ABSTRACT
Organic fertilizer application can replace a part of chemical fertilizer (CF) to improve the quality and efficiency of litchi production. To further explore the soil microbiological mechanism, with 19-year-old 'Feizixiao' litchi trees as the research objects, we examined the effects of two consecutive years of reduced CF applications (average 21.5% of total nutrients) combined with sheep manure (OF) and bio-organic fertilizers (BIO) on soil microbial diversity, community composition and differential microorganisms. The results showed that reducing the application of chemical fertilizers and combining it with the application of sheep manure and bio-organic fertilizer for two consecutive years could significantly improve yield and quality. The average increase of yield in the two years was 23.1% and 39.0%, respectively. Soil organic matter content and pH increased significantly in response to the combination treatments. Compared to that in the chemical fertilizer treatment, the contents of soil available phosphorus, potassium, calcium, magnesium, iron, manganese, copper, and zinc displayed an increasing trend in the combination treatments. The application of organic fertilizer increased the diversity of bacteria and fungi in rhizosphere soil, but not in non-rhizosphere soil. Both treatments significantly changed soil microbial community structure, increased eutrophic bacterial groups such as Bacteroides, Proteobacteria, and Bacillus phylum, and reduced anatrophic bacterial groups such as Acidobacteria and Chloroflexus. Compared with CF, the relative abundances of MND1 under OF and TK10, Gemmatimonas, Pseudolabrys, Trichoderma and Botryotrichum under BIO were significantly increased, which was positively correlated with yield. In conclusion, reducing CF and applying organic ferti-lizer for two consecutive years could effectively improve soil pH and nutrient availability, increase rhizosphere microbial richness and diversity, change soil microbial community structure, and shape microbial communities being more conducive to yield and quality improvement.
Subject(s)
Litchi , Microbiota , Animals , Bacteria , Fertilizers/analysis , Manure , Sheep , Soil/chemistry , Soil MicrobiologyABSTRACT
Severe early defoliation has become an important factor restricting the development of the pear industry in southern China. However, the assembly patterns of microbial communities and their functional activities in response to the application of bioorganic fertilizer (BIO) or humic acid (HA) in southern China's pear orchards remain poorly understood, particularly the impact on the early defoliation of the trees. We conducted a 3-year field experiment (2017-2019) in an 18-year-old 'Cuiguan' pear orchard. Four fertilization schemes were tested: local custom fertilization as control (CK), CK plus HA (CK-HA), BIO, and BIO plus HA (BIO-HA). Results showed that BIO and BIO-HA application decreased the early defoliation rate by 50-60%, and increased pear yield by 40% compared with the CK and CK-HA treatments. The BIO and BIO-HA application significantly improved soil pH, available nutrient content, total enzyme activity and ecosystem multifunctionality, and also changed the structure of soil bacterial and fungal communities. The genus Acidothermus was positively correlated with the early defoliation rate, while the genus Rhodanobacter was negatively correlated. Additionally, random forest models revealed that the early defoliation rate could be best explained by soil pH, ammonium content, available phosphorus, and total enzyme activity. In conclusion, application of BIO or BIO mixed with HA could have assembled distinct microbial communities and increased total enzyme activity, leading to significant improvement of soil physicochemical traits. The increased availability of soil nutrient thus changed leaf nutrient concentrations and alleviated the early defoliation rate of pear trees in acid red soil in southern China.
