Effects Of Rain Enhancement And Competition On Growth And Nitrogen Uptake Of Glycine Max And Amaranthus Retroflexus

In order to study the adapting mechanism of Glycine max response to water resource fluctuations,and the competition mechanism between crops and weeds in the process of invading agro-ecosystem.Based on the comparison of the normal rainfall patterns(central peak),the artificial simulation of high rainfall year in different precipitation fluctuations(early peak,central peak,double peak,later peak),compare the growth morphological characteristics,biomass and nutrient uptake of two species in three species(monoculture of Glycine max,monoculture of Amaranthus retroflexus,mixture of Glycine max and Amaranthus retroflexus)competition combination in 2015 and 2016.The results showed that rain enhancement had significant effects on special leaf area(SLA),height and relative growth rate(RGR)of A.retroflexus and G.max,they have the largest leaf area in the seedling stage,their leaves had higher SLA with higher rainfall.Compared with the monoculture,the leaf area of mixture of Glycine max decreased,and the leaf area of mixture of A.retroflexus increased.In the early growth seasonthe higher irrigation water is,the higher plant height is.A.retroflexus is higher than that of G.max,and the G.max is restricted in height,so that the mixture of G.max is obviously lower than that of monoculture of Glycine max.The RGR of G.max and Amaranthus retroflexus decreased with the growth season,and the RGR is the highest at seedling stage in June.Under the competition,the RGR of mixture of G.max is lower than that of monoculture of G.max in July and August,and the GRG of mixture of A.retroflexus was higher than that of monoculture of A.retroflexus.Rain enhancement and competition had significant effects on root mass/crown mass(R/C),biomass of A.retroflexus and G.max,From the seedling stage to the mature stage,the R/C of G.max and A.retroflexus decreased gradually.At the seedling stage,the treatment of higher rainfall have small R/C.The R/C of mixture of G.max was higher than that of monoculture of G.max and mixture of A.retroflexus was lower than that of monoculture of A.retroflexus.In the early growth season,rain enhancement can significantly increase the aboveground and underground biomass of G.max and A.retroflexus.Nutrient supply of leaves and stems,their had higher biomss with higher rainfall.In middle of growth,G.max can also increase the aboveground and underground biomass.In particular,it can significantly increase the accumulation of legume biomass.A.retroflexus growth period is short,the growth is mainly concentrated in the early growth season.Highter rainfall in the early growth season can comlete the vegetative body and accumulation higer of spica biomass in mature perio of A.retroflexus.The proportion of biomass of Amaranthus stem was higher.The biomass of whole G.max and the biomass of each organ are lower than that of monoculture,total biomass of A.retroflexus and all organs are higher than monoculture in competition.Rain enhancement and competition also significantly affect the content of nitrogen and distribution of nitrogen phosphorus,potassium accumulation in G.max and A.retroflexus.The content of nitrogen in the root,stem and leave of G.max and A.retroflexus decreased gradually with the growth period.In early growth season,G.max and A.retroflexus nitrogen,phosphorus and potassium had higher accumulation with higher rainfall.From July to September,G.max legume nitrogen content gradually increased and the content of A.retroflexus spica was decreased.As the competition to extend the growth period of mixture of G.max,so mixture of G.max nitrogen content is lower than the monoculture of G.max in Jun and July,mixture is higher than the monoculture in August and September.The nitrogen content of each organ of mixture of A.retroflexus was higher than that of monoculture of A.retroflexus.G.max nitrogen,phosphorus,potassium accumulation accounted for the highest organ is leave,root,stem.The accumulation of nitrogen and phosphorus in the leaves is the highest.With the growth period,the root,stem and leave decreased gradually,and the accumulation of phosphorus and potassium in the stem began to decline in September.The total nitrogen,phosphorus and potassium accumulation of G.max decreased,and the accumulation of total nitrogen,phosphorus and potassium increased.To sum up,rain enhancement can significantly increase the biomass and nutrient accumulation of G.max and A.retroflexus.G.max is more sensitive than A.retroflexus to precipitation fluctuations.A.retroflexus can quickly absorb the surrounding nutrients and use it efficiently to adapt to the changing environment.In competition with G.max,A.retroflexus can grow rapidly reproduce as early as possible at seedling stage.From the distribution of nutrients can be seen,the stem of A.retroflexus nutrient distribution after the spica,which is why A.retroflexus can quickly and efficiently respond to one of the reasons.