Study On The Relationship Between Phosphorus Nutrition And Continuous Cropping Obstacle In Cassava

This study choosed XinXuan 048 as material, and three phosphorus levels were set that were low phosphorus P1 (P2O5 75kg/hm2),medium phosphorus P2 (P2O5 150kg/hm2),high phosphorus P3 (P2O5 225kg/hm2) respectively,and CK(P2O5 0kg/hm2) as control,to investigate the relationship between continuous cropping obstacle and phosphorus nutrient. The main results were as follows:(1)The appropriate amount of phosphate fertilizer promoted grown and thickening of cassava under continuous cropping, of which P1 treatment was the best. High phosphorus fertilizer wasn’t conducive to the grown of cassava under continuous cropping.Excessive phosphorus might increased the occurrence of continuous cropping obstacle, inhibited the growth and thickening of cassava.(2)Under continuous cropping, the appropriate amount of phosphate was conducive to the synthesis of chlorophyll in leaf.Though high phosphorus promoted the synthesis of chlorophyll at seedling stage, in the late period did just the opposite, and increased the effect of continuous cropping.Phosphorus excess could increased the occurrence of continuous cropping obstacle.(3)Phosphorus can accelelated the rate of sucrose transportation from leaf to stem,promoted the transport of sucrose from stem to root tuber,and participated the synthesis of starch and other nutrients in root of cassava under continuous cropping. Overall,the soluber sugar content of all tissue of P1 treatment was higher; and with the increase of phosphate fertilizer, soluble sugar content decreased.It showed that phosphorus excess increased the occurrence of continuous cropping obstacle.(4)Stem’s phosphorus content of P2 treatment was the highest at tuber bluging stage,but phosphorus wasn’t good for the phosphorus accumulation in root and increased the effect of continuous cropping.(5)For continuous cropping,soil’s total phosphorus and available phosphorus content of P2 and P3 treatment were higher relatively.The soil’s available potassium content of the P1 treatment was higher in the whole growth period relatively,and the formation of soil’s alkali hydrolyzable nitrogen was inhibited by the phosphate fertilizer at the seedling stage and increased the effect of continuous cropping,but after the seedling stage is different, of which soil’s alkali solution nitrogen content of P1 treatment was higher relatively.(6)For continuous cropping, low amount of phosphorus fertilizer could promote the accumulation of tuber’s late starch, root length and weight gain of root, so as to promote the increase of starch accumulation and yield of root.Phosphate excess could inhibit root starch accumulation at the late age, decreased the yield of tuber, and increased the occurrence of continuous cropping obstacle.Due to the effect of continuous cropping, low amount of phosphorate fertilizer can coordinated nutrient of soil to meet the demand of the normal growth and development of cassava,promoted chlorophyll synthesis, and regulated the content of carbohydrate and total phosphorus content in every tissue reasonablely to coordinate the various physiological and metabolic activities, so as to promote the increase of starch accumulation and yield of root.Phosphorus excess was not conducive to normal growth of cassava and development,and increased the occurrence of continuous cropping obstacle.