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18 February 2019 | Story Leonie Bolleurs | Photo HO de Waal
Ground spiny Cactus pear
Shredded, sun-dried, and coarsely ground spiny cactus pear (Opuntia ficus-indica and O. engelmannii), ready to be included in balanced diets for ruminant livestock (cattle, sheep, goats) and wild antelopes.

Prof HO de Waal, researcher in the Department of Animal, Wildlife and Grassland Sciences at the University of the Free State (UFS), has developed a standard procedure for the processing of spiny cactus pear (Opuntia spp.) into livestock fodder. This will ultimately assist in the management of massive infestations of spiny cactus pear and help to convert underutilised farmland back to natural grazing land.

In addition to applying biological control agents, mechanical control is used to harvest alien spiny cactus pear, and the large volume of material is processed as livestock feed.

 

Introduced to South Africa

 

Three hundred years ago, seafarers visiting the Cape of Good Hope introduced the well-known invading alien spiny cactus pear to South Africa. These were later transported inland and by the 1950s about one million ha of South Africa had been invaded by the alien cacti.

Some regions in the Eastern Cape have been taken over by dense, impenetrable thickets of these cacti. Invasive alien plants (IAPs) such as cacti pose a direct threat to, among others, South Africa’s water security and productive use of land.

A range of methods is used to control IAPs, including mechanical, chemical, biological, and integrated control methods.

A control programme must include the three phases of initial control to drastically reduce the existing population; follow-up control of seedlings, root suckers, and coppice growth; and maintenance control on an annual basis to sustain low alien plant numbers.

 

Processing spiny cactus pears

 

According to Prof De Waal, the harvesting and processing of the spiny cactus pear is fairly simple. Although it requires a good measure of physical strength, perseverance, and the necessary protective clothing, the cacti can be processed by harvesting the plants; shredding the cladodes through a cladode cutter; then drying them in the sun, and lastly grinding it in a hammer mill. “The long spines are degraded mechanically by grinding the sun-dried cladode strips in a hammer mill before including it in balanced livestock diets,” said Prof De Waal.

Infestations will be opened, reclaimed, rehabilitated and the natural pastures (veld) allowed to revert back to grazing for livestock.

The National Resource Management Programme (NRM)P) will be approached for official support in clearing and rehabilitating massive areas of infestation by alien spiny cactus pear in the Eastern Cape. Such financial support will be an investment in reducing the infestation by invaders and the rehabilitation and sustainable use of natural resources in South Africa.

News Archive

Sunflowers are satellite dishes for sunshine, or are they?
2016-07-20

Eighty-six percent of South Africa’s
sunflowers are produced in the
Free State and North West provinces.

Helen Mirren, the English actress, said “the sunflower is like a satellite dish for sunshine”. However, researchers at the University of the Free State (UFS) have found that too much of this sunshine could have a negative effect on the growth of sunflowers, which are a major source of oil in South Africa.

According to Dr Gert Ceronio from the Department of Soil, Crop, and Climate Sciences at the UFS, extremely high soil temperatures play a definite role in the sprouting of sunflower seedlings. Together with Lize Henning, professional officer in the department, and Dr André Nel from the Agricultural Research Council, he is doing research on biotic and abiotic factors that could have an impact on sunflowers.

Description: Sonneblom 2 Tags: Sonneblom 2

Various degrees of deformity (bad-left
to none-right) in seedlings of the same
cultivar at very high soil temperatures.
Photo: Dr Gert Ceronio

Impact of high temperatures on sunflower production

The Free State and North West provinces, which produce 86% of South Africa’s sunflowers, are afflicted especially by high summer temperatures that lead to extremely high soil temperatures.

Dr Ceronio says: “Although sunflower seeds are able to germinate at temperatures from as low as 4°C to as high as 41°C, soil temperatures of 35°C and higher could have a negative effect on the vegetative faculty of sunflower seedlings, and could have an adverse effect on the percentage of sunflowers that germinate. From the end of November until mid-January, this is a common phenomenon in the sandy soil of the Free State and North West provinces. Soil temperatures can easily exceed the critical temperature of 43°C, which can lead to poor germination and even the replanting of sunflowers.”

Since temperature have a huge impact not only on the germination of sunflower seeds, but also on the vegetative faculty and sprouting of sunflower seedlings, Dr Ceronio suggests that sunflowers should be planted in soil with soil temperatures of 22 to 30°C. Planting is usually done in October and early November. Unfortunately, this is not always possible, as soil moisture is not optimal for growth. Farmers are then compelled to plant sunflowers later.

Impact of herbicides on sunflower growth

“High soil temperatures, combined with the herbicide sensitivity of some cultivars, could lead to the poor development of seedlings," says Dr Ceronio.

The use of herbicides, such as ALACHLOR, for the control of weeds in sunflowers is common practice in sunflower production. It has already been determined that ALACHLOR could still have a damaging effect on the seedlings of some cultivars during germination and sprouting, even at recommended application dosages.

“The purpose of the continued research is to establish the sensitivity of sunflower cultivars to ALACHLOR when exposed to high soil temperatures,” says Dr Ceronio.

 

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