| Single superphosphate is one of the important phosphate fertilizers.Recently,the production and sales volume of single superphosphate decreased greatly due to the application of high content of phosphates,excess free acids and poor root growth.As to the problems of single superphosphate,we developed 2 types of synergistic superphosphates by ammonification,addition of functional substances,prilling etc.The solubility of synergistic superphosphates and their phosphate release and their effects on the growth of crops were investigated hydroponically and in field experiments.The results were as follows:(1)Firstly,liquid ammonia was added into single superphosphate products at the proportion of 1% of single superphosphates(w/w).The p H value was changed from 2.2.to 4.52.Then chicken manure and fulvic acid were added at a certain proportion.The mixtures were granulated,and two types of synergistic superphosphates were produced named as SP1 and SP2.(2)Synergistic superphosphates were incubated in water culture for 24 hours.It was found that p H in solution was decreased to 2.65,4.98 and 6.59 when treated with single superphosphate(SP),SP1 and SP2 respectively.The size of EC value in solution with different treatments showed SP2>SP1>SP.With the prolongation of incubation time,the concentration of available N increased gradually.The size of available N among different products was SP2>SP1>SP and that of P was SP>SP1>SP2.(3)Results from soil pillar washing indicated that at the same amount of nitrogen,the p H,EC,total nitrogen presented different change washing solution with the increases of washing times.at the same amount of phosphorus,the concentration of available phosphate in washing solution increased with the increases of washing times.The size of available phosphate among different products was SP=4.69mg/L,SP1=4.33mg/L,SP=4.26mg/L,even SP>SP1>SP2.(4)Effects of synergistic superphosphates on the growth of rape seedlings were investigated in field experiments.Results indicated that in comparison to no fertilizer treatment and SP treatment,synergistic superphosphates(SP1 and SP2)treatment increased the SPAD value of rape leaves,and enhanced the uptake of N and P in shoots of rape seedlings.The biomass of rape plants treated with SP1 and SP2 were 26.5% and 33.6% of that of the control treatment,was 8.0% and 26.5% of that of the SP treatment.The yield of rape seed treated with SP1 and SP2 was 17.3% and 26.0% of that of the control treatment,and1.8% and 9.4% of that of SP treatment.(5)In case of lettuce,the community yield of lettuce treated with SP1 and SP2 was 38.0% and 72.2% of that of the control treatment,Vitamin C content was 13.6% and 25.7% of that of the control treatment.In comparison to SP treatment,treatment with SP1 and SP2 increased lettuce community yield by 10.0% and 37.0%,Vitamin C content was increased by 5.6 %and 11.18%.The above results indicated that compared with single superphosphates,synergistic superphosphate increased the growth and biomass of rape and lettuce plants,and improved some quality indices.The mechanism underlined may be related to slow release of nutrients,less fixation of phosphates by soil,thus elevated their fertilizer effects. |
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