Understanding The Soil Food Web

WHAT IS THE SOIL FOOD WEB EXACTLY?

The soil food web refers to the diverse inter-related networks through which nutrients and energy flows among plants, animals, insects, and birds to living organisms within the soil ecosystem. It is called web because the flow of these nutrients are dependent such that an activity at one point can affect the outcome of the other. The diagram at the top shows a typical soil food web.

All these activities in the soil food web provide nutritious support for plant growth, most especially is the source of energy – carbon. Carbon is needed by almost all life forms and in the soil, the food web represent a vital system through which carbon is transferred from one source to another. The soil food web shown in the diagram above is generic, different soil types can have various inhabiting microorganisms and so different functions.

The soil food web typically starts with the plant. The plant carries out photosynthesis which it uses to generate energy and other chemicals that gets excreted through the roots. Analogous to animals, plants also make wastes mostly in the form of carbohydrates and proteins which depends on energy from photosynthesis. These exudates serve as food to some beneficial bacteria and fungi living within the rhizosphere, a zone in the soil surrounding the plant roots. All these life forms at the rhizosphere depend on the exudates of plants for carbohydrates, proteins, water and mineral content. In the soil food web, the bacteria and fungi get eaten by other higher organisms in the food chain, like the nematodes and protozoa. Progressively, the nematodes and protozoa further gain carbon and other nutrients from bacteria and fungi, any nutrient not needed are excreted as waste back into the rhizosphere which the plants assimilate as nutrients. Plants basically depend on this system for nutrients where the activities of the bacteria, fungi and subsequently nematodes and protozoa generates organic fertilizer for plant growth. Farmers sometimes interfere in this process by applying inorganic fertilizers containing inorganic sources of carbon, nitrogen and other mineral contents.

Conversely in the soil food web, the nematodes and protozoa are eaten up by animals higher in the food chain, mostly the soil arthropods (insects, lobsters, shrimps and spiders). Alongside, they serve as food to the birds, snakes and other animals in search for food.

MAXIMIZING THE BENEFITS OF SOIL FOOD WEB IN FARMING

Having gained understanding of the benefits of soil food web, harnessing and improving the activities of bacteria, fungi, nematodes, protozoa and arthropods will generate more healthy crops for the farmer. One way of achieving this is creating an active soil food web, this ensures nutrients are retained more in the rhizosphere for the plants. Some of the benefits of active soil food web are:

  • Increased soil nutrient availability
  • Increased soil structure from the activities of worms and insects which improves aeration, drainage and water holding in the soils
  • Reduced exposure of the plant roots to diseases and wastes
  • Monitoring of pH according to the prevalent nitrogen available to the plants.

To maximize these benefits, every farmer must follow the alternative forms of nitrogen sources needed by different plants. Also how to enhance bacterial or fungal activities to generate the proper form of nitrogen. For instance, a soil that is inhabited by more nitrifying bacteria will have the pH of the soil above 7, being regulated by the bacteria. This pH is needed for the bacteria to grow and thrive in the soil environment. Nevertheless, when it becomes populated with fungal species, because of their decomposing abilities which generates organic acids, the pH falls below 7. Above a pH of 7, nitrogen compounds present as ammonium are easily converted to nitrates by the nitrogen – fixing bacteria. While below pH of 7, the activities of the bacteria reduces and the ammonium compounds continue as it is. Promptly, it leaves the farmer to understand the preference of plants with either forms of nitrogen and maximizing that to their benefit.

Research studies in the field of agriculture have shown that most vegetables, annuals and grasses prefer their nitrogen sources in the form of nitrate. This is convenient in soils dominated by nitrogen – fixing bacteria. While trees, shrubs and perennial plants prefer their nitrogen sources in the form of ammonium. Therefore, they thrive in fungal dominated soils. Most soil communities are dominated by the bacteria species producing nitrates as the main nitrogen source. Nevertheless, as plant leaves fall and organisms die generating more organic litter to decompose, the community of fungi in the soil increases. Thereby shifting the balance from bacterial populated soil to a fungal populated soil. This phenomenon also initiates a shift on the kind of plant growing on the soil. In this case, the short-lived plants and vegetables diminishes as shrubs and perennial grassland plants begin to dominate the environment. Having this information useful, the farmer or gardener can manipulate these activities to favour the kind of plant needed to be grown on the soil. In the absence of favorable conditions like the increase in organic biomass, the concentration of both bacteria and fungi stay balanced in the soil.

Another essential method to make the kind of nitrogen plants would need is by observing the life span of the plant. Vegetables and other plants that continue only for a season require nitrate as their preferred nitrogen source. Other plants that will continue for a year or more than a year will prefer ammonium as their nitrogen source. Essentially, a vegetable farmer will till soils that allow more bacteria than fungi to favor the plants.

PLANT PREFERENCE IN MICROBIAL OR FUNGI DOMINANT SOIL

Vegetables like carrots, lettuce and broccoli thrive in soils with a fungi to bacteria ratio ranging from 0.3:1 to 0.8:1

Cannabis, tomatoes, corn and wheat prefer the ratio to be around 0.8:1 to 1:1.

Trees need higher fungi to bacteria ratio. Conifers thrive more in fungal dominated soils with a ratio of 50:1 to 1000:1.

Orchards survive in a fungus to bacteria ratio of 10:1 and 50:1, while maples and oaks will do better in soils with 10:1 or 100:1 fungi to bacteria ratio.

Therefore, leveraging on this knowledge will equip the farmer and gardener with the basic information needed to cultivate healthy plants, trees, and flowers without inorganic fertilizers.

Using BioRhize or MycoRhize to supply your soil with microbes or fungi

Now that you the farmer, is equipped with this information, you can best decide which product best suits your needs for your plant type. Does your plant prefer microbes? Then you’ll want to include our microbial inoculant BioRhize into your feeding regiment. Or does your plant prefer fungi? Then MycoRhize our 12 species fungi blend made with humic acids and kelp is what you’ll need. For cannabis growers, you’ll want to achieve closer to a 1:1 ratio of microbes and fungi. Therefore, if growing cannabis, a combination of MycoRhize and BioRhize will ensure optimal plant performance for maximized yield.