1965 was my first year at university during which I had quite an intensive course on geology. It’s a fascinating subject once you’ve remembered the sequence and dates of the different geological periods. On the course we were told about how our landscapes were formed. Over the last couple of days I’ve finally seen at first-hand a couple of the major coastal features that were used as prime examples in the lectures and which we were told we should visit. It took me 49 years to get round to seeing them! However I’m partly comforted by the fact that this, in terms of geological time, is a very rapid response.
The reason I was ‘down south’ is that I am part of a team which is trying to develop a conventional farming system in a mini-catchment that supplies a potable water pumping station. Typically, water works have carbon filters that adsorb some of the pesticides in water and also an ozone treatment in order to oxidise the remainder. Together, these two processes will significantly reduce the levels of most pesticides. However, as you may well know, metaldehyde and clopyralid (e.g. Shield SG) can survive these treatments largely unscathed. Unfortunately, at this particular pumping station they cannot treat the raw water in order to reduce pesticides. Therefore, at the input, every pesticide has to be below the Drinking Water Directive level of 0.1 parts per billion (ppb) and the total content has to be below 0.5 ppb.
Hence, there is a need to take immense care over pesticide management in this particular small catchment. There has been significant investment in farmyard facilities to ensure that where the sprayer is filled and where the pesticides and sprayer are stored are not sources of pesticides in the raw water. The next step is to ensure that pesticide use on the fields meets similar high standards.
This objective touches many farm activities; the choice of crops, the rotation, the crop protection programmes, the spraying operation, the placement of entry points to the fields and the establishment of buffer zones.
The first step has been to define which pesticides have acceptable physical/chemical properties and doses that should mean that they can be used with little concern of them exceeding their content in the water, as specified in the Drinking Water Directive. This is a very complex and challenging issue as computer modelling for each individual pesticide is impractical because of a lack of knowledge on the actual ‘leaching’ routes through the subsoil to water. An additional challenge is that there must be a readily available and cheap analysis to identify them in water at levels at or below the standards set in the Drinking Water Directive. However, we’re getting there.
It’s clear that we cannot, at this stage, afford to have black-grass as an issue in this catchment. Its control would almost certainly mean that the standards pertaining to pesticides in water could not be met. Also, even without black-grass as a target, it is clear that robust weed control in oilseed rape is going to be at the least difficult and perhaps impossible.
It appears possible to have a robust crop protection programme in spring barley and probably in winter wheat. There are other alternative crops that might be grown but with some limitations to crop protection. A system is slowly being devised which may result in profitable conventional farming whilst meeting the Drinking Water Directive standards.
In this situation it’s easy to rely on the sulfonylurea herbicides which are used at a few g/ha. This may prove to be a short-term palliative but the threat of resistance occurring in broad-leaved weeds means that other groups of herbicides will have to be considered. There are one or two crops where only the sulfonylureas can be used. Hence, there has to be a rotational plan with non-sulfonylurea herbicides as the major means of weed control in other crops in the rotation.
The idea of the project is to start with a very precautionary approach and perhaps introduce more pesticide and cropping options if all goes well. It will be intriguing to see how this develops.