TECHNICAL
GROWING ORGANIC ONIONS Words by Mike Nichols & Martyn Callaghan
Martyn Callaghan with onions grown from sets, early January, Pukekohe. Direct seeded already harvested
Though production costs for organic onions can be higher than conventional onion growing, there is a considerable price premium for the product due to consumer demand. Organic onions can fetch prices double that of the conventionally grown product at times. However, the use of set grown onion production has the potential to reduce organic onion growing costs. The profit margin for growing onions conventionally is considered to be only about $NZ2.00 per bag, which on a per hectare crop of 50 tonnes is not huge for the use of land for nearly 12 months. Of course, if you are producing organically then the crop must be grown on an organically certified site, which takes a few years to obtain, but clearly the potential rewards are considerable. John Bostock is one of the few growers of organically certified onions in New Zealand, and in NZ Grower some years ago (Anon, 2019) it is stated that one of the major costs of organic onion production is weed control as no chemical herbicides are permitted, and there is a limit to how much mechanical cultivation is possible, so hand weeding becomes a necessity. This is because onions are very small seedlings initially and do not compete strongly with weeds. This is exacerbated due to their upright growth habit. 60
NZGROWER : APRIL 2021
Flame weeder
When growing onions conventionally the practice is to spray with a contact weed killer just prior to seedling emergence, and to combine this spray with a residual herbicide which will kill weed seedlings germinating later. Thus the onions emerge into a weed free soil, which remains weed free for several weeks. Once the onions have become established there is a wide range of herbicides which can be safely applied to the onions as they grow larger. With organic onions the standard weed control method is to use a flame weeder (see photo) just prior to seedling emergence, and then to use a combination of between the row hoeing (using a steerage type hoe) supported by in the row hand weeding. Because direct seeded onions require a long growing season (June to January), much of the critical
