Soil Health Series - Building Humus in our Farming Systems
- 20 January 2016
Soil Health Series
Over the next few weeks we will be posting an article about the pillars of healthy soils and crops and the foundation of food production in modern agriculture. Each area is as important as the other and while we often focus on one or two if these pillars (often Mineral Fertilisers and Soil Structure) we neglect the others which have the result of degrading our soils and restricting performance.
- Building Humus
- Soil Microbes
- Soil Structure
- Mineral Fertilisers
Agriculture and Agricultural productivity has grown at a phenomenal rate over the past. Crop yields have and continue to soar. Productivity in terms of live weights and milk production have increased significantly. Improved management, plants and genetic selection have played a part but they are only part of the reason for this success. The widespread adoption of fertilisers and the management of these tools has been a huge factor in lifting yields to where they are today.
While this has been very positive it does not come without its drawbacks, in fact the opportunity costs is huge. For every one part of N that a plant absorbs as nitrate, twenty to thirty parts of carbon are needed to complete the assimilation. Large and continuous applications of nitrogenous fertilisers like urea, MAP, DAP, ammonium nitrate, and anhydrous ammonia have resulted in the loss of a huge amount of the earth’s soil carbon reserves. This shows the huge speed at which we are burning through humus. This deficit, if left untreated, will become the single biggest issue facing farmers in the later part of the 21st century and on. It will also be the largest limiting factor in further agricultural production
What is Humus
Humus is dark, organic material that forms in soil when plant and animal matter decays. Put simply Humus is the biologically active or living fraction of soil carbon. Humus can be regarded as the glue that holds soil together. It acts as a sponge storing moisture and nutrient releasing both to plants effectively and efficiently. Humus has many benefits one of the most important is that Humus holds its own weight in water. Humus has huge water holding capacity - A 1 % increase in organic matter per ha results in 170000L of water that can be stored in the soil that couldn’t previously. That fact alone must resonate with farmers. In addition humus:
- Improves nutritional value of our food
- Holds all minerals and is a home for the microbes
- Stores nitrate nitrogen stopping it from leaching
- Increases the soils cation exchange capacity
- Is a bio filter protecting our environment
How you can build more Humus
Adding organic matter to your farming system is the foundation of building humus as this is the material that is decomposed by the soil microbes to form this live giving substance. All farmers add organic matter to their system in the form of crop residues and grazing animals leaving behind a blanket of nutrient-rich waste in the form of dead matter from plants, dead roots, manure etc. Often though there isn’t enough. Other techniques such as topping, and leaving stubble is imperative to increasing the amount of organic matter in the system and therefore the amount of material the microbes have available to turn into humus.
We can also add organic matter through the addition of composts, humates and other products like vermicast. These products can energise the soil biology and feed the soil rather than just feeding the plant.
Increasing microbial diversity in the soil is also very important. This enhances the breakdown of organic matter with both bacteria and fungi playing an important role and biological activity in general creating a healthier soil environment where humus will be produced. In order to get microbial diversity in the soil we can plant mixed pasture swards, use biologically friendly fertilisers or add biology directly through bio-stimulants or other biological inoculants. EM fits into this category and has the effect of adding billions of beneficial microbes including fungi, bacteria and yeasts while also having a stimulatory effect on resident microbes. EM can also help the production of humus through the breakdown of organic matter. This was one of the main reasons for EM’s development in the late 70”sand continues to be one of the hallmarks of the product.