Influence of long-term wheat residue management on some fertility indicators of an avalon soil at Bethlehem
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Date
2004
Authors
Kotzé, Elmarie
Journal Title
Journal ISSN
Volume Title
Publisher
University of the Free State
Abstract
Awareness of the environmental aspects of soil quality and crop production has been
increasing in recent years, which has led to renewed interest in crop residues as a
source of soil organic matter and nutrients for crops. Crop residue management is
known to both directly or indirectly affect soil quality and therefore soil fertility. Some
residue management practices have been tested since 1979 in a long-term wheat
trial at the ARC-Small Grain Institute near Bethlehem in the Eastern Free State on an
Avalon soil.
This trial offered an opportunity to study the influences of wheat residue management
practices on some soil fertility indicators and to establish whether differences in
wheat grain yield could be attributed to changes in the soil fertility indicators. The
treatments that were applied are two methods of straw disposal (burned and
unburned) x three methods of tillage (ploughing, stubble mulch and no tillage) x two
methods of weed control (mechanical and chemical). Soil samples were collected in
1999 at depth intervals of 0-50, 50-100, 100-150, 150-250, 250-350 and 350-450 mm
and analyzed for various soil fertility indicators, viz. organic C and total N as indices
of organic matter. In addition the pH, P, K, Ca, Mg, Na, Cu, Fe, Mn and Zn were also
determined.
The different tillage practices had a larger effect on organic matter than either straw
burning or weeding method, especially in the upper 100 mm soil. No tillage and to a
lesser extent mulch tillage, especially when combined with chemical weeding were
more beneficial to soil organic matter than when ploughing was combined with
mechanical weeding. Soil acidification seems to be retarded by mulch or no tillage
when combined with chemical weeding. The burning of wheat residues increased pH
significantly compared to no burning. It was found that the content of P, K, Cu, Fe,
Mn and Zn were increased with straw burning when compared to no burning. No
tillage and to a lesser extent also mulch tillage resulted in an accumulation of P, K,
Ca, Mg, Cu, Fe, Mn and Zn in the upper 150 mm soil compared to mouldboard
ploughing.
Grain yield does not coincide with the higher organic matter and lower acidity
resulting from mulch and no tillage. A reason for this may be that the nutrients
accumulated in the upper 150 mm soil with these two tillage practices, are not always
available for plant uptake. This aspect warrants further investigation.
Description
Keywords
Dissertation (M.Sc.Agric. (Soil, Crop and Climate Sciences))--University of the Free State, 2004, Soil fertility -- South Africa -- Free State -- Bethlehem, Crop residue management -- South Africa -- Free State -- Bethlehem, Tillage -- South Africa -- Free State -- Bethlehem, Organic matter, Straw disposal, Weed control methods, Soil acidity, Plant nutrients