Due to the many advantages they may provide to soils, cover crops have become a standard practice within arable rotations, as discussed in earlier blogs. But, currently there is a lot more interest in their capacity to capture nutrients, particularly nitrogen, given the unstable fertiliser market. Not to be overlooked is the variety of habitats they offer to diverse insects and animals.
High levels of nitrate leaching might result from leaving land either cultivated or fallow throughout the winter with limited weed growth. In rare cases, nitrate losses over the winter have reached 130kg N per hectare. So, it is obvious that maintaining this through the use of a cover crop has numerous advantages. Surprisingly, when they are planted early, they can reduce nitrate loss to zero, but on average, we observe a 60% reduction in nitrate leaching, which is still considerable.
Because a cover crop can absorb nutrients as it grows, it produces valuable plant material. After being destroyed, this is put back into the soils, and when it starts to disintegrate, the nutrients are released into the soil as organic matter.
The soil can be stabilized and protected literally from rain by cover crops. This lessens "capping" of the soil's surface, which prevents sediment and nutrient runoff as well as soil erosion.
The date the cover crop is planted is the primary determinant of the amount of nitrogen uptake. The best seeds are those sown in August because they can benefit from longer, warmer days, which allows each plant to grow quickly in the early stages and form a strong root system.
In contrast to dry and harsh winters, cover crops are more likely to be successful in moist and mild winters. This is because nitrate is less likely to leave a plant's roots zone before the spring in dryer conditions. The more nutrients the cover crops can absorb the longer they are in the ground.
Of course, the root system of a plant is the key to understanding soil structure. Depending on the species used for cover crops, the root structure can vary; this should be considered while evaluating the soil. Usually, a mixture will comprise species with various rooting systems, including lateral, fibrous, and taproot ones. Combining these also makes it possible to target certain soil profiles, which lessens compaction.
How to evaluate your cover crop's worth
The effectiveness of your cover crop can be evaluated in a number of methods, including fresh weight cutdowns, worm counts, and visual evaluation of soil structure (VESS) grading.
A m2 sample of biomass from a representative region of the field is taken during a fresh weight cut down and sent for analysis. From the findings, you can determine how much N, P, and K was taken up by the plant material and how much was released back into the soil.
Fresh weight cut down findings for this year have revealed a wide range of nutrients being harvested, ranging from 30kg to 200kg N per acre. The date of drilling, the species of cover crop, the type of soil, and previous cropping are some of the variables that can result in such broad results.
VESS rating
By taking a tiny square of soil from the ground and analyzing the various profiles, a VESS score is calculated to represent the assessment of the soil's structure. Scores range from one to five, with one denoting "friable earth" and five denoting "extremely compact soil."
It is a good idea to evaluate your soil before applying a cover crop so you can compare the profiles pre- and post-cover crop and notice the differences.
The MySOYL app can sync notes and images of recent weight losses with the environment manager tool.
Assessing soil structure and completing VESS scores are Kings technical advisors Alan Johnson and Jim Egan, together with business development manager Clive Wood.
Worm tally
A quick approach to evaluate the condition of the soil is to count the worms. Using a "normal spade," you can do this by digging a 20 cm3 spit of soil and gently breaking it apart to count the number of worms within.
How to evaluate various worm populations and numbers of worms to determine if the number is higher or lower is well-described by the Agriculture and Horticulture Development Board (AHDB). However, keep in mind that worm populations will decline if the weather has lately been extremely cold or dry.
The ideal amount of earthworms, according to soil specialists, is 400/m2, as this is a reliable sign of healthy soils.
Summary
After reading this article, hopefully you have a better grasp of the advantages cover crops can have for your farm, especially if you have never utilized them before. They don't just hold onto nutrients; they also give your soil important protection, enhancing soil health and establishing a haven for helpful insects and wildlife.
The approaches listed above make it simple to gauge the impact they have on your farm. Get your spade now and start digging if you have them but haven't yet assessed the hard work they are doing in your soils.
Contact your local Kings advisor or send an email if you have any concerns regarding how to use cover crops effectively or how to evaluate their effectiveness.