Evaluation of Growth Stimulants on Short-day Onions

Abstract

<jats:p>A 3-year study on the effects of growth stimulants on yield, bulb size, bulb quality, and storability of short-day onions (<jats:italic>Allium cepa</jats:italic> L.) was conducted at three locations. Treatments included 2-hydroxypropanoic acid, humic acids, humic acids in conjunction with micronutrients, and two formulations of cytokinin applied as a transplant dip and/or plant spray. There were no differences between 2-hydroxypropanoic acid and an untreated check at two different farm locations for onion yield, equatorial bulb diameter, or percent jumbos [≥3 inches (≥7.6 cm)] in 1997. Comparisons between untreated checks, 2-hydroxypropanoic acid, humic acids as a transplant dip or plant spray, and humic acids with micronutrients, all applied as transplant dip or plant spray, indicated there were no differences among treatments for yield, pungency, soluble solids, equatorial bulb diameter, or percent marketable bulbs after 6 months in controlled atmosphere storage in 1997-98. In a final experiment, these treatments were evaluated in a factorial arrangement using the short-day onion cultivar Pegasus and a mixture of cultivars WI-609 and WI-3115, which are referred to as Wannamaker cultivar mix. `Pegasus' displayed higher yield and lower soluble solids than the Wannamaker cultivar mix. Treatment with humic acids and micronutrients, or cytokinins resulted in greater percent marketable bulbs after 4.5 months of controlled atmosphere storage compared to the untreated check. No differences were observed among the treatments for pungency or bulb size. In addition, there was no treatment by cultivar interaction.</jats:p>

Humic Substances Generally Ineffective in Improving Vegetable Crop Nutrient Uptake or Productivity

“…U.S. research suggests that, under representative field conditions, commercial HA formulations do not reliably provide agronomic benefits for vegetable production. Boyhan et al (2001) found no HS effects on onion yield in 3 years of field trials but reported enhanced storage life in 1 year. Feibert et al (2003) and Duval et al (1998) reported no benefit from HS application in field production of onions and mustard greens, respectively.…”

Humic and fulvic acids as biostimulants in horticulture

“…yellow passion fruit; Cavalcante et al, 2013). An increase in rooting, growth and early flowering were observed in some studies with ornamental plants (Baldotto et al, 2010(Baldotto et al, , 2012Baldotto, 2013, 2014), whereby HS application was successful in substituting the more expensive plant growth regulators (Boyhan et al, 2001).…”

“…The optimum concentration was dependent on the specific plant and mode of application (foliar spray or direct soil drench). An increase in nutrient use efficiency was found to be the major biostimulant effect associated with the promotion of vegetable crop growth by HS (Boyhan et al, 2001;Neri et al, 2002;Selim and Mosa, 2012;Naidu et al, 2013;Denre et al, 2014). This was followed by a decrease in the incidence of plant disease (Zaller, 2006;Singh et al, 2010;Naidu et al, 2013;Olivares et al, 2015).…”

“…This was followed by a decrease in the incidence of plant disease (Zaller, 2006;Singh et al, 2010;Naidu et al, 2013;Olivares et al, 2015). Another important aspect was the significant effect on the commercial quality/marketable values of crop products (Boyhan et al, 2001;Neri et al, 2002;Selim and Mosa, 2012;Naidu et al, 2013;Farahi et al, 2013;Denre et al, 2014). In some cases, a better crop response was observed using humic-like substances obtained from compost or vermicompost than from humic extracts from leonardite (the most common commercial source) Azcona et al (2011), and more by humic acids than by fulvic acids (Lulakis and Petsas, 1995).…”

Growth Regulators Do Not Increase Onion Bulb Size or Weight Under Greenhouse Conditions

“…It is not clear if these materials actually affect onion bulb development and sizing. Boyhan et al (2001) used a 0.012% solution of a commercially available cytokinin and reported that there was no benefit to yield of onion. Since the use of these materials on onions is relatively new there is little information on what amounts of which growth regulators are needed, or when they should be applied, to affect developing onion plants.…”