Effect of bottom leaf removal and
fertiliser rates on the yield and quality of
flue-cured tobacco in Zimbabwe
Chapman Koga (BSc, MPhil) - Agronomist
TOBACCO RESEARCH BOARD
KUTSAGA
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Presentation Structure
1) What is bottom leaf removal (pruning)
2) Effect of pruning on tobacco yield
3) Effect of pruning on cured leaf chemistry
4) Conclusion
5) Recommendations
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CROP PRODUCTIVITY SERVICES
Mandate
To develop and disseminate
effective, efficient and
sustainable tobacco best
management practices
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What is bottom leaf removal
Also referred
to as pruning
or priming
New leaves develop and the plants topped at the desired height
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Background
1) Changes in market preferences – P&X vs C,L&T
2) Quality concerns – ‘Sand’ leaves, low prices
3) To delay ripening - Dry land vs Irrigated crop
4) Disease control – Proximity to the ground
exposes lower leaves to soil borne pathogens.
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Quality
Nicotine
Aroma
Sweetness
Impact
Lipids
Volatile oils
Polyphenols
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Brazil
Malawi
Zimbabwe
Topical issue
worldwide
USA
Research in other
countries 2017
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Zimbabwean perspective
Study period – 2014-15, 2015-16 and 2016-17 seasons
Tobacco varieties – K RK26 (fast growing and fast ripening)
K RK71 (slow growing and slow ripening
Planting times – Irrigated (1st of September)
Dry land (End of October)
Rainy season – November to April (800-1 000 mm)
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Objectives
To determine the effect of bottom leaf
removal, fertiliser rates and topping height
on the yield and quality of selected flue-
cured tobacco varieties
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Experimental design
Design: Split-split plot
Main plot: Topping height
1) 14 leaves
2) 18 leaves
14 TH
18 TH 18 TH
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Experimental design...cont’d
Sub-plot: Fertiliser level
1) Standard fertilizer programme based on soil analysis:
High C basal, NPK 6:28:23 applied at 500 kg/ha
+ 40 kg/ha N: NH4NO3 (34.5%N) at 4 WAP
2) High C (NPK- 6:28:23) - 500 kg/ha at planting
+ 40 kg/ha N: NH4NO3 (34.5%N) at planting
+ 400 kg/ha High C at leaf removal
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Experimental Design...cont’d
Sub-sub plot: Pruning level
1) 0 leaves
2) 6 leaves
3) 10 leaves
Done at 6 WAP or
12 leaf stage
10 leaves pruned 0 leaves pruned
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Results
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Irrigated trial results
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Variety - K RK26 (Interaction effects)
0
1000
2000
3000
4000
5000
Yie
ld (K
g/ha)
Influence of leaf removal & fertiliser levels on yield
a
b
a
0 6 0 6
p < 0.05
0
1000
2000
3000
4000
Yie
ld (kg/ha)
Influence of topping height & leaf removal on yield
0 10 0 6 10
14 leaves 18 leaves
p > 0.05
a a a
Adjusted fertiliser Standard fertiliser
6 10 10
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0
1000
2000
3000
4000
3 193 3 650
3 056
Yie
ld (K
g/ha)
Number of leaves removed
Influence of leaf removal on yield
a
0 6 10
p < 0.05, LSD = 477
Variety - K RK26 (Main effects)
0
1000
2000
3000
4000
14 leaves 18 leaves
3 140 3 459
Yie
ld (kg/ha)
Topping height
Influence of topping effects on yield
p > 0.05
a b
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Variety – K RK71 (Interaction effects)
0
1000
2000
3000
4000
Yie
ld (K
g/ha)
Influence of leaf removal & fertiliser levels on yield
Adjusted fertiliser Std fertiliser
6 10 0 6 10 0
1000
2000
3000
4000
Yie
ld (kg/ha)
Influence of topping height & leaf removal on yield
TH 14 leaves TH 18 leaves
0 6 10 10 6 0
p > 0.05
0
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0
1000
2000
3000
4000
3 140 3 264 2 809
Yie
ld (kg/ha)
Number of leaves removed
Influence of leaf removal on yield
0
1000
2000
3000
4000
14 leaves 18 leaves
2 898 3 244
Yie
ld (kg/ha)
Topping height
Influence of topping height on yield
Variety – K RK71 (Main effects)
p > 0.05
0 6 10
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Summary of Irrigated trial results
2015 vs 2016 seasons
Variety 2015 highest
yield
2015 standard
treatment
2016 highest
yield
2016 standard
treatment
K RK26 3 138 kg/ha
(P6, TH18, F+)
2 717 kg/ha
P0, TH18, F
4 238 kg/ha
P6, TH18, F+
3 135 kg/ha
P0, TH18, F
K RK71 3 131 kg/ha
P6, TH18, F
2 801 kg/ha
P0, TH18, F
3 711kg/ha
P6, TH18, F
3 135 kg/ha
P0, TH18, F
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Dry land trial results
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0
500
1000
1500
2000
2500
3000
2703.55 2766.68 2573.5
Yie
ld (kg/ha)
Number of leaves removed
K RK26
0 6
Influence of leaf removal on yield (Main effects)
0
500
1000
1500
2000
2500
3000
2972.93
2293.43 2591.6
Yie
ld (kg/ha)
Number of leaves removed
K RK71
p > 0.05
10 0 6 10
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Summary of Dry land trial results
2015 vs 2016 seasons
Variety 2015 highest
yield
2015 standard
treatment
2016 highest
yield
2016 standard
treatment
K RK26 3 007 kg/ha
(P3, TH18, F+)
2 280 kg/ha
P0, TH18, F
2 934 kg/ha
P6, TH18, F+
2 585 kg/ha
P0, TH18, F
K RK71 2 459 kg/ha
P0, TH18, F+
2 275 kg/ha
P0, TH18, F
3 554 kg/ha
P0, TH18, F
Same treatment
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0
1000
2000
3000
4000
2014/52015/16
2016/17
Yie
ld (
kg/ha)
Season
Irrigated K RK26
0 leaves
6 leaves
10 leaves
0
1000
2000
3000
4000
2014/52015/16
2016/17
Yie
ld (
kg/ha)
Season
Irrigated K RK71
0 leaves
6 leaves
10 leaves
0
1000
2000
3000
2014/52015/16
2016/17
Yie
ld (
kg/ha)
Season
Dry land K RK26
0 leaves
6 leaves
10 leaves0
1000
2000
3000
2014/52015/16
2016/17
Yie
ld (
kg/ha)
Season
Dry land K RK71
0 leaves
6 leaves
10 leaves
Influence of pruning on yield across seasons
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Effect of pruning on quality (Cured leaf chemistry)
1) Nitrogen
2) Sugars
3) Starch
4) Nicotine
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19.6
19.8
20
20.2
20.4
20.6
0 leaves6 leaves
10 leaves
Su
gar
con
ten
t (%
)
Pruning level
Influence of pruning on cured leaf sugar content
p>0.05)
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1.94
1.96
1.98
2
2.02
0 leaves 6 leaves 10 leaves
Nit
rogen
con
ten
t (%
)
Pruning level
Influence of priming on cured leaf Nitrogen
p>0.05)
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2.72
2.76
2.8
2.84
2.88
2.92
0 leaves 6 leaves 10 leaves
Nic
oti
ne c
on
ten
t (%
)
Pruning level
Influence of pruning on cured leaf Nicotine
p<0.05
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Conclusion
1. Response to lower leaf removal is variety and planting date dependent
• K RK26, a fast growing variety responded positively compared to
K RK71, a slow variety
• Removing 6 leaves improved yields for the early planted crop for both
varieties, but had minimal yield effect on the dry land crop
2. It seems fertilizer adjustments are required to compensate for
nutrients lost during pruning
3. Standard topping height (18 leaves) gave higher yields
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Other field observations
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10 leaves removed 0 leaves removed
Effects of pruning on leaf development
Lizard tail – lanceolate/ elliptic Broad leaves – Ovate shaped
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1.5
1.6
1.7
1.8
1.9
2
0 leaves 6 leaves 10 leaves
Leaf L/W
rati
o
Pruning level
Influence of pruning on leaf architecture
Elliptic Ovate
p=0.006, LSD = 0.13
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Lower topping (14 leaves) - Angular leaf spot
Higher chlorophyll
content - SPAD
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Recommendations
1. Pruning 6 leaves optimum; 10 leaves excessive
2. Fertilizer adjustment required to obtain yield increases
3. Standard topping height to be maintained (18 leaves)
4. Irrigated crop benefits more from pruning compared to dry land
5. A fast growing variety responds better to this practice
6. Leaf removal exercise could be a value addition practice that can
improve farmers’ income – up to 1 100 kg/ha yield increase and ~US$2 800
value gain from the economic analysis
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Are we eliminating the
importance of priming
leaves in cigarette
blending???
Smoke scientists?
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Acknowledgements
• Dr. D Rukuni (co-author)
• TRB Board, Management & Staff
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Gracias a todos!!
TOBACCO RESEARCH BOARD
KUTSAGA
[email protected] 00263 772 675 623
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