Dear all,
I want to valuate the soil/mineral retention. As I have used RUSLE model in the GIS environment to find out soil erosion with C (cover ) factor and without C factor. I have the maximum and mean values for the soil erosion in tons per hectare per year for my study area.
I want to know
1. How to valuate the retention potential
2. Assign the economic value to the maximum or mean erosion rate?
3. How I can calculate the nutrients (N, P, K) amount/quantity from the erosion value?
Best regards,
The ability of soil to retain water in its profile is one of the most important soil functions. It is expressed as the
water storage capacity or retention capacity of the soil, and it is primarily affected by the physical properties of
the soil. Given the fact that the direct measurement of hydrological data for the soil is very difficult in terms
of capacity, statistically expressed pedotransfer functions (PTF) are currently used for the indirect estimation
of hydrolimits. The data most commonly used for the PTF are easy-to-measure and usually readily available
soil data on particle size, bulk density, organic carbon and morphometric parameters of the environment (e.g.
slope of the relief, etc.). The listed pedotransfer functions are deficient for the complex evaluation of soil cover;
given disagreements about the attributes, they cannot be directly used for the vector database of classified
soil-ecological units in the Slovak Republic. Therefore, we have created a model of an algorithm from selected
parameters compatible with the vector database of classified soil-ecological units, which also allows for the
spatial distribution of the cumulative coefficient of water retention capacity (CWRC) for the soils of the SR.
Using the RUSLE, there are a few factors that can modify soil loss, mainly C cover and P practices such as BMPs for instance. C can be modified by improving soil cover by type of vegetation and land management. An example of P might be to adjust full site soil cultivation to less intensive such as a light disking or no till methods. Adding mulch and suitable rapid responding vegetation cover or hydromulching are practices that are directed at quickly improving soil cover on expose sites. Most land managers are not going to consider reshaping the land to affect slope S or slope length L, but addition of and maintaining agricultural terraces may not necessarily reduce slope length to incipient erosion, but it can reduce rill and gully development from concentrated flow and delivery of sediment. It is hard to modify soil K or rainfall/runoff factor R in any way, but understanding their relative erosion potential relative to your site may be helpful in evaluating which activities are most appropriate. In construction activities there are many ways to mitigate soil exposure and reduce soil loss and erosion and there are various organizations such as the International Erosion Control Association that provide information and suitable training options for those interested.
In researchgate, I believe I uploaded an economic analysis of some years ago (1980s) evaluating whether to treat or not treat a gully system. It is probably not applicable to your specifics and their may be better methods, but it does give you an idea of what may be considered in evaluating costs and benefits over an extended time period consistent with forest management of gullied land versus rehabilitating to forested land, benefits for wood production, wildlife habitat, preventing erosion and reducing effects of sediment downstream.
If you have NPK values for surface soils that would be most susceptable to soil loss, you can multiply the estimated loss rates by the nutrient levels to get an estimate. More assumptions may be needed to estimate if the losses will affect site productivity or the potential for instream or water body effects from adding nutrients through erosion.
William F.Hansen thank you for your response. The most difficult part is the topographic factor (LS). Different researchers used different methods/equations. Still there is not any one standard method to calculate the slope length and slope steepness factor for water erosion. I am actually interested in to check whether there is any impact of vegetation cover on the soil erosion per hectare per year in the study area or not. Secondly I want to know value of soil erosion retention due to vegetation cover.
Vegetation cover as well as soil organics composed of litter, duff and humus in the surface or A horizon help to reduce erosion. Surface irregularities can also capture and retain erosion. The C factor should help with this. Soil types have an inherent K if cultivated, but their natural K of undisturbed soil surface would be different. I think this paper provides a much better response that anything I might say.
As first mentioned, if the intent is a desire for more precision, reliability, perhaps models like Water Erosion Prediction Project (WEPP) may be better suited if you want to deal with the intensity of site specific information and measurements that may be needed.
A reverse way to look at problem of retention, is to search on erosion control studies such as those that after soils have been disturbed and exposed in construction, etc. use vegetation, mulch, hydromulch, etc. It has generally been shown that these, when applied correctly, do a good to very good job at limiting erosion. I dont have on hand, but there were a number of studies that added various levels of straw mulch in tons/acre and measured effectiveness.
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