| Under the influence of various natural and human factors,such as excessive use of chemical fertilizers,soil quality and its sustainability have declined or even completely lost its physical,chemical and biological characteristics,leading to the formation of soil degradation.Soil degradation,as an important form of soil degradation,has become one of the serious global environmental problems,posing a serious threat to the sustainable development of agriculture,exerting an important impact on the farmland ecosystem,resulting in the decline of yield and quality.As an important component of farmland ecosystem,weeds are beneficial to the ecological balance of farmland system.At present,for soil acidification,people focus more on the influence of its nutrient mechanism on farmland productivity,and less on weed community.This article use the method combined with the indoor experiment,analysis of soil acidification farmland weed community diversity characteristics,understand the different fertilization modes between soil seed bank and vegetation,the relationship between research mainly farmland weed seeds in a simulated acidification environment conditions the growth of state,was to understand the general law of weeds in farmland ecological environment,for the prevention and control of farmland weeds and weeds with certain theoretical basis and management ideas.The main results are as follows:1? In order to explore the influence of soil acidification degree on the diversity of farmland weed community,five treatments(p H=4.6,5.6,6.3,6.8,7.2)were conducted through the acidification treatment localization test.There were 19 species of weeds belonging to 16 genera and 11 families in the farmland in the survey area.The dominance of gramineous weeds increased with the increase of soil acidification.The number of non-gramineous weeds such as Saluia plebeia r.Br and Polygonum orientale L.decreased with the decrease of soil acidity.The shannon-wiener diversity index,Simpson dominance index,Pielou evenness index and Margalef richness index of farmland weed community all decreased with the increase of acidification degree,and the differences between the two groups were significant(P<0.05);The shannon-wiener diversity index of control area(p H=7.2)was significantly different from that of other acidified weed communities(P<0.01).The composition of weed families,genera and species was significantly different between treatments at p H=6.8 and others treatments,with low similarity.The composition of weed species in areas with severe acidification(treatments at p H=5.5 and p H=4.6)was more similar,which is 0.67.2?Based on the 18 years positioning of wheat-corn two cropping farmland in hunan Qiyang red soil experimental station,the influence of long-term fertilization treatment on farmland weeds was analyzed,and the relevant analysis of farmland weed seed bank and overground weed community were carried out.The seed Banks(0-5 cm,5-10 cm,10-15cm)of surface vegetation and farmland topsoil were investigated by means of sample method and seed bank germination experiment.Weed species and density were analyzed to understand the effects of different fertilization treatments on weed species,diversity and maize yield in corn-wheat rotation fields.The results showed that :(1)A total of 2227 weeds were recorded in the soil seed bank in the test area,including 12 species in 12 genera and 8 families.The improved area(adding lime)accounted for 65% of the total number of species germination.A total of 1135 weeds,6 species from 6 genera and 4families,were found in the aboveground vegetation survey,and the improved area accounted for 52% of the total germination.The weed seed bank and overground weed community were dominated by annual herbs.(2)In different fertilization treatments,no matter in the overground weed community or in the soil seed bank,the weeds of the Chinese cropland with single application of fertilizer had the highest density in the community and occupied an absolutely dominant position.In the improved area,grass density decreased.(3)There was significant difference in the density of soil seed bank among different fertilization treatments,and the seed density of farmland with N fertilizer and NK fertilizer was significantly higher than that of other pure fertilization regions(P<0.05),and in N fertilizer treatment,the germination density of weeds reached the maximum,and the number increased rapidly.(4)The species diversity of soil seed bank was greater than that of surface communities,and Shannon diversity index in N fertilizer treatment was significantly lower than that in other fertilization areas(P<0.05).(5)In the treatment with separate application of chemical fertilizers,although the total number of species is the highest,the species of weeds is single,the diversity is low,and the yield of maize is low;With the application of constant fertilizer + improver,the p H of farmland soil decreased obviously,the diversity of NPKS+ straw returning field + Ca community was high,and the yield of maize was the highest..Different fertilization methods will affect soil p H value and change the diversity of weed seed bank,which is positively correlated with crop yield.Therefore,the reasonable and scientific fertilization method is beneficial to maintain soil p H and the diversity of weed seed bank,and has certain correlation with the improvement of crop yield.3?Soil acidification is the main factor restricting agricultural production,in view of the community survey,mainly in farmland weed dominant species Beckmannia syzigachne,Echinochloa crusgalli,Setaria viridis as the materials,set different p H of the soil environment,measured under different acidic environment Beckmannia syzigachne,Echinochloa crusgalli and Setaria viridis' s plant height,root length,morphology and the chlorophyll and other physiological indicators.The results showed that:(1)the degree of acidification had a significant effect on the germination of weed seeds.The change of soil acidity promoted the germination of grass weeds and inhibited the germination of other weed species.(2)Soil acidification had no significant effect on plant height,root number and root-crown ratio of weeds(P<0.05),but there were significant differences with root length and biomass(P<0.05).(3)the change of soil acidity changed the physiological characteristics of weeds,and the chlorophyll content increased with the decrease of acidity,with significant difference between treatments(P<0.05).The relative conductivity increased with the decrease of soil acidity,and there were significant differences between treatments(P<0.05).It can be seen that gramineous weeds are more adaptable to the acidified soil environment and have stronger tolerance. |
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