Phillip

Soil porosity is a measure of air space in the soil and macroporosity is a measure of the proportion of large pores in the soil that provide air supply to roots and microbes. Soils that have been compacted because of animal treading or machinery have poor macroporosity levels. This is like a foot on an individual’s throat, and they are saying they can’t breathe. It’s the same scenario for plants and microbes. Ag Research soil scientist Dr Peter Singleton and his team based at Ruakura Research centre, Hamilton, in the late 1990s found that a 10% macroporosity level in soils was a critical value in relation to pasture and crop production. It’s a useful soil physical field calibrated test developed for New Zealand soils. His research team found that there was a 10 % decrease in pasture production for every 1% decrease in macroporosity below the critical level of 10 %. Depending on the soil type, treading and compaction damage can reduce pasture production by up to 50% or more and take 6 months to 1 year to return to normal pasture production levels. When soil structure is damaged, the infiltration rate decreases and pores that are required for aeration and drainage are destroyed. Other issues include ~80% decrease in worm populations, increased runoff of water, sediment and faecal coliforms, reduction of phosphate and other nutrient uptake and increased greenhouse gases. It can also affect soil temperature and plant root penetration. An excellent illustration of compaction and soil aeration was evident on a sheep and beef farm I visited near Te Kuiti. In a 30 meter by several hundred-meter strip in a paddock upon a hill, there was amazing pasture growth. This patch had approximately 2500 pasture cover but on either side of the 30 meter strip the cover would have been less than halve. The difference was obvious. The reason for the extra pasture growth was that a trench had been dug for a water pipe and when the soil had been returned it was in a less compacted state. As another example, I advised a young dairy farmer near Putaruru to aerate his paddock with a James aerator. The soil type was volcanic silt loam. He said the difference after aerating the paddock was incredible as the pasture growth difference to the next paddock where he did not aerate was phenomenal. There are many ways you can aerate a soil. You can do it chemically by using lime or gypsum, biologically by adding compost/organic matter, encouraging earthworms (by liming), and microbes & fungi or mechanically with a tractor and equipment such as a James aerator, ground hog, Rata and numerous other brands’ including a Forbes soil conditioner. Having drains can also reduce compaction by draining soils in wet periods of the year which will reduce compaction. About 2 months ago I was introduced to Stu Forbes by a mutual friend. Stu had developed his Forbes soil conditioner/aerator over a 35-year period with a team, including Prof. John Baker. Stu reckons he has got the best piece of equipment to aerate soils with. But he is always challenged by ‘show me the data’. That’s where I come in, as I see soil aeration/soil structure to be just as important, as soil moisture (by rainfall or irrigation) and soil pH and nutrients. Stu and I have therefore commenced trials on sheep/beef and dairy farms using the Forbes soil conditioner. The trial will be carried out on many farms around New Zealand, from as far north as Northland to Wairarapa, and in Canterbury. Pasture production will be monitored with and without the use of the soil conditioner.

The leaching of nutrients in soils generally occurs between the months of April – October, and there is a lot going on below ground, more than we imagine. This article explores the effect of rate of nitrogen fertiliser on cation and anion leaching under intensively grazed dairy pasture which can have far reaching effects on the way we farm from Hamilton-based Soil Scientist Dr Gordon Rajendram (PhD). In New Zealand, there have been limited studies on the topic of leaching of anions and cations in intensive New Zealand dairy farming systems. However, it is an important topic, as it is vital to the soil health and long-term effects on New Zealand farms. Leaching is the loss of water-soluble plant nutrients from the soil, due to rain and irrigation. Plant essential nutrients exist as anions and cations. Anions are elements or molecules that in their natural state have a negative (-) charge. Cations are ones that have a positive (+) charge in their natural state. Generally, soil is negatively charged and repels negative ions (anions), which are easily leached by rainwater and irrigation drainage.  Negative ions which are leached take a positive ion with it, it is part of nature. “The leaching of anions and cations is conditional on various factors including the amounts and form of nutrients applied in fertiliser, stocking rate, rainfall & therefore drainage, soil type and extent of previous leaching,” says the Soil Scientist Dr Gordon Rajendram The increased use of nitrogen fertiliser on dairy farms for the last few decades, has led to the growing concern about the effect on nitrate leaching to groundwater. A study in the mid 1990’s by Rajendram and Stewart Ledgard and other research’s at AgResearch set out to determine the amounts of Ca, Mg, Na, K, nitrate-N, sulphate-S, Cl and inorganic P leached from intensively grazed dairy pasture at three sites (Waikato, Taranaki & Southland) over a five-year period in the absence of N. In addition, nutrient leaching was determined in dairy farmlets at the three sites receiving 0, 200 or 400 kg N/ha/year. “The quantities of cations and anions leached from the farmlets getting no nitrogen fertiliser represented a significant removal of these nutrients from the system, particularly under high drainage,” comments Gordon. Where no N was applied, approximately $240 of fertiliser was applied above ground, but $160 of nutrients was lost below the root zone in drainage. Once the N applied was increased to 400 kg N/ha/yr, the value of nutrients lost below the root zone jumped to $250/ha/year. Another negative impact was, clover N fixation decreased from 180 to 0 kg/N/year when nitrogen application rates increased from zero N applied to 400 kg N applied per hectare per year. Leaching losses for cations and anions were similar between the different non-N-fertilised farmlets even though there were differences in soil drainage characteristics, region and management practices. This study showed that high-level leaching losses of Ca, Mg, Na, nitrate-N, sulphate-S and Cl occurred from intensively grazed pasture and that heightened farming intensity, through the use of N fertiliser, increased the losses of Ca and nitrate-N. Soil Magnesium levels were decreasing on farms in the 1980’s and 90’s. This study showed the reason why this was the case.  Approximately 30 kg per hectare of magnesium was being leached every year and not replaced in fertiliser or via rainfall. “These results have significant consequences to the sustainability of these systems, the potential for an increase in the incidence of hypocalcaemia and hypomagnesaemia in animals, and the requirements for nutrient inputs in fertilisers,” advises Gordon.  The research findings were included into the Overseer nutrient model. When farmers are required to determine their N leaching index, cations and anions leached is also generated by Overseer as part of the output. Waikato based Soil Scientist Gordon Rajendram is committed to helping New Zealand farmers get the most out of their soil so that their farm can work more proficiently, be sustainable while increasing farm profitability. Gordon is one of the leading voices in soil fertility.

Waikato-based Soil Scientist Gordon Rajendram PhD is considered one of New Zealand’s experts in soil fertility. He is committed to helping New Zealand farmers get the most out of their soil so that their farm can work more proficiently, be sustainable while still increasing the farm profitability. Dr. Gordon Rajendram worked at AgResearch, Ruakura Research Centre, Hamilton.  He has developed two field calibrated soil tests (N & S) which are used for agronomic advice in NZ and his work on leaching has been included in the Overseer nutrient model. Soils will continue to change over time, that’s why regular soil testing is crucial to the continued health and success of your farm says Hamilton-based leading Soil Scientist Dr Gordon Rajendram (PhD). Soil testing will showcase the mineral imbalances that may be affecting the health of your crops or livestock. Macroporosity is a measure of the proportion of large pores in the soil that provide the air supply to roots and microbes. A 10 % decrease in pasture production for every 1% decrease in microporosity below the critical level of 10 %. It’s the best soil physical field calibrated test for New Zealand and was developed by AgResearch in the late 1990’s.   Treading damage can cost loss in pasture production. “When soil structure is damaged the infiltration, rate decreases and pores that are required for aeration and drainage are destroyed,” says Gordon. Other issues are ~80% decrease in worm populations, Increased runoff of water, sediment, faecal coliforms, phosphate and other nutrients plus Increased greenhouse gases. An ASC test (Anion Storage Capacity), previously known as P Retention, is a measure used to define the phosphorus (P) immobilisation potential of a soil. This will test the ability of the soil to hold on to phosphate and sulphur.   An ASC test must be included with every sampled area to determine its level. “This is particularly valuable information when bearing in mind the use of phosphorus and sulphur fertilisers,” adds Gordon.  Low ASC soils have minimal P binding sites. Once you have all the testing done, and have all the accurate information on what needs to go on your soil, the next step is to develop a fertiliser programme specific to each area or paddock. Fine particle or slow-release fertiliser is a great choice. Fine particle fertiliser has improved fertiliser use efficiency with lower spread rates required to get the most out of it. “Featuring a rapid uptake of needed nutrients, with fine particle fertiliser deficiencies can be rectified quickly due to the excellent foliar nutrient uptake,” adds Gordon. With efficient application the proportion of nutrients can be varied. Not only that, it also has reduced environmental impact. You may not be able to change your soil type or the climate, but you can control the amount and type of phosphorus and sulphur that are applied to vulnerable areas. If you want to discover more about the benefits of soil testing can bring to your farm, then make sure you get the best in New Zealand, the soil scientist Dr Gordon Rajendram out to your rural farm today.  With his BSc, MSc and a PhD, Gordon is one of the leading experts on laboratory and field measurement techniques for chemical, biological and physical properties. About The Soil Scientist Gordon is dedicated to helping all farmers get most out of their soil so that their farm can work more efficiently, be sustainable while improving the farm profitability. Contact Gordon: Email: rajendram@xtra.co.nz Phone: 021 466 077 Facebook: https://www.facebook.com/GordonRajendramSoilScientist Website: http://dev.gordonrajendramsoilscientist.co.nz LinkedIn: https://www.linkedin.com/company/the-soil-scientist Instagram: https://www.instagram.com/thesoilscientistnz/ Contact MediaPA: Phone: 0274 587 724 Email: phillip@mediapa.co.nz Website: www.mediapa.co.nz Facebook: www.facebook.com/MediaPA YouTube: www.youtube.com/user/TheMediaPA

Waikato-based Soil Scientist Gordon Rajendram PhD is considered one of New Zealand’s experts in soil fertility. He is committed to helping New Zealand farmers get the most out of their soil so that their farm can work more proficiently, be sustainable while still increasing the farm profitability. Dr Gordon Rajendram worked at AgResearch, Ruakura Research Centre, Hamilton.  He has developed two field calibrated soil tests (N & S) which are used for agronomic advice in NZ and his work on leaching has been included in the Overseer nutrient model. In this second article I further explore the above question, which is better liquid, suspension, or granular fertiliser? This year the farming industry has seen unprecedented price rises for two of the major nutrients required for pasture and crop growth, phosphate, and nitrogen. The price of phosphate has increased from $2.70 to $4.27 for a kilo of the nutrient, and likewise nitrogen has increased from $1.15 to $2.89. Other nutrients such as sulphur ($0.60 to $0.90 per kilo of S), potassium and trace elements have also increased appreciably.  Due to the increase in fertiliser costs farmers are faced with keeping pasture or crop production at similar or higher levels. They will look to solutions, methodology or technologies which will be more nutrient efficient. i.e., get more pasture response with less nutrient use.    In this article I will concentrate more on my experiences with technologies/methodology which may achieve the above goal.  In the 22 years I worked at MAF and its predecessor AgResearch, Ruakura Research Centre in Hamilton, the products we researched were generally all granular based.  We did Government funded research or did projects for companies who could afford us and there weren’t many of these companies in New Zealand.  In 2016 I gave a talk in the Far North, near Taipa, to a group of farmers. At question time one of the farmers sitting in the front asked me, what I thought of fine particle application (FPA)? FPA is a trade name, but I call it suspension technology. I told him I knew nothing about it.  After the talk I approached him and asked if I could visit his farm to see what he meant as I wanted to know more.  The farmer was Arthur Beazley who runs red devon cattle on a 120ha farm just north of Kaeo. I visited him the next day and he showed me his tow n fert machine. Therefore, this started me on my journey of learning about suspension technology and foliar/liquid fertilisers.  Suspension technology uses finely ground nutrients. There are companies in New Zealand who have specialised in this technology for more than 30 years. Companies such as Uptake,  based in Taupo owned by John Davis, Mainfert, based in Timaru owned by Marty Kimble and Dean White, and there are others as well who specialise in this technology in New Zealand. Suspension technology requires specialised ground-based equipment such as the tow n fert machine (Metalform in Dannevirke) or Cylone mixers (Chaos farming in Waihi). These machines require robust pumps and large nozzles. The ground up nutrients are very abrasive and therefore require specialised equipment. There are helicopter operators and SuperAir who have the equipment to apply it from the air.  Therefore 16 elements (or more), fine lime, including growth promotors, inhibitors, hard round seeds like clover, fungicides or insecticides can be applied together.  Suspensions are in between liquid and granular and are ground up nutrients, and rates of application of a nutrient per hectare can be as high as granular if required. So, how can these technologies be more efficient and cost-effective? These questions will be answered in the following series of articles.

Waikato-based Soil Scientist Gordon Rajendram PhD is considered one of New Zealand’s experts in soil fertility. He is committed to helping New Zealand farmers get the most out of their soil so that their farm can work more proficiently and be sustainable while still increasing farm profitability. Dr Gordon Rajendram formerly worked at AgResearch, Ruakura Research Centre, Hamilton.  He has developed two fields of calibrated soil tests (N & S) which are used for agronomic advice in New Zealand and his industry-leading work on leaching has been included in the Overseer nutrient model. Due to the increase in fertiliser costs, farmers are faced with keeping pasture or crop production at similar or higher levels with similar fertiliser budgets to previously.  Can we, therefore, keep the same fertiliser spend as previously and grow just as much nutritious pasture or more pasture without compromising production or have any detrimental effects to the environment? This will be the first of a series of articles in which I explore the above question.  Firstly the main factors which drive pasture production are soil moisture, temperature, approximately 13 soil nutrients, soil acidity, microbiology and finally but not least soil air space (soil porosity).   The mantra I constantly use “if you don’t test, you cannot manage”.  It is very important to test soil, pasture, clover only and individual crops to see if any of the above factors are limiting growth.  All these parameters have optimum limits for pasture or crop growth and will be limited if these are not in the target areas. For the 13 nutrients,  once the optimum levels are reached, only maintenance rates are required and therefore application rates can be low depending on the nutrient, soil type and climatic factors (leaching and runoff).  Monitoring of pasture growth rates is also a very important testing tool. In the last five years, I have had experiences with technologies that I believe can be part of achieving the above. In this article, I will concentrate more on my experiences with these technologies whereas in the next articles I will dwell more on the science. The majority of fertilisers in New Zealand are applied in a solid granulated form for ease of spreading and generally are a in a highly soluble form i.e., becomes quickly available to pasture or crops. There are benefits to this but once optimum nutrient levels are achieved are there better technologies/modes of application available?  Suspension technology, or otherwise known as fine particle application or foliar/liquid,  may be more efficient and cost effective.  Soluble liquid fertilisers can be applied with normal spray equipment but with suspensions require specialised equipment with robust pumps and larger nozzles.   With liquids and suspensions up to 16 elements (13 for pasture growth plus three more for animal health) can be applied in one application, including growth promotors, inhibitors and fungicides or insecticides.  Suspensions are in between liquid and granular and are ground up fertilisers/nutrients and rate of application can be as high as granular if required. So, how can these technologies be more efficient and cost-effective? These questions will be answered in following articles.

Slow-release products or “suspension fertiliser technology” is the future for pasture growth in New Zealand, according to soil scientist Dr Gordon Rajendram. While fencing or planting trees along waterways to reduce phosphate loss is an expensive exercise, Dr Rajendram says more affordable methods exist. “The cheapest way to reduce P [phosphate] is to change your product from a highly soluble one to a less soluble one,” he says in disclosing five factors that drive pasture growth. Five years ago, at a soil seminar, Dr Rajendram says an elderly farmer had revealed to him the suspension method’s ability to apply 16 nutrients in one application. This technology ticks many boxes not only for pasture growth, but environmentally. The Waikato-based independent fertiliser consultant outlines five factors that drive pasture growth: 1/. Soil temperature at 10cm is a good indicator. A drop down to 5 – 6 degrees C stunts growth. 2/. Falling below 25% of soil moisture content slows growth. 3/. The pH (acidity) level and 13 key elements are required for plant growth. 4/. Soil that isn’t porous robs roots and microbes of air. 5/. Soil biology When testing the soil, he says it’s imperative to avoid dung and urine hotspot patches that can skew readings because of high nutrient levels. Animals excrete 66% of what they eat. “If you can’t test, then you can’t manage.” In a pasture of rye grass and clover, the former contributing to 19% of the protein in pasture and the latter 34%, as clover is a nitrogen fixer. “So, that means the more clover you grow, the more [nitrogen] you’re fixing for free,” he explains. Dr Rajendram says clover’s digestible quality yields more energy, compared with grasses. With clovers and most grasses ‘allergic’ to soil acidity, farmers need to monitor soil pH content to acquire 6.2- 6.5 soil pH levels.  These soil pH levels are based on many factors with Irish farmers also recommended these ideal pH levels. Farmers must strike an “optimum” level to avoid low productivity but also not “overcook” to incur leaching costs. “In Waikato, you become a bit of a slave to phosphate but, in Canterbury, you have more potential to lose it,” Dr Rajendram reveals. “It’s hard-earned money you don’t want to lose.” April-to-October rain and drainage dictate the extent of leaching. Any nitrogen that plants fail to absorb drops incrementally by approximately a metre each year until it reaches aquifers and streams. Anions (negative ions), such as nitrate and sulphate, attract and hold cations (positive ions), such as calcium and magnesium, in aiding leaching. However, minute amounts of phosphate via runoff or leaching aren’t an economic issue, but an environmental one. Contact Gordon: Email: rajendram@xtra.co.nz Phone: 021 466 077 Facebook: https://www.facebook.com/GordonRajendramSoilScientist Contact MediaPA Phone: 0274 587 724 Email: phillip@mediapa.co.nz Website: www.mediapa.co.nz Facebook: www.facebook.com/MediaPA