Before putting your valuable hemp plant material in the ground, you need to examine the stage. I’m talking about soil.
You’ve likely heard many things about growing hemp. “It doesn’t use much water,” or, “Any unfrozen soil will do,” and maybe even, “If you scatter it, they will come (‘it’ being seed and ‘they’ being million-dollar bank transfers).” Hemp’s revived market potential and sturdy nature certainly make it an attractive crop, but please know that your soil and care are still vitally important.
First things first. Get your soil tested. An extension office in your state can provide a list of labs that will do it. You’re looking for several things, and the USDA offers scientific detail if you’re so inclined.
Take your soil sample in late autumn or early spring for most useful results.
What type of soil do you have?
If you’re an experienced grower, you’ll know that soil is made up of one or more mineral particles that determine its texture. The texture will play a big part in your soil’s fertility, so check your test results for the concentration of these three mineral particles.
- Clay – Very fine, almost microscopic grains. Each grain has a unique shape and size, creating an electrostatic effect that binds them together tightly when wet.
- Silt – Up to 25 times the size of clay, silt particles are not necessarily cohesive. The particles are easily carried by water and wind.
- Sand – Up to 2mm in diameter, 40 times the size of silt particles, grains of sand are gritty and coarse to the touch, the largest of mineral particles.
Every type of soil will have some combination of these particles, determining the value to your plants.
Because clay sticks and clumps so well, it is often rich in nutrients. But plants also need oxygen, and roots will find little space – or pores – to breathe in pure clay. The lack of space also prevents water from draining.
On the opposite end, sand’s porous nature makes nutrient delivery virtually impossible, though drainage of rainfall (if there is such a thing in your all-sand climate) and oxygen will be abundantly available.
Somewhere in the middle will be best for your hemp crop, and that middle is called loam.
Loam is best
Loamy soil runs about 40% each sand and silt, and 20% clay. Your soil sample will no doubt fall somewhere on the gamut of concentrations, qualifying as sandy loam, silty clay loam or something completely different.
Keep in mind that the sandier your soil, the more irrigation and nutrition will be required to compensate for higher drainage. Poor drainage, on the other hand, can lead to fungal conditions like “damping off,” and even crop failure.
Hemp is excellent for use in phytoremediation, the process by which plants absorb nutrients and chemicals from the soil, often where there has been contamination and a “cleanup” of the soil in order. Think Chernobyl, for instance.
This is excellent news for hemp growers with wonderfully rich and balanced soil. Everyone else should be aware that their hemp plants will hungrily absorb both the good and the bad from the earth, and if you’re growing for high-dollar CBD, proper nutrition is essential.
Your soil test will show your pH levels, which should be between about 6 and 7.5. This is mostly in the neutral range favored by alfalfa, sugar beets, and even cotton, wheat, soybeans and corn.
Lower pH (greater levels of acidity) is generally achieved with nitrogen from various fertilizers, though rainfall can contribute as well. This is also why clovers, soybeans and alfalfa are used in rotation.
Though many farmers fertilize, nitrogen from fertilizer is often underutilized by the plants. Leftover nitrogen in the soil creates several negative environmental impacts and amounts to wasted money and effort on the part of the farmer.
To increase the efficiency of your fertilizer, consider using liming materials like calcitic limestone or dolomitic limestone. This could be especially useful in highly alkaline soil regions like the southwestern United States, where water is at a premium, and well-driven irrigation may contain high levels of calcium or bicarbonates. Sulfur may also be effective on alkaline soils.
Calcium is necessary for strengthening plant structure and defending against disease, but too much calcium can be toxic. Calcium toxicity is best observed if manganese, potassium and magnesium are low.
Hemp relies on chlorophyll to convert sunlight into energy, and the chlorophyll molecules rely on magnesium. Sulfur helps distribute chlorophyll, and again, increases the efficiency of nitrogen and phosphorous.
Your soil needs plenty of nitrogen, potassium and phosphorous. Secondary nutrients like magnesium, calcium and sulfur should be low, overall. Every situation is different, and you know your land best, so when analyzing your soil results, get specific advice from a professional on how to supplement your fields, whether it be nitrogen or potash inputs, or something else.
Let’s establish something right away. Hemp cultivation is becoming increasingly competitive, and that means organic farming will be preferred, if not expected by future buyers. And remember, hemp draws toxins from the soil like a straw in a cold glass of lemonade. This means that toxic soil is almost certain to groom a toxic crop.
IPM’s solutions for cannabis pest management are still in progress, as you might expect. Years more study will reveal the real threats to your crop and the economic loss potential they bring.
All that being said, corn earworms, hemp russet mites and spider mites seem to be the biggest enemies to US-based hemp farmers. Prevention is key.
This is just a starting point for examining how you will prepare your land for your hemp crop. It’s not as easy as some have said, but with solid experience on your side, you can give yourself a big head start.