20 September 1996

Care in clamps repays effort

With a later maize harvest, regular crop assessments and careful preparation are vital. Jonathan Riley reports

MAIZE dry matter levels vary by 3% between fields on one Kent unit, and a strict routine has to be observed when clamping silage.

Jeremy Wilson, the Maize Growers Association area co-ordinator for Kent, grows 32ha (80 acres) of maize at 91m (300ft) to 213m (700 ft) above sea level.

"Dry matter levels can vary by 3% between fields and we follow MGA advice and check dry matters regularly up to harvest," says Mr Wilson.

"On sheltered, lower slopes the crop is 3% higher in dry matter and we cut the driest field first."

This means the heavier, wetter maize, which is easier to consolidate, is put on top of the clamp; the weight helps to consolidate the drier maize beneath. Also effluent is absorbed by the drier maize.

Before harvest the earth walls of the clamp are strimmed and checked for stones that may tear plastic. The clamp floor is then swept clean of soil that could contaminate silage and cause secondary fermentation.

"Maize is dropped at the mouth of the clamp and spread in layers less than 6in deep," says Mr Wilson.

"The trailer always brings some soil to the mouth of the clamp and any soiled maize is removed to avoid risk of contamination," he says. Salt is added to the top of the silage to reduce spoilage and integrated into the top 10cm (4in) of the clamp using a fore-end loader.

The crop is sheeted using two layers of high quality 750-gauge plastic. One sheet is white to reflect heat and reduce spoilage. The crop is covered within a day and a half of harvest starting.

Mr Wilson uses reject stones from sea defence work to weigh down the sheets. This gets the plastic closely in contact with the silage.

"Unlike tyres, stones roll into any pockets on the silage surface rather than straddle the dips so that the sheet is always in close contact with the silage."

Herdsman Steve Harris shows the white sheet used to reflect heat and decrease spoilage. Stones are used to weight sheets down on the flat surface of the clamp.