Cotton root growth as affected by P fertilizer placement

Abstract

Growth chamber studies were conducted to evaluate root growth and P uptake by cotton (Gossypium hirsutum L.) as affected by the proportion of the soil volume that is treated with fertilizer P. Cotton seedlings were grown in a Dewey silty clay loam (Typic Paleudult) and a Marvyn loamy sand (Typic Paleudult). The Dewey soil had a low-P status and the Marvyn soil had a high-P status (7 and 44 mg kg⁻¹ Mehlich I extractable P, respectively). Phosphorus was added at a constant or base rate which was added to decreasing proportions of the soil volume (i.e. 1.0, 0.5, 0.25 and 0.125). The addition of the same amount of P to decreasing proportions of the soil volume resulted in a stimulation of root growth in the P-fertilized soil volume relative to the nonfertilized soil. The degree of stimulation was similar for the two soils which differed in P status. Phosphorus uptake reached a maximum when 0.25 and 0.50 of the soil volume was treated with P on the Marvyn and Dewey soils, respectively.