Climatic change and wheat yield in semi ARID region of Punjab-India
Materials and Methods
The yearly production and area of wheat, total NPK consumption and wheat area for the period from 1960-61 o 1989-61 to 1989-90 for Ludhiana district as reported in statistical Abstract of Punjab have been used. For each year the yield and NPK applied (t/ha) have been calculated. The climatological parameters considered for this study are daily means of maximum and minimum temperatures, relative humidity, sunshine hours and monthly totals of rainfall. The yield data for three decades were analyzed separately. The relationship between individual climatological parameters for each month and yield has been worked out.
Results and Discussion
Average yield and Climate
The adoption of improved varieties of seed and better farming techniques resulted continuous increase in the wheat yield in the region. It has almost tripled in a span of thirty years (1961-1990). (fig. 1). The average yield in three decades viz., 1961-70, 1971-80 and 1981-90 was respectively 2.22, 3.16 and 3.74 t ha-1. In comparison to first decade, per cent increase in the average yield in second and third decade was 42 and 70 percent respectively (table 1). The yield (kg ha-1) in the three decades follows equation y = a*t+b, where a and be for three decades are given in Table 1. increase in yield in 1st, 2nd and 3rd decades according to the equations are respectively 182, 29 and 109 kg ha-1 per year.
As indicated in Table 2, the month of March during the first decade was extremely warm and dry (Tx 30.9°C, H 53) and night was comparatively humid and cooler both during day and night (Tx 25.1°C, Tn 10°C) thereby increasing grain filing period and yield. The climatic conditions during number of years in third decade were nearly optimum (Tx/Tn 26°/12°C, H 67 and S 8.0 resulting in higher grain yield (Story, 1965).
Table 1 : Average yield for three decades and regression constants
| Period |
Yield t.ha-1 |
Percent increases in yield |
Regression constants |
| A |
B |
1961-70
1971-80
1981-90 |
2.22
3.16
3.74 |
-
42
70 |
182.2
29.3
109.4 |
1215.67
3000.47
3136.93 |
Table 2: Average climatic conditions in the three decades in the month of March.
| Period |
Temperature °C |
Relative humidity (%) H |
Sunshine rainfall |
| Max Tx. |
Min Tn |
Mean Tm |
Hours S |
(mm) R |
1961-70
1971-80
1981-90 |
30.9
25.1
26.0 |
9.9
10.0
11.9 |
20.4
17.5
19.0 |
53
63
67 |
8.8
8.3
8.0 |
26.1
20.7
33.9 |
| 1981-90 |
|
|
|
|
|
|
Highest and Lowest yield and Climate
During three decades the highest yield 3.14, 3.45 and 4.30 t ha-1 were observed respectively in the year 1968, 1979 and 1989 (table 3). However, during 1989, the climatic conditions appears most congenial for high yield. In this year day and night temperatures were 26.2° and 11.5°C respectively, relative humidity 68 percent and sunshine greater than 8 hours. These conditions are favorable for higher photo synthetic activity and better grain formation. These results corroborate the findings of Friend (1966). The data in Table 3 suggests that the lowest yields are observed in the years having one or more factors unfavourable. Analysis of the data indicate that day temperature in the range of Analysis of the data indicate that day temperature in the range of 25°C – 27°C and night temperature 11-12°C results highest yield (table 4).
Table 3 : Highest and lowest yield (t/ha) during the decade and climatic conditions in the month of march.
| Decade |
Year |
Yield t.ha |
Tx |
Tn |
Tm |
H |
S |
R |
| Highest Yield |
I
II
III |
1968
1979
1989 |
3.14
3.45
4.30 |
28.2
24.1
26.2 |
13.0
10.0
11.5 |
20.6
17.1
18.9 |
54
69
68 |
-
8.2
8.8 |
23.5
53.1
32.4 |
| Lowest Yield |
I
II
III |
1966
1976
1987 |
1.88
2.82
3.45 |
30.0
24.5
26.8 |
9.4
9.7
12.8 |
19.7
17.1
19.8 |
51
68
68 |
-
7.0
8.0 |
17.3
25.3
8.0 |
Climatic parameters and wheat yield relationships
The grain yield has high correlation individual with maximum and minimum temperature, relative humidity and sunshine for the month of March (Table 5). All the parameters except maximum temperature have positive correlation and contribute to yield. The maximum temperature has negative effect on yield.
A regression equation establishing the relationship between the climatic parameters (Tx, Tn, H, S, R) for the month of March and grain yield (q ha
-1 of wheat gave r = 0.81. The regression equation is as under :
Table 4: Range of day and night temperature (°C) and wheat yield
| Tx |
Yield t.ha |
No. of years |
Tn |
Yield t.ha |
No. of years |
<25
25-27
27-29
29-31
>31 |
3.27
3.55
3.08
2.91
1.80 |
7
8
6
4
5 |
<10
10-11
11-12
12-13
>13 |
2.31
3.21
3.60
3.42
2.67 |
10
6
6
6
2 |
Table 5 : Correlation coefficients between climatic parameters and wheat yield.
| Month |
Climatic parameters |
| Tx |
Tn |
H |
S |
R |
February
March |
-0.67
-0.78 |
0.59
0.61 |
0.30
0.61 |
0.39
0.55 |
-0.15
-0.08 |
Y = 17.48 – 1.22* Tx + 0.87*Tn + 0.2*H + 3.13*S – 0.04*R
