Factors of Soil Aggregation Essay -- Agriculture Agricultural essays

Factors of Soil Aggregation There are many features that characterize a soil. One such feature is aggregates. There are many different types of aggregates, such as platy, prismatic, granule, blocky, angular, and more. There are several different factors which influence the formation of these aggregates. Hans Jenny, in his book Factors of Soil Formation (1941), recognizes five factors which influence soil formation: climate, biota, topography, parent material, and time. This paper will explore each of these factors in order to gain a better understanding as to what influences aggregate formation and strength. Before exploring aggregate formation and strength, the word "aggregate" must be clearly defined. Singer and Munns (1996) define aggregate as a word synonymous to "ped" which refers to "a group of primary particles held together by various soil-stabilizing agents" (pg. 28) and "are described according to their shape, size, stability, and east with which we can see them in the soil" (pg. 28). There are six main types of aggregate shape: granular, subangular blocky, angular blocky, prismatic, columnar, and platy (Singer and Munns, 1996). Aggregates of different shapes form under different conditions, however, the basic elements that cause aggregate formation remain the same. Now that "aggregate" has been defined, the discussion of formational factors may begin. The formation of aggregates begins at the smallest level, with tiny particles of less than five micrometers called colloids (Singer and Munns, 1996). At this size, electrostatic bonding and hydrogen bonding hold particles together (Black, 1968). This causes several effects. First, the amount of clay present becomes important, since most electrostatic and inter... ...arides that are effective binding compounds. Fungal hyphae on cast surfaces can physically enmesh and stabilize casts, but stabilization is most strongly promoted by drying, which brings the organic and mineral compounds into close association, promoting clay-polyvalent cation-organic matter linkages" (pg. 1743). The factors which influence soil formation, and consequently aggregates, are complexly linked. Each factor interacts, influences, and in turn is dependent upon each other factor. Through this amazingly intricate relationship, several factors are recognized as more influential in aggregate formation. To fully list all possible elements which work to form a single aggregate would take many years, and many volumes of books to complete. This paper has hopefully provided insight into several of the most important factors that influence aggregate formation.