Sampling - Field Sampling: Principles and Practices in Environmental Analysis - page 130

FIGURE 5.11 An example of a hay field to which additions would be made
uniformly.
animals congregate, such as around watering tanks or gates, will usually have high
amounts of manure, and thus is not representative of the field as a whole. Also, when a
sampling site is chosen it should not be covered by or be very near a pile of manure, as
this will again constitute an area with unusual characteristics. Even if the manure is
scraped off the top of the sample, organic matter and chemicals will have leached out of
the manure and into the soil. The amount leached will depend on how long the manure
has been in place and how much rain has fallen in the meantime. Both of these are
unknowns and cannot be corrected for. A pasture field with animals grazing is shown in
Figure 5.12.
The largest amounts of chemicals added to the environment each year are agricultural
chemicals. In this group, lime (CaCO 3 ), which is usually spread evenly on the surface of
fields, is used in the highest quantity in areas with acid soils. In all areas, nitrogen
fertilizer is used in the greatest amount (second to lime on acid soils). Nitrogen is both
uniformly spread on the surface of soil and as a band near the seed in row crops. There
are also large amounts of pesticides—primarily insecticides and herbicides—used, while
lesser amounts of fungicides and other agents to control nematodes, mites,