How we feed our plants, much like how we feed our bodies, has a direct correlation to the health and vigor of our lovely ladies. Surprisingly, despite new advancements when it comes to plant care and how we feed our plants, most of us don’t really understand nutrients. Beyond knowing what brand you like to run or your favored N-P-K bloom booster, information regarding soil water tension and ideal EC for nutrient uptake is typically glossed over. This lack of knowledge has kept many growers from ascending to the professional level. Let’s talk about why.
Though ‘conventional agriculture’ references agrochemical fertilization and production, this science has really only developed over the past 60 to 70 years, and marketing and branding has developed alongside these scientific advancements. Most growers go straight to household names, as they’re easily accessible. Not knowing how these products differ from one another isn’t necessarily your fault; manufacturers don’t want you to recognize the simplicity of these products, because you could probably easily make them yourself. Before you can start making your own nutes, however, you need to make the most of the ones you have.
Let’s revisit the chapter of the grow book we all skimmed over—soil tension and EC. While these measurements may not be necessary when running a small home garden, they can still be the difference between 1.5lbs a harvest and 2.25lbs. The reason? Consistency. By maintaining an even soil tension and EC, the plants are able to grow at their maximum rate non-stop—the entire rationale behind hydroponics. Let’s look at why this is:
An EC reading is a measurement of electrical conductivity present in your nutrient mixture. Basically, how dense your nutrient to water ratio is, based on the conductivity of the fertilizer salts you’ve added. You have likely seen EC and ppm used interchangeably. This is because ppm (parts per million) is a conversion of EC to an estimated ppm. EC is better used as your primary measurement, as different meters utilize different scales to estimate the ppm’s, thereby making it difficult to regulate consistency over time, locations or devices.
EC measurements will help keep your nutrient availability within the optimum range. Ideally, you will stay within a window: never too low, never too high. For instance, if you want to deliver a full-strength nutrient solution with an EC of 2.0 – 3.0, typical directions are to feed plants all at once and water the rest of the week. Nutrient uptake in the beginning of the week will be low and slowly increase as the EC lowers day after day, and with the addition of water. By the end of the week, the EC and nutrient uptake are both very low, but water absorption is high. An alternative to this method is to feed a lower EC nutrient blend daily, maintaining uptake in the ideal range. Many growers have found they are able to ultimately feed heavier this way, though attention to the run-off EC is paramount. A high EC will increase the uptake of nutrients, but too high an EC leads to excessive uptake that plants respond to with lower yields and dry weights—not to mention retaining excessive amounts of Nitrogen.
Soil water tension
If you feed plants, they’ll take the nutrients they’re given…right? Wrong! Cannabis plants feed hard, but every plant operates in certain ideal conditions. Beyond EC, the amount of water available for the plant to uptake is key. Overwatering can be just as damaging as underwatering, and that’s because of an occurrence known as soil water tension, or SWT.
Soil water tension is a measurement of the force necessary for plant roots to extract water from the soil. It’s not as simple as moisture content, however. The soil tension will vary based on your medium. For example, 20% water content in a sandy soil gives you a tension of roughly five cbar, excellent for water and nutrient uptake, whereas 20% water content in a clay soil could result in a tension as much as 12 times greater. At 50-60 cbar, you’ve severely limited the growth of your plants and likely killed some of them, depending on the type of plant. By monitoring your EC and SWT in unison you can maximize feeding times and strengths, ultimately maximizing yields.
Regardless of how long you’ve been growing, it’s never time to stop learning. The industrial agricultural industry has had a recent and intensive push for organics and sustainability, propelling the industry forward. Looking at the multi-billion-dollar agriculture industry and its business decisions, both right and wrong, can help us continue to steer the direction of cannabis. From small home gardens to large operations, we have a responsibility to monitor how we grow our favorite plant, and irresponsible nutrient use is a core cause of environmental distress. So hey, why notgrow more weed for less and help the environment while you’re at it? A little extra nutrient measuring can make both a reality!