Future research may establish soil tests for these elements. Sometimes fertiliser rates for individual paddocks can be recommended without the use of soil testing. If this information is unavailable, or if leaching or transport losses of phosphorus are large, soil testing can be used instead. With potassium, large amounts can move out of the soil through leaching or plant uptake. History is therefore of little use in predicting the amount of potassium remaining in the soil, and a soil test is the most effective way in assessing the potassium status.
Soil sampling Sampling often limits the success of a soil test.
As a consequence, extreme care is needed to ensure that samples are representative. Nutrient levels in the soil vary as a result of soil type differences and management. Most soils in WA are not uniform and many soil types can usually be found in one paddock. Where soil differences in a paddock are obvious and where these can be treated differently, it is advisable to sample each area separately. Even if the paddock has a uniform soil type, stock can spread soil nutrients unevenly through urine and dung.