Agriculture Reference
In-Depth Information
While not all plants affect soils this way, organic matter may vary systematically at
the scale of single perennial plants to produce surrounding islands of enhanced fertility
with organic matter concentrations declining with increasing distance from the plant
(see, for example, Figure I.47, Jackson and Caldwell, 1993). At a larger scale, Figure I.48
presents a contour plot of the distribution of carbon in the A horizon (0-5 cm) of a soil
(inceptisol) derived from basaltic parent materials in semi-arid (535 mm annual average
rainfall) tropical northeastern Australia (McIvor
et al.,
1991). The site (
ca
. 40 ha) supports
a savanna vegetation, is nearly level and was chosen for its apparent uniformity.
The contours were generated from samples taken at the intersections of a square
40m grid.
