1. The effects of minimum and conventionaltillage systems on maize grain yield and soil fertility in western Ethiopia Tolessa Debele5th 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
9. 8000 a a MTRR MTRV CT 7000 b a a a a a b 6000 b b a b b b cGrain 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 yieldN levels Tillage system (T)(kg/ha) MTRR MTRV CT Mean69 5953 5595 5210 558692 6513 6173 5868 6185115 6953 6450 6227 6543Mean 6471 6073 5768LSD(0.05) T or N = 394 T x N = ns
11. Effects of tillage system onsoil physical and chemical properties
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 0.25Soil 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 30.0Figure 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.