ABSTRACT
A two –year (2004/2005) field investigation was carried out
on the runoff plots at the University
of Nigeria Nsukka farm, to monitor the effects of cover
management practices on physical
properties, runoff and soil loss in Nkpologu sandy loam
soil. The management practices were
barefallow (BF), cocoyam (CY) sorghum (SG), legume (CP) and
grass (PM), under no-till
practice. There was no change in soil texture due to
treatments. The treatments generally
increased soil organic matter content compared with the
control. Bulk density was significantly
increased in all treatments with highest value (1.65Mg/m3)
in barefallow and lowest value (1.49
Mg/m3) in grass. There was no significant decrease in
porosity and pore size distribution. Mean
weight diameter (MWD) of aggregates and saturated hydraulic
conductivity (Ksat) were
significantly increased (p = 0.05).
The least values for MWD (1.06mm) and for Ksat (25.80cm/hr)
and highest for MWD (2.09mm) and for Ksat (49.20cm/hr) were obtained under
barefallow and grass treatments respectively. The percentage aggregate size
above 2.0mm was highest in grass and lowest in barefallow. Calculations showed
significant positive correlation (r = 0.50 at P = 0.05) between organic matter
and MWD. There was significant negative correlation (r = -0.60 at P = 0.05)
between organic matter and bulk density and significant positive correlation (r
= 0.80 at P = 0.05) between organic matter and saturated hydraulic
conductivity.
The pentades were generally wet during the study periods in
the two seasons. Cumulative runoff
was highest in barefallow and lowest in sorghum (87mm and
41mm respectively). The highest
soil loss of 1.13kg/m2 and relatively low loss of 0.55kg/m2
were obtained in cocoyam and
sorghum respectively in 2005.
Runoff and soil loss were reduced by 100% under grass and
legume. Cocoyam and sorghum reduced runoff by 20% and 53% respectively. Sorghum
reduced soil loss by 35%, while there were no differences in the percentage
reductions due to barefallow and cocoyam treatments. Runoff as percentage of
rainfall was highest in barefallow and lowest in sorghum (60.6% and 19.9%
respectively). Erosion rate was lowest in sorghum (0.2kg/m2/month) and highest
(0.4kg/m2 month) in cocoyam. Under BF the rate was 0.3kg/m2/month. The mean
yield of cocoyam was 1.35t/ha and that of sorghum was 0.88t/ha