QUANTITATIVE RELATIONSHIP BETWEEN NET NITROGEN MINERALIZATION AND MOISTURE CONTENT OF SOILS

Publisher Website
Google Scholar
Abstract
The 0- to 15- and 15- to 30- cm depths of 5 cultivated Queensland [Australia] soils and 32 virgin and cultivated western Canadian soils were incubated at a range of moisture contents for 14 days at 35.degree. C. In most soils, net N mineralization was linearly related to moisture content in the available range (-0.03 to -4.0 MPa). Optimum moisture for net N mineralization corresponded to a soil pore water potential of between -0.01 and -0.03 MPa, while that at which no net N mineralization occurred was close to -4.0 MPa. Initially, the regression for each soil was normalized by the method of Stanford and co-workers, but this technique proved unsatisfactory. However, by normalizing against available moisture (between -0.03 and -4.0 MPa) succeeded in grouping the soils. The response of all soils could be described by a model of the form: y = bx + (1 - b)x2 constrained to pass through xo, yo and x1, y1, when both axes were scaled between 0 and 1. In the equation, y is net N mineralized expressed as a proportion of the maximum rate; x is normalized moisture content; and the subscripts max and 0 refer to soil pore water potentials of -0.03 and -4.0 MPa, respectively. Almost all data conformed to this model. Most soils had a linear response (i.e., b = 1.0), but 9 Canadian and 1 Queensland soil showed a curvilinear response. The expression worked well for the 9 Canadian soils and b was estimated statistically to range between 1.22 and 2.18.