Effect of Certain Growth Substances on Growth, Chemical Composition, and Productivity of Egyptian Cotton, Giza 95 Variety Under Two Planting Dates

Abstract

Two field experiments were executed during the 2021 and 2022 seasons at Sids Agricultural Research Station, in Beni-Suef Governorate, Egypt to study the effect of foliar spraying with two growth regulators, i.e. indole -3-butyric acid (IBA) at two levels (20 and 50 ppm) and 1-naphthalene acetic acid (NAA) at two levels (30 and 50 ppm) in addition to the control (spraying only water) under two planting dates (during April and May) and their interactions, on growth, chemical composition, water relations, fiber quality, and productivity of cotton Giza 95 var. Data indicated that early planting date (1st April), foliar spraying with 50 ppm of IBA and their interactions resulted in significant increase on leaf photosynthetic pigments, total soluble sugars, N, P, K, IAA, GA3, and kinetin concentration, leaves total water content and relative water content in both seasons and significantly decreased proline, phenols, ABA, and plasma membrane permeability (which supports and confirms membrane integrity). In addition, early planting date (1 st April) and foliar spraying with 50 ppm of IBA resulted in a significant increase in sympodia, open bolls number/plant, earliness percentage, and seed cotton yield/fed in both seasons, boll weight, and seed index in the second season only. The interaction between them gave the best results. It is advisable to apply early sowing and spraying IBA at 50 ppm twice (at start and top of flowering) to realize the most efficient effects on improving productivity and increasing the efficiency use of heat units.