Ind. Jn. ofAgri. Econ. Vol. 59, No. 4, Oct.-Dec. 1999 Nature and Causes of Inter-District Variations in Yield of Rice in West Bengal, 1970-71 to 1994-95 Utpal Kumar De* INTRODUCTION During the last few decades, substantial changes have been observed in the production and productivity of rice in West Bengal. Several studies have reported the significant contribution of new seed-fertiliser-irrigation technology (widely known as the technology of Green Revolution) to the growth of production and productivity (Dharm Narain, 1976; Mehta, 1981; Hazell, 1982; Rao et al. 1988; Bandyopadhyay, 1989; Ninan and Chandra- shekar, 1991). The growth of production and yield of rice however has not been uniform across different districts of the state. This paper seeks to examine the nature and extent of inter-district variations in the growth of yield of rice in West Bengal during 1970-71 to 1994-95 and the causes for such variations. West Bengal is one of the important agricultural states of India, that has been contributing nearly 15-16 per cent of annual rice production of the country since 1970-71. Its economy is predominantly agricultural. Around two-thirds of its population earn their livelihood from agricultural activities (Government of India, 1992). Rice occupies 70 per cent of the gross cropped area of the state and it is the main staple food of the majority of the population of the state (Table 1). From the exponential rates of growth it is observed that a major part of increase in production of rice during 1970-71 to 1994-95 was due to growth of its yield.' However,the increase in the yield of rice was not uniform across different districts of West Bengal. Thus from planning perspective it is essential to know the regional character of the productivity growth over time and also the basic reasons for the regional variations in productivity so that the appropriate policies can be formulated. TABLE 1. AREA AND PROPORTION OF AREA UNDER RICE TO GROSS CROPPED AREA DURING SOME SELECTED YEARS ('000 ha) Period 1970-73 1977-80 1984-87 1991-94 (1) (2) (3) (4) (5) Rice 5,005.47 5,031.60 5,217.73 5,763.13 (72.7) (70.22) (72.29) (74.85) Gross cropped area 6,867.40 7,152.07 7,235.53 7,681.67 Source: Government of West Bengal,StatisticalAbstract ofWestBengal,Bureau of Applied Economics and Statistics, Calcutta (various issues). Notes:(i) Figures in parentheses denote percentages to gross cropped area. (ii) As data on gross cropped area are not consistently available for all the years, here it is calculated by adding the area under major crops grown in West Bengal. * Lecturer, Department of Analytical and Applied Economics, Tripura University, Agartala, Tripura-799 004. NATURE AND CAUSES OF INTER-DISTRICT VARIATIONS IN YIELD OF RICE IN WEST BENGAL 555 DATA AND METHODOLOGY Choice ofPeriod The analysis is undertaken for the period 1970-71 to 1994-95. Though the Green Rev- olution has been initiated after the mid-sixties in Punjab and Haryana, the wave came to West Bengal in the early seventies. Since the data on all aspects of the study were not available beyond 1994-95, the study is limited to this period. For the purpose of analysis, the whole period is broadly divided into two almost equal sub-periods, namely, 1970-71 to 1981-82 and 1982-83 to 1994-95 because there has been a lot of change in the field of irrigation especially of groundwater irrigation in West Bengal after 1980 that has signifi- cantly contributed to the increase in the yield of rice. Thereafter, the sub-periods 1970-71 to 1978-79 and 1979-80 to 1994-95 are considered to compare the changes before and after the introduction ofland reform measures rigorously(by the then new Left-Front Government of West Bengal). Moreover, a close look at the data revealed that there was a remarkable shift in the production and productivity of rice after the mid-eighties. So the changes during 1986-87 to 1994-95 are also considered and compared with those of the first nine-year sub-period (1970-71 to 1978-79). Methodology For the purpose of analysis the data on yield have been collected from various issues of Economic Review and Statistical Abstract of West Bengal. Then triennia average yield of rice for selected years (1970-73, 1977-80, 1984:87 and 1992-95)is calculated at the district level and from these, the absolute change in yield of rice during 1970-71 to 1994-95 is calculated by simple growth rate. Inter-district disparity in yield is explained by coefficient of variation. Thereafter, exponential rate of growth of yield has been estimated by fitting regression of the type Ln Y,= + p„ for the entire period and for all sub-periods, where Y, represents yield of rice in t-th year, t the time in year and a, 3 are the two parameters. p represents the annual exponential rate of growth of yield of rice. Having examined the growth of yield, the nature of influence of some basic factors on the growth of yield is analysed. Responsiveness of yield to the variation in quantity of rainfall, irrigation and chemical fertiliser is estimated by regressing Y,on them for Burdwan district, which is one of the important rice producing districts of West Bengal. Equation of the form LnY,= p„+ f3,LnR + f32LnI+ f33LnC has been fitted, where R, I and C represent respectively rainfall (in millimetres),intensity of irrigation by government canals, measured by the ratio of area under government canals and gross cropped area (GCA) and use of chemical fertiliser per hectare of gross cropped area. Cobb-Douglas type of production function is used for estimation. Farmers in each agro-climatic region has some common characteristics of using irrigation and fertilisers in some proportion to land which has changed over time due to the changing conditions of cultivation. Use of high-yielding variety(HYV) seeds is not taken into consideration due to lack of complete series of data. Quantity of irrigation and fertiliser requirement change due to differences in soil character, varieties of rice, etc., but they are also ignored due to non-availability of data and to avoid complexity of analysis. Use of modern agri-implements also has a role in the changing yield of rice, which is not taken into account due to lack of complete set of data. 556 INDIAN JOURNAL OF AGRICULTURAL ECONOMICS However, there might be some relationship between use of chemical fertiliser and irri- gation or rainfall, which causes multicollinearity. Linear relationship between any two explanatory variables is shown in terms of a two-way correlation table given below. Two-way Correlation Matrix Variable LnI LiiC LnI 0.0135 0.3118 LnC ' ' 1 0.248 The t statistics of correlation between LnI and LnC and between Lnk and LnC are 1.227 and 1.5, none of which is significant at the 5 per cent level. ' Having identified the importance of .different factors on the growth of yield of rice, inter district disparity in the growth of those factors is discussed to explain the reasons for districtwise variation in yield growth.. For this purpose, changes in the proportion of area under irrigation and use of chemical fertiliser per unit of GCA have been considered for all the districts. In the time-series analysis of impact of the growth of irrigation on the increase in yield of rice in Burdwan, only area under government canals has been considered. However, during the last two decades the capacity of groundwater sources has increased remarkably (see Appendix). They were not included because of non-availability of complete series of data for them. RESULTS AND DISCUSSION There is an overall increase in the yield of rice, at the rate of68.77 'per cent in West‘Bengal during 1970-73 to 1992-95. Table 2shows that the rate of growth was higher during 1984-87 TABLE 2. TRIENNIA AVERAGE YIELD OF RICE IN WEST BENGAL AT DISTRICT LEVEL Triennia average of yield (kg/hectare) Simple growth rate (per cent) District/year 1970-73 1977-80 1984-87 1992-95 1970-73 1977-80 , 1984-87 1970-73 to , to to to 1977-80 1984-87 1992-95 1992-95 (1) - (2) (3) (4) • (5) (6) ' • (7) (8) (9) Burdwan 1523 (2) 1963 (1) '2032 (1) 2698 (1) 28.90 3.51 32.7.8 77.15 Birbhum 1518 (3) 1749 (2) 1825 (4) 2282 . (4) 15.20 4.35 25.04 • 50.33 Bankura .1324 (5) 1345 (6) 1697 (6) 2205 (6) 1.59 , 26.17 29.94 66.54 Midnapore 1200 (6) 1226 (8) 1563 (9) 2044 (9) 2i7 27.49 30.77 70.33 Howrah 1325 (4) 1209 (9) 1797 (5) 1904(11) -8.75 48.64 5.95 43.70 Hooghly 1629 (1) 1642 (3) 2029 (2) 2455 (3) 0.80 23.57 20.99 50.71 24-Parganas 1069(12) 1407 (5) 1433(11) 2019(10) 31.60 1.85 .40.89 88.87 Nadia 989(15) 1326 (7) 1951 (3) 2475 (2) 34.07 47.13 26.86 :150.25 Murshidabad 1110 (9) 1537 (4) 1565 (8) 2261 (5) 38.50 1.82 44.47 103.69 West Dinajpur 1037 (14) 973(13) 1241 (12) 1787 (7) -6.17 27.54 44.00 72.32 Malda 1081 (11) 1134(10) 1616 (7) 2083 (8) 4.90 42.50 28.90 92.69 Jalpaiguri 1168 (7) 907(14) 971 (15) 1235 (15) -22.30 . 7.06 . 27.19 5.74' Darjeeling 1097(10) 1051 (11) 1217(13) , 1482(13) , -4.19 15.79 21.77 35.10 Cooch-Behar 1051 (13) 828 (15) 1078 (14) 1302(14) -21.22 30.19 20.78 23.88 Purulia .