GISdevelopment.net ---> AARS ---> ACRS 1991 ---> Poster Session Climatic change and wheat yield in semi ARID region of Punjab-India R. Chaurasia, P K Sharma Punjab Remote Sensing Centre, Ludhiana-141 004,India G S Mahi, Gurmit Singh Department of Agrometeorology Punjab Agricultural University, Ludhiana-141 004,India Abstract An attempt has been made to study the effect of changing climatological parameters during the grain formation period of wheat on its yield in semi arid region of Punjab. Climatological data in respect of maximum and minimum temperature, relative humidity and sunshine for the months from December to April of three decades (1961-70, 1971-80 and 1981-90) was analyzed. The analysis of the data revealed that temperature during the month of March has pronounced effect on wheat yield, whereas pre-anthesis temperature has limited effect. It has been observed that maximum temperature during March contributes negatively to the yield while temperature positively. The maximum and minimum temperature around 26° and 12°C respectively during grain formation period results highest yield of wheat in the region. Positive or negative departure in temperature by 1°C from these optimum values causes reduction in yield by about 0.2 tones per hectares. A regression analysis between maximum and minimum temperature, relative humidity, sunshine and rainfall versus yield has been worked out with gave coefficient of correlation greater than 0.8. Introduction The variation in yield of agricultural crops is largely due to the changes in the climatic parameters during its growing period. Among all the climatological parameters temperature plays an important role during the vegetative growth and grain formation of the wheat crop (Marcellous et. al., 1972 : Wardlaw et al., 1980; Rawson, 1986). It has been reported that an average temperature of 15°C during grain formation is nearly optimum for maximum grain weight. (Chowdhury and Wardlaw, 1978; Weigand and Ceullar, 1981; and Fischer, 1985). The deviation in maximum and minimum temperatures above or below optimum value are found to influence the plant activities in many ways, the cumulative effects of which are observed in yield. Grain number and weight are reduced due to prolonged high temperature and drought conditions (Saini et al 1982; McDonald et al., 1983; Wardlaw, 1989; Nicolas et. Al., 1984. On the other hand prolonged lower temperature enhanced grain formation period resulting in higher grain weight. Most of these studies have been conducted under laboratory conditions and their applicability needs be tested under field conditions. In the present paper attempt has been made to establish the relationship of wheat yield with the climatological parameters in semi-arid region of Punjab. Study Area The semi arid region of the Punjab is located in central part of the state and extends from the south-east to north-west. Ludhiana district situated in the central part of the this region having sufficiently long record of different climatological parameters has been selected for this study . Physical Resources of the region Soil climate and water The soils of the area are medium to light textured consisting variable amount of silt and clay. Temperature in the region fluctuates between 6° to 41°C. The average annual rainfall is about 700mm. The optimum climatic conditions for the wheat cultivation are observed during November to April. During this period day and night temperatures remain in the range of 20° - 30°C and 6° - 18°C respectively. In the growing season, occasional rainfall due to western disturbances amounts to 126mm and evaporation 650mm. solar radiation available to the crop is of the order of 2570 Mjm-2. Water in the region is of good quality and water table varies between 5 to 10 metres. In the flood plains, ground water contains Fe and F at some places. Irrigation and Fertilizers The intensive irrigation system increased the wheat irrigated are from 82 per cent in 1965-66 to 100 percent in 1979-80. It shows that whole of the wheat in the district is grown under assured irrigation system. The use of total NPK for wheat in the area is increasing fast with the adoption of the improved varieties. In increased from 328 kg per ha in 1980-81 to 527 kg in 1987-88 (fig. 1). Fig 1 Wheat yield and fertilizer consumption in semi arid region of Punjab 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 The highest yield according to the equation is obtained with the combination of day and night temperature of 26° and 12°C respectively. An increase or decrease in these temperatures by 1°C reduced the yield by 0.2 t ha-1. The relationship between observed and predicted yield is represented in Fig. 2. Figure 2 Relation Between Observed and predicted wheat yield Conclusion The present investigation revealed that the climatic parameters (maximum and minimum temperatures, relative humidity, sunshine hours and rainfall) at the post anthesis stage play an important role on the wheat yield. As suggested by Wardlaw et. al., (1980), Rawson (1986), the effect of temperature was more important during the grain formation period than any other climatic parameter. It is true in case of semi-arid region of Punjab where most of the wheat crop is irrigated. Year to year variation in the climatic parameters particularly temperature has large effect on wheat yield. The highest yield was observed with day temperature 26°C and night temperature 12°C, relative humidity 68 per cent and sunshine 8.0 hours. The yield was reduced drastically when March was either too hot to too cool. 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