Until recently, the sustainability of a greenhouse plant nutrition program wasn’t really much of an issue.
“Looking back 10 or 15 years, I think growers related the concept of ‘sustainable’ to ‘organic.’ At the time, organic production was so difficult and had so many regulations, no one really wanted any part of it,” says Janet Curry, National Key Accounts Manager for Daniels Plant Food.
But that’s no longer the case.
Whether it’s pressure from big retail customers, pull-through interest from consumers, a better understanding of sustainable practices, or just a desire to “do something for the environment,” organic and sustainable plant nutrition programs seem to be on the rise in greenhouses across the country.
“With better education and some new products coming on the market, growers have gradually realized it’s attainable. I think we now see growers really looking for ways to grow sustainably,” Curry says.
Organics Don’t Work The Same Way
As organic fertilizers and practices have improved, many growers have been able to achieve the same quality results as they do in conventional nutrition programs. But while the results may be similar, it’s critical to understand that the process to achieve them may be completely different than what you’re used to.
“There are many different organic fertilizers on the market, and they simply don’t respond in the same way inorganic fertilizers do. There’s a lot more variability in how an individual fertilizer is going to impact the nutrient management program for different growers,” Williams says. “We don’t really have definitive standards to manage nutrition when they are used.”
With an inorganic fertilizer, effects on the plant are generally predictable and consistent. “For example, with a traditional fertilizer, growers know what’s going to happen to the root pH, and what the salt level of the root medium should be for different crops,” Williams says.
Organic fertilizers, on the other hand, often rely on microbial activity to break down organic compounds and make the nutrients available for plant uptake. Different organic fertilizers have different rates of mineral breakdown and nutrient availability depending on various external factors, such as temperature.
There are often extra salts and other “stuff” in organic fertilizers in addition to the nutrients, Williams cautions. Those salts can build up over time and become a problem.
Another issue to keep in mind is that specific products sometimes have counterintuitive effects on the crop.
“Daniels’ organic product works almost opposite of everything we learned in school about synthetic fertilizers,” Curry says. “With synthetics, if you want your crop not to stretch in cool, cloudy conditions, you cut the feed back. With Daniels, you can actually increase that feed rate and the plant will stay compact.”
Adjust Your System
While the idea of trying to manage through these challenges might seem daunting, Williams says sustainable fertilizers can fit relatively smoothly into a nutrition program–once you understand how they work in your specific production system.
“I recommend starting small,” Williams says. “Keep everything else the same, but change the fertilizer for the plants on one bench and monitor the nutrition, the pH and the EC. It takes a lot of time and effort, but do a weekly or every-two-week check of the pH and EC of the crop to see how the new fertilizer is changing those factors.”
The baseline for comparisons is your experience with traditional fertilizer programs. By monitoring EC, for example, you’ll be able to see if the organic fertilizer is causing a salt build up in comparison to the fertilizer your more familiar with.
But even these proven measurement benchmarks require some adjustment when moving to a sustainable fertilizer program.
“It’s a little more difficult to use pH and EC as decision-making tools with organic fertilizers because we’re not as sure about what the fertilizer is going to do. With inorganics, we have the ability to make whatever combination we want. It just takes a little more care to figure out how these organic formulations, which don’t tend to be as balanced as inorganic fertilizers,” Williams says. “But if you start collecting that information over time, you’re going to know what it will do in your production system.”