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A method was developed to maintain the oxygen content of soil air in pots at different levels by means of a controlled diffusion technique. The yield of plant tops and roots was reduced by low soil oxygen contents. Decreasing the soil oxygen contents also reduced the percentages of K, Mg, P, and N found in the plant tops, while the percentage values for these elements in the roots increased. These results indicated that low soil oxygen may affect the translocation of ions from the roots to the tops more than absorption of these elements from the soil. Elements other than potassium, particularly phosphorus, were of importance in explaining reduced yields with low soil oxygen contents. When gaseous diffusion between soil and the atmosphere was eliminated after a period of normal plant growth, the percentages of K and Ca in the tops were reduced while the percentages of these elements increased in the roots. Again, the data indicated a translocation effect resulting from poor aeration.

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P HOSPHATIC fertilizers have been used in relatively large amounts for many years on considerable acreages in the South. Since soils in this area have been well phosphated, is it possible either to discontinue or reduce the amount· of phosphatic fertilizer used and still maintain good crop yields? This question has been. considered by agronomists for many years, but the answers are still variable. A number of factors play a very important role in affecting the availability of residual phosphorus. Of these probably the most important are, first, the capacity of a soil to fix phosphorus in an unavailable form; second, the amount of phosphatic fertilizer applied; and third, t_he kind and use of the crops grown.Ware, Brown, and Yates (II) 3 studied the residual effect of phosphorus on Irish potatoes-in southern Alabama. They found that soils which received 240 pounds of P20 6 per acre annually for 4 years dropped from 66 to 24 p.p.m. of available phosphorus 4 years after phosphate applications were discontinued. Likewise, when 240-pound applications were followed by 120-and 6o-pound applications of P 2 0 6 , the available phosphorus dropped from 66 to 34 and 25 p.p.m. of phosphorus, respectively, in 4 years. The yields of potatoes also dropped considerably when the 240-pound rate of P20 6 was followed by r2o-, 6o-, or a-pound rates of P20 5 . They concluded that the effects of phosphorus applications were apparent for a considerable number of years after phosphorus applications had been discontinued. Since the capacity of a soil to fix phosphorus is directly related to the residual effect of applied phosphorus; the reader is referred to the work of Weiser (12) and Midgley (6) who have reviewed quite extensively this phase of the literature. · Another factor, the loss of phosphorus by erosion, which has not been investigated very extensively until recent years, app_ears to be playing a very important part in reducing the residual effects of phosphorus. Scarseth and Chandler (8) reported that 6o% of the phosphorus applied as superphosphate was lost from a light-textured soil during a period of 26 years. Many other investigators (1, 2, 4, 5, 7) have reported that varying amounts of plant nutrients have been lost by erosion.The purpose of this paper is to report the results of an experiment in which the residual effect of phosphorus on cotton was studied.