February 2025
WESSEL VAN WYK, SOYBEAN SPECIALIST AND CONTRACTOR, PROTEIN RESEARCH FOUNDATION | ![]() |
A FARMER SHOULD MAKE THE DECISION TO PLANT SOYBEANS AT LEAST TWO YEARS BEFORE THE FIRST PRODUCTION SEASON (ACTUAL PLANTING) AS THERE ARE A NUMBER OF FACTORS THAT MUST BE CONSIDERED AND ADDRESSED BEFORE PRODUCTION BEGINS.
THE RIGHT LAND AND SOIL
All compacted layers should be broken up (ripped). It is also important to use lands that are not rocky and/or very uneven. Soybeans are harvested at a low level (30 mm to 60 mm), and the harvester blade can be damaged if lands are uneven and/or rocky. Lands that are prone to waterlogging and yellow nut sedge (uintjies) should also be avoided.
The most important factor is to obtain soil samples of the earmarked areas, have these samples analysed and do the necessary soil corrections that are recommended from the samples. The pH and lime requirements are particularly important, as the lime application should be done on the crop planted before soybeans. If large corrections of phosphorus (P) and potassium (K) are required, a large part of it can also be done on the preceding crop.
KNOW THE FACTS
Herbicides: An important factor to consider is the possible transmission of herbicides from one season (crop) to another season (crop). For instance, herbicides that are used in maize and wheat production can generally not be used on soybeans. There are also waiting periods before soybeans can be planted in the same soil where certain herbicides were used previously. It is advisable to withdraw herbicides that have a waiting period of ten to twelve months at least two years prior to planting soybeans in the same soil.
Harvesting: When a farmer makes use of contract harvesting, he/she should ensure that the contract makes provision for a set harvest date. The number of days between planting and harvesting varies greatly between seed cultivars. It is therefore important to obtain this information from seed companies.
Alfred Gondo, the 2024 Grain SA Potential Commercial Farmer of the Year, in his soybean field.
A healthy soybean crop. Photo: Martin Budgen.
CHOOSING SUITABLE CULTIVARS
Currently more than 40 different soybean cultivars are sold by various seed companies. It is important that seed is ordered before the season starts (as early as May), to ensure that farmers get the specific cultivar that they want.
Maturity groups: All cultivars can be categorised in maturity groups, which indicate the number of days that it takes from the date of planting to reach maturity and be ready for harvesting. A maturity group of 000 is planted in cooler areas, while a maturity group of 10 is planted in warm areas.
Maturity groups are furthermore divided in tenths within groups, for example 4,4 or 6,2. In South Africa, groups 4, 5 and 6 are most often planted and sometimes group 7. Groups 4 and 5 are planted in the cooler areas, groups 5 and 6 in the moderate climate areas, and groups 6 and 7 in the warm areas.
Plant more than one maturity group to mitigate the risks of drought, hail and diseases. It also prolongs the harvesting period.
Growth pattern: Certain soybean cultivars have a specific growth pattern. This means that it starts to bloom and finishes blooming within four to six weeks, and it ends on the main stem with a raceme of pods.
The other type of growth pattern is non-specific. It is very sensitive to daylight and blooming will only start when the night-time is a certain length. If this type of soybeans experiences drought conditions, it will stop growing and start producing pods. However, when there is moisture again, it will continue to grow and bloom until it reaches a certain number of days after planting.
Seed mass and structure: A bushy structure has bigger potential because of more side stems. Also consider resistance to shattering late in the season and plant height – plants with a height of 76 cm to 80 cm are big enough and will be less prone to fall over than taller plants.
Publication: February 2025
Section: Pula/Imvula