Lime: Is finer always better?


 Pete Orrell    15 May 2019 : 17:30
 None    Back Paddock News

LimeFine.jpg

In a single word - NO!

When talking about liming materials, quality in terms of effectiveness is defined by two parameters, the first being purity referred to as Neutralising Value (NV) and the second being proportion of the product in defined particle size ranges. The greater the proportion of product in the fine particle ranges the faster the product works. The combination of these two parameters is generally referred to as the effective neutralising value (ENV).

The combination of purity and application rate provides the potential amount of power in the applied product to reduce soil acidity in total and the particle size distribution (fineness) regulates the speed at which the acidity is reduced.

To some degree the two parameters are interchangeable, but there are limits!

Don’t be fooled by a sales pitch that claims a 5 x reduction in rate of liming amendment required because the product is twice or three times as fine. The product might increase the soil pH of a proportion of the application zone quickly, but the depth and duration of the pH increase may be limited by the reduction application rate.

Essential guidelines for selecting liming products

  • Access most recent details of lime quality lab test particular ENV from the product supplier or obtain sample and submit to a qualified laboratory for testing (ensuring sampling pit or pile process is appropriate and request details of screen sizes used in assessing lime be provided with results)
  • Determine the ENV assumed in the liming product rate recommendation. Be aware that differences in the number of screen size factions and sizing of screens may be defence between laboratories. The ENV of a single product may differ based on the differences in calculation better those using WA, VIC or NSW based equations for ENV.
  • Adjust the liming rate for any difference in assumed and actual ENV
  • When comparing costing do so on a $ per tonne spread on the ground as products with a higher ENV will generally reduce the per hectare cost of freight and spreading.
  • Consider the finer the lime the more wind will affect spread patterns and potential loss to non- target areas.

Opterra LimeMate is a simple web based calculator that contains a liming product ENV calculator, liming product cost comparator and liming rate calculator that requires only a couple of simple soil and amendment product measurements to run scenarios.

Read the full Discussion Paper here








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