Effects Of Irrigation With Reclaimed Water On Yield And Quality Of Pepper And Numerical Simulation Of Soil Ions

Based on the scientific problem of the mechanism of yield,quality,soil security and efficiency improvement of pepper under living reclaimed water irrigation,adopting the contrast experiment of both the general rotating combination design pot experiment and plot experiment.Taking domestic reclaimed water irrigates pepper as the breakthrough point,the thesis systematically researches the effects mechanism of reclaimed water quality for irrigation,irrigation quota,fertilizer amount on yield and quality of pepper;the cumulative regularity of metal ions and non-metal ions in soil-crop system in soil,root,stem,leaf and fruit of pepper;the migration and accumulation risk of heavy metals in soil under different scenarios.The research results provide a theoretical basis for the safety and feasibility of domestic reclaimed water irrigation of vegetables.The main research results are as follows:(1)In the condition of life reclaimed water irrigation,how to improve pepper’s quality and quantity by using proper fertilizer proportion of nitrogen,phosphorus and potassium,selecting fertilizer of nitrogen,phosphorus and potassium as 3 factors;adopting the quadratic general rotary unitized design field experiment;setting up a coupling model between pepper production and nitrogen,phosphorus and potassium;making the scheme of how to improve quality and the efficiency of life reclaimed water irrigation by optimizing N,P and K combination.The research results show as follows:①The pepper coupling model of N,P and K reaches a significant level,specifically shows that Nitrogen fertilizer has a significant effect on pepper yield,followed by phosphorus fertilizer and potassium fertilizer has a minimum effect.② The increase value of pepper yield decreases with the increase of nitrogen application rate,the sensitivity of phosphorus application rate to yield has the same trend as that of nitrogen application rate,and the sensitivity of potassium application rate to yield increased with the increase of nitrogen application rate.③ When x1=322.2 kg·hm-2,x2=134.3 kg·hm-2,x3=439 kg·hm-2,the maximum yield respectively is y1=45236.3 kg·hm-2,y2=15668.8 kg·hm-2,y3=20073.5 kg·hm-2.④ When nitrogen application rate is 240 kg·hm-2 and 150 kg·hm-2 P,the yield reaches 48911.9 kg·hm-2.The interaction function is obvious at this time.When nitrogen application rate is 240 kg·hm-2 and 150 kg·hm-2 K,the yield reaches 43523.7 kg·hm-2.When k is 150 kg·hm-2 and P is 92 kg·hm-2,the maximum yield is 18318 kg·hm-2.⑤The model shows that there are 29 optimized combinations with yield greater than 52000 kg·hm-2.(2)For the life of reclaimed water irrigation conditions how to use chili nitrogen,phosphorus and potassium fertilization ratio to improve the quality of crops,using quadratic general rotary unitized design of field experiment,established the chili each quality content and nitrogen,phosphorus and potassium coupling model,reveals the N,P,and K of reclaimed water irrigation of living quality factors in primary and secondary order,the interaction effect,the optimized combination scheme.① The coupling model of capsaicin with N,P and K was established.Through the analysis of main factor effect,it was concluded that the order of influencing factors on capsaicin content was nitrogen application(X1)>phosphorus application(X2)>potassium application(X3).②It established the capsaicin class matter and total N,P,K coupling model,analyses the main factors that effect,can be concluded that experiments on the impact of various factors on capsaicin class material in order to(x2)>K application rate of phosphoric fertilizer(x3)>nitrogen amount(x1).③ A coupling model of vitamin C content with N,P and K was established.According to the analysis of main factor effect,the order of effect of various factors on vitamin C content in pepper was phosphorus(X2)>potassium(X3)>nitrogen(X1).The nitrogen and potassium interaction could effectively improve the vitamin C content in pepper.When the nitrogen application amount was the highest and the potassium application amount was the lowest,the vitamin C content in pepper was 82.2 g·kg-1.When the nitrogen application amount increased and the potassium application amount decreased,the vitamin C content in pepper increased,showing a very strong interaction.The optimal combinations with vitamin C content greater than 100.83 g·kg-1 in pepper were obtained through simulation.(3)Pot experiment and plot experiment were used to study the effects of domestic reclaimed water irrigation on soil salt non-metal ions,metal ions and yield of pepper.The results showed as follows:①The content of non-metallic salt ions in the field plots showed different differences,and the content of sulfate ions in 0-40 cm soil of each treatment showed a decreasing trend with the increase of depth;The content of bicarbonate ion in 0-40 cm soil increased with the increasing depth.The average content of sulfate ions in 040 cm soil decreased with the increase of depth in bucket planting experiment.The average sulfate ion content of each treatment decreased gradually according to T4>T6>T5.The average content of bicarbonate ion in 040 cm soil of each treatment increased with the increase of depth.In the field experiment,the sulfate ion content in 20-40 cm soil was significantly different between reclaimed water irrigation and mixed water irrigation(P<0.05),and in the bucket experiment,the sulfate ion content in 20-40 cm soil was significantly different between different treatments(P<0.05).There was no significant difference in the average content of bicarbonate ions and the average content of bicarbonate ions in 20-40cm soil between different treatments and at different depths of the same treatment.② The decreasing order of yield of each treatment was:reclaimed water irrigation>mixed water irrigation>Yellow River water irrigation.In field experiment,the yield of pepper irrigated with reclaimed water was 26%higher than that irrigated with Yellow River water.The yield of pepper irrigated with mixed water was 11.6%higher than that irrigated with Yellow River water.The yield of pepper irrigated with reclaimed water was 12.9%higher than that irrigated with mixed water.In bucket planting experiment,the decreasing order of yield of each treatment was:reclaimed water irrigation>mixed water irrigation>Yellow River water irrigation.The yield of pepper irrigated with reclaimed water was 21.5%higher than that irrigated with Yellow River water.The yield of pepper irrigated with mixed water was 13.3%higher than that irrigated with Yellow River water.The yield of pepper irrigated with reclaimed water was 7.2%higher than that irrigated with mixed water.③It was found that there was a strong negative correlation between carbonate ion and sulfate ion,calcium ion and yield,and the correlation coefficient reached above 0.72.There were significant correlations between sulfate ions and calcium ions,chloride ions and sodium ions(P<0.05),indicating that soil salts were mainly calcium sulfate and sodium chloride salts.The correlation between cation and anion shows that sulfate ion has high positive correlation with sodium ion and potassium ion,bicarbonate ion has positive correlation with magnesium ion,chloride ion has positive correlation with calcium ion and potassium ion.Sulfate ions,chloride ions,calcium ions and sodium ions were positively correlated with pepper yield,while carbonate ions,bicarbonate ions,potassium ions and magnesium ions were negatively correlated with pepper yield.(4)The effects of reclaimed water irrigation on the accumulation of heavy metals in soil and the accumulation of heavy metals in pepper plants and fruit quality in soil-crop system were revealed by bucket cultivation and field plot contrast experiments respectively.The results showed that:① By quantifying the health risk of heavy metals in 0-10 cm surface soil under field and bucket irrigation conditions,the noncarcinogenic risk of all elements was less than 1,indicating that heavy metals do not pose a risk to human health.The ingestion pathway is the main risk pathway for children and adults,and the non-carcinogenic and carcinogenic risks caused by ingestion pathway in children are higher than the other two pathways.Total non-carcinogenic risk Indicates a higher total non-carcinogenic risk of chromium and arsenic in children and should be noted.In terms of carcinogenic risk,the carcinogenic risk of chromium to population is acceptable level.The carcinogenic risk of arsenic in children is acceptable;In addition,all heavy metals pose no risk to human health.② Under bucket cultivation,the chromium content in root,stem and leaf of pepper irrigated with reclaimed water was 1.85 mg/kg,1.61 mg/kg and 0.08 mg/kg,respectively,and the transfer amount of chromium content decreased according to the root,stem and leaf.The chromium content in root,stem and leaf of pepper irrigated with mixed water was 2.26 mg/kg,2.12 mg/kg and 0.48 mg/kg,respectively,and the transfer amount of chromium content decreased in order of root,stem and leaf.The contents of Lead,cadmium,Mercury and arsenic in different parts of pepper plants were significantly different(P<0.05),and the pepper leaves were more conducive to the accumulation of mercury.③ The content of capsaicin in reclaimed water irrigation and mixed water irrigation was higher in field cultivation condition,the content of capsaicin in reclaimed water irrigation was higher in barrel cultivation condition,and the content of capsaicin in tap water irrigation and mixed water irrigation were similar.The vitamin C content of pepper in field and barrel cultivation was significantly different(P<0.05),and barrel cultivation was more conducive to the formation of vitamin C in pepper.④Cadmium content in soil was positively correlated with cadmium content in roots and leaves of plants,but negatively correlated with cadmium content in stems of plants.Cadmium content in roots was negatively correlated with cadmium content in stems of plants(P<0.05),positively correlated with cadmium content in leaves of plants,and negatively correlated with cadmium content in stems and leaves of plants.Soil cadmium content was more conducive to the accumulation of cadmium content in roots of pepper plants.(5)Based on the typical farmland soil along the Yellow River in Zhongwei city,Ningxia;Carrying out indoor soil column of reclaimed water irrigation simulation test;the moisture front movement of soil column,the rule of cumulative infiltration volume and cumulative infiltration,and soil moisture content change are analyzed;Combined with numerical simulation method,analyzing the risk of migration and accumulation of heavy metals under different scenarios,main conclusions are as follows:①The moisture front migration process of three groups of soil column experiment basically accords with power function relationship,the wetting front migration velocity from high to low,in turn,the Yellow River>the first sewage treatment plant>the fourth sewage treatment plant.The reason for that is treated sewage containing suspended solids,which was gradually trapped by soil in the process of infiltration,blocking the voids in the soil and preventing the infiltration of water.② The water quality of the three tested water samples is relatively good.Long-term irrigation may lead to redistribution of soil heavy metal concentration,but will not lead to significant risk of heavy metal accumulation in soil and groundwater.After long-term sewage irrigation,mercury mainly concentrated in 0-5 cm surface layer,but arsenic mainly distributed in 120-180 cm soil layer.It can be seen that under the same condition,the risk of mercury accumulation mainly distributes in the surface soil,while the risk of arsenic accumulation mainly distributes in the deep soil.③After long-term sewage irrigation,the shallower the groundwater is,the higher the probability of arsenic accumulation in groundwater,but the mercury element will not lead to obvious groundwater pollution because of the large amount of adsorption by soil.