Soil is ubiquitous but doesn’t get much attention because the most interesting features are out of sight, beneath the surface. Soil provides humans with some of the most important ecosystem services. For a farmer, these would be providing plants with a root habitat which supplies water and nutrients.
When we conducted learner practical’s, most smallholder farmers I had engaged with, did not know off the ability of the soil to regulate water supply. It achieves this by controlling the rate of flow in a landscape, recycling nutrients by facilitating the decomposition of organic matter and making basic elements available for the next crop.
Furthermore, what is uncommonly known by smallholder farmers is that soils are a habitat for a range of organisms that can markedly impact plant production e.g., the symbiotic relationship formed by legumes with nitrogen fixing soil bacteria.
After choosing a region with a specific climate, which soil to sow is the next big choice a producer must make. The soil is a complex mixture of mineral particles, gases, water and organic matter. These elements are continuously interacting to, over time, create soil conditions which are unique to a location. In a natural ecosystem, these climatic and soil conditions would support certain plant types unique to the region. Luckily the physical, chemical and biological components of soil can be manipulated by a producer to suit their desired crop type.
In general soils that support high yielding crops have certain characteristics in common. These fertile soils are: deep, allowing a bigger area for roots to get water and nutrients; have loamy texture that allows for easy movement of gas, water and beneficial organisms; a good amount of organic matter to maintain microbial life and soil structure; pH levels which keep all plant nutrients at optimal availability and enough clay particles to hold onto nutrients and water. The soil must be strategically manipulated to achieve its optimal fertility. But because of the wide range of interacting factors each soil requires a unique management approach to creating ideal soil conditions.
To aid in choosing a fertile soil a survey must be done by a soil scientist to classify soils according to their characteristics. Maps are then designed to illustrate the yield potential of the various soils found on the site. Any soil factors which will limit plant growth are highlighted and recommendations made on how to ameliorate them. These soil maps make it easy for the producer to choose the most productive soils for their high value crops.
There are a range of inorganic and organic compounds which can alter the soils chemical state. Furthermore, each soil would require specific types of ploughing operations to create the optimum root-zone conditions. With regular testing and analysis, soil fertility can be maintained by adjusting the application of ameliorants. Overall, the aim is to avoid any shortages or oversupplies of nutrients because both scenarios can affect the quality of the produce.
Improper management of soil results in land degradation and a “non-functioning” soil. It is thus important to understand how the application of water and ameliorants can alter the soils state. For example, applying water high in soluble salts to soils without proper drainage can create brackish soils conditions which are unsuitable for most crop types. Certain fertilisers have an acidifying effect on the soil and the change in pH can makes certain nutrients unavailable for plant uptake, causing shortages.
Hydroponics is a method of growing plants in a nutrient rich solution without using any soil. The method is done in greenhouses, is management intensive and expensive. At this stage, the method is best suited to high value crops at a small scale. To produce enough food to feed the growing population, soil would have to be used as the main resource and managed with sustainability in mind.
Naturally, occurring fertile soil is limited and as more food is required by a growing population, lower potential, marginal lands will need to be used to produce food. Applying the principles of soil fertility can enable production of high-quality crops while maintaining or enhancing the ecosystem services soils provide.
Lucian Fredericks is a feature writer for Mzansi Agriculture Talk. His key interests are nutrient dynamics in agricultural ecosystems and developing sustainable management practices that protect the natural environment. He is intrigued by plants and their ability to provide nutrition to all living animals. He studied agricultural sciences where he completed his B.Sc. in Soil Science and Agrometeorology (2015) and B.Sc. Honours in Soil Science (2016) at the University of the Free State (UFS).