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Transcript of Characterization of Agriculturally Important Rainfall variables for agricultural decision making,...
Characterization of Agriculturally Important
Rainfall variables for agricultural decision making,
Hawassa, Ethiopia Group members
Mr. Gizachew Legesse (EIAR/MARC) ([email protected])Mr. Minilik Tsega (EIAR/ HQ)Mr. Eshetu Zewidu (EIAR/MARC)Mr. Eskinder (EIAR/Mehoni ARC)
In Central Rift valley of Ethiopia, agriculture interfaces with extreme temporal and spatial variability of climate factors.
Amongst which rainfall is the most variable and the most important that greatly influence agricultural production and productivity.
For these reason, accurate analysis of rainfall is needed to generate valuable agro-climatic information that helps to reduce risks level of crop production.
Introduction
Study site
Rainfall analysis was performed for Hawassa zuria district that is found in Sothern Nation Nationality People (SNNP) regional state of Ethiopia.
1• Collecting and organizing
climate data and establishing flat databases suited for INSTAT and Genstat software
2• Turning climate data into
useful information through analysis and interpretation
3• Application of the
information for better decision making
Approach: Generation of Climate information through analysis
Rainfall variables and criteria for rainfall characterization1 • Start of the Season (SOS)
• Criteria: 3 days RT > 20mm and no dry spell of >10 days for the next 30 days
2
• End of the Season (EOS)• Criteria: any day after first of
September, when soil water starts to be at permanent deficit (WB < 50%).
3 • Length of Growing Period (LGP)• Criteria: EOS -SOS
4 • Total Season Water (TSW)• Criteria: The sum of rainfall total b/n SOS and EOS
5.
• Risk of a long dry spell
• The risk of longer dry spell of 5, 7, 10 and 15 days after sowing for any potential sowing date
Crop Coefficient for crop water requirement satisfaction index for maize crop variety having 140 day
maturity period • Value of crop coefficient for maize crop was taken from LEAP
software (fig) • Crop coefficient was interpolated for 14 dekade of the given
cropping season using INSTAT software• Computing CWRSI for maize variety having 140 day maturity
period
I. Summery of monthly rainfall total Hawassa, Ethiopia (1980-2010)
Jan_
t
Feb_
t
Mar_t
Apr_t
May_
t
Jun_
t
Jul_t
Aug_
t
Sep_
t
Oct_t
Nov_
t
Dec_
t
Rainf
all (m
m)
250
200
150
100
50
0
Monthly Rainfall total (1980-2010)
• Rainfall amount from April to September is greater than 100 mm per month.
I. Probability of occurrence of rainfall (1980-
2010)
p_rgfedcb
f_rgfedcb
f_oldgfedc
Overall chance of rain at Hawassa, Ethiopia (1980-2010)
Day of the year (DOY)400380360340320300280260240220200180160140120100806040200
Prob
abilit
ies
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
The overall chance of rainfall reveled that the probability of occurrence of rainfall in Hawassa ranges from 0.45 to 5.5 from 2nd dekade of April to the last dekade of September
fmgfedcb
Mean rain per rain day (mm) at Hawassa, Ethiopia (1980-2010)
Day of the month (DOY)400380360340320300280260240220200180160140120100806040200
Rain
fall (
mm
)
10
9.5
9
8.5
8
7.5
7
6.5
6
5.5
5
4.5
4
3.5
3
Average daily rainfall total per rainy day (1980-2010)
The average daily rainfall total per rainy days is 6.56 mm
Onset of rainy season(1980-2010)
SOSgfedcb
SOSWDgfedcb
Date of strat of the rain at Hawassa, Ethiopia (1980--2010)
Year2010200820062004200220001998199619941992199019881986198419821980
8 Jun
29 May
19 May
9 May
29 Apr
19 Apr
9 Apr
Based on the T-test result from the two onset definition (SOSWD) and (SOS ) , there is no significance difference in risk of failure (Replanting needed three times ).
The onset of rainy season in Hawassa ranges from April 1 to June 14.
Onset and Cessation of rainy season(1980-2010)
SOSgfedcb
EOSgfedcb
Year2010200520001995199019851980
Day
s of
Yea
r (D
OY
) 250
200
150
100
The mean onset and cessation of rainy season are 110th (April 2nd dekade) and 251th (September 1st dekade) DOY, respectively . Thus, the growing season accommodate about 141 days length of growing periods.
Probability of occurrence of LGP(1980-2010)
Percent Probability Plot of LGP
Length of growing period2001801601401201008060
Pe
rce
nt
100
90
80
70
60
50
40
30
20
10
0
From the result, the probability of occurrence of LGP, the chance of getting 140 days and less within the season is about 50%. one can recommend crop variety having 140 and less maturity period.
Risk of Dry spell, Hawassa, Ethiopia
sp5gfedcb
sp7gfedcb
sp10gfedcb
sp15gfedcb
Risk of dry spell based on the historic climatic condition (1980-2010)
Days of the Year (DOY)400350300250200150100500
Pro
ba
bili
ty
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Analysis of the risk of dry spell longer than 5, 7, 10, and 15 days shows that the risk of dry spell of longer than 10 and 15 days is less than 1 % in the growing period (April 2nd dekade to September 1st dekade). While, 5 and 7 day risk of dry spell gradually increases in month of May about 2.5 and 6.2 %. The result informed that farmer can use 140 day crop variety while considering the adjustment of planting time not coincide the risk of dry spell in the month May with that of sensitive growth stage of the selected crop (like flowering time).
Summary of rainfall variables(SOS, EOS ,LGP and SRT)(1980-2010)
92
245
79
27.4
107
246
140
50.0
166
296
193
86.0
0
50
100
150
200
250
300
350
SOS EOS LGP Seasonal rainfall total (cm)
Day
s o
f y
ear
and
Sea
son
al r
ain
fall
to
tal
Rainfall variables
25%tile
Min/ Max
Median
75%tile
Crop Water Requirement Satisfaction Index for maize crop variety having 140 day
maturity period
Crop water requirement satisfaction index for 140 maize variety
CWSI
X86gfedcb
CWSI values for rainfed maize at Hawassa, Ethiopia (1980-2010)
Year2010200820062004200220001998199619941992199019881986198419821980
CWSI
100
95
90
85
80
75
70
65
60
CWRSI analytical result of 31 year cropping season reveals that Maize crop having 140 maturity period was fully satisfied in 11 years . whereas in less than 70 % is only 1 years (2000). This may cause yield reduction.
Rainfall characterization analytical result raveled that in Hawassa zuria districts have unimodal rainfall characteristics with average starting of main rainy season in 2nd dekade while ending in 1st dekade of September. The risk of dry spell longer than 7,10 and 15 days is relatively low (<3%) . Thus, season can accommodate 140 LGP having 500mm on average.
CWRSI result indicate that maize crop varieties having 140 day maturity period have been satisfied from seasonal rainfall. Based on the result , maize crop having 140 day maturity period can be successfully grown the Hawassa zuria districts
A knowledge of rainfall characteristics in terms of onset and cessation date , length of growing period, seasonal rainfall
amount and duration of intermittent dry spell as well as CWRSI , are very useful for planning various agricultural operations.
Conclusion
Thank you!Soil
Atmosphere
Plant/ Sugar cane Animal
S
P
/A
A
Soil
Atmosphere
Plant/ Sugar cane Animal
S
P
/A
A