Availability of plant nutrients under conventional farming and conservation farming with and without biochar : a field study of maize on acidic, sandy loam in Zambia
Year: 2016
Type: dissertation
Abstract: Conservation farming (CF) has been promoted as an alternative and sustainable agricultural practice for many small-scale farmers in Sub-Saharan Africa (SSA) as a means to improve acid, degraded soil. Conservation farming involves minimum soil disturbance, retention of crop residues and crop rotation. In addition to CF, biochar (BC) has been advocated as a soil soil amendment for further soil improvement. Recent studies suggest that BC improves soil fertility, in particular through an increase in soil pH. BC in combination with conservation farming may have a positive impact on crop growth. Little is known about the dynamics of plant available nutrients in response to CF with and without BC and how this relates to systems under conventional farming (CV). The main objective of this study is to investigate the effects of CF, CF in combination with BC and CV on plant available nutrients.\n\nThe study was conducted at an experimental site (established in October 2015) on an acidic, sandy loam Acrisol at Mkushi, Zambia. Soil and soil water was sampled taken and analysed to investigate solute concentrations in soil water, plant available NH4+ and NO3, and general soil quality parameters including pH, total organic carbon (TOC) and nitrogen (TOT-N), cation exchange capacity (CEC) and exchangeable base cations.\n\nThe soils investigated in this study have a land-use history of 7 years of CF with planting basins. Background data indicated a significantly greater pH and TOC content in basins than in-between basins. This effect was still visible after the first year of conversion of CF to CV. Most of the results in this study are due to this legacy of CF, where soil under CV is a mix of\n\n(predominantly) in-between basin soil and (minor amounts of) basin soil. Results showed that CV had significantly lower pH soil and CEC, than CF, which could be explained by the mix of soil under CV. Soils under CF in combination with BC (CF+BC) had significantly higher TOC content, CEC and C to N ratio, than CF without BC. CF+BC did not give significantly higher soil extractable phosphorus (P) and pH in soil than just CF. Potassium (K+), but not calcium (Ca2+) and (Mg2+) concentrations in soil water, was not significantly higher in CF+BC than in CF. The respective plant available nutrients in soil water were significantly lower in CV than in CF probably due to the fact that CV soils primarily derives from the previous in-between basins. Most likely, these in-between basin soils (in contrast to the basin soils) have never received any dolomite and thus the concentrations of at least Ca2+ and Mg2+ are likely to be smaller in CV.\n\nCF in combination with BC did not result in higher concentrations of plant available nutrients, except for K+, than CF alone. CF+BC gave significantly higher content of TOC due to addition of biochar. CF gave significantly higher concentrations of plant available nutrients than CV.
Source: BIBSYS Brage (BIBSYS (Norway))
Author: Rikke Ødegård
Language: English
Subfield: Soil Science
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2605182108