Cracking the compaction

摘要

The power harrow is an essential implement for growers needing a deep, fine seedbed. But it can also be the cause of conditions that restrict root growth and plant development. With dust billowing from the rotating tines as the power harrow slowly works its way across the flat field, it wood appear to be doing the ideal job, producing a fine, deep tilth ready to take a new crop of cabbage, calabrese or cauliflower plant blocks. But dig beneath the surface into the wet, sticky silt beneath and thosepower harrow tines are probably compressing and smoothing off a thin layer of soil. Repeat the operation once or twice to complete the cultivation task, and that layer of soil will later pose an impervious barrier to the developing root system of the new crop. "A few years ago after a wet spring, an ADAS consultant came out to look at a crop of Savoy cabbage that was badly affected by leaf tip burn," says Lincs grower Mick Leggate. "He produced a spade and soon identified the cause as a soil pan causedby the power harrow. There was a beautiful tilth on top where the soil was drier but underneath there was this layer that stopped the roots getting down to moisture, causing the stress symptoms."