| The wheat/maize/soybean relay-intercropping system is commonly used by smallholder farmers in Sichuan,so study on the growth dynamics,the application of under N and P fertilizers of wheat and maize on soybean growth,nutrient absorption,the soil nutrient nutrient uptake,soil nutrient dynamics,it is of great significance to analyze the yield increasing mechanism and realize the high yield and high efficiency.The field experiment was carried out in 2013-2014 containing,wheat set up 4 nitrogen levels:0,60,120,180 kg/hm2,denoted as N0,N60,N120,N180,set up the 3 phosphorus levels:0,90,180 kg/hm2,were recorded as P0,P90,P180,maize set up 4 nitrogen levels:0,90,180,270 kg/hm2 and 3 phosphorus levels:0,90,180 kg/hm2 and sub region;the sole wheat-soybean(W-S),wheat/maize/soybean relay-intercropping(W/M/S)and wheat/-/soybean(W/-/S)in the three modes as the research object,discusses the growth dynamics,phenotypic-plasticity responses,yield and nutrient absorption and accumulation of soybean and soil nutrient content in sole and relay-intercropping system.The main results are as follows:(1)The nitrogen and phosphorus fertilizer of wheat could promote the growth of wheat-soybean and wheat/maize/soybean intercropping system.At different stage the biomass increased first and then decreased with the increase of nitrogen fertilizer,while the N120 treatment was the highest.At branching stage the branching number of soybean increased with the increase of nitrogen application,and the number of branches at No level was only 17%of N180.Yield of sole and intercropping in N120 was highest,were increased by 19.7%and 51.7%than N0 treatment.The nitrogen fertilizer was helpful to increase the soybean vegetative organs of nitrogen and potassium content,and the content of soil nitrate absorption;The biomass of different stage were increase with P fertilizer of wheat increased,P180 reached the maximum.The phosphate fertilizer of wheat was helpful to increase the content of phosphorus and potassim,the absorption and the content of available phosphorus.(2)The aboveground biomass of soybean showed "S" type growth curve with the growth stage.The biomass accumulation in seedling stage was slow,and the biomass in the branching stage increased rapidly,while the biomass of leaf and petiole decreased during the grain filling stage;soybean nutrient uptake also showed "S" with the growth period.The content of nitrogen absorbed rapidly in the seedling stage to the grain filling stage,and reached the maximum value at the end of the filling stage.The content of P absorbed gradually seedling stage to pod stage,after pod stage rapidly and then decreased.The content of potassium absorbed rapidly in the seedling stage to the blooming stage,and accumulation of slowly at podding stage then decreased rapidly;The nitrate content in soil was slightly lower than that before planting,and the content of P in soil showed a decreasing trend with the growth stage,and decreased by about 2 mg/kg.(3)The wheat/maize/soybean relay-intercropping system was better than the wheat soybean system to improve the plasticity of soybean.During the branching stage(grow with maize),the main stem length than 6.2 cm,the first internode was longer than 2.7 cm,the stem diameter was less than 1.1 mm,and the branch was less than 1.2.During the blooming stage(after the corn harvest),the difference between two system was narrow.In harvest stage,the main stem of soybean was shorter than 10.4 cm,the first internode length was longer than 2 cm,the stem diameter was more than 1.2 mm and more than 2.6 branches.At branching stage the biomass and growth rate of sole was high 62.3%and 62.1%than intercropping,at blooming stage the biomass of intercropping 57.9%high than sole,and harvest than the biomass and growth rate of intercropping were high 57.9%and 70.8%than sole.The biomass of soybean was mainly distributed on the main stem,and the grain and pod of the main stem accounted for about 55%,while the grain and pod shell of the soybean branch were about 69%.The soybean grain yield is higher 72.1%than sole,60.6%higher than the grain number per plant,100 grain weight had no difference;The yield of soybean/maize/soybean system was 15.1%higher than wheat/-/soybean system.(4)The accumulation of nutrients in soybean was consistent with the law of aboveground biomass.Branching stage,N,P and K accumulation of soybean was significantly higher 104.4%,63.3%and 77%respectively than that intercropping.At the blooming stage,the content of N,P and K accumulation in relay-intercropping was significantly lower than sole,but there was no significant difference between medium and high nitrogen levels.During harvest stage,the N,P and K accumulation in relay-intercropping higher 56.4%,80.4.4%and 87.0%respectively than sole.In all,wheat/maize/soybean intercropping system can make full use of the wheat nitrogen fertilizer and phosphate fertilizer,nitrogen(120 kg/hm2),phosphorus(180 kg/hm2)is good for the branch,pod and pod,high yield to soybean;maize has obvious inhibitory effects on soybean growth,mainly in the shade and for soil nutrients,but it could recover rapidly or even fasten the gro,wtih after the harvest of the maize,promote branching,pod and seed,so that the yield of soybean of wheat/maize/soybean intercropping.The soybean late branching upward growth is the main mechanism of the growth recovery and yield advantage. |
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