Response Of Soil Bacterial Community To Long-term Organic And Inorganic Fertilization In Dryland Areas Of Ningxia

In the arid area of central Ningxia,the soil organic carbon content is low and the level of agricultural productivity is low,and the long-term application of chemical fertilizers not only increases food production,but also brings challenges to the soil quality and sustainable development of agriculture.In order to elucidate the influence mechanism of long-term organic and inorganic fertilization on soil bacterial community composition and diversity in dry farming areas.Taking the farmland soil ecosystem as the research object,using a single-factor random block design,using long-term localization experiment（11 years）and high-throughput sequencing,the effects of no fertilization（T0）,single application of chemical fertilizer（T1）,chemical fertilizer combined with sheep manure organic fertilizer（T2）and chemical fertilizer combined with bio-organic fertilizer（T3）on soil were studied,the differences between soil bacterial community composition and diversity were analyzed,and the main soil environmental factors driving the change of soil bacterial community composition and diversity were explored.The main results are as follows:（1）Both organic and inorganic fertilizer methods increased the nutrient content in the soil and reduced the soil pH.The increase rate of soil total nitrogen,alkali-hydrolyzable nitrogen,total phosphorus,available phosphorus,available phosphorus,organic matter and available potassium content and soil pH were significantly lower under the treatment of sheep manure organic fertilizer（T2）,and the increase of maize yield and ear grain weight were significant.（2）The combined application of sheep manure organic fertilizer（T2）significantly increased soil enzyme activity and respiration intensity,and soil urease,alkaline phosphatase,catalase activity and respiration intensity increased by 2.06 times,0.52 times,10.56 times and 0.56 times compared with the control（T0）,respectively.（3）Under each fertilization treatment,the soil actinobacteria,Proteobacteria,and Chloroflexi bacteria were the dominant phylum;The combined application of organic fertilizer,bio-organic fertilizer and chemical fertilizer reduced the relative abundance of soil actinomycetes,increased the relative abundance of Phylum Lvwan,Bacteroides and Firmicutes,and there were significant differences between the combined application of chemical fertilizer and sheep manure organic fertilizer（T2）treatment and T0 treatment（P<0.05）.Nocardioides,KD4-96 and Subgroup₆ are the dominant genera of soil bacterial communities.Compared with the control（T0）,the combination of chemical fertilizer and sheep manure（T2）significantly increased the number of bacterial community species,community Simpson index,Shannon index and Chao 1 index（P<0.05）.RDA analysis showed that soil organic matter（P=0.001）and pH（P=0.003）were the main factors driving the change of soil bacterial community composition and diversity.Soil pH and organic matter content have direct effects on driving the composition of soil bacterial communities and soil bacterial diversity in dry farming areas.（4）Soil nitrogen-fixing bacteria under different fertilization treatments mainly belong to the phylum Proteobacteria.Among them,Skermanella and Azospirillum（relative abundance≥1%）were the dominant genera of soil nitrogen-fixing bacteria under long-term experiments.The combined application of long-term chemical fertilizer and sheep manure organic fertilizer（T2）significantly increased the relative abundance of soil Methylococcus and Methylocaldum compared with chemical fertilizer and bioorganic fertilizer（T3）.Compared with the control treatment（T0）,the combined application of chemical fertilizer with sheep manure organic fertilizer（T2）significantly increased the number of nitrogen-fixing bacteria species,the Simpson index,the Shannon index and the Chao1 index（P）of nitrogen-fixing bacterial communities<0.05)。RDA analysis showed that soil organic matter（P=0.001）and pH（P=0.01）were the main factors driving the change of soil nitrogen-fixing bacterial community composition and diversity.Soil pH and organic matter content had direct effects on the change of soil nitrogen-fixing bacterial community composition and diversity in dry farming area.The combined application of long-term chemical fertilizer and sheep manure organic fertilizer（T2）had the most significant effects on soil fertility and soil nitrogen-fixing bacterial community structure and diversity.（5）Long-term fertilization management combining chemical fertilizer with organic fertilizer such as sheep manure is an effective way to optimize soil nutrient management and improve soil fertility in the dry farming area of Ningxia.