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EVALUATION OF SUSTAINABLE SOIL MANAGEMENT AND COVER CROP PRACTICES

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Introduction There is increasing 'on farm' interest in the use of cover crops to improve productivity and resilience of farming systems, and also for their capacity to provide wider environmental benefit. These goals are very much in keeping with Sustainable Intensification (SI) aspirations. While the term SI can be subjective, the Sustainable Intensification research Platform (SIP) suggests that key SI objectives in an agricultural context may be expressed as 'managing farmland to increase farm output and competitiveness, whilst protecting the countryside and enhancing environment and social benefits' (www.siplatform.org.uk). The SIP initiative is a highly collaborative platform, working with stakeholders to explore risks and opportunities associated with the practical delivery of SI across a range of perspectives and scales. At a farm level SIP study farms at Morley (Norfolk) and Loddington (Leicestershire) are examining further the impacts of cover crops on aspects of soils, environment and production at a range of scales.
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14th ESA Congress 59th September 2016 Edinburgh, Scotland
EVALUATION OF SUSTAINABLE SOIL MANAGEMENT AND COVER CROP
PRACTICES
R. STOBART 1 N.L. MORRIS 1 N. HINTON 2 H. FIELDING 1 C. STOATE 2
1 NIAB, Morley, Wymondham, Norfolk NR18 9DF, UK, Email: ron.stobart@niab.com
2 GWCT, Allerton Project, Loddington, Leicestershire LE7 9XE, UK
Introduction
There is increasing ‘on farm’ interest in the use of cover crops to improve productivity and resilience of farming
systems, and also for their capacity to provide wider environmental benefit. These goals are very much in
keeping with Sustainable Intensification (SI) aspirations. While the term SI can be subjective, the Sustainable
Intensification research Platform (SIP) suggests that key SI objectives in an agricultural context may be
expressed as ‘managing farmland to increase farm output and competitiveness, whilst protecting the countryside
and enhancing environment and social benefits’ (www.siplatform.org.uk). The SIP initiative is a highly
collaborative platform, working with stakeholders to explore risks and opportunities associated with the
practical delivery of SI across a range of perspectives and scales. At a farm level SIP study farms at Morley
(Norfolk) and Loddington (Leicestershire) are examining further the impacts of cover crops on aspects of soils,
environment and production at a range of scales.
Materials and Methods
Cover crop research at Morley (sandy loam soil) builds on the New Farming Systems (NFS) programme
(initiated in 2007). This examines tillage system (plough, inversion to c. 20 cm depth; deep non-inversion, c. 20
cm depth; and shallow non-inversion, c. 10 cm) and brassica cover crop (radish, Raphinus sativus) interactions
in large, fully replicated plots using farm scale equipment. Rotations alternate between winter wheat and spring
sown combinable crops, and rotations are differentiated further by the presence/absence of an autumn cover
before spring crops (for details see Stobart et al., 2014; Morris et al., 2014). Highly complementary research at
Loddington (clay loam soil) is evaluating cover crops at a farm level, using large scale field strip studies, where
a range of autumn sown cover crops are compared to farm standard approaches (over winter stubble or autumn
cultivation), followed by a spring oat crop established by direct drilling.
Results and Discussion
The interaction of brassica cover crop use and primary tillage method on the yield of other crops in the rotation
can be gauged though the NFS data presented in Figure 1. Positive yield responses from the use of a cover crop
are represented as values above the zero line and negative responses as values below. Findings suggest an
interaction between cover crop yield response and tillage practice; with brassica cover crop use in conjunction
with shallow non-inversion tillage more likely to give a positive yield response in this study. Interestingly the
only appreciable negative value in the shallow non-inversion tillage system was in 2014, where oilseed rape
followed repeated use of a brassica cover crop; this is discussed further in Stobart & Morris (2014). Findings
from the field scale evaluation at Loddington demonstrated both improvements in soil structure (lower VESS
score, Guimarães et al. (2011)) and in the yield of a spring oat crop following the use of cover crops compared
to an overwinter stubble area (Table 1). While it should be noted soil structure following cover crop use was
similar to that achieved with an autumn soil cultivation, the yield response in the following crop tended to be
greater where an over winter cover crop had been used. The mean oat yield response associated with cover crop
use (cf. stubble) was c. 0.5 t ha-1 (worth c. £60/€70 ha-1).
Table 1. VESS Score and follow crop yield (spring oats t/ha) in farm field strips following different cover crop and farm practice treatments
at Loddington, 2015
Treatment/
Cover Crop
Overwinter
Stubble
Autumn
Cultivation
Radish +
Oats
Radish
Radish +
Tillage
Radish
Rye +
Vetch
VESS Score
3.03
2.61
2.49
2.54
2.55
2.35
Follow Crop
Yield
6.26
6.57
6.77
7.26
6.66
6.36
14th ESA Congress 59th September 2016 Edinburgh, Scotland
Figure 1. The effect of tillage and brassica cover crop (before spring sown break crops in the rotation) on crop yield (t ha-1). Figure 1a
(plough based systems) and 1b (shallow non-inversion tillage); positive values are a benefit from rotational cover crop use. Crops in
specific harvest years were: 2009 (spring oilseed rape), 2011 (spring beans), 2013 (spring barley), 2014 (winter oilseed rape) and 2010, 2012
and 2015 (winter wheat).
Conclusions
Collectively these findings demonstrate both the potential for positive yield and financial responses associated
with cover crop use in arable systems, but equally that system interactions (e.g. tillage approach and crop
rotation) will impact on performance.
Acknowledgements
Defra funding for of the SIP platform is acknowledged and thanks are extended to SIP project collaborators, stakeholders and other farm
sites engaged in SI research. Specific acknowledgements are extended to Morley Farms, TMAF and the JC Mann Trust in relation to the
New Farming Systems project.
References
Guimarães M.L. Ball B.C. Tormena C.A.: 2011. Improvement in the visual evaluation of soil structure. Soil Use and Management, 27:
395403.
Morris N.L. Stobart R.M. Orson J.H: 2014. An appraisal of research, best practice and communication approaches for the management
of soil structure. Felix Cobbold Trust review.
Stobart R. Hallett P.D. George T.S. Morris N.L. Newton A.C. Valentine T.A. McKenzie B.M.: 2014. Platforms to test and
demonstrate sustainable soil management: integration of major UK field experiments. Aspects of Applied Biology 127: Precision
Decisions for Profitable Cropping, pp. 233240.
Stobart R. Morris N.L.: 2015. The impact of repeated brassica cover crops use on system performance and oilseed rape yield. Aspects of
Applied Biology 129: Getting the Most out of Cover Crops, pp. 5156.
... Research work undertaken by NIAB TAG, within the National Agronomy Centre ( Further research on a spring oat crop following autumn cover crops at Loddington (Leicestershire; (Stobart et al. 2016)) demonstrated improved soil structure characteristics (measured through the VESS system; (Guimarães et al. 2011)) from the use of cover crops compared to undisturbed stubble (similar improvement to that delivered by an autumn cultivation). The research also assessed mean yield responses in the direct drilled spring oat crop following the cover crop; a mean increase of c. 0.5 t/ha was recorded following cover crop use compared to the stubble area (and c. 0.25t/ha compared to the autumn 'farm standard' cultivation). ...
... recorded in winter wheat within the study from the use of legume and brassica cover crops within conventional arable production scenarios (Stobart and Morris 2011, 2014. Research examining the interaction of primary cultivation system in the NFS studies is also suggesting different patterns of yield response from the use of cover crops with different cultivation approaches (Stobart et al. 2016). Specifically shallow non-inversion systems have been shown to be more likely to give a positive yield response ( Figure 3); (Stobart et al. 2016). ...
... Research examining the interaction of primary cultivation system in the NFS studies is also suggesting different patterns of yield response from the use of cover crops with different cultivation approaches (Stobart et al. 2016). Specifically shallow non-inversion systems have been shown to be more likely to give a positive yield response ( Figure 3); (Stobart et al. 2016). It has been proposed that this is associated with improvements to soil structure and the effects of this on (Kruidhof 2008) subsequent crop performance. ...
Technical Report
Full-text available
Cover crops are grown primarily for the purpose of ‘protecting or improving’ between periods of regular crop production. There are four main types of use including; improving soil fertility, improving soil structure, managing weeds and pests and environmental management. The most appropriate cover crop species/management will depend on what the grower wants to achieve from the cover crop. Direct financial benefits can be assessed most easily though improvements in yield of following crops. However, sometimes yield improvements may be detected later in the rotation and repeated cycles of cover crop use may be required. Beyond yield improvement, cover crops can provide additional benefits for the farm and the environment (e.g. reduced soil erosion risk). However, there are also potential undesirable effects (e.g. rotational conflicts, increased weed issues and increased costs). This review investigates the scientific basis of the reported functions of cover crops to better understand the feasibility of these benefits including; nitrogen (N) fixation, uptake and release; weed suppression by allelopathic effects and physical competition; biofumigation against pests; soil erosion and runoff; soil health and fertility, including soil organic matter, soil physical properties and soil biology; cover crops as forage; biodiversity and habitat provision. Cover crop agronomy is reviewed including; common cover crop choices, establishment methods, starter fertiliser, pest management and cover crop destruction. Economic and decision making factors, including yield and economic responses are reviewed and methods for evaluating cover crops on farm given. Some of the key conclusions include; the most important agronomic factor for achieving benefits for cover crops is to establish early (late summer/early autumn); N uptake during autumn/winter is typically 30-100 kg N ha-1, with 10-100 kg N ha-1 released to the following crop; N fixation is most effective between 7°C and 20°C which means little N is usually fixed over-winter; a canopy cover of 30% or more over winter decreases risk of soil erosion and run off; increases in soil organic matter following cover crops ranged from zero up to 42%, with no study reporting a decline; cover crops with allelopathic effects include several cereal and brassica species, buckwheat, clovers, sorghum, hairy vetch, sunflower and fescues. Knowledge gaps include the characterisation and performance evaluation of different cover crop types, species and varieties, particularly under different conditions (e.g. soil type and weather). The effects of cover crops will be best understood using a network of long-term coordinated farm-scale experiments which feature common treatments and assessments. This will be particularly important for evaluating effects on soil organic matter which changes slowly over many years. A continually updated database is required to support decision making, calculate cost benefits and to focus research. Other priority knowledge gaps include characterisation of rooting, uptake and release of N and other nutrients, impacts on weeds, disease & pests in following crops, effects of livestock grazing and most appropriate techniques for cover destruction and establishment of the following crop.
Conference Paper
Full-text available
The New Farming Systems (NFS) research project is being undertaken on a sandy loam soil at Morley (Norfolk, UK). The programme is funded by The Morley Agricultural Foundation and The JC Mann Trust and is a series of large scale, long term, replicated experiments examining routes to augment the stability and output of conventional arable farming systems. Within this study cultivations follow plough, deep non-inversion, shallow non-inversion and managed (where decisions are made annually based on field assessments) systems. Rotations consist of winter wheat with a combinable break crop in intervening seasons (typically spring sown break crops). Where spring breaks are grown the rotational approaches are differentiated further by the presence or absence of an autumn brassica cover crop (radish, Raphinus sativus). In 2013/14 season all treatments grew winter oilseed rape for the first time. This facilitated a comparison between rotations with a short (four times in an 8 year period) or long (two times in an 8 year period) brassica inclusion. Yield reduction in oilseed rape is associated with short rotations, and understanding whether this outcome is also associated with frequent brassica cover crop use is an important question for growers. Findings show some reduction in oilseed rape yield associated with short (alternate) rotations of brassica cover crops (c. 6%), although to a lesser degree than would be expected from a short (alternate) oilseed rape rotations (c. 12%). The research also suggests some interaction between the yield reduction and cultivation system; with greater reductions being associated with inversion tillage.
Article
Spade methods to visually evaluate soil structural quality (Sq) are simple, quick, cheap and can be used by farmers, gardeners, consultants and the scientific community. However, European and Brazilian users of one such method, viz. visual evaluation of soil structure (VESS) which is a development of the Peerlkamp test, have been concerned about its subjectivity. The method of soil slice break-up and operator influence on scores have been questioned. Thus, our aim was to make soil scoring by the VESS technique more objective and thus to revise the scoring guide. We compared scoring with normal breaking up of the soil slice by hand with scoring after breaking up the slice by dropping (drop shatter) to make the soil break-up more operator independent. After slice break-up, aggregates were split by hand and their internal porosity was evaluated to develop the use of visible porosity as an aid to scoring. This proved inconclusive on its own, so a method of reducing larger aggregates to 1.5–2.0 cm core fragments and describing their shape and porosity was developed to score soil Sq. Breaking up a spadeful of soil by hand or by dropping resulted in the same Sq score. The method of reducing aggregates and evaluation of their shape improved VESS, particularly in the middle range of soil quality and the revised chart is shown. VESS was sensitive to changes in Sq in layers within the profile and its use for diagnosing Sq in different layers allows targeted soil improvement by tillage.
Platforms to test and demonstrate sustainable soil management: integration of major UK field experiments
  • R. - Stobart
  • P D Hallett
  • T S -George
  • N L Morris
  • A C -Newton
  • T A Valentine
  • B M Mckenzie
Stobart R. -Hallett P.D. -George T.S. -Morris N.L. -Newton A.C. -Valentine T.A. -McKenzie B.M.: 2014. Platforms to test and demonstrate sustainable soil management: integration of major UK field experiments. Aspects of Applied Biology 127: Precision Decisions for Profitable Cropping, pp. 233-240.
An appraisal of research, best practice and communication approaches for the management of soil structure
  • N L Morris
  • R M Stobart
  • J -Orson
Morris N.L. -Stobart R.M. -Orson J.H: 2014. An appraisal of research, best practice and communication approaches for the management of soil structure. Felix Cobbold Trust review.