4 March 2000

More than paper profit

West Country growers are enjoying the soil-improving benefits of waste produced in recycling paper. Heres how.

Demand for by-products from waste paper and cardboard recycling is exceeding supply in the West Country. Given the benefits of less fertiliser, liming and ploughing costs and better crop yields it is little wonder. Add free delivery, application and incorporation and you can see why it is popular on farms.

Production of paper waste materials, in the form of fairly dry sludge, has risen significantly over the past five years as the public has responded to Government and local council recycling campaigns.

Recycling discarded paper and cardboard produces 4% to 5% waste, totalling 2 to 3m tonnes a year. It comprises mainly lignin and cellulose fibres too short for re-use with an organic matter content of 10% to 30%.

Two types of waste are produced. One, recycled press mill sludge (RPMS), comes from brown paper and cardboard. It contains soil maintenance levels of P, K and lime and fairly high nitrogen (see analysis table). It is treated with an odour suppressant at the mill and is best spread straight from the bag and immediately ploughed down.

The second type, recycled de-inked sludge (RCF), is a white paper recycling by-product. It contains much less N, P, and K than RPMS but a lot more lime and magnesium. Because its carbon:nitrogen ratio is very high, 95:1, compared with straws 85:1 and RPMSs 23:1, crops drilled after it has been incorporated may need extra nitrogen.

As RCF has little smell it can be stockpiled on farms and there is less urgency to spread and incorporate the stuff. Its high lime content, about 9t/ha (3.6t/acre) for a 100t/ha (40t/acre) dressing, means that when applied regularly there is no need for regular liming even on inherently acid soils.

UK Papers Kemsley Mill, one of Europes largest, produces some 150,000t of paper waste a year. Its use by farmers is organised by the Cleansing Service Group (CSG) whose offices are alongside the mill, just north of Sittingbourne, Kent, overlooking the Isle of Sheppey.

"Theres certainly been more demand for paper waste since arable crop margins have dropped, so we dont have any difficulty in finding enough farmers to take our products," says Leon Mekitarian, CSGs agronomist.

There are some cogent reasons for using paper sludge, he claims. In CSGs field trials wheat receiving the standard 50t/ha (20t/acre) RPMS has yielded around 2.5t/ha (1t/acre) more than the untreated controls. This response was achieved with half the normal nitrogen top dressing and no P and K.

Mr Mekitarian says that generally the sludge should not be used on very light and very high pH soils. Its use on each site is assessed in advance and, depending on the sites soil analysis and cropping history, is applied at 50 to 100t/ha (20 to 40t/acre) every other year at most, preferably in the autumn.

"The material improves soil structure and worm activity," he claims. "But soils with no history of organic matter application tend to respond more slowly due to their low micro-organism populations."

Disposal of the paper sludge has meant an increasing amount of paperwork for his company in recent years, notes Mr Mekitarian. The Environment Agency must be informed when the material is being delivered to farms, stockpiled and spread, and provided with waste and soil analyses and the reasons for its application.

"Advice from the agency regarding prospective field sites takes 10 to 30 days, so we have to work with farmers well in advance," he explains. "Choice of suitable sites and regard for the non-farming population are key to the operation."

The recent re-zoning of domestic ground water supply areas in Kent has meant that North Downs farms are off limits for spreading the waste. This has reduced the area for its disposal in the county by about 15%, he says.

Typical application rates of 65t/ha (26t/acre) for RPMS and 100t/ha (40t/acre) for RCF provide the nutrients shown in the table above.

Kent grower David Attwood, who has been using paper waste for the past five years or so, reckons it has saved him thousands of pounds in fertiliser, liming, ploughing and other costs and significantly increased his cereal yields and grain quality. Most of his 607ha (1,500 acres) on the North Downs around Boxley, near Maidstone, has received one or two doses of the stuff. The exception is just over 32ha (80 acres) in a borehole catchment area where its application is prohibited.

Nearly three-quarters of his farm is naturally acid clay-with-flints and the rest chalky downwash valleys. The cropping comprises around 304ha (75l acres) of first wheat, 142ha (350 acres) of oilseed rape and the rest, mostly winter oats and spring beans.

Benefits

The benefits of using the waste, mainly RCF at 100t/ha, have been considerable, claims Mr Attwood. It has obviated the need for ground chalk application and is making a much greater impression on soil pH. Previously, that operation cost him some £5,000 a year and it was "always a catch-up job" that he never got on top of.

RCFs neutralising ability is most obvious in large, very acid islands in many fields that grow a lot of wild oats and couch grass and not much else. In the past these had to be treated with extra ground chalk but now just the normal application of paper waste is sufficient to raise their pH from the low 5s to the mid-6s, maintains Mr Attwood.

He prefers to plough in the waste himself and as all of his land would be ploughed anyway, the payment he receives from CSG for the job – £29.65/ha (£12/acre) – is a nice bonus.

"Although its hard to measure, Im sure were getting soil structure benefits from the paper waste," says Mr Attwood. "Were using at least 15% less plough and cultivator metal that normally costs about £4,000 a year. Usually were very heavy on this because of our flinty soil but weve been ordering the same amount as usual and having a fair bit left over. Theres also been a significant increase in the worm population."

This season (and last) slugs have been only a minor problem where the paper waste was applied. However, it is impossible to be certain whether the material is entirely responsible for this benefit, he admits.

For crops most at risk, early drilled (mid-September) wheat following oilseed rape, he drilled quarter-rate mini-pellets with the seed. No follow-up applications were necessary.

"We didnt have any wheat after rape where we hadnt used RCF and so we dont have a non-treatment comparison," says Mr Attwood. "But a cousins wheat after rape in a field next to one of mine had a big slug problem, and it hadnt had any paper waste treatment."

However, its main benefits are higher soil pH and the slow release of nitrogen by the organic matter throughout the growing season, he reckons. In 99 these led to his best wheat yields and grain quality to date. Milling wheat proteins were all above 13% and specific weights in the low 80s, while milling and feed variety yields averaged around 9.9t/ha (4t/acre) compared with under 7.5t/ha (3t/acre) before he began using paper waste.

He finds that extra nitrogen is essential for crops on RCF-treated land. So just after emergence he applies all of the free 63kg/ha (50 units/acre) supplied by CGS to his early drilled wheat and a third more than that prior to drilling the later crops. In addition, a bit extra, not supplied by CGS, is applied in early spring.

"Crop yellowing due to nitrogen starvation can be extreme and without the autumn dressing you can get plants losses," declares Mr Attwood.

Because the nitrogen lock-up tends to affect oilseed rape even more severely than wheat, he now applies the RCF after rape, not before it. The other slot for RCF treatment is before spring beans because they can tolerate nitrogen shortage.

So far he has ignored RCFs P and K content, relying on it to raise his soil indices of these nutrients, currently 2s and 3s.


Application rates

RCF RPMS

(kg) (kg)

Total nitrogen 133 233

Available N year 1 66 115

AvailableN year 2 30 70

Available P 27 74

Available K 18 35

Available Mg 150 44

pH 8.4 7.0

Liming equivalent 9.0t 3.0t

Dry matter % 58.3 27.0