Articles: Postgraduate student articles

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Browsing Articles: Postgraduate student articles by Author "Fliessbach, A."

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    Microbial biomass and acid phosphomonoesterase activity in soils of the Central Highlands of Kenya
    (Elsevier, 2018-12) Kiboi, Milka N.; Ngetich, F.K.; Mugendi, Daniel N.; Muriuki, A.; Adamtey, N.; Fliessbach, A.
    Soil biological properties are the most sensitive soil quality indicators that respond quickly to short-term soil fertility management changes. We studied the combined effects of tillage and soil external inputs on total soil organic carbon and nitrogen, microbial biomass carbon (MBC) and nitrogen (MBN) and acidphosphomonoesterase activity (ACP). This was done in Meru South and Kandara sub-counties in Kenya for three consecutive cropping seasons. Tillage was the main factor [minimum (D0) and conventional (D15)], and soil external inputs were the sub-factors: sole mineral fertiliser (F), crop residues + mineral fertiliser (RF), crop residues + animal manure + legume intercrop Dolichos lablab L. (RML), crop residues + mineral fertiliser + animal manure (RFM), crop residues + Tithonia diversifolia + animal manure (RTiM), crop residues + Tithonia diversifolia + rockphosphate (RTiP) and an unfertilized treatment (Control). During the study period, we experienced frequent dry spells and meteorological droughts in the two sites. We found no significant effects of the tillage systems and mineral fertilisers applied alone or combined with crop residues on the biological properties. All additional organic inputs to the soils enhanced the biological soil properties. On average, MBC in the treatments with organic inputs only was enhanced by 51% in Meru South and 19% in Kandara. MBC-to-TOC ratio was significantly different (p = .0003) under soil external inputs in Meru South. On average, MBN in the treatments with organic inputs was enhanced by 66% in Meru South and 25% in Kandara. Compared with the control, ACP was higher under RML, RTiP and RTiM by 26%, 20% and 17%, respectively in Meru South. In Kandara, ACP was higher under RTiM and RTiP by 25% and 23%, respectively, compared with the control. The increase in microbial biomass indicates that application of organic inputs contributed to soil organic C, thereby stimulating the microbial growth and enzyme activity. Thus, use of organic inputs or in combination with mineral fertilisers are feasible alternatives for sustaining soil organic carbon through increased microbial biomass leading to soil organic matter build-up, which is a vital element of soil quality and fertility
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    Soil fertility inputs and tillage influence on maize crop performance and soil water content in the Central Highlands of Kenya
    (Elsevier, 2019-05) Kiboi, Milka N.; Ngetich, F.K.; Fliessbach, A.; Muriuki, A.; Mugendi, Daniel N.
    Rigorous land ploughing and cropping fertiliser treatment and mineral fertiliser combined with animal manure treatment) consistently enhanced maize crop growth and development as observed through enhanced chlorophyll content, plant height and yields. Application of soil fertility inputs significantly improved grain and stover yields except in the crop residue combined with animal manure and legume intercrop treatment (perhaps due to nutrients’ competition since Lablab has an intensive rooting system). Sole organic inputs enhanced soil moisture content in both sites. Emerging from the study, however, is the lack of advantage of minimum tillage over the conventional tillage, within the period under consideration. Thus, this study highlights the possibility of improving soil water holding capacity through application of organic inputs such as crop residues, Tithonia diversifolia and manure, either singly or in combination. It further underpins the uniqueness of an integrated approach to soil fertility and low soil moisture content in the tropical sub-humid regions experiencing erratic rainfallivity in the Central Highlands of Kenya due to low and declining soil fertility, inappropriate tillage methods, soil water scarcity and prolonged dry-spells. In this study, we assessed the effects of two tillage systems and soil fertility inputs on maize crop performance and soil water content. The research was carried out in Chuka and Kandara sites in the Central Highlands of Kenya for four seasons; long rains 2016, short rains 2016, long rains 2017 and short rains 2017. The experimental design was a split plot with tillage method (minimum and conventional) as the main treatments and soil fertility inputs as the sub-treatments: Sole mineral fertiliser, mineral fertiliser combined with crop residue, mineral fertiliser combined with animal manure, Tithonia diversifolia combined with phosphate rock (Minjingu), animal manure intercropped with Dolichos Lablab L. and a Control (conventional tillage with no inputs). Except for the control, and sole mineral fertiliser, crop residue was applied as mulch in all treatments. Based on the results, the treatments with mineral fertiliser (sole mineral fertiliser combined with mineral fertiliser treatment and mineral fertiliser combined with animal manure treatment) consistently enhanced maize crop growth and development as observed through enhanced chlorophyll content, plant height and yields. Application of soil fertility inputs significantly improved grain and stover yields except in the crop residue combined with animal manure and legume intercrop treatment (perhaps due to nutrients’ competition since Lablab has an intensive rooting system). Sole organic inputs enhanced soil moisture content in both sites. Emerging from the study, however, is the lack of advantage of minimum tillage over the conventional tillage, within the period under consideration. Thus, this study highlights the possibility of improving soil water holding capacity through application of organic inputs such as crop residues, Tithonia diversifolia and manure, either singly or in combination. It further underpins the uniqueness of an integrated approach to soil fertility and low soil moisture content in the tropical sub-humid regions experiencing erratic rainfall.