Residual phosphate fertilization and inoculation of Bacillus sp. and Azospirillum sp. in the early development and phosphorus use efficiency of sugarcane

Abstract

Phosphorus (P) is a limiting nutrient for sugarcane development in Brazilian tropical soils. However, there is evidence that phosphate-solubilizing bacteria (PSB) can improve plant development and P acquisition. A pot experiment was conducted to investigate the interaction between residual P fertilization and inoculation of Bacillus sp. and Azospirillum sp. on early development and P use efficiency traits of sugarcane plants (Saccharum spp., var. RB867515) grown in a sandy clay loam Oxisol from Brazilian Cerrado. Sugarcane seedlings were transplanted into soil containing three levels of residual P availability (low, medium and high) and subjected to three inoculation treatments with PSB [control (uninoculated plants); plants inoculated with B. megaterium (BRM119) and B. subtilis (BMF2484) or plants inoculated with A. brasilense (Ab-V5 and Ab-V6) and A. amazonense (BR11145)], arranged in a 3×3 factorial with four replicates. Results: Under low and medium residual P availability, plants inoculated with Bacillus sp. and Azospirillum sp. strains have greater plant height, number of tillers, leaf area, shoot dry matter, root dry matter, P uptake efficiency and physiological P use efficiency when compared to uninoculated plants, respectively. These results show that the inoculation of Bacillus sp. and Azospirillum sp. can be a sustainable agricultural practice to be recommended for sugarcane cropping. However, Bacillus sp. and Azospirillum sp. strains have reduced phosphate solubilization and mineralization potential when applied to tropical soil with high available P concentration. Nevertheless, the physiological basis of how high soil P availability affects the phosphate solubilization capacity of these bacteria remains unknown.