Knowledge and management of soil pH, particularly soil acidity across spatially variable soils is important, although this is greatly ignored by farmers. The objective of the study was to evaluate in-field spatial var...Knowledge and management of soil pH, particularly soil acidity across spatially variable soils is important, although this is greatly ignored by farmers. The objective of the study was to evaluate in-field spatial variability of soil pH, and compare the efficiency of managing soil pH through site-specific method vs. uniform lime application. The study was conducted on three sites with study sites I and II （23°50＇ S; 29°40＇ E）, and study sites IIl （23°59＇ S; 28°52＇ E） adjacent to each other in the semi-arid regions of the Limpopo Province, South Africa. Soil samples were taken in four replicates from geo-referenced locations on a regular grid of 30 m. Soils were analyzed for pH, and SMP buffer pH. Soil maps were produced with Geographic Information System （GIS） software, and soil pH datasets were interpolated using a geostatistical tool of inverse distance weighing （IDW）. Soil pH in the fields varied from 3.93 to 7.00. An excess amount of lime as high as 30 t/ha under uniform lime application were recorded. These recommendations were in excess on field areas that needed little or no lime applications. Again, there was an under applications of lime as much as 35 t/ha for uniform liming applications. This under- and over-recommendations of lime based on average soil pH values suggests that uniform soil acidity correction and soil pH management strategy is not an appropriate strategy to be adopted in these fields with spatially variable soils. The field can be divided into lime application zones of （1） high rates of lime, （2） low rates of lime and （3） areas that requires no lime at all so that lime rates are applied per zone. A key to site-specific soil acidity correction with lime is to reach ideal soil pH for the crop in all parts of the field.展开更多
A relative humidity series of April-August during 1825-2009 AD was reconstructed based on tree- ring width of Pinus sylvestris var. mongolica for the Hulunbuir area. During the past 185 years, 25 humid years and 26 ar...A relative humidity series of April-August during 1825-2009 AD was reconstructed based on tree- ring width of Pinus sylvestris var. mongolica for the Hulunbuir area. During the past 185 years, 25 humid years and 26 arid years were identified in the reconstruction, as well as 6 wet periods and 6 dry periods. The relative humidity has decreased since approximately the 1950s, suggesting a warm and dry climate trend in the study area. The reconstruction can be compared with those of the surrounding tree ring reconstructed precipitation and rela- tive humidity series at the decadal scale, reflecting the consistency of the regional climate variations. Besides, significant positive correlations are revealed between the reconstruction and the normalized difference vegetation index of the Hulunbuir grassland. And the decrease in relative humidity will cause negative impacts on the Hulunbuir grassland. Comparisons between the sandstorm records and the relative humidity of the study area indicate that strong sandstorms occurred more frequently in Hulunbuir when the relative humidity was low. Therefore, under the downward trend in relative humidity, more effort should be made to protect the grassland ecology and treat the bare sand land for the local and surrounding areas.展开更多
文摘Knowledge and management of soil pH, particularly soil acidity across spatially variable soils is important, although this is greatly ignored by farmers. The objective of the study was to evaluate in-field spatial variability of soil pH, and compare the efficiency of managing soil pH through site-specific method vs. uniform lime application. The study was conducted on three sites with study sites I and II （23°50＇ S; 29°40＇ E）, and study sites IIl （23°59＇ S; 28°52＇ E） adjacent to each other in the semi-arid regions of the Limpopo Province, South Africa. Soil samples were taken in four replicates from geo-referenced locations on a regular grid of 30 m. Soils were analyzed for pH, and SMP buffer pH. Soil maps were produced with Geographic Information System （GIS） software, and soil pH datasets were interpolated using a geostatistical tool of inverse distance weighing （IDW）. Soil pH in the fields varied from 3.93 to 7.00. An excess amount of lime as high as 30 t/ha under uniform lime application were recorded. These recommendations were in excess on field areas that needed little or no lime applications. Again, there was an under applications of lime as much as 35 t/ha for uniform liming applications. This under- and over-recommendations of lime based on average soil pH values suggests that uniform soil acidity correction and soil pH management strategy is not an appropriate strategy to be adopted in these fields with spatially variable soils. The field can be divided into lime application zones of （1） high rates of lime, （2） low rates of lime and （3） areas that requires no lime at all so that lime rates are applied per zone. A key to site-specific soil acidity correction with lime is to reach ideal soil pH for the crop in all parts of the field.
基金supported by the State Key Laboratory of Loess and Quaternary Geology(SKLLQG1316)the Scientific Research Plan Projects of Shaanxi Education Department(15JK1796)+1 种基金the Dominant Discipline Construction Projects of Shaanxi(Historical Geography 0602 SZXKY1302)the Specialized Research Fund Project of Xianyang Normal University(12XSYK0310)
文摘A relative humidity series of April-August during 1825-2009 AD was reconstructed based on tree- ring width of Pinus sylvestris var. mongolica for the Hulunbuir area. During the past 185 years, 25 humid years and 26 arid years were identified in the reconstruction, as well as 6 wet periods and 6 dry periods. The relative humidity has decreased since approximately the 1950s, suggesting a warm and dry climate trend in the study area. The reconstruction can be compared with those of the surrounding tree ring reconstructed precipitation and rela- tive humidity series at the decadal scale, reflecting the consistency of the regional climate variations. Besides, significant positive correlations are revealed between the reconstruction and the normalized difference vegetation index of the Hulunbuir grassland. And the decrease in relative humidity will cause negative impacts on the Hulunbuir grassland. Comparisons between the sandstorm records and the relative humidity of the study area indicate that strong sandstorms occurred more frequently in Hulunbuir when the relative humidity was low. Therefore, under the downward trend in relative humidity, more effort should be made to protect the grassland ecology and treat the bare sand land for the local and surrounding areas.
