Abstract
Field experiments were conducted to investigate the use of portable chlorophyll meter to improve nitrogen management during the growth period of cotton at Central Cotton Research Institute, Multan. The treatments consisted of six nitrogen levels i.e. 0, 50, 100, 150, 200, 250 kg ha-1 , arranged in RCB design with four replications, applied at planting, first flowering and peak flowering phases. Cotton cultivar CIM-534 was planted during second week of May at spacing 75 cm between rows and 30 cm between plants. Results indicated that applied nitrogen fertilizer showed highly significant relationship with chlorophyll meter readings. The SPAD values increased from 52.2 to 64.2 as nitrogen fertilizer was increased from 0 to 250 kg ha-1 . Results showed that seed cotton yield and its components differed significantly due to the application of different levels of nitrogen fertilizer with a range from 1731 to 2521 kgha-1 in various treatments. Main stem height, number of nodes on main stem and inter-nodal length increased significantly with the increasing dose of nitrogen fertilizer. The values of main stem height ranged from 79.5 to 119.7 cm and the nodes on main stem ranged from 23 to 31. The relationships between seed cotton yield and nitrogen doses showed that seed cotton yield increased with the increasing levels of nitrogen fertilizer. Regression analysis exhibited highly significant relationship of nitrogen doses with seed cotton yield and SPAD values. Chlorophyll meter is being used in different parts of the world to measure the chlorophyll contents (SPAD value) of leaves for N management during the cropping season. Keeping the above facts in view, there is a need to quantify chlorophyll meter readings for matching N levels during the cotton growing season.
