Irrigated N rate studies were conducted for three years on 4 varieties on Sharkey silty clay at Keiser, AR. Petiole samples were taken weekly from the week before first bloom until a total of 8 weeks samples had been collected. The petioles were subsequently analyzed for nitrate-N. The petiole nitrate concentration together with yield were then used in X(2) statistical procedures to try to establish curves for the cotton's nitrogen nutritional status. This X(2) procedure was found to work very well for the first week or two of sampling. After the week of first bloom petiole nitrate-N analysis at one date alone was not sufficient criteria for establishing the N nutritional status. We found that as cotton with various degrees of N deficiency when plotted as petiole nitrate-N content versus time of sampling would intersect the time line prior to the fifth period. On this heavy clay soil we did not determine the criteria for determining cotton's N nutritional status after the fifth week of sampling criteria other than petiole nitrate-N content are necessary for determining cottons N nutritional status on this clay soil.