Date of Award:


Document Type:


Degree Name:

Master of Science (MS)


Plants, Soils, and Climate


H. B. Peterson


The practice of applying fertilizers to the soil by adding the liquid form to the irrigation water is increasing in popularity. There are several advantages maintained for such a method of application. Some of the advantages are:

(A) Ease of application

(B) No special equipment is required for application.

(C) The fertilizer can be applied at any stage of plant growth without physical disturbance of the plant.

(D) Penetration into the root zone may be greater than the dry fertilizers.

Considerable phosphate fertilizer is used on soils of irrigated regions. If the behavior of liquid phosphoric acid after its incorporation with soil is such that it penetrates into the root zone and is otherwise as efficient as dry phosphate fertilizers in inducing favorable plant response, then it would seem practical to utilize the other advantages offered by applying the fertilizer in irrigation water.

Commercial phosphoric acid (52% available P2O5) is produced by applying an excess of sulfuric acid to ground rock phosphate. This phosphoric acid is usually applied to an additional amount of phosphate rock to make concentrated superphosphate. A given quantity of phosphoric acid can yield more available phosphorus by applying it to rock phosphate than by using it directly as a fertilizer.

Because of its potential value in producing concentrated superphosphate commercial phosphoric acid has been used very little as a fertilizer. There is insufficient research in which the comparative value of the acid as a fertilizer has been investigated the purpose of the studies reported in this paper are, to compare: (A) the value of commercial phosphoric acid and concentrated superphosphate as fertilizers when applied in equivalent amounts and, (B) the different methods of application and dilution of the phosphoric acid.