Growing in living organic soil has endless benefits when compared with more conventional methods that require careful and measured applications of synthetic chemical fertilisers in inert growing substrates. Some of these benefits include unparalleled complexity of flavour and aroma, nutrient density and overall superior crop quality, cost savings and environmental sustainability by reusing soil over multiple growing cycles with no-till cultivation principals. A high quality, well constructed living potting soil will have a high CEC (cation exchange capacity, the measure of its ability to hold minerals, nutrients) and water holding abilities which not only reduces the need for fertiliser inputs but also presents a potential solution to harmful nitrate runoff into the environment and wastage of precious water resources. I’m going to address CEC and how it relates to no till gardening for the purpose of this article.
Cation exchange capacity and base saturation
Firman Bear and William Albrecht began researching the cation saturation ratio system in the 1940s and 50s. They discovered that most fertile soils contained nutrients in similar ratios. These highly productive soils had similar physical and chemical properties with thriving microbial populations.
Let’s look at CEC and base saturation and why they are so important to consider in your living organic soils.
Cation exchange capacity is a measurement of how many mineral cations the soil can hold on to. Cations are positively charged nutrient ions consisting of calcium, magnesium, potassium, sodium and trace elements. The higher the soil CEC, the more negative exchange sites are available to hold onto minerals. The aim when building a quality living organic potting soil from a mineral balancing perspective is to fill the soil exchange sites with a ratio of about 70% calcium, 10% magnesium, 4% potassium and 1.5% sodium… leaving the rest for trace elements and exchangeable hydrogen. The higher the CEC, the more forgiving the ratios are and the longer your plants will be able to take up nutrients without having to replace them via topdressing.
When CEC is filled close to the ideal ratios, the soil will have a mineral composition that encourages optimal physical properties to provide an ideal habitat for beneficial soil microbes. This enhances plant microbial interactions which allows efficient nutrient uptake by plants through root and microbial exudates. Both the plant roots and microorganisms can exude hydrogen ions and exchange them for calcium or other cations efficiently. This exchange is what keeps soil pH optimum, at around 6.4. A well constructed living organic potting soil takes all of this into account for maximum crop performance and dense mineral content. The end results are crops that contain superior flavour and aroma from huge secondary metabolite production and nutrition from yields limited only by plant variety and general cultivation practices such as watering technique and environmental conditions.
Our Water Only Soil has a CEC of 33 and a water holding capacity of 64%. The high CEC and high water holding capacity is what enables the soil food web to efficiently exchange nutrients with plants as needed.
No till cultivation to create soil health for the long haul
Many annual crops have high nutrient demands and will extract nutrients, minerals and organic matter from soil over time. Organic matter must be returned to the soil after harvest for the next crop. This can be achieved by keeping a constant mulch layer and sprinkling light amounts of a balanced amendment blend in between crop cycles.
When topdressing, work amendments into the upper inch of your soil and add a layer of the highest quality worm castingsyou can get a hold of. Always mulch with straw to encourage even moisture content. Mulch will also supply constant organic matter. A constant supply of organic matter helps carbon cycling in the soil through increased microbial activity that breaks down minerals into plant available form. The continual addition of mulch will create humus through microbial decomposition. Humus increases the CEC of your soil which improves the capacity to provide for crop requirements as needed. Frequency of application will depend on soil volume and plant age. The smaller the container, the more frequent mineral and humus applications may need to be applied.
No till cultivation is not recommended in container sizes under 50L as the soil food web will not have the space to function effectively. Raised beds with ample soil volume and a constant layer of organic mulch would be enough to stimulate microbial activity. This will ensure constant nutrient cycling for efficient crop production. Small applications of our Regenerate blend in between crop cycles will keep cation and other nutrients at optimum levels. Cover crops are an economic and effective source of organic matter. Planting cover crops in your soil will encourage biological diversity, soil structure, nitrogen fixation and carbon cycling and is a free source of mulch. No till gardening is a highly effective method of maintaining and increasing soil fertility for many years.
Regenerate is a balanced blend of organic amendment meals and mineral rock dusts with a mycorrhizal inoculant. This blend contains gypsum, neem and kelp meals, soft rock phosphate, basalt rock dust, malted barley and mycorrhizae. Its most effective when topped with a layer of worm castings to quickly make the nutrition plant available. Your living organic soil should increase in fertility over time, reducing water and input requirements.
Consider the balance of cations as well as your soil CEC. Applying too many fertiliser inputs can alter this balance and do more harm than good. If managed well, your soil can provide harvests for a lifetime.