A presentation from the WCCA 2011 event held in Brisbane, Australia.

1. The effects of minimum and conventional
tillage systems on maize grain yield and soil
fertility in western Ethiopia
Tolessa Debele
5th World Congress on Conservation Agriculture
Incorporating 3rd Farming System Conference
26 – 29 September 2011
Brisbane, Australia

2. Introduction
• The major maize producing areas
 high yield potential
favorable environments.
• However, national average maize yield of 2.2 t/ha
• The inability to increase yield is attributed to:
 non-sustainable cropping practices, particularly plow- or
hoe-based cultivation,
soil and water loss due to erosion and
Declining soil fertility
• To overcome these inabilities:
Various management practices have to be
considered

3. Introduction …
• Generally, CT has been world-wide the basic tool
of cropping for centuries
It has been therefore an integral part of traditional
and/or conventional agriculture.
• However, the need to produce more food
for an increasing population
with decreasing soil and water resources
caused a shift to MT
• MT is recognized for its role in conservation of
both soil and water on account of CRs remaining
on the surface

4. Objectives
to evaluate the effects of tillage
system, residue management and nitrogen
fertilization on maize grain yield in western
Ethiopia
To determine the effects of the integrated
management practices on some soil fertility
parameters.

5. Methodolgy
• Experiments on integrated soil management practices
were conducted at five site for five-years in western
Ethiopia.
• The experiments were laid out in a RCBD with three
replications.
• Three tillage systems:
 MTRR = Minimum tillage with residue retention,
MTRV = Minimum tillage with residue removal
CT = conventional tillage
• Three N fertilization levels:
Recommended rate i.e. 92 kg N/ha
25% less & 25% more than recommended rate

6. Methodology….
• The experimental plots were kept permanent to observe
the carry-over effects over years
• For the MTRR and MTRV treatments soil
disturbance was restricted to the absolute
minimum,
viz. the soil was disturbed only to place the seed in
the soil at the time of sowing.
• In contrast, for CT treatments the soil was
plowed 3 times prior to sowing to obtain a
suitable seedbed.

7. Results and discussion
Effects of tillage system on
Maize grain yield

8. Table 1. Climatic data of Bako research center
Rainfall
(mm) May Jun Jul Aug Sep Oct CS Annual
1990-99 146.1 214.1 254.1 231.7 141.4 70.8 1058 1244
2000 135.1 278.2 236.9 289.6 162.0 103.4 1205 1346
2001 161.3 219.3 328.9 264.3 96.7 92.7 1163 1354
2002 68.3 236.0 239.2 205.9 42.1 0.0 792 1041
2003 5.7 265.1 420.6 434.4 39.9 11.5 1177 1355
2004 14.1 268.6 225.5 257.8 85.2 43.5 895 1061
2000-04 76.9 253.4 290.2 290.4 85.2 50.2 1046 1231

9. 8000 a a MTRR MTRV CT
7000 b a
a a a a
b
6000 b b a
b b b
c
Grain yield (kg ha-1)
b b
5000
4000
3000
2000
1000
0
2000 2001 2002 2003 2004 2000-2004
Years
Figure 1. Mean grain yield of five sites as affected by tillage systems.
Bars for each year with the same letter are not significantly different at
5% probability.

10. Table 2. Effect of tillage system, residue
management and N fertilization on maize grain
yield
N levels Tillage system (T)
(kg/ha) MTRR MTRV CT Mean
69 5953 5595 5210 5586
92 6513 6173 5868 6185
115 6953 6450 6227 6543
Mean 6471 6073 5768
LSD(0.05) T or N = 394 T x N = ns

11. Effects of tillage system on
soil physical and chemical properties

12. PR (Mpa) pH
0.0 0.5 1.0 1.5 2.0 5.3 5.4 5.5 5.6 5.7
0 0.0
0.13 0.14
5
Soil depth (cm)
Soil depth (cm)
0.17 7.5
10 LSD(0.05) LSD(0.05 ns
ns
15 15.0
ns MT RR ns
20 MTRR
22.5 MT RV
MTRV ns
25 CT ns
CT ns 30.0
30
Figure 3. Effect of tillage system on penetrometer
resistance (PR) of soil at different depths

13. Organic C (%) N (g kg-1)
1.0 1.5 2.0 2.5 3.0 1.0 1.3 1.5 1.8 2.0
0.0 0.0
Soil depth (cm)
LSD(0.0 0.25
Soil depth (cm)
7.5 7.5
0.21 ns
15.0 0.17 15.0
ns MTRR
ns MTRR
22.5 22.5 MTRV
MTRV
ns CT ns CT
30.0 30.0
Figure 5. Effect of tillage systems on OC at four depth
intervals

14. P (mg kg-1) K (mg kg-1)
5 10 15 20 25 150 175 200 225 250
0.0 0.0
LSD(0.05) LSD(0.05)
Soil depth (cm)
2.0
Soil depth (cm)
7.5 7.5 19
ns 17
15.0 MTRR 15.0
ns MTRV ns MTRR
22.5 CT 22.5 MTRV
ns ns CT
30.0 30.0
Figure 7. Effect of tillage systems on available P content of
soils at four depth intervals

15. Conclusions
• On average, MTRR increased grain yield by:
 6.6% as compared to MTRV and
 12.2% as compared to CT
• MTRR increased maize grain yield particularly when
maize crop faced terminal drought as compared to
MTRV and CT.
• When crop residues are removed, it takes at least two
years before adverse effects on grain yield reductions
become evident
• When crop residues are retained on the surface, it
requires at least two years before the beneficial influence
on grain yield are realized.

16. Conclusions …
• The grain yield was not affected by the
interaction of tillage system and N fertilization.
• Consequently, the recommended fertilizer rate of
92 kg N/ha for CT maize was also found
adequate for MT maize.

17. Conclusions …
• After 5 years the influence of the tillage systems
on PR, pH, organic C, total N, extractable P and
K was confined to the upper 0-15cm which is the
plow layer.
• In comparison with CT, MTRR resulted in a
higher PR and lower pH which is alarming
since both of them should be managed carefully for
sustainable cropping.
• However, MTRR resulted in higher contents of
organic C, total N, extractable P and K which is
reassuring
since all of them can be very beneficial for
sustainable cropping.

18. The way forward
• The results proved that MTRR can be introduced
successfully in the study area:
when it coincides with fertilization of 92 kg
N/ha
• However, MTRV is not an option at all to replace
CT from a soil quality point of view.
• The replacement of CT with MTRR should
contribute to sustainable maize production in
Ethiopia.

19. THANK YOU