There’s an old adage, “the best fertilizer is a farmer’s footsteps.” Taken simply, this suggests that farmers need to get off their tractors and walk about their fields. At a deeper level, the adage speaks of a time in which the farmer and the land were intimately connected.
Over the past half century, the divide between farmer and soil has grown to such a degree that communication between the two parties is essentially nonexistent. This may be a stretch but the common practice of the annual soil test has, in large part, contributed to the disconnect.
Soil tests have exclusively equated soil fertility with soil nutrient availability. In essence, chemical soil analysis has replaced the farmers’ wisdom of soil qualities (largely physical and biological) that had been their dominant tool in assessing soil fertility.
Moreover, an over-emphasis on chemical soil analysis removed the interpretation of soil fertility from the hands of the farmer into the world of agronomists and specialists.
More recently, an increased interest in soil health and a corresponding lack of faith in ‘N-PK’ soil science has farmers reclaiming their collective knowledge of soil fertility through qualitative assessments, and fostering an intuition that is bridging the gap between farmer and soil.
Reclaiming soil fertility
In organic systems, soil fertility management is a longer-term, more strategic process than in conventional agriculture and therefore more holistic methods of analysis are required. Organic farm-ers need to have a better understanding of the inherent properties of their land (i.e. soil texture; mineralogy; slope, climate, etc.) than conventional producers, because the tools to overcome short-term problems are more restricted in organic systems.
For example, soils prone to compaction will often lead to poor root development and in turn poor nutrient uptake. Conventional producers can turn to soluble fertilizers and remedy the situation relatively quickly. An organic farmer must take a preventative approach to ensure that soil structure is not compromised.
A one-off chemical soil analysis provides a valuable snapshot of nutrient availability at a particular time. The danger from such tests is that many soil specialists convey to farmers a sense of preciseness in mineral concentrations with such urgency that if the elements are not exactly balanced, the crop yield will be compromised. Such a mindset diminishes the complexity and dynamism of the soil ecosystem.
Farmers begin to “micro-manage” the soil and fail to recognize soil’s inherent robustness and resilience. Ideally, soil fertility should be assessed in the field, rather than as a list of properties of an isolated sample. Farmers are reclaiming the definition of soil fertility to something much broader than just nutrient availability. Farmers are adding physical and biological characteristics along with chemical analysis to the equation in determining fertility.
Common and other senses
Moving beyond the chemical soil analysis as the only tool to assess soil fertility is common sense. Interestingly, the complementary analyses use the other senses such as sight, touch and smell. Many producers are using visual soil health kits or qualitative soil health assessment tools (e.g. Ohio Soil Health Card) to monitor their soils regularly. Such monitoring helps build farmers’ knowledge of soils and allows them to compare the effect of different soil management practices on soil health.
Soil tilth – a fancy word for structure and how well the soil can be worked.
A healthy soil should crumble easily, leaving no clods. The soil feels soft and is easily tilled. The soil surface remains open (porous) throughout the growing season. Soils lacking proper structure will have a tendency to crust after tillage and rain, thereby inhibiting seedling emergence. Soils with good structure should show no signs of compaction. Farmers should intermittently pull plants out of their fields from many different areas and observe the root structure. Roots from plants with uninhibited root growth appear white and have fine roots. Compacted soils may have plants with shallow, yellow to greying roots with few, if any, fine roots. Carrots are the best diagnostic vegetable because soil crusting will affect seedling emergence, and the size and shape of the carrot will speak volumes about soil compaction.
For many farmers and gardeners, their nose is all they need.
Soil life – a living soil is a good sign that nutrients are cycling and plants are feeding as needed.
Earthworms provide the easiest tool to visually assess soil health. Soils with plenty of earthworms and their castings suggest that a high level of nutrient cycling is occurring within the soil ecosystem. Micro- and macro-arthropods, such as mites, millipedes and ground beetles, indicate that the soil ecosystem is mature and wellfunctioning.
The rate of decomposition can also be used to assess soil life. Often farmers and gardeners consider the rapid decomposition of organic matter to be a positive sign, however it is actually signalling an imbalance in the microbial population of the soil (i.e. highly bacterial). In contrast, slow decomposition may suggest little or no microbial life. Ideally, residue at various stages of decomposition on the soil surface and in the topsoil suggests good soil life activity.
For many farmers and gardeners their nose is all they need. To many, the smell of the soil is the smell of good soil life. The earthy smell of a good healthy soil is that of the filamentous bacteria called actinomycetes. In contrast, soils that lack smell may have slow biological activity. Soils with a stagnant or swampy smell may suggest anaerobic decomposition and therefore poor soil structure. Many pathogenic bacteria and fungi that cause plant disease are anaerobic organisms.
Soil air and water – half of a healthy soil should be space for air and water.
The beauty of qualitative soil health assessments is that they may force farmers and gardeners to look at the soil throughout the season, especially after intense weather events and management practices. Soil structure can be evaluated by assessing a soil’s ability to store water and allow water to drain. Soils with good drainage are able to warm quickly in the spring and are able to soak up water with little run-off during periods of intense rain, whereas soils with inadequate drainage will pond and puddle even after moderate rains. Interestingly, a well-structured soil will not only drain well, but will also hold water and supply plant roots with it as needed. To determine a soil’s ability to hold water, it is important to observe plants during moderate dry spells; wilting may suggest the soil has poor structure.
Plant vigour – the plant is the ultimate test of the wellness of the soil.
Plant performance is often directly related to nutrient uptake, and, as stated above, nutrient uptake in organic systems is directly related to the structure of the soil. Farmers whose “footsteps” are evident throughout their fields will look at their crops in search of variations in:
- height and population (i.e. drought stress and/or poor seedling emergence),
- colour (uniform, deep-green), and
- appearance (nutrient deficiency symptoms; stressed/stunted).
Visual plant assessment can help organic producers address specific needs of a plant. In organic systems, homogeneity is not desired and site-specific management practices are most appropriate.
Plants, including non-crop plants (also called weeds), provide good signs of what the soil has to offer. Certain plants are consistent with compacted soils or acidic soils or soils with nutrient imbalances.
Healthy soils are in your hands
When farmers use other senses to determine soil health they become part of the soil:plant interface. The soil is constantly sending messages regarding its health and farmers who regularly engage their sense of smell, sight, and touch can respond as required. The idea is not to avoid the traditional chemical soil test, but rather to place greater emphasis on the traditional wisdom of intuitive farmers who are connected to their soil.
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