Technical Yearbook 2023

JUNE

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Soil compaction – the silent killer of conservation agriculture? By Eduard Hoffman

In this article, the effect of compaction on water infiltration and redistribution, root growth and on aeration will be discussed. It is republished from the proceedings of the Soilborne Plant Disease Symposium 2022, with permission from the author and the organising committee. Introduction The population of the world is growing at a fast pace. According to a prediction released by Le Mouël and Forslund (2017) 20 , the earth’s population will be more than 9.7 billion in 2050. This population growth will be the highest in Asia and Africa. 20 This means that more food is needed, while the arable land available for food production will probably stay constant or will

shrink. 20 Only 14% of South Africa is regarded as arable. 12 Currently, there is a big drive to conserve this limited soil resource. This can be done by changing cultivation practices to conservation tillage practices. 4 Conservation practices for crop production are currently supported by many farmers to conserve both soil and water. South Africa’s water resources are limited and must be conserved. Without water, farmers will not be able to produce food and fibre for the increasing population of the world. In dryland farming, crop production is completely reliant on rainfall. 12 This research clearly showed how climate change aggravated the situation through a change in rainfall patterns. The long-term average annual rainfall declined from 510 in 1994 to 430 mm in 2020. 12 It is therefore essential to conserve our soil water for crop production as far as possible. This can be done by reducing the evaporation of water from the soil using stubble mulching on the

surface. 21 Mulching also creates a more suitable environment for macro- and microfauna in the soil. Conservation tillage is defined as practices that cause minimum disturbance of the soil to maintain at least 30% of plant residue on the soil surface. 4 This includes no-till, strip-till, ridge and mulch-till systems. Cultivation practices are thus adapted to till the soil less, while still achieving high production levels. No deep soil cultivation is practised. 4 Farmers that changed from conventional (clean) tillage to conservation tillage practices experienced a yield decline for several years before the yields slowly increased to previous levels. 7 However, after several years the yields started to decline again. This is attributed to the effect of soil compaction. Due to the ever increasing cost of production, farmers must produce more, work bigger farms, and have less time to perform all the necessary cultivation actions. 25 To achieve this, they must

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TECHNICAL YEARBOOK 2023