After a wet winter, in areas where treading damage has been unavoidable, the soil may have become a little compacted with the bulk of permanent pasture roots concentrated in the top 10–12cm.

Where this is the case pasture growth over summer and early autumn will be less than optimum and come in fits and starts depending on the frequency and quantity of rain.

After 20mm of warm rain plant growth may be very rapid only to slow rapidly with the onset of two or three days of warm windy weather.  This puts pressure on pasture management with some operators opting for an open-gate policy on the basis that it may as well be grazed before it turns brown and disappears.

Not all farmers have the same philosophy as well-structured soils allow pasture plants to access moisture from half a metre, or even deeper, resulting in more even growth.  Well-structured soils also have the apparent ability to develop a crust reducing the loss of moisture to the atmosphere while still allowing moisture to be utilised from a lower depth.

A recent field trip to neighbouring dairying properties provided a graphic display of the degree to which soils with different management inputs vary in structure, especially with respect to the amount of granular aggregate and resultant rooting depth of clovers and grasses.

On the property with excellent structure, the outstanding soil characteristic was the amount of aggregate, particularly fine crumb.  The quantity of fine feeding root was also impressive.  There was little sign of root congregating near the surface with an almost even spread of root mass to the bottom of a 25cm spade.  The roots went to a much greater depth, all quite fine and white indicating healthy development over winter.

As the rule of thumb is ‘weight below the ground in root equals weight above the ground in leaf’, the property with the better textured soil will grow measurably more total feed throughout the remainder of the growing season.

It was obvious that the property where soil structures were tighter and root development was closer to the surface, that heavy rain over the last few months had collected in hollows.  Soil in that condition has less moisture holding capacity further limiting potential for summer growth.

One of the differences between the two visited properties has been the use of dolomite.  The property with the well-structured soil has, for close to twenty years, had dolomite applied as the annual input of magnesium, and a portion of the 200kg/ha of calcium.

Dolomite, based on long-term field work, is the most effective magnesium fertiliser available and suitable for application to all soils where, based on soil test data and known usage, there is a need for magnesium.

On ‘heavy’ soils with a high clay or silt content, dolomite helps the formation of initially large aggregates increasing macro pore space, speeding the rate at which excess moisture is able to drain.  On ‘lighter’ soils containing more sand dolomite also helps build aggregate by holding groups of particles together increasing moisture holding capacity.

An annual application of dolomite at the recommended rate provides at least twelve months supply of magnesium and due to the fineness of grinding the response time under good growing conditions is rapid.  Performance is unmatched, it’s local, and the technical support available comes with years of practical experience.

Here in the Rotorua district the December growth figures since 1989 we have give a mean of 60kgDM/ha/day, with a range of 40 – 88kgDM/ha/day.

Figures from Edgecumbe district over the last 7 years show growth ranging from 47 – 86kgDM/ha/day with a mean of 66kgDM/ha/day.  There are long term pasture growth figures for all districts.

Based on this information growth in December is quite reliable and the examination of physical soil structures and rooting depth will further help predictions.

Soil is a living breathing organism and therefore able to respond, often quite rapidly, to changing climatic conditions.   After a prolonged dry period a crust may form on the soil surface, possibly in an attempt to limit moisture loss as it soon disappears after a small amount of rain.

Pasture plants have the ability to send roots to a depth of 0.8m enabling them to access moisture and nutrient from areas usually little affected by our typical short term dry spells over summer.

Recent digging on clients’ properties has shown strong root depth to spade depth (25cm).  The bulk of the root is white indicating that it has formed during winter and early spring prior to the rapid growth phase which starts with soil temperatures reaching a daily minimum of 10°C.

There has been little evidence of roots matted in the top 7.5 – 10.0cm of the soil.  Matting of root usually only occurs if there is hard layer at about 10.0cm.  In some instances if water soluble fertiliser has been regularly applied plant roots may congregate close to the soil surface and this is often accompanied with a hard layer just below.

The ability of soil to withstand the pressure exerted by animal feet is due to the activity of beneficial soil dwellers, predominantly earthworms, bacteria, and fungi.  For these essential workers to provide the assistance necessary there must be sufficient available calcium.

Where excess fertilizer nitrogen is applied soil calcium levels may reduce rapidly with soil pH levels declining to levels of less than 6.0.  Soils may become compacted and unable to provide the moisture and nutrient necessary for strong clover growth over summer.

It is clover that provides strong growth over summer as most pasture grasses only remain in a vegetative stage at soil temperatures less than 20°C.  Above that they become stressed and a seed head supported by a stalk rapidly forms, nearly always occurring in the first week in November.

Calcium is the nutrient most influential in clover growth as clovers are often 3 – 4 times higher in calcium than grasses.

Common to nearly all the properties visited recently is the annual application of dolomite at the rate required to provide magnesium lost to production.  Dolomite also contains calcium, has a stronger pH modifying effect than lime, and is an outstanding conditioner of physical structures.

Some years ago a farmer in the Waikato drafted out his lightest cows in autumn, put them into a large covered shed and fed them almost entirely on kiwifruit.  It wasn’t long before they gained weight and were reintroduced to the main herd without fuss for wintering.

There are cows close to main centres that are fed waste produce from Supermarkets that includes a variety of potato chip type products and a range of confectionary.  Although I haven’t seem them I have it on good authority that these cows perform well by industry standards, with the intriguing part of this story being that a considerable amount of this ‘food’ is still in its wrapper.

Dairy cows that die as result of a calcium/magnesium deficiency or imbalance do so not because their diet is a little deficient, but because their diet is substantially deficient or imbalanced, and unsuited to the animal’s requirements for calving and early lactation.

This is where a single annual application of dolomite can have a major impact.  A single application of 220kg/ha provides 25kg of magnesium and 53kg of calcium per hectare, however it is what results that is important.

The magnesium content of grass as a result of a dolomite application may vary from 0.22 – 0.25% depending largely on the amount of direct sunlight. Leaf calcium content usually measures no less than 0.60% as the calcium and magnesium release at the same rate.

Dairy cows fully fed on grass with this Ca and Mg content receive sufficient to ensure Ca/Mg related metabolic disorders are minimised and production after calving moves rapidly toward its peak, provided rumen function is good.

Now before the calculator is brought out to see whether there is some other way the same amount of calcium and magnesium can be applied by mixing other products together, think about the soundness of the argument that cheapest is best.

Think about your own farm vehicles.  Were they the cheapest available when you bought, or was the main consideration their suitability for the work to be undertaken?  Can the cheapest vehicle be relied on to perform faultlessly year after year?

Soils are living breathing organisms and the health of our animals in spring is a direct reflection of the health of our soils.  Continuing to apply the same soil nutrient package each year, with perhaps minor tinkering, enduring the same animal health problems each spring when there are alternatives that provide largely trouble free calving suggests flawed thinking.

With the present value of quality dairy animals and the increasing payment for fat and protein this is the time to maximise health and performance by applying dolomite, proven to outperform all other calcium/magnesium options.

For those still not convinced, buy 25kg bags of dolomite, empty them into a container where it can stay dry, make it available to the herd each day, observe and monitor.

As that question could not be adequately answered without at least knowledge of current soil nutrient status and past fertiliser inputs the call took some time, with several pieces of extra information providing a clearer picture.

The entire farm had been cultivated in the autumn prior to dairy cows being introduced.  At that stage there had been no known applications of fertiliser nitrogen.  Initially pugging damage was minimal even in extended periods of wet weather, with excess moisture draining freely without ponding

Animal health during the first two springs had been largely trouble free. Calcium/magnesium related metabolic problems had been few, cows calved without difficulty, the occasional mastitis case easily and effectively treated, with somatic cell counts remaining low throughout both seasons.

The third spring had been more challenging with a range of issues requiring extra time and effort.  The number of calcium/magnesium related problems had increased particularly amongst older higher producing animals. The incidence of mastitis also increased with somatic cell counts remaining stubbornly high at times.

Is it possible that all issues are related?  The downward pressure exerted by the feet of heavy animals is significant, and as soils are ideally by volume 25% air, 25% moisture, and 50% solid, compaction particularly in periods of wet weather can readily occur.

Reduced air content reduces the activity of beneficial soil organisms as they rely on a steady interchange of air entering and gas being released.   Under intensive dairying soils will often compact at 75 – 100ml, slowing the ability of excess water to drain freely, with the soil above the developing pan more easily scuffed and pugged.

With plant roots concentrated in the top 100cm, soil moisture content and chemistry rapidly change.  The potassium content in the leaf of pasture often increases significantly during periods of wet weather at the expense of calcium and magnesium, which are more tightly held.

The question of whether compaction is inevitable is then open for discussion.  Under treading pressure soil compresses, compaction occurs when it does not return to its ideal state. This is not inevitable and careful management is required.

When the ideal levels of calcium and magnesium are obtained soils are much less likely to compact.  The ideal levels are best ascertained by soil testing.  In all situations where magnesium is required Golden Bay dolomite is the most effective input.

For an intensive dairy operation a single application of dolomite at 220kg/ha provides 25kgMg/ha, sufficient for one season, and 53kgCa/ha, approximately one quarter of the required annual calcium input.  Due to the fineness of grinding the release of nutrient can be rapid with a marked improvement in animal health achievable within three weeks of application.

Dolomite also has a strong conditioning effect on the soil, increasing the crumb content, reducing the likelihood of compaction occurring and as with all living systems when one aspect of health improves every aspect improves.

I came across a small group of dairy farmers in the Matamata region that claimed to have minimal animal health issues of any type.  The one thing that was common practise amongst this group was that Golden Bay Dolomite was applied regularly to each of their properties.

Their claim was that calcium/magnesium problems were negligible, bloat was almost non existent, as was facial eczema.  I was somewhat puzzled as to how a single annual application of calcium and magnesium could have such an effect on what were perceived to be ailments of unrelated causes.

As farmers our understanding was that each particular illness had a particular cause, they were unrelated and each needed a quite separate treatment, often with varying results.  Our own experience was that even with increasing the amount of magnesium supplemented to stock we needed to remain extra vigilant to avoid unwanted deaths in spring.

Bloat then reared its ugly head just as cows started to reach peak production.  There is plenty of work to indicate that bloat is linked to the potassium:sodium ratio of spring pasture.  Ideally the ratio in a pasture leaf test should be 7:1 or less however it is not uncommon for this ratio to exceed 25:1.

Facial eczema spore counts can vary widely between neighbouring properties, even when subject to the same climatic conditions.  There is a school of thought along with evidence that indicates facial eczema problems are lessened with the regular application of lime.

Perhaps the reason for the group of farmers in the Waikato claiming that annual applications of Golden Bay Dolomite were able to alleviate all these issues is due to its ability to ‘condition’ soils.  Dolomite has the ability to improve the physical structures of soil allowing for better drainage of excess water, more rapid exchange of gasses, and quicker recovery from treading damage.

Soil health improves with better drainage, with plant roots able to grow deeper into the soil accessing nutrient and moisture from lower levels.  Along with the extra calcium and magnesium applied there is probably less luxury feeding taking place near the soil surface where potassium concentrations are likely to be higher.

Dolomite encourages earthworm activity, and earthworms devour dead grass left on the soil surface, limiting the habitat for facial eczema spore.

Just as with any living organism when just one aspect of health is improved all aspects improve.  Every aspect of soil, chemical, physical, and biological, is related and interdependent.  Dolomite supplies both calcium and magnesium, though its primary function is as a magnesium fertiliser.

Being originally a seabed deposit it also contains a wide range of naturally occurring trace minerals.  Dolomite can be applied at any time of the year with an improvement in animal health and performance being reported sometimes within a fortnight of application.

Over a period of several years crop yields declined to the point where it was deemed no longer financially viable to continue cropping and the decision was made to return the area to pasture to be rotationally grazed.

The reason for the decline in yield was not the lack of major growth nutrients, but a steady decline in humus.  Humus is the result of the breakdown, carried out by soil organisms, of plant matter.  The decline of humus resulted from both regular cultivation with soil exposed to the atmosphere for prolonged periods and the probable overuse of soluble fertilisers particularly nitrogen.

My initial visit to the area was three years ago soon after the initial application of a remedial nutrient input programme based on local Golden Bay Dolomite, along with soft phosphate rock and elemental sulphur.

At that time, as it was at the time of the recent visit, there had been a great deal of heavy rain during the month prior.  The soil had been hard underfoot, with few earthworm casts visible and the grass plants were growing with their crowns well above the soil surface.  Although a sand based soil, there were puddles covering a significant area of the paddock.

Now the soil is soft underfoot, and feel is a valid measure when carried out regularly, with the surface almost entirely covered in worm casts, some of which were very large indicating the presence of deep burrowing worms along with others working closer to the surface.

Although recently grazed there were few obvious dung patches and only in the wetter hollows were urine patches obvious.  The soil surface was more than 90% covered in a range of pasture species, all with their crowns close to the soil surface and there were no puddles although there had been heavy overnight rain.

Digging a number of holes to the subsoil depth of about 300mm, a little over a spade depth, showed that the majority of plant roots were going straight down.  Many of the root ends at 250 – 300mm were white and fine indicating they had recently grown, with few darker roots indicating ongoing breakdown of old root mass.

There was no obvious break line at 75 – 100mm depth indicating the soils ability to rebound from the pressure exerted by stock feet.  A truly healthy soil does not compact under rotational grazing regimes where stock are well fed and on areas for a maximum period of 48hours.

A walk to the fence line confirmed our judgement that soil health was excellent.  The stock that were resident in the area and had recently grazed the paddock, were in outstanding health.  Although they could have eaten more, had more feed been offered, they were all large framed animals with dark glossy coats and even without drenching there was not a dirty tail to be seen.

For more information call 0800 436 566 (0800 4 DOLOMITE).

The ability of air to move into the soil and gases to move out is every bit as important as the application of nutrients.  In order for this interchange to happen to best effect soils must be able to withstand heavy treading over winter without becoming severely pugged or the surface sealed.

Graham Shepherd’s Visual Soil Assessment manual states that treading damage on compacted moist soil may reduce pasture production by up to 27%, with a reduction in growth of up to 45% where soils are badly pugged.

There is a difference between a little scuffing, or ‘hoof cultivation’, that repairs rapidly once stock are removed, and pugging.  Stirring of the top soil by feet can be beneficial as it rapidly incorporates dung and dead plant matter speeding the formation of humus.

Pugging is not inevitable; we work with many farmers where even in very wet conditions cows create little damage.  Animals know in advance of the onset of dirty weather and provided they have access to plenty of high energy fibrous feed they will fill up, turn with their tails into the weather and wait for it to pass before moving.

One common misapprehension is that pasture quantity and quality do not occur together, often expressed as “ I would love to grow better quality feed however I can’t afford to grow less.”  Quantity and quality come in the same basket and the role of air in the soil in achieving optimum performance is often ignored.

Beneficial soil organisms require a steady supply of air for maximum activity and it is this activity that ensures a steady supply of nutrients, of which nitrogen is one, for plant uptake.  Plant roots also require oxygen for growth with autumn and winter important times for root development.  Poor root development over winter markedly reduces spring growth.

Presently poorly aerated and drained pastures or areas within properties are easily identified both by colour and length of leaf.  In the wettest situations areas of pasture are more yellow than green with urine patches very obvious.  Urine contains nitrogen and pastures on waterlogged soils respond dramatically however applying nitrogen fertiliser is not the answer.

With thousands of kilograms of nitrogen held in the top 25cm of each hectare of soil the key to making it plant available at any time, and particularly over winter and early spring, is increasing the quantity of air able to enter and leave the soil.

Management of stock over winter remains the most important aspect of a farms ability to grow winter and early spring feed.

With a winter application of Golden Bay Dolomite at 200 – 300kg/ha the physical structure of the soil can be enhanced as well as providing a steady supply of plant available calcium and magnesium over the critical lambing and calving time.

Dolomite is essentially a magnesium fertiliser i.e. dolomite is only applied where there is a requirement for magnesium.

Golden Bay Dolomite typically contains 11.5% magnesium and 24% calcium, both in the carbonate form.  The deposit at Golden Bay is unique in this country although there are magnesium silicate (serpentine) deposits in both the North and South Islands.

Magnesium silicate is very much harder than magnesium carbonate and therefore the release period is longer.  A field trial conducted in the Manawatu over a 2 ½ year period compared the agronomic effectiveness of a number of magnesium products that included both dolomite and serpentine rock.

17 months after application 90 – 100% of the magnesium in dolomite had dissolved while 45% of the magnesium in serpentine had dissolved.

Typically dolomite is applied to pastoral land at the rate of 200 – 250kg/ha.  In our twenty year experience with dolomite, applying heavier rates does not necessarily provide better performance.  Well-structured high organic matter soils may be able to store magnesium and calcium, however the economics of applying capital inputs when smaller quantities applied frequently provide the same results, need to be carefully considered.

Although technically the release rate of magnesium and calcium from dolomite may be slower than from magnesium oxide the improvement in animal health on properties to which dolomite is applied may be obvious within 10 – 14 days after application.

The method of grinding dolomite provides a small percentage of very fine particles.  Because of the high surface to volume ratio of the fines, breakdown in moist acidic conditions on the soil surface can be rapid.  Typically 62% is less than 150 microns.

To argue that a product should be applied because it is the cheapest regardless of its effectiveness is misleading.   Product is only suitable for use if it provides the desired outcome, regardless of the cost of input, however the financial benefit(s) must outweigh the cost of supply and application.

The health of plants and animals are dependant on the soil health, with healthy plants and animals unable to be sustained on degraded soils.  Under most conditions, particularly intensive livestock grazing or where there is regular cultivation, the responses from more oxygen entering the soil outweigh the responses from other inputs.

Dolomite is a proven soil conditioner and a single application is sufficient to start the process of improving physical soil structures, and because of its unique ability to deliver the benefits of improved soil and animal health it has become the standard by which other magnesium fertilisers are judged.

As a result beneficial soil life is stimulated.  It is very difficult to measure beneficial soil microbes as we don’t know a great deal about what is there or what ought to be there and by the time the counting process is underway populations will have changed.

Dr Graham Sparling in his 2004 Norman Taylor Lecture stated that “despite being present in very large numbers, soil microbes are reluctant to grow in laboratory culture, and it has been estimated that less than 5% of organisms have been cultivated”.

The reason we should care about soil microbes is because our very survival depends on their existence and the maintenance of a diverse population in excellent health.

As pastoral farmers and growers are producers of food we have a responsibility to ensure that the soil we farm provides a suitable environment for not only beneficial soil microbes but also soil macrobes with the ones best able to seen and counted being earthworms.

If there is a resident population of healthy earthworms then we may assume that there is also a healthy population of beneficial soil microbes, without which we have only rock dust.

There are typically 3 distinct types of earthworms (surface workers, mid range workers, and deep burrowers) in our soils, nearly all introduced from overseas in soil used as ballast in sailing ships and around the roots of trees and plants.

Although they thrive in most friable well-aerated soils they are able to survive in water for quite long periods.  They don’t drown in puddles but are killed by sunlight after having come to the surface at night in wet weather in order to relocate.

The ideal temperature for earthworms is 10°C, which is why the greatest number of casts is seen on the soil surface during winter and early spring.  Not all worm casts are on the surface with much casting taking place below the surface.

The number of worms in a 25cm spade cube will vary.  There is no ideal number as different soil types will support different numbers.  Soils with high sand content do not support large numbers as sand is abrasive, and worms need somewhere cool and damp to survive dry summers.  Typically between 10 and 30 worms in can be found in a cube of well-managed pastoral soils containing a mix of silt, sand and clay i.e. loam soils.

Initially after making more calcium available earthworm numbers may increase to 70+ per spade cube, however earthworms are macro processors and as the friability of the soil steadily improves earthworm numbers will stabilise based on available food.

The time from egg to maturity is around 90 days so when conditions are favourable rapid increases in numbers can occur.  A worm egg is about the size of a match head and usually a dull yellow in colour.

Dolomite apart from being the most effective magnesium fertiliser, and supplier of calcium, is also a proven soil conditioner ensuring soils drain more freely over winter and recover more rapidly from heavy treading damage in wet conditions.

As cows got older and bones hardened calcium availability declined and the likelihood of metabolic disorders increased.

With the advent of maize silage and the increase in fertiliser nitrogen usage the need to increase calcium supplementation became greater.  Nitrogen fertiliser reduces clover growth and increases the rate of grass growth, thereby reducing the intake of calcium.  Maize contains relatively low levels of calcium so for best effect calcium needs to be added.

To actually digest the mix of feeds extra energy should be added, however the amount required will depend on sunshine hours at the time, the frequency and rate of nitrogen fertiliser applications, and climatic stress at the time.

So what is the best formula?  The most important concept to retain is that everything; feed, fertiliser, animal breed and age, weather conditions, management practises are all inter-related; alter one thing and everything else changes.

The second most important concept is that everything starts with the soil.  If there are ill health issues of any sort go back to the soil, ensure initially that physical soil structures are as close to ideal as possible before analysing soil or tissue tests.

A well-structured soil is capable of providing a mineral rich pasture of sufficiently high energy for near maximum animal production.  The key is well-structured, and there are some easy checks with a spade that can be made.

All soils compress under the weight of heavy animals and in certain conditions this leads to compaction.  The application of Golden Bay Dolomite once a year helps overcome compaction problems.

Dolomite is a proven soil conditioner that contains magnesium, calcium, and a wide range of essential minerals.  Applied to the soil at 220kg/ha dolomite provides 25kg/ha of magnesium, sufficient to replace losses on a high performing dairy unit, and 53kg/ha of calcium.

Provided dolomite is applied annually, autumn being an ideal time, calcium/magnesium related metabolic disorders are minimised.

Increasing numbers of farmers are feeding dolomite with supplement, or making it available to their animals, particularly during winter and spring.  This further reduces the likelihood and severity of metabolic disorders over this time.  When made available in easily accessible containers animals will eat only when they have a requirement and only the amount required to meet their needs.