Cover crops, an essential aspect of sustainable agriculture, play a pivotal role in improving soil health and farm productivity in the UK. These crops are planted primarily not for harvest but to cover the soil, hence the name.
Understanding Cover Crops
Cover crops are a diverse group of plants used by farmers to manage soil health, fertility, pests, and erosion. While they are primarily known for covering the soil surface, their benefits extend far beyond this basic function. These crops can be categorised into different types based on their characteristics and the specific advantages they offer.
Types of Cover Crops
- Legumes, such as clovers and vetches, are popular choices for their ability to fix atmospheric nitrogen, enriching the soil.
- Grasses, including rye and barley, are effective in preventing soil erosion and improving soil structure, making them a practical option for many UK farms.
- Brassicas, like radishes, are known for their deep roots that help in breaking up compacted soil layers, thus enhancing soil aeration and water infiltration.
The Benefits They Offer
Cover crops confer numerous advantages, essential for maintaining a healthy farm ecosystem.
Improve Soil Health
- They improve soil health by enhancing its structure and increasing the nutrient content, thereby fostering a better environment for microbial activity.
Retain Moisture
- Additionally, the canopy formed by these crops helps in retaining soil moisture by reducing evaporation.
Suppress Weeds
- Their growth suppresses weeds, reducing the need for chemical herbicides.
Control Soil Erosion
- The root systems of these crops stabilise the soil, playing a crucial role in controlling erosion.
Deter Pests
- Certain cover crops can deter pests and diseases, providing a natural form of pest management.
Implementing Cover Crops in UK Farming
The incorporation of cover crops in the UK requires strategic planning.
- The selection of appropriate cover crops depends on various factors, including the specific soil type, local climate, and the type of subsequent cash crop.
- Planting usually takes place after the harvest of the main crop, with the timing being critical for optimal growth and benefit.
- Effective management of cover crops might involve techniques like mowing, grazing, or ploughing them into the soil before they start flowering.
How Are Cover Crops Incorporated Into The Soil
Crops and Green Manure
Cover crops are incorporated into the soil through a process commonly referred to as “green manuring.” This practice involves several steps designed to maximize the benefits of cover crops to the soil and following crops. Here’s how it typically works:
1. Selection and Planting of Cover Crops:
- Species Selection: Farmers select cover crop species based on the specific needs of their soil and the subsequent crops. For instance, legumes are chosen for nitrogen fixation, while deep-rooted species like radishes are used for breaking up compacted soil.
- Timing: Cover crops are usually planted after the harvest of the main crop and grown during the off-season or between regular crop cycles.
2. Growth Period:
- Development: Cover crops grow and develop, fulfilling their roles such as fixing nitrogen, suppressing weeds, reducing soil erosion, and improving soil structure.
- Monitoring: Farmers monitor the growth to ensure that cover crops are terminated before they set seed to avoid unwanted propagation.
3. Destroy Cover Crops:
- Timing: The ideal time for terminating cover crops is just before or at flowering, when they have maximum biomass but haven’t yet produced seeds.
- Methods: Common methods of termination include mowing, crimping, or using herbicides. In organic farming, mechanical methods like rolling or crimping are preferred.
4. Incorporation into the Soil:
- Ploughing or Tilling: The terminated crop is turned into the soil using ploughing or other tillage methods. This process helps in breaking down the plant material.
- Decomposition: Once incorporated, the cover crop residues decompose, releasing nutrients back into the soil. This also adds organic matter, which improves soil structure, fertility, and microbial activity.
- No-Till Method: In no-till systems, cover crops are killed, and their residues are left on the surface as a mulch. This method enhances soil health by minimizing disturbance and erosion.
5. Waiting Period:
- Allowing Breakdown: After incorporation, there is usually a waiting period before planting the next crop. This allows time for the cover crop biomass to decompose and release nutrients.
- Monitoring: Soil conditions are monitored to determine the right time for planting the next crop.
6. Benefits to Subsequent Crops:
- Improved Soil Fertility: The decomposed cover crops enrich the soil with nutrients, particularly nitrogen if leguminous crops were used.
- Enhanced Soil Structure: The added organic matter improves soil porosity, water retention, and overall soil health, benefiting the following crops.
Challenges and Key Considerations
While cover crops offer numerous benefits, their implementation comes with its own set of challenges.
- Selecting the right species is crucial and should be based on the specific needs and conditions of the farm.
- Balancing the growth of cover crops with cash crops requires careful planning and resource allocation.
- It’s also important to choose species that are adaptable to the varied and often unpredictable UK weather conditions.
The use of cover crops presents a promising avenue for enhancing the sustainability and productivity of UK farming. By understanding their types, benefits, and the best practices for their implementation, farmers can significantly improve the health of their soil and the overall efficiency of their farming operations. This sustainable approach aligns with the broader goals of environmental stewardship and agricultural sustainability.
Green Cover Case Study: Newhouse Farm Partnership, Hampshire
The Newhouse Farm Partnership in Hampshire, managed by Andy Bason, has transitioned cover crops from an experimental phase to a core component of their cropping system. This shift was influenced by policy changes and inspired by neighbouring farms. Working with Kings technical advisor Will Moynan, Andy has fine-tuned cover crop mixes to maximize soil benefits.
The farm, spread over 1,200 hectares, practices diverse cropping and livestock rearing. It’s also a LEAF (Linking Environment and Farming) demonstration farm and participates in environmental schemes. Cover crops are used especially before spring cropping, covering about 250 hectares. The farm collaborates with Southern Water on cover crops for high run-off risk areas, using a specific mix that aligns with Southern Water’s requirements and aims for nutrient capture and organic matter increase.
The current cover crop mix, a variation of Kings’ Cereal-Free Green Cover Mix, includes radish, phacelia, linseed, buckwheat, and vetch. This mix is part of a four-year project with Kings and Southern Water to study nutrient uptake from cover crops and its availability to subsequent crops.
For establishment, direct-drilling has proven most effective, replacing previous methods involving cultivation and rolling. Destruction of the crops involves a combination of rolling during frost and low-rate glyphosate application. The benefits observed include improved soil structure, higher worm counts, and potential reduction in future fertiliser needs due to effective nutrient recycling and increased organic matter from cover crops.
Crop Rotation And Cover Crops
Crop rotation and cover crops are two fundamental agricultural practices that play a crucial role in sustainable farming. Both practices offer a range of benefits for soil health, pest and disease management, and overall farm productivity. Here’s how they work together:
Crop Rotation:
- Diversity in Planting: Crop rotation involves growing different types of crops in a sequential manner on the same land. This diversity helps in breaking pest and disease cycles, as different crops often attract different pests and diseases.
- Nutrient Management: Different crops have varying nutrient requirements and contributions. For instance, legumes fix nitrogen, enriching the soil, which is beneficial for subsequent crops that are heavy nitrogen feeders.
- Soil Structure and Health: Rotating crops helps prevent soil compaction and degradation, as different crops have different root structures and depths. This variation aids in maintaining soil porosity and health.
- Weed Control: Different crops can outcompete or suppress different types of weeds, reducing the reliance on herbicides.
Cover Crops:
- Soil Protection: Cover crops are planted primarily to cover the soil, hence the name. They protect the soil from erosion, reduce water runoff, and help maintain soil moisture.
- Soil Fertility: These crops can significantly enhance soil organic matter and fertility. Leguminous cover crops, for instance, fix atmospheric nitrogen, improving soil nitrogen levels.
- Organic Matter Addition: Cover crops, when ploughed back into the soil, add substantial organic matter, which improves soil structure, aeration, and water-holding capacity.
- Pest and Weed Suppression: Some cover crops can suppress pests and weeds through natural mechanisms such as allelopathy, where they release chemicals that inhibit weed germination and growth.
Synergy of Crop Rotation and Cover Crops:
- Enhanced Soil Health: When cover crops are incorporated into crop rotation, the benefits to soil are amplified. The organic matter from cover crops improves soil structure and fertility, which benefits the subsequent crops in the rotation.
- Integrated Pest and Weed Management: The combination of crop rotation and using cover crops offers a more robust approach to managing pests and weeds, reducing the need for chemical inputs.
- Improved Water Management: Cover crops help in water retention and prevent erosion, which is particularly beneficial in the non-growing seasons. This leads to better water management in the farming system.
- Sustainable Farming Practice: Together, they form a cornerstone of sustainable agriculture, minimizing the need for external inputs like fertilisers and pesticides, and promoting biodiversity.
Cover Crops For Organic Growers
Cover crops are a vital tool for organic growers, providing numerous benefits that align with the principles of organic farming. These benefits include soil health improvement, natural pest and weed control, and nutrient cycling, all without the use of synthetic chemicals. Here’s an overview:
Types of Cover Crops for Organic Growers:
- Legumes: Such as clover, vetch, and peas. They fix nitrogen from the atmosphere, enriching the soil naturally.
- Grasses: Like ryegrass, oats, and barley. They add organic matter and improve soil structure.
- Brassicas: Including radishes and mustard. These are known for their biofumigant properties and ability to break up compacted soil.
- Mixed Species: Combining different types of cover crops can provide a range of benefits in one planting.
Benefits in Organic Farming:
- Soil Health: Cover crops enhance soil structure, increase organic matter, and prevent erosion.
- Nutrient Management: Leguminous cover crops fix nitrogen, reducing the need for external nitrogen sources.
- Weed Suppression: Dense growth of cover crops can outcompete weeds, reducing the need for mechanical weeding.
- Pest and Disease Control: Certain cover crops can suppress pests and diseases, reducing reliance on organic pesticides.
- Water Management: They help in moisture retention and prevent nutrient leaching.
Incorporation into Organic Systems:
- Crop Rotation: Integrate cover crops into crop rotation plans for continuous soil cover.
- No-Till or Reduced Tillage: Minimise soil disturbance by using no-till methods or gentle incorporation techniques.
- Biodiversity: Diverse cover crop mixtures support a wide range of beneficial insects and soil organisms.
- Timing: Plant and terminate cover crops at the right time to maximise their benefits and prepare the soil for subsequent crops.
Termination Methods:
- Mowing or Crimping: Mechanically terminate cover crops to prepare for planting without disturbing the soil structure.
- Roller-Crimper: A tool used in no-till systems to knock down and crimp cover crops, creating a mulch layer.
- Livestock Grazing: Some farmers use livestock to graze cover crops, which naturally terminates them and adds manure to the soil.
Challenges for Organic Growers:
- Selection: Choosing the right cover crop species to meet specific farming needs.
- Management: Balancing the growth and termination of cover crops with the main crop cycle.
- Resource Allocation: Requires careful planning in terms of time, labour, and equipment.
