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Cultivar selection is the most important decision

October 2015

Selecting the right soybean cultivars to plant is one of the most important decisions a farmer has to make.

It is not unusual for unmodified cultivars to deliver yields of up to 20% lower than the top producer in national cultivar trials (Table 1). With low profit margins being common in crop cultivation, major losses can be incurred if the wrong cultivar is selected. If it is taken into account that the best cultivar yields up to 580 kg/ha more at R4 500 per ton, the losses can amount to R2 610/ha. That is why the time spent on gathering data to make better-informed decisions is so important and therefore not wasted.

Cultivar selection is the most important decision

Cultivars available to you

There are a large number of soybean cultivars on the market and available to the farmer. The improvement in yield over the past 34 years with better cultivars amounts to 1,2% per annum (A). Sufficient information is available to select the right package. The competition between seed companies is intense, and each one wants to sell the best to the producer.
Each company very carefully selects the best cultivars available to them. They use the most modern production and breeding techniques to deliver the best quality seed to the farmer.

The national cultivar trials carried out by the ARC are the best place to start if a cultivar has to be selected. If a cultivar does not appear in the trials, it should rather be avoided.

Production areas

The South African production areas are divided into three primary areas, namely cool, moderate and warm.

Unlike the rest of the world, where soybean production areas are determined by the relative distance from the equator, soybean production areas in South Africa are determined by the area’s altitude. The cooler production areas are located in the eastern, higher-lying areas that are characterised by a shorter production season, with moderate summer days and relatively higher rainfall.

The moderate production area generally has a longer production season, with warmer days and average rainfall.

The warm production areas have a long growing season, with warm days and little rainfall, rainfall, and soybeans are mainly cultivated under irrigation here.

In the first place, every farmer has to know in which one of the three production areas his land falls, and also what the production potential of the soil is. The wheat can be separated from the chaff quickly here.

Look at the research

Seed companies conduct a lot of research so that the right cultivar for each area can be identified and the data can be obtained to assist with the decision-making process. It is also essential to add information from local comparative strip trials conducted by study groups and individual farmers.

The dangerous option is to listen only to a neighbour, because this season will not be exactly the same as the previous one. If all the information is combined, three to five cultivars that can be used will quickly emerge.

Growth classes

The next step is to make a selection between the different growth classes. It is good practice not to place all your eggs in one basket. In order to distribute risk, a selection of different cultivars should preferably be planted.

If the cultivars are arranged into different growth classes, the best from each growth class can immediately be selected. Thus the risk can be optimally managed.

In years where the rain stays away at the end of February and in March, the growth classes 4,5 to 5,5 will perform much better than the growth classes 5,5 to 7,5. The reverse is true where good rains fall in the second half of the season. It has been found that, over the long term, growth classes 5 and 6 produce the most stable yield (Table 2), and the biggest part of the selection should come from these growth classes.

Cultivar selection is the most important decision

Sources for tables

A.S. de Beer and M.A. Prinsloo. 2013. The national soybean cultivar trials in South Africa – 34 years experiences and progress.
AS de Beer and N de Klerk. 2014 Sojaboon kultivaraanbevelings 2014 - 2015.

Article submitted by Nico Barnard: Research Agronomist, Pannar Seed.
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Publication: October 2015

Section: Pula/Imvula