Homogeneous high-phosphorus supply is more effective than heterogeneous application or Bacillus subtilis inoculation for short-term maize growth and phosphorus uptake in loess soil

Abstract

Low phosphorus (P) availability limits sustainable crop production on the Loess Plateau. Heterogeneous nutrient supply and phosphate-solubilizing bacteria have been proposed to improve P availability, yet their combined effects remain unclear. A greenhouse pot experiment was conducted with maize in the loess soil under two application methods (homogeneous vs heterogeneous), two P supply levels (50 and 200 mg P kg−1), and with live or inactivated Bacillus subtilis to assess plant growth, P uptake and bacterial community responses. After 47 days, heterogeneous P supply induced P enrichment in patch soil and increased the P activation coefficient by 216%, but reduced shoot biomass by 23%, as well as shoot and root P content by 42% and 35% respectively. Bacillus subtilis inoculation promoted dry mass by only 36% under homogeneous supply and 33% under heterogeneous supply, with diminished effects under high P. Heterogeneous P supply significantly altered the bacterial community structure, and reduced the Shannon’s diversity index, with the diversity being negatively correlated with soil available P concentration. Even though heterogeneous supply can drive spatial redistribution of soil P and reshape microbial community, it failed to significantly improve plant P acquisition. Inoculation with Bacillus subtilis slightly enhanced root growth, but its benefit weakened under high P. Co-application of B. subtilis with P-fertilizer provided no additional benefit over P application alone. Therefore, homogeneous high-P supply remains the most effective approach for enhancing P uptake and promoting maize growth in loess soil in the short term.