Maximizing onion and economic feasibility of growing onions from plug transplants

View the project final report

• 2008 annual report

Commodities

• Vegetables: onions

Practices

• Production Systems: general crop production

The problems onion growers face by importing bare root transplants into New York include: i) availability of skilled labor to transplant the crop in a timely manner; ii) the task of transplanting them into the field is labor-intensive and very costly; iii) they risk bringing in serious pests of onions; and iv) the rate of return of transplants on seed is inconsistent. These problems threaten the sustainability of the onion industry in New York. An alternative would be to use locally grown greenhouse plug transplants. Opportunity also exists for growers to adopt new automated plug transplanting technology, which would drastically reduce the need and cost of manual labor. The reasons why onion growers have not adopted growing onions from plug transplants are: i) plugs cost 3 times more than bare roots; and ii) onions grown from bare roots yield significantly higher with significantly more jumbo sized bulbs than those grown from plugs, netting significantly more profit per acre. Successful demonstration and evaluation of adjustments to the standard method of growing onions from plug transplants that make yield, bulb size and economics comparable to that of bare roots, in addition to demonstrating the benefits of plug transplants including how they are less labor intensive and cost less to transplant, and are produced free of pests, will result in grower adoption of using locally grown plug transplants and automated plug transplanting technology. This would benefit local economies and most importantly, sustain the viability of the northeastern onion industry.

We propose to demonstrate and evaluate yield, bulb size and economic feasibility of 3 adjustments to the standard method of growing red onions from plug transplants in comparison to the standard plug method and to growing onions from bare roots.

This project will build on a previous project funded by a Northeast SARE Partnership grant in 2006 where we conducted a thorough comparison of onions grown from bare root and plug transplants. In that study, onions grown from bare roots netted 29% and 26% more profit per acre than those grown from plugs, values of $1898 and $2156 for a yellow and red variety, respectively. The major difference between bare roots and plugs was attributed to the bare roots yielding 2 times more jumbo sized bulbs than plugs, which were worth more money, especially for the red variety. In another year, plugs could perform more favorably to bare roots for several reasons. First, onion prices in 2006 were 5 to 7 times the 5-year average. Lower onions prices and less difference in price among size classes could minimize the difference in net profit between plugs and bare roots. Second, the growing season in 2006 was favorable for producing large onions. Fewer jumbos and higher proportions of small and medium onions could minimize the net profit between plugs and bare roots. Finally, bare roots had 3 to 4 times higher incidence of neck rot out of storage compared to the plugs, a result of the transplant seedlings being contaminated with the neck rot pathogen. In a year that is more favorable for spread and development of neck rot, storage losses could have greater economic impact on bare roots. This justifies the need to compare the standard method of growing plug transplants with bare roots another year.

In the 2006 study, having 3 plants per hole was too crowded in the field and bulb size was clearly compromised. It was observed that out of the 3 plants per hole, often there were either 2 big and 1 small bulb or 1 big and 2 small bulbs, while holes with 2 plants had evenly sized bulbs that appeared comparable to the singly planted bare roots. In this project, we will compare plugs grown with 2 plants per cell to the standard of 3 plants per cell to see if we can achieve comparable yield and size to bare roots.

The cost of plug transplants is based on the amount of greenhouse space used to grow them. In the 2006 study, we found that the cost of plug transplants was 3 times higher than it was for bare roots (including cost of shipping from Arizona to New York), a difference of about $600 per acre. When the number of plants per cell is reduced from 3 to 2, the amount of greenhouse space required to grow them would remain the same when standard plug trays (288 cells per tray) are used. When using 8 inch plant spacing, planting 2 plants per hole would result in a plant population that is 33% less than the 3 plants per hole configuration and identical to the bare root plant population and the cost of seed would be 33% less. In this study we will evaluate 2 plants per cell grown in trays that have 392 and 512 cells per tray, which would require 26% and 44% less greenhouse space, respectively, than the standard. When the 33% reduced cost of seed is factored in, this results in plugs costing only 1.6 times more and 2.5 times less than the cost of bareroots for 392 and 512 cell trays, respectively. Rising costs of fuel will increase the cost of shipping bare roots and the cost of bare roots.

Generally, there is a trend that as cell volume decreases, yield and bulb size decreases. Also, as the number of plants per cell increases, yield and bulb size decreases. In a study in Texas, researchers found no difference in total yield between onions grown from transplants produced in 392 and 512 cell trays but the 512 cell trays had slightly fewer jumbos. Unlike in previous studies, this project will focus on growing a red long-day onion variety as opposed to short-day and sweet varieties. Also, this trial will be conducted on a commercial scale, not as small plot research at an experiment station.