Fighting witches and vampire in rice! Sowing time as a measure to regulate host plant-parasitic weed interactions in rain-fed rice production systems. Dennis E.
Fighting witches and vampire in rice! Sowing time as a measure to regulate host plant-parasitic weed interactions in rain-fed rice production systems. Dennis E. Tippe, Centre for Crop Systems Analysis - Wageningen University and Research, the Netherlands.
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Background In Sub-Saharan Africa (SSA), rice is an important cereal food crop and source of income. Rice demand is growing at a rate of >6% annually. - population growth (4% annually) - urbanization - dietary shift Rice production is increasing across SSA, but the continent still imports some 40% of its rice! 2
Background Constraints in rice production In SSA, rice is produced in three main eco-systems: upland rain-fed lowland rain-fed irrigated In rain-fed eco-systems, rice production is constrained by: drought poor soil fertility diseases weeds 3
Background Constraints in rice production
In SSA, farmers are losing
yearly half a million tons of rice because of parasitic weed infection
Root parasitic weeds, connect to their host plant and: Extract assimilates and
nutrients Reduce photosynthetic rate
Rodenburg J. et al., 2016. Parasitic weed incidence and related economic losses in rice in Africa. Agriculture, Economics and Environment 235 (2016), 306-317
Main parasitic weeds in rain-fed rice: Striga spp. – witchweed (uplands) Rhamphicarpa fistulosa – rice vampire (lowlands) 4
Parasitic weeds in rain-fed rice S. asiatica (witchweed)
Rhamphicarpa fistulosa (rice vampire)
Obligate hemi-parasite Cereal crops, wild grasses... Free-draining uplands
Facultative hemi-parasite Cereal crops, wild grasses... Water-logged lowlands
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Parasitic weeds management constraints Few research focused on parasitic weeds in rain-fed rice; most focus was on maize and sorghum.
With maize and sorghum, various management options were proposed: e.g,
use of fertilizers crop rotation use of resistant varieties weeding/herbicides
Yet, few control strategies have been effective and adopted Farmers need locally accessible and affordable strategies 6
Rationale: Developing affordable parasitic weed management strategies Rice production in Tanzania. Farmers’ hypothesis:
Sowing time can be used to reduce parasitic weed infection in rice.
However, late sown crops frequently face drought during grain filling, specially the traditional long duration varieties
Experiment: sowing dates x rice varieties with different growth cycles
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Treatments: Sowing dates x rice varieties To investigate the effect of sowing time on infection level and growth of S. asiatica and R. fistulosa, and of rice grain yield
Rice sowing dates: Five sowing times (20 Dec – 15 Feb) Two weeks intervals (14 days) used
3 rice cultivars (similar resistance level):
NERICA-14 (short), Supa India (medium/long) Mwangulu and (long) IR64 (short), NERICA-L-20 (medium) Supa India (long)
upland
lowland
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Treatments: Sowing date x Variety Experimental design split-plot - rice variety on main plot sowing date on sub-plot 5 replicates (75 plots in total)
Artificial parasite seed infestation in 2012 Crop establishment and management: rice seeds sown directly rice gap filled (21 DAS) to 3 plants hill-1 fertilizer: N-P-K (20-10-10) at (30 DAS)
Data: parasite number, biomass and rice grain yield
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140 d
120 100
c c
80 60 40 20 0
d c
b
c b a
b b a
b
b
2013
50
2013 S. asiatica biomass (g m-2)
S. asiatica maximum numbers (plants m-2)
Results: S. asiatica
b
40 30
ab
ab
20 10
a
0
b
ab
a a a
n.s
a
a
S1 S3 S5 S1 S3 S5
S1 S3 S5 S1 S3 S5 S1 S3 S5
Mwangulu Supa India NERICA-14 Sowing time x Variety
Mwangulu Supa India NERICA-14 Sowing time x Variety
S1 S3 S5
Parasite numbers and biomass decreased with later sowing -
in late sowing, Striga seeds returned to a state secondary dormancy 10
Results: S. asiatica 2013
2.5 b ab
2
Rice grain yield (t ha-1)
b ab
1.5
Early sowings resulted in
b 1
lower rice yields.
ab ab
ab
a
a 0.5
a
b
Short growth cycle variety
a
a
(NERICA-14) resulted in stable relatively high yields with delay in sowings.
-
0
S1
S3
S5
Mwangulu
S1
S3
S5
Supa India Sowing x Variety
S1
S3
S5
NERICA-14
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-
2012
70
c
b
60 50
c
a a
40
c
a
b b
30
a
20
a
a
10 0
-
S1
-
-
S3
S5
S1
S3
S5
S1
Supa India NERICA-L-20 Sowing time x Variety
S3 IR64
S5
2012
120 R. fistulosa dry weight (g m-2)
R. fistulosa maximum numbers (plants m-2)
Results: R. fistulosa c
100 80 60 b
40 ab
20 0
S1
a S2
S3 S4 Sowing time
S5
Parasite number and biomass increased with delay in sowing time. early sowing resulted in partial escape of parasite infection of the rice. 12
Results: R. fistulosa 9
2012
c
Rice grain yield (t ha-1)
8 7 6 5
Early sowing times yielded
c c
4
ab ab
b
3 2
ab a
-
S1
a
-
S3
S5
Supa India
higher rice grain yields, because of lower infection rates.
a
1 0
b
b
S1
-
S3
S5
NERICA-L-20 Sowing time x Variety
S1
S3
S5
IR64
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Conclusion Sowing
time influenced parasite development and rice grain yield, but the effect was very different for the two ecosystems.
In upland, with S. asiatica: Sowing rice from two to four weeks after the onset of the rain was found to be optimal, as parasite infection decreased and rice grain yields increased. Improved short-duration varieties can help to avoid risks of drought stress associated to late sowings.
In lowland, with R. fistulosa The best strategy is early sowing, as in this way parasite infection delays, resulting in low parasite infection and the highest rice grain yields 14
Thank you for your attention! Acknowledgments:
Financed by Netherlands Organization for Scientific Research through Science for Global Development (NWO-WOTRO;W01.65.327.00)
Additional funds was received from the CGIAR research programs funded by CCAFS and GRiSP
Jonne R.
Marc S.
Aad van A
Niels A.
Kayeke J.
Derek M.
Tippe, D. E
Daniel and Kamanda
Lammert B.
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