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Derivation of soil Pb/Cd/As thresholds for safety of vegetable planting: A case study for pakchoi in Guangdong Province, China
LI Fu-rong, WEN Dian, WANG Fu-hua, SUN Fang-fang, WANG Xu, DU Ying-qiong, LIU Xiang-xiang, WAN Kai
2019, 18 (1): 179-189.   DOI: 10.1016/S2095-3119(18)61975-6
Abstract262)      PDF in ScienceDirect      
Regional guidelines for soil heavy metals, in conjunction with specific crops, are proposed to better assess soil environmental quality.  In this study, large amounts of soils with different levels of Pb/Cd/As pollution were collected in Guangdong Province, China, to carry out a pot experiment, which was closer to the actual situation and properties of the heavy metal contaminated soils.  Taking the widely planted vegetable pakchoi as the research object, we analyzed the correlations between the Pb/Cd/As concentrations in pakchoi and the total or available soil Pb/Cd/As concentrations and established their optimal regression equations.  And then, the total and available soil Pb/Cd/As thresholds for pakchoi were calculated according to the allowable Pb/Cd/As limits in pakchoi and were compared with the current soil assessment standards.  Furthermore, a lot of paired vegetable-soil samples in field were collected and their pollution situations were assessed by both the current limit thresholds and the calculated thresholds.  Obviously, it was more consistent to assess the Cd and As pollution situation of the vegetable and soil samples with the calculated soil thresholds than the current soil assessment thresholds.  It further proved that it was necessary to explore the soil heavy metal thresholds for safety of vegetable in specific regions, which would be more scientific and practical to guide safety production of local agricultural products and effective utilization of soil resources.
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The Effects of Farmyard Manure and Mulch on Soil Physical Properties in a Reclaimed Coastal Tidal Flat Salt-Affected Soil
ZHANG Jian-bing, YANG Jing-song, YAO Rong-jiang, YU Shi-peng, LI Fu-rong , HOU Xiao-jing
2014, 13 (8): 1782-1790.   DOI: 10.1016/S2095-3119(13)60530-4
Abstract1663)      PDF in ScienceDirect      
Careful soil management is important for the soil quality and productivity improvement of the reclaimed coastal tidal flat saline land in northern Jiangsu Province, China. Farmyard manure (FYM) and mulch applications, which affect soil characteristics and plant significantly, are regard as an effective pattern of saline land improvement. As a conventional management in the study region, FYM and mulch are used for the amendment of the new reclaimed tidal flat regularly, but little is known about their effects on soil physical properties functioning. A study was conducted on a typical coastal tidal flat saline land, which was reclaimed in 2005, to evaluate the effects of FYM, polyethylene film mulch (PM), straw mulch (SM), FYM combined with PM (FYM+PM), FYM combined with SM (FYM+SM), on soil hydraulic properties and soil mechanical impedance. CK represented conventional cultivation in study area without FYM and mulch application and served as a control. The experiment, laid out in a randomized complete block design with three replications, was studied in Huanghaiyuan Farm, which specialized in the agricultural utilization for coastal tidal flat. Result showed that capillary water holding capacity (CHC), saturated water content (SWC), saturated hydraulic conductivity (Ks) and bulk density (BD), cone index (CI) were affected significantly by the FYM and mulch application, especially in the 0-10 cm soil layer. FYM and mulch management increased CHC, SWC and Ks over all soil depth in the order of FYM+SM>FYM+PM>FYM>SM>PM>CK. With the contrary sequence, BD and CI decreased significantly; however, FYM and mulch application affected BD and CI only in the upper soil layers. CHC, SWC and Ks decreased significantly with the increasing of soil depth, BD and CI, and a significant liner equation was found between CHC, SWC, Ks and BD, CI. With the highest CHC (38.15%), SWC (39.55%), Ks (6.00 mm h-1) and the lowest BD (1.26 g cm-3) and CI (2.71 MPa), the combined management of FYM and SM was recommend to be an effective method for the melioration of reclaimed coastal tidal flat saline soil.
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