Influence of nutrient levels and plant growth regulators on relative chlorophyll content (SPAD value), days to 50% flowering and nodulation of soybean (<em>Glycine max</em>)

Abstract

A field experiment was conducted to study the influence of nutrient levels and foliar application of plant growth regulators on relative chlorophyll content (SPAD value), days to 50% flowering and nodulation of soybean [Glycine max (L.) Merrill] during kharif 2017. The experiment was laid out using randomized complete block design (factorial concept) with 14 treatments including control and replicated thrice. The treatments consisted of two nutrient levels 125% RDF and 100% RDF, six plant growth regulator (PGR) dosages: salicylic acid @ 50 and 100 ppm, ethrel @ 100 and 200 ppm, chlormequat chloride (CCC) @ 250 and 500 ppm; independent control: RPP, without PGR spray and RPP + KNO3 @ 1%. PGRs were sprayed at 25 and 40 DAS. Results shows that application of 125% RDF + chlormequat chloride @ 500 ppm at 25 and 40 days after sowing (DAS) as foliar spray recorded significantly higher relative chlorophyll content (SPAD value) compared to other treatment combinations and control, followed by 125% RDF + ethrel @ 200 ppm. Numerically application of ethrel (200 ppm) initiated early flowering (42.9 days for 50% flowering) in soybean. 125% RDF treatment statistically observed higher number of nodules and nodule dry weight on per plant basis.