Excessive application of nitrogen fertilizer and weeding on the soil surface of pomelo orchards lead to soil nutrient loss, soil acidification, and thus reduce the yield and quality of pomelo.
More...Excessive application of nitrogen fertilizer and weeding on the soil surface of pomelo orchards lead to soil nutrient loss, soil acidification, and thus reduce the yield and quality of pomelo. A two-year field plot experiment was carried out to study the effects of grass mulching and nitrogen fertilizer reduction on the productivity and quality of pomelo as well as soil chemical properties and microbial community by considering the following treatments; Farmer nitrogen fertilizer (F) application as a control, Farmer nitrogen fertilizer + Natural mulch (FN), Optimized (reduced) nitrogen application + Natural mulch (ON). The results showed that compared with F, the FN and ON increased the quality of pomelo by increasing Vc content (FN: 5.46% and ON: 12.37%), flesh aspect ratio (FN: 5.45% and ON: 7.14%) and TSS/TA (FN: 23.24% and ON: 32.99%) while decreasing titratable acidity (FN: 23.68% and ON: 31.57%) of pomelo. In addition, the FN and ON treatments increased soil water content (FN: 29.09% and ON: 27.58%), organic matter content (FN: 32.59% and 32.98%), pH (FN: 4.74% and ON: 12.80%), nutrient content (AN, AP, AK) (FN: 21.62% and ON: 19.21%), CEC (FN: 2.79% and ON: 8.61%) and decreased exchangeable acidity (FN: 29.05% and ON: 74.76%) and soil bulk density (FN: 9.82% and ON: 10.71%). Metagenomic sequencing results showed that FN and ON significantly changed the diversity and community composition of microorganisms and functional genes compared with F treatment. FN treatment increased bacterial and fungal diversity, while ON treatment reduced fungal diversity. In addition, FN treatment increased the relative abundance of Rhodanobacter, Mycobacterium, Streptomyces and ON treatment increased the relative abundance of Rhodoplanes, Bradyrhizobium, and Catenulispora. FN treatment significantly increased functional genes involved in carbon metabolism. At the same time, FN and ON treatment significantly affected the abundance of the CAZY gene at the class level, and ON treatment significantly increased the abundance of GH74, CE10, GH109, and CE4 enzymes. According to RDA analysis, SBD was positively correlated with bacterial community and functional genes, and negatively correlated with the fungal community. SMC, pH, SOM, AN, and CEC were negatively correlated with the bacterial community and functional genes and positively correlated with the fungal community. According to the correlation analysis, soil properties, microbial community, and function all affected the productivity and quality of pomelo. In conclusion, mulching grass and reduction of N fertilizer improved soil quality and reshaped soil bacterial, fungal, and functional gene ecology, thus improving pomelo productivity and quality. This study showed that grass mulching and nitrogen reduction was a promising method for pomelo production management.
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