Effect of ethrel and gibbrellic acid on bio-chemical changes and productivity of sugarcane (Saccharum species hybrid complex)

Abstract

The present study was conducted during the spring seasons of 2015–16 to 2017–18 to investigate the effects of application of ethrel and gibbrellic acid on growth, yield and sucrose content of spring planted sugarcane in order to work out its potential to be used as germination and growth enhancer in subtropical region. The treatments viz., planting of setts after overnight soaking in water, T₂ ; planting of setts after overnight soaking in 50 ppm ethrel solution, T₃ ; planting of setts after overnight soaking in 100 ppm ethrel solution, T₄ ; T₁ + GA₃ spray @ 35 ppm at 90, 120 and 150 DAP, T₅ ; T₂ + GA₃ spray @ 35 ppm at 90, 120 and 150 DAP, T₆ ; T₃ + GA₃ spray @ 35 ppm at 90, 120 and 150 DAP, T₇ and T₄ + GA₃ spray @ 35 ppm at 90, 120 and 150 DAP, T₈ were compared with T₁ (conventional planting/farmers practice treatment). Sugarcane growth, yield, and quality parameters were significantly influenced by various treatments. Owing to enhanced reducing sugars, acid invertase (AI), indole acetic acid oxidase (IAAO) and superoxide dismutase (SOD) activity in treated setts, planting of setts after overnight soaking in 50 ppm ethrel solution resulted in higher germination count at 10, 20, 30, 40 and 50 days after planting (DAP). Planting of setts after overnight soaking in 50 ppm ethrel solution + GA₃ spray @ 35 ppm at 90, 120, and 150 DAP resulted in a greater plant population at all stages of growth, which was responsible for a higher number of millable canes at harvesting. Treatment planting of setts after overnight soaking in 50 ppm ethrel solution + GA₃ spray @ 35 ppm at 90, 120 and 150 DAP recorded higher leaf area index at 180 and 240 DAP. Similarly, treatment (T₇ ) also recorded higher shoot and root dry weight at 120, 180, 240 and 300 DAP. Net assimilation rate during 120–180 DAP (5.78 g/m2 /day) and 180–240 DAP (3.95/m2 /day) were also recorded highest in treatment T₇ . Similarly, planting of setts after overnight soaking in 50 ppm ethrel solution + GA₃ spray @ 35 ppm at 90, 120 and 150 DAP recorded higher cane yield (101.2 t/ha) and net returns (166.25 × 103 `/ha) with a benefit: cost ratio of 1.31 which was significantly higher than farmers practice and planting of setts after overnight soaking in water. Thus, planting of setts after overnight soaking in 50 ppm ethrel solution + GA₃ spray @ 35 ppm at 90, 120 and 150 DAP should be adopted to obtain the maximum productivity and profitability by spring sugarcane.