irrigation management and solutions to cope with ...

N. Poushkarov Institute of Soil Science, Agrotechnology and Plant Protection-ISSAPPNP

IRRIGATION MANAGEMENT AND SOLUTIONS TO COPE WITH AGRICULTURAL DROUGTH IN BULGARIA Z. Popova, М. Ivanova, K. Doneva, D.Martins, L. S. Pereira, M. Kercheva, V. Alexandrov, P. Alexandrova

GeoRisk 2012 Conference on Extreme Natural Hazards and Their Impacts 8-12 Dec 2012, Orange, Chapman University, CA, USA

month sum of precipitation (mm)

140 120 100 80 60 40 20 0

f)

May

June

July

August September



Experimental

140 120 100 80

140 120 100 80 60 40 20 0

g)

May

June

July

August September

60 40 20 0 May

June

July

August

September

140 month sum of precipitation (mm)


e)

120 100 80 60 40 20 0

a)

May

June

July

140 120 100 80 60 40 20 0

August September

h)

May

June

July

August

September


120 100 80 60 40

c)

140

0

d)

120 100 80 `

60 40 20 0

20

May

June

July

August

September



140

140

May

120 100 80 60 40 20 0

b)

May

June

July

August

September

Experimental fields of ISSAPPNP and meteorological stations of NIMH

June

July

August

September

Experimental Climate and seasonal SPI 3

Hig h P eak S eas on (J uly-Aug )S P I2

2

1

0

-1

-2

2,5

2004

2003

2002

2001

2000

1999

1998

1997

1996

1995

1994

1993

1992

1991

1990

1989

1988

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1986

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1971

1970

1969

1968

1967

1966

1965

1964

1963

1962

1961

1960

1959

1958

1957

1956

1955

1954

1953

1952

a)

1951

-3

Hig h P eak S eas on (J uly-Aug )S P I2

2 1,5 1 0,5 0 -0,5 -1 -1,5

2004

2003

2002

2001

2000

1999

1998

1997

1996

1995

1994

1993

1992

1991

1990

1989

1988

1987

1986

1985

1984

1983

1982

1981

1980

1979

1978

1977

1976

1975

1974

1973

1972

1971

1970

1969

1968

1967

1966

1965

1964

1963

1962

1961

1960

1959

1958

1957

1956

1955

1954

1953

1952

-2

b)

1951

Seasonal SPI (2) that is the average of the index for periods referring to maize sensitivity to drought, as “May -Aug”, “JuneAug” and “July-Aug” (Fig.1) were used to define categories of agricultural drought relative to summer crops in Bulgaria and SEE

Fig.1 Evolution of High Peak Season (July-Aug) SPI (2) at: a) Sofia and b) Plovdiv, 1951-2004.

Experimental Koinov V., Kabakchiev I., Boneva K. Atlas of the soils in Bulgaria. Zemizdat, Sofia (1998)

Experimental

WINISAREG model •

• • • • • • • • •

WINISAREG (Teixeira et al. 1992; Pereira et al. 2003) is a simulation tool for computing the soil water balance, generating alternative irrigation schedules and evaluating the respective impacts on crop yields. TW is separated in three zones: ASW, mm (i) excess (ii) optimum yield and (iii) water stress. 250 TAW 200 TAW=z(ППВ - ВЗ) (4) 150 Rmin is a fraction of TAW: 23/08 100 Rmin =(1-р)*TAW (5) 50 ASW =(Pe +Vz+ Ir +Gc- ETа -Dr) t (6) 0 100 150 200 250 ASW >TAW: а) DOY Dr= ASW-TAW ETmax= Кс ETо (12) ( Stewart 1976): (1-Ya/Ymax) =Ky (1-ETa/ETmax) (13) MAD=32% TAW

10.09.

300

Experimental I.

Calibration/validation of WinISAREG model Thracian Lowland

Kc coefficients 0.23

1.4

3

Soil Moisture, cm cm

-3

Milky ripening

1.2

0.13 0.08 100

130

160

190

220

250

280

DOY 1988

е)

Crop coefficient Kc

0.18

1 0.8 0.6 0.4 0.2

0.18 0.13

DOY 1988

Observed and simulated SM versus time (1988) model validation for high stress treatments 9 (e) and 11 (f) alluvial soil (116 mm m -1), Tsalapitsa, Plovdiv region

15/Октомври

30/Септември

15/Септември

31/Август

16/Август

1/Август

17/Юли

2/Юли

2/Юни

18/Май

Pustren Date Calapica

0.08 100 130 160 190 220 250 280 f)

17/Юни

0.23

3/Май

18/Април

Soil Moisture, cm3 cm-3

0

I.

Calibration/validation of WinISAREG model Thracian Lowland

Deriving Ky using long-term data from Pustren site: а) Kn-2L-611, 1972-1980г AEE=0.048; b) Н-708, 1981-1990г AEE=0.067; c) both hybrids, 1972-1990г (ETm-ETa)/ETm

0,5

1,0

0,0

0,5

1.0

y = 0,987x R2 = 0,495

1,0

(Ym-Ya)/Ym

y = 1.280x R2 = 0.615

0,5

b)

0.0 0.0

y = 1,477x R2 = 0,663

0,5

0.5

0,0

0,0

a)

0,0

1,0

(Ym-Ya)/Ym

1,0

(ETm-ETa)/ETm

0.5

c)

1.0

(Ym-Ya)/Ym

(ETm-ETa)/ETm

Results and Discussions Probability curves of NIRs soil of small, medium and large TAW, 1951-2004

Plovdiv region

500 450 400

300 250 200 150 100 50 0 Year PNIRs , %

2000 1994 1993 2003 1965 1952 1988 1996 1998 1986 1987 1962 1954 1970 1964 1990 1992 1981 2001 1953 1999 1958 1985 1991 1989 1968 1956 1974 1995 1978 1980 1972 1963 1984 1969 1975 1951 1973 1982 2004 1967 1979 1957 1960 1997 1966 1977 1976 1961 1955 1971 2002 1959 1983

NIRs, mm

350

1,4 3 5 7 9 11121416182022242527293133353638404244464749515355575960626466687071737577798182848688909294959799 TAW=136 mm m-1

TAW=116 mm m-1

TAW=180 mm m-1

Results and Discussions III. Vulnerability of agriculture to drought for climate regions and soil groups in Bulgaria Comparison of NIRs, TAW (136-157 mm m-1) 1951-2004 500 450 400 350

NIRs (mm)

300 250 200 150 100 50 0 0

10

Pleven

20

30

Silistra

40

50 PNIRs (%)

Sofia

60

Plovdiv

70

80

Sandanski

90

Varna

100

Results and Discussions Vulnerability of rainfed agriculture to drought Ky validation for rainfed maize, TAW=116 mm m-1

100 90 80

100

70

80 50

RYD, %

RYD (%)

90 60

40

70 60

30

50

20

40

10

30

49% risky years (26/53) for semi early hybrid with Ky=1.6

20

Year

71% risky years (38/54) for the late hybrids (Ky=1.6)

1993 2000 1952 1962 1965 1988 2001 1987 1992 1958 1994 1961 1974 1985 1956 2003 1990 1982 1954 1999 1963 2004 1969 1970 1997 1973 1953 1964 1966 1996 1978 1981 1979 1975 1998 1959 1984 1986 1983 1989 1957 1967 1955 1980 1960 1971 1972 1977 1968 1991 2002 1995 1976

0

10

Year

RYD Threshold

Observed RYD for semi-early hybrids, (Jivkov and Varlev) PYD, %

2000 1993 1965 1952 1994 1987 1996 2003 1992 1990 1988 1962 1954 1985 1964 1981 1982 1998 1973 1958 1953 1995 1968 1999 1956 1986 1980 2001 1970 1969 1963 1997 1978 1984 1974 1972 1989 1967 1951 2004 1966 1960 1979 1991 1957 1975 1983 2002 1977 1976 1961 1955 1971 1959

PRYD (% ) 1,4 3 5 7 9 111315161820222426283031333537394143454648505254565860626365676971737577788082848688909293959799 0 Simulated RYD with Ky=1.6

1.4 3 5 7 9 11 1214 1618 20 2224 2527 2931 33 3536 3840 4244 46 4749 5153 55 5759 6062 6466 68 7071 7375 7779 81 8284 8688 9092 94 9597 99 RYD Threshold for late hybrids

RYD H708 (Rafailov)

RYD H708 (Vurlev, Kolev, Kirkova)

Probability of exceedance curves of RYD under rainfed maize Ky=1.6 relative to: Sofia field Tsalapitsa experimental field, Plovdiv region, 1951-2004

III. Vulnerability of agriculture to drought Ky validation for rainfed maize

Simulated YD, % Simulated RYD, %

100

100 80 60 40 20 0

80 60 TAW 116, Ky=1.6, late hybrids H708

40

y = 0,99x R2 = 0,61

20

y = 0,99x

0 0 a)

20

40

YD,% 20 Observed 40 60

80

80

100

100

2

R = 0,82

60 40 20

40

60

80

100

YD semi early hybrids, Jivkov and Vurlev

YD H708 (Rafailov,Vurlev, Kolev, Kirkova)

(a) Tsalapitsa, Linear (YD H708 (Rafailov,Vurlev, Kolev, Plovdiv Kirkova))

20

Observed RYD, %

Observed RYD,%

Linear (YD Pioner (Rafailov) )

y = 0,95x

0

60

YD Pioner (Rafailov)

80

0

R2 = 0,61

0

Simulatedd RYD (%)

a)

Simulated RYD, %

One to one regression between observed and simulated TAW 116, Ky=1.6, Early hybrid RYD (%) TAW 116, Ky=1.6, late hybrids H708 100

100

Linear (YD semi early hybrids, Jivkov and Vurlev)

(b) Chelopechene, Sofia

80 60 40 y = 1.00x R2 = 0.66

20 0

(c) Pustren, Stara Zagora

0

20

40

60

Observed RYD (%)

c)

RYD H708 (Eneva)

80

100

Results and Discussions Rainfed maize yield and risky years Plovdiv region Ky=1.6

100 90 80

RYD,%

70 60 50 40 64.8% risky years (35/54) for TAW=116, 57.4% risky years(31/54) for TAW=136, 31.5% risky years(17/54) for TAW=180

30 20 10

1997 1977 1976 1961 1955 1971 2002 1959 1983

1982 1967 1951 2004 1979 1960

1972 1984 1963 1969

1995 1980 1978

1958

1981 1992

1962

1988 1996

Year PRYD,%

2000 1994 1993 1965

0

1,43 5 7 9 11121416182022242527293133353638404244464749515355575960626466687071737577798182848688909294959799

b) RYD Threshold late hybrids, %

TAW=180 mm m-1

TAW=136mm m-1

TAW=116 mm m-1

Probability exceedance curves of RYD under rainfed maize on the soil of small, medium and large water holding capacity TAW (116, 136, 180 mm m-1), Ky=1.6, at: b) Plovdiv for a late maize hybrid (H708), 1951-2004.

Results and Discussions III. Vulnerability of agriculture to drought for climate regions and soil groups in Bulgaria 1951-2004 Large TAW (180 mm m-1)

100

100

90

90

80

80

70

70

60

60 RYD (%)

RYD (%)

Yields of rainfed maize and risky years Medium TAW (136-157 mm m-1)

50 40 18 % risky years (9/51) for Pleven 35 % risky years (18/51) for Silistra 39 % risky years(20/51) for Sofia 59 % risky years (30/51) for Plovdiv 82 % risky years(42/51) for Sandanski 49 % risky years(25/51) for Varna

30 20 10

50 40 30 12 % risky years (6/51) for Pleven 10 % risky years (5/51) for Silistra 20 % risky years(10/51) for Sofia 29 % risky years (15/51) for Plovdiv 63 % risky years(32/51) for Sandanski 14 % risky years(7/51) for Varna

20 10

0

0 0

10

20

Pleven RYD Threshold Pleven TAW=136-157mm m-1 Plovdiv TAW=136mm m-1

30

40

50 PRYD (%)

60

Plovdiv/Silistra RYD Threshold Silistra TAW=136-157mm m-1 Sandanski TAW=136mm m-1

70

80

90

100

0

10

20

30

40

50

60

70

80

90

PRYD (%) Sofia RYD Threshold Sofia TAW=136mm m-1 Varna 136-157mm m-1

Pleven RYD Threshold Pleven Plovdiv

Plovdiv/Silistra RYD Threshold Silistra Sandanski

Sofia RYD Threshold Sofia Varna

100

RELATIONSHIPS BETWEEN ECONOMICAL YIELD THRESHOLD, GRAIN PRICE AND PRODUCTION EXPENSES 14.0 12.0 10.0 8.0 6.0 4.0 2.0 0.0 0

-1.0 y = 97.6x70

0,70

60

84.5x-1.0

0,60

-1.0 y = 74.7x50

0,50

-1.0 y = 60.7x 40

0,40 0,30 0,20

20

10

0,10

10

0

0,00

100

1.00

1,00

90

0.90

0,90

80

0.80

0,80

-1.0

0.70 y = 142.5x-1.0

0,70

-1.0

0.60y = 123.3x-1.0

0,60

0.50 y=

108.9x-1.0

0,50

88.6x-1.0

0,40

0

100

60

50

y = 97.6x y = 84.5x

40

y = 74.7x-1.0

30

y = 60.7x

-1.0

20

10

0.40y = 0.30

0,30

0.20

0,20

0,10

0.10

0

0 800 0 100 200 300 400 500 600 700 Grain price, lv t-1

70

0,00

0.00

0 100 200 300 400 500 600 700 800 500 600 700Grain 800price, lv t-1

200 300 400 -1 Grain price, lv t

Plovdiv/Silistra

Sofia

Lom

Pleven

Economical y = 1-RYD threshold

70

30

-1

y = 1-RYD(x)

80

0,80

20

800

-1

Economical RYD threshold, %

0,90

60

400 600 -1 Grain price, lv t

PRODUCTION PRODUCTION EXPENCES 800 lv haEXPENCES 1200 lv ha

90

RYD, %

Economical RYD threshold, %

200

90

30

1400 lv ha-1

y = 600x-1

1,00

40

1200 lv ha-1

y = 800x-1

100

50

1000 lv ha-1

y = 1000x-1

100

y=

800 lv ha-1

y = 1200x-1

PRODUCTION EXPENCES 800 lv ha-1

80

600 lv ha-1

y = 1400x-1

Economical y = 1-RYD threshold

Economical threshold of yield, t ha-1

16.0

Results and Discussions III. Assessment of drought vulnerability for climate regions and soil groups Table 1. Variability of rainfed maize grain yield characterized by the mean value, kg·ha-1, and the coefficient of variation Cv, %, for the considered climate regions and soil groups in Bulgaria, 1951-2004. South Bulgaria Climate region

Location

Maize hybrid

TAW (mm·m-1)

North Bulgaria

Moderate Continental

Transitional Continental

Mediterranean


Sofia Field

Thracian Lowland

Sandanski

Danube Plain

Transitional

North Black Sea

Sofia

Plovdiv

Stara Zagora

Sandanski

Pleven

Lom

Silistra

Varna

semi early

late

late

late

late

late

late

late

(kg·ha-1)

Cv mean Cv mean Cv mean Cv mean Cv mean Cv mean Cv mean Cv (%) (kg·ha-1) (%) (kg·ha-1) (%) (kg·ha-1) (%) (kg·ha-1) (%) (kg·ha-1) (%) (kg·ha-1) (%) (kg·ha-1) (%)

mean

Small

116

4421

42

3894

69

3723

59

2292

72

6419

50

4187

55

4866

46

4349

50

Medium

136

4920

37

4550

59

4299

52

2906

59

7237

44

4827

47

5616

40

5156

42

180

5896

29

5915

43

4250

41

8867

34

6094

35

7118

30

6810

30

Large

173

5483

41

Results and Discussions

Pleven,

RYD raimfed maize (%)

Plovdiv and

RYD raimfed maize (%)

III. Drought vulnerability categories according to climate region and soil group

RYD threshold 60

y = -23.61x + 47.22 2

R = 0.91

TAW=180 mm m-1

RYD threshold 67

y = -21.57x + 35.72 R2 = 0.79

0 -2,00 -1,50 -1,00 -0,50 0,00 0,50 1,00 1,50 2,00 2,50

0 -2,50 -2,00 -1,50 -1,00 -0,50 0,00 0,50 1,00 1,50 2,00 2,50

SPI (2) for "July - Aug"


Economical threshold of High Peak Season SPI2 “July-Aug” (the average SPI2 for July and August) indicating the risk relative to rainfed maize for each climate region/soil group in Bulgaria Soil groups according to total available water TAW: Climate Region Transitional Mediterranean Transitional Continental

Small 116 mm m-1

Medium 136-157 mm m-1

Large 173-180 mm m-1

Sandanski

+1.40

+1.00

+0.20

Stara Zagora

+0.50

+0.10

-0.50

Plovdiv

+0.15

0.00

-0.50

Lom

+0.15

-0.10

-0.75

Sofia

0.00

-0.25

-0.90

Silistra

-0.15

-0.50

-1.25

Pleven

-0.50

-0.75

-1.50

Varna

+0.21

-0.21

-1.05


Northern Black Sea

Results Groups of soil according to TAW Small 116 mm m -1 RYD % NIRs mm

Medium 136-157 mm m -1 RYD % NIRs mm

Large 173-180 mm m -1 RYD % NIRs mm

Intercept a Slope coefficient b R2 (%)

79.6 -15.0 75

312,3 -66,4 70

74.1 -15.7 77

294.2 -66.2 70

62.1 -16.1 78

256.6 -65.8 70

Stara Zagora Intercept a Slope coefficient b 2 R (%)

67.0 -19.9 80

259.2 -83.2 77

61.81 -20.5 82

243.3 -83.1 78

51.3 -20.5 83

211.4 -83.4 79

Plovdiv Intercept a Slope coefficient b R2 (%)

65.2 -24.8 92

244.4 -97.3 89

59.4 -24.7 92

226.7 -96.4 89

47.2 -23.6 91

189.9 -93.8 89

Lom Intercept a Slope coefficient b R2 (%)

57.7 -23.8 86

202.5 -81.7 80

51.3 -23.6 86

184.7 -81.5 80

38.5 -22.1 86

148.7 -78.9 81

Sofia Intercept a Slope coefficient b R2 (%)

48.4 -21.0 76

178.8 -78.2 76

42.6 -20.5 75

162.5 -77.1 75

31.2 -18.8 73

129.2 -73.3 73

Silistra Intercept a Slope coefficient b R2 (%)

56.1 -20.5 86

190.3 -68.5 84

49.1 -20.3 86

171.7 -68.5 85

35.9 -19.3 86

135.4 -67.4 85

Pleven Intercept a Slope coefficient b 2 R (%)

53.5 -23.3 82

202.4 -88.1 77

47.6 -23 81

184.8 -87.1 76

35.7 -21.6 79

148.4 -84.3 75

Varna Intercept a Slope coefficient b R2 (%)

63.6 -18.1 82

212.3 -59.6 73

56.9 -17.6 81

195 -58.7 74

43 -16.5 80

158.1 -56.72 73

Region Sandanski

Parameters of y=a+bx relationship between simulated RYD (%)/NIR (mm) and High Peak Season SPI2 “July-Aug” across soil groups and climate regions Bulgaria, 1951-2004

Results and Discussions III. NIRs threshold to cope with drought in the risky years

y = -84.34x + 148.40 R2 = 0.75

NIRs maize, mm)

Plovdiv and Pleven, TAW=180 mm m-1

NIRs maize, mm

y = -93.81x + 189.90 R2 = 0.89

NIRs threshold 235

0

0 -2.00 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50 2.00 2.50

a)

NIRs threshold

267

-2.50 -2.00 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50 2.00 2.50

b)



NIRs maize, mm

Sofia and Lom, TAW=180 mm m-1

c)

y = -78.88x + 148.72 R2 = 0.81 NIRs maize, mm

y = -73.33x + 129.23 R2 = 0.73 NIRs threshold 192

0 -2.50 -2.00 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50 2.00 2.50 SPI (2) for "July - Aug"

d)

NIRs threshold 216

0 -2.00 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50 2.00 2.50


The corresponding thresholds were identified for NIR, namely 240 and 270mm for Plovdiv and Pleven and 190 and 220 mm for Sofia and Lom/Silistra/Varna respectively.

Results and Discussions III. Drought vulnerability categories according to climate region and soil group SEE Economical threshold of High Peak Season SPI2 “July-Aug” (the average SPI2 for July and August) or SPI3 “June-Aug” indicating the risk relative to rainfed maize for each climate region/soil group in SEE

Soil groups according to total available water TAW:

Climate Region

Small 116 mm m-1

Medium 136-157 mm m-1

Large 173-180 mm m-1

Mediterranean

Podgorica‫٭‬

+2.30

+2.00

+1.20

Transitional Mediterranean

Sandanski

+1.40

+1.00

+0.20

Stara Zagora

+0.50

+0.10

-0.50

Plovdiv

+0.15

0.00

-0.50

Lom

+0.15

-0.10

-0.75

Sofia

0.00

-0.25

-0.90

Silistra

-0.15

-0.50

-1.25

Pleven

-0.50

-0.75

-1.50

-1.1

-1.4

Transitional Continental


Nis

Rimski Sancevi

-0.70

-1.00

Kikinda

-0.40

-0.6

Berane‫٭‬

0

-0.8

-1.5

Varna

+0.21

-0.21

-1.05

Typical Continental Mountainous Northern Black Sea

‫٭‬High Peak Season SPI3 “June-Aug”


III. Drought vulnerability mapping

Economical SPI2 “July-Aug” threshold, under which soil moisture deficit leads to severe impacts on yield losses for rainfed maize, Bulgaria.


III. Drought vulnerability mapping Spatial distribution of SPI2 “July-Aug”

Average 1970

Extremely dry 2000

Moderately dry 1981

Results and Discussions III. 4С Drought vulnerability mapping Spatial distribution of RYD (%)

Extremely dry 2000

Average 1970

Moderately dry 1981

Results and Discussions Spatial distribution of NIR

Average 1970

Extremely dry 2000

Moderately dry 1981

ANALYSIS OF PHYSICAL ASPECTS OF CLIMATE CHANGE

Trend line of monthly precipitation (mm) Rainfall, June

Rainfall, July Plovdiv 1951-2004 200 180 160 140 120 100 80 60 40 20 0

Year

y = -0.2738x + 57.493

1951 1955 1959 1963 1967 1971 1975 1979 1983 1987 1991 1995 1999 2003

Year

y = -0.7908x + 77.672

Rainfall, mm

200 180 160 140 120 100 80 60 40 20 0

1951 1955 1959 1963 1967 1971 1975 1979 1983 1987 1991 1995 1999 2003

Rainfall, mm

Plovdiv 1951-2004

Trend line of average monthly air temperature Tmax and Tmin (Co) Tmaxo, June Plovdiv 1951-2004 40 35 30 25 20 15 10 5 0

Tmax o

Year

Tmaxo, July Plovdiv 1951-2004

Year

Tmax o

y = 0.0305x + 16.049

1951 1955 1959 1963 1967 1971 1975 1979 1983 1987 1991 1995 1999 2003

Tmin o

Tmino, July Plovdiv 1951-2004 40 35 30 25 20 15 10 5 0

y = 0.0363x + 26.86

40 35 30 25 20 15 10 5 0

Year

y = 0.0329x + 29.335

1951 1955 1959 1963 1967 1971 1975 1979 1983 1987 1991 1995 1999 2003

y = 0.02x + 14.526

1951 1955 1959 1963 1967 1971 1975 1979 1983 1987 1991 1995 1999 2003

Tmin o

40 35 30 25 20 15 10 5 0 Year

1951 1955 1959 1963 1967 1971 1975 1979 1983 1987 1991 1995 1999 2003

Tmino, June Plovdiv 1951-2004

Trend Analysis by Modified Mann-Kendall test Table 1 Precipitation Trend Analysis Lom Pleven Plovdiv Sandanski Silistra Sofia Stara Zag. Varna January -0,17 0,25 -0,25 0,02 -0,19 -0,20 -0,39 0,03 February -0,56 0,74 -0,09 0,03 -0,04 0,05 -0,32 0,04 March -0,23 0,39 -0,14 0,05 0,46 0,11 0,00 0,06 April -0,05 0,94 -0,20 0,01 0,27 0,02 -0,39 0,02 May -0,09 0,67 -0,55 0,04 -0,21 0,16 -0,58 0,03 June -0,48 0,25 -0,92 0,06 0,05 -0,52 -0,39 0,02 July 0,30 0,36 -0,31 0,12 -0,08 -0,51 -0,44 0,21 August -0,05 0,15 0,06 0,02 0,18 0,27 0,11 0,04 September 0,50 0,49 -0,20 0,01 0,44 0,17 0,27 0,02 October -0,11 0,71 -0,43 0,01 0,14 -0,05 -0,29 0,03 November -0,40 0,23 -0,45 0,00 0,09 -0,23 -0,43 -0,01 December -0,02 0,83 0,10 -0,02 0,12 -0,01 -0,09 -0,02 Annual Precipitation -1,27 0,35 -3,52 0,03 1,14 -0,95 -3,30 0,02

Table 1, regarding precipitation, shows: oNo significant trend in January for all 8 station. oOn the other hand in June is found trend in 3 of the stations. oThese trends are responsible for a decrease in the annual precipitation amount in the station of Plovdiv (-3,52 mm yr-1) and Stara Zagora (-3,3 mm yr-1). oAlthough Varna shows trend in 6 months that only leads to an increase of 0,02

Trend Analysis by Modified Mann-Kendall test Table 1 Maximum Temperature Trend Analysis

January February March April May June July August September October November December Annual mean

Lom Pleven Plovdiv Sandanski Silistra Sofia Stara Zag. Varna 0,04 -0,01 0,01 0,02 0,02 0,05 0,05 0,02 0,06 0,02 0,03 0,03 0,05 0,04 0,08 0,03 0,07 0,03 0,05 0,05 0,06 0,05 0,09 0,05 0,01 0,00 0,00 0,01 0,02 0,00 0,02 0,02 0,03 0,02 0,03 0,04 0,04 0,03 0,04 0,04 0,03 0,03 0,04 0,06 0,03 0,05 0,05 0,04 0,02 0,02 0,03 0,04 0,03 0,05 0,04 0,03 0,01 -0,01 0,01 0,02 0,02 0,04 0,05 0,03 -0,02 -0,02 0,00 0,01 -0,01 0,01 0,00 0,01 0,00 -0,01 0,01 0,01 0,00 0,01 0,01 0,00 0,00 -0,03 0,00 0,00 -0,01 -0,04 0,00 -0,01 -0,01 -0,03 -0,01 -0,02 0,02 -0,01 0,00 -0,01 0,02 0,00 0,02 0,03 0,02 0,02 0,04 0,02

o June is the months with larger number of significant trends, 7stations. o January, February, April, August, October and November show no trend for the increase or decrease of the maximum temperature. o Stara Zagora and Silistra have an increase in maximum temperature in 4 months. o With the exception of Pleven all stations have a positive trend for max temperature, with a mean increase of 0,024 ⁰C yr-1.

Trend Analysis by Modified MannKendall non-parametric test Table 1. SPI-3 Trend Analysis (a refers to p-value; b to the sen’s slope)

lom a b January 0,29 -0,01 February 0,12 -0,02 March 0,00 -0,02 April 0,07 -0,02 May 0,55 -0,01 June 0,27 -0,01 July 0,57 0,00 August 0,76 -0,01 September 0,14 0,01 October 0,76 0,00 November 0,65 0,00 December 0,29 -0,01 Annual mean 0,11 -0,01

Plovdiv a b 0,46 -0,01 0,52 -0,01 0,55 -0,01 0,30 -0,01 0,05 -0,02 0,00 -0,03 0,00 -0,02 0,05 -0,02 0,38 -0,01 0,22 -0,02 0,00 -0,03 0,10 -0,02 0,01 -0,02

Pleven a b 0,26 -0,01 0,17 -0,02 0,50 0,00 0,98 0,00 0,81 0,00 0,44 -0,01 0,66 0,00 0,56 -0,01 0,05 0,01 0,75 0,00 0,37 -0,01 0,04 -0,01 0,66 0,00

Sandanski Silistra a b a b 0,43 -0,01 0,67 0,00 0,08 -0,01 0,58 0,00 0,00 -0,02 0,73 0,00 0,13 -0,01 0,18 0,02 0,02 -0,02 0,29 0,01 0,14 -0,01 -0,20 0,00 0,38 -0,01 0,26 -0,01 0,96 0,00 0,99 0,00 0,35 0,01 0,20 0,01 0,55 0,00 0,01 0,01 0,21 -0,01 0,14 0,02 0,60 0,00 0,52 0,01 0,06 -0,01 0,31 0,01

Sofia Stara Zagora a b a b 0,93 0,00 0,21 -0,02 0,81 0,00 0,05 -0,02 0,69 0,00 0,13 -0,01 0,71 0,00 0,09 -0,01 0,98 0,00 0,02 -0,02 0,27 -0,01 0,00 -0,03 0,05 -0,01 0,00 -0,03 0,12 -0,01 0,18 -0,02 0,74 0,00 0,59 0,00 0,42 0,01 0,93 0,00 0,76 0,00 0,10 -0,01 0,69 0,00 0,02 -0,02 0,59 0,00 0,00 -0,02

Varna a b 0,49 -0,01 0,05 -0,02 0,44 -0,01 0,37 0,01 0,99 0,00 0,13 -0,02 0,16 -0,02 0,87 0,00 0,06 0,02 0,07 0,02 0,66 0,01 0,42 0,00 0,63 0,00

Globally, the regions of Plovdiv and Stara Zagora with a decrease in precipitation and an increase in the temperature range may have consequences in the occurrence of droughts. That is explained in next two tables, in which the trends of SPI-3 and SPI-12 are computed . The results show, for SPI-3 that there is a significant trend for the increase of droughts in Stara Zagora and Plovdiv, being the months of May, June and July the ones who most contribute for this.

Trend Analysis by Modified MannKendall non-parametric test Table 1. SPI-12 Trend Analysis (a refers to p-value; b to the sen’s slope)

lom a b January 0,34 -0,01 February 0,18 -0,01 March 0,29 -0,01 April 0,22 -0,01 May 0,13 -0,01 June 0,17 -0,01 July 0,06 -0,02 August 0,07 -0,02 September 0,12 -0,02 October 0,13 -0,01 November 0,24 -0,01 December 0,08 -0,01 Annual mean 0,11 -0,01

Plovdiv a b 0,00 -0,03 0,00 -0,03 0,00 -0,03 0,00 -0,03 0,00 -0,03 0,00 -0,03 0,00 -0,03 0,01 -0,03 0,00 -0,03 0,00 -0,02 0,00 -0,03 0,00 -0,03 0,00 -0,03

Pleven a b 0,58 -0,01 0,61 -0,01 0,70 -0,01 0,51 -0,01 0,51 -0,01 0,59 0,00 0,68 -0,01 0,76 -0,01 0,57 -0,01 0,49 -0,01 0,63 -0,01 0,34 -0,01 0,81 0,00

Sandanski a b 0,01 -0,02 0,05 -0,02 0,03 -0,02 0,06 -0,02 0,03 -0,02 0,00 -0,03 0,00 -0,03 0,00 -0,03 0,01 -0,02 0,02 -0,02 0,01 -0,02 0,01 -0,02 0,01 -0,02

Silistra a b 0,50 0,01 0,66 0,00 0,61 0,01 0,57 0,00 0,48 0,01 0,64 0,00 0,63 0,00 0,66 0,00 0,53 0,01 0,41 0,01 0,34 0,01 0,36 0,01 0,55 0,01

Sofia Stara zagora a b a b 0,47 -0,01 0,01 -0,03 0,43 -0,01 0,00 -0,03 0,60 0,00 0,00 -0,03 0,61 -0,01 0,00 -0,03 0,37 -0,01 0,00 -0,03 0,39 -0,01 0,00 -0,03 0,32 -0,01 0,00 -0,03 0,22 -0,01 0,01 -0,03 0,24 -0,01 0,01 -0,03 0,32 -0,01 0,00 -0,03 0,20 -0,01 0,00 -0,03 0,42 -0,01 0,01 -0,03 0,35 -0,01 0,00 -0,03

Varna a b 0,59 -0,01 0,43 -0,01 0,54 -0,01 0,54 -0,01 0,61 -0,01 0,89 -0,01 0,79 -0,01 0,91 0,00 0,71 -0,01 0,97 0,00 0,64 -0,01 0,59 -0,01 0,77 0,00

For SPI-12, only Stara Zagora, Plovdiv and Sandanski show a negative trend. In the first two cases the trends are present in every month of the year and annually its magnitude is 0,01 higher than with SPI-3. With the SPI-12 Sandanski has trend in 8 months and in the annual mean SPI12, whereas with the SPI-3 such is not revealed.

Trend line of RYD for rainfed maize (H708), 1951-2004 TAW=116 mm m-1 100 90 80

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70

70

60 50 40

60 50

40

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0 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

a)

0 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

b)

Year

Year

Trend line of NIRs, mm

a) Plovdiv y = 1.5x - 2706

450

400

400

350

350

NIRs, mm

NIRs, mm

b) Stara Zagora

500

500 450

y = 0.14x - 207

90

RYD, %

RYD, %

100

y = 0.35x - 634

300 250

300 250

200

200

150

150

100

100

50

50

0 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

a) Year

y = 0.47x - 667

0 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

b)

Year

Conclusions • • •

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The study relative to eight climate regions, three soil groups and the period 1951-2004 shows that: In soils of large TAW , Plovdiv, NIRs range 0-40 mm in wet years and 350-380 mm in dry years. When TAW is small, NIRs reach 440 mm in the very dry year. NIRs in Sofia and Silistra are 100 mm smaller than in Plovdiv while in Sandanski they are 100 mm larger. Rainfed maize is associated with great yield variability (29%