The recently announced Department of Agriculture, Environment and Rural Affairs (DAERA) Protein Crop Scheme, and the financial support it offers, has renewed interest among Northern Ireland’s tillage farmers in the growing of peas, beans and lupins.

This was the focus of a recent webinar held jointly by DAERA, AgriSearch and AFBI.

The three crops eligible for the scheme are peas, beans and lupins. Each must be grown as a single-species stand and not in mixtures with cereals or other crops, including under-sown grass.

Leigh McClean, a crops adviser with CAFRE, pointed out that for an arable farmer, protein crops may offer a useful take-all break crop option and provide a number of other benefits.

Integrated pest management

They can be used as part of an integrated pest management strategy to get on top of difficult-to-control grass weeds.

This strategy offers the opportunity to use stale seedbeds and herbicides with alternate modes of action once the crop has emerged, to counteract the development of resistance in some weeds.

Another agronomic benefit that McClean pointed out was that protein crops fix nitrogen from the atmosphere. This not only provides nitrogen for their own growth, but also leaves residual nitrogen for the following crop, reducing chemical nitrogen fertiliser requirements.

He also noted that as protein crops are flowering crops, they bring diversity to the landscape and provide a feed source for pollinators such as bees.

With protein crops, there is also the potential to spread workload: for example, spring beans may be suitable for earlier drilling than spring cereals and are later to harvest than other combinable crops.

Aspects to consider

However, McClean cautioned that there are some important aspects to consider before planting a protein crop.

The first being: do you have a market for them? On mixed farms, they can reduce the amount of bought-in protein required as stock feed.

For tillage-only operations, there may be potential to sell to neighbouring livestock farms or local feed mills, some of whom currently use peas and beans as part of their rations. 

Consideration needs to be given to harvest, treatment and storage of the crops, as harvest can be late in the case of beans or tricky in the case of peas as they have a tendency to lodge.

Nutritional value

It is also important to consider the nutritional value of any protein crop grown, an issue that was examined in a number of recent studies undertaken at AFBI.

These studies, which were jointly funded by DAERA and AgriSearch, examined the impact of including locally-grown field beans in dairy cow diets.

Conrad Ferris, a dairy scientist at AFBI Hillsborough, explained that beans were included in dairy cow diets in two separate experiments to examine the effect of inclusion level.

The maximum inclusion level in the first study was 4.7kg beans per cow per day, and this had no negative effects on cow performance. However, in a second study, beans were included at up to 8.4kg/cow per day, a much higher level than would be advised in practice.

While neither intakes nor milk yields were affected at this high level of inclusion, both milk fat and milk protein levels were reduced. Based on these experiments, maximum inclusion levels of 4-5kg field beans per cow per day are advised.

A third AFBI study demonstrated that cow performance was unaffected when either dried milled beans or moist propionic acid treated beans were offered to cows, thus providing an option for home treatment of beans.

These experiments have clearly demonstrated that field beans can partly replace some of the imported protein in dairy cow diets.