Bartholomews Ultimate Guide to Cover Crops
CONTENTS
1 - Introduction 2 - Six reasons why cover crops support soil health 3 - 5 Why cover crops
6 - Sowing options 7 - 10 What to sow 11 - 12 Mixture options 13 - Custom mixes 14 - 16 Black vs conventional oats 17 - Roots photo phase 18 - 20 Trial nutrient update data 21 - Notes
Introduction
Welcome to our guide to cover crops.
This booklet has been put together with the aim of displaying the benefits, reasons and options of growing cover crops.
SFI payments are becoming more prominent, and with the arable standard focusing on soil management, organic matter and ground cover, cover crops can play a key part in the actions required. With more extreme weather patterns coming through, creating more resilient soils is key. Cover crops are one way to increase organic matter, improve structure and reduce run off, which are all necessary to help maximise production from soils. With heavy rainfall, soils that are able to hold as much water as possible without becoming waterlogged are vital to be able to continue production. Conversely, soils that are able to maintain moisture without droughting in the dry weather are just as important. There is no one mix to fix all, but it is more dependent on soil type, cropping rotation, management and destruction. Each farm is unique and the scope for cover crops is huge. Working with industry leaders we have put together a comprehensive range of mixes that will work in a range of situations, combating the main reasons for using a cover crop. For those that want something more specific, we have the option of creating a bespoke mix. The information we have displayed on the key species can help make these decisions. Over the last few years we have run several trials, looking at how the species interact and take up nutrients, further adding to the species information. For more information on this, we have a dedicated cover crop trials booklet, which follows the crops from planting throughout the season, with details on rooting and nutrient uptake. We hope that you find this booklet useful and informative, please contact your agronomist or the seed department for more information. Email: seed@bartholomews.co.uk Call: 01243 755620 Boston Seeds
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6 Reasons Why Cover Crops Support Soil Health
1. Nitrogen fixation
6. Increased organic matter
2. Reduced leaching and run off
3. Improved soil structure
5. Weed control
4. Part of the SFI scheme
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Why Cover Crops? There are many important reasons why cover crops should be sown and utilised. Using a range of species and crops for different lengths of time, can create significant benefits for soil health. This is a non-exhaustive list of reasons why cover crops are beneficial: Nitrogen Fixation Nitrogen is fixed by rhizobium bacterium on the nodules of legume cover crops and this nitrogen will be freely available upon destruction and incorporation of the old cover crops. This freely available nitrogen can improve subsequent yields and reduce the need of purchased artificial fertiliser, thereby improving gross margins of any crop grown after a cover crop.
Reduced leaching and run off One of the greatest pollutants from agriculture is diffuse source pollution, which can arise from both nitrate leaching and soil run-off which deposits phosphates into waters courses in the UK. Both nitrates and phosphates in waters has detrimental effects to local water sources, such as eutrophication which causes algal blooms that reduce oxygen levels in the water and therefore reduces biodiversity in waters. Nitrates leach over winter when rainfall washes out nitrogen in bare soils not covered by a crop, whereas phosphates, which are bound to soil particles are deposited into surface waters by soil erosion. This is most prevalent in soils which have poor soil structure. You can help reduce these pollutants on your farm by planting a cover crop which will scavenge for leachable nitrates and help bind the soil thereby preventing further phosphate deposition in your local water.
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Organic matter/ climate change and carbon sequestration Cover crops have the beneficial effects on your soil structure which includes the building up of soil organic matter. Soil organic matter is the organic fraction of the soil, formed from decaying organic material such as vegetation and animal deposition. Organic matter is often depleted by heavy tillage systems in arable farming. By growing cover crops and incorporating them into your soil, you are helping to reduce your farms carbon footprint as you are capturing the carbon otherwise released to the atmosphere into the soil. As well as reducing the amount of carbon in the atmosphere, soil carbon sequestration can also improve soil health and its ability to retain warmth, moisture, and fertility; all of which are conducive to crop growth.
Weed control Growing a cover crop can form an integral part of an Integrated Weed Management programme. Certain species, such as White Mustard, Forage Rye have vigorous growth habits and typically outcompete which can suppress weeds. This natural suppression in weeds can lead to reduced herbicide use which is better financially and environmentally to the farmer. Other species, such as Black Oats may have some allelopathy effect on weed growth. Allelopathy is the secretion of natural chemicals by one plant to inhibit the growth of another. Better soil structure Cover crops which have vigorous rooting such as Black Oats and Forage Rye help promote good aggregation within the soil, opening pores for free movement of air and water which is essential for crop growth. Other species, such as Tillage Radishes have extremely strong tap roots which can break up compaction in soils thereby reducing the need for expensive machinery passes to break up the compaction. Using a mix of species with different rooting types enables soil structure to be improved across different depths.
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SFI As part of the updated SFI, cover crops are now included in the ‘ Actions for Soils ’ section, with the aim of protecting the soil surface and improving the soil structure. To be classed as a multi species cover crop, it should contain at least two of the following: brassicas, legumes, herbs, grass or cereals. This gives more scope with choosing a mix that is suitable for each farming situation, but they suggest using a more diverse mix to bring increased benefits. The cover crop has to be well established over the winter months, classified as December – February. An established cover crop can be grazed, so long as it meets the requirements of providing overwinter cover. For destruction of the cover, it should be done after the winter months. However there is a clause that can see it destroyed before then, if establishing an early sown spring crop – this must not be done more than 6 weeks before the spring crop is sown.
There are a wide range of sowing dates, dependent on what the cover crop is going to be used for. Most species will need to be sown by September to have established well enough before winter. Late sown species such as Rye can go in as late as October - this is ideal for following maize harvest. When to sow?
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What are my sowing options?
Phacelia
Rye
Vetch
Crimson Clover
Berseem Clover
Radish
Red Vetch
Mustard
Black Oats
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What to sow?
Phacelia Phacelia is very quick to establish and will mature in 10-12 weeks after sowing. It will produce a large, shallow root mass, making it useful for improving soil structure and organic matter, as well as preventing leaching. The biomass it produces also acts as a weed suppressant too. Once mature and in flower, it is a great attraction to bees and other pollinators. It can be used if OSR is in the rotation. Not winter hardy. Suggested sowing rate – 10-15kg/ha. Sow April – October
Vetch From the legume family, vetch is very suitable for fixing nitrogen, even in a relatively short space of time or even at low temperatures. It works well as a companion to Rye. Winter hardiness depends on variety but will break down quickly once incorporated. It can offer some effectiveness at weed control with the biomass produced. Will add protein to ruminant ’ s diet if used for grazing after. Suggested sowing rate – 50kg/ha Sow March – October Red Vetch A slightly more frost susceptible option to either Spring or Winter Vetch, that will produce plenty of biomass in a short space of time. Suggested sowing rate – 50kg/ha. Sow March - October
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Mustard White Mustard is used in situations as it is quick to establish and will produce a good amount of biomass. This makes it excellent at preventing leaching and controlling weeds. It can improve soil structure and build organic matter, but it is not winter hardy. Sown after cereals, mustard can be grazed from October/November. Brown mustard is used in situations where a biofumigant is needed and is more winter hardy. Suggested sowing rate – 10-15kg/ha. Sow April – September
Radish Broken down into two main types, there is the Oil Radish and the Tillage Radish. They are great for improving soil structure and removing compaction. They have large amounts of biomass, which acts as a great weed suppressor and can improve the soil organic matter. With its quick growth habit, it quickly produces a large leafy canopy, which can be incorporated back into the soil, enhancing soil structure and enriching soil humus.
Oil Radishes grow quickly, with a widely branched root system, penetrating deeply into the soil profile. This attribute aids the radish ’ s ability to scavenge for nitrogen, preventing leaching, allowing nitrogen to be recycled into the following crop. Oil Radishes can be further broken down in to three types, Classic, Type 1 and Type 2. Types 1 and 2 have some degree of nematode control, with Type 2 being the most effective. Tillage Radish produces a long tap root, penetrating through many different soil types and profiles, improving drainage and air movement through the soil. This deep tap rooted radish captures and stores nutrients from deep within the soil which is released during the spring for the next crop. Very effective at relieving soil compaction. Suggested sowing rate – 10-25kg/ha for Oil Radish & 10-15kg/ha for Tillage Radish Sow April – August for Tillage Radish, April – September for Oil Radish
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Rye A quick growing option that is fantastic for preventing leaching and scavenging nutrients, particularly Nitrogen. Even at low rates, Rye is great at supressing weeds and will help improve soil structure. Forage Rye can be sown as late as October and is winter hardy. It will provide early grazing in the spring for cows or can provide over wintering for sheep. Suggested sowing rate – 30-50kg/ha Sow August - October
Black Oats Deep fibrous roots on Black Oats make them suitable to improve soil structure and relieve compaction. Black Oats also contain allelopathic qualities, which help with the suppression of blackgrass germination. It can be sensitive to frost but able to be sown up until October. Suggested sowing rate – 30-50kg/ha. Sow August – October Please see information later on the differences between conventional oats.
Berseem Clover An annual legume that is quick to establish. It is great for nitrogen fixation but is not frost tolerant. There are significant varietal differences, Tabor, which is a single cut type with no regrowth after. Suggested sowing rate – 15kg/ha. Sow April – September
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Crimson Clover A great weed suppressant, producing plenty of biomass ( more than that of red clover ) that will grow at lower temperatures to other legumes. It has a very upright growth habit and degrades into the soil quickly after destruction, releasing nutrients for the following crops. It is also very attractive to pollinators. Suggested sowing rate – 15kg/ha. Sow August - September
Buckwheat A very fast growing species that is good at mopping up excess nutrients in the soil, particularly phosphates. Not frost tolerant and will break down quickly once incorporated. Shallow roots are produced but plenty of about ground biomass. Suggested sowing rate – 50kg/ha. Sow May - August
Remember
There are no wrong answers when it comes to putting a cover crop in, each situation might vary, which is why a mix is often the best way to go. Each species has its own benefits that can improve the soil. Cover crops can be a post-harvest catch crop, an over winter cover or just around field edges for attracting beneficial insects or wildlife in areas that are not being cropped.
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New Bartholomews Mixes From our successful trials of 2020 and 2021, we have put together some new mixes to add to the existing selection we offer.
Bartholomews Foundation mix • Vetch, Buckwheat, Phacelia
Bartholomews Enhanced mix • Vetch, Buckwheat, Phacelia & Oats Using the base of the foundation mix, our enhanced mix, offers a larger range of species with different rooting depths covering all bases. No brassica in this mix, suiting rotations with other brassicas in. Sow at 30kg/ha.
Our basic mix, which will provide above ground biomass, nitrogen fixation and nutrient scavenging. No cereals and no brassica in this mix, offering an easy entry into the following spring crop. Suitable for mixing in with own cereals. Sow at 15kg/ha.
Standard Mixes
Grabber • Rye, Vetch
Soil Improver • Oats, Mustard, Oil Radish, Phacelia A slightly simpler version of the Green Reward. Soil Improver ’ s root structure covers different levels of the soil profile. Soil Improver is ideal to follow a cereal crop and helps retain moisture for the following crop. Quick to establish, its root structure covers different levels of the soil profile, and it is proven to up organic matter content. Sow at 40-50kg/ha.
This mix provides over winter cover that can be grazed, whilst helping to scavenge and fix nitrogen and reducing weed pressure. Winter vetch has a prolonged growing season and fixes Nitrogen at lower temperatures than other legumes. The rye develops a strong root structure to scavenge Nitrogen from the previous crop. Sow at 35-50kg/ha.
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Sprinter ·Black Oat, Vetch
Specifically chosen for that early autumn sowing where high biomass is required but mixture is not required to overwinter. This is a short term cover crop that will be taken out by frosts but provides exceptionally quick coverage. Black Oats are exceptionally quick to establish but late to mature, reducing risk of unwanted seed shed. There is a large amount of biomass produced above and below ground with the deep roots of black oats. Vetch establishes and grows quickly in the autumn. Sow at 25-35kg/ha.
Green Reward ·Rye, Black Oat, Oil Radish, Tillage Radish, Mustard, Vetch, Phacelia
This mix has been tried and tested for a few years now, offering a wide range of rooting types. A premium cover crop mixture which will improve your soil structure, help reduce compaction and leave the soil in a healthy state ready for the next crop. It ticks all the boxes for soil improvement - improved organic matter, moisture retention, traps and recycles nitrogen, and improved soil structure. Sow at 40-50kg/ha Summer Thrive • Black Oat, Vetch, Buckwheat, Berseem Clover, Linseed, Phacelia This is a mix with a diverse range of rooting depths and types to ensure different layers of soil are conditioned. Designed for sowing after early harvested crops and incorporating before autumn-sown cereals. It will also produce a significant amount of organic matter for incorporation. Sow at 20kg/ha. Winter Revivor • Rye, Vetch, White Mustard, Brown Mustard, Crimson Clover, Oil Radish, Tillage Radish Most effective combination of winter hardy species to improve and condition the soil with variable rooting depths. Varying plant types and root profiles maximise soil conditioning and spring organic matter production. Deep taproots of oil radish breaks up soil compaction whilst clover helps to scavenge nutrients. Sow at 20kg/ha.
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Boston Seeds
Custom mixes are available; please call the seed department to discuss your individual requirements. These custom orders cannot be cancelled or returned due to the specialised nature of the order. We also have a range of straight species available.
Boston Seeds
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Plot 5 Conventional Oats
Plot 13 Black Oats
Conventional Oats vs Black Oats
Plot 13 Black Oats Root Growth
Plot 5 Conventional Oats Root Growth
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Data taken from our 2021 trial.
Comparing the nutrient uptake for the conventional and black oats, at first glance the conventional oats have taken up more of the macro nutrients.
Only with the uptake of calcium, have the black oats been more efficient than conventional. The phosphorus, magnesium and sulphur have all been fairly similar in uptake.
Looking at the micronutrients, the Black oats have a slight edge in uptake. This is mainly seen in the uptake of Zinc, but there is a small margin in the copper and boron as well. Molybdenum was omitted due to the very small amounts seen in both types of oat.
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The black oats seem to have taken more nutrients up. This is seen in the Nitrogen, Phosphorus, potassium and Sulphur. There is minimal difference in the uptake of magnesium. Only the calcium has seen more
of an uptake in the conventional oats.
Similar to the leaf analysis, the zinc has seen the most uptake, particularly in the black oats too. The boron and copper uptake are very similar in both, but the conventional oats taking up slightly more boron. Manganese has been separated due to the larger amounts. The nutrients taken up into the leaf are more in the black oats, however conventional oats have more in the roots.
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Nutrient uptake Looking at the data from our 2020 trial, over a three month period, we can see how the nutrient uptake has varied between species and treatment. Broken down into Major or Minor nutrients and Carbon uptake.
The Nitrogen in the plant has increased, over the first two months and then dropped back down by the third month.
The Winter Vetch ( nacre ) has also seen a decrease in Nitrogen, which could be accounted for by the lack of active growth from the cold soils, not utilizing the root nodulation.
Whilst staying the most consistent in Nitrogen uptake, the Soil Improver mix saw a drastic drop in overall major nutrient uptake by January. This is also seen in the Sprinter mix.
Kora Buckwheat has seen the best increase as a single species from the first two months, followed by a drop in uptake which is most likely due to the plant beginning to senesce from the frosts. The radish Discovery is the species that has seen, even though it is marginal, an increase in nutrient uptake in January. The Romesa radish, similarly, has not seen as much as a decrease as other species or mixes in this month.
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Nutrient uptake Uptake on the minor nutrients is commonly increased with the single species in the first two months and decreased in the mixes. The majority of species and mixes have seen a decrease in January uptake. The Soil Improver mix is the only one to stay consistent in the uptake of the minor nutrients.
As the Buckwheat begins senescing the uptake has decreased, shown here with the decrease in uptake over the three months.
The Sprinter mix has seen a significant decrease in the uptake of Molybdenum, compared to the other nutrients.
Boston Seeds
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Nutrient uptake The majority of plots have seen an overall increase in the uptake of carbon, over the three months samples. The mixtures have a better uptake than the single species, with the N Fixer and Green Reward showing the biggest difference between November and December, and an increase in January uptake.
Both types of radishes have seen an increase in the January uptake.
Only the N Fixer and Sprinter mixes have seen an overall increase in carbon uptake.
Boston Seeds
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Notes
If you would like any more information please contact the seed department on 01243 755620 or email: seed@bartholomews.co.uk
Visit our website at www.bartholomews.co.uk
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