In orange you will find my comments putting this opinion piece from Mr André Pochon in a welsh context perspective.
In Brittany algal blooms have been associated with the development of both intensive inputs heavy husbandry (cattle, poultry, pig) and the uptake of maize, replacing grass as the main forage crop. The nitrate concentration skyrocketed from 2mg of nitrates per litre in the 60’s to 50-100mg/l in the 70’s-80’s. The successive plans to comply with the nitrates directive (from 2004) have gradually reduced the impact of the intensive high inputs units. Increasing slurry and muck storage, prescriptions on slurry and muck spreading, the mandatory planning of nitrogen spreading on each farm, the processing of slurry and muck, or their export all played a part in it. On the flipside ones tried to match more finely the needs of the crops with fertilisation through the 6th action plan [1]. Mandatory cover crops to catch excess nitrates over autumn and winter was another part of this plan.
[1] Yes in Brittany we are at the 6th action plan showing you that all problems are still not solved reinforcing the stance of Mr Pochon.
"Marée verte" - algal bloom in Brittany have plagued some of the "shallow coastal bay" close to heavily stocked areas, those heavy deposits have been associated with sanitary issues due to the release of toxic H2S. This is on top of eutrophisation of some watercourses and ponds. The supermat - wikimedia commons - CC 2.0
But today, the main cause of algal bloom is clearly the substitution of grass by maize [2] to feed cattle. One of the main reasons being that Maize contrary to Corn will not lodge. Indeed generous amount of slurry can be spread and help to deal with excess nitrogen in the stores; for many years maize has been a slurry dump yard receiving nearly 5 times as much than it needs. With today’s rules, this is not a possibility anymore, despite this the amounts of slurry spread often go over the allowance. Simply put it is hard to control what is spread [3].
[2] Maize is used a lot more in Brittany than in the UK.
[3] The slurry spread can differ heavily in terms of composition, dry matter, N/P or K content...
On Maize fields, manure is mostly spread before sowing, between March and the beginning of May. But the full growth phase of Maize happens between July and August [4]; If it rains heavily between March and July there will be some nitrates leaching into ground water and waterways.
[4] The needs of the plant and the times when the nutrients are brought do not match. On grazing platforms of cattle farm it is often quite difficult to spread manure during the vegetative growth period due to bio-security problems.
Likewise from September onwards Maize’s vegetative growth is finished and grain’s maturation takes place. There is no more nitrogen absorption from the plant after mineralisation of it. This unused nitrogen will again leach into ground water or waterways.
In Brittany contrary to Wales there has been a massive adoption of Maize (fodder and grains) with the implementation of the 20th century agricultural revoltuion for both for ruminants and other livestocks (in Wales this was done through grass). Maize represents more than 75% of the fodder crops according to the DRAAF stats. (LT 2019)
We mentioned the importance of nitrate cover crops in order to absorb the excess nitrates of the soil in autumn and winter; those excess nitrates are linked to the process of mineralisation itself linked to autumn rains. The widespread adoption of cover crops has considerably helped reduce the nitrates levels in waterways. After the corn harvest, cover crops are sown in July or August. Thus they are in full vegetative growth in autumn and winter therefore absorbing available soil nitrates. Unfortunately, maize harvested in October [5] does not allow the following cover crops to reach a full vegetative growth during winter. The high level of nitrates measured show how much will be washed away.
[5] In Wales the problem of Maize is even worse given the shorter growing season.
Nota: In Brittany the number of pigs and poultry much surpass the number of other kind of husbandry. Those are the main users of the Maize being grown before dairy cows, but fear not the problem is quite similar on dairy cows.
However when it comes to buildings, straw bedded pigsties should be allowed and supported by devolved authorities and those on slats converted onto straw bedding with local subsidies. This conversion is capital for several reasons:
- A finishing pig on straw bedding will produce 13.5 kg of nitrogen while one on slats will produce 27 kg of the same substance; therefore the acreage needed to spread the slurry is halved.
- Nitrogen in straw based manure is under organic form; it actively contributes to the increase of humus proportion, therefore increasing its fertility and favouring carbon sequestration (contributing to the fight against climate change).
- Straw-bedded pork fetch a higher price, have a lower mortality rate and lower veterinary bills. A 50 sow breeder to finisher farm with straw buildings will provide a higher income compared to a 100 sow one with slats buildings. Produce less but produce better.
Grass field in France (Normandy) in those areas specialisation of farms has proved to be a challenge for some environmental parameters (Lenormand, 2017).
Today in Brittany the high acreages of maize are the main cause of our nitrates rates oscillating between 30 to 40 mg in our waterways. Without a steep reduction in the Maize acreage in Brittany, algae blooms will keep swamping up our coasts. In Lannion’s bay where grass has been substituted back to maize improvement have been witnessed in the nitrates levels. This result has also been witnessed on farms that have adopted the local agri-environmental mixed farming scheme where the forage production is grass-based. If we want to end the algae blooms, it is key to feed our cattle and ovine grass, from little fertilized pastures based on white clover.
[7] Looking at this a welsh person would say that in Wales there is very little straw being grown, mixed farming systems are the key as explained after.
Why hesitate when this systemic change would lead to an increase in farmer’s income? Obviously it will still be necessary to keep track of nitrogen exchanges on farms. The most efficient way to do this in France is to base ourselves on the entry-exit nitrogen system (INRA Quimper). With a grass-based mixed farming systems, porks on straw-bedding, free-range poultry; Brittany will be one of the richest areas of France with numerous and flourishing farmers, while getting rid of algal blooms. It is a deep systemic change for our farming systems. The CAP reform as well as public opinion through mass medias can help promote this revolution.
[8] For Wales the consequences are also important, as nitrogen has been billed a major problem it needs to be addressed from a systemic change point of view as per Brittany’s case described by Mr Pochon.
