Water managements a necessity not a luxury
Water managements a necessity not a luxury
After the wettest autumn,
winter and spring on record
how can arable farms
protect their fields from a
repeat performance?
Tim Isaac, of Colchester-
based surveyor Fenn Wright,
provides some pointers
BRITAINS wettest winter since records began wrought havoc on arable farms across the country, NFU estimates suggesting financial losses running into hundreds of millions of £s.
For some growers the deluge meant direct crop losses. For others it brought delayed drilling, wasted cultivations and severely disrupted rotations. Severe erosion, removing both soil and nutrients, was an added complication.
That all serves as a reminder of the importance of controlling soil water. In the UK we have cold, wet winters with little growth and excess water, and hot, dry summers with maximum crop growth and insufficient water. Good water management is a necessity, not a luxury.
Underground drainage
Most of the good agricultural areas in the UK have had permanent drainage systems installed since World War Two. Those will work efficiently for at least 50 years, provided they are well maintained.
Check your system is still operating properly by mapping areas hit by ponding and outfalls that did not produce the expected volume of water. Keeping outfalls clear is essential to avoid silt backing up and blocking pipes. Use obvious markers to reduce the chance of accidental machinery damage.
If pipes are badly broken, new ones may be needed. A permeable backfill in conjunction with mole-ploughing may also be appropriate in heavier soils.
Landlords and tenants should check the terms of their agreement before considering any drainage improvement schemes.
Ditches
Many fields have ditches, but how many of those carry water as they should? The modern practice of flailing field margins is easy, but the flailed material usually ends up in the ditch. Over time, and with natural silt deposition, ditches become shallow and often block where they run under bridges.
Ditches must be treated as an integral part of the farms drainage system. If they are not working, then neither will the rest of the system.
Winter maintenance should be done every three to seven years on rotation. Specialist equipment hire costs £15-£35/hour (excluding labour).
Be aware that there is legislation under which landowners can force neighbours to improve inadequate ditches.
Mole ploughing, subsoiling
To move water through the soil requires a network of cracks and fissures, which can be created artificially. But it is essential to use the right tool at the right time for the soil type concerned.
Experience shows soils with clay contents down towards 25% will only hold a mole channel for four to five years. So an area of the farm will probably need moling every year to a depth of 500-600mm depending on the situation.
Subsoiling is also important, particularly if no-plough systems are used. Use a spade to identify problem areas and as a guide sub-soil in line with the rotation at a depth of about 400-500mm. It is important not to re-pack the soil shortly afterwards.
The effectiveness of both moling and subsoiling will be minimal if they are carried out when soil conditions are unsuitable and will have an adverse effect on structure if this is the case.
Other cultivations
Bear in mind that every field operation affects the movement of water in the soil, even non-cultivation passes. Creating a coarser surface tilth and partial straw incorporation helps control run-off, while direct or low-till drilling helps preserve natural soil structure and encourages water to percolate through the profile.
Tramlines also deserve consideration, since they can act as water channels. Correctly positioned they help; in the wrong places they certainly hinder.
When ploughing on slopes try to ensure soil is thrown uphill to reverse the downwards soil creep.
Environmental schemes
Under the England Rural Development Programme there are grants available for works with clear environmental benefits, some of which can be used as part of an overall water management plan.
One example is sowing low-lying, shaded, heavy clay areas with permanent grass. That can attract grant payments higher than the net return from forcing a crop in and watching it suffer from flooding.
Alternatively, on very large, rolling arable fields, slope length can be reduced by establishing grass strips across the slope. These can incorporate shallow channels leading to existing waterways, so they help divert run-off and stabilise the soil without interfering with field operations too much.
There are also grants available for pond creation under the Countryside Stewardship Scheme. If an area of waste ground exists adjacent to an arable field, consider digging a pond to trap excess run-off.
Water conservation
Lastly, why not turn an enemy into a source of income? Water is a valuable resource, so if you have excess winter rainfall, talk to the Environment Agency about constructing a reservoir, particularly if flooding is an annual problem.
You could stock the reservoir with fish and let it. Alternatively you could irrigate and enhance the value of your own crops, or sell the water to a neighbouring farmer to enhance the value of theirs. You may be thankful for such a resource when we get that long, dry summer. *
Flooded fields delayed crop drilling and destroyed many crops already in the ground. Action over the coming months might help avoid a repeat if wet weather returns next winter, says Tim Isaac.
WATERISSUES
• Loss of crops and soil from widespread flooding.
• Have a planned approach to water management.
• Keep water moving.
• Maintain drainage systems.
• Consider cultivation strategy.
• Take advantage of environmental schemes.
• Do not forget water is a valuable resource.
Better water management
Operation Typical cost Possible grant aid
Installing new pipework £1000-£2000/ha None
Maintaining/creating £1-£2/m Under one of the ERDP ditches Schemes if environmental benefit can be proved
Mole Ploughing £45-55/ha (add up to None £25/ha for contractor)
Subsoiling £28-£38/ha (add up to None £25/ha for contractor)
Establishing grass £70-£350/ha Under one of the ERDP strips schemes, such as CSS
Creating ponds Huge variation depending Under one of the ERDP on circumstances schemes, such as CSS
Constructing reservoirs £1-4/cu m. Under one of the ERDP Schemes
Clean ditches help prevent floodwater; blocked ditches do not.
Do not let this happen again. Soil management techniques can help avoid a repeat of the widespread flooding and severe erosion caused by unprecedented winter rainfall. Tramline placement also merits care.
Turn floodwater to profit by investing in a winter storage reservoir. It can be stocked with fish and let, or used for irrigation on your farm or a neighbours.