Another way to collect a stool sample is to loosely place plastic wrap across the rim of the toilet, under the seat. Then place the stool sample in a clean, sealable container before taking to the laboratory. Plastic wrap can also be used to line the diaper of an infant or toddler who is not yet using the toilet. The stool should be collected into clean, dry plastic jars with screw-cap lids.
The potential variations in the properties of agricul-. tural soils are less well known. Diaz et al. (1994) have. reported that under a climate change scenario the soil. organic matter content and erosion rate would de-. crease with regard to current values in the Arrecifes. River basin.
environments, soil pH decreases over time in a process called soil acidification, due to leaching from high amounts of In dry climates, rainfall. however, soil weathering and leaching are less intense and pH can be neutral or alkaline. Soils with high clay and organic matter content are more able to resist a drop or rise in pH have a (greater buffering capacity) than sandy soils. Although clay content cannot be modified, organic matter content can be changed by management. Sandy soils commonly have low organic matter content, resulting in alow buffering capacity , high rates of water percolation and infiltration making them more vulnerable to acidification . Soil pH Management Soil pH is affected by land use and management. Vegetation type impacts soil pH. For example, areas of land foresttend to be more acidic than. areas of Conversion of land from grassland. forestland or grassland to cropland can result in. drastic pH changes after a few years.