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The Influence of Certain Soil Treatments upon the Fixation and Availability of Applied Phosphates
Author(s) -
Copeland O. L.,
Merkle F. G.
Publication year - 1942
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1942.036159950006000c0057x
Subject(s) - citation , library science , computer science , operations research , mathematics , agricultural economics , law , political science , economics
T N the general process of evolution plants have *• developed which require, on the average, approximately one-fourth to two-thirds as much phosphoric acid as of either nitrogen or potash. Under natural conditions plants must have been able to obtain the amounts needed. Under cultivation, however, the constant mixing of all the organic products with the inorganic colloidal matter has caused fixation and consequent deficiency of phosphates to be more universal than that of nitrogen or potash. The reason for this is because the phosphate ion is more rapidly and completely fixed by the inorganic soil colloids than is nitrogen or potassium. The degree to which applied phosphates are fixed by soils is well known as a result of laboratory and field studies. It may be shown that in many cases not over one-tenth to one-half the phosphate applied in fertilizer is ever obtained by the crop. Furthermore, it appears that when phosphates are fixed by soils they are not easily removed thereafter, otherwise those fertility plots which have been fertilized with phosphates for long periods would gradually develop a sufficient reserve so that further applications would be unnecessary. This is not the case. On mineral soils which have been phosphated for many years it is observed that yields drop within a year or two after phosphating is stopped even though there must be a great reserve of fixed phosphate in the soil. Phosphates, even the less soluble and available ones as well as the more available ones, nearly always give profitable results, but if fixation could be reduced in some degree, greater profit would be obtained, and a valuable natural resource would be conserved. Numerous laboratory investigations have shown how great is the capacity of soils to fix soluble phosphates. It has been reported by different workers that from 80 to 99% of the soluble phosphate applied is fixed. Some have determined what soil constituents are responsible for phosphate fixation and what may be the effect of different treatments of soil colloids upon fixation. The purpose of this investigation was to determine what effect normal field treatments of fertilizers, manure, and lime over a period of years may have upon the power of soils to fix applied soluble phosphates. This was done by determining the fixing power of the Jordan field plots and the New Phosphate plots at the Pennsylvania State Experiment Station for applied phosphates and as a check upon these determinations the phosphate content of the crops produced was obtained.