Considerations For An Effective Soil Amendment Strategy

Wednesday 29 November 2017


Lime, dolomite and gypsum are the cornerstones of soil conditioning, a practice with immense benefits in all agriculture industries. In collaboration with leading researchers, and in response to grower feedback, Nutrifert Australia now deliver a unique granular range of the world’s highest quality lime, dolomite and gypsum. The stable granular form of these inputs offers a degree of user-friendliness not seen before in the market, with potential to include them into standard fertilizer blends for a one-shot application. The unique high quality also promises effectiveness at much lower rates than standard bulk applications of their equivalent.

Let’s take a closer look at the considerations for an effective soil amendment strategy, and why Nutrifert’s products are the platinum choice in this market.  


The importance of pH in soil management

pH is one of the first steps in assessing the health of a soil. Changes in soil pH may be advantages or detrimental depending on what you start with, which is why it is vital to take a soil test and consult with your local Nutrifert supplier to determine the most appropriate pH management strategy for your operation. Generally, you want to maintain an equilibrium of between 6.2 and 6.5 for optimal mineral availability. Anything below 5.5 or above 7 will create issues.


pH management

In general, the following rules should be followed for soil pH management

  • Do not add lime to a soil with a pH above 7, as there are no acids present for the carbonates to react.
    1. In this situation, gypsum may be a more appropriate strategy to maintain a healthy soil structure.
  • Alkalinity, and excesses of soil sodium/magnesium can be managed with appropriate applications of gypsum.

What causes the pH to drop, or the soil to become acidic?

Cumulative applications of some nitrogen based fertilisers can wreak havoc on your soil health by burning out the carbon and acidifying the soil. Urea, DAP, MAP, SOA etc. all have an acidifying effect on the soil, and granular lime incorporated with these types of inputs can help counteract this. At the same time, quality lime provides calcium nutrition, an element vital for root development and overall plant health.

This counteractive strategy is especially important in soils with an already acidic soil pH, where the availability of phosphorus is severely diminished due to the release of aluminium and iron.

Without countering this acidiyfyig trend, consecutive applications of a nitrogen/phosphorus fertiliser will give you a poorer and poorer response each season, and end up wasting money. At the same time, you are damaging your number one asset as a grower, the soil.

And it’s not just mineral availability that’s the issue in acidic soils; low pH can also be detrimental to plant root health, and if the roots are harmed during critical establishment phases (when you apply starter fertilizer for example) then it will severely diminish your return of investment.

Reference: Mineral Nutrition and Plant Disease (2007 Lawrence E. Datnoff (Author, Editor),‎ Wade H. Elmer (Editor),‎ Don M. Huber (Editor)

But won’t lime lock up my phosphorus inputs?

In an alklaine soil (pH above 7) the highly reactive phosphorus, and calcium in its ionic form, can form insoluble crystalline calcium phosphates. In acidic conditions (under 5.5 for example) reactive forms of P will lock up with aluminum to form insoluble compounds. No good agronomist will ever recommend applying lime with a phosphorus input when the pH is over 7. So as long as your pH remains below the 6.5 threshold, lime will not lock up your phosphorus inputs. In fact, it will enhance it in these situations. Studies in America have shown incidences were straight soil applied lime has increased phosphorus levels in pasture leaf tissue, more so than soil applied DAP!

How much lime do I need, and how do I apply it?

You have to ask yourself what you are actually trying to achieve. If the base pH of the surrounding soil is already below 5.5 then it would be advisable to manage this with a broadcast lime application, in conjunction with applying the appropriate amount of lime with any inorganic fertiliser blend to counteract acidifying effects. Traditionally, bulk lime is the standard choice for broadcast applications, however research shows this is not actually the best choice. Let’s take a closer look at the importance of lime quality.


Lime quality

There are essentially two measures of lime quality:

  • Neutralising Value
    1. A measure of purity, rated as a percentage. Any lime that’s 95% and above is as an average to good quality. 99% and above (Ozcal) is very high quality.


  • Particle size and release pattern.
    1. Essentially by decreasing lime particle size you are increasing the exposed surface area for reaction with soil acids, and therefore increasing the rate the soil acids will break down the lime. The carbonate portion of the lime is released, and this is what neutrliases acidic soil pH.
    2. Lime solubility decreases as pH increases. If the particle size of the lime material varies considerably, as it does for most bulk lime, the smaller fines will neutralize the soil surrounding the larger particle sizes, and the coarser material will not react. Essentially a large portion of bulk lime applications may not actually do anything, and a more precision pH management approach utilizing granular ultrafine lime can be a lot more cost effective.



The following research trial is one of the most referenced investigations into lime particle size, demonstrating particle size effects on rates of pH change and calcium ion release:

B.J. Scott, M.K. Conveyers, R. Fisher and W. Lil (1992). Particle Size Determines the Efficiency of Calcitic Limestone in Amending Acidic Soil. Australian Journal of Agricultural Research, Vol. 43


“The six particle size fractions were derived from a 98% pure calcitic limestone from the Marulan Quarry in New South Wales. At a given rate of application, the finer the particle size, the greater the increase in pH. This trend applies even at the 10 t/ha application rate where we expected the fineness would be of less importance.”

For reference:

  • Ag Lime: Less than 500 micron (0.5 mm)
  • Super Fine Lime: Less than 100 micron (0.1 mm)
  • Ultra Fine Lime: Less than 40 microns (0.04 mm)


Nutrifert’s Ozcal and Ozcalmag granular inputs are 95% less than 45 microns (0.045 mm), with an average of 20 microns, and a neutralizing value of 99%, making them highly effective for any pH management strategy. Yes, you are applying a product with an equivalent chemical analysis however you must consider the fact the average particle size falls within an even fine sized band, meaning what you put on the soil is utilized. This is why we recommend applying at a rate 10-20% of your normal bulk applications. The same level of quality is also included in the Ozgyp, where the micro fine particle size offers superior release and effectiveness.

Nutrifert are loyal to addressing the needs of Australia’s farmers, and will continue to research and develop cost effective products as the industry progresses. Get in contact with your local supplier to see how Nutrifert can benefit you.