Cotton production and climatic factors: Studying the nature of its relationship by different statistical methods

Figures & data

Table 1. Range and mean values of the independent variables for the two seasons and over all data

Climatic factor’s	First season^a		Second season^b		Over all data (Two seasons)
	Range	Mean	Range	Mean	Range	Mean
Max. Temp. (°C), (X1)	31.0–44.0	34.3	30.6–38.8	34.1	30.6–44.0	34.2
Min. Temp. (°C), (X2)	18.6–24.5	21.9	18.4–23.9	21.8	18.4–24.5	21.8
Max.–Min. Temp. (°C), (X3)^c	9.4–20.9	12.4	8.5–17.6	12.2	8.5–20.9	12.3
Evap (mm d^−1), (X4)	7.6–15.2	10.0	4.1–9.8	6.0	4.1–15.2	8.0
06:00 h Temp. (°C), (X5)	14.0–21.5	17.8	13.3–22.4	18.0	13.3–22.4	17.9
18:00 h Temp. (°C), (X6)	19.6–27.0	24.0	20.6–27.4	24.2	19.6–27.4	24.1
Sunshine (h d^−1), (X7)	10.3–12.9	11.7	9.7–13.0	11.9	9.7–13.0	11.8
Max. RH (%), (X8)	62–96	85.4	51–84	73.2	51–96	79.6
Min. RH (%), (X9)	11–45	30.8	23–52	39.8	11–52	35.1
Wind speed (m s^−1), (X10)	ND	ND	2.2–7.8	4.6	ND	ND

Note: ND = not determined.

Source: Sawan et al. (2006).

^a Flower and boll stage (68 days, from 23 June to 29 August).

^b Flower and boll stage (62 days, from 29 June to 29 August).

^c Diurnal temperature range.

Figure 1. Daily number of flowers and bolls during the production stage (68 days) in the first season (I) for the Egyptian cotton cultivar Giza 75 (Gossypium barbadense L.) grown in uniform field trial at the experimental farm of the Agricultural Research Centre, Giza (30° N, 31°: 28′ E), Egypt.

Notes: The soil texture was clay loam, with an alluvial substratum, (pH = 8.07). Total water consumptive use during the growing season supplied by surface irrigation was about 6,000 m³ ha⁻¹. No rainfall occurred during the growing season. The sampling size was 261 plants (Sawan et al., 2005).

Figure 2. Daily number of flowers and bolls during the production stage (62 days) in the second season (II) for the Egyptian cotton cultivar Giza 75 (Gossypium barbadense L.) grown in uniform field trial at the experimental farm of the Agricultural Research Centre, Giza (30° N, 31°: 28′ E), Egypt.

Notes: The soil texture was clay loam, with an alluvial substratum, (pH = 8.07). Total water consumptive use during the growing season supplied by surface irrigation was about 6,000 m³ ha⁻¹. No rainfall occurred during the growing season. The sampling size was 358 plants (Sawan et al., 2005).

Table 2. Simple correlation values for the relationships between the independent variables and the studied dependent variable

Independent variables (Climatic factors)	Dependent variable
	First season		Second season		Combined data
	Flower	Boll	Flower	Boll	Flower	Boll
Max. Temp. (°C) (X1)	–0.07	–0.03	–0.42**	–0.42**	–0.27**	–0.26**
Min. Temp. (°C) (X2)	–0.06	–0.07	0.00	0.02	–0.03	–0.02
Max.−Min. Temp. (°C) (X3)	–0.03	–0.01	–0.36**	–0.37**	–0.25**	–0.24**
Evapor (mm d^−1) (X4)	–0.56**	–0.53**	–0.61**	–0.59**	–0.40**	–0.48**
06:00 h Temp. (°C) (X5)	–0.01	–0.06	–0.14	–0.13	–0.09	–0.09
18:00 h Temp. (°C) (X6)	–0.02	–0.16	–0.37**	–0.36**	–0.27**	–0.25**
Sunshine (h d^−1) (X7)	–0.25*	–0.14	–0.37**	–0.36**	–0,31**	–0.25**
Max. RH (%) (X8)	0.40**	0.37**	0.01	0.01	0.04	–0.06
Min. RH (%) (X9)	0.14	0.10	0.45**	0.46**	0.33**	0.39**
Wind speed (m s^−1) (X10)	ND	ND	–0.06	–0.04	ND	ND

Note: ND = not determined.

Source: Sawan et al. (2002).

* Significance level at p < 0.05.

** Significance level at p < 0.01.

Figure 3. Daily boll retention ratio during the production stage (68 days) in the first season (I) for the Egyptian cotton cultivar Giza 75 (Gossypium barbadense L.) grown in uniform field trial at the experimental farm of the Agricultural Research Centre, Giza (30° N, 31°: 28′ E at an altitude 19 m), Egypt.

Notes: The soil texture was clay loam, with an alluvial substratum, (pH = 8.07). Total water consumptive use during the growing season supplied by surface irrigation was about 6,000 m³ ha⁻¹. No rainfall occurred during the growing season. The sampling size was 261 plants (Sawan et al., 2002).

Figure 4. Daily boll retention ratio during the production stage (62 days) in the second (II) for the Egyptian cotton cultivar Giza 75 (Gossypium barbadense L.) grown in uniform field trial at the experimental farm of the Agricultural Research Centre, Giza (30° N, 31°: 28′ E at an altitude 19 m), Egypt.

Notes: The soil texture was clay loam, with an alluvial substratum, (pH = 8.07). Total water consumptive use during the growing season supplied by surface irrigation was about 6,000 m³ ha⁻¹. No rainfall occurred during the growing season. The sampling size was 358 plants (Sawan et al., 2002).

Table 3. Selected factors and their relative contribution to variations of flower and boll production

Selected climatic factors	Flower production			Boll production
	R.C. (%)			R.C. (%)
	First season	Second season	Combined data	First season	Second season	Combined data
Max. Temp. (°C) (X1)	–	5.92	–	–	5.03	–
Evapor (mm d^−1) (X4)	19.08	23.45	16.06	23.04	22.39	22.89
18:00 h Temp. (°C) (X6)	–	–	5.83	–	–	2.52
Sunshine (h d^−1) (X7)	9.43	7.77	8.31	11.65	7.88	5.47
Max. RH (%) (X8)	8.46	–	–	–	–	–
Min. RH (%) (X9)	–	4.37	7.38	–	4.26	4.64
R^2 % for selected factors	36.97	41.47	37.58	34.69	39.56	35.52
R^2 % for factors studied	40.22	45.03	40.73	38.43	42.87	37.90
R^2 % for factors deleted	3.25	3.56	3.15	3.74	3.31	2.38

Notes: R.C. % = Relative contribution of each of the selected independent variables to variations of the dependent variable. R² % = Coefficient of determination in percentage form.

Source: Sawan et al. (2002).

Figure 5. Daily number of flowers and bolls during the production stage (60 days) in the first season (I) for the Egyptian cotton cultivar Giza 75 (Gossypium barbadense L.) grown in uniform field trial at the experimental farm of the Agricultural Research Centre, Giza (30° N, 31°: 28′ E), Egypt.

Notes: The soil texture was clay loam, with an alluvial substratum, (pH = 8.07). Total water consumptive use during the growing season supplied by surface irrigation was about 6,000 m³ ha⁻¹. No rainfall occurred during the growing season. The sampling size was 261 plants (Sawan et al., 1999).

Figure 6. Daily number of flowers and bolls during the production stage (60 days) in the second season (II) for the Egyptian cotton cultivar Giza 75 (Gossypium barbadense L.) grown in uniform field trial at the experimental farm of the Agricultural Research Centre, Giza (30° N, 31°: 28′ E), Egypt.

Notes: The soil texture was clay loam, with an alluvial substratum, (pH = 8.07). Total water consumptive use during the growing season supplied by surface irrigation was about 6,000 m³ ha⁻¹. No rainfall occurred during the growing season. The sampling size was 358 plants (Sawan et al., 1999).

Table 4. Range and mean value of the independent variables (climatic factors) during the four periods of flower and boll production stage

Climatic factors	First period		Second period		Third period		Fourth period
	Range	Mean	Range	Mean	Range	Mean	Range	Mean
First season
Max. Temp. (°C), (X1)	31.0–37.3	33.7	33.0–37.3	34.7	32.4–37.2	34.5	32.0–38.4	33.8
Min. Temp. (°C), (X2)	18.6–23.5	21.4	20.6–23.5	22.3	18.9–24.4	21.6	19.6–23.8	21.8
Max.−Min. (°C), (X3)	9.4–14.8	12.3	9.8–15.6	12.4	9.7–18.3	12.9	9.5–14.6	12.0
Evapor. mm d^−1, (X4)	10.2–15.2	11.7	8.0–13.2	`10.1	7.6–11.2	9.1	7.7–11.1	9.2
06:00 h Temp. (°C), (X5)	14.2–19.9	16.8	15.8–21.5	18.9	13.9–21.1	17.4	15.4–20.8	18.0
18:00 h Temp.(°C), (X6)	22.0–25,2	23.8	22.2–27.0	24.2	19.6–25.6	24.1	21.8–26.0	23.9
Sunshine h d^−1, (X7)	11.4–12.9	12.4	10.4–12.4	11.5	10.5–12.4	11.6	9.9–12.2	11.4
Max. Hum. %, (X8)	62–88	80.7	84–94	88.4	85–96	89.9	76–96	87.4
Min. Hum. %, (X9)	21–37	28.2	22–43	31.4	17–42	29.9	24–45	34.0
Second season
Max. Temp. (°C), (X1)	31.4–38.8	35.5	31.4–35.5	33.4	32.6–37.9	34.4	30.6–34.6	32.8
Min. Temp. (°C), (X2)	20.1–23.4	21.3	19.6–23.1	21.7	18.4–24.3	22.3	18.6–23.9	21.7
Max.−Min. (°C), (X3)	9.4–17.6	14.2	10.1–15.0	11.7	9.6–17.0	12.1	8.5–12.6	11.0
Evapor. mm d^−1, (X4)	5.9–9.8	7.5	5.0–7.0	6.0	4.3–7.1	5.6	4.1–6.1	4.9
06:00 h Temp. (°C), (X5)	15.5–20.4	17.5	15.2–21.4	18.4	12.9–22.4	18.7	13.3–21.0	17.5
18:00 h Temp. (°C), (X6)	22.8–26.5	24.4	22.2–26.5	24.2	22.9–27.4	24.4	20.6–25.8	23.6
Sunshine h d^−1, (X7)	11.2–13.0	12.4	10.9–12.6	11.9	10.6–12.4	11.6	10.3–12.3	11.5
Max.−Hum. %, (X8)	62–83	71.7	51–82	72.8	59–81	74.7	64–84	73.3
Min. Hum. %, (X9)	23–44	33.1	32–50	41.3	29–51	39.9	37–52	44.7
Windspeed m/s, (X10)	2.8–6.8	5.1	3.4–6.6	4.5	2.2–7.8	4.4	3.4–5.8	4.5

Source: Sawan et al. (1999).

Table 5. Significant simple correlation values between the climatic factors and flower, boll production and boll retention ratio due to quarters of production stage

Climatic factors	Flower				Boll				Ratio: Bolls/Flowers (100)
	1st	2nd	3rd	4th	1st	2nd	3rd	4th	1st	2nd	3rd	4th
First season (n by quarter = 15)
Max. Temp. (°C), (X1)	NS	NS	NS	NS	NS	NS	NS	NS	NS	NS	NS	NS.
Min. Temp. (°C), (X2)	0.516*	0.607*	NS	NS	0.561*	0.638**	NS	NS	NS	0.680**	NS	NS
Max.−Min. (°C), (X3)	NS	NS	0.538*	NS	NS	NS	0.494*	NS	0.515*	NS	NS	NS
Evapor. mm d^−1, (X4)	0.512*	−0.598*	NS	0.424***	0.397****	−0.500*	−0.0321****	NS	NS	−0.387****	−0.287****	NS
06:00 h Temp. (°C), (X5)	−0.352****	0.534*	−0.358****	0.301****	0.402****	0.516*	−0.441***	NS	NS	0.440***	NS	−0.292****
18:00 h Temp. (°C), (X6)	NS	NS	NS	NS	NS	NS	NS	NS	NS	NS	NS	NS
Sunshine h d^−1, (X7)	NS	NS	0.346****	NS	NS	NS	NS	0.430***	NS	NS	NS	0.480*
Max. Hum. %, (X8)	−0.316****	−0.260****	0.461***	0.283****	NS	NS	0.410***	NS	0.389****	NS	NS	−0.322****
Min. Hum. %, (X9)	NS	0.309****	−0.436***	NS	NS	0.436***	−0.316***	NS	−0.473***	0.527*	NS	NS
Second season (n by quarter = 15)
Max. Temp. (°C), (X1)	NS	NS	NS	−0.730**	NS	NS	NS	−0.654**	NS	NS	0.407***	NS
Min. Temp. (°C), (X2)	NS	NS	NS	−0.451***	NS	NS	NS	−0.343****	NS	NS	NS	NS
Max.−Min. (°C), (X3)	NS	NS	0.598*	NS	NS	NS	0.536*	NS	0.456***	−0.416***	NS	NS
Evapor. mm d^−1, (X4)	NS	NS	0.640**	NS	NS	NS	0.580*	NS	NS	−0.318****	NS	NS
06:00 h Temp. (°C), (X5)	−0.397****	−0.301****	−0.407***	−0.506*	−0.380****	−0.323****	−0.332****	−0.426***	NS	NS	0.283****	NS
18:00 h Temp. (°C), (X6)	NS	−.0440***	NS	−0.656**	NS	−0.410***	NS	−0.582*	−.0626**	NS	NS	NS
Sunshine h d^−1, (X7)	0.362****	NS	NS	NS	0.340****	0.308****	0.354****	NS	NS	0.409***	NS	NS
Max. Hum. %, (X8)	−0.523*	0.424***	−0.587*	NS	−0530*	0.431***	−0.586*	NS	NS	NS	NS	NS
Min. Hum. %, (X9)	NS	NS	−0.585*	0.639****	NS	NS	−0.517*	0.652**	NS	NS	NS	0.420***

Notes: Wind speed did not show significant effect upon the studied production variables. NS = Means simple correlation coefficient is not significant at the 0.15 alpha level of significance; n = Number of data pairs used in calculation.

Source: Sawan et al. (1999).

* Significant at 5% probability level.

** Significant at 1% probability level.

*** Significant at 10% probability level.

**** Significant at 15% probability level.

Table 6. Significant simple correlation values between the climatic factors and flower, boll production, and boll retention ratio due to quarters periods of production stage for the combined data of the two seasons (n = 30)

Climatic factors	Flower				Boll				Ratio:Bolls/Flowers (100)
	1st	2nd	3rd	4th	1st	2nd	3rd	4th	1st	2nd	3rd	4th
Max. Temp. (°C), (X1)	NS	NS	0.29****	−0.48**	NS	NS	0.38***	−0.47**	0.27****	NS	NS	NS
Min. Temp. (°C), (X2)	NS	NS	−0.35***	NS	NS	NS	−0.28****	NS	NS	NS	NS	NS
Max.−Min. (°C), (X3)	−0.40*	−0.30****	0.59**	−0.36***	NS	−0.48**	0.52**	−0.38***	−0.40*	−0.47**	NS	−0.28****
Evapor. mm d^−1, (X4)	0.78**	NS	0.32***	−0.67**	0.67**	−0.51**	NS	−0.74**	NS	−0.82**	−0.49**	−0.72**
06:00 h Temp. (°C), (X5)	NS	0.27****	−0.43*	−0.31****	NS	NS	−0.37***	−0.37***	NS	NS	NS	NS
18:00 h Temp. (°C), (X6)	NS	NS	NS	−0.42*	NS	NS	NS	−0.37***	NS	NS	NS	NS
Sunshine h d^−1, (X7)	NS	NS	0.38***	NS	NS	NS	0.32***	NS	NS	0.30****	NS	0.27****
Max. Hum. %, (X8)	NS	NS	NS	−0.64**	NS	NS	NS	−0.71**	NS	−0.60**	−0.44*	−0.70**
Min. Hum. %, (X9)	NS	NS	−0.54**	0.69**	−0.32***	0.42*	−0.37***	0.72**	NS	0.72**	0.40*	0.56**
R^2	0.667	0.116	0.496	0.672	0.446	0.335	0.389	0.747	0.219	0.737	0.269	0.615

Source: Sawan et al. (1999).

* Significant at 5% probability level.

** Significant at 1% probability level.

*** Significant at 10% probability level.

**** Significant at 15% probability level.

Table 7. Significant simple correlation values between the climatic factors and flower, boll production and boll retention ratio for combined data of the two seasons (n = 120)

Climatic factors	Flower	Boll	Ratio
Max. Temp. (°C), (X1)	−0.152***	NS	NS
Min. Temp. (°C), (X2)	NS	NS	NS
Max.−Min. (°C), (X3)	−0.259**	−0.254**	NS
Evapor mm d^−1, (X4)	−0.327**	−0.429**	−0.562**
06:00 h Temp. (°C), (X5)	NS	NS	NS
18:00 h Temp. (°C), (X6)	−0.204*	−0.190***	NS
Sunshine h d^−1, (X7)	−0.227*	−0.180***	NS
Max. Hum. %, (X8)	NS	NS	−0.344**.
Min. Hum. %, (X9)	0.303**	0.364**	0.335**
R^2	0.406**	0.422**	0.336*

Source: Sawan et al. (1999).

* Significant at 5% probability level.

** Significant at 1% probability level.

*** Significant at 10% probability level.

Table 8. Significant simple correlation coefficient values between the production variables and the studied climatic factors for the daily and different intervals of days combined over both seasons

Daily and intervals of days	Production variables	Climatic factors^a
		Air Temp. (°C)			Evap (mm d^−1)	Surface soil Temp.(°C)		Sunshine duration (h d^−1)	Relative humidity (%)
		Max. (X1)	Min. (X2)	Max.−Min. (X3)	(X4)	06:00 h (X5)	18:00 h (X6)	(X7)	Max. (X8)	Min. (X9)
Daily (n = 120)	Flower	−0.15***	NS	−0.26**	−0.33**	NS	−0.20*	−0.23*	NS	0.30**
	Boll	NS	NS	−0.25**	−0.43**	NS	−0.19***	−0.18***	NS	0.36**
	Boll ret. rat.	NS	NS	NS	−0.56**	NS	NS	NS	NS	0.34**
2 Days (n = 60)	Flower	−0.31***	NS	−0.32*	−0.36**	NS	−0.24****	−0.36**	NS	0.37**
	Boll	−0.29***	NS	−0.30***	−0.46**	NS	−0.21****	−0.31*	NS	0.44**
	Boll ret. rat.	NS	NS	NS	−0.61**	NS	NS	NS	NS	0.40**
3 Days (n = 40)	Flower	−0.34*	NS	−0.34*	−0.33*	NS	−0.28***	−0.39*	NS	0.34*
	Boll	−0.32*	NS	−0.32*	−0.48**	NS	−0.24****	−0.36*	NS	0.45**
	Boll ret. rat.	NS	NS	NS	−0.63**	NS	NS	NS	NS	0.40*
4 Days (n = 30)	Flower	−0.31***	NS	−0.35***	−0.33***	NS	−0.28****	−0.39*	NS	0.34***
	Boll	−0.31***	NS	−0.33***	−0.48**	NS	−0.23****	−0.38*	NS	0.45*
	Boll ret. rat.	NS	NS	NS	−0.64**	NS	NS	NS	NS	0.42*
5 Days (n = 24)	Flower	−0.35***	NS	−0.37***	−0.39***	NS	−0.39***	−0.52**	NS	0.41*
	Boll	−0.33****	NS	−0.35***	−0.49*	NS	−0.35***	−0.44*	NS	0.47**
	Boll ret. rat.	NS	NS	NS	−0.66**	NS	NS	NS	NS	0.43*
6 Days (n = 20)	Flower	−0.37***	NS	−0.41***	−0.38***	NS	NS	−0.54**	NS	0.42*
	Boll	−0.37***	NS	−0.40***	−0.49*	NS	NS	−0.46*	NS	0.49*
	Boll ret. rat.	NS	NS	NS	−0.69**	NS	NS	NS	NS	0.45*
10 Days (n = 12)	Flower	NS	NS	−0.45***	−0.40****	NS	−0.55*	−0.65*	NS	0.43***
	Boll	NS	NS	−0.43***	−0.51***	NS	−0.53***	−0.57*	NS	0.51***
	Boll ret. rat.	NS	NS	NS	−0.74**	NS	NS	NS	NS	0.55*

Notes: NS = Simple correlation coefficient is not significant at the 15% probability level; n = Number of data pairs used in calculation.

Source: Sawan et al. (2006).

^a Wind speed did not show significant effect upon the studied production variables, so is not reported.

* Significant at 5% probability level.

** Significant at 1% probability level.

*** Significant at 10% probability level.

**** Significant at 15% probability level.

Table 9. The equations obtained for each of the studied cotton production variables for the five-day intervals and daily intervals combined over both seasons

Equation^a	R^2	Significance
Five-day intervals
Y1 = 23.78 − 0.5362X4 − 0.1429X6 − 0.1654X7 + 0.0613X9	0.6237	**
Y2 = 15.89 − 0.4762X4 − 0.1583X6 − 0.1141X7 + 0.0634X9	0.5945	**
Y3 = 72.65 − 0.0833X4 − 0.1647X6 + 0.2278X9	0.6126	**
Daily intervals
Y1 = 19.78 − 0.181X3 − 0.069X4 − 0.164X6 − 0.182X7 + 0.010X9	0.4117	**
Y2 = 14.96 − 0.173X3 − 0.075X4 − 0.176X6 − 0.129X7 + 0.098X9	0.4461	**
Y3 = 52.36 − 3.601X4 − 0.2352X7 + 4.511X9	0.3587	**

Source: Sawan et al. (2006).

^a Where Y₁ = number of flowers per plant, Y₂ = number of bolls per plant, Y₃ = boll retention ratio, X₃ = maximum − minimum temperature (°C), X₄₌evaporation mm day⁻¹, X₆ = surface soil temperature (°C) at 18:00 h., X₇ = sunshine duration h day⁻¹, and X₉ = minimum relative humidity %.

^** All entries significant at 1% level.

Table 10. Mean, standard deviation, maximum and minimum values of the climatic factors during the flower and boll stage (initial time) and the 15 days prior to flowering or subsequent to boll setting for I and II season at Giza, Egypt

Climatic factors	First season^a				Second season^b
	Mean	SD	Max.	Min.	Mean	SD	Max.	Min.
Max. Temp. (°C) (X1)	34.1	1.2	44.0	31.0	33.8	1.2	38.8	30.6
Min. Temp. (°C) (X2)	21.5	1.0	24.5	18.6	21.4	0.9	24.3	18.4
Max.−Min. Temp. (°C) (X3)^c	12.6	1.1	20.9	9.4	12.4	1.3	17.6	8.5
Evapor (mm d^−1) (X4)	10.6	1.6	16.4	7.6	6.0	0.7	9.8	4.1
06:00 h Temp. (°C) (X5)	17.5	1.1	21.5	13.9	17.6	1.2	22.4	13.3
18:00 h Temp. (°C) (X6)	24.2	1.9	32.3	19.6	23.7	1.1	27.4	20.6
Sunshine (h d^−1) (X7)	11.7	0.8	12.9	9.9	11.7	0.4	13.0	10.3
Max. Hum. (%) (X8)	85.6	3.3	96.0	62.0	72.9	3.8	84.0	51.0
Min. Hum. (%) (X9)	30.2	5.2	45.0	11.0	39.1	5.0	52.0	23.0
Wind speed (m s^−1) (X10)	ND	ND	ND	ND	4.6	0.9	7.8	2.2

Note: ND = not determined.

Source: Sawan et al. (2005).

^a Flower and boll stage (68 days, from 23 June to 29 August).

^b Flower and boll stage (62 days, from 29 June to 29 August).

^c Diurnal temperature range.

Table

File	Data of any dependent variable (for each flowers and bolls)		Any independent variable (for each climatic factors)
	Production stage		In case of original file and files before production stage		In case of original file and files after production stage
	Date	Days	Date	Days	Date	Days
Original file	23 June–29 August	68	23 June–29 August	68	23 June–29 August	68
1st new file	23 June–29 August	68	22 June–28 August	68	24 June–30 August	68
2nd new file	23 June–29 August	68	21 June–27 August	68	25 June–31 August	68
15th new file	23 June–29 August	68	8 June–14 August	68	8 July−13 September	68

Table 11. Simple correlation coefficients (r) between climatic factors and number of flower and harvested bolls in initial time (0) and each of the 15-day periods before flowering in the first season (I)

Climate period		Air Temp. (°C)			Evap (mm d^−1)	Surface soil Temp. (°C)		Sunshine duration (h d^−1)	Humidity (%)
		Max. (X1)	Min. (X2)	Max.−Min. (X3)^a	(X4)	06:00 h (X5)	18:00 h (X6)	(X7)	Max. (X8)	Min. (X9)
0	Flower	−0.07	−0.06	−0.03	−0.56**	−0.01	−0.20	−0.25*	0.40**	0.14
	Boll	−0.03	−0.07	−0.01	−0.53**	−0.06	−0.16	−0.14	0.37**	0.10
1	Flower	−0.15	−0.08	−0.11	−0.64**	−0.01	−0.17	−0.30*	0.39**	0.20
	Boll	−0.07	−0.08	−0.02	−0.58**	−0.06	−0.10	−0.23*	0.36**	0.13
2	Flower	−0.26*	−0.10	−0.22	−0.69**	−0.07	−0.30*	−0.35**	0.42**	0.30*
	Boll	−0.18	−0.08	−0.14	−0.64**	−0.05	−0.21	−0.25*	0.40**	0.20
3	Flower	−0.28*	−0.02	−0.31**	−0.72**	0.15	−0.29*	−0.37**	0.46**	0.35**
	Boll	−0.19	−0.02	−0.21	−0.65**	0.11	−0.20	−0.30*	0.37**	0.25*
4	Flower	−0.26*	−0.03	−0.26*	−0.67**	0.08	−0.24*	−0.41**	0.46**	0.35**
	Boll	−0.21	−0.04	−0.21	−0.63**	0.04	−0.18	−0.35**	0.39**	0.29*
5	Flower	−0.27*	−0.02	−0.27*	−0.68**	0.16	−0.29*	−0.45**	0.49**	0.38**
	Boll	−0.22	0.00	−0.24*	−0.63**	0.16	−0.21	−0.39**	0.44**	0.32**
6	Flower	−0.21	0.05	−0.25*	−0.73**	0.16	−0.28*	−0.46**	0.47**	0.42**
	Boll	−0.15	0.08	−0.21	−0.67**	0.19	−0.19	−0.46**	0.43**	0.35**
7	Flower	−0.17	−0.01	−0.17	−0.69**	0.10	−0.27*	−0.43**	0.46**	0.35**
	Boll	−0.11	−0.06	−0.15	−0.64**	0.14	−0.19	−0.46**	0.43**	0.32**
8	Flower	−0.24*	−0.03	−0.24*	−0.71**	0.09	−0.30*	−0.44**	0.45**	0.45**
	Boll	−0.14	0.04	−0.17	−0.63**	0.16	−0.17	−0.48**	0.44**	0.39**
9	Flower	−0.23	−0.10	−0.19	−0.68**	0.05	−0.33**	−0.32**	0.43**	0.44**
	Boll	−0.14	0.04	−0.17	−0.61**	0.15	−0.21	−0.40**	0.42**	0.41**
10	Flower	−0.26*	0.05	−0.30*	−0.67**	0.13	−0.29*	−0.29*	0.40**	0.48**
	Boll	−0.14	0.13	−0.22	−0.58**	0.22	−0.17	−0.36**	0.46**	0.41**
11	Flower	−0.20	0.10	−0.27*	−0.62**	0.21	−0.19	−0.29*	0.42**	0.44**
	Boll	−0.04	0.22	−0.16	−0.53**	0.27*	−0.04	−0.38**	0.45**	0.36**
12	Flower	−0.17	0.16	−0.26*	−0.62**	0.29*	−0.15	−0.40**	0.44**	0.45**
	Boll	0.00	0.25*	−0.13	−0.51**	0.35**	−0.04	−0.45**	0.40**	0.30*
13	Flower	−0.13	0.16	−0.22	−0.62**	0.23	−0.12	−0.42**	0.43**	0.45**
	Boll	0.00	0.22	−0.11	−0.51**	0.30*	−0.03	−0.49**	0.41**	0.33**
14	Flower	−0.08	0.18	−0.18	−0.56**	0.21	−0.15	−0.44**	0.41**	0.46**
	Boll	0.01	0.21	−0.10	−0.47**	0.26*	−0.09	−0.49**	0.42**	0.33**
15	Flower	−0.08	0.22	−0.21	−0.51**	0.24*	−0.22	−0.42**	0.39**	0.38**
	Boll	−0.03	0.19	−0.13	−0.45**	0.24*	−0.17	−0.44**	0.43**	0.30*

Note: 0 = Initial time.

Source: Sawan et al. (2005).

^a Diurnal temperature range.

* Significant at 5% level.

** Significant at 1% level.

Table 12. Simple correlation coefficients (r) between climatic factors^a and number of flower and harvested bolls in initial time (0) and each of the 15-day periods before flowering in the second season (II)

Climate period		Air Temp. (°C)			Evap (mm d^−1)	Surface soil Temp. (°C)		Sunshine duration (h d^−1)	Humidity (%)
		Max. (X1)	Min. (X2)	Max.−Min. (X3)^b	(X4)	06:00 h (X5)	18:00 h (X6)	(X7)	Max. (X8)	Min. (X9)
0	Flower	−0.42**	0.00	−0.36**	−0.61**	−0.14	−0.37**	−0.37**	0.01	0.45**
	Boll	−0.42**	0.02	−0.37**	−0.59**	−0.13	−0.36**	−0.36**	0.01	0.46**
1	Flower	−0.42**	0.10	−0.42**	−0.63**	−0.08	−0.29*	−0.41**	0.05	0.48**
	Boll	−0.41**	0.11	−0.42**	−0.62**	−0.07	−0.28*	−0.41**	0.05	0.47**
2	Flower	−0.40**	0.08	−0.43**	−0.65**	−0.09	−0.27*	−0.39**	0.02	0.49**
	Boll	−0.40**	0.08	−0.43**	−0.64**	−0.08	−0.26*	−0.40**	0.03	0.49**
3	Flower	−0.38**	0.13	−0.43**	−0.61**	−0.06	−0.17	−0.38**	0.00	0.45**
	Boll	−0.37**	0.15	−0.44**	−0.61**	−0.05	−0.15	−0.38**	0.01	0.46**
4	Flower	−0.36**	0.17	−0.41**	−0.61**	−0.04	−0.18	−0.38**	0.02	0.45**
	Boll	−0.35**	0.18	−0.41**	−0.60**	−0.03	−0.16	−0.36**	0.03	0.44**
5	Flower	−0.30*	0.13	−0.36**	−0.60**	−0.07	−0.23	−0.32**	−0.05	0.43**
	Boll	−0.28*	0.15	−0.35**	−0.58**	−0.05	−0.21	−0.31**	−0.05	0.41**
6	Flower	−0.24	0.21	−0.38**	−0.61**	−0.02	−0.12	−0.28*	0.02	0.40**
	Boll	−0.22	0.24	−0.38**	−0.59**	0.00	−0.07	−0.29*	0.02	0.40**
7	Flower	−0.19	0.23	−0.29*	−0.54**	−0.03	−0.05	−0.26*	−0.04	0.32**
	Boll	−0.18	0.23	−0.27*	−0.53**	−0.02	−0.03	−0.27*	−0.04	0.30*
8	Flower	−0.15	0.24	−0.25*	−0.52**	−0.03	−0.07	−0.24*	−0.05	0.28*
	Boll	−0.14	0.22	−0.22	−0.51**	−0.03	−0.06	−0.22*	−0.05	0.26*
9	Flower	−0.16	0.34**	−0.32**	−0.56**	0.08	−0.02	−0.25*	0.05	0.30*
	Boll	−0.14	0.34**	−0.31**	−0.56**	0.09	−0.01	−0.23*	0.07	0.29*
10	Flower	−0.16	0.31**	−0.30*	−0.56**	0.11	−0.06	−0.27*	0.11	0.33**
	Boll	−0.14	0.28*	−0.27*	−0.55**	0.09	−0.07	−0.25*	0.09	0.31**
11	Flower	−0.16	0.31**	−0.27*	−0.55**	0.10	−0.02	−0.31**	0.08	0.32**
	Boll	−0.15	0.29*	−0.26*	−0.53**	0.10	0.00	−0.29*	0.08	0.29*
12	Flower	−0.17	0.44**	−0.37**	−0.57**	0.26*	0.02	−0.36**	0.17	0.34**
	Boll	−0.17	0.42**	−0.36**	−0.55**	0.25*	0.01	−0.34**	0.16	0.32**
13	Flower	−0.14	0.40**	−0.33**	−0.56**	0.21	0.03	−0.28*	0.10	0.34**
	Boll	−0.15	0.38**	−0.34**	−0.56**	0.21	0.01	−0.27*	0.09	0.33**
14	Flower	−0.19	0.39**	−0.38**	−0.59**	0.25*	0.04	−0.34**	0.16	0.35**
	Boll	−0.20	0.39**	−0.40**	−0.59**	0.26*	0.03	−0.36**	0.17	0.36**
15	Flower	−0.24	0.49**	−0.45**	−0.62**	0.37**	0.16	−0.38**	0.27*	0.42**
	Boll	−0.24	0.51**	−0.48**	−0.63**	0.40**	0.15	−0.40**	0.26*	0.43**

Note: 0 = Initial time.

Source: Sawan et al. (2005).

^a Wind speed did not show significant effect upon the studied production variables, so it is not reported.

^b Diurnal temperature range.

* Significant at 5% level.

** Significant at 1% level.

Table 13. Simple correlation coefficient (r) values between climatic factors and number of harvested bolls and retention ratio in initial time (0) and each of the 15-day periods after flowering in the first season (I).

Climate period		Air Temp. (°C)			Evap (mm d^−1)	Surface soil Temp. (°C)		Sunshine duration (h d^−1)	Humidity (%)
		Max. (X1)	Min. (X2)	Max.−Min. (X3)^a	(X4)	06:00 h (X5)	18:00 h (X6)	(X7)	Max. (X8)	Min. (X9)
0	Retention ratio	−0.05	−0.03	−0.03	−0.10	−0.11	0.10	0.20	−0.04	−0.02
	No. of bolls	−0.03	−0.07	−0.01	−0.53**	−0.06	−0.16	−0.14	0.37**	0.10
1	Retention ratio	−0.07	−0.08	−0.01	−0.10	−0.16	0.04	0.15	0.04	0.05
	No. of bolls	0.02	−0.08	0.08	−0.49**	−0.09	−0.05	−0.20	0.35**	0.09
2	Retention ratio	−0.08	−0.14	0.02	−0.08	−0.19	0.03	0.17	0.02	−0.02
	No. of bolls	0.02	−0.04	0.07	−0.46**	−0.06	−0.01	−0.19	0.33**	0.09
3	Retention ratio	−0.09	−0.21	0.06	−0.08	−0.24*	0.02	0.19	0.01	−0.10
	No. of bolls	0.03	−0.03	0.06	−0.44**	−0.04	0.05	−0.18	0.32**	0.08
4	Retention ratio	−0.05	−0.20	0.09	−0.01	−0.24*	0.01	0.22	0.00	−0.15
	No. of bolls	0.01	−0.05	0.05	−0.40**	−0.03	0.04	−0.16	0.31*	0.08
5	Retention ratio	−0.03	−0.21	0.13	0.07	−0.25*	0.00	0.26*	−0.02	−0.22
	No. of bolls	0.00	−0.07	0.05	−0.37**	−0.02	0.03	−0.13	0.29*	0.07
6	Retention ratio	0.01	−0.19	0.15	0.12	−0.24*	0.02	0.27*	−0.03	−0.20
	No. of bolls	−0.01	−0.08	0.04	−0.38**	−0.02	0.04	−0.15	0.31*	0.13
7	Retention ratio	0.05	−0.17	0.17	0.18	−0.25*	0.05	0.29*	−0.02	−0.21
	No. of bolls	−0.03	−0.09	0.03	−0.39**	−0.04	0.06	−0.14	0.34**	0.18
8	Retention ratio	0.06	−0.08	0.13	0.21	−0.20	0.07	0.28*	−0.06	−0.19
	No. of bolls	−0.05	−0.07	−0.01	−0.35**	−0.02	0.02	−0.17	0.28*	0.17
9	Retention ratio	0.08	0.00	0.08	0.26*	−0.14	0.08	0.29*	−0.12	−0.20
	No. of bolls	−0.08	−0.06	−0.05	−0.33**	−0.01	0.00	−0.23	0.20	0.16
10	Retention ratio	0.06	−0.02	0.05	0.27*	−0.13	0.09	0.27*	−0.10	−0.08
	No. of bolls	−0.11	−0.10	−0.07	−0.34**	−0.03	−0.03	−0.19	0.18	0.21
11	Retention ratio	0.04	−0.04	0.08	0.28*	−0.12	0.08	0.26*	−0.09	−0.05
	No. of bolls	−0.18	−0.18	−0.06	−0.37**	−0.10	−0.04	−0.14	0.15	0.28*
12	Retention ratio	0.02	0.01	−0.08	0.32**	−0.05	0.05	0.25*	−0.08	−0.03
	No. of bolls	−0.17	−0.13	−0.08	−0.32**	−0.06	−0.07	−0.11	0.16	0.24*
13	Retention ratio	−0.04	0.04	−0.09	0.38**	0.00	0.01	0.27*	−0.09	−0.02
	No. of bolls	−0.15	−0.09	−0.09	−0.29*	−0.03	−0.10	−0.08	0.18	0.20
14	Retention ratio	−0.07	0.04	−0.13	0.34**	0.06	−0.02	0.18	−0.08	−0.01
	No. of bolls	−0.15	−0.10	−0.10	−0.28*	−0.01	−0.10	−0.15	0.17	0.17
15	Retention ratio	−0.13	0.03	−0.18	0.33**	0.09	−0.04	0.06	−0.07	0.00
	No. of bolls	−0.16	−0.10	−0.11	−0.28*	0.00	−0.11	−0.13	0.17	0.15

Notes: 0 = Initial time; Retention ratio = (the number of retained bolls obtained from the total number of each daily tagged flowers in all selected plants at harvest/each daily number of tagged flowers in all selected plants) x 100.

Source: Sawan et al. (2005).

^a Diurnal temperature range.

* Levels of significance at 5%.

** Levels of significance at 1%.

Table 14. Simple correlation coefficient (r) values between climatic factors^a and number of harvested bolls and retention ratio in initial time (0) and each of the 15-day periods after flowering in the second season (II)

Climate period		Air Temp. (°C)			Evap (mm d^−1)	Surface soil Temp. (°C)		Sunshine duration (h d^−1)	Humidity (%)
		Max. (X1)	Min. (X2)	Max.−Min. (X3)^b	(X4)	06:00 h (X5)	18:00 h (X6)	(X7)	Max. (X8)	Min. (X9)
0	Retention ratio	−0.04	0.20	−0.31*	−0.14	0.12	−0.20	0.01	−0.04	0.17
	No. of bolls	−0.42**	0.02	−0.37**	−0.59**	−0.13	−0.36**	−0.36**	0.01	0.46**
1	Retention ratio	−0.10	−0.03	−0.22	−0.21	−0.15	−0.05	−0.04	−0.02	0.23
	No. of bolls	−0.25*	−0.01	−0.36**	−0.63**	−0.15	−0.30*	−0.25*	0.06	0.44**
2	Retention ratio	−0.15	−0.06	−0.10	−0.15	−0.08	−0.21	−0.01	−0.04	0.12
	No. of bolls	−0.18	−0.01	−0.34**	−0.65**	−0.11	−0.25*	−0.32*	0.13	0.43**
3	Retention ratio	−0.03	−0.01	−0.02	−0.21	−0.01	−0.17	−0.08	0.09	0.12
	No. of bolls	−0.15	−0.06	−0.30*	−0.62**	−0.05	−0.28*	−0.31*	0.14	0.33**
4	Retention ratio	0.08	−0.02	0.07	−0.09	−0.03	−0.09	−0.10	0.05	−0.04
	No. of bolls	−0.15	−0.05	−0.28*	−0.63**	−0.06	−0.25*	−0.33**	0.15	0.32*
5	Retention ratio	0.23	−0.03	0.12	−0.06	−0.06	−0.01	−0.11	0.01	−0.16
	No. of bolls	−0.14	−0.05	−0.25*	−0.62**	−0.06	−0.24*	−0.35**	0.15	0.31*
6	Retention ratio	0.09	−0.08	0.12	−0.09	−0.07	−0.01	−0.09	0.00	−0.05
	No. of bolls	−0.15	−0.04	−0.22	−0.61**	−0.08	−0.25*	−0.34**	0.13	0.22
7	Retention ratio	−0.03	−0.12	0.12	−0.10	−0.11	−0.01	−0.04	−0.03	0.02
	No. of bolls	−0.15	−0.02	−0.19	−0.60**	−0.10	−0.29*	−0.32*	0.10	0.18
8	Retention ratio	−0.02	0.05	0.03	−0.10	−0.04	−0.03	−0.02	−0.01	0.01
	No. of bolls	−0.20	−0.03	−0.23	−0.61**	−0.10	−0.28*	−0.32*	0.19	0.22
9	Retention ratio	−0.02	0.13	−0.05	−0.10	0.08	−0.05	−0.01	0.03	0.00
	No. of bolls	−0.24	−0.04	−0.29*	−0.62**	−0.11	−0.30*	−0.33**	0.13	0.27*
10	Retention ratio	−0.04	0.12	−0.08	−0.09	0.05	0.11	−0.02	0.04	0.02
	No. of bolls	−0.27*	−0.07	−0.30*	−0.60**	−0.16	−0.34**	−0.34**	0.11	0.26*
11	Retention ratio	−0.07	0.10	−0.10	−0.08	0.03	0.20	−0.03	0.05	0.04
	No. of bolls	−0.30*	−0.12	−0.30*	−0.61**	−0.18	−0.39**	−0.36**	0.10	0.27*
12	Retention ratio	−0.11	0.09	−0.14	−0.11	0.04	0.13	−0.08	0.11	0.09
	No. of bolls	−0.32*	−0.19	−0.26*	−0.60**	−0.22	−0.42**	−0.37**	0.09	0.27*
13	Retention ratio	−0.14	0.09	−0.17	−0.18	0.06	−0.06	−0.14	0.16	0.12
	No. of bolls	−0.33**	−0.26*	−0.23	−0.59**	−0.28*	−0.48**	−0.39**	0.08	0.27*
14	Retention ratio	−0.11	−0.04	−0.10	−0.13	−0.15	−0.05	−0.09	0.01	0.12
	No. of bolls	−0.34**	−0.32*	−0.21	−0.61**	−0.32*	−0.48**	−0.38**	0.06	0.27*
15	Retention ratio	−0.08	−0.11	0.02	−0.08	−0.22	−0.05	−0.02	−0.03	0.12
	No. of bolls	−0.35**	−0.37**	−0.18	−0.61**	−0.38**	−0.48**	−0.37**	0.03	0.27*

Notes: 0 = Initial time; Retention ratio = (the number of retained bolls obtained from the total number of each daily tagged flowers in all selected plants at harvest/each daily number of tagged flowers in all selected plants) x 100.

Source: Sawan et al. (2005).

^a Wind speed did not show significant effect upon the studied production variables, so it is not reported.

^b Diurnal temperature range.

* Level of significance at 5%.

** Level of significance at 1%.

Table 15. The models obtained for the number of flowers and bolls per plant as functions of the climatic data derived from the 5, 10, and 15 day periods prior to flower opening in the two seasons (I, II)

Season	Model^a	R^2	Significance
First	Flower
	Y1 = 55.75 + 0.86X3 − 2.09X4 − 2.23X7	0.51	**
	Y2 = 26.76 − 5.45X4 + 1.76X9	0.42	**
	Y3 = 43.37 − 1.02X4 − 2.61X7 + 0.20X8	0.52	**
	Boll
	Y1 = 43.69 + 0.34X3 − 1.71X4 − 1.44X7	0.43	**
	Y2 = 40.11 − 1.82X4 − 1.36X7 + 0.10X8	0.48	**
	Y3 = 31.00 − 0.60X4 − 2.62X7 + 0.23X8	0.47	**
Second	Flower
	Y1 = 18.58 + 0.39X3 − 0.22X4 − 1.19X7 + 0.17X9	0.54	**
	Y2 = 16.21 + 0.63X3 − 0.20X4 − 1.24X7 + 0.16X9	0.61	**
	Y3 = 14.72 + 0.51X3 − 0.20X4 − 0.85X7 + 0.17X9	0.58	**
	Boll
	Y1 = 25.83 + 0.50X3 − 0.26X4 − 1.95X7 + 0.15X9	0.61	**
	Y2 = 19.65 + 0.62X3 − 0.25X4 − 1.44X7 + 0.12X9	0.60	**
	Y3 = 15.83 + 0.60X3 − 0.22X4 − 1.26X7 + 0.14X9	0.59	**

Source: Sawan et al. (2005).

^a Where Y₁, Y₂, Y₃ = number of flowers or bolls per plant at the 5, 10 and 15 day periods before flowering, respectively, X₂ = minimum temperature (°C), X₃ = diurnal temperature range (°C), X₄ = evaporation (mm day⁻¹), X₇ = sunshine duration (h day⁻¹), X₈ = maximum humidity (%) and X₉ = minimum humidity (%).

** All entries significant at 1% level.

Table 16. The models obtained for the number of bolls per plant as functions of the climatic data derived from the 5, 10, and 15 day periods after flower opening in the two seasons (I, II)

Season	Model^a	R^2	Significance
First	Y1 = 16.38 − 0.41X4	0.14	**
	Y2 = 16.43 − 0.41X4	0.14	**
	Y3 = 27.83 − 0.60X4 − 0.88X9	0.15	**
Second	Y1 = 23.96 − 0.47X4 − 0.77X8	0.44	**
	Y2 = 18.72 − 0.58X4	0.34	**
	Y3 = 56.09 − 2.51X4 − 0.49X6 − 1.67X7	0.56	**

Source: Sawan et al. (2005).

^a Where Y₁, Y₂, Y₃ = number of bolls per plant at the 5, 10, and 15 day periods after flowering, respectively, X₄ = evaporation (mm day⁻¹), X₆ = soil surface temperature (°C) at 18:00, X₇ = sunshine duration (h day⁻¹), X₈ = maximum humidity (%) and X₉ = minimum humidity (%).

** All entries significant at 1% level.

Table 17. Simple correlation coefficient (r) values between the independent variables and the dependent variables in the first season (I)

Independent variables (Irrigation and climatic factors)	Dependent variables (First season)
	Flowers	Bolls
(X1) Irrigation on day 1	−0.1282	−0.0925
(X2) Irrigation on day 0 or −1 (1st and 2nd day after irrigation)	−0.1644	−0.1403
(X3) 1 is for the day prior to irrigation	−0.0891	−0.0897
(X4) Number of days that temperature equaled or exceeded 37.5°C	0.1258	0.1525
(X5) Range of temperature (°C) on day 1	−0.0270	−0.0205
(X6) Broadest range of temperature (°C) over days 1 −12	0.0550	0.1788^d
(X7) MinRH (%) during day 1	0.1492	0.1167
(X8) MaxRH (%) during day 1	0.2087^c	0.1531
(X9) MinRH (%) during day 2	0.1079	0.1033
(X10) MaxRH (%) during day 2	0.1127	0.0455
(X11) Largest maxRH (%) on days 3–6	0.3905^a	0.2819^b
(X12) Lowest minRH (%) on days 3–6	0.0646	0.0444
(X13) Largest maxRH (%) on days 7–12	0.4499^a	0.3554^b
(X14) Lowest minRH (%) on days 7–12	0.3522^a	0.1937^d
(X15) Lowest minRH (%) on days 50–52	−0.3440^a	−0.4222^a
(X16) Daily light period (hour)	−0.2430^b	−0.1426

Source: Sawan et al. (2010).

^a Significant at 1% probability level.

^b Significant at 5% probability level.

^c Significant at 10% probability level.

^d Significant at 15% probability level.

Table 18. Simple correlation coefficient (r) values between the independent variables and the dependent variables in the second season (II).

Independent variables (Irrigation and climatic factors)	Dependent variables (Second season)
	Flowers	Bolls
(X1) Irrigation on day 1	−0.0536	−0.0467
(X2) Irrigation on day 0 or −1	−0.1116	−0.1208
(X3) 1 is for the day prior to the day of irrigation	−0.0929	−0.0927
(X4) Number of days that temperature equaled or exceeded 37.5°C	−0.4192^a	−0.3981^a
(X5) Range of temperature (°C) on day 1	−0.3779^a	−0.3858^a
(X6) Broadest range of temperature (°C) over days 1–12	−0.3849^a	−0.3841^a
(X7) MinRH (%) during day 1	0.4522^a	0.4665^a
(X8) MaxRH (%) during day 1	0.0083	0.0054
(X9) MinRH (%) during day 2	0.4315^a	0.4374^a
(X10) MaxRH (%) during day 2	0.0605	0.0532
(X11) Largest maxRH (%) on days 3–6	0.2486^c	0.2520^b
(X12) Lowest minRH (%) on days 3–6	0.5783^a	0.5677^a
(X13) Largest maxRH (%) on days 7–12	0.0617	0.0735
(X14) Lowest minRH (%) on days 7–12	0.4887^a	0.4691^a
(X15) Lowest minRH (%) on days 50–52	−0.6246^a	−0.6113^a
(X16) Daily light period (hour)	−0.3677^a	−0.3609^a

Source: Sawan et al. (2010).

^a Significant at 1% probability level.

^b Significant at 5% probability level.

^c Significant at 10% probability level.

Table 19. Simple correlation coefficient (r) values between the independent variables and dependent variables in the combined two seasons (I and II)

Independent variables (Irrigation and climatic factors)	Dependent variables (Combined two seasons)
	Flowers	Bolls
(X1) Irrigation on day 1	−0.0718	−0.0483
(X2) Irrigation on day 0 or −1	−0.1214	−0.1108
(X3) 1 is for the day prior to the day of irrigation	−0.0845	−0.0769
(X4) Number of days that temperature equaled or exceeded 37.5°C	−0.2234^b	−0.1720^c
(X5) Range of temperature (°C) on day 1	−0.2551^a	−0.2479^a
(X6) Broadest range of temperature (°C) over days 1–12	−0.2372^a	−0.1958^b
(X7) MinRH (%) during day 1	0.3369^a	0.3934^a
(X8) MaxRH (%) during day 1	0.0032	−0.0911
(X9) MinRH (%) during day 2	0.3147^a	0.3815^a
(X10) MaxRH(%) during day 2	−0.0094	−0.1113
(X11) Largest maxRH (%) on days 3–6	0.0606	−0.0663
(X12) Lowest minRH (%) on days 3–6	0.3849^a	0.4347^a
(X13) Largest maxRH (%) on days 7–12	−0.0169	−0.1442^d
(X14) Lowest minRH (%) on days 7–12	0.3891^a	0.4219^a
(X15) Lowest minRH (%) on days 50–52	−0.3035^a	−0.2359^a
(X16) Daily light period (hour)	−0.3039^a	−0.2535^a

Source: Sawan et al. (2010).

^a Significant at 1% probability level.

^b Significant at 5% probability level.

^c Significant at 10% probability level.

^d Significant at 15% probability level.

Table 20. Model obtained for cotton production variables as functions of climatic data and soil moisture status in individual and combined seasons

Season	Model	R^2
Season I (n = 68)	Y1 = −557.54 + 6.35X6 + 0.65X7 + 1.92X11 + 4.17X13 + 2.88X14 − 1.90X15 − 5.63X16	0.63
	Y2 = −453.93 + 6.53X6 + 0.61X7 + 1.80X11 + 2.47X13 + 1.87X14 − 1.85X15	0.53
Season II (n = 62)	Y1 = −129.45 + 25.36X1 + 37.02X4 + 1.48X7 + 1.69X9 + 4.46X12 + 2.55X14 − 4.73X15	0.72
	Y2 = −130.23 + 24.27X1 + 35.66X4 + 1.42X7 + 1.61X9 + 4.00X12 + 2.18X14 − 4.09X15	0.71
Combined data: I & II (n = 130)	Y1 = −557.36 + 6.82X6 + 1.44X7 + 0.75X9 + 2.04X11 + 2.55X12 + 2.01X13 + 3.27X14 − 2.15X15	0.57
	Y2 = −322.17 + 6.41X6 + 1.20X7 + 0.69X9 + 1.81X11 + 2.12X12 + 2.35X14 − 2.16X15	0.53

Notes: (Y1) Number of cotton flowers; (Y2) Number of cotton bolls; (X₁) Irrigation on day 1; (X₄) Number of that temperature equaled or exceeded 37.5°C; (X₆) Broadest range of temperature (°C) over days 1–12; (X₇) MinRH (%) during day 1; (X₉) MinRH (%) during day 2; (X₁₁) Largest maxRH (%) on days 3–6; (X₁₂) Lowest minRH (%) on days 3–6; (X₁₃) Largest maxRH (%) on days 7–12; (X₁₄) Lowest minRH (%) on days 7–12; (X₁₅) Lowest minRH (%) on days 50–52; (X₁₆) Daily light period (hour).

All entries significant at 1% level.

Source: Sawan et al. (2010).

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