Cattle and Crops: Completing the Nutrient Cycle

How many of us producers have a shovel in our pickup? When was the last time we used that shovel to thoroughly examine our soil?  Are we able to determine what a truly healthy soil looks like? Grab a shovel and take a look at your soil. Check out your soil profile. Does the shovel easily enter the ground? Is there a cottage cheese like structure? Is there a nice, deep rich brown color to your soil? Is the soil easily crumbled in your hand? All of these characteristics indicate a healthy soil. If you answered no to any of these questions, a look into your soil’s health may be just what you need.
Soil health has become a buzzword in agriculture. It is used as a way of understanding the impacts we have on the living soil ecosystem. The five principles of soil health are: cover the soil, minimize soil disturbance, create a diverse plant population, maintain continuous living roots and integrate livestock to complete the nutrient cycle and promote a healthy soil ecosystem. Highly disturbed soils with low organic matter, high weed pressure, poor soil structure and poor soil drainage are only a few symptoms of a “sick” soil. Continued interest in influences that impact soil biology, an important link to the physical and chemical characteristics of soils, have led to the reduction of tillage, fertilizer and pesticide use, thus reducing producers’ input costs.
Soil health also relates to the crops we choose to grow. When a plant is growing, it harvests energy from the sun and converts it into simple sugars for plant growth. As the nutrients begin to deplete around the root zone, the plant roots begin growing towards nutrients in the soil. The roots cannot grow quickly enough to harvest adequate nutrients for continued growth. They release simple sugar based compounds called root exudates that gather a microbial community that will help harvest nutrients from the soil. As microbial communities grow and expand, they release “super glues” in the soil that promote soil aggregation. Aggregation not only acts as a home for microbes but also creates channels that promote water infiltration and increases the soils’ ability to retain water.
Furthermore, root growth density, structure and depth are plant dependent, so care should be taken when deciding what to plant. Cover crops can be excellent nitrogen scavengers, soil builders, erosion preventers, weed suppressors and forage sources. As interest in cover crops continues, it is important to realize that although there are numerous benefits to keeping a living plant on your ground, each plant species can have harmful characteristics. Certain species may be better at suppressing undesirable weeds than others. Some species may become hosts to harmful pests. For example, cereal rye is a popular, fast growing cover that has the ability to reduce soil-borne diseases, nematodes and weeds, but it does not control weedy grasses and can increase cut worms and wire worms. Thus, rye would not be the most suitable cover to plant prior to grass crops such as corn, sweet corn, sorghum or wheat. Multispecies cover crops not only provide a variety of benefits, but helps fill gaps or mitigate the weaknesses of monoculture cover crops. Multispecies cover crops mimic nature, which uses a wide variety of plant species to maintain an effective system. Selecting the correct mix of cover crops for your production will take time, research and trial and error. A cover crop that is ideal for one producer may not be the best for another, so it is important to select cover crops that grow well in your area and meet you own soil health goals.
Producer oriented conferences, such as the Western Canada Soil Health and Grazing Conference we recently attended, can aid producers in forming a plan of action for their soils as well as start a conversation with local producers as to what management practices have worked well for them. While at the conference, producers and researchers alike shared principle ideas about incorporating cattle and cover crops into a cropping system. This approach has created healthier soils and a more cost-effective feed source for livestock. So, what happens to the soil when cattle graze?
Cover crops can provide a mixed culture forage for cattle to gain key macronutrients such as proteins, carbohydrates and fats. In exchange for the plant’s nutrients, manure and urine left behind provide a source of new microbes and new organic matter for plants and existing microbes. Addition of new microbes often signals to prevailing microbes that a new source of nutrients is available for consumption and use. This process feeds the continued growth of plants and completes the nutrient cycle.
But it doesn’t end there. An animal feeding on the plant also impacts its root growth. When cattle feed on plants, they trigger a survival response in plants that requires the plant to decide which roots best support the continued survival of the plant. The other roots are abandoned, but still serve as a home and food source for the microbial community. As the abandoned roots degrade, the tunnels left by the roots increases the soil’s water infiltration rate and improves the soil for macrofauna such as earthworms and arthropods. As the plant recovers, roots will resume growing normally and further improve soil structure.
The use of cattle and cover crops in agriculture operations provide the link to completing the nutrient cycle in the soil. The strong root systems of multispecies cover crop mixes provide numerous benefits to soil microbial communities and positively influence soil structure. These mixes can provide nutrients to cattle who in turn return nutrients to the soil. Successful implementation of management practices by well-known regenerative farmers such as Gabe Brown and David Brandt are excellent examples of soil health practices but should not be viewed as the silver bullet to healthier soils. Instead, their principles and view of soil management in a holistic manner can provide helpful guidelines to producers interested in improving their soil. Soils, like people, differ greatly and will require different strategies to strengthen them. So, grab your shovel. Get down. Get dirty. And get to know your soil.