Agricultural Lime. Last week we looked at the importance of liming and the returns it generates by maximising the efficiency with which nutrients can be used by the crop and improving the root environment for the plant.
This week I want to look at the options for correcting pH with different types of Agricultural Lime materials. For most situations, calcitic lime from calcium carbonate is the appropriate liming product. When limes are sold it is important to understand the Neutralising Value and the Reactivity.
Neutralising Value – how effective is the material compared to pure calcium oxide, expressed as a percentage.
Reactivity – how quickly does the lime react with hydrochloric acid – a good indication of how quickly is acts in the soil.
It is advisable to always test your lime – which is a very important step to understand what Agricultural lime you are applying any how effective it is; and from this you can calculate how much lime you need to apply.
Agricultural Lime Tip#1: Check the material you are dealing with
The analysis will also tell you the fineness of the material. As we looked at last week this is crucial. Lime may look fine to the naked eye but if it does not have the surface area for the reaction to take place in the soil, it will not effectively alter the pH, as the work below from Cornell State University demonstrates.
A good quality Agricultural Lime will have around 40% plus passing through a 150 micron sieve. If the Lime that you have purchased, or have access to is not of suitable fineness, you have two options…
- Apply proportionately more lime to increase the amount of very fine particles in the soil.
- Buy a lime crusher to improve the fineness of the material.
The second point is not as crazy as it sounds. Let’s look at the numbers …
Over 100 hectares this increases the cost by over 1.2m Ksh or $12,000 and that’s before the extra time and cost of spreading double the agricultural lime material.
For larger farms it does not take long before a jaw crusher or roller mill becomes feasible to reduce the amount of product required and the cost. The lime can even be purchased at a lower grade and lower price, so that you do the majority of the crushing on-farm and have a known quality of product at the end.
Agricultural Lime Tip #2: Use Fast-Acting Granular Lime
An alternative to bulky liming is using lower rates of fast-acting, ultra fine granular lime products on a little and often basis. Products such as G-Lime, Physiolith and Calciprill are all ground to below 125 microns, before granulation to prills of around 3-6mm.
A major benefit of these products is that they can be mixed in with seedbed fertilizer at planting or broadcast with a conventional fertilizer spreader so offer a quick solution when you have left it late to be putting conventional lime on that will not have time to work and benefit the immediate crop.
The high reactivity and the calcium supply to legumes on many of our soils is very useful, but ultimately these products do not apply sufficient material to notably raise the pH.
My costings below suggest that while these may be useful on short term rented land, the better long term investment by far is proper lime.
— David Jones (@Cropnuts_agron) March 5, 2017
My Experiences of Low Rate Granular Limes
- In no-till situations we experimented in the UK applying ultra fine granulated G-lime at 800 kg/ha vs 5 t/ha of conventional lime. 10 months later, the top 5cm was a slightly higher pH but the next 5-15cm was unchanged. Conventional lime raised the pH of both significantly.
- I undertook 3 trials with ultra fine liquid lime applied in furrow to wheat and two pea crops in 2017. No difference in root mass or nodulation was seen in any trial. In the interest of objectivity I should add that these trials were not taken to yield.
- Some granular lime pellets do not appear to breakdown and disperse in the soil as you might imagine, which one can only imagine severely limits their effectiveness.
- I have heard reports and seen in our own pot trials where roots mass HAS been visually improved with HIGH rates of granular lime.
David Jones is the Broad Acre Specialist at Crop Nutrition Laboratory Services Ltd. (CROPNUTS). David has a keen interest in soils and no till farming systems where he has undertaken work looking into weed levels and changes in soil structure, and has extensive experience in field trials and in the development of precision farming techniques. In his spare time he enjoys playing rugby.