Compost: is it worth it?
Is there a return on investment when it comes to adding compost to soil? Is there a money-back guarantee? Maybe the question should be posed differently: can a farmer afford not to add compost to their soils?
Farming has entered a new paradigm; farmers are farming soil and not crops. With healthy soils, farmers can farm almost any crop. This also leads to being more climate-resilience and will enable even livestock farmers to become more self-reliant in terms of production of fodder and the availability of grazing.
Compost is feeding the soil and not a specific crop. Alan Rosenberg of Lindros Whole Earth Consultants explains that the addition of compost focuses on nourishing the soil. "Compost is humified organic matter and benefits soil in three aspects - mineral, chemical and biological. Adding anything to the soil has a cost but the more real return on investment (ROI) include soils transitioning from unhealthy and infertile to healthy and fertile.'
'This process takes time and often large quantities of compost. Should one not be addressing the development of the soil and only be focused on feeding the plant then the ROI will be affected by the very steep rise in the cost of inputs. ROI cannot only be measured in financial terms."
Compost is used on large scale by commercial farmers and applied at a rate of 30t/ha or 30kg/m². The form in which compost is applied (e.g. planting hole, broadcasted, localised under drippers) is a management decision. It will depend on factors such as the scale of farming, crops and equipment. Bear in mind that compost is not a once-off exercise but rather a response to mimic the way healthy soils should function.
To illustrate: the best time for compost application is in autumn. This is the time when leaves fall and organic matter starts to be assimilated into the soil structure through the three processes of decomposition, humification and mineralization. In this way, nutrients are made available for the plant and microbes and are ready for absorption in spring.
In addition, during these processes, soil aggregates are formed by the addition of organic matter. Aggregates are responsible for soil structure as they form pores which help prevent compaction and improve water holding capacity and aeration.
The use (and growing) of green manure is another aspect that might be more appetising for livestock farmers. Cover crops can be incorporated soon after flowering to add organic matter into the soil. The use of nitrogen-fixing legumes such as lucerne, clover and medics increases the availability of nitrogen in the soil while adding to the nutrient content of a fodder crop.
The application of compost is not advocated for specific crops, advises Alan.
'The motivation should rather be to develop healthy fertile soils.' This takes time and cost but the returns may be seen within three years. However, the keen observer and hands-on farmer might already be able to see benefits in the following season. Visible changes may include less water run-off and soil erosion, higher biodiversity, less moisture loss and improved growth.
The benefits of actions such as investing in healthy soil might not always be immediately measurable on a bank balance but the benefits are far beyond monetary profit and extends into the future of a resilient and living soil.
Alan Rosenberg 082 719 7263 email@example.com
Author Marinda Louw Coetzee