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23.02.15 Agroforestry - essential for a sustainable future

Agroforestry is the growing of trees or shrubs with other agricultural crops. It can range from lines of trees intercropped with a cereal like wheat, to fully integrated forest garden systems incorporating trees, shrubs and perennial crops in a self-sustaining system.

Over the last few hundred years almost all the research and agricultural effort has been focussed on annual plants, to the extent that most of the world population depends on them. This wasn’t always the case, though, and many people have forgotten that the mass growing of annuals on a field scale is never going to be sustainable because they take a huge amount of energy to grow. As long as energy is cheap and available they can continue their dominance – but it is clear now that energy is not going to remain cheap for much longer.

We need to move much more towards perennial crops – whether it be tree-based crops (for example, nuts to take the place of some of the cereals) or smaller plants – for example perennial vegetables like perennial onions. In other words a move towards agroforestry.

Perennial plants, once established, take much less work to maintain than annuals – you only have to plant once (in a long while anyway), and most plants look after themselves with far less susceptibility to pests, diseases or the vagaries of the weather than annuals. Perennial plant products are often more nutritious than their annual counterparts too, because their roots systems are larger and can get more nutrients out of the soil.

Sustainable growing requires a change in attitudes too. Agriculture has been misled into thinking that every bit of ground needs to be productive – in other words needs to have a crop coming from it.  This is never going to be sustainable. Truly sustainable growing systems must devote a proportion of the land to plants with ‘system’ functions – in other words, plants which increase the health and resilience of the whole growing system (whether or not they produce a crop). Such plants would usually include nitrogen-fixing species (to make the use of nitrogen fertilisers unnecessary), and also plants to deter pests and diseases by, for example, attracting predators of likely pests or by confusing pests with aromatic emissions.

The most sustainable systems will be closed-loop systems, where no extra nutrients are brought in and the growing system sustains itself. Forest gardens are an example of this.

Agroforestry systems are less suited to very large scale production than monocultures, so by their nature they will smaller scale – which also means that they are much more likely to be integrated far better with their local economy: crops are likely to be sold and used locally, so the mass transport of food should decrease significantly as these systems become more popular.

Agroforestry systems have many other benefits – for example wildlife value is very high, they can provide shelter and thus reduce energy usage for heating or cooling, and so on. Once understood we’ll wonder how we ever did without them!

Martin Crawford, 2015

Martin is Director of the Agroforestry Research Trust (and his books include Creating a Forest Garden (Green Books, 2010) and How to Grow Perennial Vegetables (Green Books, 2012). 


17.02.15 The potential of legume based grassland livestock systems in Europe

So for the final blog of this month, I will be looking at the potential of legumes to aid with livestock production from pasture based systems. There is a well-known debate that rears its head in the media from time to time about meat consumption and methane emissions and how we should all be reducing our meat consumption to reduce the effects of climate change and reduce emissions.

Running alongside this debate is a growing interest in the emissions from pasture based systems. At the moment, science has not advanced sufficiently to allow us humans to eat grass, and digest the fibrous lignocellulose which ruminants are able to convert into meat or milk and as such grazing livestock will continue to be part of our environment. However where we can have an impact is on how we manage that grassland to get optimal production from that pasture. Making sure that there is a balance of inputs and outputs to that grassland, ensuring adequate soil structure, as well as optimising nutrient and animal management will allow us to use that pasture to ensure efficient production.

One of the ways that grassland production can be “improved” is to include legume species within the sward. Grassland production will need to keep pace with requirements for higher meat and milk production from ruminant systems and with a changing climate. Legumes offer important opportunities for sustainable grassland based animal production because they can contribute to important key challenges by:

  • Increasing forage yield
  • Substituting bagged N fertiliser inputs with plants which are able to biologically fix nitrogen
  • Mitigating and supporting adaptation to climate change
  • Increasing the nutritive value of herbage and raising the efficiency of conversion of herbage to animal production

This blog content comes from a paper entitled “Potential of legume based grassland – livestock systems in Europe” which was compiled by Luscher et al and brings together information from a wide range of European research on different properties of legumes to assess the contribution that legumes can make to sustainable livestock production from grass. To read the paper in full please click here.

For this blog in this monthly theme of livestock diets, the bit that I will be concentrating on is the properties that are found in some legumes that suppress methane production from ruminants. Without diving into a complicated biochemistry and nutrition lecture, a key feature of legumes are the plant secondary metabolites.

There are a few legumes which possess additional features which offer promise for ruminant nutrition and health as well as reducing greenhouse gas emissions. These features include tannins, polyphenol oxidase and protease enzymes.  Sainfoin holds particular promise for alkaline and drought prone soils.

Condensed tannins are a group of fabulous compounds that are found in some forage legumes including birdsfoot trefoil. Sainfoin, sulla and the flowers of trifolium species. Total concentrations of these compounds depend on the variety, plant organ and processing methods.

The role of these condensed tannins in reducing protein degradation in the rumen is well documented. By forming bonds with dietary proteins, condensed tannins generally slow the rate of protein degradation during fermentation in the rumen, and as such will reduce losses associated with rumination. What is not yet fully understood is which types of condensed tannins create optimal degradation rates. For example, high concentrations of condensed tannins in trefoils may be too potent, as cattle cannot utilise its dietary protein fully, as such, it is excreted and results in high faecal N contents.

What does all this mean?

Grass clover mixes with 30-50% of legumes in the mix seems to be an optimal system. These yield high amounts of N from biological fixation (symbiosis), generate high forage yields of high nutritive value, which generates high voluntary intakes and livestock performance and at the same time they minimise the risk of N losses to the environment. The big challenge for legume based grassland husbandry systems however will be to maintain the proportion of legumes within this optimum range.

As a component of mixed grass legume sward, forage legumes offer important opportunities for tackling future agricultural challenges.  The great potential of legumes for sustainable intensification is related not just to one specific feature, their strength stems from the fact that several of their features can act together on different “sites” in the soil plant animal atmosphere system. The multiple advantages benefit the whole grassland husbandry system through reduced dependency on fossil energy and industrial N fertiliser, lower nitrate and GHG emissions, into the environment, lower production costs, higher productivity and protein self-sufficiency.

Legumes generate these benefits at the land management unit level, and although these benefits are brilliant, there are some limitations and further research is needed to make sure that we as farmers have all the facts and can make best use of them within our swards and rotations.

To read the full paper please click here. Are you managing to hit 30% legumes in your sward? Let us know how you manage their persistence and graze them to optimise productivity. FCCT would love to know how you manage them.

12.02.15 Soil biodiversity reduces nitrogen pollution and improves crops' nutrient uptake

Increased soil biodiversity can reduce nitrogen pollution, improve nutrient uptake by plants and even increase crop yields, according to new research.  The two-year study found that levels of nitrogen leaching from soil with an abundant soil life were nearly 25% lower than for soil with a reduced level of soil life.  Practices which enhance soil biology such as reduced tillage, crop rotations and organic farming may therefore help to reduce the environmental impact of fertilisers and improve agricultural sustainability.

Fertilisers boost crop growth by providing important nutrients. However the amount applied in modern agriculture is often far in excess of that taken up by the crops. For instance it is estimated that only half of all nitrogen applications are used by plants; the rest can be leached from fields or lost to the atmosphere as gas, causing environmental problems.

Intensive agriculture also threatens soil organisms, such as fungi, earthworms and others; in fact studies have shown that soil biodiversity is under threat in 56% of EU territory. These organisms are known to be important for nutrient cycling and there has been some suggestion that their decline may increase the need for artificial fertilisers.

In this study, part-funded by the EU project BRIO, the researchers investigated whether the abundance and biodiversity of soil organisms could affect plant growth and nutrient use as well as nutrient leaching. They filled 16 containers, each with a volume of 230 litres, with sterilised soil that was then treated with either a reduced or a high level of soil life and placed them outdoors. The containers were monitored for two years, and rotated with maize, grass and wheat crops.  Fertiliser was applied twice during the study.

What did the research find?

In the first year, nitrogen leaching was 51.5% lower in containers with higher soil life compared with reduced soil life containers; the equivalent of 150.6kg per hectare of nitrogen (kg/ha) leached from the low soil-life containers, but just 74.4 kg/ha from the plants in the biodiverse containers contained 28.9% more nitrogen, and 110% more phosphorus than those in the reduced soil-life containers.

Crop yields and plant biomass were also significantly higher in the biodiverse containers. For example, maize in the reduced soil-life containers showed yields of 33.2 tonnes per hectare (t/ha) but this increased by 22.3% to 40.3t/ha in the biodiverse containers.

In the second year the differences were not as pronounced and the only statistically significant differences were a greater biomass of wheat and higher plant phosphorus levels in the biodiverse containers. However this does not imply that biodiversity is not important in the long term, the researchers say. They point out that, in the second year, the reduced soil-life containers were invaded by a variety of soil organisms including arbuscular mycorrhizal fungi (which are particularly important for plants and nutrient cycling).

The researchers note that the phosphorus leaching was higher in the more biodiverse containers. However, this reflects increased mobilisation of this element by soil organisms, they say, which also makes the phosphorus easier for the plants to take up. As a result, relative phosphorus losses, defined as the number of grams of phosphorus leached per kilogram of phosphorus taken up by the plants, was actually 25% lower for biodiverse containers compared with the reduced soil-life containers.

The importance of soil biodiversity

Increased soil biodiversity could be an important step on the road to sustainable agriculture. Management practices known to enhance soil biodiversity, such as reduced tilling, and crop rotations could provide real improvements in nitrogen and phosphorus use efficiency.

Source: 

"Science for Environment Policy": European Commission DG Environment News Alert Service, edited by SCU, The University of the West of England, Bristol.

09.02.2015 The effect of grazing behaviour of suckler cows on predicted methane emissions

A research paper published last year in the Journal of Animal Science has looked at the effect of grazing behaviour on predicted methane emissions. This study used a computer model and a large dataset from a large scale grazing study to identify the potential impact of grazing behaviour and performance of different breeds of cattle on predicted methane emissions.

The study used GPS collars and activity sensors to monitor dairy cows that were grazing extensive semi natural grassland. The diet selected by cows of three different genotypes (Aberdeen Angus cross Limousin, Charolais and Luing) was simulated by matching their locations during active periods with hill vegetation maps.

Measured performance and activity were used to predict energy requirements, dry matter intake and methane output.

The cumulative effect of actual performance, diet selection and actual physical activity on potential methane output and yield was estimated. Sensitivity analyses were performed for the digestibility of intake, energy cost of activity, proportion of milk consumed by calves, and reproductive efficiency.

Results

This study suggests for the first time that measured activity has a major impact on estimated methane outputs. Predicted methane emissions was highly sensitive to small changes in diet quality, suggesting the relative importance of diet selection on diverse rangelands.

Extending these results to a farm systems scale, methane outputs were also highly sensitive to reductions in weaning rates, illustrating the impact on methane at the farm scale of using poorly adapted breeds on habitats where their performance may be compromised.

The paper demonstrates that variations in grazing behaviour and grazing choice have a potentially large impact on methane emissions, illustrating the importance of including these factors in calculating realistic national and global estimates.

Source: J Animal Science, 2014 Mar; 92(3): 1239 – 49

06.02.2015 Leading soil regeneration expert coming to Devon

On 21st February, RegenAG UK are pleased to bring a leading soils expert to the south-west, and at the moment there are still a few places left with funding for farmers (£48 plus VAT, thanks to RDPE/DEFRA).

Joel Williams integrates understanding of the physical aspects of soil chemistry and nutrient balancing (Albrecht style) with the biology (Soil Food Web) and will present a full-day workshop at Bicton EaRTH Centre.

If you would like to explore the potential to cheaply and easily improve soil health and nutrient availability and thereby also productivity, then registering for the seminar could be an excellent starting point. Improving soil health will of course also help with water and disease management.

For further details see the website,  - specific event page is here.

RegenAG UK acts within the UK to promote Regenerative Agriculture, which addresses the need to respond to ongoing changing conditions in order to regenerate soil fertility and natural cycles for sustained productivity and wellbeing. Collaborating internationally with like-minded organisations and individuals enables the organisation to make best practice from around the world available more locally.


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