By Craig Madsen
My wife and I traveled to New Zealand and Australia this December. We had a great time seeing some beautiful landscapes and fascinating wildlife. As part of our journey, I spent a week with around 40 farmers and agronomists attending Graeme Sait’s Nutrition Farming Class.
One of my takeaways from the class: Is science asking the right questions? Is it looking for better ways to collaborate with the natural system and address the underlying causes of the problems, or is it merely addressing symptoms that stem from past decisions? One agronomist sitting next to me in the class has been working in the field for over 20 years, and he mentioned that it’s time to rethink our approach to agriculture. Graeme Sait emphasized that it’s time for a wake-up call.
What are the signs telling us about the management of our agricultural lands?
Studies estimate that since the advent of intensive agriculture, U.S. cropland soils have lost 50-70% of their original organic carbon content.
Herbicide-resistant weeds – over 70 species in the United States
Increased disease and insect pressure on crops
Increased use of synthetic fertilizers and pesticides
Water quality issues related to erosion and leaching of synthetic fertilizers
Another issue is the declining nutrient density of our food.
How do we counteract these issues? Healthy plants need and create healthy soil.
Stop treating symptoms – treat the underlying cause. Insects and disease are symptoms of an unhealthy plant – Ask - What does the plant need to be healthy? Not how to kill the pest.
Work with the natural processes versus fighting them.
Understand the impact of your management decisions on soil biology.
Test your soil and plant to understand the chemistry and biology. Remember that biology drives chemistry. A biologically active soil can overcome many issues related to imbalances in chemistry. For example, fungi can break bonds that tie up phosphorous. Fungi and bacteria also produce chitinase, which dissolves chitin, which makes up the bodies of fungi and insects. If allowed to function, the soil biome works to create a balance.
Two of the many critical roles of a farmer are to manage gas exchange (are your soils breathing) and chlorophyll management (how well are plants capturing the free energy of sunlight).
Two key ratios that help a farmer are the Calcium-to-magnesium ratio (you need to know your base saturation levels in your soil) and the fungal-to-bacteria ratio.
Calcium to Magnesium ratio
Adequate calcium levels are necessary to allow the soil to breathe. The most important nutrient for plant and soil health is not nitrogen, phosphorus, potassium, or calcium; it is oxygen. The higher the clay content in the soil, the more calcium is needed to separate the clay so that the soil can breathe. Microbes, like us, need oxygen to survive, and they produce CO2. For sandy soils, a Ca:Mg ratio of 3:1 is ideal, 5:1 for silt soils, and 7:1 for heavy clay soils. This is a target to aim for, not an absolute goal.
Calcium is also essential for the absorption of minerals that affect chlorophyll density and, consequently, the rate of photosynthesis. An insufficient or excessive amount of calcium can lead to deficiencies in other minerals.
Calcium and boron are important in cell wall strength. Together, they form a protective armor-like substance that increases resilience against disease and insects.
Boron levels are essential for calcium absorption.
Do not want to forget about magnesium, as it is the centerpiece of chlorophyll.
Fungal to Bacterial Ratio
Fungi
o Decompose more complex carbon compounds like lignin and cellulose.
o Release acids that break the bonds, making minerals such as phosphorus and zinc accessible to plants.
o Mycorrhizal fungi penetrate plant roots, creating a synergistic relationship with them. The plants release exudates that nourish bacteria and fungi, while the soil’s biology provides minerals, water, and essential compounds for plant growth and protection. Mycorrhizal fungi hyphae can increase the surface area of roots by up to ten times, enhancing access to nutrients like phosphorus, zinc, and iron. They also shield the roots from pathogens, including fungi and insects.
o Fungi release compounds that bind small soil particles into larger aggregates, forming pore spaces for water storage and gas exchange, enabling the soil to breathe.
o The liquid carbon pathway is the quickest method for building organic matter in soils. Plants transfer solar energy from their leaves to nourish soil biology through root exudates. Fungi are essential contributors to the liquid carbon pathway and the long-term storage of carbon in the soil. They create humus, a stable carbon compound, and form aggregates where carbon is safeguarded for microbes. Humus can remain in the soil for 100 to over 1,000 years.
Bacteria
o Break down simple organic compound materials with lower carbon and higher nitrogen levels.
o Packages of nutrients that play a key role in the soil food web – food for protozoa, nematodes
o Form small aggregates
o Produce compounds that can protect the plant, such as antibiotics and growth-promoting compounds
o There are free-living bacteria in the soil that fix nitrogen (another reason for well-aerated soil – 78% of the atmosphere is nitrogen) and others that excrete acids or produce enzymes that make phosphorous, zinc, and iron available.
·Fungal to Bacteria Ratio
o This ratio impacts the types of plants that grow in the soil.
o Bacteria-dominated soil – annuals and plants that low organic matter
o Bacteria-dominated soil – less pore space, more prone to cap over, higher risk of erosion, high carbon plant material does not break down well, nutrients less available
o High fungal component – trees – Where do you go mushroom hunting?
o Native grassland has a fungal-to-bacteria ratio close to 1:1. Cropland should also have a 1:1 ratio.
The Ecdysis Foundation has been conducting soil sampling across the United States. Below is a figure showing the fungal-to-bacteria ratios on one farm, along with the ratios for wheat and averages for cropland in Washington State, as well as the national average. The low fungal-to-bacteria ratio is a strong indicator of how our management affects soil biology. In the next article, we will discuss some options for improving this situation.
