| dc.description.abstract | This study aimed at evaluating the different soil conservation measures
namely, level and graded bunds, level and graded fanya juus and grass strips in
soil conservation, nutrient retention and crop yields in the Harerge highlands
of Ethiopia. The experiment was conducted on 6 m by 30 m soil conservation
experimental plots. Runoff, soil loss and crop yield data which had been
collected since the establ ishment of the soil conservation measures in 1986
and which had not been ana lysed were used in this study. In addition, soil
samples were collected in 1097 in order to evaluate changes in soil properties,
since the establishment of the trials.
The soil conservation measures showed varied performance in controlling soil
loss, retention of diflerent soil properties and crop yields. Level bund and level
fanya juu were significantly different (ANOVA; p=O.05) from the control in
controlling runoff and soil loss. On the average, highest values of % clay (56
%), available phosphorous (P) (11.79 ppm), and. available potassium (K)
(86.48 ppm) were recorded Irom level fanya juu, grass strips and level bund
respectively and that of total nitrogen (TN) (0.212 %) and organic carbon
(OC) (1.54 %) from graded fanya juu. All soil properties tested except % clay'
were found to be lower at the upper positions of all the structural measures
tested with an increasing trend down the terrace positions. In particular, total
nitrogen, organic carbon and available phosphorous were significantly higher
(ANOY A; p=O.05) in the lower positions when compared with the middle and
upper positions of the interstructural spaces.
An average increase of '0.28 % and 0.16 % in OC and TN respecti.vely was
observed in 1997 as compared to the initial nutrient content determined at the
site in 1983. Available K, % TN, % clay, grain and biomass yield are
negatively correlated with soil loss with correlation coefficients (r) or -0.9, -
0.4, -0.9, -0.4 and -0.6 respectively. Level blind, level fanya juu, graded bund,
graded fanya juu and grass strips reduced soil loss by 99.5 %,100 %, 67 %, 54
% and 60 % respectively as compared to the control plot. Grain yield was
increased by 12.3 %, 4.2 %, 14.9 %, and 6.5 % on level bund, level fanya j L1~1"
graded bund and graded fanya j ULI respectively as compared to the control plot.
Level fanya juu, grass strips and graded bund ranked highest in soil loss
reduction, nutrient retention and grain yield increase respectively. In general,
all techniques tested at the research site reduced soil' loss and all of them
except the grass strip (J1ll1 graded bund increased grain yield and nutrient
retention respectively as compared to the control plot. Level bund showed a
relatively better overall performance than other techniques tested in the area
in terms of all parameters considered i.e. soil conservation, nutrient retention
and crop yield. | en |
