In this article series we have been exploring the efficiency, substitution, redesign [ESR] framework which outlines pathways for transitioning from high input, intensive production systems toward biologically based, ecologically integrated systems. Here in the final piece we will discuss practices and strategies that begin the process of redesigning the production system and how these practices can help reduce dependency on external inputs.
A central concept of the redesign process is to acknowledge the context of the farm within its ecological surrounds and work to integrate the production areas into the surrounding landscape and environmental setting. Terms like agroecology or ecological intensification emerge here and perhaps a rather simplistic but useful definition could be defined as ‘the goal of simultaneously producing food and supporting the surrounding ecology’ or ‘designing farms toward multifunctionality’ [figure 1]. There is much more detail and nuance to these concepts in reality but critically, when the focus is not solely to maximise production but to optimise both production and ecology, there are numerous benefits that feedback towards production from a farms in-field and surrounding ecological intensification and these gains do not necessarily come with a cost on yield1.
A definition of the redesign process [which I have humbly adapted from another source2] is ‘the establishment of an ecological infrastructure from field- to landscape-scale that uses diversification and biological interactions to generate soil fertility, nutrient cycling and retention, water storage, pest/disease regulation, pollination, and other essential ecosystem services.’ There are many strategies that can be implemented as part of this redesign process. These might include widening rotations with new cash crops, use of cover crops, intercropping, breeding novel varieties, reducing tillage, direct drilling, split fertilisation, livestock integration, buffer strips, conservation areas, wildlife shelters, agroforestry and silvopastures. For the purpose of this article, we will discuss four key themes – plant species diversity, intercropping, mixed farming systems and ecological integration.
Plant Species Diversity
The vast majority of production systems that have become mainstream in today’s agriculture are built around monocultures. In this pursuit of uniformity, not only do we plant the same species, but we also go a step further and plant the same variety of that species too. Undoubtedly there are some advantages to this approach, but it also comes with many weaknesses – particularly in the context of input dependencies. Uniform stands of plants are more likely to accelerate the development of pest resistance and hence be susceptible to and spread pest and disease problems. Additionally, uniform root structures and depths leads to greater competition for moisture and nutrients as compared to a diversity of roots growing at different depths. Both of these weaknesses typically lead to a situation of higher pesticide and fertiliser dependency to overcome the inherent design fault of the monoculture. On a transition to redesigning production systems, arguably taking the initial steps away from monocultures toward more diverse plant stands is a key starting point. Let’s explore a few examples of the changes and benefits that occur as production systems move from uniformity to diversity.
When compared to monocultures, more diverse plant stands have been shown to increase many soil biological properties – microbial biomass and respiration3,4, bacterial and fungal biomass and the fungal:bacterial ratio5 and mycorrhizal fungi6,7. A greater diversity of plant root systems also yields favourable outcomes on soil structure by improving aggregation and aggregate stability8,9. Improved biological and physical functioning of the soil environment ultimately leads to improved nutrient cycling and availability for plants3,10–12 hence lowering the dependency on fertiliser inputs. As production systems move away from monocultures and into mixed cropping, the introduction of additional plant species begins to dilute the susceptible cash crop and with this dilution effect, pest pressures decline. There is a good body of evidence highlighting that more diverse production systems more often than not have lower insect, disease and weed pressures13–16. Lastly, plant diversity has also been demonstrated to increase soil carbon levels in a range of environments and production systems including forests, grasslands and cropland systems12,17,18. A transition towards greater species diversity is straightforward enough to implement in grassland systems however it is much more challenging in cropping systems. The practice of companion and intercropping has gained major traction in recent years as jumping from one to two species is a much more manageable transition and consequently, we will devote special attention specifically to this practice.
Companion and Intercropping
At the field level, there has been significant interest in and adoption of intercropping in recent years and I personally believe this shift towards multi-cropping systems will only become more and more mainstream over the next decade or two. This trend has also been reflected in the research arena with an ever-increasing number of published studies on intercropping14 [figure 2]. Although there are plenty of barriers remaining to the widespread adoption of intercropping, jumping from a monoculture to a bi-culture is practically much more feasible than moving towards complex polycultures and this small shift from one to two plant species can indeed lead to significant changes in soil properties and pest and disease resistance [as partly outlined in the previous paragraph]. Companion cropping [where one of the companions is terminated and only one taken through to harvest] provides an opportunity for beginners to experiment with the practice and is also more common in drier environments where there are concerns about sufficient moisture to bring both crops to maturity.
The most common type of intercrop is a cereal:legume combination and there are many advantages for the cereal when combined with a legume which can supply some nitrogen to the cereal in real time17,18 and improve overall nutrient scavenging via their more acidic root exudates11. Equally the upright cereal can provide scaffolding and prevent lodging in the legume. Some common examples include wheat:beans, wheat:peas, barley:peas, oats:peas, corn:beans. corn:vetch. Beyond this the number of combinations of intercrops is limited only by the imagination of the farmer but some other common combinations include pea:canola, canola:beans, linseed:oats, chickpea:linseed, camelina:lentils for example. Let me be clear that not all plant combinations are by default collaborative; some can indeed be competitive and consequently there are many variables to consider when planning for intercrops. Beyond choosing suitable plant partners, factors such as variety selection, seeding rates, row spacing, planting arrangement [alternate vs same row], soil fertility and local environmental constraints should all be considered. For example, a higher legume percentage in a mix encourages more N transfer to the non-legume companion. Planting in alternate rows of 1:1 has been shown to transfer more N than a planting configuration of 2:1 [cereal:legume]. A somewhat common starting point when pairing two plant species is to half the seeding rate of each monoculture. However, with different growth habits, the canopy of one species can dominate and smother out the companion, so it is a delicate balance and some trial and error is required. For example, oats can smother out peas so to compensate, the seeding rate of peas can be increased from 50% up to 70% of the full monoculture rate.
Mixed Farming Systems
Prior to advent of industrial agriculture which spawned a focus on segregation and specialisation, mixed farming systems were the norm. The objective of these farming systems is for self-sufficiency of feedstuffs for the animals and maximum possible nutrient recycling between soil, plants and animals within the farming unit19. This way nutrients are not lost from the farm’s soils, and nutrients are not imported into the farm unless they are deficient and critically needed. Beyond this, integrated crop and livestock systems bring a suite of ecosystem services and benefits to biodiversity that are unique to these systems while they can also help reduce some of the negative effects of either segregated system [surplus nutrients in livestock systems for example]. A comprehensive meta-analysis showed that organic amendments increased crop yields an average of 27% vs mineral-only fertilization. Farmyard manure specifically had the highest effect while organic amendments also increased soil organic carbon, total nitrogen and microbial biomass when compared to mineral-only fertilisation20.
Trees also provide a unique opportunity for integration into farming systems not just for aesthetic value or wildlife habitat but also with a silvoarable and silvopastoral production focus. Traditionally trees have primarily been used as hedgerows, windbreaks, shade, buffer strips, near riparian zones or for timber but they also provide opportunities to integrate into crop and livestock systems and can improve productivity of both pastures and crops, support soil conservation, supply bioenergy, increase land use diversity and also income diversity [especially when high value fruit or nut trees are utilised – figure 3]. Enriching pastures with high value forage shrubs can also improve whole-farm profits through reduced supplementary feeding, deferred grazing of annual pastures and other benefits such as animal health with many trees and shrubs bringing anthelmintic properties. Lastly, planting woody plant species alongside crops has been demonstrated to double the number of insect pollinators and improve species richness of solitary bees21.
With the term ecological integration, I am referring to strategies that manage or create more semi-natural and wildlife friendly areas on the farm, be that in-field or surrounding field or farm margins. As outlined already, the easiest way to increase ecological function in-field is to simply increase diversity of plants, trees and animals; which strikes the balance between ecological improvements but still with a production focus. The use of cover crops on the shoulder seasons is also a good example of an easily implemented in-field practice. Beyond this, the 3 key strategies to ecological integration are protect, expand and create:
- protect any natural and semi-natural areas as a priority
- expand and connect these areas wherever feasible, and
- create and integrate new ecological spaces
As with most wild spaces, protecting existing habitat means getting out of the way and leaving it be. This might mean not trimming hedgerows or field margins yearly but perhaps every 3-5 years instead and staggering this process so there is always a percentage of wild and overgrown hedgerows present on the farm. Equally, trying to make functional use of headlands and ditches – leave them to grow tall grasses and don’t slash them short. As a general rule, the taller the better for habitat so intentionally planting up field margins with a mixture of short and tall grass and herb species is advised. It could also mean leaving weed species too, weeds can provide beneficial habitat and food source for pollinators as long as the weeds are not above an economic threshold of course. In terms of creating new parcels of ecologically functional land, plant more hedgerows or a flower rich habitat comprising a mixture of annuals and perennials can be planted around field margins, alongside watercourses or farm tracks and under/around gateways. It depends on the insect species but many beneficials will migrate from field margins approximately 50m into the canopy of the cash crop22. Consequently, dividing larger fields with flower strips every 100m or so can ensure the full cash crop area is receiving the ecological benefit of predator migration and biological pest control [figure 4]. In summary, it is a major wasted opportunity to leave field margins to a simple stand of grass and keep it mowed, neat and tidy. A very easy first step for farmers wanting to integrate some ecological practices into the farm is to plant up these field margins with a diverse mix of tall and short grasses, flowering plants and herbs; both a combination of annuals and perennials. This will provide shelter, food and habitat for a host of mini beasts to live, feed, reproduce and provide valuable services for the in-field production areas as part of an integrated pest management approach.
The efficiency, substitution, redesign concept provides a useful framework for managing the transition of production systems towards soil health and agroecosystem sustainability. Improving the efficiency of external inputs and substituting away from these inputs towards more biological based solutions are important steps and can provide many positive economic and environmental outcomes. However, redesigning production systems towards a greater level of ecological integration is absolutely an essential part of the transition process if we are to achieve a sustainable balance between food production and environmental restoration. Implementing biodiversity-based strategies starts at the field scale with practices like intercropping, cover cropping, multi-species pastures, agroforestry and integration of livestock. Practices that protect, expand and create semi-natural parcels of land with intentional management of hedgerows, flower strips and tall grassed areas at the landscape scale, is also necessary. On this journey from uniformity to diversity and to achieve an impactful level of ecological integration we cannot omit the essential stage of system redesign, as it is with this redesign, that we will, regenerate.
Read another article in our series with Joel Williams on The Microbial Pathway to Soil Organic Matter Formation.
- Agricultural diversification promotes biodiversity and multiple ecosystem services without compromising yield. (2019). doi: 10.1126/sciadv.aba1715.
- groecology: The science of natural resource management for poor farmers in marginal environments. (2002). doi: 10.1016/S0167-8809(02)00085-3.
- Plant Diversity, Soil Microbial Communities, and Ecosystem Function: Are There Any Links? (2003). doi: 10.1890/02-0433.
- Meta-analysis shows positive effects of plant diversity on microbial biomass and respiration.(2019). doi: 10.1038/s41467-019-09258-y.
- Root biomass and exudates link plant diversity with soil bacterial and fungal biomass. (2017). doi: 10.1038/srep44641.
- Glomalin Production and Infectivity of Arbuscular-Mycorrhizal Fungi in Response to Grassland Plant Diversity. (2014). doi: 10.4236/ajps.2014.51013.
- Arbuscular mycorrhizal fungi respond to increasing plant diversity. (2002). doi: 10.1139/b01-138.
- Plant diversity and root traits benefit physical properties key to soil function in grasslands. (2016). doi: 10.1111/ele.12652.
- Crop diversity facilitates soil aggregation in relation to soil microbial community composition driven by intercropping. doi:10.1007/s11104-018-03924-8.
- Yield of binary- and multi-species swards relative to single-species swards in intensive silage systems. (2020). doi: 10.2478/ijafr-2020-0002.
- Species interactions enhance root allocation, microbial diversity and P acquisition in intercropped wheat and soybean under P deficiency. (2017). doi: 10.1016/j.apsoil.2017.08.011.
- Intercropping enhances soil carbon and nitrogen. (2015). doi: 10.1111/gcb.12738
- Mixed Cropping and Suppression of Soilborne Diseases. (2010). doi:10.1007/978-90-481-8741-6_5.
- Designing intercrops for high yield, yield stability and efficient use of resources: Are there principles? (2020). doi: 10.1016/bs.agron.2019.10.002.
- Higher plant diversity promotes higher diversity of fungal pathogens, while it decreases pathogen infection per plant. (2014). doi: 10.1890/13-2317.1.
- Can legume companion plants control weeds without decreasing crop yield? A meta-analysis. (2017). doi: 10.1016/J.FCR.2017.01.010.
- Effects of plant diversity on soil carbon in diverse ecosystems: a global meta-analysis. (2020). doi: 10.1111/brv.12554.
- Soil carbon sequestration accelerated by restoration of grassland biodiversity. (2019). doi: 10.1038/s41467-019-08636-w.
- Integration of Crop and Livestock Production in Temperate Regions to Improve Agroecosystem Functioning, Ecosystem Services, and Human Nutrition and Health. (2019). doi:10.1016/b978-0-12-811050-8.00015-7.
- Organic amendments increase crop yields by improving microbe-mediated soil functioning of agroecosystems: A meta-analysis. (2018). doi: 10.1016/j.soilbio.2018.06.002.
- Temperate agroforestry systems provide greater pollination service than monoculture. (2020). doi: 10.1016/j.agee.2020.107031.
- Wildlife-friendly farming increases crop yield: Evidence for ecological intensification. (2015). doi: 10.1098/rspb.2015.1740.
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