The old adage 'give a man a inch and he'll take a mile' is never truer than when dealing with Mother Nature. Since humans first began cultivation, weeds and diseases have been the Achilles heel in grain production. But what we have failed to realize is that weeds and diseases are just one of many ways Mother Nature adds diversity to the system.
Weeds and diseases are signs that the farming system does not contain sufficient diversity. Historically, we have treated these antagonists using tillage and pesticides instead of addressing the real problem: why do we have specific weed problems or disease incidents? The advancement of new pesticides have lulled many producers into thinking that previously valued agronomic skills are less important than picking a good pesticide.
Inputs such as fertilizers and pesticides should not be used as tools designed to stop natural processes, but rather as a way to initiate natural cycles. This is what is referred to as a systems approach. A crop or two is added to the rotation to provide the diversity that is lacking from the system. Nutrients are used to replace the nutrients that are exported from the system, but they must be applied to provide a competitive advantage to the crop intended for harvest.
For the farming system to be profitable, as well as sustainable, the system must be designed such that natural cycles and principles become an ally rather than an enemy. If we grow crops placing a heavy emphasis on creating a healthy and biologically active soil ecology, we can attain a high level of pest control. At the Lethbridge Research Centre, Dr. Jill Clapperton found as many as 300 earthworms per square meter under no tillage compared with zero under conventional tillage. In the same experiment, significantly lower incidences of common root rot in the no-till situation illustrates the long-term benefit of maintaining the soil habitat.
The presence of earthworms in the soil is often considered a positive indicator of soil quality and productivity. Numerous researchers have suggested that earthworms play an important role in the breakdown of organic matter and nitrogen cycling in reduced tillage systems. Earthworms prefer plant material that has been colonized by fungi and bacteria which can lead to reduced incidents of fungal diseases like take all and pythium root rot.
Many of the soil organisms that are rapid colonizers of organic matter are antagonistic to disease-causing organisms. As well, the residue from some crops inhibit the growth of other plants either directly or indirectly from the byproducts produced from the microbial decay of the residues (allelopathy). Fall rye, mustard, oats, black medic, hairy vetch, sunflower, oil seed hemp, and sweet clover are all reported to inhibit the growth of weeds. There is also research showing that residues from oats can inhibit the germination of some disease causing fungal spores like Sclerotina.
The work done by earthworms and other soil fauna provide a biological tillage of the soil profile. These soil animals feed on the organic matter, fungi, bacteria, and each other to recycle all the carbon, nitrogen, phosphorus, sulphur and other nutrients in the soil organic matter into mineral forms that can be used by plants. At the same time, the root exudates, hyphae of the fungi and the secretions and waste products of the bacteria act as binding agents to hold small soil particles and organic matter together to improve soil structure. This makes for a better soil habitat which, in turn, attracts more soil animals, which further increases the amount of nutrient cycling.
Farming practices that include diversified crop rotations, increased use of legumes, cover crops, green manures, and composts not only build up soil organic matter but also increase the biodiversity of soil organisms. One of the basic principles in developing a proper rotation is that the diversity must be appropriate for each land parcel. Some land is owned, some is rented, and each parcel has its own cropping and management history that must be taken into account. However lack of diversity allows an opportunity for weed and disease organisms to build to harmful levels.
Dwayne Beck from the Dakota Lakes Research Farm emphasizes there must be proper water utilization intensity. This means that crop water use must match the water available. Problems with salinity, erosion, and nutrient loss can occur if the intensity is not sufficient. However, if the system is too intense, poor yields due to water stress or stand establishment problems are likely. In either case, improper intensity will result in management problems and less than optimum profitability.
The best systems attempt to mimic native vegetation in water use intensity, and employ as much diversity as required to optimize the system. Every resource on the farm (land, labour, machinery) is managed to optimize its contribution to the operation without overtaxing its capability. Sustainable profitability must be the primary goal in order to assure that conservation continues long-term.
Remember, Mother Nature is an Opportunist. If you have a problem (weed and/or disease), you have provided the opportunity for that problem somewhere in your system.
Henry Ford once said:
"The land supports life. Industry helps man to make the land support him. When Industry ceases to do that and supplants the land, the land is forgotten and man turns to the machine for sustenance, we find that we do not live off the work of our hands but off the fruits of the land".
Leopold (1933):
"A harmonious relation to the land is more intricate and of more consequence to civilization than the historians seem to realize. Civilization is not, as they often assume, the enslavement of a stable and constant earth. It is a state of mutual and interdependent cooperation between human beings, animals, plants and soils, which may be disrupted at any moment by the failure of any of them. Land spoliation has evicted nations and can do it again. As long as six virgin continents awaited the plow, this was perhaps no tragic matter….".
William Bryant Logan (1995):
"A soil is not a pile of dirt. It is a transformer, a body that organizes raw materials into tissues. These are the tissues that become the mother to all organic life."