LIMING and SOIL AMELIORATION – Options for Precision Farming the Time Poor.
The wheels turn very slowly at times in our beloved country and it is easy to get behind with early preparations like liming. It takes a while for lime to breakdown it brings its benefits to the soil slowly.
One way around this is to use Micronized Lime. “Micronized” means finely milled into small particles measured in microns. One micron is one thousandth of a millimetre, so pretty small.
Normal agricultural lime has a much larger particle size and these particles take months to break down. One expects to get the benefits of lime to spread over several years. Micronized particles have a high surface area for their size, so they break down and react much quicker. Such ultra-fine particles would normally be taken by the wind and not settle on the soil where they are needed, so the particles are made into granules as part of the manufacturing process. The granules dissolve easily once they reach the soil to release the micronized particles. The particles themselves breakdown as quickly as 2 – 3 weeks in some conditions, according to the supplier.
Micronized products are used at lower rates. The actual rate per hectare would be arrived at by soil analysis. As a rule of thumb, 100 kg of MicroCal would be equivalent to 1 tonne of normal calcitic lime. The product is of course more expensive than normal lime (about USD 580 / tonne compared to about USD 80 / tonne). The lower rate and quicker availability offset the higher cost of the imported product. MicroCal appears cheaper in per hectare terms (a grower using 1 tonne calcitic lime per ha, costing USD 80 / ha, would use 100 kg MicroCal costing USD 58 / ha) however it must be remembered that the benefits of normal lime in the soil extend beyond one year. This leads to another difference with micronized lime: it needs to be applied every year, as it is assumed by end of season, most of the micronized lime has reacted and done its job.
There are 3 micronized products available from Damara:
1) MicroCal (mostly calcium carbonate or calcitic lime)
2) MicroDol (equivalent to dolomitic lime, contains magnesium)
3) MicroGyp (equivalent to gypsum, calcium sulphate).
The MicroGyp is also used at a lower rate than normal gypsum: 90 kg / ha is equivalent to 500 kg / ha of normal gypsum.
Incidentally, there is a new local source of normal agricultural gypsum: Lafarge Holcim have now started to sell it.
Damara Bio-Agri recently hosted farmers at Summer Cropping Roadshows in Banket, Chinhoyi and Harare to discuss the above products. The response was positive and as one farmer observed “the long-term is not always on the agenda for JVs, where you can be here today, gone tomorrow” so the benefits of using a type of lime that gives all its benefits in one season was appreciated.
Further information: Damara Bio-Agri can be contacted on office cell +263 772 666 690 or [email protected] or landline +263 8677005277.