It has been well documented that organic amendment affects soil nematode community structure. However, little is known about the effect of organic amendment amount on soil nematodes. To assess the effect of the amount of organic amendments on soil nematode community structure and metabolic activity, the community composition, abundance, and metabolic footprints of soil nematodes were determined in a long-term field experiment with various amounts of organic amendment in Northeast China. Fertilization treatments included an unfertilized control (CK), chemical fertilizer without manure amendment (OM0), manure applied at 7.5 Mg ha-1 plus chemical fertilizer (OM1), and manure applied at 22.5 Mg ha-1 plus chemical fertilizer (OM2). A total of 46 nematode genera were found. Treatments with the largest amount of organic amendment had the smallest number of plant parasite genera (5), but a largest number of dominant genera (7). Soil nematodes, bacterivores, and fungivores were the most abundant in OM2, followed by OM1, and the lowest in OM0 and CK. Organic amendment increased the enrichment index (EI), and the large amount of organic amendment increased the metabolic footprints of bacterivore (Baf) and fungivore (Fuf) and enrichment footprint (Ef). The relationships between Baf (or Fuf) and the increases in soil organic carbon (ΔSOC) and total nitrogen (ΔTN) were stronger than those of bacterivore (or fungivore) abundance with ΔSOC and ΔTN, except for the relationship between bacterivore abundance and ΔSOC. The EI and Ef were positively correlated with ΔSOC and ΔTN. These findings suggest that the amount of organic amendment affects soil nematode activity and function at entry levels in soil food web, and that metabolic footprints of soil nematodes may be better indicators than their abundances in assessing their relationships with soil nutrients. 相似文献
Crops grow poorly in saline-sodic soils, and the productivity of these soils can be dramatically improved with proper amendments. Current research mainly focuses on either organic or inorganic soil amendments, whereas few studies address options of combining organic and inorganic amendments. The objective of this study was to develop new organic and inorganic soil amendments which can lower the soil pH, replace sodium, and improve soil structure.
Materials and methods
Polyhalite (PL), microporous potassium-silicon-calcium mineral fertilizer (MF), furfural residue (FR), and fulvic acid (FA) were mixed with four different ratios to produce organic and inorganic soil amendments: PLFR, PLFA, MFFR, and MFFA. And their optimum mixing ratios were determined by comparing the potassium, calcium concentrations, and pH of filtrate after dissolution. Then, a leaching experiment was conducted by packing mixtures (mass ratio of soil to amendment = 219:1, equivalent to 13 t/hm2) of the saline-sodic soil with each one of these amendments plus two contrasts, gypsum (GP), and no amendment (CK). And the remediation effect was compared by pH, EC, ESP, texture, organic recombination degree of clay, saturated hydraulic conductivity, water-stable aggregates fraction, and enzyme (urease, alkaline phosphatase, and catalase) activities of soil.
Results and discussion
After four times leaching experiment, soil treated with PLFR had lower pH and 25.86% lower exchangeable sodium than untreated soils. The water-stable small macroaggregate fractions and saturated hydraulic conductivity of the MFFR-treated soils were significantly increased by 133% and 31%, respectively. Also, the total soil and heavy fraction organic carbons of the soils treated with MFFR in addition to its alkaline phosphatase activity were all significantly higher than the other treatments.
Conclusions
The results revealed that MFFR has more potential as a soil amendment to improve soil structure and quality and thus help in the development and use of saline-sodic lands for agriculture.
