Healthy Soil Biology – Giving your trees knives and forks

Probably one of the best ways that a farmer can reduce plant stress, irrigation costs, and fertilizer use, whilst increasing yields is to look after the soil biology.

When crops are grown in soil with optimal biology one can expect increased yield and crop health, and resistance to insects and diseases compared to crops grown in soil where they are heavily dependent on chemical fertilizers and where the biology has been suppressed.

Good soil biology, in particular strong bacterial populations, are required for the extraction of minerals, or the mineralization process, whereby minerals are being made available to the plant. The benefit of this process is mostly not understood or appreciated and should be explained in more detail.

When you have a healthy plant that is photosynthesizing very well, a surplus of sugars and carbohydrates are produced. These surpluses are being transmitted out through the root system as root exudates into the soil profile. These sugars and carbohydrates excreted by the roots then trigger rapid bacterial population growth. Although the bacteria use the root exudates for energy, they require minerals for growth. These required minerals are obtained from the soil by a process known as mineralisation, incorporating it into their own cells. As the bacteria population die off or are absorbed by other soil life, these minerals become available to the plant in forms of amino- and organic acid chelates in the soil profile. These trace mineral chelates are now absorbable to the plants, greatly increasing plant health and its ability to withstand disease and insect attacks. Without the soil biology our plants have very poor absorption ability of minerals from the soils. In short, a healthy soil biology helps the farmer to mine minerals from the soil that would otherwise not have been available for the plant to use. This process, if used optimally, should thus reduce the demand of chemical fertilisers to some extent.

Many would agree that it requires substantially more inputs today to achieve a desired result than what it took years ago for the same result. The reason is that extensive damage has been done to the soil biology through the accumulation of herbicides, fungicides and insecticides in the topsoil layers. This accumulation has greatly reduced the beneficial effects that we get from soil amendments (introduction of minerals). The best way to regenerate the capacity of the soil to respond, would be to replenish the bacterial population in our soils.

Soil fungi plays an equally important role in the soil ecosystem. The need to have appropriate fungal to bacteria biomass ratio in the biology is important. Many of the soils we have today have substantially more bacterial than fungal biomass. The presence of a strong bacterial population creates a conducive environment for fungi, either by creating food sources or stimulating plant development which is favourable for the fungal population.

One of the challenges of our modern agricultural production systems is that in many soils the cultural management practices results in strongly suppressing soil biology. Many of the fertilizers that we use, often referred to as high salt fertilizers, or fertilizers with high electrical conductivity, (which serve as electrolytes), create an environment not conducive to soil biology and actively suppress the formation of bacterial and fungal populations. In recognizing this, and also that we mostly still need to use these fertilizers, we need to answer the question of how we optimise both and balance out the damaging effects.

A surplus of available nutrients can be built up in soils by the functioning of a healthy soil biomass. This can potentially allow the producer to cut fertilizer applications significantly.

In recent years we have seen the development of various analysis allowing the farmer to significantly better understand the specific plant nutrient needs and critical growth phases. One such analysis is plant sap analysis which accurately shows the plant’s available nutrients and also what is actually being translocated and utilised by the plant. This allows the producer to reduce fertilizers and also to be predictive of potential plant stresses looming. The single best feedback loop system to keep the soil biology healthy is by ensuring the plant is photosynthesising optimally to maximise the root exudates. This can be done by having a continual look at the energy available to the plant.

So how do we incorporate or increase biology into the soil? There are various microbial inoculants, soil health products and organic growth stimulants available. The critical key is to be sure that they have the required material in the soil to survive and thrive. Some organisms require a living root system such as mycorrhizal fungi. Mulching and cover cropping is the single largest benefit that we can use to stimulate and keep the soil biology alive that we have in the orchards. Introduction of soil biology towards the end of the season, or closely after harvest, can contribute to the micronutrient accumulation in the soils, adding to soil health early in the season.