Flooding, maize and undersowing.

It has been raining a lot throughout England and Wales just recently. According to the map below (H/T Phil Latham) parts of Devon, Dorset and throughout the Midlands, there has been in excess of 55% of the average rainfall for November, in just three days.


Inevitably, there has been debate about how much of the flooding is down to wicked farmers growing horrid maize to feed their cattle. Some of this debate has been quite lively and extended between Phil Latham (angry dairy farmer), Miles King (botanist and ‘boring ecotroll’) and Phil Brewin (waterlevel manager and freshwater ecologist). It has been entertaining to watch.

Normally, my default position is to fly to the defence of farmers because I feel strongly that they get a rotten PR deal from the media, which tends to broadcast the eco-nuttery of George Monbiot without balancing it with any common sense from actual farmers. But on this occasion, Miles suggested that the problem of run-off from maize stubble can be mitigated by undersowing grass which will stabilise the soil over winter and the high risk period. For his part, Phil Latham wondered about the yield reduction caused to the maize by the undersown grass.

I have a lot of sympathy for the undersowing idea, so I shall explain. Some years ago, I had a grazing licence on some land near Kingston Maurward near Dorchester. So on a daily basis, I used to drive out, using the back road between Tincleton and Dorchester. (Miles  might know this road). Along this road are a number of farmers, some of whom grow maize for their cattle. One winter was especially wet and the maize stubble became waterlogged, compacted and then shed the water with a rush. Great gullies were cut into the soil and large amounts of sediment were dumped onto the lane as well as flooding it. This confirmed my view that leaving bare soil over winter was not only environmentally damaging, but also a waste of good agricultural land, because the land is doing nothing for six or seven months of the year.

I suspect that conventional farmers have been slow to adopt the idea of undersowing maize because it is yet another operation and there are valid fears of reducing the maize yield. Farmers have enough to do already without giving themselves extra work. If they can get away with cutting the number of operations on a farm whilst maintaining margin, then the minimum amount of work is a sensible strategy.

A little time spent on Google reveals that the practice of undersowing maize with various grass and grass/legume options is now common practice in Denmark. It is under trial for the purposes of flood prevention in Wye and Usk. I have no doubt that farmers in the catchment of the Somerset Levels will be encouraged to do something similar. I certainly hope so.

The characteristics of the late growing season demanded by maize (it needs a soil temperature of about 10 degC to germinate) mean that it provides a long window of opportunity for farmers to get a catch crop in between their main crop. The grass can be grazed or silaged and offers an effective increase in the quantity of dry matter produced from a given area of land. In addition, it can be viewed as a green manure (so beloved of organic farmers) with the root mass being returned to the soil to provide the basis of an improved soil structure – rather than an increasingly depleted one. Furthermore, the catch crop of grass does not need inputs of N, because it is helping to restore the soil Nitrogen balance after the high inputs of the maize crop. In the end, this system seems to me to provide the farmer with lower costs (easier cultivation), better compliance with environmental standards in cross compliance; lower risk of run-off during periods of high rainfall; and above all else, the opportunity for additional income for the farm.

There will be times and some farms for which this system is difficult or expensive to operate, but I suspect that reluctance in take-up of this idea is more due to caution on the part of farmers, than any real objection. So it would be good to see this happen across the country.

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