Effects Of Different Soil Amendments On The Growth Of Peach Trees And Concentration Of Cr In Plant Under Different Levels Of Cr Stress In Soil

The pollution of heavy metal in soil has been becoming more serious at present.As one of the important pollution elements in soil and water,chromium has been a threat to the safety and green production of the orchard.In-situ remediation by amendments is one of the effective approaches to decrease the amount of heavy metal existed in soils.Based on two-year-old peach trees ‘lu xing/wild peach'(Amydalus persica Linn.)as the research object,the pot experiment was conducted to study the effects of organic manure?biochemical fulvic acid potassium?activated carbon?bio-carbon?nano-carbon on peach tree's growth,physical and biochemical conditions and Cr absorption amount,soil enzyme activities and Soil Physics and Chemical Proper of Cr contaminated soil under different levels of Cr stress in order to elucidate the mechanism of Cr injury and the remission of soil amendments to peach tree.The main results are as follows: 1.With increasing Cr stress level,peach trees showed a decreasing trend on the chlorophyll content,photosynthesis,increasing of trunk girth and amount of dry mass accumulation.Cr stress had effects on physiological and biological activities of peach tree plant.The activities of the peach tree's protective enzyme(SOD,POD,and CAT)decreased and MDA concentration increased under high concentration of Cr.The activities of soil enzyme in Cr contaminated soils decreased.Under the Cr stress of high concentration(150mg/kg),the activities of soil urease,invertase,phosphatase and catalase were decreased by 40.1%,18.9%,43.9% and 39.5% compared with the comparison respectively.The concentration of Cr in various organs of the plant significantly increased under Cr stress.The Cr content in various parts of peach tree is different,generally expressed as coarse root> fine root> stem >leaf >new tip and phloem >xylem in the same part.2.Compared with biochemical fulvic acid potassium and activated carbon,organic manure had the best relieving effect caused by Cr stress.Under different Cr stress,application of organic manure could mitigate the impact of Cr stress on the growth of young peach trees to some extent and increase plant biomass and alleviate the inhibitory effect of Cr on soil enzyme activities.The activities of urease,phosphatase,catalase and protease except invertase by applying organic manure were significantly higher than those of no amendment treatment.Determination of Cr in plant samples was studied by ICP-Ms using microwave digestion.It is shown that under exogenous Cr stress,applying organic manure could significantly reduce the accumulation of Cr.Under high Cr dosage stress in soil,the concentration of Cr in each part of the peach tree after organic manure application decreased by 39.3~85.3% lower than no amendment application.Biochemical fulvic acid potassium had less effect on alleviating the injury by Cr stress.The application of activated carbon could obviously mitigate the injury in peach trees by Cr stress in early days.However,for some reasons,the effects gradually subsided during middle and late period.3.The study of the effect of bio-carbon,activated carbon and nano-carbon on the growth of peach tree and the repairing effect of chromium showed that,applying soil amendments could relieve the inhibitory effect on soil enzyme caused by Cr,and the relieving effect of BC was better than of AC and NC.The activities of urease,invertase and catalase after BC application increased by 65 %,49%and53%more than no soil amendment application under middle concentration treatment(Cr1).Under high stress(Cr2),the activities of urease after BC application were 1.65 times of the control.In generally,the influence of different soil amendments on total Cr content in peach tree was significant(p<0.05)compared with the control,the total amount of Cr in plant were reduced by 11.5%,36.7% and 41.5%,after BC,AC and NC were applied under the Cr1 treatment.BC shared the most efficiently result under the Cr2 treatment,reducing 51.2% than the control.Adding soil amendments greatly alleviated the inhibited effect of protective enzyme activity caused by Cr stress.With different Cr treatment,different soil amendments greatly decreased the amount of MDA compared to the control,following the decreasing order: BC>AC>NC.The application of soil amendment could effectively increase peach tree's shoot length and dry weight.In the study,groups treated with BC had the best production effect,followed by groups treated with AC and NC under the same concentration of Cr treatment.4.We studied the content of heavy metal in 16 different peach-orchards,which under the conventional fertilization and management level.Results showed that,Cd?Cr?Cu?Pb?Ni and Zn were all found on the 16 peach production areas.After multiple factors comprehensive evaluation,most of the orchards belonged to the clean orchard,while the heavy metal pollution of Yunnan peach producing areas reached warning level.The single factor pollution indictor of Ni was the biggest among all the elements,which made it critical for pollution abatement and detection.