In an agricultural context, a fertile soil has many functions. It supports healthy plant growth by cycling nutrients, controlling plant pests biologically, and regulating the water and air supply for plant roots and microbial activity.
These functions are sensitive to soil management practices. Soil is a complex ecosystem that has interrelated physical, chemical, and biological properties. Your continued soil fertility is dependent on the soil management practices on your farm.
10 Ways To Improve And Maintain Your Farm’s Soil Fertility
1. Test your soil
Not just for NPK but for microbial activity and micronutrients. Knowing which biology is present in your soil and its function offers great insight on the nutrient cycling capacities of your soil. Tracking that throughout a harvest and/or a season, can give you valuable information on how to adjust practices and potentially improve soil and crop health.
2. Walk your fields and look for visual clues of soil fertility
Dig a hole in your field, count the earthworms. No earthworms? Your soil fertility is probably low. Look at the color of the soil, is it a rich, dark brown – or grayish dust? Which do you think has more fertility?
Fertile soil smells good. After a spring rain there is a good smell in the air. This smell is attributed to a compound produced by an Actinobacteria. Griseofulvin is produced by microscopic streptomyces. The bacteria releases this gas to attract springtails to help disperse their spores. Turn over a damp log and you’ll see a large number of them “springing” away, they are harmless, and they feed on algae, fungi, decaying organic matter, and pollen.
While you’re looking at your dug hole note how deep the roots have penetrated. If they’re shallow you may have a hardpan layer, especially if you’ve been tilling. That layer of hardpan can be remedied without any more tilling.
3. Get to Know your Weeds
You have some allies in breaking up that hardpan that you may never have thought of before. They are plants that act as “dynamic accumulators” and that you have been calling weeds. Comfrey, stinging nettle, chicory, lamb’s quarters and many more weeds that have long tap roots break up the hardpan, bring up minerals from deep in the soil, and bring fertility to your soil. Nettle and comfrey, especially, are high in mineral content as well as nitrogen. They make excellent additions to a compost heap or can be used as mulches.
The roots of comfrey can grow 8 – 10 feet deep into the soil. You can cut the above ground biomass and put it where you need more fertility. The same is true for stinging nettles and lamb’s quarters. (be sure and wear gloves when working with stinging nettles and cut the aboveground biomass before it goes to seed) Don’t pull up these helpful weeds.
We have a tendency to think of weeds as detrimental to our land but examining the types of weeds on your farm you get an idea of the state of your soil. Weeds are particular about where they’ll grow. Chicory, lamb’s quarters, and purslane all indicate rich soil. (They’re all edible and highly nutritious, too.) Thistle could mean a deficiency in iron and copper. Weeds like a particular pH: plantain and sheep sorrel like an acid soil, whereas goosefoot and chamomile like their soil alkaline.
Weeds are an indicator of the limitations that exist. If you learn how to read your weeds that knowledge will allow you to make better management decisions for better soil fertility.
4. Disturb the soil as little as possible
Every time you till, disc, or even hoe your soil you are disturbing the microbial community. Those microbes are responsible for the fertility of your soil, along with water and air. If you are using a mold board plow, consider discing. If you are tilling at all, consider strip-till, no-till, or ridge-till. They all retain 30% or more of the vegetative matter on the soil surface.
Plowing your fields leaves them vulnerable to both wind and water erosion. It also brings weed seeds to the surface, exposing them to sunlight and allowing them to sprout. Once weeds have sprouted, they emit auxins (powerful growth hormone produced naturally by plants), creating territorial boundaries. When you plant your cash crop a week after tilling, it will never reach its full potential.
The soil food web is made up of microscopic microbes, nematodes, earthworms, arthropods (insects), and other burrowing critters that are all creating humus in the process of living and dying. They act as partners with your plants creating a cycle of fertility. Disturbing the soil when it’s not necessary disrupts the cycle, making space for disease and pests.
5. Rotate Crops
Have you been growing corn and soybeans or peppers and tomatoes on the same fields for a number of years? Have you been encountering more pest and disease problems? It‘s time to add another crop to your rotation. Your friends, the soil microbes, are becoming specialized. When that happens anything unusual in weather patterns, an invading pest, or decrease in a soil nutrient will show up as lower yields and decreased soil fertility. At Iowa State University, Steven Hall conducted a study on the effects of corn/soybean rotations. The study found that corn/soybean rotation by itself saved farmers money on nitrogen fertilizer in the short term, but it led to decreased organic matter in the soil.
"Hall said it may be possible to sustain or increase organic matter by introducing other grains and legumes as well as cover crops, such as rye or oats, into corn and soybean rotations. That way, farmers could retain the benefits of rotating their crops while replacing organic matter." (1)Maintaining optimal levels of soil organic matter for microbial activity helps plants grow to their full potential. It allows microbes to release nutrients in plant soluble form and sandy soil to retain water while clay soil forms aggregates to hold water until the plants need it.
6. Plant Cover Crops
If you leave soil bare Nature will cover it for you, probably with readily available weeds. If you want to increase the fertility of your soil, create a healthy farm ecosystem, and stop erosion from wind and water – cover crops are perfect. There are numerous YouTube videos on cover crops. This video is a little dated but the information is still correct.
Cover crops are a long-term gain. In the short-term you may see no benefits, but after a couple years you will see:
- Less erosion
- Less leaching of nutrients from your soil (your creek down-field will run clear again)
- Improved moisture availability for sandy soils
- Ability to get into the fields earlier on clay soils
- Less irrigation needed
- Reduced infestations by insects, diseases, and weeds
- Habitat for beneficial insects and important pollinators
These are some of the gains. It takes some planning to get the right mix for your particular farm. Start with a small plot on your farm as you fine-tune your system. Might as well start out with the least productive spot. What do you have to lose? And there is so much to gain!
7. Use IPM (Integrated Pest Management)
In other words, use beneficial bugs to take care of bug pests. We are all familiar with ladybugs, they eat aphids and many other bug pests. But there are a vast number of beneficial insects that may already be on your farm. You need to identify them so you don’t destroy them. The more beneficials you have on your farm, the fewer pest insects, the less toxic chemical spraying, and the more microbial activity in your soil. IPM is directly related to soil fertility because every time you spray a pesticide it eventually gets into your soil and destroys microorganisms.
Pesticides are not selective. In your attempt to rid your fields of a particular pest you also take out all the beneficial insects, many that are predators of that very pest you sprayed for. Pesticides also kill many pollinators.
According to the University of Georgia Honey Bee Program, "There are several ways honey bees can be killed by insecticides. One is direct contact of the insecticide on the bee while it is foraging in the field. The bee immediately dies and does not return to the hive. In this case, the queen, brood, and nurse bees are not contaminated and the colony survives. The second more deadly way is when the bee comes in contact with an insecticide and transports it back to the colony, either as contaminated pollen or nectar or on its body."
This same scenario happens with Mason bees, wasps, flies, and other pollinators. Most pesticides attack the nervous system of the insect, leaving residual pesticide on the leaves, flowers, and fruit. Most pesticide problems are caused by a few pesticides but it’s not usually cost effective to use a pesticide when you can use IPM. Once you have a predator insect on your farm, and as long as you have a few pest bugs they will keep the pests below the threshold of fruit or vegetable damage.
8. Create Greater Biodiversity
If you want those beneficial insects to hang around you have to create some habitat. The use of cover crops and native plant edges around and in your fields will greatly enhance the beneficial diversity above ground, as well as below ground. Just as many beneficial insects only have a taste for certain pests, so too do microorganisms form mutualistic relationships with certain plants. Greater biodiversity in your fields creates more microbial activity and thus higher soil fertility as they break down organic matter into humus. Fertile soil is made up of microbes, humic acids and many other soil organisms. Using Humic Land can jumpstart your soil fertility. It contains humic acid, fulvic acid, and is a great source to increase your soil’s microbial activity and biodiversity. Humic acids are the building blocks of healthy soils and play a key role in improving soil fertility At first it may seem difficult to add biodiversity to row crops but using a cover crop mix between rows is highly beneficial for increasing crop yield and decreasing pest damage.
9. Incorporate Livestock with Crops
Whether you’re growing vegetables or commodity crops part of your rotation could be pasture. Leaving soil fallow does not add nutrients but growing cover crops as pasture and then grazing your livestock does. According to Moses Organic
"By combining livestock and vegetable production, the whole farm nutrient balance of imports and exports becomes more even. Along with nutrients, manure and compost applications tend to improve soil organic matter, biological activity, and potential disease suppression."(2)
The pasture, with nitrogen fixing clovers in the mix, and the addition of manure create a high fertility seed bed for the crops that follow. The livestock act as mowers and if you are using a no-till or strip-till method of planting your field is ready to plant.
Livestock can also be a secondary revenue stream for your farm. One of the topics rarely discussed is the ability of crop/livestock operations to build community in a farming area. Most farmers do one or the other and there is the opportunity to build rapport with area farmers, share equipment, and share knowledge.
10. What About Edible Cover Crops?
This is probably one of the least considered of the “10 ways farmers can improve soil fertility.” But the legume family has many edible species. Cowpeas and field peas both fix nitrogen in the soil and give protein-rich food. Fava beans are also a good choice for warmer climates. They all have substantial biomass and when planted in close rows will suppress weeds, support the microbial activity in the soil, and attract pollinators.
Planting legumes to improve farm fertility can be done anywhere on the farm. Because the seeds are large this is not a cover crop to broadcast seed. The flowers on legumes are attractive and could easily be incorporated into flower and vegetable gardens. By thinking of the farm in a holistic way, flower beds become an important part of the farm. Fixing nitrogen in the soil by the peony bushes improves soil fertility and increases the health of the flowers.
You live on a farm because you love it. A vase of cut flowers may be exactly what you need after a hot day in the fields. Harvesting some cowpeas for the winter may not constitute farming but there is a sense of satisfaction that you are self-sufficient.
