The study, led by Pengcheng Luo and Lijun Su of Xi’an University of Technology in Shaanxi, China, together with colleagues including Quanjiu Wang and Mingjiang Deng, was conducted over the 2024 and 2025 growing seasons on saline farmland in northwest China, a region where secondary salinization has long undermined irrigation agriculture. The research team set out to test a concept they describe as coordinated soil and plant regulation: rather than treating the soil and the crop as separate problems, they asked whether improving the below-ground environment and the above-ground physiology at the same time would produce benefits that neither intervention could achieve alone.

The experimental design was deliberately systematic. Three dilutions of a foliar biostimulant, labeled B1 at 600-fold, B2 at 500-fold, and B3 at 400-fold, were factorially combined with five rates of organic fertilizer, designated C1 through C5 and ranging from 60 to 140 kilograms per hectare, alongside an untreated control plot. This factorial layout meant the researchers could disentangle the contribution of each input and, crucially, detect interaction effects where the combination outperformed the sum of its parts. Randomized complete block design, a standard safeguard against field heterogeneity, ensured that differences in soil salinity or fertility across the experimental site would not masquerade as treatment effects.

The standout result came from the intermediate combination, B2C3, which paired the 500-fold biostimulant dilution with the mid-range organic fertilizer rate. Compared with the untreated control, this treatment maintained greater soil water storage in the 0 to 40 centimeter profile, the layer where most of maize’s active roots reside, although the magnitude of that advantage shifted with sampling stage and between the two years. More dramatic was the effect on salinity: at physiological maturity, the depth-weighted mean salinity of the 0 to 40 centimeter layer was 38.6 percent lower than the control in 2024 and 32.4 percent lower in 2025. Those are not marginal numbers; they represent a substantial reduction in the osmotic burden that salt places on the crop precisely when grain filling demands maximum water uptake.

The physiological consequences were equally pronounced. Maximum net photosynthetic rate, a measure of the leaf’s peak capacity to convert light energy into sugars, increased by 67.5 to 69.3 percent under the best combination. Salt stress typically suppresses photosynthesis through multiple channels: osmotic stress closes stomata and restricts carbon dioxide entry, ionic stress disrupts chloroplast function, and secondary oxidative damage degrades the photosynthetic machinery itself. By easing the salinity of the root zone, the organic fertilizer plausibly reduced the osmotic penalty at its source, while the foliar biostimulant acted directly on the leaf, sustaining stomatal conductance, transpiration, and intercellular carbon dioxide concentrations. The study tracked these parameters, along with leaf area index, light saturation and compensation points, and dry matter accumulation, building a picture of a crop that was not merely surviving salinity but photosynthesizing at something close to its unstressed capacity.

The payoff appeared at harvest. Grain yields under B2C3 reached 11.75 tonnes per hectare in 2024 and 11.98 tonnes per hectare in 2025, representing increases of 26.2 to 30.4 percent over the untreated control. For context, yields above 11 tonnes per hectare on saline farmland are remarkable; many salt-affected fields produce a fraction of that. The consistency of the yield advantage across two consecutive seasons matters as much as its size, because single-year results in field agronomy are notoriously vulnerable to weather quirks. Here, the treatment effect held in both years, suggesting a robust mechanism rather than a lucky season.

What might that mechanism be? The authors are careful to note that the processes producing the soil water and salinity differences were not fully resolved by their measurements, an honest caveat that distinguishes this work from overreaching claims. But the plausible pathways are well grounded in the broader literature. Organic amendments are known to improve soil aggregation, increase water-holding capacity, and enhance microbial activity, all of which can alter how water and salts move through the profile. Better aggregated soils hold more plant-available water and can facilitate the leaching or redistribution of salts away from the active root zone. Humic substances and microbial metabolites released during decomposition can also chelate ions and moderate the osmotic stress experienced by roots. Meanwhile, foliar biostimulants, which in commercial practice include seaweed extracts, humic and fulvic acids, and plant growth-promoting compounds, can prime the plant’s own stress-response machinery, improving antioxidant defenses and hormonal signaling under abiotic stress.

The factorial results also carry a practical message about dosage. The winning combination was not the highest rate of either input but the middle dilution of biostimulant paired with the mid-range fertilizer rate. This pattern echoes a recurring theme in biostimulant research: these compounds often show hormetic dose responses, where moderate application stimulates and excessive application does nothing or even harms. For farmers weighing input costs against returns, the finding that an intermediate, not maximal, application delivered the best yield is economically significant. It suggests that the technology could be adopted without the expense of pushing fertilizer rates to the top of the tested range.

The broader context makes the study timely. Saline and sodic soils already cover hundreds of millions of hectares worldwide, and the area is growing as intensive irrigation, climate-driven evaporation, and seawater intrusion degrade coastal and inland aquifers. Traditional reclamation, flushing salts with large volumes of good-quality water, is increasingly untenable where water itself is the scarce resource. That has pushed researchers toward biological and agronomic approaches: salt-tolerant root systems, microbial inoculants, organic amendments, and biostimulants that help crops tolerate what cannot easily be washed away. A recent meta-analysis of organic amendment inputs on saline-alkali land found generally positive effects on soil quality and crop productivity globally, and other studies have documented how seaweed-based biostimulants reshape rhizosphere microbial communities in ways that benefit maize growth. The new work adds a systems-level twist by showing that soil-side and plant-side interventions can be combined productively.

Caveats remain, and the authors flag them clearly. The experiment was conducted at a single site under specific saline farmland conditions, and the tested fertilizer rates and biostimulant dilutions define the boundary of the recommendation; B2C3 was the best performer within that range, not a universal optimum. The study also measured outcomes rather than mechanisms, so follow-up work tracing water and salt fluxes, root architecture, and microbial community shifts would strengthen the causal story. Still, the headline numbers, roughly a third less salt in the root zone, two-thirds more peak photosynthetic capacity, and a quarter to a third more grain, are the kind of results that translate quickly into field trials elsewhere. For the millions of hectares of salt-stressed irrigated land where every tonne of grain is hard-won, a cheap, two-pronged treatment that works with the soil and the plant simultaneously may prove one of the more practical tools to emerge from salinity research in years.

Subject of Research: Combined organic fertilizer and foliar biostimulant effects on maize growth and soil water-salt conditions in saline farmland

Article Title: Integrated application of organic fertilizer and a foliar biostimulant improves root-zone water–salt conditions, photosynthesis, and yield of maize (Zea mays L.) under saline farmland conditions

Article References: Luo, P., Su, L., Lei, Q., Chen, H., Sun, Y., Shan, Y., Deng, M., & Wang, Q. (2026). Integrated application of organic fertilizer and a foliar biostimulant improves root-zone water–salt conditions, photosynthesis, and yield of maize (Zea mays L.) under saline farmland conditions. Plant and Soil. https://doi.org/10.1007/s11104-026-09051-z

Image Credits: AI Generated

DOI: 10.1007/s11104-026-09051-z

Keywords: maize, saline farmland, organic fertilizer, foliar biostimulant, soil salinity, photosynthesis, grain yield, soil water storage, salt stress, root zone, Plant and Soil, field experiment