| Problems caused by excessive application but low use efficiency of phosphate fertilizers are beingincreasingly prominent in the greenhouse vegetable production, and it is in urgent need to carry outrelevant basic research. A greenhouse experiment,which is carried out at Beijing Shunyi District inmoisture soil under production conditions, is conducted with complete experimental design toinvestigate the effects of artificially adding citric acid to the soil on available phosphorus temporal andspatial dynamic, phosphate fertilizer utilization ratio and fix ratio, and finally prove that phosphorusavailability is enhanced by citric acid through changes of tomato yield and economic benefits, as well astomato morphology/physiological and quality.The results are as follows.(1) An experiment was conducted with complete experimental design to investigate the effects offour levels of phosphate fertilizer and citric acid on available phosphorus temporal and spatial dynamicin0-1m soil layers. The test results showed that temporal and spatial dynamics were impactedappreciably by both the application of phosphate fertilizer and citric acid. Available phosphorusreduction tendency slowed down and maintained at a high level as the cultivation period by citric acidimposing. Citric acid could obviously increase available phosphorus contents of soil0~20cm depth ofthe soil, however, the amounts of available phosphorus improved by citric acid in the soil of20~40cmdepth were not as significantly as0~20cm’s, and citric acid had slightly effects to the soils blow40cm.(2) The soil pH was significantly reduced with0.08to0.63units in the application of citricacid,and dropped to7.55from8.17in the application of citric acid3.9mmol/L without phosphatefertilizer, which was close to the range of effectiveness pH value(pH6.0~7.5) in the calcareous soils.Agronomic phosphorus utilization efficiency(APUE), partial factor productivity of phosphorus(PFPP),apparent phosphorus recovery efficiency decreased as phosphate fertilizer application, whilephysiological phosphorus utilization efficiency increased, but citric acid improved them all at the samephosphate fertilizer level until a certain phosphate fertilizer and citric acid application. Phosphorus fixedrate decreased with the citric acid application at highest decrease of81.71%in96kg/hm2phosphorusapplication.(3) The morphology/physiological and quality of tomato were changed in a application of citricacid and the results were as followed. Citric acid promoted the shoot growth of plants, whole plant freshweight and shoot dry weight. Through inhibiting the growth of plant roots, citric acid limited theallocation of photosynthetic products transferring to the roots, and promoted root activity. Energyconversion rate, gas exchange capacity of leaves of the tomato were enhanced by citric acid and alsotomato quality, TSS content and acid-sugar ratio. Excess of citric acid got the opposite effects.(4) Tomato yield and economic benefits were increased as the phosphate fertilizer and citric acidadding until achieve the maximum yield6.04t/hm2at the treatment of phosphate fertilizer240kg/hm2and citric acid1.3mmol/L, and decreased if continuing to add citric acid. There was no significantvariation of yield between treatments of240kg/hm2phosphate fertilizer/2.6mmol/L citric acid and168 kg/hm2phosphate fertilizer/0.84kg/hm2citric acid, but additional228.12CNY/hm2economic efficiencyand0.0015ratio of output value were achieved, and the result showed that citric acid applied to improvethe economic benefits of the tomato.In conclusion, the application of citric acid reduced the soil pH, improved phosphate agronomicefficiency and the phosphate partial factor productivity, promoted the phosphate fertilizer in agricultureuse, inhibited the apparent utilization rate of decline of phosphate due to the application of phosphatefertilizer trends, improved phosphate physiological efficiency, promoted fruit phosphorus uptake,inhibited soil phosphorus in a fixed rate, and activated the soil phosphorus.The application of phosphatefertilization chould be reduced in a appropriate citric acid and obtain more economic benefits. |
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