The bean crop has been made more attractive to growers in recent years because of the supplementary payment to support the production of up to 12,000ha of protein crops. This can be paid for the production of either beans, peas or lupins, but the payment will be diluted if the area grown exceeds the target area.

Of these, beans are the most appealing because they are more easily harvested compared with peas. However, the potential lateness of harvest reduces the appeal of the crop for growers who wish to plant winter crops.

For this reason I have been asking for some time about the potential to harvest this crop as moist beans either for crimping or as whole-crop, where the full plant is taken as silage as with whole-crop maize or cereal.

The whole-crop option would mean that harvesting is done with a silage outfit, which means that the combine can be put away once the last of the cereals are harvested. The challenge has been the lack of information on whether ensiled protein crops can be successful and still deliver a good-quality protein and starch feed to animals, specifically ruminants.

Benefits of legumes

Leguminous protein crops produce their own nitrogen and so are cheaper to grow as they save on expensive nitrogen. But they do need good soil fertility, so phosphorous (P) and potassium (K) remain essential inputs. But, as with most spring-sown crops, it is better to grow them in a fertile soil rather than in a low-fertility field with a lot of applied P and K.

All leguminous crops provide the added benefit of leaving residual nitrogen in the soil, which should reduce the need for applied nitrogen to the following crop. Leguminous crops also provide the potential to grow higher yields in the following crop, which can also have premium uses such as seed. Having a non-cereal crop also provides an opportunity to target difficult grass weeds that may be building in fields.

The combined benefits from protein crops reinforce the need to cost all of the benefits associated with rotation gross margins at farm rather than crop level. That said, it is still important to produce good yields on an annual basis.

One other benefit is that every acre growing a protein crop should have a ready market, while every acre that produces a cereal crop is merely adding to the existing surplus, which is pressurising prices. While what we do in Ireland has no tangible consequence on world market prices, it can affect local prices, especially where there is a real demand for native protein.

Protein crops also help with greening in that they are one of the three crops required on the farm and they also count as ecological focus area (EFA) on every application.

These two reasons were also responsible for driving up the area of protein crops in 2015, but with many growers now aware that they can meet their EFA obligation without growing beans, it remains to be seen what will happen the protein area in 2016.

Good soil for productivity

In my opinion protein crops, and specifically beans, are likely to benefit even more than cereals from being grown in a good healthy soil situation. And this is key to their successful production in a rotation. So, as with cereals, the benefits of having your soil in good chemical (fertility), physical (structure) and biological (organic matter for to feed the soil biology) condition is very important for productivity and will show across the full rotation.

For the past few decades the price paid for beans in particular showed a significant premium over barley – normally €30-€40/t. However, ration manufacturers suggest that this over-valued the feed and, with supplies increasing considerably, that this level of premium cannot continue.

This opinion was seen as an attempt by feed manufacturers to claw back the price when growers were receiving a payment per acre to support the production of native protein.

However, with €135/t being a common price for feed barley this year, the equivalent price of €170/t for beans still represented a price premium of €35/t over barley. And if growers can choose their fields wisely, this crop can still provide a sensible return as a standalone crop with knock-on benefits throughout the rotation.

Systems that allow early harvest: Moist conservation systems

So can we consider usage systems that will enable beans to be harvested earlier to get fields cleared in time for replanting? Teagasc recently produced an update on the value of the crop in diets and this made reference to local and other work on moist conservation options for beans.

Beans, or faba beans to be more precise, are generally stored dry. They must then be processed in some way, such as cracking, rolling, coarse grinding or steam flaking, prior to feeding to ruminants. However, wet beans can also be stored for extended periods through drying or treatment with agents such as propionic acid or mould inhibitors.

Moist beans can also be ensiled, with or without physical processing pre-ensiling. This process can also be manipulated by treating the ensiled crop with additives that restrict or enhance fermentation.

A Teagasc experiment examined the effects of crimping and additive treatment of beans. The beans were harvested at high moisture content and then ensiled. The bean crop used had a yield of 4.9t/ha and whole or crimped beans (751g DM/kg) were ensiled for 160 days either without additive or following the application of either acid, urea, Lactobacillus buchneri or Lactobacillus plantarum plus Pediococcus pentosaceus based additives.

These beans, conserved successfully, had limited fermentation and in-silo losses and were relatively stable, aerobically speaking, during feed-out (Table 1). In this trial each additive had its unique influence but no single additive improved all traits.

This study showed that beans harvested at high moisture can be efficiently conserved by ensilage, resulting in the retention of their nutritive value with minimal quantitative losses. However, it is still important to keep the face of the feed pile neat and tidy during feed-out.

This would also require good compaction of the crimped beans during ensiling. However, while it is possible to successfully ensile crimped beans, it may be less easy to harvest them. It can be very difficult to harvest immature beans with a combine as green stems can cause problems on the straw walkers, grain pan and sieves, an green beans can be messed up by augers.

Whole-crop beans

Faba beans can be harvested as whole-crop and ensiled – whole-crop includes all parts of the plant above a 6-10cm stubble. Whole-crop yields have been recorded as high as 9-10 tDM/ha, but much lower yields have also been reported. The dry matter (DM) yield of whole-crop increases rapidly as the bean crop develops through its growth stages. This is shown in Table 2, with results from a crop in Wales which was harvested after 10 (first pod set), 12 (pods fully formed) and 14 (pod fill) weeks post planting on 29 April.

The composition of the yield will vary due to the contribution of the different plant parts to whole-crop yield. This will change as the bean crop advances through its growth stages. Table 2 shows that this is primarily down to a reduction in the percentage of leaf, which coincides with an increased contribution from pods.

Whole-crop beans usually have relatively low DM and water-soluble carbohydrate (WSC) concentrations and sometimes a relatively high buffering capacity (Table 3). These can make a crop difficult to preserve, so wilting or treatment with an additive that will secure a lactic-acid dominant fermentation is recommended. But it is important that the crop not be contaminated with soil so successful wilting could be difficult. A range of different pre- and post-ensiling silage values are shown in Table 3 from different researchers.

The generally low DM concentration of whole-crop beans results in a significant effluent risk . That said, whole-crop bean silages are usually relatively stable (slow to heat or become mouldy) when exposed to air during feed-out. In general, legume silages are regarded as being aerobically more stable than whole-crop cereals such as maize but care is still needed during feed-out.

Research findings from elsewhere indicate that whole-crop beans tend to have a high crude protein concentration but that energy content is more variable. However, rumen DM degradability, neutral detergent fibre (NDF) and crude protein, all decline as bean crops mature. Intakes have been found to be comparable to those for forage pea silage and higher than for a grass-legume silage. And performance in dairy cows was found to be as good from whole-crop beans as from a grass-legume silage.

Research from Scotland indicates that the best time to harvest whole-crop beans is when pods are fully formed and the beans are pliable with a rubbery texture.

The impact of harvest timing on quality can be seen in Table 4.

The crop options

A few comments on the individual crops that can be grown for the protein crop payment – beans, peas and lupins. Each one may have more or less appeal on individual farms.

Beans: The performance of this crop in 2015 was generally excellent. However, yield levels at farm level had been quite variable in the previous years. Beans have two main challenges – they really need to be sown early, with February or early March being preferable, and they ripen relatively late for combine harvesting. They can also be very subject to diseases such as chocolate spot and ascochyta.

While beans can be grown anywhere, this crop is better suited to heavier moisture- retentive soils and the pressure from chocolate spot tends to be higher close to the coast.

Beans can be planted in either winter or spring, or we can even sow a spring variety in winter. Late autumn planting will bring forward harvest date but only slightly. Autumn drilling adds to the crow risk during establishment, the difficulty of weed control and possibly the threat from chocolate spot.

Peas: This crop has been widely grown for many decades in Ireland but production is better suited to light land for earlier drilling and also to areas with lower rainfall risk during harvest. Harvesting is a major concern with peas as it may be necessary to stop harvesting other crops when a suitable day arrives to harvest peas.

Peas can be planted later than beans and they are harvested much earlier, generally end of July or early August. Disease can also be an issue, but lodging, pigeons and harvesting are major problems. Being able to conserve the crop by ensiling could add to its appeal as a source of animal protein.

Lupins: This is not a widely grown crop but it is a good source of protein. There have been crops grown in the past and there were some grown this year. Lupins are also a leguminous crop but they have one major practical difference – the pods are carried on the top of the plant.

Lupins can grow well in this country but they have difficulty maturing for harvest. For this reason, it is may be best suited for use as a whole-crop rather than grain. The fact that pods are carried towards the top of the plant, allows a grower to use cutting height to fine tune the material put into the pit.

This gives the grower/user the ability to alter the amount of vegetative material in the silage to control its quality specification.