Research On Tomato Growth And Quality With Sewage Irrigation

The effects on the soil and crop of pollutants have attracted a lot attention in sewage irrigation. The experiment in the greenhouse was designed to show the influence on the tomato growth, output and quality. We also discussed the distribution and accumulation rule of elements Hg and As in the superficial soil layer and tomato.Compared to the clear water irrigation,①the sewage irrigation had significiant influence on the diurnal changing of tomato height and stalk. The average height and stalk of the sewage treatment was lower than the comparison. The tomato growth was strongly prevented by the sewage, and the later period growth was obviously slowed down. It had the certaininhibitory action on tomato's growth;②The sewage irrigation was advantageous to reduce the first inflorescence setting position of tomato, and reduce the fruit setting rate, then finally affect the output: the output of the autumn stubble with wastewater and sanitary water irrigation reduced by 7.68% and 2.47% separately; While the output of the spring stubble reduced by 21.48% and 14.69%;③Compared to clear water irrigation, the irrigation with wastewater had significiat influence on tomato fresh weight on the soil. The research on tomato roots showed that sewage irrigation can enhance the tomato to accumulate less dry mass in the certain degree, but the rule of the tomato root system's growth is not very obvious. Tomato root system's crowded level showed the tendency of gradually densed and the root system volume of the sewage treatment got a larger tendency during the growing period, which conforms to the tomato growth demand. In tomato's earlier period sample, the root–top ratio of various sewage treatments were slightly smaller than the comparison. The root system's function was weakening along with the growth duration and the proportion of root system and the crown department was also gradually reduced. The root–top ratio of two kinds of sewage irrigation had small discrimination in the later period, which had significiant difference with the comparison.④Various targets of the tomato quality had the remarkable difference: The content of soluble sugar was lower than the comparison on the value, which explained that the sewage irrigation was disadvantageous to the tomato's sugar accumulation under this soil texture condition. The soluble sugar content of later period sample was higher than the earlier period sample. The sewage irrigation may enhance the tomato Vc content in the certain degree, but Vc content in the spring stubble was smaller than the autumn stubble. The Vc content in the tomato young fruit is very high, but later the content dropped gradually. The sewage irrigation was disadvantageous to the protein synthesis in the certain degree. On the acid content, each processing differred not in a big way with the comparison in the quantity, but the difference was remarkable. This explained that such kind of soil texture condition had no adverse effect on the acidity synthesis, but the acid content of later sample was higher than the earlier sample. The soluble solid of two sewage treatments was higher than the comparison, which showed that the sewage irrigation could enhance soluble solid in the certain degree. The value of sugar/acid had remarkable differenc with each other. Tomato's sugar/acid of spring stubble was higher than the fall stubble, and value of the sewage treatment was higher than the sanitary water.⑤The heavy metals Hg and As did not transform obviously in the soil-crop system. Hg and As gatthered differently in the soil after the sewage irrigation. Significant variant of soil heavy metals concentrations between different soil layers were discovered in the experiment. Element As accumulatd more than element Hg, and the content of Hg and As was higher in sewage treatment than the comparison. Regression analysis showed strong correlations between heavy metals after sewage irrigation. The soil environment was deeply impacted with exterior pollutants, and risk of complex pollution still exits in the area, which showed the quality of soil envioment could decrease after few years'sewage irrigation. Single factor appraisal to the polutants showed that the Polution indexes of Hg and As were smaller than 1. The value was still in the scope of the satandard quality and the soil was clear enough. The element left in the tomato showed higher selectivity to the element As than Hg and thia can satisfy the state food safety standard.