The effects of different types of phosphate fertilization on the phosphorus (P) adsorption-desorption in low-P red soil remain unclear. A field plot location test was carried out, and fifteen red soil samples were collected at depths of 0–20 cm from five phosphate fertilizers (CK—no-phosphate, SSP—single superphosphate, CMP—calcium magnesium phosphate, MAP—monoammonium phosphate, and DAP—diammonium phosphate) after the maize was harvested to evaluate the soil physicochemical properties, P adsorption, and desorption characteristics. The structural equation model (SEM) and adjacent tree method (ABT) were used to quantitatively analyze the relative contribution of P adsorption and desorption. The yield, P accumulation, and the P use efficiency of maize were the highest under SSP and CMP treatments. The P adsorption amount was CK > DAP > MAP > CMP > SSP, and the P desorption amount was DAP > MAP > CMP > SSP > CK. Compared with the CK treatment, P adsorption of other P treatments reduced by an average of 21.4%, while P desorption increased by 154.8%. The effect of different types of phosphate fertilizers on soil P adsorption was mainly through regulation of soil organic matter (SOM) and Olsen P, and the effect on soil P desorption was mainly through regulation of SOM and CaCO₃. Al₂O₃ had the greatest effect on P adsorption with a relative contribution rate of 31.52%, and SOM had the greatest effect on P desorption with a relative contribution rate of 53.04%. SSP and CMP treatments had an optimal matching with acidic red soil, which can promote P adsorption, effectively slow down P loss, improve P utilization, and increase crop yield.

Phosphorus (P) application can enhance soil P availability and alter P fractions. However, the P accumulation and transformation of different P sources in low-phosphorus red soil remain unclear. Two-year (2018–2019) field experiments were conducted to investigate the effects of five P source treatments (CK—no phosphorus; SSP—superphosphate; MAP—calcium–magnesium phosphate; DAP—monoammonium phosphate; and CMP—diammonium phosphate) on the P accumulation of maize and soil P fractions in low-P red soil using the Hedley Sequential Method. The results showed that P application significantly increased P uptake, Olsen-P, total phosphorus, and most of the soil P fractions. Compared to the CMP, MAP, and DAP treatments, SSP had a relatively higher P accumulation and labile P pool, with a slightly lower moderately labile P pool. The SSP treatment mainly increased soil-available P content and crop P uptake by increasing the labile P pool (resin-P and NaHCO₃-Pi) and reducing the moderately labile P pool and non-labile P pool. The P activation coefficient (PAC%) and Olsen-P were positively correlated with labile P (resin-P, NaHCO₃-Pi, and NaHCO₃-Po) and moderately labile P (NaOH-Pi and 1 M HCl-Pi) and negatively correlated with Fe₂O₃ and Al₂O₃. The results suggest that SSP has a priority effect on the crop P uptake and soil P availability in low-P red soil.

Studying the effects of maize and soybean intercropping for improving the maize yield and sustaining stability of the maize yield under different phosphate (P) application rates in red soil is crucial for promoting maize productivity, improving soil fertility and optimizing P nutrient management in southwest China. The objective of this study was to evaluate the dynamic changes in maize yield, yield stability and soil fertility under monoculture and intercropping maize with different P application rates. A six-year field experiment was conducted from 2017 to 2022 to investigate the effects of maize intercropping with soybean on the yield stability and sustainability of maize according to the changes in the maize yield, biomass, partial land equivalent ratio of yield (pLERY), actual yield loss index (AYL), contribution rate of soil capacity and fertilizer (SCR, SFCR) over time, as well as the differences in the coefficient of variation (CV) and sustainable yield index (SYI) at four P application rates (0 kg P₂O₅ ha⁻¹, P0; 60 kg P₂O₅ ha⁻¹, P1; 90 kg P₂O₅ ha⁻¹, P2; and 120 kg P₂O₅ ha⁻¹, P3) based on the two-factor randomized block design. The linear-platform model was utilized to simulate the relationship between the grain yield, the SYI and the amount of P fertilizer under different P application rates. The maize yield in intercropping was significantly superior to the maize yield in monoculture throughout the entire six-year experiment. For all planting years, the yield and biomass of the intercropping were higher than those of the matched monoculture average by 56.0% and 56.1%, respectively. Intercropping had an advantage of pLERY and AYL for maize. Otherwise, intercropping reduced the CV by 30.8% and 39.1% and increased the SYI by 39.4% and 23.0% in P0 and P3 compared with the matched monoculture, respectively. For all planting years, the average SFCR in intercropping treatment was higher than that in monoculture treatment. The linear-plateau model fitted showed that intercropping increased the yield and SYI by 19.8% and 40.7% on the platform and reduced the P application rate by 37.8% and 11.9% at the inflection point, respectively. These results demonstrate that maize and soybean intercropping could achieve a higher yield, a higher yield stability and an SYI with a lower P input than monoculture. Maize and soybean intercropping could be a sustainable practice for promoting the maize productivity and the yield sustainability in the red soil of southwest China.

This study investigated the effects of phytase (PHY) and phosphate-solubilizing Bacillus (PSB) isolates on maize growth and phosphorus (P) acquisition in low-P red soil, under conditions with or without organic P application. A pot experiment demonstrated that the combined application of organic P with exogenous PHY and PSB significantly enhanced maize agronomic traits, root morphology, rhizosphere properties, and P mobilization. Compared to the P-free control, organic P application alone increased plant height, stem diameter, dry matter, and P uptake by 9.9%, 5.4%, 23.2%, and 34.6%, root surface area, volume, and branching increased by 39.7%, 26.7%, and 44.7%, while average root diameter decreased by 19.5%, respectively. Exogenous phytase treatment was more effective than bacterial adding in enhancing P activation and uptake, increasing maize P absorption by 55.4% and 47.3% with and without sodium phytate, respectively. Redundancy analysis indicated positive correlations between root traits (root tips, surface area, volume) and P uptake, and between Olsen-P, resin-P, NaHCO₃-Pi, and enzyme activities. The results suggest that combining organic P with exogenous phytase effectively mobilizes native soil P pools, improves maize growth, and increases P use efficiency, offering a sustainable strategy for P management in low-P red soils.

Dendrobium officinale (D. officinale) is an important medicinal horticultural crop. Its wild resources are threatened by over-exploitation. Fertilization regimes that balance yield and medicinal quality are urgently required for its artificial cultivation. This study aimed to investigate the effects of reduced chemical fertilizer combined with organic fertilizer on the yield and quality of D. officinale, and screen the optimal combined fertilization pattern, so as to provide a theoretical basis for standardized fertilization in D. officinale cultivation. A bed-cultivation experiment was carried out in greenhouse. Seven treatments were set up, including no fertilizer application (CK), sole chemical fertilizer (CF), 20% organic fertilizer substitution for chemical fertilizer (T20), 40% organic fertilizer substitution for chemical fertilizer (T40), 60% organic fertilizer substitution for chemical fertilizer (T60), 80% organic fertilizer substitution for chemical fertilizer (T80), and single organic fertilizer application (OM). Plant growth traits, yield, active ingredients, protein and amino acid components of D. officinale were determined. The membership function method was adopted for comprehensive evaluation of all treatments. Fertilization significantly improved the growth traits, yield and quality of D. officinale. Compared with CK, stem length, stem diameter and yield under fertilized treatments increased significantly by 15.5%-60.3%, 34.2%-64.7% and 65%-143.2%, respectively; dendrobine, polyphenols and alcohol-soluble extract contents increased significantly by 21.2%-83.7%, 14.0%-49.1% and 10.8%-26.9%, respectively. The highest plant growth and yield were observed under sole chemical fertilizer treatment. With the increase of organic fertilizer substitution ratio, plant growth and yield decreased gradually, while medicinal active ingredients including dendrobine, polysaccharides and flavonoids showed a trend of rising first and then falling. A total of 17 amino acids were detected in all treatments. T40 and T60 treatments significantly increased total amino acids, essential amino acids, as well as contents of medicinal, umami and bitter-tasting amino acids, whereas excessive proportion of organic fertilizer led to the decline of amino acid contents. Most growth, quality and amino acid indicators showed significant or extremely significant positive correlations with each other. The comprehensive evaluation order by membership function method was T40 > T60 > CF > T20 > T80 > OM > CK, and T40 obtained the highest comprehensive evaluation value. Sole chemical fertilizer contributes to yield increase of D. officinale, while combined application with organic fertilizer improves its medicinal quality. The 40?% organic substitution scheme provides a feasible fertilization strategy for high-quality greenhouse production of this medicinal horticultural plant.

Phosphorus (P) is a vital non-renewable macronutrient that is frequently immobilized by chemical fixation in acidic and calcareous soils. However, the specific transformation processes of different P sources across these different soil types remain poorly understood. A 120-day incubation experiment was conducted in a completely randomized design with three replicates using acidic and calcareous soils from Myanmar to evaluate six treatments: single superphosphate (SSP), diammonium phosphate (DAP), triple superphosphate (TSP), ammonium polyphosphate (APP), calcium phytate (CP), and an unfertilized control (CK). The modified Hedley fractionation method was employed to investigate the dynamic transformation of soil P fractions, the rate of available P transformation, and the relationship between soil transformation and soil P availability under different P-fertilizer sources. In both soils, SSP, DAP, and TSP provided high initial P release (249.7%, 239.9%, and 234.1%) in acidic soil and (159.5%, 170.8%, and 161.4%) calcareous soil, which peaked on day 10 compared to CK (p < 0.001) before rapidly declining. P transformation in calcareous soil declined more sharply than in acidic soil from the 10th day to the 15th day (especially in SSP and TSP, −11.3 and −16.9 mg kg⁻¹), indicating a higher rate of P immobilization in calcareous soil. Conversely, the delayed peak of APP (day 60) and the stability of CP indicate resistance to immediate soil fixation. Notably, overall effectiveness depended on soil type: SSP performed best in acidic soil and DAP in calcareous soil.