Food Plot Soil Health
Today I would like to write about soil health. Everyone knows we have to lime and fertilize our food plots, but why? When? How much? How often?
Once you have your food plot soil corrected in terms of pH and fertility and plant and animal communities working correctly in the soil, fertilizer and herbicide will not be necessary. Avoid using fertilizers and herbicides if possible. It is better not to mess with the soil structure and the biosphere with tillage and applications of soil amendments.
Ok, I’m about to get all scientific on you, so buckle up. If you are serious about growing big deer, you need healthy food plots, if you want healthy food plots, you need healthy soil.
Everyone if familiar with nutrients in fertilizer, Nitrogen, Phosphorous and Potassium. But plants use 90 molecules in the soil. We know about Macronutrients but not so much about the Micronutrients. Micros are also important for plant growth and vigor.
What is soil, anyway? Soil is the earth’s rock that has been weathered by the elements and lower life forms over the past 100 million years, more or less. It also consists of plant and animal matter (organic material,) air and water. Soil has layers or Profiles and Horizons which is not important here, since what we are concerned with is the O and A Horizon, or surface. This is where the humus is located, and the root zone of forbs. Soil also has a texture, which is the percentage of clay, silt and sand – which generally refers to the particle size. Clay particles are extremely small and flat in form and can hold a lot of molecules of nutrient molecules, gas molecules and water molecules on their surface. Soil texture is categorized by its relative content of sand, silt, clay particles and its humus content.
Good soil for food plots has 10% organic matter and rest should be an even volume of silt, sand, and clay.
Soil also has a structure, or the shape it takes when undisturbed. The way it clumps together and forms natural shapes and aggregates together determines its’ structure. Don’t worry too much about that either, just be aware of it since your soil classification you see on a soils map is influenced by this.
Your soil type may be an Inseptisol with a channery, silt loam texture. In English, this means it is relatively young and is stony and leans toward silt sized particles.
Ok, Back to Nutrients in Food Plots.
Nitrogen – N is part of every amino acid molecule which are the building blocks of proteins, which are the molecules of many functions is organisms, including new cells for growth and repair and chemicals that regulate the functions and transfer information within the organism.
Phosphorous – P is used in the many biochemical reactions in plants including that which converts light to energy in photosynthesis. It is the P in ATP, the energy unit in a cell and it is part of RNA and DNA molecules. It is needed throughout the growth of a plant and increases when seeds are being produced as it takes a lot of energy and cell multiplication to do this.
Potassium – K is involved in numerous plant processes: acts as a catalyst in many chemical reactions. K regulates the opening and closing of stomates, the pores on a leaf that allows transpiration, and respiration of plants. Potassium causes the opening of pores to help cool the plant and let in atmospheric oxygen and hydrogen and closes the pores during drought stress to conserve water. K is involved with just about everything a plant does. It regulates the flow of energy produced by photosynthesis throughout the plant and is involved with the creation of ATP, the energy molecule within the cells.
Potassium and Magnesium need to be in proper balance. If you put too much of K fertilizer on it can be harmful to plants and also the animals that eat the plants.
Other important nutrients are Calcium Magnesium and Sulfer. Calcium and magnesium are important to soil pH and are derieved from rock decay. Sulfer can be from decaying organic matter. Micronutrients that are only needed in very small amounts are numerous and are the metals like iron, boron, zinc, etc.
Macronutrients are less available in soil with low pH and micronutrients tend to be less available in soil with high pH. A pH of 6.5 is a happy medium where the greatest availability of macronutrients and micronutrients are available at once. This is due to environmental conditions preferred by fungi and bacteria which make a lot of the nutrients available to the plants through their activities. Fungi like it acid and bacteria like it neutral or alkaline. Different plants like different pH levels, depending on the microorganisms that help it function.
What is PH
PH is a measure of how much Hydrogen cations (positively charged molecules) are in solution. If H ions are in solution, negatively charged Hydroxyl ions (OH ions) are held on the exchange sites of soil particles. OH ions take up spots that could be held, or exchanged with nutrient cations. Which brings us to the Cation Exchange Capacity of the soil. The higher the CEC is, the more nutrient cations that can be held by the soil and in turn taken up by the plant roots. OH ions are tightly held to the soil particles, not allowing nutrient cations to attach to the soil. So that’s why low pH soil is a bad thing. Nutrients cannot move throughout the soil and work their way into plant roots.
What Does pH Correction Do?
PH is easily corrected with lime and if Magnesium is also low, you can put on limestone that is high in magnesium. Use pulverized limestone to get the quickest change in acidity. The reason limestone changes acidity is that it is made of Calcium with a carbon/oxygen group, making it calcium carbonate.
If there is hydrogen in solution (acidity) calcium carbonate reacts with it and makes water and carbon dioxide and the calcium molecules are available to the plant. Ca is a cation that is attracted to soil particles and is easily exchanged with other nutrient molecules.
Soil as a Living Organism
Now, I told you all that to get to this: There is a living community, a biosphere in the soil that consists of bacteria, fungi, worms, bugs like arthropods. There are by far more species you can’t see than what you can. These life forms have there own ecosystem, with predators and prey, symbiotic relationships with plant roots, beneficial and harmful to plants, all in balance with each other. If the microbiology of the soil is intact, the soil takes care of itself.
The crop takes up nutrients with the help of mycorrhizal fungi and rhizobium bacteria that form symbiotic relationships with plant roots. The crop dies, decomposes or is eaten by animals and is eliminated as manure and deposited back into the soil. Decomposers like nematodes (worms) and other tiny bugs, bacteria and fungi work on the plant material, breaking it down to create the organic material or Humus in the O layer of soil. When this ecosystem is in balance, it regulates itself. You no longer need to put lime and fertilizer on your plot.
Why Fertilizer is Bad for Your Soil and not Necessary
Fertilizer, especially Nitrogen, is the number one culprit of causing soil pH to go down. Constantly adding N to soil causes acidity. Nitrogen and Phosphate also leaches out of the soil and causes terrible pollution of coastal waters. The only reason farmers have to add nutrients is because they harvest the nutrients in the form of corn, wheat, soybeans or whatever and take it off site. The molecules tied up in the crop are gone and no longer cycle back into the soil. Fertilizer and herbicides cause pollution, acidity and are expensive. We should avoid them if we can.
How Legumes Extract Nitrogen from the Air
The most important symbiotic relationships are the bacteria that form nitrogen-fixing nodules on the roots of legumes and also fix nitrogen without nodules on some grain plants. Everybody knows you need legumes to get N from the air. But how does this work? Atmospheric N is useless to plants because it is a tightly bound two-N molecule. A plant has to have a more loosely-bound molecule like Amonium, a Nitrogen with a hydroxide. That is what nitrogen fixation is.
How do Bacteria Fix N
How it works is this: A plant root, lets say a soybean plant, sends out a chemical signal. Just as a flower sends out an odor and color to attract pollinators, this signal attracts nitrogen-fixing bacteria. Bacteria in turn send other signals back to the root. The root then starts to grow around the bacteria – absorbing it into itself. The bacteria looses its cell wall and essentially becomes part of the root and enlarges. It feeds off the carbohydrates created by the plant from photosynthesis and, in turn, takes atmospheric N and makes it available to the plant by forming amonium and nitrates (NO3.)
There are also very important fungal nets that live on plant roots that help the plants obtain nutrients, oxygen and water.
There is a nutrient cycle and billions of tiny life forms with their own life cycles and relationships. When all is in balance. The soil is a healthy, living organism that is productive and will grow food forever.
No-till planting and keeping much of the plant material on the land has become popular in farming. Before heavy use of fertilizer, farmers had to rotate crops to add nitrogen back into the soil and to disrupt plant diseases. Disease is a symptom of an over-crowded monoculture. Too many of one plant or animal in one place – what do you get? With people it is plague, with beans it could be rust, with deer it could be EHD and CWD.
Correcting the System
If you have poor soils, you need to add lime, organic material and possibly some fertilizer. But once you have a good system in place, you should have to do very little in terms of soil amendments. Use no-till techniques, add manure, grow different plants to add variety, rotate your crops. Once in a while, you may want to do some herbicide applications, but not too often. And add a little fertilizer, but stay away from Nitrogen if you can. Legumes don’t need it. And always use a soil test before you ever add soil amendments.
You now know more about food plots and soil in food plots than 99% of food plotters out their. Happy food plotting!