Effects of varying nitrogen and potassium nutrition on spectral reflectance and physiological properties of cotton

Assessment of cotton's (Gossypium hirsutum L.) N and K nutritional status using spectral reflectance may aid in their efficient use. Field studies were conducted in 1998 and 1999 at the Plant Science Research Center at Mississippi State, MS to evaluate the effects of varying N and K nutrition on cotton lint yield, leaf pigment concentrations, and to assess cotton growth via selected remote sensing techniques. A two-factor factorial arranged in a randomized complete block design experiment consisting of 20 treatments was used. Fertilizer N at rates of 0, 45, 90, 135, and 180 kg ha -1 in factorial combination with K at rates of 0, 56, 112, and 168 kg ha-1 were applied.;Nitrogen and K nutrition were found to be effective in maximizing lint yield production. Nitrogen nutrition was found to influence leaf pigment concentration, but was dependent upon K nutrition. A specific nutrient deficiency, such as N, cannot be detected by leaf reflectance without prior knowledge of the sufficiency of other nutrients, such as K. The normalized difference vegetation index was determined to be effective as an indicator of vegetative biomass.