NAMPO 2019

www.nampo.co.za

Graan|Grain

he entire agricultural community, from small scale and com-

mercial producers, through agent networks, commercial

and agricultural economists to as widespread as university

researchers and experts, is pondering on the effect of lime-

stone mineralogy, limestone fineness and the granulation of

fine limestones on the efficiency of soil neutralisation.

Producers employing conservation agriculture specifically,

report problems in liming deeper soil layers as their soils are not

tilled. Granulated fine limestones may offer a solution to the prob-

lem as the lime granules can be placed with the seed, deeper

in the soil during planting. Fine limestones might also be able to

permeate the soil more effectively than regular class A crushed

limestone sources due to higher solubility, whereas granulation

offers the additional advantage of reducing or completely elimi-

nating the loss of valuable fines due to windy conditions during

spreading.

Industry and academia – partnering

for purposeful, practical research

SA Lime & Gypsum is at the forefront of current research to develop a

quick and reliable comparative laboratory tool to approximate the

neutralisation kinetics

and time-constrained

capacity of standard

limestones versus mi-

cronised and/or granu-

lated materials.

In collaboration

with various research

teams at the Stellen

bosch University, we

are also looking at

comparing the soil

permeation of these

limestone

sources

and their physical

forms in soils with

widely different tex-

tures as well as the

placement effect of

the various materials

on plant root and

shoot growth as well

as calcium (Ca) up-

take. Since wind loss-

es are becoming a crucial dynamic in an environment where

fast changing climate factors are affecting the timing of fertili-

sation and planting, we have included various wind loss simula-

tion studies in the research design.

The research, which was initiated in 2017 at the company’s

central laboratory facility in Gauteng, consists of four different

assessments:

A laboratory study of the kinetics of weak acid neutralisation

combined with a time-based lime incubation neutralisation

study;

a lime penetration study in various soils;

a small pot-trial to assess plant response; and

an extensive field trial matrix incorporating the effects of

no-till versus different tilling methods on soil response, using

normal versus micronised limestone sources.

This work is conducted by a team consisting of the company’s inter-

nal research scientists and analytical chemists together with various

soil scientists, agronomists and master’s degree students from the

Stellenbosch University.

Using reaction kinetics to compare

time-based neutralisation efficiency

SA Lime & Gypsum enjoys the enormous benefit of a purposeful

laboratory at our processing facility and distribution depot in

Olifantsfontein, Gauteng. Here, a designated experimental setup,

designed and built in-house by professional scientists, is used to ap-

proximate the reaction kinetics of neutralisation of limestone in a

weak acidic environment.

The experimental design utilises the principles of forced

first-order reaction kinetics at stoichiometric excess limestone

addition rates.

Graph 1

illustrates this principle and shows

the difference be-

tween a class A

limestone and a mi-

cronised

product.

The same setup can

also be used to de-

termine the amount

of limestone needed

to neutralise a fixed

amount of acid, from

which the experi

mental usage factor

can be determined.

Initial results are

very promising and

pending the out-

comes from the field

trials and a potential

correlation between

that and these labo-

ratory results, we are

determined to pro-

vide market defining

information on the

exciting prospects of using micronised limestone – not only as

an effective way of providing essential macro-elements in the

furrow but also as a highly effective deep-penetrating soil im-

prover. SA Lime & Gypsum and its collaborators intend to make

this information available to the broader community through

various channels in the public domain to serve the agricultural

community of South Africa for the benefit of all.

Dr Jaco Erasmus,

SA Lime & Gypsum

, Dr Pieter Swanepoel

and

Dr Ailsa Hardie,

Stellenbosch University

From lab to field

– research for the greater good

Graph 1: The difference between a class A limestone and a micronised product.

2019

Product

information