The impact of tillage, cowpea-maize rotation and mulching on the physicochemical properties of a Haplic Plinthosol in Ghana
Loading...
Date
2015
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The study was carried out on a Haplic Plinthosol at the Faculty of Agriculture Research
station, Anwomaso in the semi-deciduous forest zone of Ghana for two years to assess
the impact of tillage, crop rotation and mulching on selected soil physical, hydrophysical
and chemical properties, grain and stover yields of maize and cowpea. The
experiment was a split-split plot arranged in randomized complete block design
(RCBD) with three replications. Tillage treatments were assigned to the main plots
and consisted of conventional-no-tillage rotation (CT – NT) and continuous
conventional tillage (CT – CT). In the sub plots were, cowpea-maize rotation (C – M),
maize monoculture (M – M) and cowpea monoculture (C – C). Crop residue mulch
that is, mulch (+R) and no mulch (-R) were assigned to the sub-sub plots. Maize and
cowpea were used as test crops. The results of soil physical parameters indicated
significantly (P < 0.05) lower soil bulk density and higher total porosity under the
treatment interactions, conventional-no-tillage rotation x cowpea-maize rotation or
maize monoculture x mulch. Soil penetration resistance increased with time and
ranged between 500.1 and 1079.6 kPa with practices that included conventional-notillage
rotation and mulch recording significantly (P < 0.05) lower values in both years
of study. On the other hand, treatment effect on dry and wet aggregate size distribution
and stability followed a consistent trend with conventional-no-tillage rotation x maize
monoculture or cowpea-maize rotation x mulch recording higher fraction of large
aggregates and stability than continuous conventional tillage x cowpea monoculture x
no-mulch at both the 0 – 15 and 15 – 30 cm depths. Saturated hydraulic conductivity
ranged between 5.40 and 16.74 cm h-1. Continuous conventional tillage x maize
monoculture x mulch significantly increased saturated hydraulic conductivity than
conventional-no-tillage rotation x cowpea-maize rotation x mulching. Sorptivity,
vii
steady state infiltrability and cumulative infiltration amount ranged between 24.7 and
167.1 mm s-1/2, 0.14 and 0.53 mm s-1, and 377 and 2823 mm respectively. These were
significantly higher under conventional-no-tillage rotation x cowpea-maize rotation
and mulching. Soil moisture storage increased with soil depth and was significantly
higher in the 0 – 15 cm depth under continuous conventional tillage x cowpea-maize
rotation x mulching. Meanwhile in the 15 – 30 cm depth, significantly higher soil
moisture was noted under conventional-no-tillage rotation x cowpea-maize rotation x
mulching. Soil organic carbon ranged between 1.54 – 1.86 % and 1.06 – 1.48 %
respectively in the 0 – 15 and 15 – 30 cm depths. The effect of treatment interactions
on soil organic carbon indicated significantly (P < 0.05) higher values under
conventional-no-tillage rotation x cowpea-maize rotation x mulching at the 0 – 15 and
15 – 30 cm depths.
Particulate organic carbon decreased with soil depth and was 3.71 g kg-1 (0.371 %)
soil and 2.44 g kg-1 (0.244 %) soil at the 0 – 15 and 15 – 30 cm depths respectively.
Water extractable organic carbon decreased with soil depth and was 13.95 mg kg-1
(0.01395 %) soil and 10.73 mg kg-1 (0.01073 %) soil at the 0 – 15 and 15 – 30 cm
depths respectively. Water extractable organic carbon was significantly (P < 0.05)
higher under conventional-no-tillage rotation x cowpea-maize rotation x mulch at the
two depths, the former treatment interaction together with conventional-no-tillage
rotation x maize monoculture x mulch and conventional-no-tillage rotation x maize
monoculture x no mulch showed significantly (P < 0.05) higher impact. Mineralized
carbon also decreased with soil depth and was 0.85 mg CO2 g-1 (0.085 %) and 0.54 mg
CO2 g-1 (0.054 %) in the 0 – 15 and 15 – 30 cm depths respectively. It was significantly
(P < 0.05) higher under continuous conventional tillage x cowpea-maize rotation x
mulch, continuous conventional tillage x cowpea monoculture x mulch and continuous
viii
conventional tillage x cowpea monoculture x no mulch in the 0 – 15 cm soil depth. In
the 15 – 30 cm depth, however, significantly (P < 0.05) higher mineralized carbon was
noticed under conventional-no-tillage rotation x maize monoculture x mulch,
conventional-no-tillage rotation x cowpea-maize x mulch and continuous conventional
tillage x cowpea monoculture x mulch. Maize grain yield increased in the second year
of the study with values ranging between 3.32 and 4.69 Mg ha-1 compared to 1.83 and
4.13 Mg ha-1 in the first year. The results showed significant differences in the impact
of treatment interactions with higher values recorded under conventional-no-tillage
rotation x cowpea-maize rotation x mulch and continuous conventional tillage x
cowpea-maize rotation x mulch in both years of study. Cowpea grain yield ranged
from 0.17 – 3.32 Mg ha-1 in 2013 and 0.61 – 2.03 Mg ha-1 in 2014 with significantly
higher values recorded under conventional-no-tillage rotation x cowpea monoculture
x no mulch and continuous conventional tillage x cowpea-maize x mulch in the former
and latter years respectively. Conventional-no-tillage rotation in combination with
cowpea-maize rotation or maize monoculture and mulch is recommended for the
potential of its attributes for sustained crop production in the semi-deciduous forest
zone of Ghana.
Description
A thesis presented to the Department of Crop and Soil Sciences, Faculty of Agriculture, College of Agriculture and Natural Resources, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana in partial fulfilment of the requirements for the award of the degree of Doctor of Philosophy in Soil Science,