With the adoption of conservation agriculture growing in South Africa, various Agricultural Research Council (ARC) institutes have now started to research it. Peter Hittersay reports.
Conservation agriculture (CA) is growing in South Africa. Now the Agricultural Research Council (ARC) has launched a new programme to increase the capacity of researchers, acquire good quality data, disseminate information and improve interdisciplinary and inter-institute collaboration.The ARC Institute for Soil, Climate and Water (ISCW) has launched one of these projects, an on-station five-year (mid-2007 to mid-2012) research strategy. This is in collaboration with the ARC’s African Pollinator Initiative (API) and Plant Protection Research Institute (PPRI).
The research investigates specific impacts of CA under controlled experimental conditions, and mostly develops new research methods.
The research wants to establish the roles of CA’s key principles, especially under different cropping systems, to contribute to soil health and to help restore agro-ecosystem. It also aims to investigate the effects of CA on carbon sequestration and greenhouse gas emissions. Researchers will measure carbon dioxide, nitrogen dioxide and methane emissions under conventional and conservation tillage, and evaluate their impact on the yield of the maize crops.
The research covers soil carbon; nutrients and aggregate stability; crop production (yields and biomass), greenhouse gas emission, soil microbiology, nematodes, mycorrhiza and soil water.
Soil water is measured every two weeks throughout the year on selected plots, with a neutron moisture gauge (Waterman model). Continuous soil water content is also measured at two-minute intervals in selected plots, using capacitance probes.
In future, this research will cover some Highveld areas where monocropping under conventional tillage and fallowing to allow moisture retention is believed to be essential.
These trials may establish whether one of CA’s principles – maximum soil protection using crop residue or green manure cover crops which capture rainfall, moderate temperatures, and retain moisture – applies in this area. A method is also being developed to measure greenhouse gas (GHG) emission from agricultural soils. The three important agricultural GHGs are carbon dioxide, methane and nitrous oxide. The ARC has bought a probe to log carbon dioxide level, and temperatures at different intervals. This provides continuous readings for several hours. Methane and nitrous oxide are measured by collecting gas samples in airtight containers, which are then sent to a lab for analysis.
No results are available at this stage of the project and after only one season, no significant changes in crop yield have been measured. A general trend was observed where reduced tillage plots showed higher yields than conventionally ploughed ones (see Graphs 1, 2 and 3). Preliminary soil water levels were also higher in the unploughed soils. One season is still too short a time to observe CA’s effects, but preliminary data already indicate a beneficial trend.
Contact Dr Hendrik Smith, Programme Manager of the ARC-ISWC, on 012 310 2500 or 082 331 0456, or e-mail [email protected]. |fw