Studies on Steam Sterilization of Soils: I. Some Effects on Physical, Chemical, and Biological Properties

Abstract

Effects of steam sterilization and recontamination with original soil, on certain physical, chemical, and biological properties of four Alberta soils were investigated. The soils were Edmonton black loam, Vegreville black fine sandy loam, Gros Ventre brown loam, and Fallis gray silt loam. Certain physical properties were affected by steam sterilization as follows: (1) capillary rise of moisture was greatly retarded in all four soils following sterilization; (2) the percentages of the different separates as determined by ordinary mechanical analysis were not changed significantly by sterilization; (3) water-holding capacity and moisture content at the 'sticky point' were slightly reduced, and, in three of the soils, shrinkage was slightly increased by sterilization, but these effects were of uncertain significance; (4) the pH values of these soils were not changed appreciably by sterilization. The following chemical changes were produced by steam sterilization: (1) water-soluble phosphate was generally greatly increased and water soluble sulphate somewhat increased by sterilization. Easily soluble phosphorus (soluble at pH 3) was increased by about one-third in the two black soils rich in organic matter, but not in the other soils; (2) ammonia accumulated rapidly in the sterilized recontaminated black and brown soils for four to six weeks, and then returned to normal in 8 to 12 weeks. Ammonia accumulated less rapidly and to a smaller degree in the gray soil; (3) nitrification was suppressed for about 6 to 10 weeks in the sterilized recontaminated soils, but was later more active in these soils than in the unsterilized (especially in the black soils rich in organic matter).

The influence of soil steaming on some properties of the soil and on the growth and heading of winter glasshouse lettuce. I. Changes in chemical and physical properties.

“…The changes in the pH due to steaming were only small. This is in agreement with earlier observations (Millikan, 1942;Malowany and Newton, 1947;Walker and Thompson, 1949;Davies and Owen, 1953). The pH values measured in leached soil are about 0.1-0.2 units higher than in the corresponding unleached soil.…”

“…The mineral nitrogen, accumulating in this period, especially during the first weeks, was exclusively ammo nium-nitrogen. This is a well-known fact in steamed and partially sterilized soil (Rich ter, 1896; Koch and Liiken, 1907;Pickering, 1908a, b;Russell and Hutchinson, 1909;Russell and Petherbridge, 1912;Potter and Snyder, 1918;Baldwin, 1922;Herzog, 1939;Van Koot, 1942;Malowany and Newton, 1947;Simpson and Newton, 1949;Davies andOwen, 1951, 1954;Roll-Hansen, 1952;Lapensee, 1959;Str0mme, 1962;Davidson and Thiegs, 1966;Simone-Sylvestre, 1967). The formation of nitrate was retarded during the first weeks; 56 days after steaming the largest part of the in organic nitrogen was still NH4-N and even after 79 days the amounts of NH4-N and NO3-N were about equal (Table 1).…”

“…Other elements are also found to become more soluble due to steaming: boron (Naftel, 1938;Roll-Hansen, 1952), calcium (Russell and Petherbridge, 1912;Kelley and McGeorge, 1915; no change in calcium is reported by Simone-Sylvestre, 1967), silicon (Kelley and McGeorge, 1913), sodium (Lapensee, 1959), sulphur (Lapensee, 1959), sul phate (Malowany and Newton, 1947;Simone-Sylvestre, 1967) and copper (Roll-Hansen, 1952).…”

“…A similar effect, depending on possibly changed con centrations of cations forming insoluble phosphate compounds could be presumed for steaming. However, in most cases increased amounts of soluble phosphates are re ported in the literature: Lyon and Bizzel (1910), Kelley and McGeorge (1915), Van Koot (1942), Malowany and Newton (1947), Roll-Hansen (1952), Lapensee (1959) and Simone-Sylvestre (1967). Baldwin (1922), using soils from various greenhouses, often found increases in acid-soluble phosphates, but sometimes the reverse effect was noticed.…”

“…The waterholding capacity of the soil may be reduced after steaming (Pickering, 1908a). But according to Malowany and Newton (1947) this reduction is small or even absent. Herzog (1939) observed a reduction of the water-holding capacity after steaming of alcaline soils ; in other soils sometimes an increase was observed.…”