Preliminary Lab Results Show Low Phosphorus Across Sentinel Sites

by | December 5, 2011
Category: Blog

Reference lab data from the AfSIS sentinel sites analyzed so far show an over-riding constraint of low available phosphorus (

The six kernel density plots below show the distribution of key soil fertility constraints at AfSIS sentinel sites. The vertical lines in each plot show critical limits from left to right of low and high in the case of soil pH, very low and low for bases, P, K, and Zn, and low for Cu.



In the figure below, the laser diffraction particle size analysis of dry and wet soils is providing indices of soil erodibility. Soils in the left half of the graph are coarse textured soils and by definition do not give fine particles in wet or dry state. The soils in the bottom right quadrant are fine textured soils but are well aggregated in their dry state and so are not susceptible to wind erosion.

On the other hand, soils in the top right quadrant are fine soils that contain a high proportion of fine particles in their dry state (i.e. poorly aggregated) and so can be expected to be highly susceptible to both wind and water erosion.

Soil aggregate stability index based on laser diffraction particle size analysis in dry and wet modes. The percentage of fine particles (i.e the silt plus clay fraction, <50 microns) in dry mode against the percentage of fine particles in fully dispersed wet mode.

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