How Cover Crops Can Help Farmers, Protect Drinking Water and Fight Climate Change
Is there a natural way to slow down erosion, improve soil health, enhance water availability, smother weeds, help control pests and diseases, and increase biodiversity in agricultural lands? The answer is yes, using a technique called cover cropping.
Cover crops are capable of offering a wide range of benefits. They’ve been shown to increase crop yields, breakthrough a plow pan, add organic matter to the soil, improve crop diversity on farms, and attract pollinators. Moreover, there is growing evidence that cover crops can improve crops’ resilience to heavy rainfall and drought.
As the name would suggest, cover crops are not harvested. They are crops grown to improve soil health. They are planted to support the growth of the actual crops. When cover crops reach the appropriate age, they are not harvested and are cut down instead. Their plant matter is left on the soil to decompose so that the soil’s nutrients are recharged.
In summary, cover crops have the following effects on soil and water:
Cover crops are capable of improving the amount of solar energy harvested.
Cover crops can increase the amount of carbon in the soil.
Cover crops are capable of restoring soil nutrients.
Cover crops support diverse ecosystems by providing food to both macro- and micro-organisms.
Cover crops contribute to evapotranspiration which increases the amount of moisture in the air.
Cover crops increase water infiltration through their roots and decrease soil bulk density. An increase in water infiltration means more water goes to groundwater instead of staying on the surface as runoff. Reductions in runoff are beneficial for water quality.
Cover crops protect the soil from the impacts of raindrops, they are also capable of reducing sediment production, and runoff velocity. This could also benefit water bodies, as nutrient introduction through runoff is lessened.
Cover crops can improve the biological, chemical, and physical properties of soil.
Cover crops improve both soil and water quality. It is capable of reducing nutrient and pesticide runoff by up to 50 percent. Aside from that, it can reduce soil erosion by 90 percent, sediment loading by 75 percent, and pathogen loading by 60 percent.
Cover Crops Can Protect Drinking Water
As mentioned earlier, cover crops can improve both soil and water quality.
Cover Crops Improves Soil Health
Cover crops have the ability to control erosion, improve water infiltration, and manage nutrients. All of which improve soil health and are associated with numerous on-farm benefits. Besides that, the aforementioned properties of cover crops could also lead to improved water quality. Reduction of erosion and improvement of water infiltration will reduce the severity of erosion and runoff. What little runoff remains would be relatively lower in nutrients as cover crops are capable of reducing nutrients in the soil surface. With the reduction of runoff, and the nutrients present in the runoff, eutrophication of nearby water bodies is lessened.
Organic Farms and Usage of Cover Crops
Cover crops can be used as a natural method to provide nitrogen, manage weeds, and improve soil health. This agricultural technique is favoured in organic no-till farming. Cover crops can be turned to mulch using a roller-crimper to incorporate the cover crop as a sort of green manure into the soil. The cover crop may also transfer their water into the soil through this method. When cover crops are used to provide nutrients, manage weed, and improve soil health, over the usage of chemicals. The amount of chemicals present in the soil surface is lessened which could lessen the amount of chemicals introduced into nearby water bodies.
Soil and Fertility Management
Cover crops protect the soil from water and wind erosion, which is one way of maintaining the soil’s fertility. However, the best way for cover crops to introduce nutrients into the soil is when they are crushed and turned to mulch. Cover crops are capable of improving the affinity of the soil around them to fertilizers. This reduces the likelihood of nutrients leaching out of the soil. When legumes are used as cover crops nitrogen fixation into the soil is improved. Some cover crops are able to unlock some nutrients that are already present in the soil and convert them to other forms of nitrogen that are easily usable by the plants. There are several factors as to how well cover crops are able to manage soil nutrients. These factors include the plant species used as cover crops, date of planting, plant biomass and maturity at termination date, residual soil fertility, and temperature and rainfall conditions. All in all, cover crops’ capability to manage soil fertility prevents the usage of fertilizers. As we’ve already mentioned multiple times, a reduction in the usage of fertilizers, pesticides, and other agricultural chemicals reduces the amount of chemicals that get introduced into nearby water bodies.
Climate Resilience and Water
Climate is the average weather conditions in a given area. Recently we’ve witnessed erratic weather patterns. Days of extreme heat, without warning, turn to days of extreme wetness. This kind of climate destroys soil health.
The good news is that cover crops can help improve the actual crops’ ability to grow despite the unfavourable climate conditions. On extremely wet days, cover crops can take up excess water through evapotranspiration. During days of extreme dryness, cover crops’ can be turned to mulch which increases water infiltration of the soil and incorporates moisture reserves into the soil. Furthermore, the cover crops’ root channels increase soil pore space which helps improve the soil’s ability to hold water. When crops are able to hold water, runoff is reduced.
Pest Management
There are several ways that cover crops can contribute to agricultural pest management. Their effectiveness in doing so is dictated by the placement, timing, and cultivars of choice. When done properly, cover crops can reduce insect infestations, diseases, parasitic nematodes, and weeds. Cover crops are capable of doing this because they can attract beneficial insects. Some of the best cover crops that attract beneficial insects include brassicas, buckwheat, and clovers. Cover crops’ protection may also come in the form of protecting the crops from the splashing of soil-borne pathogens onto the leaves. Some cover crop species such as brassicas, mustards, and sudangrass are capable of reducing verticillium wilt and other soil pathogens in the soil itself. Cover crops may also suppress weed growth.
Studies on pest suppressing mulches are still being conducted. In Michigan, some potato farmers reported that growing radishes suppress parasitic nematode infection of the potato.
Cover Crops can help minimize the usage of pesticides, which can reduce the usage of chemicals in farms.
Ecosystem Services
Cover crops have a vital role to play in the ecosystem, planting them improves the health of the ecosystem in a variety of ways. Cover crops are mostly beneficial for insects as they can provide both food and habitat. Beneficial insects reciprocate by pollinating the plants or by controlling the population of other insects. Besides insects, cover crops may also support birds and other wildlife. Due to the fact that cover crops reduce soil erosion, run-off, and nitrogen losses, they prevent the introduction of nutrients into bodies of water which, in turn, would protect the water bodies’ ecosystem from algal blooms.
Cover Crops and Soil
The positive effects of cover crops on water quality are tied with their positive effect on soil.
Reduction of Sediments
In agriculture, the most common water pollutant is sediments. Sediment is the result of water erosion over flat soils and is especially a problem in inclined areas. Cover crops involve the addition of more vegetative biomass which would transpire water, increase water infiltration, and decrease surface runoff and runoff velocity. The decrease in runoff velocity is particularly good at reducing sediments. In fact, doubling the velocity of runoff increases the amount of sediments and nutrients carried by them by up to 64 times. Doing the opposite significantly reduces the amount of sediments and nutrients carried by the runoff. Cover crops also protect the soil from the impact of raindrops. This reduces the ability of rain to break down soil aggregates and generate sediments.
Reduction of Nutrient Loses
A plot of agricultural land loses nutrient efficiency as a result of soil erosion for nutrients are also stripped away by the erosion. Cover crops are particularly good at scavenging some residual nitrogen converting them to protein. How well cover crops take up nitrogen depends on the amount of nitrogen present in the soil, climatic conditions, the plant species used as a cover crop, seeding rate, and planting and killing date.
Timing is a factor when it comes to the cover crops’ ability to take up nitrogen. Some species of cover crops, like Winter grass, take up nitrogen better during the fall and winter. However, beyond these seasons the winter grass doesn't take up that much nitrogen. For legumes, they accumulate nitrogen only in the spring. For the times in the year that the cover crops don’t take up nitrogen, they can be converted to mulch.
For improved nutrient management, grass or brassica species are able to absorb and recycle excess nitrogen from manure or fertilizer.
When nutrients are properly managed in agricultural lands, their excess nutrients don’t spill to nearby water bodies and ruin the water bodies’ quality.
Pesticide Usage
Cover crops have the potential to reduce pesticide usage by helping in pest management. However, it is not as straightforward as applying a pesticide and killing the pests directly. Using cover crops to manage pests may require a good understanding of the role of the specific cover crop species in the agricultural land’s ecosystem. With that said, using cover crops to manage pests is overwhelmingly beneficial to the environment. However, it can be challenging.
Some cover crop species are able to suppress weed growth. They compete with the weeds for sunlight, water, and nutrients. There are cover crop species like cereal rye that have an allelopathic effect on weeds. Meaning they release certain compounds into the soil which control the growth of any adjacent weeds. However, it is important to note that living allelopathic cover crops are better at suppressing weeds than dead mulches.
Cover crops are also capable of reducing some soil-borne pathogens. Ryegrass and cereal rye cover crops have been shown to reduce soybean cyst nematodes.
Unfortunately, there are some green cover crops that attract armyworms, cutworms, and slugs. To remedy this issue, these types of green cover crops are killed three to four weeks before corn planting to prevent infestation.
Cover crops can act as a form of trap for some pests. Some of the cover crops would attract the pest. When the pests are already inhabiting the cover crops, killing the cover crops early on would trap the pests.
Other methods of pest management involve letting the cover crops grow. For some cover crop species can attract beneficial insects that are able to control the population of pests. The interactions between these beneficial insects and pests must be carefully studied so that they can be utilized to their full extent.
With the effective usage of cover crops, pesticide usage can be reduced as the cover crops alone can handle a significant number of pests.
Cover Crops Help Fight Climate Change
Besides helping farmers and protecting drinking water quality, cover crops may be able to help with our fight against climate change.
Increasing Soil Carbon Storage
Photosynthesis is a natural process carried out by photosynthetic living things that convert carbon dioxide and water to glucose. Cover crops are capable of photosynthesis. However, when it comes to cover crops, their ability to store carbon dioxide into the soil has the greatest potential for reducing atmospheric carbon dioxide. Scientific studies have demonstrated that the amount of atmospheric carbon dioxide that cover crops are able to sequester to the ground is erratic. This is due to the wide range of uncontrollable factors that affect the ability of cover crops to sequester carbon dioxide.
Soil health in farmlands needs to be managed over the years. This is important because the full potential of cover crops’ ability to sequester carbon into the soil depends on the farm land’s soil health.
The farm land’s ability to sequester carbon dioxide into the soil would be wasted if they are converted for urban development. This is the reason why farmers should be incentivized to encourage them to continue with farming, instead of selling their lands to potential buyers who would convert them for the purpose of urban development.
If all farmlands would manage their soil health properly and use cover crops, they have the potential to become a huge carbon sink.
Reducing Nitrous Oxide Emissions from Groundwater and Surface Water
All over the world, farmers are adding nitrogen fertilizers to their agricultural lands’ soil. This is due to the fact that crops depend on the nitrogen that is present in the soil. However, these crops don’t always take up all of the nitrogen that is added to the soil. The excess nitrogen gets washed away into nearby water bodies. This would increase the amount of nitrogen in the water bodies which would then encourage the growth of microbes that can convert the nitrogen to nitrous oxide. This would ultimately lead to the increase of nitrous oxide in the atmosphere. This is not ideal because nitrous oxide is 300 times more potent than carbon dioxide when it comes to trapping heat in the atmosphere.
Cover crops are capable of solving this problem by absorbing most of the soil’s nitrogen through their roots. Aside from that, cover crops are capable of reducing runoff velocity and improving water infiltration into the soil. Both of which would lead to the reduction of nitrogen getting carried to nearby bodies of water through runoff. Another benefit that comes from cover crops’ ability to incorporate nitrogen into the soil is that the crops around them would benefit from the additional nitrogen that was already present in the soil. All of these combined lead to significant reductions in nitrogen pollution in nearby water bodies or groundwater which leads to reductions in the amount of nitrous oxide released into the atmosphere.
Despite the ability of cover crops to reduce nitrous oxide emissions from microbes in water bodies, some cover crop species may encourage nitrous oxide emissions in the soil. For instance, some cover crop species are capable of stimulating the growth of nitrous-oxide-producing microbes in the soil. When these nitrous-oxide-producing microbes would increase in number, nitrous oxide emission would increase. Aside from that, cover crop legumes add nitrogen into the soil. More nitrogen means more raw materials for the microbes to convert into nitrous oxide.
All in all, eliminating the use of fertilizers over cover crops usage doesn’t automatically lead to reductions in nitrous oxide emissions. Careful management practices are needed to reduce nitrous oxide emissions through cover crops usage.
Reducing Emissions from Fertilizer Production and Transport
Cover crops are capable of incorporating more nitrogen into the soil, reducing nitrogen losses, and converting atmospheric nitrogen to nitrogen forms that are usable by plants. This means that the usage of cover crops can be done for the purpose of reducing fertilizer use. However, it’s not that simple. It is still a choice that a farmer has to make, use cover crops and reduce fertilizer use. They could always use fertilizers even though they are already using cover crops. Besides that, fertilizers offer faster results than cover crops.
Still, if a farmer decides to use cover crops and do away with fertilizers, the continual usage of cover crops for several years can help improve soil health in agricultural lands. They can help fix nitrogen into the soil efficiently. The reduction in fertilizer use could also lead to a reduction in the amount of nitrous oxide emissions. However, if nitrous oxide emissions are a cause of concern, there should be a selection process wherein cover crop species that encourage the growth of nitrous-oxide-producing microbes would be excluded.
Cover Crops Can Help Farmers
Reduction in fertilizer and pesticide usage brought about by cover crops could translate to reductions in cost. So in a way cover crops benefit farmers as well. However, cost savings from the usage of cover crops isn’t immediately apparent. It needs to be viewed as some kind of long-term investment.
There are too many variables to accurately quantify just how many cover crops can help farmers economically in the long run. With that said, positive net returns from cover crops usage may come in the form of:
Reducing feeds cost for grazing livestock
Reducing cost in dealing with herbicide-resistant weeds
Reducing cost in dealing with soil compaction
Eliminating fertilizer usage which also eliminates the cost associated with fertilizer use.
Reducing cost associated with irrigation.
Cover Crops increase Yield
The greater the amount of food a farmer can produce, the greater their earnings. With cover crops’ proven ability to increase yield, farmers may be able to earn more. However, this increase in crop yields doesn’t happen immediately. It may take about a year or more of using cover crops before any noticeable increase in crop yields would be observed.
Fortunately, several studies guarantee that cover crops are capable of improving crop yields. In one study, data showed that cover crops increased corn yield by up to 3% and soybeans by up to 4.9% after five years of consistent cover crops usage. The data also showed that cover crops were able to increase crop yields during times of drought. There was one drought that cover crops increased yields greater than average, corn yields increased by up to 9.6% and soybeans by up to 11.6%.
A Profitable Long-Term Investment
Determining cover crops’ Return of Investment is not a straightforward undertaking. It’s complicated to calculate the cost of using cover crops. When the cost of using cover crops can’t be calculated accurately, it's hard to determine just how much the usage of cover crops improved crop yields and income in the farms that use them. Despite this, the usage of cover crops should be viewed as a long-term investment as its benefits have been shown multiple times in several high-quality cost-benefit analyses made by reputable research institutions. When cover crops are used for grazing or for managing herbicide-resistant weeds, there are some studies that revealed that they could pay off within a year. When they are used to alleviate compaction and improve nutrient management, cover crops may pay off after two to three years. All in all, cover crops as an investment may lead to lower costs and even increased revenue.
Things to remember when planning for Cover Crops
As mentioned earlier, to take full advantage of cover crops, thorough planning is needed.
Selection and Management
This Planning Process involves identifying goals and choosing the appropriate cover crop species that would help realize that goal. Aside from that, this part of the planning process also involves identifying important steps for managing the cover crops. Some common goals include improving nitrogen content in the soil, improving general soil health, reducing soil erosion, controlling weed population and growth, soil nutrient management, and improving and conserving soil moisture. While cover crops, in general, can help meet these goals. Each cover crop species has a specialty of sorts. Some cover crops may be better in improving nitrogen content than others but are less in other aspects. There is also the option of using cover crops cocktails or cover crop mixes, to achieve a specific goal.
Once the appropriate cover crop species has been selected, the next thing to do is determine the appropriate time to plant the cover crops and determine their proper placement. Timing is important when it comes to planting cover crops. Consider these situations. During winter, cover crops can help scavenge nitrogen during a time when nitrogen-hungry crops need nitrogen the most. During summer, cover crops can help improve soil moisture and break soil compaction. With the specific demands for each season in mind, cover crops that are capable of meeting those demands should be used for that season. Thus, for long-term goals, it is a good idea to rotate the cover crops. Also, farmers are encouraged to be open to the idea of cover crop cocktails as there is a high likelihood that their goals can only be achieved by using more than one cover crop species.
Other things to consider regarding cover crops management include determining when to plant seeds and when to terminate the cover crops. The weather needs to be considered as well.
Legumes
Legumes, like red clover, crimson clover, vetch, peas, and beans, are the best cover crop species when it comes to nitrogen fixation. However, they are not good at scavenging nitrogen that is left over after the cash crops. Legumes are also capable of preventing erosion, attract and support beneficial insects and pollinators, and increase organic matter in the soil. Legumes also vary in their productivity and adaptability to variabilities in the soil and climatic conditions. These should be taken into consideration when using legumes as cover crops.
Non-Legumes
Contrary to legumes, non-legume cover crops like forage grasses, buckwheat, mustards, brassicas, rye, wheat, barley, oats, and triticale, are better at scavenging nutrients. They are also capable of suppressing weeds and adding soil organic matter.
Non-legumes are great for managing excess nutrients. They are usually planted in the fall. They take up large amounts of residue nitrogen left behind the soil from the summer crop or due to a history of heavy fertilizer usage. However, their ability to scavenge excess nutrients may be reduced depending on the environmental conditions.
Cocktails or Mixtures
The main drawback to using cover crop cocktails or mixtures is that seeding, planting and managing them is a complex process. However, the best thing about cover crop cocktails or mixtures is that they offer the benefits of each individual cover crop species included in the mix. Cover crop mixtures also allow for the utilization of the different growth characteristics of each cover crop species. Compared to using single cover crop species, cover crop mixtures are usually better when it comes to producing overall biomass, incorporating nitrogen into the soil, tolerating adverse conditions, increasing winter survival, providing ground cover, improving weed control, and attracting a wider range of beneficial insects and pollinators.
Final Thoughts
Cover cropping is a good agricultural practice that benefits farmers, the environment, animals, basically entire ecosystems. It is a practice that is all-natural and may lead to the reduction of fertilizer and pesticide usage. On top of this, cover crops can improve soil health and improve nutrient utilization. They can also reduce erosion and slow down runoff. All of this leads to healthier water bodies as pollutants of agricultural origin are lessened.
Sources:
https://www.sare.org/resources/cover-crops/
https://www.sare.org/resources/cover-crop-economics/
https://ohioline.osu.edu/factsheet/anr-57
https://sare.org/Learning-Center/Bulletins/Cover-Crop-Economics