Cotton Root Development in Relation to Natural Aeration of some Mississippi Blackbelt and Delta Soils 1

HE agriculture of the Missippi-Alabama blackbelt soils consists T mainly of cotton and Johnson grass meadows for hay. Originally, this was a natural prairie section. Because of its high content of clay, the soil is difficult to handle and the crop yields are often poor; nevertheless, with proper management the yields are good. The agriculture of the alluvial delta area of Mississippi consists mainly of row crops, of which cotton is the most important. Originally, the area was covered with a forest consisting of broad leaf trees and of Cyprus. The sandier soils are easily handled and the crop yields are generally good. The heavy clay soils are difficult to handle and the crop yields are often poor. It was obvious that wet subsoils and poor aeration were factors limiting crop production on the soils derived from Selma Chalk in the Mississippi-Alabama blackbelt. The heavy clay soils in the Mississippi Delta area 'were believed to be less productive than similar soils containing more sand because of poor internal drainage and, consequently, poor aeration. The sandier soils of the Mississippi Delta were considered poorly aerated during prolonged rainy seasons. Imperfect drainage affects plant growth chiefly in the manner in which it affects soil aeration. Factors that influence the aeration of soils have been excellently reviewed by Clements ( 7)3 and by Rommel (17). Only a limited amount of work has been done on the effect of soil aeration on cotton root growth. Balls (I) in Egypt found that cotton roots died, apparently from asphyxiation, when the water table rose. Cannon and Free ( 6 ) , in laboratory studies, found that cotton roots did not grow when oxygen values in the soil approached 1% oxygen or less. The minimum percentage of oxygen for cotton root growth was somewhat variable and, also, was influenced by soil temperature. The original purpose of the investigation reported here was to determine the influence of tillage on cotton root growth and soil aeration under Houston clay and soils of the Sarpy series. The influence of tillage, but not of soil aeration, has already been reported for Houston clay ( 1 2 ) . It was necessary to have a general picture of the seasonal changes in cotton root growth and soil aeration in order to evaluate properly the effect of tillage treatments. After the study was underway, the importance of aeration on the presence and severity of the cotton-