Effects of sheep manure on Hg concentrations in grape vines

【Objectives】 The paper is to study the effects of applying different amounts of sheep manure on Hg accumulation in different parts of grape vines during different growing periods at different Hg addition rates in soil. 【Methods】 The experiment was conducted in the lab by using pots. Each pot contains 15 kg dry soil ( 5 mm). Three different concentrations of Hg (0, 1.5, 25 mg/kg) were added in the form of HgCl2 solid powder into the soil. Each level of Hg treatment was compared between application of 12.5% (12.5% sheep manure vs 87.5% soil) of sheep manure and no sheep manure. At 15 days after mixing, a disease-free and strong grape plant was planted in each pot on April 8, 2015. Each treatment repeated 6 times.【Results】 The results showed that mercury contents in grape fruits, flowers, vines and leaves were significantly increased with the increase of soil Hg contents for all the treatments. However, the Hg accumulation rates vary dramatically in different parts of grape plants in the following order: leavesflowersvinesfruits. Mercury contents and their accumulation rates in vines and leaves were the highest during early fruit stage and the lowest during late fruit stage with or without sheep manure applications. The mercury concentrations in flowers, leaves, vines and fruits with sheep manure in the soil were lower than those without the sheep manure and the decreasing rates of Hg concentrations in the grape plants at the higher addition of Hg in soils are greater than those at the lower addition of Hg in the soils. Comparing to the treatments with no sheep manure, the Hg concentrations in the grape leaves with sheep mature treatments were decreased by 26%, 29.7% and 37%, respectively, during flowering, early fruit growth and late fruit growth periods. The decrease of Hg contents in the vines during flowering stage was greater than other growth stages with sheep manure application at low Hg stress and the Hg content was reduced by 69.16% comparing to no manure treatment. However, Hg content in the vines was reduced by 50.52%, 58.33% and 48.35%, respectively, during flowering period, early fruit growth and late fruit growth periods with organic fertilization comparing with no fertilization. Applying sheep manure in soils can reduce Hg accumulation in different parts of the grape plants significantly, especially under high Hg stress in soils. 【Conclusions】 Application of organic fertilizer in soils that are contaminated with Hg significantly reduces the Hg content in different parts of grape vine.