Effects of leaf extracts, organic, inorganic fertilizers on soil ph, growth, soil macronutrients, beta-carotene of amaranthus in Kiambu County, Kenya
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Date
2018-05
Authors
Njeru, Charity N.
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
Soil is a significant reservoir for plant nutrients and hence necessary for plant
growth. Soil pH is a very important chemical property of the soil, as it dictates the
availability of plant nutrients. Low soil pH reduces soil nutrients. Some of the
factors leading to acid soils include continuous cultivation of soil due to scarcity
of arable land, excessive use of inorganic fertilizers, climate change and
deforestation. Reclamation of acidic soils includes addition of lime which is
expensive and requires re-application. These do not add all the nutrients required
by plants and may also contain soil contaminants which can make the soil
unproductive or may result in contaminated products harmful to humans if
consumed. Some plant leaves and their extracts reduce soil acidity and add plant
nutrients to soils as well as improving soil texture. The objective of this study was
to evaluate the effects of leaf extracts from selected trees on soil acidity, their
effect on soil macro nutrients, growth and betacarotene levels of amaranthus.
Plant leaves that were tested were Turril (Vitex keniensis), Mexican sunflower
(Tithonia diversifolia) and Indian nettle (Plectranthus barbatus).Amaranthus
(Amaranthus spp.) leaves are a good source of vitamin A, vitamin C, and folate
and were therefore used as a test crop. The experiment setup was in a randomized
complete block design (RCBD) with three replicates, arranged in a two by seven
factorial with two species of amaranthus.The soil treatments were the three leaves
extracts, lime, farm yard manure, inorganic fertilizer and control. Data on plant
height, leaf area, number of leaves, fresh weight and dry weight and levels of beta
carotene were collected from the amaranthus grown on the treated soil.AOAC
method was used for analysis of beta carotene. All data was subjected to analysis
variance (ANOVA) at 5% level of significance using SAS and least significant
difference (LSD) for means separation,every week for four weeks.The results
showed that leaf extracts,Plectranthus barbatus reduced soil acidity(pH5.9) to
(pH6.7),while inorganic fertilizer increased the acidity (pH5.9)to (5.3).On the
growth parameters ,FYM (47.0g) and leaf extract Vitex keniesis(45.17g) gave the
highest increase while control(26.3g) the least. On the macronutrients analysis in
the soil,F.Y.M(0.244%) gave the highest nitrogen levels while control gave the
least (0.138%), on phosphorus inorganic fertilizer(32.75ppm) and F.Y.M.(32.42
ppm) gave the highest levels while lime(25.08ppm)the least and on potassium,
leaf extract Plectranthus barbatus(1.416me/100g)gave highest levels and
control(1.311me/100g) the least. Betacarotene levels,F.Y.M(51.1μg) and leaf
extract Plectranthus barbatus(46.1μg)gave the highest betacarotene levels while
control the least(19.22μg).Amaranthus with high levels of betacarotene, have an
antioxidant which fights cancer cells.The outcome, of the research will be used in
recommendation of economical organic fertilizer leading to decreased dependence
on inorganic fertilizer especially for small scale farmers with 0.4 ha and below
within Juja Ward in Kiambu County,Kenya.
Description
A thesis submitted in partial fulfillment of the requirements for the award of degree of Master of Science (agronomy) in the school of agriculture and enterprise development, kenyatta university. May, 2018