Arable Matters: Quickening the pulse of an old has-bean …

This week, they were credited with having an incredibly bright future, both for farmers who want to grow a sustainable, diverse rotation, and for consumers seeking a versatile, protein-rich food with multiple health benefits.

We heard that a wider adoption of these crops – which have much lower fertiliser requirements than other crops as they can fix their own nitrogen – would fit 'hand in glove' with the desire of Scottish and UK governments to take a greener approach to farm policy.

At least that was the message being pushed by Roger Vickers, chief executive of the Processors Growers and Research Organisation, probably better known as PGRO, the non-statutory levy body which has long been the UK’s centre of excellence for pea and bean crops.

“The world of legume research, innovation and trade is small compared to many other crop types and reflects relatively low current commercial values and investments surrounding legume crops,” said Mr Vickers, who called on growers to sign up to a Europe-wide initiative to share information and spread understanding of the growing of these minority crops.

The project is to be delivered by experts from across Europe with the aim of unlocking the potential for greater production across the globe through a producer network to promote the crops by linking industry with researchers, policy makers, civic organisations, brokers/traders and consultants throughout the continent and further afield.

Now I’ve always loved the possibilities offered by legumes and pulses, driven first and foremost by the prospect of saving ourselves the often outrageous price of nitrogen fertilisers by growing a crop which can fix its own.

Can we get it right?

So, it was also interesting to read the piece in last week’s paper about another group being set up in Scotland to promote a wider uptake of peas and beans – although I suspect that increasing the area we currently grow by a factor of 15 might be a bit of a tall order in the short term.

But while the ability to fix its own nitrogen and save some of the fertiliser costs – not only for that crop but also for the cereal crop following the break – has always appealed to me, the current push to be green, and to focus on sustainability could actually mean that the time has come for a greater uptake of these useful crops.

One of the biggest sources of greenhouse gases in the arable sector is nitrous oxide. It's a gas which is around 300 times more potent in global warming terms than carbon dioxide and manufactured nitrogen fertilisers are a major source of these emissions, especially if it’s spread when its either too wet, or too cold for the plant to use it up.

Reducing the emissions of this gas will be a key area of focus when the proposals for the arable sector’s climate change policy are revealed. So anything, like growing legumes, which can cut back on what can be not only an expensive waste but also a detriment to the environment, is likely to be 'a good thing'.

Fertiliser and GHGs:

Another issue coming into play here is the surprising fact that the farming sector currently escapes being 'charged' with the emissions from the heavy calls on fossil fuels which go into manufacturing synthetic nitrogen fertilisers, through the Haber Bosch process. Under the current auditing procedures for GHG emissions, they are allocated to energy use in industry, rather than in agriculture.

In this respect the our constant clamouring for a fairer auditing procedure than the one currently used by the Intergovernmental Panel on Climate Change (IPCC) could actually backfire if this additional allocation of emissions was heaped on top of us.

Now the details of the true extent of nitrogen fertilisers which would be saved by changing over to growing more legumes are a bit sketchy and remain open to a bit of interpretation – but Climate Exchange Scotland, the country’s centre of expertise connecting climate change research and policy – took a stab at this in a briefing paper they drew up.

If a legume is grown in place of another crop as part of a rotation and with no added fertiliser, the organisation puts the savings in terms of fertiliser-offset in that particular year at around 100 kg/ha for a spring cereal, 180 kg/ha for a winter cereal and about 200 kg/ha for winter oilseed rape.

Additional benefits include the potential availability of nitrogen to the following crop, thus reducing further the need for synthetic nitrogen fertiliser which could be by as much as 50-100 kg/ha nitrogen. However, Climate Exchange admitted that the ability to calculate total fixation and residual nitrogen in Scotland’s soils and climates with any great accuracy is currently a bit on the limited side.

But while we’re on about sustainability, you could argue quite strongly that growing legumes in the UK could knock a serious hole in the amount of protein crop – mainly in the form of soya – which is imported into the UK, most of which is used to feed livestock.

By displacing crops which have a reputation for being cultivated in parts of the world where there has been major deforestation, a home-grown legume protein source would probably do a lot of good for the reputation not only of the arable sector, but also for livestock producers as well.

Getting above the average:

The Climate Exchange paper also highlighted the fact that there was considerable potential for legume yields to be increased above the sort of average figure currently achieved, although it does admit that the evidence shows that annual yields are variable across Europe – a fact which they admit suggests low resilience of the crops in the face of unusual weather.

One of the main constraints on legume production in Scotland is probably, as suggested in the paper, the absence of processing facilities. There are no dehullers, only one miller (small scale and pea mainly) and no dry or wet-fractionation facilities to separate pulses into their protein and starch components.

But legumes have been widely grown in Scotland for quite some time. Crop census data records going back to the 1850s suggested a systematic decline in cropped legume area to the present day and with less than 1% of cropping land growing grain-type legumes in Scotland, the area is pretty low by global standards.

Of course, grain legumes aren’t the only ones we grow. Forage legumes, in the shape of both red and white clover, are widely used in grass mixes and there’s been a fair move towards relying on this to a greater or lesser degree in many silage and grazing systems.

Growing peas and beans for freezing for human consumption is also pretty big business in Scotland, with the sight of viners moving from field to field over the summer months being a common occurrence in many of the country’s arable areas. Also growing legumes as veg is an important part of the rotation in many, more favoured areas.

Growers can show the way ...

All the same though, major brownie points to the group of farmers growing peas, beans and lentils who have got together with processors, buyers and researchers to take more Scottish, locally grown pulses to market.

For, with legumes offering a win:win situation with both financial and environmental benefits what’s not to like?

Well …

A large proportion of the arable sector probably still bears the mental scars of trying to make the most of these crops at one stage or another.

Certainly backed up by supposedly lower growing costs and the odd foray by the EU into a protein supplement payment to encourage wider uptake of legume crops, many of us have added them to our rotations in the past to try them out.

We’ve been amongst that not so merry band on several occasions – with early forays into combining peas yielding mixed success, ranging from reasonable crops to downright disasters, where crops wallpapered to the ground yielded trailer loads of mushy peas which went into the drier in a single, glutinous lump.

And while growing the crop in a mixture with spring barley to keep it on its feet might have given some of the benefits of pea-sticks, difficulties in weed control in such a mixed crop ensured that the resulting animal feed was about as botanically diverse as it was possible to be.

Later attempts with field beans yielded a similarly mixed set of outcomes, with pretty good yields one year often followed by another in which damage limitation salvage operations were undertaken literally months after the rest of the harvest had been finished.

As often as not, the damage limitation and salvage operations extended beyond the field in which they were grown, focusing on the innards of the poor combine which had struggled manfully to finish the task.

Then there was the drying! Two, three or sometimes even four times of going through the process to get the moisture down to anything approaching a level at which the crop could be sold.

Sadly, the last few points are only likely to get worse as, with the remaining total herbicide tool, glyphosate, on the slippery slope to extinction, we are slowly and inexorably moving towards having no desiccants to dry the crop out a little before trying to harvest it.

Finding new markets:

Of course, there is also the interesting job of actually finding a market. It doesn’t help that the advisory services of old tended to denigrate the poor protein content of beans and peas when compared with the quick fix of imported soya – so there wasn’t a big uptake from feed manufacturers.

While the density of beans seemed to find favour in the manufacture of fish food for salmon at one stage, even that market seems to have run out of steam.

All that said, though, with the proper recognition of the benefits of the legumes symbiotic relationship with soil rhizobia resulting in nitrogen being fixed for free, there has to be some future in their adoption.

Current scientific consensus also believes that legume yields are only around one-third of their theoretical potential – so there’s considerable scope for varietal and management improvements.

Therefore, if we could develop that, in combination with breeding varieties which were better suited to the Scottish climate and get some decent markets developed, then that might be enough to quicken the pulse. Even for an old has-bean like me.