Soil variability and geostatistical applications

Statistical and geostatistical methods are utilized to investigate soil variability. Methodology includes block kriging, cokriging and simulations of random fields. The ramifications of the variability are numerous, including the effect on soil water, soil fertility, evapotranspiration, and crop yields. Block kriging can be used to estimate crop yields and infiltration rates on a large scale using small scale or point data. Results based on variograms and geostatistics are compared to the classical relationship developed by Smith in 1938, that the variance is reduced from V₁ to V₁/nᵇ as the support area increases from 1 to n plots. These results establish a firm theoretical basis for the variance within a finite domain as a function of sample support size. Applications include not only uniformity trials, but also measurement theory. Based on 20 data sets, indices of soil heterogeneity are derived. With these indices, optimal sample sizes and shapes can be determined. The ordinary kriging and cokriging estimators are investigated in order to examine their utilization. Soil moisture content and soil water retained at 1.5 MPa within the root zone are predicted by cokriging with surface moisture and texture as auxiliary variables. Compared with ordinary kriging, cokriging gave a significant improvement in terms of the average kriging variance and the sum of squared errors between the actual and the predicted values. With soil spectral properties and cokriging, soil texture is estimated successfully. Cokriging is also used for temporal variables and compared with a time invariant relationship. Recently-developed pseudo-cross variograms and cokriging are utilized to predict soil chemicals. The main advantage of this approach is that the computation of sample cross-variograms does not require that measured variables be sited at the same locations. Lastly, several simulation methods are studied. A new simulation procedure is developed and compared with other simulation methods, such as the Turning Bands Method. Conditional simulation is used to simulate random fields for soil water and reflectance

Phosphorus metabolic disorder of Guizhou semi-fine wool sheep.

Guizhou semi-fine wool sheep are affected by a disease, characterized by emaciation, lameness, stiffness in the gait, enlargement of the costochondral junctions, and abnormal curvature in the long bones. The objective of this study was to determine possible relationships between the disease and mineral deficiencies. Samples of tissue and blood were collected from affected and unaffected sheep. Samples of soil and forage were collected from affected and unaffected areas. The samples were used for biochemical analyses and mineral nutrient measurements. Results showed that phosphorus (P) concentrations in forage samples from affected areas were significantly lower than those from unaffected areas (P < 0.01) and the mean ratio of calcium (Ca) to P in the affected forage was 12:1. Meanwhile, P concentrations of blood, bone, tooth, and wool from the affected sheep were also significantly lower than those from the unaffected group (P < 0.01). Serum P levels of the affected animals were much lower than those of the unaffected ones, whereas serum alkaline phosphatase levels from the affected were significantly higher than those from the unaffected (P < 0.01). Inorganic P levels of the affected sheep were about half of those in the control group. Oral administration of disodium hydrogen phosphate prevented and cured the disease. The study clearly demonstrated that the disease of Guizhou semi-fine wool sheep was mainly caused by the P deficiency in forage, as a result of fenced pasture and animal habitat fragmentation

Mineral element concentrations (ppm) in soil and forage samples collected in the affected and unaffected areas.

a<p>Results between the affected and unaffected areas were significantly different (<i>P</i><0.01).</p

Labile carbon input and temperature effects on soil organic matter turnover in subtropical forests

The objective of this study was to assess the effects of labile organic carbon (LOC) input on the dynamic turnover of soil organic matter (SOM) with temperature in subtropical forests. Soil samples were collected from three subtropical forests: an evergreen broadleaf forest, a mixed pine and broadleaf forest, and a pine forest. To simulate LOC inputs, soil samples were supplemented with 13C-glucose at levels of 0, 0.2, 0.6, and 1.2 mg C g−1 soil. The soils with the LOC treatments were incubated for six weeks at temperatures of 15, 25, and 35 °C. Results showed that the increase in LOC inputs reduced the priming effects of SOM decomposition significantly, whereas native SOM mineralization increased with temperature. The preferential utilization of LOC by microorganisms reduced SOM decomposition, resulting in net SOC increases with LOC inputs. In the temperature range, the net increases in SOC with the LOC inputs were −0.19 to 0.56 mg C g−1 soil. Moreover, the LOC inputs aided microbial anabolism and promoted the formation of new mineral-associated organic matter and the aggregation of particulate organic matter, resulting in carbon sequestration. Among the forest soils, the soil with the highest organic carbon content, total nitrogen, and carbon to nitrogen ratio (i.e., the mixed forest soil) had the lowest priming effects and was the most conducive to net carbon increase. The priming and carbon sequestration caused by the LOC inputs were not sensitive to temperature changes. Our findings suggest that the increase in the supply of LOC has the potential to alleviate SOM decomposition and increase carbon storage in subtropical forest soils

Mineral element concentrations in bones and teeth of Guizhou semi-fine wool sheep (The unit for Ca and P is in g/kg dry sample and others in ppm).

a<p>Results between affected and unaffected the Guizhou semi-fine wool sheep were significantly different (<i>P</i><0.01).</p

Serum protein concentrations (g/l) of Guizhou semi-fine wool sheep.

a<p>A =  albumin;G =  globulin.</p>b<p>Results between the affected and unaffected Guizhou semi-fine wool sheep were significantly different (<i>P</i><0.01).</p