The Cultivation Phase: Soil Treatment and Approved Pesticides

Hemp Soil Requirements & Approved Pesticides

Hemp Soil Requirement, Approved Pesticides, Nutrients

As of December 2019, The US Environmental Protection Agency (EPA) approved adding hemp to the use sites of 10 pesticides. Of those, 9 are biopesticides and one is a conventional pesticide.

Although hemp can successfully grow without the aid of pesticides, the news of the approval came as a welcomed change to cultivation rules and regulations. Hemp is resilient, but it still an arduous and time consuming process to cultivate and harvest. Farmers will take any type of assistance and aid that they can to grow hemp more effectively and efficiently, especially if these pesticides can help decrease the cost per acreage (thus increasing profit margins per acre).

The EPA website also states that on an ongoing basis it they process applications they receive to amend product labels to add use on hemp.

Visit their website for updates, but currently the 10 approved pesticides are as follows:

Biopesticides

  • EPA Registration Number: 70310-5. Applicant: Agro Logistic Systems, Inc. Active ingredients: Azadirachtin and Neem Oil. Product type: Insecticide, Miticide, Fungicide, and Nematicide. 
  • EPA Registration Number: 70310-7. Applicant: Agro Logistic Systems, Inc. Active ingredients: Azadirachtin and Neem Oil. Product type: Insecticide, Miticide, Fungicide, and Nematicide. 
  • EPA Registration Number: 70310-8. Applicant: Agro Logistic Systems, Inc. Active ingredients: Azadirachtin and Neem Oil. Product type: Insecticide, Miticide, Fungicide, and Nematicide. 
  • EPA Registration Number: 70310-11. Applicant: Agro Logistic Systems, Inc. Active ingredient: Neem Oil. Product type: Insecticide, Miticide, and Fungicide. 
  • EPA Registration Number: 84059-3. Applicant: Marrone Bio Innovations, D/B/A Marrone Bio Innovations, Inc. Active ingredient: Extract of Reynoutria sachalinensis. Product type: Fungicide and Fungistat. 
  • EPA Registration Number: 84059-28. Applicant: Marrone Bio Innovations, D/B/A Marrone Bio Innovations, Inc. Active ingredient: Bacillus amyloliquefaciens strain F727. Product type: Fungicide. 
  • EPA Registration Number: 91865-1. Applicant: Hawthorne Hydroponics LLC, D/B/A General Hydroponics. Active ingredients: Soybean Oil, Garlic Oil, and Capsicum Oleoresin Extract. Product type: Insecticide and Repellent. 
  • EPA Registration Number: 91865-3. Applicant: Hawthorne Hydroponics LLC, D/B/A General Hydroponics. Active ingredient: Bacillus amyloliquefaciens strain D747. Product type: Fungicide and Bactericide. 
  • EPA Registration Number: 91865-4. Applicant: Hawthorne Hydroponics LLC, D/B/A General Hydroponics. Active ingredient: Azadirachtin. Product type: Insect Growth Regulator and Repellent. 

Conventional Pesticides

  • EPA Registration Number: 91865-2. Applicant: Hawthorne Hydroponics LLC, D/B/A General Hydroponics. Active ingredient: Potassium Salts of Fatty Acids. Product type: Insecticide, Fungicide, and Miticide. 

 

Hemp Soil Requirements

Detailed information comes from the online edition of Robert A. Nelson’s webpage on Hemp Husbandry (Copyrighted 2000) which is said to be based on a United Nations study. The following highlights the study's most important information, but please visit the study to learn more.

  • As N [Nitrogen] increases relative to Mg [Magnesium], CBD increases relative to CBN.
  • Increasing the ratio of N to Cu [Copper] increases the level of CBD.
  • Increasing amounts of P [Phosphorus] converts CBN to THC. Low to medium levels of P produces a high level of CBD, but CBD decreases with high levels of P.
  • Low levels (levels less than 40 ppm) of Mg produce more CBD than do high levels of Mg. As levels of Mg increase relative to Ca, the concentration of THC decreases.
  • The concentration of Mg and Fe [Iron] in leaves is positively correlated to THC levels.
  • Potassium increases the concentration of CBN by effecting the dehydrogenation of THC.
  • An excess of K [Potassium] in the 3rd month will inhibit resin production. Excess Ca will inhibit resin production, and it increases the production of CBD in the resin.
  • Either an excess or deficiency of Mg produces more CBD.
  • 5 ppm Fe gives highest yields of THC.”

 

Nitrogen

With respect to hemp, nitrogen is removed at approximately 200 actual kg/ha. For a more specific metric, the nitrogen is removed at 160 kg/ha (stalk) and 40 kg/ha (seed). Nitrogen removal can start to increase depending on where the hemp is grown. In general, any hemp that is grown in a field is going to have a higher amount of nitrogen compared to its alternatives. This is essential and something all growers should keep in mind during the growth phase. 

Nitrogen and potassium are immediately leached out during the retting process, which can start to settle in the soil over time. In most cases, phosphorus has been studied as being a common nutrient that is stored in the seed. However, nutrients other than phosphorus can also be seen in the stalks. 

The growth rate for hemp tends to vary but it generally settles somewhere between 7-10 cm/day in the summer months (July-August). This is known as its vegetative state. When it moves onto the development stage, the nitrogen production starts to rise and can get up to approximately 6.7 kg N/ha/day, while also seeing an increase in phosphorus update (1.56 kg P2O5/ha/day). 

It's important to note hemp seed is generally known to be sensitive to seed-placed nitrogen fertilizer. As a result, it's important to make sure the nitrogen is mid-row-banded. 

 

Phosphate

Phosphate is commonly associated with hemp. Hemp tends to use a high amount of phosphate as the crop is being established. This becomes noticeable as the growing season wears on. Since phosphate tends to remain close to the roots, it is reserved for the soil and stays there. Hemp has shown to work around this depending on the seed but this can vary from situation to situation. Factors that play a role in this regard can include soil moisture, soil type, and seed opener spread. Each of these variables will play a role in the seed and how it is affected by the phosphate. As a result, it's important to keep an eye on these variables at all times. 

Additional studies have been run on this subject including assessing phosphate fertility and how it works in hemp. Studies have revealed there's a certain amount of tolerance when it comes to seed placed phosphate. As long as the growing conditions are perfect, the hemp seed can continue to do well on a per-acre basis. For those working on managing growth in such conditions, the rate should remain at approximately 31-40 pounds per acre. This is assuming the growing conditions are in good shape and will not hamper the growth phase for the hemp seedlings.

When the conditions aren't ideal, seed placed phosphate can do a tremendous amount of damage leading to a loss of germination. This is often seen when cool and/or wet compacted soils are present. The same applies to seed placed fertilizer that is used on younger plants. This can lead to the plants dying out and not adapting to the conditions. 

 

Micronutrients

The idea of micronutrients refers to smaller quantities that are rated at around 100 ppm based on plant dry weight. The micronutrients are not the same as macronutrients. With micronutrients, it is quite rare to see issues pop up in hemp in comparison to macronutrient deficiencies. This is often assumed to have more to do with how these variables are studied by researchers. If additional research was done on the subject, it may reveal a larger pattern.

 

Nutrient Application Rates *

Nitrogen        90 to 135 kg/ha

Phosphorus  45 kg/ha

Potassium    65 kg/ha

Sulfur           15 kg/ha


*These rates include soil supplied nutrients plus applied.

 

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