Fertility assessment is best carried out at a soil and plant testing laboratory. However, certain quick field tests exist for soil nitrates and SOM which can be used as surrogates of soil fertility in a comparative manner. Knowing the texture and the soil pH, the depth to lime, and the topography, the previous crop and yield, can assist in the interpretation of the nitrate and SOM levels. Soil can be taken from the top foot or two feet, and the nitrate and organic matter estimated for those depths. Knowing that about 2 lb of N is required per bushel of wheat, one can estimate the N fertilizer needs based on N in the soil profile and organic matter N contribution.
Crops differ in their tolerance to salts.
While beans are sensitive, wheat is more tolerant. If the water table is not near the surface, salts can be leached, and appropriate crops can be grown. Quick field tests with electrical conductivity probes exist for salt evaluation. Where manure is rarely used and the parent material is not overlain by shales, salinity does not present a problem. Thus, stable aggregates are less erosive, and create less crusting and greater water infiltration.