Animal life of soils

A great diversity of animals, having few morphological features in common, exists in the soil and in the litter above it. Some of these are permanent soil inhabitants, whereas others are temporary. Some are burrowing forms but others live either under surface debris or in the soil openings made by natural agencies or by man. In size the individuals vary from the microscopic Protozoa and nematodes to mammals, such as moles, rabbits and woodchucks. There are literally thousands of kinds of animals involved and many thousands of species. For example, Peters (1955) states that there are about 10,000 species of nematodes alone, half of which are free-living. The proportion of these that is found in soil is not known with accuracy, but soil nematode species are abundant. About 1,800 species of earthworms are known, and the arthropod species (principally insects) that spend a part of their lives in soils are even more numerous (Kevan, 1962). 

The soil fauna play such an important role in humus formation that any reasonably complete discussion of soil organic matter and its effect on plant growth must deal with them. In the limited space available the author will refer briefly to the chief types of animals involved, mention some of the main factors that determine their abundance, and consider the role that they play in soil formation and crop production. 

The most important kinds of animals constituting the soil and litter fauna, according to Kevan (1962), are the Protozoa, nematodes, segmented worms and the great phylum of arthropods. 

INTERRELATIONSHIP BETWEEN VEGETATIVE COVER AND ANIMAL POPULATIONS 

Soil-inhabiting animals form communities that are fairly stable so long as the environmental conditions remain reasonably constant. This ecological balance between organisms that have few characteristics in common is not unlike the situation that exists in plant communities. Any marked change in the environment may, however, radically modify the animal community. Some kinds of animals may be eliminated entirely, or at least the ratio between individual kinds within the community may be changed markedly (Tischler, 1955). 

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CgH,3BrN202. A soil-acting herbicide. White crystalline solid, m.p. 158-159" C. It is a non-selective inhibitor of photosynthesis used for weed control In citrus and cane fruit plantations. It is relatively non-toxic to animal life. 

Plutonium (Pu) is an artificial element of atomic number 94 that has its main radioactive isotopes at 2 °Pu and Pu. The major sources of this element arise from the manufacture and detonation of nuclear weapons and from nuclear reactors. The fallout from detonations and discharges of nuclear waste are the major sources of plutonium contamination of the environment, where it is trapped in soils and plant or animal life. Since the contamination levels are generally very low, a sensitive technique is needed to estimate its concentration. However, not only the total amount can be estimated. Measurement of the isotope ratio provides information about its likely... 

Zinc, like most metals, is found in all natural waters and soils as well as the atmosphere and is an important trace element in plant and animal life (see Mineral nutrients). Rocks of various kinds contain 20—200 ppm zinc and normal soils 10—30 ppm (average ca 50 ppm) in uncontaminated areas. The average zinc content of coal is 33 ppm. Seawater contains 1—27 )-lg/L (median ca 8 p.g/L), and uncontaminated freshwater usually <10 / g/L. 

Moisture must be considered of primary importance in soil formation, in weathering, and in all of the changes taking place within the soil. The types of soil that form depend to a great extent upon the rainfall situation. Too little rainfall will prevent development of plant and animal life with their soil-building action. Too much moisture has a similar effect in preventing normal soil formation. 

The transfer of PBBs from soil to plants is so low, e.g., Table III and References (6,29), that the only important issue In the agricultural scenario appears to be soli ingestion (and possibly ingestion of groundwater) by cattle. Based on an estimated half-life, tj/2> in beef of 120 days (30) an estimated mass of fat per animal, M, of 67 kg and a soil Ingestion rate, Mg, of 0.72 kg/day (31), a reasonably conservative soll-to-fat bioconcentration factor can be obtained ... 

Keeper substances in a scent secretion, and/or the nature of the substrate such as rock, wood or soil, impart longevity to a scent mark. In our own studies, scent marks of captive pronghorn, A. americana, were still noticeable to the human nose 4 months after all animals had been removed from a pen. Similarly, scent marks of the aardwolf, Proteks cristatus, last for up to 6 months (Apps etal, 1989). 2-Phenoxyethanol in the secretions from the chin gland of the rabbit is typical in dominant animals, serving as a fixative to extend the life of the signal (Hayes etal, 2001). 

Calcium in Plant and Animal Nutrition. Calcium is essential to plant and animal life and is present in adequate amounts in many soils (78). The outer green leaves of cabbages and certain other leafy vegetables contain much more calicum than the inner white ones (79, 80, 81). Large amounts of it are present in the human body. The composition of bone suggests that it must be closely related to the apatite series of minerals, which have the formula nCa3(PO.t )2-CaC03, in which n has a value... 

The purpose of organic agriculture is to optimize the health and productivity of interdependent communities of soil life, plants, animals, and people. 

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