Abstract:

To address the issue of phosphorus surplus and environmental risks caused by excessive phosphorus fertilization in vegetable fields, this study explored the effects of reduced phosphorus fertilizer application combined with phosphorus-solubilizing bacteria on the improvement of acidic P-rich soil and the growth of mustard, providing a scientific basis for sustainable vegetable production. In this study, a pot experiment was conducted with four treatments: conventional P, 50% conventional P, conventional P + phosphate-solubilizing bacteria, and 50% conventional P + phosphate-solubilizing bacteria, to compare their effects on the properties of acidic P-rich soil, the nutrient utilization and growth of mustard (Brassica juncea). Correlation analysis revealed that the total exchangeable bases cations in soil were positively correlated with soil nutrient parameters such as alkali-hydrolyzable nitrogen, available potassium, available P, available zinc and available copper, while negatively correlated with exchangeable aluminum. High acidity and phosphorus-rich soil conditions were detrimental to mustard growth and severely inhibited its nutrient absorption. Conversely, reducing P application enhanced the available K in bulk soil and improved the root traits, the utilization of N, P and K in mustard, reduced soil nutrient surplus, promoted the growth of mustard, and increased the content of soluble sugars and vitamin C in mustard stems and leaves. Adding phosphate-solubilizing bacteria could enhance the nutrient utilization, biomass and quality of mustard greens. Especially, the combined use of conventional phosphorus and phosphate-solubilizing bacteria, could further improve the properties of non-root zone soil, increase the root surface area, root length ratio, total root length, fine root length and coarse root length of mustard greens, and enhance their ability to absorb nutrients from the root zone soil, reduce the allocation of dry matter to the underground roots and promote the increase in the above-ground yield of mustard greens. Reducing the amount of phosphate fertilizer and adding phosphate-solubilizing bacteria not only promoted the absorption of nutrients by mustard greens but also reduced the content of base ions in the root zone soil, increased the risk of aluminum toxicity in the root zone of mustard greens. In comparison, the conventional phosphate fertilizer combined with phosphate-solubilizing bacteria model showed the best application potential in acidic phosphorus-rich soil.

Key words: mustard, acidic phosphorus-rich soil, soil exchangeable base cations, phosphorus-solubilizing bacteria, nutrient use efficiency, root trait