By Kason Charles
Soil fertility in an interesting, quite large, however, very necessary conversation. It is understood by different communities in different ways. Nonetheless, I think it is through a clear and inclusive definition we may understand its importance. I believe however, that looking at practices that were encouraged traditionally in Grenada may help us to develop a better structure of soil fertility.
Soil fertility is the soil’s performance, it is the ability of each of its main parts to function optimally; minerals, organic matter, water and air. The fertility of the soil speaks about the soil’s ability to encourage plant and animal productivity together with diversity.
These soils should support adequate water and air quality and foster human health. It is also important to note that the soil should be developing to its production potential instead of moving towards degradation.
But why is soil fertility important? Well, unlike animals, plants do not have a digestive system. Instead, the soil serves as the organ for processing the plants’ food. A fertile soil allows plants to use water and nutrients in a better way giving us higher yield.
Plant – soil fertility- product
Why is soil fertility important?
Well, improvement to soil fertility helps the entire growth process of any plant; it creates balance in the soil – A balanced root function, balanced overall plant composition, balanced nutrients and a balanced ecology. Soil fertility in many instances can be interpreted as Balance.
A fertile soil improves the plant and soil’s ability to interact with each other. To improve this interaction, we have to understand that soil has different dimensions; biological, chemical and physical.
The forces defining soil fertility can be divided into 4 groups:
Soil biology
Organic matter
Inorganic matter
System of planting.
Today, let’s have a conversation about one of those forces that have been neglected as it may be harder to understand yet it stands as a foundation of soil fertility: Soil biology.
What is soil biology?
This actually refers to the communities of microorganisms inhabiting our soils. It is important to understand that agriculture is in fact an ecosystem; it comprises many hands clapping together. Different organisms interact with each other; they share, use and recycle different resources. It is often a disturbance of these “community interactions” that creates an infertile soil.
Soil Biology has gained its importance through its role of maintaining soil fertility, while decreasing the need for agricultural inputs (these inputs are usually pesticides, fertilizer, additional labour) and increasing production volume or crop yield.
“Soil Biology” in our conversation speaks about the microorganisms in the soil and the communities they form. While they are small their impact is not microscopic, someone said that we can find more microorganisms in a handful of fertile soil than people in the planet (there are a lot of people on the planet).
Soil biology & Soil fertility
Just how do these microorganisms affect soil?
How do they improve crop and agricultural production?
What role can these little organisms play in feeding home?
The translators – mineralization
– soil biology has the ability to make mineral nutrients in the soil (Phosphorus, potassium, Iron etc.) that may be trapped by certain soils more available to the plant. Many times the soil may not struggle with having minerals present but instead the plant may have issues “feeding” because these minerals are in a “language” which the plants cannot understand. Soil biology translates these nutrients into forms that our plants can use making full use of nutrients present in the soil.
The tiny workers – Nutrient shuttling
-These tiny little workers can play an even more direct role in plant “feeding”; they have the capacity to search for and directly transport water and nutrients into plant roots. Here, the plant does not have to spend energy developing an entire root system to get maximum use of the soil as labourers are provided that act as extended roots. These plants that are provided help with water and nutrient acquisition are usually more competitive.
The recyclers – Nutrient cycling
These microorganisms are also responsible for the regenerative process, of converting plant biomass and manure into soil organic matter – a soil like construct that encourages microorganism life and builds several other qualitative features of the soil (a topic of a future conversation). If this decomposition doesn’t happen, many of those nutrients trapped in plant matter is instead scattered in the air.
The construction workers – soil particle & colloid adhesion
As if these tiny organisms were not playing a big enough role, they also play a role in soil construction. Soil biology or soil microflora are have the capacity to excrete substances that act as “glue”; holding the soil structure together. This allows the right soil building complex to remain in the complex of the soil facilitating a more “sponge-like” structure.
This improved structural construction gives way to several functions of the soil:
– You know those “heavy” soils that are really difficult to work when dry. Well, another function of this structural construction is that it reduces the possibility of the soil being compact which now not only encourages easy working of the soil, but also encourages germination and allows roots to easily grow through the soil. Another important aspect we cannot overlook is waterlogging -an environment that encourages disease and crop loss. The infiltration element reduces this excess build -up of water on the surface.
– It allows more water infiltration and transportation; as the rain falls naturally, water is absorbed into the soil and stored for plant use. Some soils because of poorer structure are too condense to allow water to flow through and lose the absorption ability. When this happens, the water quickly evaporates from the soil surface making that surface crust. The soil now has a lower water storage ability. Through this happening, plants struggle to grow as there is constantly less water available in the soil and in many cases develop a crust which makes future penetrations even more difficult. This leads to an increasing cycle of soil unproductivity. Greater infiltration and storage ability of water then allows agricultural production to become more resilient in a changing climate
The Immune System – Pathological Protection
The soil has its own way of dealing with disease like damping off, blight and rots.
Nature has allowed for or expects that soil biology and plants to live in a “give and take” or symbiotic relationship. Vaguely, our plants release foods into the soil, microorganisms consume this food and maintain life. As we would, these organisms protect their food source. They release enzymes and antibiotics that would suppress organisms that would harm the plant or disrupt the activities of their “kitchen”.
It is important to understand that each soil has some degree of soil biology that is able to help or harm the plant. What influences the role these organisms play is completely up to the environment. Under certain unfavourable conditions, like waterlogging, poor food availability or through the presence of certain chemicals in the soil (e.g. Glyphosate), the microorganism community in the soil that should be potentially beneficial can be converted to perform destructed behaviours. A clear conversion would be a change of appetite; from feeding on dead plant material to actively attacking our live planted crops.
Here we understand that manipulated properly, soil biology does not only create fertile soils but those that are also disease resistant.
How do we encourage soil biology?
Well, these microorganisms are not very different than we are; they also require food, water, air and shelter, like we would.
Covering the soil. – cover, relay, constant, continuous cropping
Weeds do not grow to make our crop production difficult, or at least we hope not. Naturally or ecologically, weeds serve as protection or a covering from the soil. A fertile soil mimics this function.
The soil biology requires food constantly. With this consideration we understand that the surface of the soil has to be covered with plant material providing microorganisms food (plants excretes food through their roots) throughout the entire year.
This vegetable cover also cools the temperature of the soil making it more “liveable” for microorganisms. Additionally, this plant cover also increases the soil’s ability to absorb rain water deeper into the lower levels of the soil improving storage. Bare soil encourages water to simply stay on the surface and eventually be evaporated back into the atmosphere.
Planting different types of crops. – Diversity, cycling and rotation
One of the largest influences to biological soil fertility is food; through the availability of food, a harmonious balance and population control is maintained between these biological communities. We maintain balance through having a diverse crop profile on a particular piece of land.
Planting diversity or planting different types of crops would be important as each species or type of plant interacts with the soil differently; feeding different conditions and organisms and encourage the activities of a wide range of soil biology through their roots. For this provision of balanced nutrition, it is necessary to cycle different types of plants on a particular area of land or in cases where cycling is not possible, encourage a diverse root network to be present in the soil.
Diversity is a huge marker of soil fertility.
Building a home. – The organic matter conversation
Dead plant matter and animal manure are used as construction material for building the homes in which these microorganisms inhabit. A fertile soil has to encourage the regeneration and presence of organic matter in the soil. Our growing practice should encourage the application and presence of organic matter in the soil.
Measures such as excess tillage which allows too much oxygen into the soil and consequently destroying organic matter should be done through discretionary decisions.
Inputs like inorganic fertilizer application also take a toll on organic matter structures through both biological and chemical destructive measures. Another concern is that the lack discretionary use of inorganic fertilizer is their potential to decrease yield and make the soil more inhospitable in the drier seasons.
Herbicide use warrants a few words in this conversation as it renders plant material (leaves, roots) inaccessible to microorganisms and biological decomposition which facilitates the cycling process of plant material into organic matter. Excess herbicide use has another function as it also has the potential to reduce soil biology up to 80%, and with that, suppress the production of plant supportive hormones (microorganisms make hormones that encourage roots to grow) and enzymes.
Each of these inputs should be done on the basis of weighed pro’s and con’s understanding the lack of sustainability of these practices.
Closing
Although small, soil biology has dominated a very large part in the conversation of soil fertility not only because of their influence on crop production and livestock nutrition, but also due to their capacity to perform further large crucial functions, reducing the need for inputs including pesticide and fertilizer having a huge economic impact on agricultural production.
