Extreme weather means good land drainage is vital

Inadequate drainage can result in growers missing key fungicide timings or lead to uneven crops that fail to reach their full yield potential, as Philip Case found out.

A recent trend of extreme dry and wet spells of weather in the UK means growers are taking land drainage more seriously, according to one drainage contractor.

The scale of the problem was highlighted in the autumn and winter of 2010 when wet weather hampered the plans of many East Anglian farmers, whose dated drainage systems started to fail, says Tim Sisson, managing director of land drainage specialists William Morfoot, based in Norfolk.

“Growers were unable to get on to their land to carry out routine arable operations, such as applying fertiliser and spraying crops at the optimum times,” he says.

“Water was getting locked in the land and could not drain away. Many were wasting their time spraying as the chemical was just sitting there in the water.”

Mr Sisson points out the many benefits to having well-drained land.

“Good land drainage can improve the yield potential of land, especially poorly drained areas of fields, which are prone to waterlogging,” he says.

“It also dramatically improves the field recovery time after prolonged or heavy spells of rain and provides optimum and uniform growing conditions for the crop during the wetter periods of the year.”

By maintaining an efficient field and farm drainage system, machinery is better able to travel across land while reducing the problems associated, such as tractors or combines getting bogged down in wet patches and rutting in fields, he adds.

Better drainage can also improve the timeliness of all arable operations, which can be critical when considering harvest windows and certain spray/fertiliser applications, Mr Sisson says.

“Growers may be looking to spray wheat crops at the critical T1 or T2 timing, but if they have a wet period at that time, their spraying operations can be delayed,” he explains.

Mr Sisson says the rising value of land means growers should take steps to make sure that it remains in good condition and at its productive best, especially considering the recent trend of extreme dry and wet weather periods, with wetter Augusts in particular.

High input costs associated with sprays, fertilisers and seed means that the soil structure in the field must be in peak condition if growers are to make the most of current high crop prices.

Drainage costs

Field drainage carried out by a professional contractor is not cheap, admits Mr Sisson, typically around £1,730-£2,225/ha to drain on a comprehensive basis.

But he points out that land drainage, when installed professionally, will improve the yield potential of the field for a minimum of 20-25 years on fen soils and for considerably longer on stable upland soils.

“You can spend £100,000 on a new tractor and its value will soon depreciate,” he says.

“But a good drainage system will carry on returning investment year-after-year through higher yields and ensure better timeliness of operations.”

With land values remaining at record levels – buying an acre of land in East Anglia can cost in excess of £7,000 – carrying out land drainage will increase the value of land further still, he adds.

Assessing need

“Growers know their land better than anyone and if they feel their machinery is getting stuck too often, their drainage may be inadequate,” says Mr Sisson.

“Alternatively, they may have noticed a significant decline in crop yields from poor-performing fields. Land drains do have a fixed lifetime and if a drainage scheme has been in place for decades, it may need to be looked at with a view to renewing some of it.”

“We will generally walk these fields with them and carry out a full field survey to make sure their drainage system is designed in the best way to give them the most benefit.”

Drainage options

Comprehensive land drainage

Standard method of drainage using a trenching machine to install drains within a field spaced 20m apart. Using a professional contractor to complete the works will ensure drains are correctly installed, as getting it wrong can lead to new wet areas.

Remedial land drainage

This enables landowners to target particular wet patches within a field and requires the use of a trenching machine.

Secondary drainage methods, such as mole drainage

This is carried out on a field that already has a comprehensive land drainage system in place. This method drags an implement through the soil to create a cavity for water to run into the drains. It is best suited to clay-based sub-soils and heavy-land farms.

Infrastructure-related drainage

Using an excavator, this process allows drainage water within ditch systems and watercourses to flow in the correct direction, therefore, draining water away from the fields. Having appropriately maintained ditch systems is vital for any farm that is experiencing drainage-related issues. 

Case study: Poul Hovesen, Norfolk

Norfolk grower Poul Hovesen believes farmers should allocate about 2% of their annual turnover to land drainage improvements.

Since he started investing in drainage improvements 10 years ago, crop yields at Manor Farm, in Salle, have soared by 20%, Mr Hovesen says.

“I cannot claim that all of our yield increase is exactly related to drainage, but the efficiency has gone up a lot – it’s a combination of yield and efficiency,” he adds.

To date, a range of projects has been completed at the 2,000ha arable unit, including a major drainage scheme, field restructuring including hedge removal, piping and filling in ditches, cleaning out ponds and wet spot remedial work.

Yield mapping helps identify lower-yielding areas, especially in wet years, and repair work will be carried out either in whole or part fields, depending on the level of damage.

“Because of climate change and weather patterns where we suddenly get periods of continuous rain, timing of the crop establishment operation is vital,” he says.

“If field areas are lying wet, it can hold back crop establishment, which will severely upset your timings.”

Wet patches can lead to big pieces of machinery getting stuck, which can cause unnecessary delays to the farming operation and cost money.

They can also create uneven crop maturity that can delay the harvesting schedule, he adds. “If the crop does not mature evenly, you cannot harvest it at the same time. But more importantly, the quality is uneven.”

• Farming in the Fens has always involved a battle with water, and good drainage is vital when your fields are 3m below sea level. Watch the video below by Farmers Weekly news reporter Johann Tasker looking at a trencher in action.

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