EFFECTS OF ELEVATED CO_(2) AND TEMPERATURE ON PRODUCTIVITY OF THREE MAIN CROPPING SYSTEMS IN PUNJAB STATE OF INDIA--A SIMULATION ANALYSIS

摘要

Global climate change can affect yields of agricultural crops are likely to be affected due to rise in CO_(2) and temperature, apart from other factors. In this context, the present study aimed at to assess the effects of elevated ambient CO_(2) concentration, maximum and minimum temperatures alone and in combinations on crop productivity of three major cropping systems (maize-wheat, rice-wheat and cotton-wheat) of Punjab state of India. Series of climates were synthesized by increasing CO_(2) levels from 350 to 700ppm at interval of 70ppm and temperatures (maximum and minimum) from existing to 20percent rise at 5percent interval of the recorded data at Punjab Agricultural University, Ludhiana. Simulations were made for 15 years (1991-2005) using CropSyst model. The simulated results indicated that on doubling the CO_(2) level of the existing (350ppm) at existing temperature, yields of grain in maize, paddy in rice and seed-cotton in cotton were increased by 6.5, 4.9 and 5.5percent, respectively. In wheat, the magnitude of benefit varied from 3.8 to 12 percent depending upon the previous crop in rotation. In a complete rotation of cropping system, percent increase in wheat equivalent yield was 7.6 in maize-wheat, 7.5 in rice-wheat, and 4.7 in cotton-wheat system, respectively. Unlike effect of CO_(2), crop yields were decreased with increase in temperature. The percent decrease in yields of maize, rice and cotton were 42, 23 and 56 with increased maximum temperature (20percent of the existing) and 24, 13 and 28 with increased minimum temperature, respectively. In the cropping systems of maize-wheat, rice-wheat and cotton-wheat, percent decrease in wheat equivalent yield was 2, 23, and 39 with maximum and 12, 11 and 17 with minimum temperature, respectively. Sensitivity factors estimated by fitting a multiplicative model to the simulated data indicated that the crop yield is more sensitive to increase in maximum temperature than minimum and CO_(2). The interaction of temperature and CO_(2) suggest that decrease in yield due to increased maximum temperature by 1.0, 1.8 and 0.3 deg C or minimum by 1.8, 2.0 and 0.7 deg C of the existing temperatures can be levelled off by increased yield at double concentration of the CO_(2) than the existing in maize, rice and cotton crops.