Accelerates seed germination and early maturity of crops; important for nitrogen metabolism. Mn becomes more available at low pH - toxicity can be a problem. High iron or phosphorus can tie up manganese. When K and Na base saturation together exceed 10%, then manganese uptake is blocked.

Found in the mitochondria, it is key component of energy metabolism - may be linked to Chronic Fatigue Syndrome. Critical in cartilage formation and neurotransmitter synthesis (Alzheimer’s is linked to a decline in production of acetyl choline – a key neurotransmitter).

Ruminant levels range from 75-200 ppm of the ration. Nuts, whole grains and black tea are rich in manganese. Deficiencies may lead to infertility in animals and humans. Manganese is required for growth, bone formation and it is also an enzyme activator. Symptoms of manganese deficiency include decreased signs of oestrus and poor conception. A deficiency may manifest as ‘knuckled under’ legs in new born calves, or an excess of bull calves. Take-all in wheat is Mn deficiency.

Sources of manganese include trace mineralised salt, licks, and commercial supplements. Apply manganese sulphate to the soil to maintain a minimum of 75 ppm, building to an optimum of 125-250 ppm. However, do not allow Mn to exceed iron levels, maintaining at least a 5 ppm gap between the two. Mn over (or too close to) Fe will cause the iron to oxidize in the leaves, leading to Fe deficiency.

How Iron and soil microbes influence plant growth

Iron is the most abundant element in the earth but is not always plant available. Humic acid may be a key to make it available. Iron draws heat into the leaf, promoting growth. It is essential to the function of chlorophyll, fixing magnesium to the chloroplast. Iron absorption is hindered in cold soils (as is P), and in small root systems.

Adequate sulphur reduces the chances of iron deficiency.

In animals, iron is concentrated in haemoglobin and is used by the liver and immune system. It is found in many enzymes, proteins, and in DNA synthesis. Ruminants require 100-200 ppm and humans 20 mcgs per day. Symptoms of deficiencies include nutritional anaemia and pale mucus membranes. Beef, liver and tuna are very good sources of iron.

Always ensure iron exceeds manganese at all times. There are at least 500,000 hectares of iron deficient hill soils in NZ. Maintain at least 200 ppm in the soil. Kiwi Fertiliser consultamts will always prove the need for iron before recommending it. Since soil probes are shallow and iron may be present in deeper profiles, the addition of iron sulphate may be unnecessary. Proving a need may involve a test plot, leaf test or a deeper soil test.

Plants are only organisms that can directly utilise the sun’s energy. They transfer 30% of their energy from the leaves to the rhizosphere and in doing so stimulate soil microbes. If this process is interrupted, (e.g. girdling), diseases are more likely.

Plant exudates feed microbes that in turn can deplete soil oxygen. Ethylene is then produced at the anaerobic micro-sites at 1-2ppm to inactivate the microbes. Oxygen demand reduces and oxygen diffuses back into the soil.

Presence of ethylene in undisturbed soil indicates the soil is healthy. Agricultural soil has little or no ethylene. Plant pathogens are unimportant in the former, but prevalent in the latter where inorganic fertilisers and pesticides are used, increasing production costs.

Agricultural soils fail to produce ethylene because of the changes in soil nitrogen. Virtually all nitrogen in undisturbed soils is in the ammonium form. Modern farming techniques encourage a specific group of bacteria that convert most nitrogen to the nitrate form. Nitrate nitrogen inhibits ethylene production. Ammonium nitrogen does not.

When oxygen is consumed at a rhizosphere micro-site, a series of complex chemical changes occur. In adequately aerated soil, virtually all the iron is ferric (oxidized) and immobile. If oxygen is consumed, the minute iron crystals break down into the highly mobile ferrous form. Ferrous iron is a specific trigger for ethylene production. When oxygen is depleted and nitrate nitrogen is present, the production of ferrous iron is inhibited or prevented.

However, a precursor produced in senescent vegetation is required to react with the ferrous iron before ethylene can be produced. In intensive agriculture most of the older leaves are removed by grazing animals, by harvesting or by burning, so little is left to decay.

A major limitation to plant growth in most agricultural soils is an inadequate supply of plant nutrients, regardless of the supply in the soil. Iron crystals have a large surface area and are highly charged. As a result, nutrients such as phosphate, sulphate and trace elements are tightly bound to the crystals and unavailable to plants. If anaerobic micro-sites are able to develop, the crystals break down, releasing the nutrients for plant uptake. Ferrous iron is released into the soil. Other nutrients including calcium, magnesium, potassium and ammonium, are held on the surface of clay and organic matter. The release of ferrous iron displaces these nutrients into the soil solution where they are available for uptake by plants.

Modern farming techniques encourage the aeration and oxidation of the soil and give a short-term increase in plant growth. Unfortunately, those practises also rapidly create long-term problems of nutrient depletion and increased plant diseases. Treatments that stimulate rates of nitrification (conversion of ammonium to nitrates,) such as excessive use of nitrogenous fertiliser, or excessive removal of plants by overgrazing, or forestry operations require moderation and re-examination.

Based on research by Dr. M.A. Smith, Principle Research Scientist, NSW Dept of Agricultural, Biological and Chemical Research Institute. PMB 10, Rydalmere 2116, Australia. Published in the Australian Plants Periodical Vol. 9 Dec. 1977.

Boron (B) is necessary for uptake and efficient use of calcium in the plant. It is a calcium synergist and a temperature regulator. Boron is essential for cell division and development, particularly in the growing points of shoots and roots, also promoting flowering. It affects pollination, pollen viability, fruit and seed set. It is required for the movement of sugars (e.g. energy) within the plant and hence plays a significant role in photosynthesis.

Typical Boron deficiency symptoms include: hollow stems in cabbages and cauliflowers; woody taste in strawberries; poor seed set generally; crosswise cracking of celery stalks; external and internal cork in apples; lop-sided fruit and heavy fruit shedding of citrus; ‘shot’ berries and poor fruit set in grapes; flower shedding with deformed and bumpy fruit. It also affects growing tips (i.e. dieback) and leaves. Small clover leaves may indicate boron deficiency.

In the soil boron is an anion and therefore is found mainly the soil solution or complexed with humus.

Marine soils may have high B reserves. Deficiencies can be worse in long dry spells and in high pH soils. Kiwi Fertiliser recommends Organibor, a natural magnesium-calcium borate from Argentina. Organibor is non-toxic. however, it is relatively slow acting, particularly in a dry season, so may need to be applied early in the season, or some Ulexite may need to be added as well, particularly for short-term crops such as turnips. Organibor boron levels in the soil stay higher for longer with Organibor.

Without boron, the plant cannot transfer sugar from leaves to the roots. This process is also interrupted by various cultural practices, i.e. girdling.

In animals, boron helps regulate both calcium release into the blood and calcium absorption. Boron helps convert vitamin D into an active form which facilitates calcium absorption. Silicon and calcium together are cell strengtheners but they both require boron to deliver their benefits. Boron encourages silica to form silicic acid which then moves into the plant to form nutrient highways which then help to move the poorly translocated calcium into the plant. Required at 2ppm in the soil.

Boron deficient lucerne compared with a normal tiller.

Organic matter is important to be able to build anion levels in the soil. (Figures in ppm.)

Sodium (Na) should measure between 0.5 and 3% on the base saturation. It is rarely deficient (there being 6 ppm in rain), and should not (but sometimes does), exceed potassium in base saturation as sodium will be taken up by the plant instead. On hot days, this can lead to cell walls bursting and the plant dehydrating. In severe cases, the plants, including pasture, can die.

According to Perry Agricultural Soil Laboratories (PAL) results, we have yet to see a situation that warrants sodium being added to fertiliser. However, we have observed the negative effects of excess sodium, when applied to fodder beet.

If sodium is in excess, correct the calcium first, then use sulphur to reduce sodium if it is still in excess.

Sodium is involved in osmotic (water movement) and ionic balance in plants. Na may be important in some plants such as sugar beet, but is less so in fodder beet.

A major mineral is missing in many soils and most soil tests do not even monitor its presence. This mineral can increase stress resistance, boost photosynthesis and chlorophyll content, improve drought resistance, salt tolerance and soil fertility and prevent lodging. lt can also reduce insect pressure, frost damage and destructive disease while lowering irrigation rates, neutralising heavy metal toxicity and countering the negative effects of excess sodium. If I were to tell you that this same missing mineral can increase root growth, boost yield and enhance crop quality, you could well ask, “how could we have overlooked something so important?” and you would be correct. It has been a serious oversight. The mineral in question is silicon, and science is rapidly revealing the scope and scale of our silicon neglect.

Poverty in a Sea of Abundance

Silicon is not classed as an essential nutrient, but, in response to a wealth of new findings highlighting the importance of this nutrient, that status may soon change. Silicon is the second most abundant mineral on the planet. It is everywhere. Clays are alumina silicates and sand is largely silicon, so how could there be a shortage of silicon? The answer lies in the form of silicon that enters the plant. Plants uptake silicon as silicic acid and this is what is missing in the soil. Something we have done in conventional agriculture appears to have compromised the conversion of insoluble silicon into the plant available form. It may reflect a mineral imbalance or we may have knocked out some of the soil microbe species that solubilise this mineral. It is not yet understood what drove the widespread deficiency but we do know that a healthy, disease suppressive soil should contain 100 ppm of monosilicic acid (as measured in a soil analysis) and very few soils come anywhere near that mark!

Little was known about the multiple roles of silicon until recently. It was known to be present in every soil but it was only when it became less plant available that it was realised that there may be a link between this loss and a host of growing problems. During the last decade, silicon seems to have become “flavour of the month” in the soil science community. Researchers have delved more deeply and hundreds of papers have been presented at the International Silicon Conferences in Brazil and South Africa. This neglected mineral is now emerging as a key player in proactive pest and disease management and the production of nutrient dense food. If you are not yet aware of the silicon story then this article should serve to fill some gaps.

Cell Strength is Resilience

The cell wall in plants is a substantial barrier that must be breached to gain access to the goodies within. A fungal pathogen must drill through this wall with its hyphae to be able to tap into the nutritious cell centre. Once this goal is achieved, the pest has the food source that sponsors its spread, and a disease is born. There is an obvious opportunity here to stop the pathogen in its tracks. What happens if we strengthen that cell wall so that the hyphae buckle? It’s simple – the disease cannot gain a foothold and will not spread. Similarly, why would a leaf eating insect choose to wear out his eating gear on silicon-strengthened rock cakes when it can go elsewhere for sponge. Many published papers have now confirmed the exciting potential for increased disease and insect resistance through good silicon nutrition. In one paper presented at the South African conference, soluble silicon used as a soil drench had the equivalent inhibitory effect as phosphorus acid in the management of phytopthora in avocados. However, the silicon-treated plants had much more vigorous roots and canopies. In another case silicon was shown to offer effective management of dreaded black sigatoka in bananas. Other papers reported efficacy against brown rust in sugar cane, powdery mildew in cucurbits, fusarium wilt in potatoes and leaf blast in rice.

Interestingly, the plant understands the protective potential of silicon, even if we don’t. When a disease begins, the plant directs all available silicon to the attack site, to strengthen the surrounding cells and stop or slow the spread of the pathogen. There is a problem here, though, because silicon is immobile once incorporated into the cell wall. It must be in constant supply so that the plant can utilise it at these times. Most soils contain less than half of the soluble silicon required so there can be significant benefits in foliar spraying silicon at the first sign of a disease. This can stop the spread of the disease and many growers are successfully using this strategy.

Silicon and Sun Power

Photosynthesis is the most important process on the planet. The green plant is the only source of food and the management of chlorophyll, the green pigment where all the action happens, is the chief role of the farmer. Silicon is a gold sponsor of the sugar factories within the plant as it supports this process in several ways. The leaf is essentially a solar panel, the underside of which also serves to capture the CO₂ gas as it rises from the roots and soil life. The better that panel is presented, the more efficient it will prove in capturing sunlight, water and CO₂ (the three components of photosynthesis). Silicon strengthens the stem and holds that panel in perfect position. The plant is less likely to droop in warm conditions and more likely to maximise photosynthesis.

Minerals are the major players in the photosynthesis equation. Blotches, stripes and pale colours, from shortages of minerals, represent the mismanagement of chlorophyll. Sometimes it’s not just the lack of these nutrients but their delivery into the crop that is the issue. Silicon can have a big impact upon mineral uptake. Phloem and xylem are the pathways that govern mineral absorption and the translocation of minerals within the plant. These nutrient highways are built from silicon and their performance will suffer in its absence.

Calcium is an example of a poorly translocated mineral that will be utilised more efficiently when the nutrient highways are broad and true. Boron is a calcium synergist, which can improve the performance of calcium, but it has recently been recognized that boron also boosts silicon uptake.  Boron solubilises insoluble silicon and it is a good idea to combine boron, calcium and silicon in your program to maximise the synergistic potential of the trio. One popular strategy involves the application of boron to the soil in late winter to trigger the release of silicon. The soluble silicon will be used to build the super highways that will improve the sluggish uptake of calcium (needed for cell division during the spring flush).

Silicon – The Stress Savior

There are two types of stress that affect production negatively. Abiotic stress involves the negative impact of environmental factors upon living organisms and biotic stress is about pest pressure. Abiotic stress is the single most harmful factor impacting crop growth and productivity on the planet and it can only have more impact as global warming progresses. However, biotic stress is not far behind. Every year since we began the chemical experiment in agriculture there has been an increase in the total amount of chemicals applied on a global scale and every year there has also been a marked increase in pest pressure. The current path is not sustainable; in fact it is not working! There is an obvious relationship between abiotic stress and biotic stress in that environmental factors will increase pest pressure. We are seeing this in all of the countries in which we work. Even in the local ginger industry, right on our doorstep, growers are experiencing pythium pressure unlike anything they have previously experienced. This destructive fungus has found a new niche in the wettest growing season ever. This does not represent a deficiency of fungicides but rather it highlights the desperate need for a more holistic approach that will offer a greater level of inherent protection during times of stress.

Silicon can reduce the impact of both abiotic and biotic stressors and it represents an essential component of a program designed to create a disease suppressive soil and stress resistant plants. The stronger the cell wall, the more stress resistant the plant, whether that stress is from pathogens or non-living factors.

Part of the climate change forecast is an increase in extreme weather events. Wind can be particularly destructive in that it can promote lodging, which can render the crop unharvestible. At the most recent silicon conference, Iranian researcher, A. Fallah, presented a paper reporting a reduction of silicon within the plant associated with high nitrogen usage. It is already understood that over application of nitrogen has a nutrient diluting effect and that the mineral most affected is potassium. Now we understand that mismanagement of nitrogen can also impact silicon nutrition and the associated protective effect of this mineral. In this instance, weaker stem strength and increased susceptibility to lodging were noted in the rice crop studied. Fallah reported much stronger stems and resistance to lodging in silicon treated crops.

One of the stressors that is becoming more of an issue in many soils is the oversupply of heavy metals, salts and some trace minerals. In all cases, silicon has been shown to mitigate the stress. Copper (Cu) can build up in the soil due to the overuse of fungicides. We have found humates a valuable tool to neutralise the negatives associated with this excess. Silica has been effective in mitigating the effect of a variety of heavy metals but recent US research suggests that silicon may be a viable management tool in high copper soils. J. Li, J. Frankz and S. Leisner working in flower crops in Ohio, found that silicon could very effectively mitigate Cu toxicity stress and the improvement was measured on multiple levels.

Swedish researchers working in cadmium contaminated soils found that the higher the silicon level in the plant, the lower the cadmium level. In fact, there was 60% less cadmium in the silica treated food grains.

In some exciting Russian research involving wheat, silica was shown to alleviate salt stress quite dramatically. Wheat is notoriously sensitive to high salinity and the salt created a major decrease in photosynthesis. The addition of silicon to the soil resulted in increases in photosynthesis ranging from 158% to 520% depending upon the salt concentration in the soil. This is one of several studies highlighting the silicon link to salt management. We always recommend the inclusion of small amounts of humic acid and potassium silicate with every irrigation, to manage saline irrigation water.

A South Australian study reported reduced drought stress and an associated reduction in pest pressure following silicon treatment. This study found that applied silicon mitigated the increased insect pressure that was a direct effect of high levels of nitrogen. Not only does high N shut down silica uptake but applied silica can also compensate for this nitrogen mismanagement.

Cold stress can even be addressed with silicon. South African scientists working with bananas have shown that silicon protected the plants from cold damage and that an associated increase in vigour decreased the banana’s susceptibility to Fusarium Wilt.

This enhanced protection from disease has been well researched. A recent Japanese study entitled “Silicon in the Control of Diseases in Rice, Sorghum and Soybean”, found reductions in brown spot pressure that varied between 35% and 75% in rice studies. They found significant reductions in anthracnose in silicon-treated sorghum and the results were quite dramatic when foliar applying potassium silicate to manage soybean rust. They concluded their paper with the following words; “The results of these studies underscore the importance of Si to increase plant resistance to foliar disease”.

This increase in disease resistance was originally thought to be related to the “barrier effect” linked to increased cell strength, but it is now understood to be also related to increased plant immunity.

Silicon-Based Immunity

One of the most dynamic research streams in agricultural science relates to the investigation of plant immunity and the triggers that activates the plant to fight its own battles. It is now understood that the plant has an immune system, which can be both monitored and magnified. Salicylic acid, for example, the biochemical upon which aspirin is based, activates the plant’s immune system. Aloe vera is the richest natural source of this compound and many of our growers benefit from the inclusion of this plant extract in their programs.

Recently, silicon has been found to trigger the production of a suite of compounds that fuel immunity. This mineral is now seen as an integral tool in proactive pest management as it offers both protective cell strength while also fuelling a robust defense system.

Phenolic compounds are one of the biochemicals that are part of this defense system and these compounds are now recognised as key players in the protection of avocado trees from Phytopthora cinnamoni. T.F Bekker, et al, from the University of Pretoria, conducted research which demonstrated that soil applications of potassium silicate to soils affected by this disease, increased the total phenolic content of the avocado root tissue.

It is interesting to note that this silicon-based, immune response is most pronounced when there is existing disease pressure. It’s almost like the plant calls in the heavy artillery when the going gets tough! A Canadian paper presented at the South African conference involved the study of 30,000 genes. The researchers reported that unstressed plants appeared to be minimally affected by silicon feeding with the associated upregulating of only two genes. (Note: upregulation is the process by which a cell increases the quantity of a cellular component such as RNA or protein in response to an external variable.) However, in stressed plants (affected by powdery mildew) there was an upregulation of a number of genes. A Spanish paper also covered the Powdery Mildew control potential of silicon and they found that the inclusion of amino acids with the silicon fertiliser enhanced the response.

Russian researchers have hypothesised that the plant immune system requires mobile silica compounds and if there is luxury levels of silica available to the plant there will be additional synthesis of stress protection molecules. A co-operative research effort between American and Japanese scientists showed that silica related resistance involves multiple pathways and that silica amendment clearly alters plant defense signaling, increasing the plant’s disease resistance.

But There’s More

Not only does silicon offer increased pest and stress resistance. It can also provide a major fertilising response and substantial yield increases. In a paper by J Bernal, involving research with rice and sugarcane in Columbia, just 100 to 200 kg of magnesium silicate per hectare achieved yield increases of 14.63% in sugar cane and the increases in rice ranged from 21% to 33% (depending upon the application rate). Iranian research with rice mirrored the South American findings but in this case the yield increase was 22% after applications of 500 kg of silicon. Rice and sugarcane have been most researched, as they are recognised silicon accumulators. In fact, rice has the highest levels of silicon of any crop. However, we have found that most crops respond to silica and research is now quantifying our infield experience. Brazilian researchers trialed six different application rates of potassium silicate on potatoes and found that the1% rate was most effective. In fact, 6 litres of potassium silicate in 600 litres of water, sprayed each week during the crop cycle, produced an impressive yield increase of 22.4%.

Australian, M. Lynch, a champion of silica fertilisers for over a decade, presented a paper at the SA conference where he suggests that silica fertilisers have consistently outperformed high analysis fertilisers in cereal production. This has included increased protein levels, increased yields, decreased screenings and increased grains/heads. He contends that silica fertilised grapes have superior skin quality, higher brix values, uniform bunch size and a virtual absence of fungal diseases.

At NTS, we have often found unexpected benefits when including silicon in programs. An avocado grower from North Queensland found that he no longer lost up to 15% of his crop to wind abrasion. The increased skin strength created fruit that did not mark when the fruit rubbed against the branches in windy conditions. Golf courses often report that the greens are wearing better following applications of liquid, micronised diatomaceous earth (a rich silicon source).

Silicon and You

If plants respond so favourably to silicon, what about humans? One could assume that if most plants are silica deficient then most people would also suffer from a shortage of this mineral. The Japanese Government has certainly recognised this problem and have strongly encouraged the use of soluble silica on rice crops.

H M Laane from the Netherlands, presented a research summary of human health research into silicon. The human body contains 7 grams of silicon, which is more than all the other trace minerals put together. High levels of this mineral are deposited in bones, nails, tendons and the walls of the aorta and substantial amounts are found in the kidneys, liver and lungs. Silica intereacts with several minerals but important research has highlighted the use of silicon as a means of inhibiting aluminium toxicity. Aluminium has been strongly implicated in the plague of Alzheimers disease which now sees 1 in 4 Westerners over 65 succumb to this disease.

Silicon is also a calcium synergist and should be included in all good calcium supplements. H M Laane concluded that dietary levels in Western diets are too low and there is a coincidence with increased skin, hair and nail problems, osteoporosis and Alzheimer’s disease. There are also obvious benefits in silicon-strengthened arteries.

Fertiliser Sources of Silicon

Silica fertilisers are available in liquid and solid form and the liquids offer the most rapid response. Silicon is found in good levels in rock mineral fertilisers and in rock phosphate and guano products. However, this is not the plant available form of the mineral and, depending on the particle size, it may take many years for the mineral to become available. This is not the case if the fertiliser is a calcium silicate or magnesium silicate but you need to ask about the solubility of any silica fertiliser you may be considering. This is also not the case if these materials are micronised.

Diatomaceous earth in the amorphous form is a very rich source of insoluble silica. The material is basically the exoskeletons of tiny prehistoric creatures called diatoms. These remains contain up to 85% silica dioxide and the silica shell is sharp and jagged under a microscope, almost like a broken razor blade. Diatomaceous earth has been used as a natural insecticide for decades, as the jagged, little razor blades can cut up the offending insect’s exoskeleton causing the creature to dehydrate and die. This material is also used internally as a natural means to control intestinal parasites. The rich silica lode from diatomaceous earth can be made plant-available by micronising the material right down to a tiny particle size of 5 microns. It can then be held in a liquid suspension and applied via boom spray or fertigation. As little as 5 litres of liquid, micronized diatomaceous earth per hectare, applied through fertigation on a regular basis, can lift leaf levels of silica into the luxury zone, with all of the associated benefits.

Potassium silicate is a good soluble form of silica but it is not compatible with many other fertilisers and must often be applied as a standalone or with boron. One way out of this limitation is to use a pre-formulated potassium silicate-based fertiliser which includes other synergists.

In Conclusion

Proactivity is the essence of the biological approach. If you understand how plants protect themselves, then you provide the necessary components to maximise that process and minimize the need for chemical intervention. In this context, silicon is an essential pre-requisite for proactive pest and stress management and should be an integral part of every good nutrition programme.

Many thanks to Graeme Sait NTS Ltd

Nitrogen is the most abundant nutrient required for plant growth. It forms 16% of all plant proteins, and is a vital component in chloroplasts - the factories that synthesize energy from sunlight. N management is one of the most important issues in our quest to build both profitability and sustainability. Excess N burns out organic carbon and contributes to the “Greenhouse Effect”. Nitrogen toxicity is a significant cause of loss in production when nitrogen is overused or misused. Potassium and calcium will inevitably be deficient when plant nitrgen levels are excessive. Nitrogen and potassium imbalances in plants is also a major disease "calling card".

Currently nitrogen losses account for up to 50% of applied nitrogen. Nitrates contaminate waterways, groundwater and drinking water; remove oxygen from the blood and are proven carcinogens. Excess nitrates in plants encourages pest and diseases to flourish. Brix levels in plants cannot be raised with excess nitrates. Excessive N causes the top to outgrow the weakened roots i.e. “nutrient dilution” which seriously reduces yield and quality.

Good nitrogen management increases quality - the key to increased profitability. We need to concentrate on capturing free nitrogen from the atmosphere; each hectare has the equivalent of over 74,000 tonnes of nitrogen above it in the atmosphere.

Deficiency symptoms include yellowing of older foliage (being mobile in the plant it transfers from older to younger leaves); reduced plant-leaf size and "ground" cover. This all amounts to fewer solar panels -> less photosynthesis -> less sugar -> lower yield and quality. Fewer stems; dwarfed plants; thin and upright habit; stems and petioles rigid; reduced tillering in cereals. 150 - 200 million tonnes of N are utilised in agricultural each year. The vast majority of nitrogen comes from the atmosphere via nitrogen fixation by soil microbes into plant available ammonium and nitrate, as well as lightning and rain which oxidises nitrite to nitrate.

Atmospheric nitrogen is the cheapest form of Nnitrogen you can get.

Modern misuse of nitrogen

Most nitrogen is applied in large amounts early in the season results in large amounts of nitrate at the crucial, fruit-filling phase of crops. The pH of plant and soil go out of balance therefore the crop is subjected to nutrient deprivation, pest and disease attack plus misuse of all important photosynthates needed for maximum yield.

Nitrogen management - keeping excesses to a minimum.

1) CEC of your soil. Lighter soils require spoon feeding. When ammonium can’t store on clay or humus colloid, nitrate conversion is guaranteed.

2) Soil balance improves nitrogen efficiency; calcium is “the trucker” and is essential for uptake, while sulphur is necessary for conversion of nitrates into essential amino acids. High or low magnesium soils require at least 50% more nitrogen to achieve the same yields as soils with correct magnesium.

3) Crop rotation, pasture composition; legumes can leave considerable quantities of nitrogen in the soil for use by other crops.

4) Levels of humus and organic matter. Undigested OM present during a crop cycle can consume considerable amounts of nitrogen during decay causing nitrogen drawdown. Begin stubble digestion with shallow incorporation immediately after harvest.

Radioactive tagging methods have shown that every 1 kg of nitrogen supplied over and above plant requirements will burn out 100 kg organic carbon. Microbes devour nitrogen and carbon in set proportions.

Adding compost protects valuable soil organic carbon. Always add carbon to nitrogen.

5) Cover crops protect the environment from free-roaming nitrates. Winter cover crops help reduce nitrogen leaching. Barley, oats and triticale are planted between vine rows of vineyards and similar to help capture nitrogen and recycle it following incorporation. By the time the primary crop is harvested, the remaining nitrogen is in the nitrate form via nitrification. Cover crops take up nitrates for early vegetative growth and convert them into proteins, thereby stabilising the nitrogen. Decomposing protein then releases ammonium to be taken up by plants or converted back to nitrate where it is still in a plant available form.

6) Manure and compost application: the nitrogen content should always be factored into the equation.

Nitrogen forms the basis of amino acids and proteins, the building blocks of life; an essential constituent of nucleic acids, DNA, RNA, and enzymes, which are all made up of proteins. It is a necessary component of vitamins biotin, thiamine, niacin and riboflavin.

Nitrate is paramount to the formation of chlorophyll which is the green pigment within chloroplasts where photosynthesis takes place. The central part of the chlorophyll molecule consists of a magnesium atom surrounded by four nitrogen atoms plus carbon, hydrogen and oxygen.

Protein is decomposed by aerobic soil organisms and the nitrogen is released from these organisms as ammonia gas which is quickly converted to plant available ammonium in ideal situations.

Forms of nitrogen in fertilisers and their impact on soil and plants.

Ammonium – ammonium sulphate, mono-ammonium phosphate, di-ammonium phosphate

Nitrate – potassium nitrate calcium nitrate magnesium nitrate

Urea (NH2-CO-NH2) is in the amine form. The most commonly used nitrogen source in agriculture. The cheapset product, but notoriously unstable, and with negative down-stream consequences.

Zeolite: capable of holding onto nitrogen (especially ammonium) and is a permanent addition to the soil and increases its water and nutrient holding capacity.

Humates: as liquid or granules which dissolve at the same rate as urea; can extend the life of nitrogen in urea by 60 days. Humic acid should be used at a rate 5%-10%. Humic acid also provides a source of food for microbes.

Ammonium can attach to negative soil particles or form compounds with nitrates, sulphates or phosphates, and will be plant available and secure from leaching.

However, in warm, moist conditions, microbes quickly convert ammonium to nitrate which can then be leached away. Stabilising with humic acid and zeolite will help slow down nitrification.

The conversion of ammonium to amines to amino acids occurs in the roots. The energy used causes plants to send more sugar to the roots. The plant is then stimulated to produce more chlorophyll.

The increase in photosynthesis is the reason why ammonia turns leaves dark green and actually results in net gain of energy to the plant.

Nitrate is the end product of nitrification. Most fertiliser applications force plants to take in nitrogen in this form during the production phase of the crop. This goes against nature’s intentions. That is, nitrate should go in during the vegetative stage of the crop and ammonium during the reproductive stage of the crop. Nitrate conversion to amine (NH2) is an energy expensive process which relies on sunlight and Molybdenum to enable the nitrate reductase enzyme to be activated. Ammonium from decay is released near live plant roots and taken up before nitrification takes place.

The pH surrounding the rhizosphere is low to stimulate soil microbes and promote the uptake of nutrients to stimulate further production of chlorophyll. Nitrates are needed for cellular pH maintenance, obtained through decomposing organic matter on the soil surface which goes through nitrification. Also nitrogen is made available from atmospheric oxidation of nitrgoen, nitrate and rain carrying nitrate to roots.

The nitrogen cycle

Organic matter is important to be able to build anion levels in the soil. (Figures in ppm.) The higher the OM, the higher the anions.

Sulphur is important for protein synthesis being a component of two essential amino acids, cysteine and methionine. It is required for the formation of vitamins and chlorophyll, as well as the development of legume nodules. It is a component of certain oil compounds creating a distinctive odour and flavour to plants such as onions, garlic and brassicas. Sulphur aids in the translocation of sugars and starches to the roots. Early morning brix levels may be high when sulphur is low. It activates nitrate reductase, so is essential for the conversion of nitrate to amino acids. When sulphate is deficient nitrate accumulates and protein levels decrease. Disease pressure will increase. Sulphur is required in amounts similar to phosphorus. 

Deficiency symptoms are very similar to nitrogen deficiency symptoms i.e. pale green leaves, but usually on young leaves, although can be on older leaves in some plants such as tobacco and cotton. 

They include small and spindly plants; delayed maturity; reduced nodulation in legumes and fruits that do not fully mature. Other symptoms are dependent on species e.g. spotting on potato leaves 

In the soil sulphur occurs as a negative charge sulphate ion: not attracted to soil clay, therefore easily leachable 

Monitor soil levels regularly, particularly sandy soils; good organic matter levels will hold onto sulphur. (See table below.) 

Sulphur is good for leaching excess cations. E.g. 2 kg of sulphur will reduce 1 kg of calcium, potassium or sodium if they are in excess. If excesses of calcium, magnesium, potassium or sodium exist, sulphur levels will not build in the soil. Sulphur may leach calcium or other cations when they are not in excess in coarse, open volcanic soils, particularly those found on the central plateau.       

The main form taken up by plants is sulphate (SO4). Crops also have the ability to take up sulphur through their stomata in the form of gaseous sulphur dioxide, SO2. 

In animals sulphur is a component of protein. It is important for collagen synthesis, being present in large amounts in hair, skin and hooves. Sulphur is also involved with the B vitamins biotin and thiamine, and the hormone insulin. Sulphur must be present for stock to receive essential amino acids.

Organic matter is important to be able to build anion levels in the soil. (Figures in ppm.) The higher the OM, the higher the anions. 

Soil samples taken by Kiwi Fertiliser consultants are sent to Perry Agricultural Lab (PAL) in Missouri. After analysis, Kinsey Agricultural Services (KAS) (who receive samples from 70 countries world-wide,) make the appropriate recommendations. Regarding the order of deficiencies found Potassium and Sulphur are invariably at the top of the list.

Potassium (K) is involved in nearly every aspect of plant growth. It does not become an integral part of the plant, unlike silicon and calcium that become the main components of the cell wall; and magnesium and nitrogen that are the main components of the chlorophyll molecule. This is the reason why cut hay is so vulnerable to potassium loss due to rainfall.

Potassium is second only to nitrogen in terms of quantity taken up by a plant. K is involved in the regulation of around 50 enzymes in a plant. It is needed to convert nitrogen into protein thereby reducing the amount of non-protein nitrogen (nitrate) in the system. It facilitates the movements of sugar and starches and is important in sizing up fruit and grain and preventing build-up of sugars in chloroplasts. K influences stomata regulation. Stomata can open to seven times their original size, therefore influencing gas exchange for photosynthesis and drought resistance and/or water efficiency.

The positive benefits of adequate K fertility are:

Deeper rooting. K helps plant roots penetrate to access deeper soil water.

Faster closing of the crop canopy. When the crop canopy closes, the ratio of transpiration to evaporation increases, which means more of the available water is used by the crop.

Greater osmotic gradient. The more K inside the plant cell, the better it can attract water from the soil, and control water loss.

Earlier maturity. Adequate K ensures plants get through to the critical pollination period before possible drought.

Stomata can open approximately seven times their original size. Therefore if potassium is deficient the plant will not receive adequate CO2, moisture and nutrients from the environment or foliar sprays. That will also affect the plants ability to cool itself. K is quite mobile in the plant and moves to the young leaves, therefore symptoms show in the old leaves first.

Only a fraction of potassium is available at one time

The visual signs of K deficiency are similar to nitrogen deficiency; yellowing of the pasture, browning off of the tips of grass blades, and prominent urine patches. If clover growth in urine patches is much stronger than in the rest of the pasture, K deficiency is likely.

Potassium is an alkalising mineral, so when potassium is low the fruit can be acidic and therefore taste sour. It is also due to the fact that potassium is not sufficient enough to transport good levels of sugars and nutrients into the fruit. The plants resistance to pathogens is reduced. Fungi tend to attack crops at low pH. Low pH simply means too much hydrogen and not enough nutrients.

About 90% of the potassium found in soils is insoluble. This source is released by microbial activity and weathering over time. K+ is attracted to, and hence stored on, the negatively charged clay colloid. The humus colloid has less attraction, but is also capable of storing potassium.

Severe potassium deficiency in Lucerne

Maize just starting to show potassium deficiency

Plants access potassium via the soil water. In sandy soils, there are very few storage surfaces for potassium, so some is carried away in the soil water. In light soils, (i.e. soils with a CEC<10) humus can make a significant difference in increasing the potential for potassium retention and storage. Leaching is particularly prevalent in light sandy soils where spoon-feeding potassium may be the better strategy. Animal urine contains 80-90% of the potassium excreted by animals.

Excessive magnesium leads to tight soils which in turn traps potassium in the clay layers. Improving the Ca% in the soil alleviates this problem. In high Mg soils, more K is required to reach that soils higher production potential. The problem of tight soils is alleviated by opening up the soil structure, leaving more space on the external colloid for K to attach to. When pH exceeds 6.5 there is no space for increasing K levels on the colloid. All spaces are filled up with existing cations rather than hydrogen, which can be readily bumped off. The same problem essentially occurs in dry soils where the soil solution and diffusion needed does not occur. K levels cannot be built when pH is 6.5 or higher; unless you use compost or manure. If you have a high pH, just use maintenance levels of K until the pH comes below 6.5.

When the base saturation of potassium gets greater than 7.5%, weed pressure increases, boron is tied up and often pastures become less palatable. Soil structure tends to decline because the K ion is dispersive (much like sodium), which contributes to poor soil structure and eventual collapse of the soil particles. Crops will struggle (particularly wheat) when the K% is greater than Mg.

Adding K to the soil is easily achieved for crops, but can be problematic where livestock are concerned. It needs to be done with caution and after magnesium and calcium levels have been addressed. It may be safer to apply up to 60 units after mating, but this does depend on individual farms’ soil balance, particularly having correct Mg & Ca levels.

With PAL test results, sodium should never be higher than K. If K + Na exceed 10% of base saturation, manganese uptake will be blocked. That may show up as excess bull calves born over heifer calves. When the soil is properly balanced, the ratio can be 60:40 in favour of heifers.

Potassium Sulphate is superior to Potassium Chloride! Potassium chloride raises the brix of many weed species, lowers the brix of many crop species and acts as a biocide.

More Energy. It costs more per unit, but delivers better value. Money spent on potassium sulphate (K2SO4) will purchase less fertilizer by weight than will one dollar spent on potassium chloride (KCl) but the dollars spent on potassium sulphate will buy significantly more crop growth energy. 47% of KCl is choride and of little use for crop growth. In contrast almost 100% of potassium sulphate is useable by the plant.

Lower Salt Index. K2SO4 has a salt index of 46. KCl is 116. The higher the index, the greater the chance of damaging germinating seeds, seedlings and soil biology.

Better Uptake of Potassium. Uptake of potassium requires it to be in the phosphate of potassium form. When there is an excess of chlorides the bonding of potassium with phosphate is blocked. The end result is less potassium uptake into the plant in the preferred form. The sulphate form does not overwhelm the soil solution with chloride ions and consequently more potassium is taken up by the plant.

Microbial Stimulation vs. Microbial Suppression Sulphates have a stimulating effect on the microbial system in the soil whereas chlorides at high levels are very hard on soil biology and are never recommended by creditable sources. A small amount of chloride is actually beneficial for soil microbes. This modest requirement is easily met by the 1-2% in potassium sulphate. High rates of chlorides can destroy soil carbons. Humus destruction leads to greater N leaching as soil N levels are dependent on humus levels. The better the humus percent, the more anions (particularly nitrate, sulphur and boron), held in the soil.

Plants and soils need Sulphur. Most soils are sulphur deficient. In order for plants to make oils and sulphur bearing amino acids such as cysteine and methionine the plants need an adequate supply of sulphur in the sulphate form. This is exactly what potassium sulphate supplies.

Better palatability. Pastures, crops, vegetables and fruit taste poorly when the potassium comes from potassium chloride (that’s right, cows prefer K2SO4). This happens because chlorides are also taken up by the plants. Fruit and vegetables grown with calcium chloride taste bitter; this is the main reason why children reject vegetables.

Less is more. The application of 100 kg of potassium sulphate will give a greater plant response than 200 kg of potassium chloride. This relates to a soil where the cations are balanced and soil potassium is adequate.

Below is a passage written by Jerry Brunetti, as part of an article titled “Cows don’t have carburettors” and was published in Acres USA, May 2012. The title seems absurd; it is extremely relevant.

Unfortunately, livestock operators, especially in New Zealand, are being sold a big lie as to how to grow forages, applying huge amounts of urea and super phosphate for yield while dropping the energy levels of the forages, increasing the “funny protein” (nitrogen), obliterating the biodiversity of forbs (forage herbs) rich in phenols, carotenoids/terpenoids, and complexing those vital elements in the soil, namely calcium, magnesium, sulfur and boron that are responsible for creating quality protein and forage diversity.

Many New Zealand farms have acidic soils (e.g., pH of 5.5). Yet, their soil analysis showing a P2O5 “deficiency” was derived from an “Olsen Test,” to be used on alkaline soils. Thus these soils show a continued “need” for super phosphate, even though some soil tests that we reviewed contained 4,000 pounds per acre of phosphate when they were analysed. All of this excessive phosphate locks up whatever calcium and magnesium is present, denying the plant an ability to synthesise both quality protein and quality forage calories in the form of pectins and hemi-cellulose.

Mycorrhizal fungi can multiply a plant's ability to extract phosphate by many hundreds of times.

Moreover, the excess phosphate drives the critical mycorrhizal fungi out of the rhizosphere, depriving that organism’s contribution of phosphatase enzyme, needed to extract complexed phosphate and trace elements out of the soil. Thus over-applying phosphate ironically leads to a deficiency of plant phosphorus, needed to produce ATP (adenosine triphosphate), the energy currency in the Krebs cycle for both plants and animals.

What does it all mean? Neal Kinsey, of Kinsey Agricultural Services (KAS), a true adherent to the Albrecht principles of soil fertility, advises all his clients, (which include countless consultants in over 70 countries around the world), to use Perry Agricultural Laboratories (PAL) for their soil tests. PAL uses the Bray II (root acid soluble) test for soils with pHs up to 7.5. Once the pH gets to 7.6 and above, they provide an Olsen P test result. Since there are at least 12 tests to choose from, why do NZ labs use the wrong one? The Americans use it appropriately and we in NZ have been led to believe it is a true measure of our soil P, when it is not.

On average, most of acid phosphates tie up or complex with aluminium, iron, manganese and calcium, within six weeks; sometimes within hours of application. But, super’s big marketing ploy is its low cost. How cheap is a material that is on average not very effective? Remember, chemical agriculture is a self-serving, input-driven system. You are advised to apply an unbalanced fertiliser to an unbalanced soil to help sustain a state of imbalance, which will then require constant chemical intervention. Now we have an inappropriate P test and an inappropriate product. When compared to alkaline phosphate products the answer comes out very much in favour of alkaline products such as guano, Sechura RPR, dicalcic and DAP. If needed, you can quickly build soil P levels with those products without those tying-up problems.

Sinclair** et al (1997) took the average curve and examined how good it was at explaining the relationship between % relative pasture yield and Olsen P values at 17 of the 19 sites. The result (Figure 4.1.16) (of the Massey University “Sustainable Nutrient Management in New Zealand” manual) is somewhat sobering! Sinclair et al (1997) concluded that Olsen P soil tests from farms could not accurately predict relative pasture yield. These data, however, did show that when Olsen P values exceed 20 a near maximum relative yield can be produced.

When we add the demise of mycorrhizal fungi (VAM) into the equation, the situation becomes even clearer. There is little or no reason to use superphosphate, as the VAM increases the effectiveness of phosphate uptake of roots by up to 1000 times. Loss of VAM leads to increased soil erosion and leaching of nutrients from the soil. When the VAM is lost, some other organism will take its place. Usually it is a pathogenic organism. Since properties I have worked with have no facial eczema, it seems a good bet that those using alternative phosphates will also not be bothered by that terrible affliction.

As for excess phosphate in the soil, on reviewing soil tests taken on flats, 90% had an excess, some being in the plus 700kg bracket. The hills were a different proposition as 86% were deficient.

The difference between rock phosphate and acid phosphate (USA data)

Not only do we have criticism from USA regarding the use of the Olsen P test; we also have it from New Zealand. It appears the use of the Olsen P test was chosen in the 1970’s for no other reason than it being the latest test. It appears fertiliser companies have used the Olsen P test ever since for the purpose of selling superphosphate, a product that they manufacture; not because the farms actually need it.

In general, and depending on location, Kiwi Fertiliser finds P levels of NZ soils to be excessive. Where phosphate is required, we recommend Sechura RPR.

As for excess phosphate in the soil, on reviewing soil tests taken on flats, 90% had an excess, some being in the plus 700kg bracket. The hills were a different proposition as 86% were deficient.

* The late Jerry Brunetti was managing director of Agri-Dynamics, which specialises in products for farm livestock and pets, and consults on a wide variety of other issues. He used to be reached at Agri-Dynamics, P.O. Box 267, Martins Creek, Pennsylvania 18063, phone 877-393-4484, email info@agri-dynamics.com, website www.agri-dynamics.com

(**The late Dr A G Sinclair, AgResearch, Invermay Agricultural Centre.)

Chlorophyll provides the vital interface that connects the light energy from sun to all life on earth via the process of photosynthesis.  The magnesium atom is at the centre of a chlorophyll molecule; without it photosynthesis would not be possible. It is like the plug on the end of an extension lead, and it plugs all life directly into the suns energy.  Magnesium plays a similar role in plants to that of iron in the structure of haemoglobin in animals.

Managing plant growth is about managing photosynthesis.  The more energy from the sun the plant can collect, the more it will yield.  Any limiting factor that inhibits maximum photosynthesis is one that will limit crop productivity.

Look for luxury levels of magnesium in leaf analysis. It is vital for photosynthesis and phosphorus uptake; the energy system of the plant.  You can apply as much nitrogen as you like, but without adequate magnesium you will receive poor photosynthetic responses.

Magnesium is:

• essential for the metabolism and translocation of carbohydrates
• an enzyme activator, and a cofactor in synthesis of amino acids and proteins.
• included in beta-carotene, a precursor to conversion to Vitamin A.
• required in many enzymatic reactions for metabolism of compounds.
• found in fruit and vegetables, and the body converts magnesium to vitamin A when required.
• abundant in antioxidant properties.
• important as an anti-cancer agent and in reducing parasites on stock, e.g. fly strike, Barbers Pole Worm and many others.
• often the missing link for hypomagnaseamia (grass tetany) or downer cows. 

Magnesium reacts with phosphorous to enable phosphate compounds (Magnesium ATP) to be carried around the plant; particularly helpful in translocation of phosphorus into seeds of high oil content and for superior seed germination.

Ca:Mg percent is the most important relationship in soil fertility.  Light soils will require more magnesium than heavy soils. This is due to the properties of the magnesium atom which are much smaller than Ca and aids in the tightening of the soil structure to prevent excess leaching. Required at 10.1-12% of base saturation, but should be up to 20% in very light soils.

Magnesium has more impact on soil pH than Calcium due to its smaller atomic size (more surface area available to alkalise soil).

Calcium, magnesium, potassium and sodium are all alkaline cations and the more of these ions instead of hydrogen and alminium, the more balanced the soil will be. Magnesium can be easily leached, so magnesium deficiencies are more pronounced on acid and coarse textured soils. If low levels are present, use a combination of slow and quick release forms to ensure availability for the duration of the crop, e.g. Dolomite and Kieserite. The base saturation is made up of a combination of predominantly calcium, magnesium, potassium, sodium, and hydrogen. Any significant increase or decrease in any of these elements can ultimately increase or decrease magnesium base saturation.

After decades of using serpentine and its blends on the soil, why do we still have widespread magnesium deficiencies?

Dolomite is a magnesium and calcium carbonate combination that raises pH and soil magnesium levels and is very useful when both magnesium and calcium are required.

Magnesium carbonate, (Mag 2000) increases pH when magnesium but no calcium is required.

Magnesium oxide is created by the burning of magnesium carbonate to drive off CO2 has the highest concentration of all Mg fertilisers. Thermal alteration dramatically affects the reactivity of magesium oxide since less surface area and fewer pores are available for reaction with other compounds. Serpentine, a hard silica rock is also ineffective at raising soil magnesium, unless applied at very high rates, or is applied to very acid soils.

Magnesium sulphate is a good source when both magnesium and sulphur are needed, and can be used at the reproductive phase.

Defoliation can occur if magnesium is deficient while carrying a heavy crop. Monocots (grasses including sugar cane, cereals, maize, bananas) leaves’ can become striped; often along the full length, resulting in necrosis in the tip of the leaf. As maize plants age they have a more spotted appearance. It is relatively easy to build magnesium in the soil, but not so in the plant. We would like it to be 50 ppm, but realistically it is often less than half that figure; more often than not it is below 10 ppm. That may not be due to low magnesium, rather than low sulphur. Building sulphur may not solve it either. Calcium may be the key in this situation.

Magnesium is quite mobile and is translocated from older leaves to younger leaves under normal conditions, and is particularly obvious when there is a deficiency in the soil. 

Magnesium - the Unheralded Star  

Magnesium - by Neil Kinsey        

Dr. Linus Pauling, winner of two Nobel Prizes stated: "In my opinion, one can trace every sickness, every disease and every ailment to a mineral deficiency."

Magnesium deficiency in maize

Magnesium deficiency in potatoes