IMPROVEMENT OF SOIL QUALITY AND MAIZE (Zea mays L.) PERFORMANCE USING SELECTED WEED SPECIES AS SOIL AMENDMENT
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Date
2018
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Abstract
Continuous cropping and poor soil management have resulted in reduced crop yield in
southern Guinea savannah (SGS) zone of Nigeria. Effective soil management strategy to
restore essential soil nutrients is thus required. This study assessed the potential of selected
weed species as soil amendment for improved soil quality and crop performance in SGS. The
specific objectives of the study were to: (i) assess the effect of soil amendments on the soil
microbial population, succession and diversity; (ii) evaluate the effects of the combination of
varying rates of the amendments on soil properties; (iii) evaluate the effect of the amendments
on soil productivity using maize as test crop; and (iv) investigate relationships between soil
quality indicators and maize yield components.
Weed species (Amaranthus spinosus, Aspilia africana and Chromolaena odorata) were
screened for ability to improve soil quality and maize performance in a preliminary potted
experiment using a complete randomized design (CRD). C. odorata was selected for the field
experiment. A randomized complete block design (RCBD) was adopted for field experiments
conducted in 2014 -2015 growing seasons with application of C.odorata at 10 t/ha and 15t/ha
singly and in combination with NPK (60-30-15kg/ha) as well as sole application of NPK (120-
60-30kg/ha) in maize plots. The plate culture technique was used for microbial analysis of soil
dilutions. Data collected on soil and yield computed were subjected to analysis of variance.
Pearson Product Moment correlation coefficient was used to establish relationships between
the measured soil quality indicators and maize yield components.
The findings of the study were:
(i) soil amendment with C. odorata increased soil microbial population (22.73 %)
and diversity (11.11 %) within the first four weeks of application. Proliferation of
saprophytes and suppression of pathogens were observed as decomposition C.
odorata progressed;
(ii) soil amendment with 7.5 % w/w C. odorata gave significantly (P≤ 0.05)
higher; mean soil moisture content (SMC), 60.97 g/kg, total porosity, 48.73 %,
bulk density, 1.36 g/cm3
and grain yield, (72.40 g/plant) than other treatments;
(iii) C.odorata at 15t/ha combined with NPK fertilizer (60-30-15 kg/ha) on the
field, increased soil organic matter (SOM) and ECEC by 80.91 % and 72.36 %
respectively after second year harvest. This rate had significantly higher values of
mean SMC (76.40 g/kg), total porosity (49.43 %), % water filled pore spaces
(20.68 %) and lower bulk density (1.39 g/cm3
to 1.34 g/cm3
) at the end of second
cropping season than other treatments;
(iv) C. odorata at 15 t/ha combined with NPK (60-30-15 kg/ha) produced
significantly higher mean maize cobs weight (11.46 kg/plot), mean grain yield
(4.67 t/ha)
(v) SOM was positively correlated with soil exchangeable bases, total N and available P
with correlation coefficient (r) ranging from 0.65- 0.93. Most measured yield
components were also strongly correlated with each other with r ranging from
0.13 to 0.99.
It was concluded that C.odorata has great potential for use as soil amendment in SGS zone to
improve soil productivity. Application of 15 t/ha of C. odorata combined with NPK (60-30-15
kg/ha) was recommended for improved soil quality and maize performance in the region