Effect of N-fertigation Frequency on the Lint Yield , Chlorophyll, and Photosynthesis Rate of Cotton

Abstract

The objectives of this study were to evaluate the e ffects of nitrogen fertigation frequency on lint yield, lint properties, chlorophy ll 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 dri p-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 cyc les (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 reading s ranged from 40.1 to 54.9, depending on the treatment and e xperimental 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 t he treatments. One possible reason for the lack of difference in PR, o r 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 condition s, age, and location of the leaf on a plant. Keywords: Cotton, Chlorophyll (SPAD), Drip irrigation, Nitro gen, Photosynthesis rate.