Correlations between the phosphorus fractions of soil and rhizosphere microbiome of sugarcane

Phosphorus is essential for life, but it is often limited in soil due to its high reactivity. Up to 80% of added phosphorus can be immobilized as low-labile compounds. Plants can solubilize non-labile phosphorus through organic acids synthesized by soil microorganisms, which also contribute to the mineralization of organic phosphorus through the production of enzymes. This study aimed to correlate changes in organic and inorganic phosphorus fractions in the rhizosphere of sugarcane plants with their microbiome structure and diversity. A total of 74 rhizosphere samples were analyzed. Plants were grown for 180 days in microcosms with different phosphorus sources, both with and without filter cake. The different phosphorus fractions were correlated with molecular data based on partial sequencing of the 16S rRNA gene. At 60 days, there was greater overall bacterial diversity, benefiting copiotrophic bacteria. At 120 days, diversity decreased in response to reduced labile phosphorus content, benefiting oligotrophic bacteria. The association of filter cake with monoammonium phosphate showed evidence of increased mineralization on the soil surface, with a strong correlation with an increase in Beta-Proteobacteria population. In general, filter cake changed the solubilization and availability of phosphorus in mineral sources, contributing to increases in organic and inorganic phosphorus fractions. These results showed that bacteria participate in processes that make phosphorus available in soil and that filter cake can modulate these transfers beneficially to plants by stimulating the activity of phosphorus-solubilizing microorganisms and mineralizing soil organic matter.

磷是生命活动必需的营养元素，但由于其高反应活性，在土壤中往往有效性受限。外源施加的磷中最多有80%会被固定为低活性态化合物。植物可通过土壤微生物合成的有机酸溶解非活性磷，而微生物亦可通过分泌酶类促进有机磷的矿化过程。本研究旨在关联甘蔗根际（rhizosphere）有机磷与无机磷组分的变化与其微生物组（microbiome）结构及多样性。本研究共分析了74份根际样品。供试甘蔗植株在添加不同磷源（添加与不添加滤饼）的微宇宙培养体系中培养180天。基于16S rRNA基因（16S rRNA gene）的部分测序数据，将不同磷组分与微生物群落分子数据进行关联分析。培养60天时，细菌整体多样性更高，利于富营养型细菌（copiotrophic bacteria）的生长繁殖；培养120天时，由于活性磷含量降低，细菌多样性下降，此时寡营养型细菌（oligotrophic bacteria）占据优势。滤饼与磷酸一铵（monoammonium phosphate）配施处理在土壤表层表现出增强的矿化作用，与β-变形菌门（Beta-Proteobacteria）种群丰度的提升存在显著相关性。总体而言，滤饼可改变矿物源磷的溶解过程与有效性，提升土壤中有机磷与无机磷组分的含量。本研究结果表明，细菌参与了土壤中有效磷活化的相关生物学过程；而滤饼可通过激发溶磷微生物的活性、促进土壤有机质矿化，正向调控磷素转化过程，从而有益于植物对磷素的吸收利用。