Effects Of Fertilization And Weeds Diversity On Soil Microbial And Nematodes Community Composition

Due to a large number of application of fertilizer and herbicides, high-yield farmland ecosystem issubject to decreasing productivity, biodiversity and soil environmental degradation. Soil microbes andnematodes are involved in soil carbon, nitrogen, phosphorus and sulfur cycle, they play an important role insoil fertility, and often considered as sensitive marker in detecting changes in soil properties. Microbial andnematode community composition and can be used to assess the level of fertility and health. In this study,we set fertilization and weed diversity experiments, to study the effects of fertilization on soil microbial andnematodes community structure, and the effects of increasing weeds diversity on soil microbial communitystructure. We based on phospholipid fatty acid analysis to assess chemical fertilizers and weed diversity onmicrobial and nematode community composition in winter wheat, clarifying the relation betweenfertilization and weed and soil biology.Fertilization is a strong determinant of soil chemical properties, which in turn affect soil microbialcommunity composition and activities. This study examined the effects of chemical fertilizer application onsoil microbial biomass, community structure in winter wheat crops using phospholipid fatty acid (PLFA)analysis. A complete factorial combination experiment of nitrogen (N) and phosphorus (P) fertilization wasdesigned, with4treatments:(1) P-addition (SP),(2) N-addition (SN),(3) NP-addition (NP), and (4) nofertilization (CK). The results showed that fertilization have a greater impact on soil nutrient content,phosphorus fertilizer significantly increased soil available phosphorus, nitrogen fertilizer significantlyincreased amino nitrogen content. The interaction effects between nitrogen and phosphorus significantlydecreased soil pH. Fertilization significantly affect microbial community composition. SN did notsignificantly affect the total microbial biomass, but significantly increased the Gram-negative bacteriabiomass, and significantly decreased the fungal biomass; SN did not significantly affect the total abundanceof nematodes in2012, but significantly reduced the total abundance of nematodes; SN significantly reducesthe abundance of bacterivores, phytophages, but no significant effect on other trophic groups. SP did notsignificantly change the total microbial biomass, but significantly increased the Gram-positive bacteriabiomass in2012, Gram-negative bacteria did not change significantly; SP reduced significantly fatty acids 16:010Me and18:010Me, which were consider as actinomycetes. SP had no significant effect onnematodes. NP-addition significantly increased fungal biomass; various groups of microbial biomass werelargest in NP-addition, which also had some new markers of fatty acids, such as16:02OH,18:3ω6c and19:1ω11c. No significant effect of nitrogen and phosphorus on nematodes. This suggests that theinteraction of nitrogen and phosphorus improved soil fertility, increased microbial biomass and diversity.These results suggest that N and P co-limited microbial biomass. As time progressed, microbial communitystructure significantly changed in all treatments except in the SP-addition plots. We conclude that microbialbiomass and structure of soil microbial communities were influenced by soil nitrogen and phosphorusaddition and their interaction effects. In two years, the interaction of nitrogen and phosphorus significantlyincreased actinomycetes biomass, which had a significant positive correlation with aboveground biomass ofwinter wheat (r=0.520, p=0.000; r=0.548, p=0.000). Therefore, soil actinomycetes appear to be animportant driver to improve aboveground productivity, and play an important role in safeguarding soilecosystem function.This study was conducted to examine the effects of weeds diversity on microbial community structurein soil of winter wheat using phospholipid fatty acid (PLFA) analysis. The experiment with a split-plotdesign was established in October2010, where the fertilizer treatment (chemical fertilizer and organicmanure) was applied to main plots and weeds diversity (0,1,2,4) in sub-plots. The results show that:organic fertilizer can largely increase soil microbial biomass and soil nutrients. In chemical fertilizer andorganic fertilizer treatments, weeds diversity significantly changed soil carbon to nitrogen ratio and pH,carbon to nitrogen ratio was the highest in the4kind weeds diversity treatment, they were10.08and13.51,respectively. In chemical fertilizer treatment, weeds diversity significantly affected fungi to bacteria ratio,which was the largest in4kind weeds treatments, significantly higher than other treatments. Fungal andmycorrhiza fungi biomass were lowest in1kind weed treatment (1.0nmol/g dry soil and0.4nmol/g drysoil), and significantly lower than4kind weeds treatment (1.3nmol/g dry soil and0.6nmol/g dry soil). Inorganic manure treatment, weeds diversity significantly affected Gram-positive to Gram-negative bacteriaratio, which was minimum in0kind weed treatment, and was significantly lower than1,2,4kind weedstreatments. Mycorrhiza fungi biomass was lowest in1kind weed treatment (1.5nmol/g dry soil), andsignificantly lower than the4kind weeds treatments (1.8nmol/g dry soil). In two fertilization treatments, the carbon to nitrogen ratio was significantly correlation with various groups of microbial biomass, so thatweeds diversity affect microbial community composition by changing the soil carbon and nitrogen ratio,moreover, the shift of microbial community composition was different. In chemical fertilizer treatmentweed diversity significantly increased fungi to bacteria ratio, improved soil ecosystem stability; while inorganic fertilizer, increasing the diversity of weeds significantly increased the ratio of Gram-positivebacteria and Gram-negative bacteria, pH value. Analysis of variance in1kind of weed showed that in thepresence of legume, Asteraceae, Poaceae and cruciferous weed species treatment, species specificity are nosignificant effect on soil microbial biomass and taxa ratio. Thus, species diversity is not species-specificaffect microbial community composition. We suggest that farmland should apply manure to increase soilmicrobial biomass; while in chemical fertilizer farmland should maintain a certain weed diversity, forregulating microbial community structure and improving the soil ecosystem.Therefore, to grasp the dynamics of soil organisms in farmland ecosystem under fertilization and weeddiversity, explore the ecological functions of soil organisms in maintaining farmland ecosystem, revealingplant-soil-soil biota interactions and feedback mechanisms, which has important theoretical and practicalsignificance for farmland ecosystem health development.