A SINGLE MEASUREMENT TO PREDICT POTENTIAL MINERALIZABLE NITROGEN

• Published in: Communications in soil science and plant analysis 2002-11, Vol.33 (15-18), p.3517-3530
• Main Authors: Zhang, Mingchu, Karamanos, R. E., Kryzanowski, L. M., Cannon, K. R., Goddard, T. W.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Chemical, physicochemical, biochemical and biological properties; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Nitrogen fertilization; Nitrogen, phosphorus, potassium fertilizations; Organic matter; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Soil science; Soil-plant relationships. Soil fertility. Fertilization. Amendments
• ISSN: 0010-3624; 1532-2416
• DOI: 10.1081/CSS-120014545

Since the early 1970's, soil nitrate nitrogen (NO 3 -N) levels have been used as a basis for N fertilizer recommendations in western Canada. However, soil nitrate N does not represent the supplying power of soil N for plant uptake. Furthermore, the nitrate concentration in soil changes depending on the time and ambient conditions at sampling. Researchers in the past have used mineralization potential to predict N supply power for plant growth. There are two methods to estimate the potential mineralizable N: a laboratory incubation and a chemical extraction method. The laboratory incubation method requires a long time to obtain a measurement. By comparison the chemical extraction method (e.g., hot KCl extraction) provides a quick estimation of potential mineralizable N, but the method requires calibration with laboratory incubation results. Alberta Agriculture, Food and Rural Development has established benchmark sites to monitor soil property changes from agricultural practices. Hot KCl extractable N and soil organic matter were determined each year in these sites. Using the results from the benchmark sites, an approach was developed to estimate mineralizable nitrogen (Nt) from soil organic matter based on an equation of Nt=No(1−e −kt )y, and validated the calculated Nt with hot KCl extractable N. Our results indicated that the potential mineralizable N released from soil differed among different ecoregions and slope positions. Potential mineralizable N is lower in southern Alberta as compared to central Alberta. The lower slopes released more N than higher slope positions. The results also showed that Nt released in soil over the growing season correlated with hot KCl extractable N quite well in three different slope positions. However, variability of Nt in upper slopes is greater than that in middle and lower slopes due to a shallow A horizon and variable soil moisture during the growing season. After removal of outliers (9% of the total data set), the values of R 2 (regression of hot KCl N with calculated Nt) are 0.529, 0.576 and 0.627 for upper, middle and lower slope position, respectively. Based on the calculated results, a potential mineralizable N map in Alberta can be developed, which will guide producers to manage soil as well as fertilizer N.