrigation scheduling model development. Scholars like Jiri Simunek and Yaohu Kang have made substantial contributions. The field’s established framework calls for continued international collaboration to drive further innovation. The identified trends and parameters can be a valuable reference for researchers, policymakers, and practitioners, guiding efforts to optimize agricultural productivity and resource use.

Arundo donax L. (giant reed) is a perennial rhizomatous grass with high drought and salinity tolerance, making it a promising low-input bioenergy crop. However, the combined effects of irrigation and nitrogen application in salinized soil on physiological adaptations and biomass allocation are still limited. In this study, we conducted a three-factor orthogonal pot experiment with four levels per factor in 2023 and 2024: salinity (S0: non-saline, S1: low salinity, S2: moderate salinity, S3: high salinity); irrigation amount (W0: 605, W1: 770, W2: 935, W3: 1100 mm); and nitrogen application (N0: 0, N1: 60, N2: 120, N3: 180 kg/ha). This resulted in 14 irrigation-nitrogen-salinity combined treatments. The results showed the following: (1) Irrigation, nitrogen and salinity significantly affected leaf dimensions (length, width, area and leaf elongation rate, specific leaf weight), photosynthetic rate, plant height, biomass allocation and dry matter of total plant (p < 0.05). (2) Significant coupling interactions were observed between salinity and irrigation, as well as between nitrogen and irrigation, affecting leaf width, leaf elongation rate,plant height,leaf dry matter and total biomass accumulation; coupling interaction of salinity and nitrogen were found to have effect on leaf width, leaf area, leaf fresh weight, root, stem and leaf dry weight. (3) The S0N2W2 treatment produced the highest dry biomass (44.76 ± 0.68 g/plant), which was 2.2 times higher than the S3N2W2 treatment (20.13 ± 0.50 g/plant). (4) Under moderate salinity conditions (S2), biomass allocation favoured stems (42.70%, mean values of 2023 and 2024) and leaves (39.53%, mean values of 2023 and 2024), whereas under high salinity conditions (S3) biomass allocation shifted towards leaves, followed by stems and roots. A combination of 935 mm irrigation amount and 120 kg/ha nitrogen (N2W2) in S1 and S2 is recommended to optimise biomass production. Our study provides practical irrigation and nitrogen management strategies to enhance A. donax cultivation on marginal saline lands, supporting climate-resilient bio-economy initiatives.