Nitrogen Mineralization Characteristics Research Articles

Nitrogen mineralization in forest soil profiles from central Alberta

The nitrogen mineralization characteristics of soils from stands dominated by jack pine (Pinusbanksiana Lamb.) and white spruce (Piceaglauca (Moench) Voss) were examined using a 37-week incubation with periodic leaching to allow measurement of mineralized N. Soils were compared on the basis of total N, N mineralized during the incubation, potentially mineralizable N, mineralization rate constant, and nitrification potential. Nitrogen characteristics of LFH horizons primarily reflected the age and species composition of the existing vegetation while those of A horizons appeared to relate to conditions in previous as well as present stands. Characteristics of B horizons were independent of vegetation implying control by long-term accumulation and transformation of N within the soil. The N fertility of a forest site therefore represents the integration of processes acting within different time frames and an understanding of the relative contributions of short- and long-term processes in the control of N availability is required for efficient fertility management.

Organic Carbon and Nitrogen Changes in Soil Under Selected Cropping Systems

AbstractThe use of different cropping systems is one means of conserving soil organic matter. This study was conducted to evaluate the effect of 9 yr of selected cropping systems on organic C (WBC), N levels (TKN), and N mineralization characteristics (BMN) of a Charity clay (Aeric Haplaquepts). The six cropping systems consisted of combinations of corn (Zea mays L.), oats (Avena sativa L.), alfalfa (Medicago sativa L.), sugarbeets (Beta vulgaris L.), and navy beans (Phaseolus vulgaris L.). Each crop in each system was fertilized at recommended rates. Cropping systems that contained corn had up to 10% more WBC and 7% more TKN at the time of sampling than systems that did not contain corn. Nitrogen mineralization characteristics correlated linearly with WBC and TKN using S81 soil samples but not with WBC, TKN, or N uptake in a greenhouse study using F81 soil samples. The uptake and response to applied N in the greenhouse indicated that 9 yr of cropping with a particular system had an effect on the N supplying capacity of the soil. Reduced uptake and larger responses to applied N were observed for systems that did not contain corn and that lost larger amounts of C and N over the 9‐yr cropping period.