Cadmium (Cd) contamination threatens human health and plant growth due to its accumulation in edible parts. The sole application of phosphorus-solubilizing bacteria (PSB), biochar (BC), and phosphorus (P) effectively mitigates Cd’s adverse effects in contaminated agricultural systems. However, further investigation into their combined impacts on Cd toxicity and maize (Zea mays) production is essential. This study evaluates the synergistic effects of PSB (10 g kg⁻¹ of Bacillus megaterium), BC (5% w/w), and P (0.8 g kg⁻¹) on soil properties and the morphological and physiological traits of maize cultivated in agricultural soil contaminated with Cd (20 mg kg⁻¹). The study revealed that Cd toxicity negatively impacts soil properties, reducing shoot and root biomass, lowering chlorophyll content, and heightening oxidative stress levels. Conversely, the combined use of P, PSB, and BC markedly improved soil properties, increasing the organic matter by 175.94%, available K by 87.24%, and available P by 306.93% compared to the control. This combination also improved maize growth metrics, with increases in aboveground dry biomass (92.98%), root dry biomass (110.33%), chlorophyll a (28.20%), chlorophyll b (108.34%), and total chlorophyll (37.17%). Notably, the treatment reduced Cd concentrations in maize leaves by 61.08% while increasing soil Cd levels by 31.12% compared to the control group. Overall, the synergistic effect of P-BC-PSB is an eco-friendly strategy for mitigating Cd toxicity in contaminated soil. However, further studies are required to explore its effects and molecular mechanisms on other crops.

Understanding how straw incorporation affects soil stoichiometry and biochemical processes is essential for improving soil fertility in dryland wheat systems on the Loess Plateau. We quantified effects of four wheat straw return rates [0 (W0), 3500 (W1), 7000 (W2), and 14,000 kg ha⁻¹ (W3)] on C-N-P stoichiometry, microbial biomass, active carbon fractions, and enzyme activities in a randomized block experiment in Dingxi, Gansu. Composite soil samples from 0–10, 10–20, and 20–30 cm were analyzed for soil organic carbon (SOC); total nitrogen (TN); total phosphorus (TP); microbial biomass C, N, and P; dissolved, particulate, and readily oxidizable organic C; and sucrase, urease, alkaline phosphatase, and catalase activities. Increasing straw input significantly increased SOC, TN, and TP across all depths, with W3 increasing them by up to 42, 33, and 24% relative to W0, respectively. Under W3, microbial biomass C and N more than doubled, and labile C fractions and enzyme activities increased by 35–80% compared with W0. Straw return also modified soil and microbial C:N:P stoichiometry, decreasing microbial C:N and C:N:P and increasing N:P, suggesting alleviated N limitation. Overall, moderate-to-high straw incorporation improved soil fertility and functioning, supporting straw return as a sustainable management practice for Loess Plateau drylands.

Soil microbial nutrient limitation is of great significance for the maintenance of soil fertility, the sustainability of plant growth, and the stability of the alpine meadow ecosystems, which are particularly sensitive to global climate change. This study aimed to explore the effects of soil extracellular enzyme activities on soil microbial nutrient limitation across three altitudinal gradients—low altitude (LA: 2900–3200 m above sea level (masl)), middle altitude (MA: 3200–3500 masl), and high altitude (HA: 3500–3800 masl)—in alpine meadows in the northeastern Qinghai–Tibet Plateau, using the method of ecological stoichiometry. The research results showed that soil nutrients mostly accumulate in the surface layer: with increasing altitude, soil organic carbon (SOC) and total nitrogen (TN) contents gradually increase (p < 0.05), and their contents at high altitude in the 0–20 cm soil layer are twice those at low altitude. The activities of β-1,4-glucosidase (BG) and β-1,4-N-acetylglucosaminidase (NAG) at high altitude are significantly 26.77% and 30.88% higher than those at low altitude, respectively. Linear regression analysis shows a significant positive correlation between soil nutrients and C/N/P-related enzymes after logarithmic transformation along the altitudinal gradient. Enzyme vector analysis revealed that in the alpine meadows at altitudes ranging from 2900 to 3800 masl, relative nitrogen limitation was widespread, while relative carbon limitation was more significant in both high-altitude and low-altitude regions (p < 0.05). Notably, this study did not account for the granulometric composition of the soil at the sampling sites. Nevertheless, it partially reveals the nutrient acquisition strategies of microorganisms across different altitudinal gradients, providing a theoretical basis for understanding nutrient cycling in alpine meadow ecosystems and addressing global change.