effect of n-fertigation frequency on the lint yield, chlorophyll, and photosynthesis rate of cotton

the objectives of this study were to evaluate the effects of nitrogen fertigation frequency on lint yield, lint properties, chlorophyll content (spad readings), and the photosynthesis rate (pr) of cotton. this study was carried out in the southeastern anatolia region of turkey in 2011 and 2012 with drip-irrigated cotton. the maximum lint yield (1,856 kg ha-1) was obtained with one lateral for every two rows and the application of equal doses every two irrigation cycles (10 days). fertigation frequency of every two irrigation cycles (10 days) increased (p≤ 0.05) the fiber strength (32.3 g tex-1), the fiber elongation (6.5%), and the fiber length (28.9 mm). the spad readings ranged from 40.1 to 54.9, depending on the treatment and experimental year. there was no significant difference (p≤ 0.05) among the spad readings. the pr ranged from 35.9 to 74.7 µmol m-2 s-1, and there was no significant difference between the treatments. one possible reason for the lack of difference in pr, or spad, was that there was no difference in the total amount of nitrogen applied in the different treatments. the pr measured in cotton leaves may also change depending on the environmental conditions during measurement, prevailing ecological conditions, age, and location of the leaf on a plant.