PhD candidate’s quest to promote food security

The Department of Soil Science and the Department of Agronomy in the Faculty of AgriSciences at Stellenbosch University (SU) has embarked on a long-term field study to determine the effects of biochar on agricultural practises.

Ms Makhosazana Sika. (Photo: STEPHANIE NIEUWOUDT)

At the centre of this project is Ms Makhosazana Sika, a PhD candidate who is trying to trace what happens to the microscopic amounts of nitrogen from fertilizer that “becomes unavailable” when biochar is added to soil.

During her studies for her earlier master’s degree, Sika found that biochar could retain large amounts of nitrogen, and which helps to retain other nutrients in the soil. This means that there is a potential cost saving for farmers who would have to buy less fertiliser if they use biochar.

“However, I also found that small amounts of inorganic nitrogen became unavailable. I am trying to trace through molecular studies the exact mechanisms involved,” says Sika, who recently spent a month in America working at a project of the Global Agriculture & Food Security Program where she reviewed proposals from farming communities asking for financial help. This reinforced her belief that agriculture is the way forward in addressing the food security issues in the world.

Her research encompasses using six treatments: a control group where sandy loam soil is used; traditional organic treatment; scientific organic treatment; chemical treatments; biochar treatments and biological treatments.

During the first season she planted cauliflower and she aims to plant a number of other crops in seasons to come.

“I am also looking at the vertical movement of biochar in soils and how it affects soil erosion,” she says.

The field study takes place at SU’s Welgevallen Experimental Farm. Sika will be involved for the next two or three years – the duration of her studies – but the overarching research project will carry on for the next 30 years.

Sika did some ground-breaking work during her master’s degree research when she studied the effects of biochar on the acidic sandy soil commonly found in the Western Cape.

“Pinewood was used as a feedstock to make the biochar by a carbonisation process called pyrolysis. This means that the feedstock was burned under conditions where little or no oxygen was available.

“Biochar research is quite new in South Africa and we did not know how much biochar would have to be applied for optimum results. I also studied nutrient uptake and the leaching of nutrients from biochar amended soils. We found that when biochar is applied to the soil, the fertiliser remains in the soil for longer.”

Sika found that if pinewood biochar is used in sandy acidic soil, it should be applied at an upper level of 10 tonnes per hectare. Concentrations of biochar that were too high resulted in over liming of the soil, which caused nutrient deficiencies.

In contrast to the research she is doing for her PhD, the research for her master’s degree was done in a greenhouse where winter wheat was used as a test crop.

The biochar research is part of the Food Security Initiative of Stellenbosch University’s HOPE Project, which is aimed at seeking solutions for major societal challenges.

In South Africa, as in the rest of the world, answers need to be found to agricultural challenges in order to ensure food security in a world where the population is increasing dramatically. Biochar can help to improve crop yields.

Sika explains that forests and vegetation are not necessarily threatened with the advancement of biochar.

“A number of feedstock can be used – including animal waste and vine pruning. The pinewood I used for my master’s studies was chippings (sawmill wastes).”

Sika initially wanted to study winemaking after she read an article as a 9-year-old about Jabulani Ntshangase, a black wine connoisseur. She kept the clipping in her memory box for years and when she had to make her final decision, she chose Stellenbosch because it was the only university offering the relevant course.

In her first year she realised she did not really want to pursue her studies in this field, but fell in love with soil science during a module which formed part of the second year BScAgric syllabus.

“Although I decided to change courses in my second semester, I worked hard to finish my degree in the original four years. I made life extremely difficult for myself but am quite proud that I succeeded in obtaining my first degree in four years,” Sika says. — STEPHANIE NIEUWOUDT

• Click here for more information on the Stellenbosch University Food Security Initiative.