Hello Everyone!
In this blog, you will find several links to topics I believe could be beneficial to you. The first link is to a resistant weed chart developed by chemical companies to help farmers manage resistant weeds in 2016. The second link is to a chart showing how to calculate soluble fertilizer rates for tobacco greenhouses.
Herbicide Classification Chart
Tobacco farmers will start seeding greenhouses soon and listed are some suggestions that may help you when you call on growers. Most tobacco farmers are very successful growing quality transplants, but as greenhouses get older problems can occur. Listed are some steps you can follow to help your growers stay successful.
Step 1 Encourage your growers to collect a source water sample and send to an accredited laboratory for analysis. If there are problems such as high bicarbonate levels, amendments can be made before floating trays. Nutrient levels in the source water sample might also influence choosing the correct fertilizer analysis. If you have never taken a water sample, I encourage you to do so. I will be glad to teach you how to understand the report. Below are some water samples from various laboratories.
Step 2 Choose the correct fertilizer. Some areas of the state have water with either a low pH or a high pH. Some water contains a trace of boron and others may have a high level of boron. Some wells may be contaminated with nitrates and others may have very little nitrate in the water. The report will tell you. Knowing this will allow you to help your customers choose the right fertilizer.
Step 3 Many growers have old trays that are difficult to clean. Encourage growers with old trays not to fill water beds too far in advance of seeding. Studies have shown an increased level of Pythium issues that occur early when water is allowed to warm.
Step 4 Purchase a conductivity meter and help your growers monitor the ppm level in float beds during the growing season. Learn how to calculate water volume in float bed and how to maintain ppm level. Fertilizer recommendations are made on a per 100 gal basis. Accidents can happen such as a leak in a bed or a bed could be over filled. Helping the grower recover can go along way in building a relationship. It is also a good idea to collect a nutrient solution sample during the growing season to make sure the calibration on your conductivity meter is correct. I’ll be glad to assist you here because there is so much you can learn.
Step 5 How to calculate water volume. Most float beds are 16 ft wide x 96 ft long with a water depth of 4 inches. Example: 16 x 96 x .33 = 506.88 cu ft. The conversion factor for cu ft to gallons is 7.48
506.88 x 7.48 = 3791.46 gallons of water per bed
rounded off = 3800 gallons/bed
Step 6 Below is table 4.6 from the NCDA Fertility Handbook that shows nutritional sources on a ppm basis.
The nitrogen % of the fertilizer is used to calculate rate on a ppm basis. Let’s assume the grower wants to apply 100 ppm of a 20-10-20 fertilizer to a standard size water bed before floating trays. How much should he apply to the bed? The formula used is: Concentration/ N % x .75 = 100ppm/15ppm = 6.6 oz/ 100 gals
6.6 oz/ 100 gals x 38 (100) gals = 253.3 oz per bed or 253.33 oz/ 16 oz = 15.83 lbs per 3800 gallons
rounded off to 16 lbs.
| Table 4.6 Fertilizer dilutions necessary (oz/100 gal. water) to deliver parts-per-million (ppm) rates * |
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|---|---|---|---|---|---|---|---|---|---|---|---|
| ppm soln. |
Percent Element in Fertilizer | ||||||||||
| 10 | 13 | 15 | 16 | 18 | 20 | 25 | 30 | 33.5 | 46 | 50 | |
| 50 | 6.7 | 5.1 | 4.4 | 4.2 | 3.7 | 3.3 | 2.7 | 2.2 | 2.0 | 1.5 | 1.3 |
| 100 | 13.3 | 10.3 | 8.9 | 8.3 | 7.4 | 6.7 | 5.3 | 4.4 | 4.0 | 2.9 | 2.7 |
| 125 | 16.6 | 12.8 | 11.1 | 10.4 | 9.3 | 8.3 | 6.7 | 5.6 | 5.0 | 3.6 | 3.3 |
| 150 | 20.0 | 15.4 | 13.3 | 12.5 | 11.1 | 10.0 | 8.0 | 6.7 | 6.0 | 4.3 | 4.0 |
| 175 | 23.3 | 17.9 | 15.6 | 14.6 | 13.0 | 11.7 | 9.3 | 7.8 | 7.0 | 5.1 | 4.7 |
| 200 | 26.7 | 20.5 | 17.8 | 16.7 | 14.8 | 13.3 | 10.7 | 8.9 | 8.0 | 5.8 | 5.3 |
| 250 | 33.3 | 25.6 | 22.2 | 20.8 | 18.5 | 16.7 | 13.3 | 11.1 | 10.0 | 7.2 | 6.7 |
| 300 | 40.0 | 30.8 | 26.7 | 25.0 | 22.2 | 20.0 | 16.0 | 13.3 | 11.9 | 8.7 | 8.0 |
| 350 | 46.7 | 35.9 | 31.1 | 29.2 | 25.9 | 23.3 | 18.7 | 15.6 | 13.9 | 10.1 | 9.3 |
| 400 | 53.3 | 41.0 | 35.6 | 33.3 | 29.6 | 26.7 | 21.3 | 17.8 | 15.9 | 11.6 | 10.7 |
| 450 | 60.0 | 46.2 | 40.0 | 37.5 | 33.3 | 30.0 | 24.0 | 20.0 | 17.9 | 13.0 | 12.0 |
| * Equivalent units: 1.0 lb = 454 g = 16 oz; 1.0 oz = 28.38 g. The equation for calculating the amount of fertilizer to mix in 100 gallons of water is shown below: ppm of desired element ÷ percent of element × 0.75 = oz/100 gal. |
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Step 7 Help your growers monitor plant health by checking for salt injury shortly after germination. This is a frequent problem and occurs when all of the fertilizer is put in the bed before floating trays. Whatever is in the water is wicked into the germinating cell when the tray is floated. Often if condensation occurs inside the greenhouse and the house needs ventilation, air flowing across the surface of the trays can cause salt levels to increase. Catching salt injury early and flushing overhead with pure water is the best way to minimize injury and promote uniformity.
These few suggestions may help you help your customers get plants off to a good start. Other problems may develop during the greenhouse season but if they do please feel free to give me a call!
Sincerely,
Rick Morris
Harvey’s Agronomist