| Farmland soil acidification is one of the main reasons that lead to the reduction of crop yield and affect the sustainable development of agriculture.Weeds are an important part of farmland ecosystem.They play an important role in maintaining farmland ecological balance and sustainable utilization of farmland.In order to explore the effect of soil acidification on the relationship between wheat and weed species,this study selected Triticum aestivum L.and Setaria viridis(L.)Beauv.De Wit replaced the experiment to set up 4 different soil acidities(p H 7.3,p H 6.2,p H 5.9,p H 5.3)and 3 configuration ratios(wheat sole species,Setaria sole species,wheat and Setaria 1:1 mixed species)to analyze the soil The effect of p H reduction on the growth and development of Setaria and wheat seedlings,soil nutrients and microbial structure in the rhizosphere provides a theoretical basis for the sustainable management and resource utilization of farmland weeds by soil acidification.The main results are as follows:1.Effects of soil acidification on the growth of Setaria and wheat seedlingsIn order to explore the effects of soil acidification on the growth and interspecific relationship between Setaria and wheat,leaf enzyme activities(malondialdehyde MDA,peroxidase POD,catalase CAT),chlorophyll content,and morphological indicators(plant height,leaf area,biomass,root length,root-shoot ratio,etc.),and relative competition intensity(RCI)were used as parameters for the effect of soil p H on the growth of Setaria and wheat.The results showed that:(1)In sole planting,the decrease of soil p H significantly increased the MDA content and POD activity of Setaria and wheat,and significantly increased the CAT activity of Setaria.Compared with the sole species,the MDA content of Setaria in the mixed species decreased significantly by 49.44% at soil p H5.9,and the POD activity increased significantly except at soil p H 6.2;the MDA content of wheat decreased significantly during mixed planting,and the activity of CAT increased by8.32%～84.89% at soil p H 5.9～6.2.(2)With the decrease of soil p H,the chlorophyll content of Setaria decreased first and then increased in a sole species,and the difference was significant when the soil p H≤5.9;the content of chlorophyll a in wheat decreased,and the content of chlorophyll b increased first and then decreased,and the difference was significant.Compared with the sole species,the chlorophyll b content of Setaria in the mixed species was significantly increased by 47.38%～213.07% and that of wheat was significantly decreased by 9.72%～30.28%.(3)With the decrease of soil p H,except for the root shoot ratio and leaf area,other morphological indexes of Setaria increased first and then decreased in a sole species,and the difference was significant;the plant height,root length and biomass of wheat increased first and then decreased,and other morphological indexes decreased first and then increased.Compared with sole species,the plant height of Setaria in the mixed species decreased significantly by 35.07%～46.92% when the soil p H≤6.2,the root shoot ratio increased significantly by 202.33%～1025.51% when the soil p H≥6.2,and other morphological indexes decreased significantly;wheat plant height decreased significantly by 7.90% at soil p H 6.2,biomass decreased significantly by13.03% at soil p H 6.2,and root shoot ratio increased by 7.90% at soil p H 6.2.(4)The RCI value of each soil acidity was 0～1.The RCI value of wheat was greater than 0 in soil p H5.3 and p H 6.2,and less than 0 in soil p H 5.9 and soil p H 7.3.2.Effects of soil acidification on soil nutrientsIn order to explore the impact of soil acidification on soil nutrients,soil samples were collected after plant harvest,mixed,air dried and screened for physical and chemical properties analysis.The results showed that:(1)Before planting,the content of organic matter increased significantly by 0.18%～9.96% with the decrease of soil p H,and the content of available nutrients decreased first and then increased.(2)The content of organic matter of mixed species is lower than that of sole species at soil p H 5.9～6.2,and the content of ammonium nitrogen of mixed species is higher than that of sole species at soil p H>5.9.Except for soil p H 5.9,the content of available phosphorus of mixed species is significantly higher than that of sole species,and the content of available potassium of mixed species is lower than that of sole species at soil p H≥5.9.Compared with that before planting,the organic matter content of mixed species at soil p H 5.9 and wheat sole species at soil p H 5.3 decreased significantly,and the organic matter content of other treatments increased;the content of ammonium nitrogen in mixed species,sole wheat and sole Setaria decreased by 16.16%～60.56%,24.24%～67.75% and 35.98%～71.50% respectively;the content of rapidly available phosphorus increased by 3.58% when the soil p H 5.3,and the content of available phosphorus in other treatments decreased;the content of available potassium in mixed species,sole wheat and sole Setaria decreased by 8.03%～14.37%,7.97%～10.53% and 0.58%～12.15% respectively.(3)Total phosphorus and available phosphorus were positively correlated with soil p H,and the correlation coefficients were0.144 and 0.767.Other soil nutrients were negatively correlated with soil p H.Organic matter,available phosphorus and total potassium have the greatest correlation with soil p H.3.Effects of soil acidification on rhizosphere soil microorganismsThe plant rhizosphere soil was sampled and sequenced to analyze the soil microbial community structure.The results showed that:(1)The species number,richness,evenness and diversity of bacteria increased first and then decreased with the decrease of soil p H,and the difference was significant.Compared with mixed species,the abundance of soil bacteria was increased in the sole species of Setaria and wheat;The number of species increased significantly by 8.97% and 3.38% at soil p H 5.3;Shannon index decreased by0.36% and 0.26% at soil p H 6.2.The decrease of soil p H resulted in the decrease of the number and diversity of fungal species,the increase of the richness and uniformity of the sole species and the decrease of the richness and uniformity of mixed species.Compared with mixed species,the abundance of soil fungi decreased in the sole species of Setaria and wheat when the soil p H≥6.2;The number of species decreased by 1.93%～12.26% and7.45%～11.86% when soil p H≥5.9;Shannon index decreased by 4.98% and 12.04% at soil p H 7.3.(2)The number of common bacterial species in the mixed species was 6.90% and1.27% lower than that in the sole species of Setaria and wheat respectively,and the number of common fungal species in the mixed species was 1.92% and 6.83% higher than that in the sole species of Setaria and wheat respectively.The main dominant bacterial groups were Proteobacteria,Actinomycetes,Chloroflexi,Acidobacteria and Firmicutes,and the main dominant fungi were Ascomycota,unclassified-k-Fungi and Mortierella.(3)Soil p H,ammonium nitrogen,available phosphorus,available potassium,organic matter and total potassium had significant effects on soil bacterial community structure,and only available phosphorus had significant effects on fungal community structure. |
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