| Gravel-mulched land is a set of planting methods summarized by farmers in arid and semi-arid areas to cope with the formation of scarce precipitation.However,with the increase of gravel-mulched years,a series of ecological and production problems such as decreased fertility,increased pests and diseases,and reduced yield have emerged,which seriously restricts the sustainable development of gravel-mulched land.Therefore,the transformation of gravel-mulched field planting mode is imminent.In this study,the planting base of Sunshine Ranch in Zhongwei City,Ningxia Hui Autonomous Region was selected.After 22 years of continuous sand pressing,Lonicera japonica,Lycium chinense and Citrullus lanatus were planted respectively.Three 20 m × 20 m quadrats were set in each plot,and each quadrat was sampled according to the five-point method of plum blossom.The soil physical properties(soil water content,soil bulk density,capillary porosity,total porosity,non-capillary porosity,soil capillary water holding capacity,soil saturated water content),chemical properties(available nitrogen,pH,available potassium,available phosphorus,total phosphorus,total nitrogen,organic carbon,total potassium),microbial properties(non-specific bacteria,Gram-positive bacteria,Gram-negative bacteria,methanotrophs,fungi,saprophytic fungi,actinomycetes,eukaryotes),enzyme activity(β-1,4-glucosidase(BG),β-1.4-Nacetylglucosaminidase(NAG),leucine aminopeptidase(LAP),alkaline phosphatase(AKP))and soil metabolites(lipids,nucleotides,amino acids,xenobiotics,peptides,cofactors,vitamins)were measured,combining the above indicators to measure changes in soil quality on sand pressed land.The main results are as follows:(1)In terms of soil physical properties,the soil bulk density of Lonicera japonica plot was 1.52 g/cm3,the soil bulk density ofLycium chinense plot was 1.61 g/cm3,and the soil bulk density of Citrullus lanatus plot was 1.59 g/cm3.The soil water content of Lonicera japonica plot was 5.56%,the soil water content of Lycium chinense plot was 2.4%,and the soil water content of Citrullus lanatus plot was 5.64%.The total soil porosity of the Lonicera japonica plot was 42.34%,and the soil capillary porosity was 41.66%.The total soil porosity of the Lycium chinense plot was 40.33%,and the soil capillary porosity was 39.77%.The total soil porosity of the Citrullus lanatus plot was 38.08%,and the soil capillary porosity was 37.26%.In terms of soil chemical properties,the soil organic carbon content in the Lonicera japonica plot was the highest(0.55%)in the 0-10 cm soil layer,and the soil organic carbon content in the Citrullus lanatus plot was the lowest(0.33%).The content of alkali-hydrolyzable nitrogen in Citrullus lanatus plot was the highest(43.02 mg/kg),and that in Lonicera japonica plot was the lowest(17.52 mg/kg).The total nitrogen content of soil in Lonicera japonica plot was the highest(4.94%),and the total nitrogen content of soil in Citrullus lanatus plot was the lowest(4.49%).The content of soil available potassium in Citrullus lanatus plot was the highest,which was 77.99 mg/kg,and the content of soil available potassium in Lycium chinense plot was the lowest,which was 56.31 mg/kg.The soil available phosphorus content in Citrullus lanatus plot was the highest,which was 2.55 mg/kg,and the soil available phosphorus content in Lycium chinense plot was the lowest,which was 1.09 mg/kg.The soil organic carbon content in the 10-20 cm soil layer was the highest,which was 0.47%,and the soil organic carbon content in the Citrullus lanatus plot was the lowest,which was 0.27%.The content of alkalihydrolyzable nitrogen in Citrullus lanatus plot was the highest(22.31 mg/kg),and that in Lonicera japonica plot was the lowest(16.29 mg/kg).The total nitrogen content of soil in Lonicera japonica plot was the highest(4.55%),and the total nitrogen content of soil in Citrullus lanatus plot was the lowest(3.45%).The soil available potassium content in the Lonicera japonica plot was the highest(51.02 mg/kg),and the soil available potassium content in the Lycium chinense plot was the lowest(38.08 mg/kg).The soil available phosphorus content in the Citrullus lanatus plot was the highest,1.83 mg/kg,and the soil available phosphorus content in the Lycium chinense plot was the lowest,0.93 mg/kg.(2)A total of 38 PLFAs were detected in Lonicera japonica plots,of which 23.7%were nonspecific bacteria and 31.8%were Gram-negative bacteria.A total of 32 PLFAs were detected in the Lycium chinense plot,of which 41.9%were non-specific bacteria and 27.2%were Gram-negative bacteria.A total of 14 PLFAs were detected in Citrullus lanatus plots,of which 35.7%were non-specific bacteria and 48.7%were gram-negative bacteria.The ratio relationship between fungi and bacteria was Lonicera japonica>Citrullus lanatus>Lycium chinense,and the ratio relationship between Grampositive bacteria and Gram-negative bacteria was Lonicera japonica>Citrullus lanatus>Lycium chinense.The BG enzyme activity in the Lonicera japonica plot was the highest(1.61 nmol g-1 h-1),the BG enzyme activity in the Citrullus lanatus plot was the lowest(0.90 nmol g-1 h-1),the NAG enzyme activity in the Lonicera japonica plot was the highest(18.31 nmol g-1 h-1),the NAG enzyme activity in the Lyclum plot was the lowest(6.14 nmol g-1 h-1),the LAP enzyme activity in the Citrullus lanatus plot was the highest(0.92 nmol g1-h-1),and the LAP enzyme activity in the Lycium chinense plot was the lowest(0.60 nmol g-1 h-1).The AKP enzyme activity in the Lonicera japonica plot was the highest,24.68 nmolg-lh-1,and the AKP enzyme activity in the Lycium chinense plot was the lowest,9.19 nmol g-1 h-1.(3)There were 184 kinds of soil differential metabolites in the positive ion mode between Lonicera japonica plot and Lycium chinense plot.Among them,97 metabolites showed an upward trend compared with Lycium chinense plot,and 87 metabolites showed a downward trend compared with Lycium chinense plot.There were 129 kinds of soil differential metabolites between the two in the negative ion mode,of which 72 metabolites showed an upward trend compared with the Lycium chinense plot,and 57 metabolites showed a downward trend compared with the Lycium chinense plot.Compared with the Citrullus lanatus plot,there were 204 different metabolites in the soil under the positive ion mode,of which 144 metabolites showed an upward trend compared with the Citrullus lanatus plot,and 60 metabolites showed a downward trend compared with the Citrullus lanatus plot.There were 146 kinds of soil differential metabolites in the negative ion mode,of which 73 metabolites showed an upward trend compared with the Citrullus lanatus plot,and 73 metabolites showed a downward trend compared with the Citrullus lanatus plot.Compared with the Citrullus lanatus plot,there were 191 differential metabolites in the positive ion mode,of which 116 metabolites showed an upward trend compared with the Citrullus lanatus plot,and 75 metabolites showed a downward trend compared with the Citrullus lanatus plot.There were 105 differential metabolites between the two in the negative ion mode,of which 51 metabolites showed an upward trend compared with the Citrullus lanatus plot,and 54 metabolites showed a downward trend compared with the Citrullus lanatus plot.There were 15 differential metabolites in Lonicera japonica and Lycium chinense plots.The most up-regulated metabolites were 2-furfural,tyrosol,β-alanine and glyceraldehyde.There were 9 differential metabolites in Lonicera japonica and Citrullus lanatus plots.The most up-regulated metabolites were Dcathinone and 2-aminobenzoic acid.There were 16 differential metabolites in Lycium chinense and Citrullus lanatus plots.The most up-regulated metabolites were maleamine,(R)-2-O-sulfonate and 2ketobutyric acid.A total of 28 metabolic pathways were significantly enriched in the Lonicera japonica plot compared with the Lycium chinense plot,of which 15 were significantly enriched.Compared with Citrullus lanatus plot,43 metabolic pathways were significantly enriched in Lonicera japonica plot,of which 34 metabolic pathways were significantly enriched.A total of 38 metabolic pathways were significantly enriched in the Lycium chinense plot compared with the Citrullus lanatus plot,of which 20 metabolic pathways were significantly enriched.(4)The soil fertility index of Lonicera japonica plot was the highest(0.246),followed by Lycium chinense plot(0.211),and Citrullus lanatus plot(-0.457).The soil quality index of Lonicera japonica plot was 0.347,the soil quality index of Lycium chinense plot was-0.268,and the soil quality index of Citrullus lanatus plot was-0.124.The relationship of soil quality index under three crop types was Lonicera japonica>Citrullus lanatus>Lycium chinense.From the soil quality index based on the minimum data set,the soil quality of the Lonicera japonica plot was good,and the soil quality of the Lycium chinense and Citrullus lanatus plots was low.In summary,compared with the planting of Lycium chinense and Citrullus lanatus,the planting of Lonicera japonica can improve soil fertility and improve soil quality.Therefore,we suggest that Lonicera japonica can be transformed after the decline of gravel-mulched land. |
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