Is it too late to plant cover crops?

Cover crops are crops grown in between cash crop cycles, intercropped with cash crops, or planted in the absence of a normal crop. 

They are grown to protect the land from soil erosion and loss of nutrients and to add organic matter to the soil, which can lead to increased soil microbial populations and diversity. 

Cover cropping is an important component of sustainable agricultural systems because it helps build soil health and makes the soil more resilient to drought and other extreme environmental factors.

While cover cropping can deliver many positive on-farm benefits, farmers in dry regions, including Nevada, face several challenges related to incorporating cover crops into their farming systems. Major challenges include which cover crop to select, cost and ease of establishment, and availability of water to raise cover crops. Growers are also concerned about the cost of seeds, tillage, irrigation, weed control, and termination of cover crops, especially in the current challenging economic climate. Many growers are reluctant to grow crops that may not be harvested and that will not deliver immediate economic benefit.

Another concern among dryland farmers, is the challenge of cover crop establishment under the recurrent droughts this region has been facing. There may not be enough rainfall in the preceding fall and winter seasons to guarantee the establishment and growth of summer cover crops in these semi-arid dryland areas. 

Additionally, farmers are also concerned that cover crops will extract too much water from the soil profile, thus limiting the water that will become available for the following cash crop.

Research results have shown that the amount of water accumulated in the soil profile during the winter may affect the yield of the following cash crop in semiarid dryland farming systems (Unger and Vigil, 1998).

One of the emerging innovative ways for cover cropping in semi-arid dryland systems is to combine no-till or minimum tillage with cover cropping. Reducing tillage intensity can help improve soil health, promote water infiltration, and reduce evaporative losses during the period that the cover crop is growing. Moisture utilization by the cover crops is counterbalanced by the improved infiltration and reduced evaporative losses that occur in no-till and minimum tillage systems (Unger and Vigil, 1998).

While cover crops can deliver many benefits within cropping systems, using them may not always be easy. There are many barriers that growers face when contemplating the utility of cover crops, especially in arid and semi-arid regions. To successfully practice cover cropping, it is important to address the following issues.

1. What is the goal for cover cropping? There are many possible goals that you can set before selecting a cover crop, including building up soil organic matter, managing soil nitrogen, protecting soil from erosion, or suppressing insect pests, diseases, and/or weeds. Setting a goal can significantly affect the cover crop that you select.

2. Soil type and properties. It is important to know your soil type—including its physical properties and inherent abilities and limitations—before you can select an appropriate cover crop.

Questions to consider include: Is it a heavy soil or a sandy soil, or in between? How do crops typically respond to fertilizers on the soil? Do I have salinity problems? What is the drainage condition of the soil? Are there other soil limitations like a hard pan?

3. Crop rotation. Your rotation will also determine which cover crops will fit into your cropping system. If you grow a winter cash crop, then summer cover crops may fit better into your rotation, whereas if the cash crop is grown in summer, a winter cover crop will be more suitable. Also consider what chemicals (e.g., herbicides) have previously been used for the cash crop that might negatively affect the cover crop.

4. Suitability for utilization/frequency of harvest. In some situations, you may wish to use the cover crop for marketable income or on-farm needs. A forage crop (such as sorghum–sudan) is an example of this, in which the first growth cycle or cutting is used for forage or income and the last growth cycle is worked back into the soil as a cover crop. In the case of perennial systems such as alfalfa, the last cut before the alfalfa field is terminated is incorporated into the soil as the cover crop.

5. Soil preparation and other cultural practices. It is important to know the soil preparation needs of the cover crop for proper establishment. For example, some small-seeded cover crops may be challenging to establish in heavy soils and/or heavy residues (e.g., no-till). It is also important to understand the growth pattern of cover crops and how to effectively terminate them. A crucial aspect is to know when cover crops go into the seeding stage. It is advisable to terminate cover crops before they set seed; otherwise, they may become weeds and affect the growth of subsequent cash crops.

6. Irrigation and water availability. In arid and semiarid regions such as Nevada, water availability is very crucial for crop production. Farmers need to assess how much water is available for growing cover crops and when water is most available in the system (e.g., irrigation supply or monsoonal rains). Crop production should be planned such that the amount of water used to raise cover crops will not cut into the water needed to raise the cash crops. It is more desirable to choose drought-tolerant cover crops in situations with limited water availability.

As we move into late fall the question is; “Is it ever too late to seed cover crops?”

The short answer: It depends.

Each situation is going to depend on the variables and conditions of that particular farm and farmer,”. Your weather conditions, location, the number of acres you have, the species of cash crop you’re coming from and going to, as well as equipment, all play a role in determining whether it’s too late to get your cover crops seeded.

Many experts say that it is never too late to plant cover crops, but if you wanted the benefit in the fall and early winter, then it’s too late. If you’re looking for benefits in the spring, as many farmers are, there are several species or mixes that can overwinter and still put on some growth in the spring.

The Midwest Cover Crops Council has a cover crop selector app available at (https://mccc.msu.edu/selector-tool/). Although, this selector tool was developed for the Midwest, it can still provide some useful information for our region. When selecting a State, select one that is similar in latitude and weather to Nevada.

As we get later into the fall, you may want to avoid any species that is not suitable for surviving cold weather, such as radishes and some specific clover and oat varieties. Instead, wheat, triticale and cereal rye are some of the go-to species for late-seeding — according to Sustainable Agriculture Research and Education (SARE), cereal rye can germinate in soil temperatures as low as 34 degrees Fahrenheit, and needs at least 38 degrees to begin growing.

Also, if you’re planting late you should plan on using a cheaper variety, so if it does fail the economic impact would be considerably less.

Sources:

Principles of Cover Cropping for Arid and Semi-arid Farming Systems Guide A-150 John Idowu and Kulbhushan Grover.

When is it Too Late to Seed Cover Crops? By Laura Barrera