Jocelyn Durston and Chris Kasza
Jocelyn Durston and Chris Kasza Organic Farmers from Maple Ridge.
To most consumers, organic means the absence of chemicals in, or on, the food they buy. The more astute may even refer to integrated pest management or the avoidance of GMOs. This public attention on the “green and growing” aspect of organic ignores the equally important role of “brown and fertile.”
At the 2013 Pacific Agriculture Show, three experts discussed the careful balance of soil management. The soil itself, fertility inputs and alternate compost sources are part of creating the best base possible for organic growing.
“There’s nothing new under the sun (in soil management),” says DeLisa Lewis, from the Faculty of Land and Food Systems with the University of BC. “But there are some core practices we all need to continually discuss. Soil and land stewardship – they’ve been with us a very long time.”
While the modern versions of these practices are much more scientific than their ancestors, what soil needs is still the same. Lewis references the Cornell Soil Health Manual, 2009, which outlines physical, biological and chemical soil concerns along with options for resolution. “[The Cornell manual] is essentially a trouble shooting guide.”
At its core, soil management consists of five activities: soil tillage – reduce the amount of soil movement and ensure better timing, crop rotation – improve timing, cover crops – an age-old practice, but more trial is needed, adding organic amendments, adding approved mineral amendments.
Crop rotation and cover crops are a focus for Lewis who studied cereal grain crop rotation and under-seeding cover-crop trials in Delta and Ladner potato fields from 2008 to 2011.
One approach, she says, was to “alleviate the phosphorous inputs and provide a saleable [rotation] crop. We found red clover to be the best of the three cultivars we tried [for cover crops].”
Stephen Eng of Agrium Advanced Technologies triggers laughter with his opening: “How many of you have your nutrient management under control?”
His joke brings home the point that soil nutrient management is a moving target. His goal is to “help you make the rights choices at the right time.”
Eng notes there are 17 essential primary, secondary and micronutrients. “Three come from the air and water,” he explains. “Those other 14 have to come from the soil somehow – either within the soil or by adding it.”
A soil pH of between 6.0 and 8.0 is where the majority of nutrients are available to plants. To correct levels, Eng suggests lime to raise, or sulphur to lower, the pH.
While pH impacts the availability of nutrients soil type influences the ability to hold nutrients. A clay based soil will hold nutrients more efficiently than a sandy based soil. Understanding what to add comes down to Eng’s commonsense formula: Plant needs minus (what is available) equals (what you add)
As to what’s allowed, Eng explains each organic certification body decides. “I can only say…whether or not the product has been registered with Organic Materials Review Institute (OMRI).”
Generally acceptable primary nutrient sources include animal and poultry manures, blood and bone meals, compost, fish emulsions and hydrolyzed fish among others. Dolomite lime, oyster shell meal and gypsum were sources for calcium, but magnesium sources were few: dolomite lime, langbeinite (SPM) and Epsom salts. The sources of sulphur were the same as magnesium except for the addition of elemental sulphur.
“For micronutrients (see chart previous page) for organic growers, kelp is the best source,” he adds.
For natural fertilizers permitted in organic production Eng notes: manures, compost, soybean meal, corn gluten meal, blood meal, liquid fish plant food, liquid fish fertilizers and some blended source options. Ready-for-use, commercial fertilizers Sustane, Guaranteed Organics 1-0-1 and Kelpgrow are OMRI registered and are accepted by most organic certification standards.
“Cold, wet soils release P and K very slowly, even when soil tests indicate adequate amounts,” Eng says, touching on the topic of phosphates. The ideal soil temperature for optimum phosphate release is above 22º C (72° F) and he recommends soil temperature checks in the spring.
Before concluding, Eng touches on compost. “Compost provides uniform humus that can be used to amend soils and provide fertility.”
He recommended growers make their own compost due to the ability to control the process and says it is “buyer beware” when it comes to purchasing compost.
“Few suppliers of manure based fertilizers actually manufacture compost,” he notes. “Fewer still provide any proof of temperature monitoring or continuous safety testing.”
Tom Forge of the Pacific Agri-Food Research Centre agrees on-farm compost is the best resource, but explains many organic farms can benefit from “off-farm” compost as well, which is permitted in the Organic Production Systems – General Principles and Management Standards.
The primary concern about off-farm compost is contaminants that could threaten certification. A secondary concern is that compost could affect crops.
“There are a lot of concerns with fecal bacteria,” Forge says. “Has the composting process been significant enough to eliminate fecal bacteria?”
With the growing volume of residential yard and food waste composts, growers have a new option. The Metro Vancouver region alone produces 628,000 tonnes of organic waste each year and herbicide use is no longer an issue due to aggressive non-herbicide positions by most municipalities.
“Use of municipal yard waste and/or food waste compost is ‘safe’ for organic producers – or at least is the lowest risk option for off-farm amendments,” Forge says, adding that greenbin composts comply with National Organic Standards.
Forge adds, “You need to match the compost with the use to achieve optimal benefits. When you get the nutrient info [for offsite compost] make sure it’s on the batch you are getting.”
Understanding soil inputs and management is one that goes unnoticed by most consumers. Growers, however, will reap the rewards of healthy plants by staying on top of information and resources available. ■