24 January 1997

Detailed analysis gives big cuts in fertiliser bill

Slurry analysis has cut fertiliser bills on one Cheshire dairy unit. Jessica Buss reports

SLURRY spreading on one Cheshire dairy unit – completed by late January to avoid silage contamination – saves £2650 on bag fertiliser bills.

Clive and Andrew Gurney, who run 120 milkers at Austerson Hall, Nantwich, belong to the Cheshire Grassland Societys research and development group, which has worked to improve slurry use.

The Gurneys 45ha (112-acre) all-grass farm needs just over £7000 worth of fertilising nutrients a year, yet efficient slurry use means that only £4500 was spent on bag fertiliser last year.

They check the nutrient balance of the soils by sampling a percentage of the farm each year for pH, phosphate, potash and magnesium indexes. The farms soils currently have high indexes.

Clive Gurney also gets a laboratory to analyse the farms slurry and dirty water at least once a year, at £25 a sample. That calculates how much nitrogen, phosphate and potash is available to the soil after ammonia losses at spreading.

The test enables Mr Gurney to know that when he spreads at 33,700 litres/ha (3000gal/acre), for example, it provides 36kg/ha (29 units/acre) N, 46kg/ha (37 units/ acre) of P and 113kg/ha (91 units/ acre) of K. These nutrients are worth £58.44/ha (£23.65/acre).

The phosphate and potash from slurry should supply all that the grass fields need, says Mr Gurney, who buys bagged potash for second- and third-cut silage fields only. "Potash must be applied little and often and we cannot spread slurry before second and third cuts for risk of contaminating the silage," he says.

Before spreading he calculates exactly the nutrients each field will receive from slurry. That involves analysing the slurry on farm in case it has been diluted by rain water since the laboratory analysis.

"Slurry dry matter is the most variable factor, so we need an on-farm test to use on the spreading day," he explains. Several on-farm tests are available but Mr Gurney finds a hydrometer is simple and quick to use and gives a good guide to the slurrys nutrient content.

He is also careful to ensure he knows how much slurry is to be spread on the field. He applies five tanker loads a hectare (2/acre) over the whole farm in late winter. Spreading is completed by the end of January to avoid silage contamination and none goes out before Christmas, when nutrient losses would be high. Grazing fields also receive slurry at 33,700 litres/ha (3000gal/acre) but application to the 6ha (15 acres) for turnout is soon after Christmas to avoid staggers.

"Slurry produced later in the year is stored and ploughed into autumn grass reseeds when soils are dry. It adds humus to the soil, helping the crops drought resistance, and by ploughing it in we use the full value of nutrients available."

Unfortunately, spreading slurry on top of grass means only 25% of the nitrogen is used. There are actually 25kg (50 units) of nitrogen in each 4450 litres (1000gal) of slurry, says Mr Gurney. "When the right system for injecting is found, the rewards will be dramatic and economic," he says.

The Cheshire grass research group feels the way ahead could be an umbilical injection system.

Above: This lagoon holds dirty water until it can be used for irrigation after first-cut silage. Right: Before spreading, Clive Gurney calculates exactly the nutrients each field will receive from the application using a hydrometer.

&#8226 Analyse slurry.

&#8226 Know the application rate.

&#8226 Allow for nutrients from slurry when applying fertiliser.

Better storage for better use

BETTER use of slurry has been possible at Austerson Hall since the Gurneys built a store large enough to hold five months waste and a separate dirty water lagoon eight years ago.

Dirty water irrigation now helps grow the forage that enables Mr Gurneys 120 cows to produce 3750 litres, of their 8800 litres a cow yield, and to feed the 90 youngstock.

The dirty water lagoon is large enough to hold 227,5000 litres (0.5m gal) until it can be used for irrigation after first-cut silage.

"Dirty water goes on at 3000gal/acre after first-cut silage before the leaf starts to grow, avoiding contamination," says Mr Gurney. "This kick-starts grass growth and washes in inorganic fertiliser giving the benefit of an extra weeks growth."

Mr Gurneys dirty water contains 4.5kg (3.6 units) of N, negligible P, and 0.9kg (0.7 units) of K in each 4450 litres (1000gal). He takes this into account when applying second-cut fertiliser. &#42

Less nitrogen lifts grass DM

PRODUCERS in the Cheshire Grassland Societys research and development group have found that using less nitrogen encourages higher grass dry matter yields.

Group member Clive Gurney says spreading 100kg/ha (80 units/ acre) of inorganic nitrogen after a typical slurry application in late winter, providing 31kg/ha (25 units/ acre), produces a higher dry matter yield than when 125kg/ha (100 units) of bag N and slurry are applied.

"At 100 units of bag N/acre there is a decease in dry matter yield – and as the dry matter of the crop is reduced the crop lodges. Lack of light stops grass growth, so the yield is lower," says Mr Gurney.

For second cut the level of N supplied is also important and should be reduced to 88kg/ha (70 units/acre) of bag N without slurry. &#42


SCOURING dairy calves treated with a combination of oral electrolytes and intravenous hypertonic saline solution recover faster than those treated with either method alone, according to the Veterinary Record, Jan 4, 1997.

KETOSIS in cattle and sheep can be detected using a new diagnostic test kit. The kit can be used with milk, saliva, urine or blood and will identify clinical acetonemia or pregnancy toxemia in two minutes. The Keto-Kit contains the equipment for testing, and a positive result is seen by a colour change after the test fluid – for instance, milk – is added to the test reagent. Each test costs about £1.50. Details from Lab Pak (01676-540022).

WINNER of this years George Hedley Memorial Award, presented by the NSA, is Angus Russel, of Newton Bank, Franks-croft, Peebles. The award, presented each year to the person who has given outstanding service to the sheep industry, was given to Dr Russel for his work on ultrasound scanning.

QUICK diagnosis of rotavirus is possible with a new test. Based on detecting rotavirus in faecal samples, the test is designed for field use and will give a result in three to five minutes. Each test has a control to ensure correct performance, and a test for the result. The kit contains 10 tests with the equipment for sampling and testing, and has a shelf life of 18 months stored at room temperature. Details from Lab Pak on 01676-540022.

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