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Effect of fertilization on the composition of a Lufkin fine sandy loam and of oats grown on it

Fraps, G.S., Fudge, J.F., Reynolds, E.B.
Agronomy journal 1937 v.29 no.12 pp. 990-996
Avena sativa, sandy loam soils, NPK fertilizers, Gossypium hirsutum, Zea mays
A study was made of the effect of fertilizers added during a period of 8 years in varying quantities up to a maximum of 800 pounds of an 8-12-8 fertilizer per acre, on the quantities of nitrogen, active phosphoric acid, active potash, and acidity in Lufkin fine sandy loam soil, and of the relation of these to the composition of oats grown on the soil at College Station, Texas. Of the total amount of nitrogen added, 50 tO 70% was found in the surface 6 inches of soil; only a small amount had penetrated into the subsoil. From 36 tO 48% of the phosphoric acid added was found as active phosphoric acid in the surface 6 inches of soil. The phosphoric acid penetrated to a considerable depth as shown by the fact that the subsoil of the plats that received phosphoric acid contained about 2 1/2 times as much active phosphoric acid as the plats which received no phosphoric acid. Practically all of the increases in active potash were caused by increases in exchangeable potash. Potash also penetrated the subsoil, but to a lesser extent than phosphoric acid. Additions of phosphoric acid and potash had little, if any, effect on soil acidity, but nitrogen added as sulfate of ammonia increased acidity; manure decreased it. The phosphoric acid and nitrogen contents of the oats were fairly well related to the quantity of these constituents in the soil while the oats were in a vegetative stage of growth, but the relation was not close in oats cut near maturity. The relation with respect to potash was irregular at both stages of growth.