Virtual soil testing – what is it?
Currently only ten percent of the total arable land in western Canada is soil tested at best. The percentage of farmers that soil test on a yearly basis is even lower. Providing recommendations to the farming community for the non-tested land presents both a challenge and an opportunity. Virtual soil testing started as an idea to essentially utilize information collected from soil tested fields and provide more qualified recommendations for those fields that were not tested. Virtual soil testing (or VST®) is in essence a modeling technique that reverses the soil testing process, i.e., utilizes crop production characteristics in association with chemical tests to predict soil nutrient levels for a subsequent crop (Karamanos and Cannon 2002). It is based on the Fertility Analysis and Recommendations Management (F.A.R.M.) model (Kruger et al. 1994) that was developed by Henry (1990; 1991) and was subsequently adapted to Saskatchewan, Manitoba and Alberta conditions by Karamanos and Henry (1991) and Karamanos et al. (1992a,b), respectively. F.A.R.M. essentially recognizes three sources of nitrogen contributing to plant N uptake, namely, soil available as determined by soil testing, net mineralizable and fertilizer nitrogen. Target yields are based on moisture use efficiency crop production equations (Karamanos and Henry, 1991) and are estimated for 75, 50 and 25 percent probability of precipitation in a given Soil Climatic Zone (Meyers and Karamanos, 1997). Recommendations for the rest of nutrients are simply based on “available” nutrient ranges and are in table format. This system of recommendations was introduced in the Province of Saskatchewan in 1991 and is currently used by Enviro-Test Laboratories in all three Prairie Provinces. Development of the VST process required modifications in the F.A.R.M. model, especially in relation to the soil mineralization component. These modifications are discussed by Karamanos and Cannon (2002).
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