Studying soil to boost herd health
Studying soil to boost herd health
Frustrated by lack of a solution to some dairy herd health and production problems, one
nutritionist devoted her Nuffield scholarship to finding the answer in the soil.
Marianne Curtis reports
TAKING a more detailed look at soil nutrient balance and applying fertilisers which correct rather than upset it, could help solve persistent problems such as dairy cow infertility, according to one dairy nutritionist.
An increasing number of dairy herds are struggling to meet yield potential and even more are experiencing a progressive decline in fertility, says Jo Scamell, technical manager of Ground Level Nutrition, which specialises in improved soil management.
"Nutritional solutions will have a limited impact on resolving these problems where soil minerals are out of balance."
Excluding energy deficiency, many fertility problems relate to enzyme function and hormone status, dependent upon trace elements such as copper, explains Mrs Scamell.
But supplementing ever higher levels of copper may not provide a solution as the effect can be cancelled out by cows metabolism when molybdenum, which interferes with copper absorption, is high in forage. Instead, the answer lies in correcting soil mineral balance to prevent excessive molybdenum uptake by grass, she believes.
Dominant minerals in soil are calcium, magnesium, potassium, sodium and hydrogen, known as macro-elements. "Copper availability can be enhanced by correcting the macro elemental balance of the soil. However, this may take several years during which time mineral feed supplements should be designed to accommodate overall ration balance.
"The macro elemental balance has great impact on overall soil function, including nitrogen use and trace element availability to plants."
Most producers regularly apply lime every few years to correct soil pH, but even this apparently innocuous material is variable and can do more harm than good when the wrong type is applied, she warns.
"Lime is not all the same. Always ask for a specification sheet when purchasing lime as it can be dominated by calcium, magnesium or be somewhere in between.
"It is common to use lime from the quarry nearest the farm, but this is likely to contain calcium and magnesium in similar proportions to your soil, pushing it in a certain direction. When soil has a high magnesium content, such as some clay soils, avoid using dolomitic lime, otherwise soil will gradually become like concrete."
Selecting sources of nitrogen, phosphorous and potash that enhance soil nutrient balance is also important, Mrs Scamell believes. "When buying fertiliser, ask about ingredients. When soils are sulphur deficient it may be appropriate to use ammonium sulphate, to raise sulphur levels and enhance efficiency of nitrogen use."
Finding out true nutrient status of a soil is the starting point when attempting to correct nutrient imbalances. "Conventional nitrogen, phosphorous, potassium and pH evaluation has served the UK for the past 40 years or so. But soils are becoming more compacted and less efficient at using fertilisers.
"A different integrated soil management approach, based on work in the US and Australia, has been developed through Thomson and Joseph laboratories." It looks at soil pH, organic matter content and total levels of basic nutrients. Balance of macro elements such as calcium, magnesium, sodium, potassium and hydrogen, which influence release of other nutrients to plants, is also included in the report. Finally, independent advice is given on the most appropriate nutrients required to restore soil balance.
At £80/sample for a full soil analysis, this approach is probably more expensive than conventional NPK pH analyses. But for producers facing seemingly intractable yield or fertility problems, it may be a small price to pay. "Consider how much is spent on vet bills trying to solve these problems."
Paying more attention to soil will mean it produces forage with a nutrient balance more closely matched to livestock requirements, she says.
But restoring soil balance must be tackled over a three to five year period. "Instead of just thinking about the current grazing season, think ahead. Consider which fertilisers best match your soil for its long term productivity."
As well as improving fertility, getting soil balance right can also deliver substantial benefits in terms of yield. "Trace elements influence enzyme function which determines how efficiently cows metabolise feed.
"When there is an overall imbalance of trace elements in the diet, conversion of feed into milk can be severely impaired. One client, feeding a reputable mineral supplement, a 50:50 ratio of grass/maize silage and 1.4t concentrate was achieving dry matter intakes of 24kg/head and an average yield of 6200 litres.
"Using an integrated soil management approach, yield increased to 8500 litres within three years at the same dry matter intake." *
SOILCARE
• Often neglected.
• Not just about NPK.
• Improves stock health and productivity.
Answers to dairy cow production and health lie in improving soil mineral balance, believes
Jo Scamell.