FIXED AMMONIUM IN SOME SASKATCHEWAN SOILS

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Abstract
Nitrogen, as fixed ammonium, occurred in the five profiles of arable soil of different texture which were examined. The amounts observed increased with increasing soil depth in four of the profiles. Total amounts found in the 4-ft profiles varied from 2600 to 4600 lb per acre and ranged from 7% of the total nitrogen in the surface soil to as much as 58% in the soil at the 4-ft depth.When the fixed ammonium nitrogen was subtracted from the total nitrogen the C:N ratios of these soils increased very sharply with depth, indicating that the subsoil organic matter was less rich in nitrogenous substances than was that of the surface soil.The clay fractions of the profiles were mineralogically similar and contained essentially the same amounts of fixed ammonium, approximately 2.4 meq ammonium per 100 g of clay. The silt fractions contained approximately 1.8 meq fixed ammonium per 100 g of silt. These fractions accounted for nearly all the fixed ammonium nitrogen observed except in the coarser-textured soils.Fixed ammonium and total nitrogen analysis of 25 paired samples of cultivated and virgin soil indicated that although the average total nitrogen had been reduced by one-third, there had been little or no effect on the amount of fixed ammonium N in the surface soil.

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