Effect of Nitrogen Fertilizer on Maize Performance, Nitrogen Use Efficiency and Soil Available Nitrogen Concentrations in Smallholder Farms in Rongo, Kenya
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Date
2019
Authors
Nduwimana, Desire
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
Reduced crop productivity among the smallholder farms is the main cause of food
insecurity in Sub-Sahara Africa (SSA). Maize is a staple food crop in Kenya and is
especially grown in the parts of North Rift and Western Kenya. In the Lake Victoria
region and particularly in Rongo sub-county, maize potential production is low ranging
between 0.8 to 1.6 tons ha-1. The low soil productivity is due to low soil fertility, low
soil nitrogen, inadequate use of inputs such as mineral fertilizers, improved maize
seeds, and inadequate agricultural practices to boost production. The purpose of this
study was to determine the effect of nitrogen fertilizer on maize yields, nitrogen use
efficiency (NUE), its effect on soil properties, and distribution in the soil profile and on
soil microbial population. The study was carried out at Kambija and Koderobara in
Migori County during the long rainy season from March–July, 2018. The experiment
was arranged in a Randomized Complete Block Design with three replications. The
treatments of N fertilizer (CAN) were at four levels (0, 25, 50 and 75 kg N ha-1). Tri-
Superphosphate (TSP) at 10 kg P ha-1 was applied as blanket. Maize variety (Sc Duma
43) was used as a test crop. Data were analyzed with the ANOVA procedure using
GenStat statistical software (15th edition) and treatment means separated using least
significant difference at (P≤0.05). Results indicated that treatments with nitrogen
fertilizer application significantly increased maize yields (p=0.001) at Kambija and
(p=0.01) at Koderobara. Applied N fertilizer at 50 kg N ha-1 exhibited the highest maize
yields compared to other treatments at both sites (4.34 t ha-1 for Koderobara and 3.41 t
ha-1 at Kambija). High rates of N fertilizer increase soil acidity and decrease maize
yields. Highest nitrogen use efficiency (NUE) was recorded at 25 kg N ha-1 with 23.84
at Kambija while at Koderobara was recorded at 50 kg N ha-1 with 22.61, in general
NUE decreased with increased applied N rates. At Kambija, 75 kg N ha-1 had the
highest N content in plant tissues with 2.07% in the heading stage while at Koderobara,
the highest N content of 1.90% was recorded at 50 kg N ha-1. Due to rainfall variability,
mineral N fractions (N03
− and NH4
+) were higher in sub-layers (10-20 cm and 20-30
cm depth) at seedling stages but at heading stages, N mineral concentrations were
higher in top-layers (0-10 cm depth) in both sites. Plots fertilized at 50 kg N ha-1
recorded highest concentration of available N in the soils in both sites of the experiment.
Soil microbial population was slightly increased by N fertilizer application and declined
with increased soil depth. Based on the results of this study, application of N fertilizer
at 50 kg ha-1 can be recommended among the smallholder farms for improvement of
maize yield in Rongo-sub County, Migori County, and the catchment of Lake Victoria.
Description
A Thesis Submitted In Partial Fulfilment of the Requirements for the Degree of Master of Science (Integrated Soil Fertility Management) In the School of Agriculture and Enterprise Development of Kenyatta University, September, 2019
Keywords
Nitrogen Fertilizer, Maize performance, Rongo, Kenya