Dynamic change and diagnosis of physical, chemical and biological properties in bauxite residue disposal areas

Vegetation encroachment occurred in bauxite residue disposal area(BRDA)following natural weathering processes,whilst the typical indicators of soil formation are still uncertain.Residue samples were collected from the BRDA in Central China,and related physical,chemical and biological indicators of bauxite residue with different storage years were determined.The indicators of soil formation in bauxite residue were selected using principal component analysis,factor analysis,and comprehensive evaluation to establish soil quality diagnostic index model on disposal areas.Following natural weathering processes,the texture of bauxite residue changed from silty loam to sandy loam.The pH and EC decreased,whilst porosity,nutrient element content and microbial biomass increased.The identified minimum data set(MDS)included available phosphorus(AP),moisture content(MC),C/N,sand content,total nitrogen(TN),microbial biomass carbon(MBC),and pH.The soil quality index of bauxite residue increased,and the relative soil quality index decreased from 1.89 to 0.15,which indicated that natural weathering had a significant effect on improveing the quality of bauxite residue and forming a new soil-like matrix.The diagnostic model of bauxite residue was established to provide data support for the regeneration on disposal area.

Effects of Different Tree Species and Proportions on Soil Fertility Quality in Eucalyptus Mixed Plantation

In order to study the effects of Eucalyptus mixed plantation with different mixed tree species and mixed proportion on soil nutrient accumulation and fertility quality, Eucalyptus-Mytilaria laosensis and Eucalyptus-Magnolia sumatrana mixed plantations in Guangxi State-owned Qipo Forest Farm were selected as the research objects. Based on 15 conventional soil fertility indexes, the minimum data set and membership function method were used to evaluate the soil fertility quality of mixed plantations with different structures. The results showed that compared with pure forest, the soil organic matter, total nitrogen, total potassium, alkali hydrolyzable nitrogen, available phosphorus, available potassium and other nutrients of mixed plantations with different treatments were significantly increased, and the contents of Cu and Zn in trace elements were most significantly increased. Compared with pure forest, the soil fertility quality of mixed plantations with different structures was significantly improved. The treatment with the highest soil fertility quality was 25% of Eucalyptus-M. sumatrana mixed plantation. When formulating production and management strategies, it can refer to construction measures of the mixed plantation to ensure the sustainability of forest soil fertility, and promote the healthy and sustainable development of Eucalyptus plantation and downstream industries in Guangxi.

Current State and Development of the Soil Health Index in Localities with Various Soil-Climatic Conditions in the Slovak Republic

The aim of the study was to assess the current state and development of the Soil Health Index (SHI) at 13 localities with various soil-ecological conditions in the Slovak Republic. The SHI was developed using a minimum soil data set, physical and chemical soil parameters in combination with environmental parameters (land use, gradients). The SHI is one numerical value accumulates information about the state of soil health and its ability to provide soil functions and thus ecosystems in the optimal range. The highest SHI values were determined at model localities used as arable land (Haplic Chernozem, Fluvisol) located in a warm climate at altitudes up to 200 meters above sea level. Ecosystems with very low and low value are mostly grasslands with mildly cold climate (Cambisol) and considerable slope, agroecosystem on low organic matter (Arenosol). Arable ecosystem SHI is also reduced in areas of geochemical anomalies and areas with anthropogenic load, where there is a higher content of risk elements. The SHI changes are mainly the result of changes in dynamic indicators such as soil response and soil bulk density.

The Determinants of China's Minimum Wage Rates

We use a highly disaggregated panel of macro data and minimum wages at the county level to investigate the processes behind minimum wage adjustments in China.Relying on random effects models,spatial econometrics techniques,and multilevel analyses,we document that a comparatively small number of economic variables-including the local price level and GDP per capita-are important determinants of minimum wage rates.Interactions between adjacent counties and counties of the same administrative type,and centralized mechanisms,particularly at the provincial level,also play an important role in explaining the variance in minimum wage rates across counties.Finally,we show that China's provinces are the key players for setting minimum wage rates and that,when they do so,they are not uniform in the way they weigh different economic variables.

Quantitative Assessment of Soil Health Under Different Planting Patterns and Soil Types

Soil health assessment is an important step toward understanding the potential effects of agricultural practices on crop yield, quality and human health. The objectives of this study were to select a minimum data set for soil health evaluation from the physical, chemical and biological properties and environmental pollution characteristics of agricultural soil and to develop a soil health diagnosis model for determining the soil health status under different planting patterns and soil types in Chongming Island of Shanghai, China. The results showed that the majority of the farmland soils in Chongming Island were in poor soil health condition, accounting for 48.9% of the survey samples, followed by the medium healthy soil, accounting for 32.2% of the survey samples and mainly distributed in the central and mid-eastern regions of the island. The indicators of pH, total organic carbon, microbial biomass carbon and Cd exerted less influence on soil health, while the soil salinization and nitrate accumulation under a greenhouse cropping pattern and phosphate fertilizer shortage in the paddy field had limited the development of soil health. Dichlorodiphenyltrichloroethanes, hexachlorocyclohexanes and Hg contributed less to soil health index (SHI) and showed no significant difference among paddy field, greenhouse and open-air vegetable/watermelon fields. The difference of the SHI of the three soil types was significant at P = 0.05. The paddy soil had the highest SHI values, followed by the gray alluvial soil, and the coastal saline soil was in a poor soil health condition, indicating a need to plant some salt-tolerant crops to effectively improve soil quality.

Pore Size Distribution as a Soil Physical Quality Index for Agricultural and Pasture Soils in Northeastern Iran

Assessment of soil quality is important for optimum production and natural resources conservation. Agricultural and pasture soil qualities of Deh-Sorkh region located at south of Mashhad, northeastern Iran were assessed using the integrated quality index (IQI) and Nemero quality index (NQI) models in combination with two datasets, i.e., total data set (TDS) and minimum data set (MDS). In this study 6 soil properties considered as MDS were selected out of 18 properties as TDS using principle component analysis. Soil samples were divided into 3 groups based on optimum ranges of 8 soil physical quality indicators. Soil samples with the most indicators at optimum range were selected as group 1 and the samples having fewer indicators at optimum range were located in groups 2 and 3. Optimum ranges of soil pore size distribution functions were also determined as soil physical quality indices based on 8 soil physical quality indicators. Pore size distribution curves of group 1 were considered as the optimum pore size functions. The results showed that relatively high organic carbon contents could improve pore size distribution. Mean comparisons of soil physical quality indicators demonstrated that mean weight diameter of wet aggregates, structural stability index, the slope of moisture retention curve at inflection point, and plant available water content in agricultural land use decreased significantly in relation to pasture land use. In addition, the results demonstrated that the studied MDS could be a suitable representative of TDS. 78% of pasture soils had the optimum pore size distribution functions, while this parameter for agricultural soils was only 13%. In general, the soils of the studied region showed high limitations for plant growth according to the studied indicators.