Extent of Soil Acidity in No-Tillage Systems in the Western Cape Province of South Africa

Adriaan Liebenberg, John Richard (Ruan) van der Nest, Ailsa G. Hardie, Johan Labuschagne and Pieter Andreas Swanepoel
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Adriaan Liebenberg: Department of Agronomy, Stellenbosch University, Stellenbosch 7602, South Africa
John Richard (Ruan) van der Nest: Department of Agronomy, Stellenbosch University, Stellenbosch 7602, South Africa
Ailsa G. Hardie: Department of Soil Science, Stellenbosch University, Stellenbosch 7602, South Africa
Johan Labuschagne: Western Cape Department of Agriculture, Elsenburg 7606, South Africa
Pieter Andreas Swanepoel: Department of Agronomy, Stellenbosch University, Stellenbosch 7602, South Africa

Land, 2020, vol. 9, issue 10, 1-17

Abstract: Roughly 90% of farmers in the Western Cape Province of South Africa have converted to no-tillage systems to improve the efficiency of crop production. Implementation of no-tillage restricts the mixing of soil amendments, such as limestone, into soil. Stratification of nutrients and pH is expected. A soil survey was conducted to determine the extent and geographical spread of acid soils and pH stratification throughout the Western Cape. Soil samples ( n = 653) were taken at three depths (0–5, 5–15, 15–30 cm) from no-tillage fields. Differential responses ( p ≤ 0.05) between the two regions (Swartland and southern Cape), as well as soil depth, and annual rainfall influenced ( p ≤ 0.05) exchangeable acidity, Ca and Mg, pH (KCl) , and acid saturation. A large portion (19.3%) of soils (specifically in the Swartland region) had at least one depth increment with pH (KCl) ≤ 5.0, which is suboptimal for wheat ( Triticum aestivum ), barley ( Hordeum vulgare ), and canola ( Brassica napus ). Acid saturation in the 5–15 cm depth increment in the Swartland was above the 8% threshold for production of most crops. Acid soils are a significant threat to crop production in the region and needs tactical agronomic intervention (e.g. strategic tillage) to ensure sustainability.

Keywords: acid saturation; exchangeable acidity; calcium; magnesium; dolomitic lime; calcitic lime; wheat; barley; canola (search for similar items in EconPapers)
JEL-codes: Q15 Q2 Q24 Q28 Q5 R14 R52 (search for similar items in EconPapers)
Date: 2020
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