Effects of application of organic-inorganic compound fertilizers on microbial communities and enzyme activities in tropical paddy soil

Objectives We studied the effects of basal application of different rates of organic-inorganic compound fertilizer (OF) on rice yield and soil microbial community and enzyme activities in paddy soils, to provide a scientific basis for its efficient application.

Methods A field rice experiment was carried out for three seasons in Hainan Province. Five treatments were set up as no fertilizer (i.e., CK), conventional chemical fertilizer (CF), basal application of OF once, application of OF less 10% (–10%OF), and application of OF less 20% (–20%OF). Soil samples were collected after harvesting rice in the third season. We employed Illumina high-throughput sequencing technology to determine bacterial and fungal community composition, diversity, and structural differences.

Results All the three OF treatments had similar rice yield to CF. The three OF treatments (P<0.05) increased soil pH. Compared with CF, OF treatment increased soil organic matter content, –20%OF treatment increased soil alk.-hydr. N and readily available K contents (15.40% and 39.75%), OF and –10%OF treatments increased soil available P (49.82% and 46.02%) and readily available K contents (91.40% and 30.44%). OF treatments had no significant effect on soil enzyme activity compared with CF treatment. OF treatment (P<0.05) changed the structure of the microbial community to different extents, –20%OF treatments increased chao1 index and species richess index significantly. The abundance of Proteobacteria and Acidobacteria in –20%OF treatment was 6.64% and 8.37% higher than those in CF, while Firmicutes was 72.67% lower in –20%OF than in that CK. The abundance of Zygomycota in –20%OF treatment was 77.40% higher than that in CF, and the abundance of Glomeromycota in –10%OF treatment was 117.38% lower than that in CK. Correlation analysis indicated that soil bacterial diversity was positively related to soil available P. Redundancy analysis indicated that APtase activity, available K, available P, and alk.-hydr. N were the bacterial community’s main drivers, while alkali-hydrolyzable N, total K, available P and urease limited the soil fungal community.

Conclusions Organic-inorganic compound fertilizer is more effective on rice yield than chemical compound fertilizer. Reducing 20% of nutrient input based on OF could regulate soil available nutrient content for diverse and abundant bacterial and fungal communities.