Resumen
- Sugarcane industry generates large amounts of waste and filter cake and ashes are the main solid wastes. One of the technologies developed for the management of these wastes is composting with the addition of rock phosphate and animal manure. The organic compost originated from these sources can substitute for several macro and micronutrients, which, in conventional agriculture, generally come as industrial fertilizers. However, such compost does not always satisfy the plant’s need for P, a nutrient that has little mobility in its ionic form, and is easily fixed and precipitated in tropical soils. Microorganisms play an essential role in soil processes such as the P cycle and P transfer to the plant. Studying the microbial roles also is mandatory to improve P uptake in this environment. Sugarcane is one of the crops that needs large amounts of phosphate fertilizers to maintain a high productivity, and we constantly look for a new way to gain a better understanding of plant productivity, especially with regard to incrementing available P in soil. P-mobilizing bacteria (PMB) can increase P availability for plants in soil. Thus, our objective was to evaluate the effect of PMB on sugarcane growth and soil bacterial communities when we applied these PMB on sugarcane seedlings, jointly with distinct P sources. We hypothesized that, in certain treatments, PMB would liberate more soluble P to improve plant growth while, concomitantly, modifying the bacterial community in soil. Therefore, we conducted a greenhouse experiment with different P sources (organic compost, rock phosphate, compost + rock phosphate, triple superphosphate (TSP), triple superphosphate + compost, and a control without P). We also tested two bacterial consortia as inoculants: We evaluated P content in sugarcane shoots after 60 days of growth and used thesequencing technique MiSeqTM System (Illumina) platform to determine the effect of the treatment on soil bacterial communities. Application of inoculants had a positive effect on P accumulation in plants regardless of P source. However, the largest increases in P occurre when using organic compost as P source, together with PMB inoculation. Using compost as P source and applying inoculant 2 we got the greatest increment, corresponding to an increase of up to 28.91% in the shoot P, when compared to treatments without inoculation. Inoculantapplication changed the structure of bacterial communities compared to un-inoculated treatments, particularly in treatments that showed a more efficient use of P. The bacterial strains used in this study as inoculants (especially inoculant 2) changed the structure of the natural soil Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017 bacterial communities, due to their ability to mobilize P, therefore improving the efficiency of P and other nutrients, such as N and K, in sugarcane. The results confirmed our hypothesis. We could demonstrate that both PMB consortia modified the bacterial community and improved the absorption of P by sugarcane. These results open a new perspective for the use of bacterial consortia jointly with organic compost in soils.