EFFECT OF PERIODICAL CO2 ENRICHMENT ON WHEAT cv. PBW 343 THROUGH FIELD AND SIMULATION STUDY

Abstract

The global population is rising and demand for protein-rich diets are increasing pressure to maximize the agricultural productivity. At the same time rising atmospheric CO2 altering the global temperature and precipitation patterns, are challenges to agricultural productivity. It has already been proved that a rising CO2 provides a unique opportunity to increase the productivity of C3 crops by improving the photosynthetic activity in the plants. Thus, under ample supply of CO2 condition the carboxylation process is accelerated and resulting in increased photosynthesis which in turn enhances the plant growth. This phenomena is termed as “Carbon Dioxide Fertilization Effect” and defined as the enhancement of the growth of plants as a result of increased atmospheric CO2 concentration. Wheat (Triticum aestivum L. and related species) is an important crop grown over the entire globe. It covers more than 25% of global cropland and contributing about 21% of calories and 22% of protein to the human food supply. Even after such a coverage and dependency of people globally, the observed average yield is well below the potential gains. There is ample room for improving the productivity by utilizing the rising atmospheric CO2. As of now only a fraction of available genotype of wheat has been tested for CO2 responsiveness. In order to evaluate the response of rising CO2 on wheat an experimental field study was conducted in Haridwar district of Uttrakhand State (India) during the years 2011-12 and 2012-13. Wheat cultivar PBW 343 was taken as a test genotype using locally designed low-cost per unit area Open Top Chamber (OTC) experiments. The study was undertaken with the specific objectives to (1) assess the effect of periodical CO2 enrichment on microclimatic change in wheat crop. (2) Evaluate the effect of periodical CO2 enrichment on growth, development, yield and quality of wheat crop. (3) Calibration and evaluation of the DSSAT CERES-Wheat model using field experimental data. (4) Suggestion for the agronomic ways and means to improve the productivity of wheat under changing climate. Field experiment was laid out in Randomized Block Design (RBD) with 4 treatments of CO2 enrichment and 3 replications during Rabi season (November-April) of the years 2011-12 and 2012-13. Treatment includes -Control (without CO2 enrichment), 700 ± 50 ppm CO2 (enrichment once a week, 700 ± 50 ppm CO2 (enrichment twice in a week) and 700 ± 50 ppm CO2 (enrichment thrice in a week) on the demonstration farm of the Department of Water Resources Development ii and Management, Indian Institute of Technology Roorkee, Uttrakhand (India). Fire extinguishing CO2 cylinders were used for CO2 enrichment. IPCC projections for the years 2050 (550 ppm) and 2100 (750 ppm) were used as a guideline for CO2 enrichment in wheat crop. Observations were recorded for the changes in microclimate, plant growth and development attributes, yield and yield attributes, physical and chemical quality components of grain. For calibration of DSSAT CERES Wheat model under the soil climatic condition of Roorkee, a separate field experiment was conducted using cultivar cv. PBW-343 with recommended package of practices during the year 2013-14 with four different dates of sowing i.e. 15th Nov.; 22nd Nov.; 29th Nov. and 6th Dec. All the growth, yield and yield attributes were recorded for calibrating the CERES Wheat model. In order to derive the genetic coefficient, DSSAT CERES Wheat model was run iteratively by adjusting genetic coefficient values until the simulated and observed values were statistically significant. Furthermore, the DSSAT CERES wheat model was evaluated by using results on growth, development and yield attributes obtained from different treatments of the field experiment conducted during the years 2011-12 and 2012-13. Actual soil parameters, weather parameters, and the crop management practices followed under different CO2 enrichment treatments were used as the data input to run the model for different treatments. Genetic coefficient generated in the calibration process was used to run the model. The effect of CO2 enrichment treatments on the growth, development and grain yield was simulated. The simulated values were statistically compared with the observed values. Various statistical techniques i.e. Root Mean Square Error, Normalized Root Mean Square Error, Mean Bias Error, Index of Agreement, Fractional Bias, Coefficient of determination and Percent Deviation etc. were adopted to evaluate the model outputs. The CERES Wheat model was also used to test the sustainability of experiment in the future scenario. For this purpose PRECIS-regional climate model derived weather data were used for simulating the wheat productivity during the period of 2015-2030 keeping in view the agro technological advances. Further, to suggest the agronomic adoptions for improving the wheat productivity in the future (2015-2030) changing climate, the model was run by taking five dates of sowing and five nitrogen doses under four CO2 scenarios. iii The periodical CO2 enrichment under field condition was employed using locally available lowcost materials (Fire extinguishing quality CO2, iron rods and normal plastic sheet) as an alternative to FACE and OTC techniques. Further, the CO2 has been used to assess the climate change impact and its fertilization effect on wheat productivity. The CO2 enrichment effect on a particular wheat variety (cv. PBW 343) has been established through a two year experiments. Similar, study can be replicated for a longer period to test the validity of experiment for various genotype of wheat at different agroclimatic regions of India. Results obtained from the field experiment are summarized as follows: 1. A marginal increase of 0.2-0.5 ºC in leaf temperature, within canopy temperature and above canopy temperature was noticed among the CO2 treated plots. Practically there was no abnormality shown by the crop with such a change in temperature, probably this increase was purely temporary in nature as the crop was grown under the open field condition. The average ambient CO2 concentration in the experimental plot was recorded as 309 ppm during 2011-12 and 319 ppm during 2012-13. The result showed that the CO2 level rose to about 770 ± 10 ppm at the time of application which subsided to 560±10ppm within 15 minutes of application and further subsided to normal equivalent to ambient within 20 minutes. 2. The CO2 enrichment treatments of wheat crop cv. PBW-343 recorded significant increase in plant height, tiller count, leaf length and width, dry matter, LAI, flag leaf area, leaf area duration, % effective tiller, grain weight /plant (g), grain test weight (g), grain yield, straw yield and biological yield though the CO2 enrichment effect was insignificant for ear emergence, anthesis, and flowering, no. of grain/spike, harvest index, grain length and width. Grain Protein & Nitrogen content were significantly decreased and carbohydrate content was increased due to CO2 enrichment. Other macro nutrient content such as K, Mg and S increased and P, Ca were decreased, though the change was insignificant. 3. The calibration of the DSSAT CERES wheat model using field experimental data of four dates of sowing conducted during 2013-14 shows that the variation of observed and simulated growth, development and yield parameters are within the acceptable range. Thus, the DSSAT CERES wheat model output is acceptable to soil climatic condition of Roorkee. iv 4. The DSSAT CERES wheat model was evaluated using field experimental data of four CO2 enrichment treatments conducted during the years 2011-12 and 2012-13. Model simulated growth and yield parameters are at par with actual experiment. This proves that the model could be effectively used for simulating field experiment of Wheat cv. PBW 343. 5. The DSSAT CERES Wheat simulation during the years 2015-2030 showed that the yield will decline with the advancing of climate change but CO2 intervention will compensate the loss in yield due to higher temperature and erratic rainfall pattern (climate change). 6. The DSSAT was used to develop the adaptation strategies for the future (2015-2030) under the climate change and higher CO2 scenarios. The result showed that the better yield can be obtained by sowing the wheat between 14-28 November, and adopting the nitrogen application between 100-120 kg/ha. Study reveals that the response of periodical enrichment of CO2 on wheat cv. PBW-343 under the soil climatic conditions of Roorkee (Haridwar, Uttarakhand, India) is beneficial to increase its productivity.