| Nowadays,the total amount of available water resources for farmland irrigation is decreasing,and the treatment of irrigation water resources is not perfect.Heavy metal ions in water will enter rice through rice roots and enter human body through rice,thus causing harm to human health.Therefore,in order to reduce the lead content in rice plants and achieve the standard of green rice,three kinds of modifiers,zeolite,rice husk biochar and corn straw biochar,were selected through pot experiment,and split plot experiment was adopted to study.According to the requirement of lead concentration in water quality standard of farmland irrigation,the concentration of lead in water was 0 mg/L and 0.2 mg/L for soil irrigation.The dosage of modifier was 10t/ha,and a group of non-modifier group was set as control group.All treatments were repeated three times.The effects of three amendments on soil physical and chemical properties,rice growth,rice yield and yield components,different parts of rice plant and lead content in soil were studied under the condition of whether or not lead was contained in water.The main results are as follows.(1)Lead content in water and amendments can have different effects on the physical and chemical properties of soil.Among them,the concentration of lead in water can significantly reduce the physical and chemical properties of soil,and the application of three amendments in soil can effectively increase the soil p H value,total nitrogen content,total phosphorus content and organic matter content.Under the condition of no lead concentration in water,the soil p H value increased by 2.04%,1.9% and 1.78%,the total phosphorus content increased by6.58%,12.7% and 5.45%,while the organic matter content increased by 7.01%,10.19% and8.29%,respectively.When the concentration of lead in water was high,the soil p H value increased by 2.52%,2.77% and 2%,the total phosphorus content increased by 9.8%,8.75%and 10.14%,and the organic matter content increased by 24.75%,24.17% and 24.02%,respectively.(2)Lead concentration in water and modifier have different effects on rice growth.Among them,the concentration of lead in water can reduce the total biomass of rice,and its effect is remarkable.Three amendments applied in soil can improve the effect of lead concentration in irrigation water on the total biomass of rice and promote the growth of total biomass of rice.The effects of three amendments on the total biomass of rice were significant.The tolerance index of rice plants is also affected by lead concentration and modifiers.Lead concentration in water can decrease the tolerance index of rice plant,but the tolerance index of rice plant can be increased by applying amendment in soil.The tolerance index of rice plants increased by 18.81%,15.60% and 13.15% respectively when the lead-freeconcentration in water was applied to soil,while the tolerance index of rice plants increased by 20.01%,19.88% and 20.79% when the lead concentration in water was applied.The above data show that the effect of zeolite on the tolerance index of rice plant is the most obvious when there is no lead concentration in water,and the effect of corn straw biochar on the tolerance index of rice plant is the most obvious when there is lead concentration in water.(3)Lead concentration in water and modifier have different effects on Rice Yield and yield components.All three amendments applied in soil could increase rice yield,but lead concentration in water could decrease rice yield.The effective panicles of rice increased by13.81%,24.15% and 17.27% respectively after applying three amendments in soil without lead concentration in water;the grain number per panicle of rice increased by 15.33%,14.34% and 19.24% respectively;the 1000-grain weight of rice increased by 20.68%,12.31%and 8.73% respectively;and the theoretical yield of rice increased by 35.05%,35.39% and34.82% respectively.Under the condition of lead concentration in water,the effective panicles of rice increased by 5.26%,5.26% and 8.79% respectively after applying three amendments in soil;the grain number per panicle of rice increased by 21.09%,15.99% and 16.10%respectively;the 1000-grain weight of rice increased by 9.96%,12.08% and 10.91%respectively;the theoretical yield of rice increased by 24.61%,7.84% and 4.99%,respectively.Compared with the rice irrigated without lead concentration,the effective panicle number of rice irrigated with lead concentration decreased by 1.71%,the grain number per panicle decreased by 6.27%,the 1000-grain weight of rice decreased by 5.06%,and the theoretical yield of rice decreased by 3.66%.(4)Lead concentration in water and modifier had different effects on lead content in different parts of rice plant and soil,and the effects were significant.Lead concentration in water can change the physical and chemical properties of soil and increase the content of lead in all parts of rice plant and paddy soil.Adding amendments to soil can absorb lead ions and reduce the fluidity of lead content,thus reducing the content of lead in all parts of rice plant and soil.Under the condition of lead-free irrigation,the lead content in soil decreased by11.03%,9.39% and 9.37%,respectively,while that in rice roots decreased by 19.19%,14.79%and 21.25%,while that in rice stems decreased by 15.13%,22.31% and 15.58%,and that in rice leaves decreased by 13.08%,15.27% and 16.76%,respectively.The lead content in the samples decreased by 12.83%,8.56% and 9.63%,respectively.Under the condition of irrigation with lead concentration,the contents of lead in paddy soil decreased by 15.97%,15.25% and 17.53%,respectively,while the contents of lead in rice roots decreased by23.96%,28.91% and 26%,the contents of lead in rice stems decreased by 21.52%,24.86%and 24.46%,and the contents of lead in rice leaves decreased by 22.34%,22.61% and 23.94%,respectively.The lead content in rice decreased by 14.07%,13.06% and 14.57% respectively.The lead content in rice was lower than the national food safety standard(0.2mg/kg).In conclusion,the addition of zeolite,rice husk Biocharcoal and corn straw Biocharcoal in soil can reduce the effects of lead concentration in water on soil physical and chemical properties,rice growth characteristics,rice yield and lead content in different parts of rice plant,which provides a reference for meeting food security standards and reducing the impact of lead ion on rice pollution. |
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