Power harrow right option?
Power harrows – indispensable tools or expensive luxuries? Robert Harris relays one farming companys views
CHOOSING the correct cultivation equipment and tactics for a particular farm gets plenty of thought at Aubourn Farming, the Lincs-based firm which manages about 8000ha (20,000 acres).
"The use of power harrows may have simplified soil management decisions, but it can be a costly alternative in terms of both damage to soil structure and high operation costs," says managing director Philip Wynn.
Operations on the 2853ha (7050 acres) of heavy marine clay land at Willoughby Farms in East Lincs highlight the need for care, he explains. Although the soils have developed a good structure through constant conditioning, they are tricky to work. Timeliness in the autumn is vital for profitability.
"Most of the land is ploughed," says Mr Wynn. "But it is essential not to allow it to dry out. Our team of four ploughs follows the combines and is closely followed by a heavy disc and press combination. We aim to leave the land level and firm to retain moisture and allow for final seed-bed cultivations with either a tine cultivator or a Hankmo with its star-shaped discs.
"We need to drill a large acreage within a small window of opportunity to achieve the best results. Our methods are not the easy option and are very dependent on having people with the right skills to work the soil.
"Power harrows would be a slow and costly option for us when we may want to drill up to nearly 300 acres a day on clay with our three 6m drills. Although we will start sowing from the beginning of September, we cannot guarantee an uninterrupted drilling programme," says Mr Wynn.
Sowing late into poor soil conditions dramatically cuts yield potential and reduces average output, which is the key to overall profitability, he explains. "We have a big workforce at Willoughby Farms and that gives us greater flexibility in our operation."
"Power harrows may create a level tilth to drill into, but we would be concerned about damage to soil structure. It is no good forcing a seed-bed, and provided we plough early we can get some help from the weather. Our aim is to drill into firm, moist, level seed-beds to give quick emergence.
"The cost an acre of our tine and disc cultivators is minimal in comparison to powered implements, and we have a low horsepower requirement for final seed-bed work. Work rates are high and in a catchy time we can work just ahead of the drill, enabling optimum output."
Capital outlay for powered and non-powered equipment is not too dissimilar, he adds. "But a power harrow can be worn out after three years, while a tined-cultivator should still be serviceable after 10."
Power harrows, however, certainly have their place, he believes. "Combination drills are ideal tools where there are few staff and land can be ploughed and drilled in sequence. But I would be concerned about their effect on soil structure when conditions are not perfect. There is no doubt they can create pans and impede drainage."
"Tines and discs can cover more acres a day than power harrows," says Aubourn agronomist Bridget Carroll. "That means growers are less tempted to force the land. Agronomically, the benefits of using the right tool on the right day are enormous. Seed-bed structure is greatly improved with more crumb staying at or near the surface. This promotes quicker and more even germination, thanks to improved seed/soil contact. Small roots are better able to take up nutrients in the fine medium.
"Clients have tested this by splitting fields in half, power harrowing one side and using tine and discs on the other. You can see the different speed of emergence, and the subsequent overall health of the crop is greater in the non power harrowed area.
"Clearly seed-beds must be firm to minimise slug damage on our heavier soils. Rolling is essential where soil conditions allow, regardless of the type of seed-bed cultivations.
"Timeliness and quality of seed-beds is the bottom line," says Ms Carroll. "Generally our larger units have more flexibility in their approach to cultivations and I am sure they reap the benefits." *
Willoughby Farms cropping
Aubourn clay land policy:
• Marine soils tricky to work.
• Timeliness and flexibility vital.
• Need to avoid drying out.
• Small drilling window.
• Disc and tine work rates high.
• Power harrows slow and costly.
Willoughby Farms in east Lincs benefits from better soil structure, fewer slug problems and easier weed control now that power harrows are no longer part of the scene, says Aubourn farmings Bridget Carroll.