Distribution of available soil water capacity in China

The available soil water capacity (ASWC) is important for studying crop production, agro-ecological zoning, irrigation planning, and land cover changes. Laboratory determined data of ASWC are often not available for most of soil profiles and the nationwide ASWC largely remains lacking in relevant soil data in China. This work was to estimate ASWC based on physical and chemical properties and analyze the spatial distribution of ASWC in China. The pedo-transfer functions (PTFs), derived from 220 survey data of ASWC, and the empirical data of ASWC based on soil texture were applied to quantify the ASWC. GIS technology was used to develop a spatial file of ASWC in China and the spatial distribution of ASWC was also analyzed. The results showed the value of ASWC ranges from 15 × 10-2 cm3·cm-3 to 22 × 10-2 cm3·cm-3 for most soil types, and few soil types are lower than 15 × 10-2 cm3·cm-3 or higher than 22 × 10-2 cm3·cm-3. The ASWC is different according to the complex soil types and their distribution. It is higher in the east than that in the west, and the values reduce from south to north except the northeastern part of China. The "high" values of ASWC appear in southeast, northeastern mountain regions and Northeast China Plain. The relatively "high" values of ASWC appear in Sichuan basin, Huang-Huai-Hai plain and the east of Inner Mongolia. The relatively "low" values are distributed in the west and the Loess Plateau of China. The "very low" value regions are the northern Tibetan Plateau and the desertified areas in northern China. In some regions, the ASWC changes according to the complex topography and different types of soils. Though there remains precision limitation, the spatial data of ASWC derived from this study are improved on current data files of soil water retention properties for Chinese soils. This study presents basic data and analysis methods for estimation and evaluation of ASWC in China.

Use of Fe/Al drinking water treatment residuals as amendments for enhancing the retention capacity of glyphosate in agricultural soils

Fe/Al drinking water treatment residuals（WTRs）, ubiquitous and non-hazardous by-products of drinking water purification, are cost-effective adsorbents for glyphosate. Given that repeated glyphosate applications could significantly decrease glyphosate retention by soils and that the adsorbed glyphosate is potentially mobile, high sorption capacity and stability of glyphosate in agricultural soils are needed to prevent pollution of water by glyphosate.Therefore, we investigated the feasibility of reusing Fe/Al WTR as a soil amendment to enhance the retention capacity of glyphosate in two agricultural soils. The results of batch experiments showed that the Fe/Al WTR amendment significantly enhanced the glyphosate sorption capacity of both soils（p 〈 0.001）. Up to 30% of the previously adsorbed glyphosate desorbed from the non-amended soils, and the Fe/Al WTR amendment effectively decreased the proportion of glyphosate desorbed. Fractionation analyses further demonstrated that glyphosate adsorbed to non-amended soils was primarily retained in the readily labile fraction（Na HCO3-glyphosate）. The WTR amendment significantly increased the relative proportion of the moderately labile fraction（HCl-glyphosate） and concomitantly reduced that of the Na HCO3-glyphosate, hence reducing the potential for the release of soil-adsorbed glyphosate into the aqueous phase. Furthermore, Fe/Al WTR amendment minimized the inhibitory effect of increasing solution p H on glyphosate sorption by soils and mitigated the effects of increasing solution ionic strength. The present results indicate that Fe/Al WTR is suitable for use as a soil amendment to prevent glyphosate pollution of aquatic ecosystems by enhancing the glyphosate retention capacity in soils.

Using ^(137)Cs technique to quantify soil conservation capacities of different ecosystems in Wolong Natural Reserve, southwestern China

Reliable information about soil conservation capacities of different natural ecosystems is an important reference for the design of targeted erosion and sediment control strategies. The objective of this paper is to quantify the soil conservation capacities of different natural ecosystems that can represent dif-ferent climatic zones. The 137Cs technique has been used to estimate soil redistribution rates in differ-ent natural ecosystems over the past 40 years in Wolong Nature Reserve. The reserve, transiting from the Chengdu plain to the Qinghai-Tibet plateau, maintains rich ecosystems from subtropical to frigid. The net soil erosion rates of 5 selected ecosystems that represent a warm coniferous-broadleaf-mixed forest, a cold-resistant deciduous taiga forest, a cold-resistant shrub, an evergreen cold-resistant taiga forest, and an alpine meadow are 0.17, 0.16, 0.13, 0.11 and 0.06 kg·m-2·a-1, respectively. Their soil con-servation capacities are reversed in order. The reference inventories for ^(137)Cs in different ecosystems range from 1658 to 3707 Bq·m-2 with the altitude. Results of this study indicate that any attempt to de-velop effective erosion and sediment strategies in areas with similar climates should consider natural ecosystem types.