You want to grow great onions and save water, right? This article shows you how to do both. Whether you prefer your onions chopped, diced, grilled or sautéed, you need to know the best way to grow onions while maximizing water savings. Onions are an annual short-season crop that can generally be grown in a variety of conditions ranging from a light sandy loam soil to a heavy peat/muck. With approximately 75,000 acres planted annually in the U.S. representing approximately $900 million, growers are learning that onions require an aggressive approach to maximize yield and quality.
Items to consider in seed and variety selection are:
- Growing degree days (12 hours of daylight for short day onions and 16 hours of daylight for long day onions)
- Market type: white, red, yellow
- Seed that is resistant to disease and insect pressure
- Select a seed that is coated to help improve planting uniformity. Also consider “priming” a seed which is a way of initiating the germination process before it’s planted to get a quicker harvest
Onions are generally planted in a firm bed with a precision planter to help ensure a specific population per acre. The spacing is typically 4” between plants and 12” between rows. A common bed configuration is 40” beds with 4 rows of onions planted on the bed top. The seed is planted about 0.5 to 1 inch below the soil. Plant population is around 120,000 plants per acre to achieve a 3 – 4 inch diameter onions.
Most onions require about 30 inches of water per season to grow a good crop with drip irrigation. The key is to provide about 0.3 – 0.4 inches/day – drip irrigation is the best way to apply small amounts of water frequently. Generally, one line of tape to supply 4 rows of onions is adequate. It’s important to maintain good soil moisture during the 8th leaf stage which is when bulb formation begins. Good moisture monitoring will result in increased yields, single centers, and better storage conditions.
Because storage onions do not perform well with water near the onion bulb, it’s important to match the application rate of the drip tape with the soil infiltration rate. The goal is to provide enough water to the plant without puddling. Common tape products to help achieve this will include:
- Chapin Drip Tape 5 & 6 MIL –12”spacing — .25GPM/100’ (View Details)
- Turbo Tape Drip Tpae 5 & 6 MIL –Echelon Flow Track – 6” .25GPM/100’ and 8” .20GPM/100’ (View Details)
Because onions develop little leaf area, it’s difficult for onions to compete with weeds that may have a more aggressive leaf area. A few ways to reduce weed pressure are:
- Plant after a crop that has less restrictive herbicide regulations to reduce weed pressure
- Bed up in the fall to allow any weeds near the surface to germinate. Use a non-selective herbicide to eliminate the weeds before planting
- Use good pre-emergent and post-emergent herbicides at the proper rates to reduce weed pressure
- Drip irrigation can reduce the amount of water between rows which will reduce weed pressure.
With a shallow root system of around 18 inches, it’s important to manage the fertility of the soil within the top foot to 1 ½ feet. Most fertilizer can be applied through the drip system – it’s important to make sure the uniformity of the system is above 90%. Listed below are some of the common fertilizers and their annual application rate:
- Nitrogen: 150 pounds per acre – there is plenty of nitrogen in the soil – always test the soil to determine existing amounts
- Phosphorus: 50 pounds per acre if soil testing shows 20-30 PPM in the soil. Phosphorus does not move well in the soil – need to band the fertilizer just to the side and below the seed
- Potassium: This is very abundant in many soils and should be added as needed depending on the PPM soil sample
- Zinc & Copper are two micronutrients that help the crop grow well and are often found in the irrigation water. Always get a water and soil sample to determine the amount to apply
For more information on Fertilizer, watch these online trainings here. Want to know how not to tear up when cutting an onion? The National Onion Association answers this question and many more here. Hopefully we have you fully prepared for your next crop of onions. If we missed anything or if you have further questions about onions please feel free to make comments below. If you enjoyed this article please consider subscribing to the blog.