Abstract:
Soil acidity, which is associated directly with deficiency of nutrients like phosphorus (P);
nitrogen (N) and potassium (K) and is accompanied by toxicity of aluminium (Al), iron (Fe)
and manganese (Mn) appear to be the major constraint to crop production in western parts of
Ethiopia in particular. Therefore, three field experiments were carried out in the acidic soil of
Assosa, western Ethiopia, for two years in 2014 and 2015 main growing seasons. Thus, the
first experiment was conducted with the objective to assess the effect of integrated application
of compost (0, 5 t ha-1), lime (0, 1.5, 3 t ha-1) and P (0, 20, 40 kg P ha-1) on growth, yield
components, yield and P use efficiency of maize; and to assess subsequent changes on selected
physico-chemical properties of the soil. The second experiment was conducted with the
objective to assess the effect of integrated application of compost (0, 5 t ha-1), lime (0, 1.5, 3 t
ha-1) and N (0, 69, 138 kg N ha-1) on growth, yield components, yield and agronomic
efficiency of maize; and to assess subsequent changes on selected physico-chemical properties
of the soil. The third experiment was conducted with the objective to assess the effect of
integrated application of inorganic N (0, 69, 138 kg N ha-1), P (0, 20, 40 kg P ha-1) and K (0,
80 kg K ha-1) on growth, yield components, yield, and agronomic efficiency of maize; and to
assess subsequent changes on selected physico-chemical properties of the soil. All experiments
were laid out in randomized complete block design with three replications. The results of the
first experiment showed significant (P<0.05) main effects of year, compost, lime and P on
plant height, dry biomass yield, grain yield, agronomic P efficiency and P uptake. There was
significant (P<0.05) interaction effects of year with P, compost with P and lime with P on the
apparent recovery efficiency of maize. The main effects of lime and compost and interaction
effects of lime and year showed significant (P<0.01) effect on the exchangeable Al. The
interaction effects of year, lime and P significantly (P<0.01) affected the soil pH, organic
carbon (OC), total N and exchangeable acidity of the soil. The interaction effects of year,
compost, lime and P significantly (P<0.01) affected the available P of the soil. The results of
the second experiment showed significant (P<0.05) interaction effects of year with N on the
days to tasseling, LAI, number of ears per plant and grain yield of maize; interaction of year
with lime on TKW, grain yield and; while the interaction of compost with lime showed
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significant (P<0.05) effect on plant height and dry biomass yield of maize; interaction of
compost and N also showed significant difference on agronomic N efficiency of maize. The
interaction effects of year, compost and lime showed significant (P<0.05) effect on the CEC,
available P and exchangeable Al. The interactions amongst year, compost, lime and N also
showed significant (P<0.05) effect on the soil pH, OC, total N and the exchangeable acidity.
In the third experiment the LAI, plant height, ear length, number of kernels per ear, dry
biomass yield, grain yield and agronomic P efficiency of maize were significantly (P<0.05)
affected by the main effects of N, P and K. The days to tasseling, silking and agronomic N
efficiency were significantly affected only by the main effect of K; while the harvest index and
agronomic P efficiency were significantly affected by N alone. The main effect of P showed
significant (P<0.05) effect on CEC and available P; and the main effect of N showed
significant effect on the soil pH and exchangeable acidity. In general, there was a grain yield
loss from the first (3.84 t ha-1) to the second (2.84 t ha-1) and to third (2.74 t ha-1) objectives.
The soil pH decreased and exchangeable acidity increased due to increasing rate of N in the
third experiment, but exchangeable acidity decreased in the first and second experiments due
to applied compost and lime even in presence of N, as application of N together with compost
and lime have not affected the soil pH and exchangeable acidity. On the other hand, the
interaction of compost and lime when applied with P or N highly increased the available P in
the first two objectives. Therefore, integrated application of compost (5 t ha-1) and lime (1.5 t
ha-1) with P (20 kg P ha-1) or N (69 kg N ha-1) could best be use to improve yield of maize and
the soil property.