The effect of 2-chloroethylphosphonic acid foliar application on stem yield components and sex expression in fiber hemp ’Marina’

Abstract

Quantitative variations in the sex ratio significantly affect the industrial hemp (fiber hemp) cultivation, since the production is closely related to the reproductive biology of the species. Both dioecious and monoecious varieties are cultivated, but only monoecious ones enable simultaneously mechanized harvesting of stalks and grains. 2-chloroethylphosphonic acid (Ethrel®) is a synthetic plant growth regulator that affects sex expression and suppresses stem elongation and plant growth. Thus, four various dosages of Ethrel® were applied as foliar sprays to fiber hemp plants cv. Marina, twice- in stage of flower primordia and, two weeks later in stage of flower formation. The trial was set up in Bački Petrovac at experimental field of the IFVCNS, as completly randomized block design in three replicates. Sex ratio in the control plots was 37.11 to 62.89% in favor of femail plants. Although the ratio significantly changed with increase of applied Ethrel dosages (47.84 to 52.15 at maximal applied Ethrel concentration, 2.5 ml l-1), the total grain yield significantly decreased only if plants were treated with the highest dosage, 748.04 kg ha-1 compared to 836.81 kg ha-1 in control plots. Treated plants had shorter stems (276.78 cm and 233.84 cm in control and plants treated with 2.5 ml l-1 of Ethrel, respectively) with lower fiber content. The fiber content in these stems was by 8% lower (20.10%) compared to the stem fiber content of the control plants (28.25%). The applied Ethrel treatments had no statistically significant effect on the hemp stem diameter.