Liming strategies for barley and canola production under no-tillage.
Date
2021-03
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : Stellenbosch University
Abstract
ENGLISH ABSTRACT: The slow movement of lime in soil combined with no-tillage practices that restricts the incorporation of
surface broadcast lime deeper into the soil has led to an increase in soil acid stratification with depth in soils
under no-tillage over the long-term in the Western Cape Province of South Africa. A soil survey was
conducted across the southern Cape and Swartland regions of the Western Cape Province to determine the
extent and geographical spread of soil acidity and stratification (Objective 1). Soil samples were taken on
long-term no-tillage fields at depth increments of 0 – 5, 5 – 15 and 15 – 30 cm. It was found that 19.3% of the
soils surveyed in the Swartland had at least one depth increment with a pHKCl lower than 5.0, which is, in
general, below optimal for crop production. A field trial was also established in 2019 (Year 1) to investigate
the effect of form, fineness and purity of lime as well as different degrees of incorporating lime into the soil,
on soil chemical attributes (Objective 2) as well as on the growth and development of barley (Year 1) and
canola (Year 2) (Objective 3). The field trial consisted of ten treatments which included a control treatment,
95% calcium carbonate equivalent (CCE) surface broadcast calcitic lime, 88% CCE surface broadcast lime, lime
incorporated with either a disc plough, a chisel plough or a ripper, pelletised lime placed in-row (40 kg ha-1),
pelletised lime placed in-row and broadcast at 960 kg ha-1, pelletised lime placed in-row and broadcast at
770 kg ha-1 and pelletised lime broadcast at 1000 kg ha-1.
Minor differences in lime purity, type of tillage action (disc plough, chisel plough and ripper) used when
incorporating lime as well as form and fineness of lime (pelletised micro-fine) led to an increase (p ≤ 0.05) in
pHKCl up to a 30 cm depth, but did not show major crop responses within the first or second growing season
after receiving 810 - 1000 kg ha-1 of lime on a sandy loam soil (pHKCL of 5.05; SD ± 0.33 at 0 – 30 cm) that
received a total of 558 mm of rainfall.
Broadcasting pelletised micro-fine lime at the recommended rate however, led to the greatest (0 - 5 cm
depth) as well as the quickest increase in pHKCl, up to a 30 cm depth three months after liming. Applying less
than the recommended rate led to more effective neutralisation of soil acidity. Micro-fine pelletised lime
however, did not lead to a greater crop growth and productivity within two growing seasons following liming
compared to conventional class A lime.
There was however a trend for a one-off strategic tillage to result in greater crop biomass production. The
positive response of crop growth to a one-off strategic tillage was most likely attributed to deeper
redistribution of lime in the soil (15 – 30 cm depth), an increase in nutrient mineralisation and decrease in
nutrient stratification, alleviation of soil physical limitations and reduced weed pressure.
AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar.
AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar.
Description
Thesis (MScAgric)--Stellenbosch University, 2021.
Keywords
Liming of soils, Soil acidity, No-tillage -- South Africa -- Western Cape, Canola, Barley -- Breeding -- South Africa -- Western Cape, Crops -- Effect of soil acidity on, Conservation agriculture, UCTD