Min-till makes an ideal partner, says recycler
Min-till makes an ideal partner, says recycler
SEWAGE sludge and minimal tillage are ideal companions, according to recycling management contractor Agrivert.
Using them together can optimise their agronomic benefits, minimise potential environmental impact and provide nutrient savings of £90/ha (£36.50/acre), says the firms Alexander Maddan.
Incorporating biosolids cake such as that from Wessex Waters Avonmouth treatment works near Bristol, into the top 75-100mm (3-4in) of soil with heavy discs gets nitrogen and phosphate to where they can do most to help encourage rooting and kick-start autumn crop seedlings, he says.
"Digested and lime-stabilised cake biosolids immediately raise the water-holding capacity and, mixed with straw stubble, help create ideal seed-bed conditions. Growers can reduce seed rates with far greater confidence."
Reducing soil disturbance and encouraging crop nutrient uptake cuts the risk of leaching, and discing eliminates smells. *
Defending use of sewage sludge cake
Agrivert will defend its use of sewage sludge cake in DEFRAs proposed NVZ closed period of Aug 1-Nov 1 on shallow and sandy soils, says Mr Maddan. Most of the immediately water-soluble nutrients are removed during processing, he explains.
"We can demonstrate that it is a slow release product which is safe to use during the proposed closed period."
The UK produces about 3.2m tonnes a year of sewage sludge, but that is small beside the 21m tonnes of farmyard manure, he notes. Although more biosolids need to be recycled to farmland since the ban on dumping at sea, it still needs only 4% of UK arable land to take the whole output, he calculates.