The available phosphorus and potassium contents of surface soils and subsoils as shown by the Neubauer method and by chemical tests
1935
Thornton, S.F.
Comparative data for surface soils and subsoils are given for 460 soils with the Neubauer method and 400 soils with chemical tests. With the Neubauer method, subsoils as compared to surface soils show a much lower available phosphorus content. For soils from the Middle West, subsoils are phosphorus deficient in almost all cases. Neubauer values for available potassium are only slightly lower with subsoils than with corresponding surface soils. With chemical tests subsoils appear to be relatively only slightly lower in available phosphorus and slightly lower in available potash. With the Neubauer method there appears to be little correlation between pH and available phosphorus add potassium content. With chemical tests the phosphorus values increase with increasing pH and the potassium values show somewhat the reverse tendency, The data presented indicate that for subsoils of the humid regions at least, phosphorus deficiency is an important factor in the unproductivity so often observed.
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