[Characteristics of acidification and the distribution of available phosphorus along soil depths in heavy clay soils in southern Henan Province, China]. / è±«å—é»æ¿åœŸå£¤åˆ†å±‚é ¸åŒ–å’Œè€•å±‚é€Ÿæ•ˆç£·åˆ†å¸ƒç‰¹å¾.

The acidification of agricultural soil in the southern part of the North China Plain has become more obvious, which is particularly true for the heavy clay soil types, such as yellow-cinnamon and lime concretion black soils. To understand the spatial variability of the pH value and nutrients on the vertical agricultural soil profile of heavy clay soils in this area, we measured pH values and available phosphorus (AP) in 63 farmland sample points from Xiping County in the southern Henan Province. Geostatistical methods and ArcGIS technology were used to map soil pH values along three soil depths (0-10, 10-20, and 20-30 cm) and the spatial distribution of soil AP in the tillage layer (0-20 cm). Furthermore, the correlation between pH and AP was analyzed. The results showed that mean pH values of typical yellow-cinnamon and typical fluvo-aquic soils from three soil layers were 4.98, 4.93, 5.31, and 5.46, 5.81, 6.26, respectively, which gradually increased with soil depths. However, there was no significant difference among the three soil layers. Mean pH values of typical lime concretion black soil from the three soil layers were 5.23, 5.43 and 6.03, respectively, and that of the 20-30 cm soil layer was significantly higher than that of the 0-10 cm (by 0.8-1 pH unit) and the 10-20 cm layers. The pH of the 20-30 cm soil layer of the calcareous lime concretion black and moist soils were also significantly higher than that of the 0-10 and 10-20 cm soil layers. The AP contents of the typical yellow-cinnamon, typical lime concretion black, moist, typical fluvo-aquic and calcareous lime concretion black soils in 0-20 cm soil layer were 8.85-54.75, 4.27-37.49, 8.22-51.80, 6.07-34.82, and 13.22-22.85 mg·kg-1, respectively. The results of the map indicated that the areas with low AP were distributed in the middle of the study area in blocks, and the areas with high AP were distributed around the study area in dots and flakes. The pH values of the typical yellow-cinnamon, typical lime concretion black, and moist soils positively correlated with the content of AP in the 0-20 cm soil layer. In conclusion, the heavy clay soil in southern Henan Province became stratified acidification, which slowed down along the soil depth. Soil AP contents in the tillage layer were distributed unevenly in the study area, and were affected by soil types and soil pH. These results would be useful for the improvement of heavy clay soil acidification in the southern part of the North China Plain.

Island soil quality assessment and the relationship between soil quality and land-use type/topography.

Information about the soil quality of different land-use types and topographies is essential for the sustainable development, utilization, and protection of soil resource in coastal areas. In this study, representative topsoil samples were collected from Liandao Island, China, and soil water content (SWC), soil bulk density (BD), total nitrogen (TN), soil organic matter (SOM), ammonium nitrogen (NH4+-N), nitrate nitrogen (NO3--N), available phosphorus (AP), available potassium (AK), soil salt content (SSC), and pH were recorded. The suitable minimum soil data set (MDS) was computed by principal component analysis (PCA) and the soil quality index (SQI) was then determined. The spatial distribution of the SQI was analyzed using ordinary kriging interpolation. The effects of topographical parameters (digital elevation model [DEM], slope, and aspect) and land-use types (vegetation [V], water resource conservancy land [WRC], sandy land [SL], unused land [UL], and built-up land [BL]) on SQI were then analyzed in detail. The parameters included in the MDS were TN, pH, and BD, which together accounted for 84.371% of the variation in soil quality. The SQI varied from 0.189 to 0.772 in the study area. The correlation coefficients between SQI and DEM, slope, and aspect were 0.498, 0.294, and 0.137, respectively (p < 0.01). The highest SQI score was found at an elevation of 110 m, with a slope of 68.2° and an aspect of 246.6, in the vegetation land-use type. Soil quality differed significantly (p = 0.0000) among the land-use types, with the following ranking: V > UL > SL > BL. Our results provide land managers with an important reference for the development, utilization, and protection of soil resource in coastal zones such as Liandao Island, China.

[Spatial variability of nutrients and heavy metals in paddy field soils based on GIS and Geostatistics.] / 基于GISå’Œåœ°ç»Ÿè®¡å­¦çš„ç¨»ç”°åœŸå£¤å »åˆ†ä¸Žé‡é‡‘å±žç©ºé—´å˜å¼‚.

Based on a grid (25 m X 25 m) equidistant sampling, the spatial variability of pH, organic matter, total nitrogen, available phosphorus, CEC and three typical heavy metal elements Cd, As and Pb in soil tillage layer (0-20 cm) were analyzed by using GIS and Geostatistics in the paddy field of 3.56 hm2 in Beishan Town, Changsha County, Hunan Province. The results showed that soil pH value and Pb content showed weak variation, and other indexes showed moderate variation. The order of variation was following available phosphorus ＞ Cd ＞ total nitrogen ＞ organic matter ＞ CEC ＞ As ＞ Pb ＞ pH. Results of the semi-variance test showed that the best fitting model of the semi-variance function of organic matter, available phosphorus and As was exponential, and the best semi-variance function of pH, total nitrogen, CEC, Cd, Pb was spherical. All the indicators had a strong spatial correlation except for CEC, which showed moderate spatial correlation. Kriging interpolation analysis showed that pH, total nitrogen, CEC, Pb were plaque distribution, while organic matter, available phosphorus, Cd and As were block and banded distribution. Vegetation, topography and human activities were the main factors driving the variation of soil nutrients and heavy metals in the study area. The correlation between soil nutrients and heavy metals content was significant, among which pH and organic matter, Cd and Pb reached a very significant correlation level.

[Spatial variation of soil phosphorus in flooded area of the Yellow River based on GIS and geo-statistical methods: A case study in Zhoukou City, Henan, China.] / 基于GIS和地统计学的黄泛区土壤磷空间变异­­ä»¥å‘¨å£ä¸ºä¾‹.

Soil phosphorus is an important indicator to measure the soil fertility, because the content of soil phosphorus has an important effect on physical and chemical properties of soil, plant growth, and microbial activity in soil. In this study, the soil samples collecting and indoor analysis were conducted in Zhoukou City located in the flooded area of the Yellow River. By using GIS combined with geo-statistics, we tried to analyze the spatial variability and content distribution of soil total phosphorus (TP) and soil available phosphorus (AP) in the study area. Results showed that TP and AP of both soil layers (0-20 cm and 20-40 cm) were rich, and the contents of TP and AP in surface layer (0-20 cm) were higher than in the second layer (20-40 cm). TP and AP of both soil layers exhibited variation at medium level, and AP had varied much higher than TP. TP of both layers showed medium degree of anisotropy which could be well modeled by the Gaussian model. TP in the surface layer showed strong spatial correlation, but that of the second layer had medium spatial correlation. AP of both layers had a weaker scope in anisotropy which could be simulated by linear model, and both soil layers showed weaker spatial correlations. TP of both soil layers showed a slowly rising change from southwest to northeast of the study area, while it gradually declined from northwest to southeast. AP in soil surface layer exhibited an increase tendency firstly and then decrease from southwest to the northeast, while it decreased firstly and then increased from southeast to the northwest. AP in the second soil layer had an opposite change in the southwest to the northeast, while it showed continuously increasing tendency from northwest to the southeast. The contents of TP and AP in the surface layer presented high grades and the second layer of TP belonged to medium grade, but the second layer of AP was in a lower grade. The artificial factors such as land use type, cropping system, irrigation and fertilization were the main factors influencing the distribution and spatial variation of soil phosphorus in this area.