| Peanut is a type of significant oil crops in China. In recent years, with the development of system update and innovation of agricultural technology, the peanut planting structure has greatly changed. The expanding of scale and increasing of peanut planting density have led to a more severe continuous expansion. As peanut is very sensitive to the continuous cropping, it has become one of the leading problems of low and unstable yield. There is a series of obvious phenomena, such as thin and short plant, dysontogenesis, decline of quality and reduced yield. Therefore, the obstacles of continuous cropping in peanut cultivation have become an urgent problem to be solved. In the past, domestic and foreign researches on continuous cropping peanut focused on the factors that directly affected the yield, such as the effects of continuous cropping years on the growth and development of photosynthesis. With the development of fertilization technology, researches on the use of anti-croping to overcome the obstacle of continuous cropping have increased in recent years. Most researches focus on the single application of microbial agent, humic acid fertilizer and amino acid fertilizer. However, only a few emphasize on the effects of combined application of organic, inorganic and microbial fertilizers to overcome the continuous cropping obstacles.This paper selected more than five years of continuous cropping soil to test the soil. Pot experiment was utilized to simulate the field of continuous cropping. Through the comparative analysis on the effects of different formula fertilizers on protective enzyme activity, root vigor, root exudates as well as yield of continuous cropping peanut at different growth stages, this paper studied the role of different formula fertilizers in overcoming continuous cropping obstacles. The results show that:(1)The leaves and roots SOD activities and CAT activity of continuous cropping peanut were increased then decreased at the whole stage. The leaves and roots POD activities were increased first, then decreased and increased after the podding stage. The leaves MDA accumulation showed the same tendency at the whole growth stage:it decreased first and then increased. However, the roots MDA accumulated at a relatively low level at the seeding stage, then gradually increased and decreased.The effect of different formula fertilizers on protecting the enzyme system of plant showed that:The leaves and roots POD activities and CAT activity were higher than the activity of CK. The leaves and roots POD activities were lower than those of CK and there were significant differences except during the seeding stage. The effect on leaves POD activity began at the flowering and needling stage and the effect on roots POD activity ended at the podding stage. The effect of ATC treatment on the MDA accumulation in leaves happened at the seeding and flowering stage and the effect on MDA in roots was most significant at the seeding stage. The effect of ATC3 treatment on the protective enzyme system was most significant. Compared with the activity of CK, SOD activity and CAT activity in leaves and roots were 3.98-5.09 times and 1.57-1.58 times higher respectively. POD activity and MDA accumulation in leaves and roots were 16%-144% and 36%-45% lower than that of CK severally.(2)The effect of different formula fertilizers on root vigor showed that the root vigor of ATC treatment was higher than CK except in the podding stage. The treatment of ATC 1 and ATC3 had a significant effect compared with the other two treatments. However, there was no significant difference between them. The effect of ATC3 was the best and was 3%-109% higher than that of CK.(3)15 kinds of root exudates of continuous cropping peanut were identified in this study are as follows:4,6 dimethyl dodecyl,2,4 di tert butyl phenol,1 dodecanol, hexadecane,7 methyl heptadecane,1,2 benzenedicarboxylic acid,1,4 benzenedicarboxylic acid, tetradecanoic acid,2,6,10,15 tetranethyl heptadecane, hexadecane acid, eicosane, octadecanoic acid,hexyl pentadecane, hexadecanoic acid,2,3 bis(oxy)propyl ester, octadecanoic acid,2,3 bis(oxy)propyl ester.7 of them were reported rarely, including 2,4 di tert butylphenol,1 dodecanol,1,4 benzenedicarboxylic acid,7 methyl heptadecane, ercosane,hexadecanoic acid,2,3 bis(oxy)propyl ester,octadecanoic acid, and 2,3 bis(oxy)propyl ester.(4)The effects of different formula fertilizers on different kinds of root exudates of continuous cropping peanut were different. The formula of ATC3 decreased the total amount of root exudates at seeding stage. However, the effect of ATC treatment on 1,2 benzenedicarboxylic acid occurred during the whole growth stage. The effect of ATC3 on root exudates of continuous cropping peanut was mainly showed as the inhibiting during the whole growth stage. The inhibitory effect was the best at seeding stage.The RI of 1,4 benzenedicarboxylic acid reached-0.81.(5) Different formula fertilizers could improve the yield of peanut continuous cropping. The treatment of ATC3 in increasing the full fruit number of single plant was the best with an increase of 63% compared with CK. The treatment of ATC2 in increasing the weight of single plant was the best and was 38% higher than that of CK.(6)The correlation among root exudates, root vigor and yield of continuous cropping peanut was different. As simple correlation analysis showed, effects of root exudates of the content of Tetradecanoic acid, Hexadecane acid and Octadecanoic acid on root vigor and yield were no significant regularity in the rhizosphere soil of continuous cropping peanut. The effect of the content of Phthalic acid and Terephthalic acid on root vigor and yield of continuous cropping peanut was inhibited.Construction of root vigor of continuous cropping peanut regression model based on the content of root exudates of Tetradecanoic acid, Hexadecane acid, Octadecanoic acid, Phthalic acid, Terephthalic acid and the total of them at different growth stage in the rhizosphere soil of continuous cropping peanut. The model order: RVS(μg·g-1·h-1)=1408.86-1427.881X1(PTA)+289.206X2(M)-15.802X3(P)+5.717X4(St);RV FN(μg·g-1·h-1)=2073.696-38172.82X1(PTA)+31348.31X2(TPS);RVPD(μg·g-1·h-1)=4618.056-52893.547X1(PTA)-46.403X2(St)+486.710X3(M);RVM(μg·g-1·h-1)=816.902+13379.035X1 (TPA)-109.177X2(M)+1.899X3(TRE).Construction of continuous cropping peanut yield regression model based on the content of root exudates of Tetradecanoic acid, Hexadecane acid, Octadecanoic acid, Phthalic acid, Terephthalic acid and the total of them at different growth stage in the rhizosphere soil of continuous cropping peanut. That found the correlation among yield of continuous cropping peanut, the total of five kinds of root exudates at seeding stage, the content of Terephthalic acid at havesting stage and the content of Tetradecanoic acid at havesting stage was positive. The correlation among yield of continuous cropping peanut,the content of Phthalic acid at havesting stage and the content of Terephthalic acid at flowering and needle stage was negative. The regression equation can be expressed as:Yield (kg/hm2)=-3465.392+640.931X1(TPAH)-4112.731X2(TPAFN)+2.479X3(TRES)+34.333X4( MH)-768.718X5(PTAS).Through the above conclusions, compared with the ordinary fertilizer, combined application of organic, inorganic and microbial fertilizer was the best formula to improve the phenomenon of continuous cropping obstacles. The advantages were regulating leaf and root protecting enzyme system of continuous cropping peanut, increasing root vigor, reducing the content of root exudates and improving the yield. By constructing the regression model among the content and the total of root exudates of Tetradecanoic acid, Hexadecane acid, Octadecanoic acid, Phthalic acid, Terephthalic acid at different growth stage in the rhizosphere soil and yield of continuous cropping peanut, it can be seen that the main inhibiting factors of the yield of continuous cropping peanut were affected by the content of benzoic acid at the seedling stage and the content of Terephthalic acid at flowering and needle stage. |
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