The significance of intercalary ammonium in representative surface and subsoils from southern New South Wales

Abstract

Six surface and subsoils known to contain native intercalary ammonium were examined to assess the importance of ammonium fixation when nitrogen fertilizers were applied, the availability of native and recently fixed intercalary ammonium to plants, and the effect of potassium on fixation. Only one soil, a grey soil of heavy texture (Ug 5.4), fixed significant amounts of added ammonium sulphate, the level of intercalary ammonium being increased by 55 % in the surface and 100% in the subsoil. The native level of intercalary ammonium was reduced by 8 and 17% by the growth of plants in the red-brown earth (Dr 2.23) and the grey soil of heavy texture, respectively, but was unchanged in the other soils. The addition of small amounts of potassium prior to the ammonium did not affect fixation; however, additions of 500 ppm reduced the fixation of a 200 ppm solution of ammonium by 80 %. Intercalary ammonium is not considered to be important in the nitrogen economy of five of the six major farming soils of the slopes and plains area of southern New South Wales. The sixth, the grey soil of heavy texture, is an alluvium associated with the Murrumbidgee River and its tributaries, and as such is used extensively for irrigated agriculture. Because this soil can fix large amounts of ammonium, the use of ammonium or ammonium forming fertilizers is not recommended.

Measurement and simulation of soluble, exchangeable, and non-exchangeable ammonium in three soils

“…Fixation is fast and occurs within the first few hours after fertiliser application (e.g., Kowalenko, 1978;Sowden, 1976). On the other hand, its release, which normally concerns only a fraction of the fixed ammonium, is slower and longer-lasting, taking up to several weeks (Osborne, 1976a;Smith et al, 1994;Steffens and Sparks, 1997).…”

Fixation and defixation of ammonium in soils: a review

“…Figure 1 shows Legg and Allison (1959) and Black and Waring (1972) found that this N fraction plays a minor role for the N nutrition of plants, Norman and Gilmour (1987) estimated that the amounts of fertilizer-derived NH 4 + f -N available to ryegrass ranged from 35% to 72%. As percentage of total NH 4 + f -N, the release of this fraction ranged from 4% to 25% in different soils (Osborne 1976b;Smith et al 1994;Steffens and Sparks 1997). According to Smith et al (1994) were released during a growing season of annual crops (oats and winter wheat; Van Praag et al 1980).…”

“…However, in dry soils, the interlayer space is reduced and NH 4 + fixation also increases. According to Osborne (1976b), NH 4 + fixation was reduced by 25% in a clay soil moistened to 60% of the maximum water holding capacity as compared with the dry soil. Also, Gouveia and Eudoxie (2007) found a lower NH 4 + fixation in wet soils.…”

Advances in Soil Science

“…Scherer (1980) reported that soils of basaltic origin with smectite as the dominant clay mineral, although not low in nonexchangeable NH4 +, released only minute amounts of interlayer NH4 +. Osborne (1976) also reported that the release of non-exchangeable NH4 + depended largely on the mineral, with illite and vermiculite being the most important for NH4 + release.…”

“…The so bound NH/ is called "fixed NH4 +''' although this term is not correct since it suggests a non-available N fraction that, as has been shown by recent experiments, is not the case. It is more appropriate to term this fraction "non-exchangeable NH/" or "intercalary NH4 +" (Osborne, 1976). This NH4 + fraction is not exchangeable by K+.…”