Table Of ContentsNext Page

Possible impact of climate change on rice production in the Gangetic West Bengal, India

Saon Bannerjee

AICRP on Agrometeorology
Directorate of Research,
Bidhan Chandra Krishi Viswavidyalaya
Kalyani, Nadia: 741235. West Bengal. India.
E-mail: sbaner2000@yahoo.com

Abstract

Climate change, the greatest challenge to global community, will affect the agriculture of the tropical countries.. To provide food security in India, the production and productivity of the staple foods such as rice must be increased. To assist with increased production it is important to assess the production potential of different crops under climate change regimes. This study reports on the impact of increased temperature on rice production in the Gangetic West Bengal as assessed through the crop growth model WOFOST (WOrld FOod STudies).

Experiments on different dates of sowing were carried out using the popular rice cultivar MTU 7029 (Swarna) in the years 2004 to 2006 at Gontra Village, Ghetugachi PO, Nadia, West Bengal, India (231’ N latitude, 8835’ E longitude and 9m altitude. Phenological characteristics, thermal time requirements for different phenophases, yield and yield attributes were measured. These data were used to validate and run the crop growth model WOFOST for the Indo-gangetic plain of West Bengal. Two climate change situations were considered, an increase in the maximum and minimum temperature by 1C and 2C.

The simulated yield decreased due to a temperature increase of 1C and 2C are was 300 kg/ha and 800 kg/ha respectively. Under increased temperature conditions, the crop growth model predicted a slight increase in above ground biomass, dry stem and leaf weight for the first 25 days of crop growth . The study concludes by considering suitable management option to reduce the impact of climate change.

Key words

Temperature, Crop simulation models, Climate change, Rice

Introduction

The economic condition of West Bengal, as well as of India as a whole, depends mostly on agriculture. Despite increased grain yield through green revolution, agriculture is still heavily dependent on annual rainfall and the pattern of rainfall distribution, indicating its susceptibility to climate change. Agriculture in tropical countries like India are more vulnerable to climate change. Moreover, if there is any inherent problem of water holding capacity of soil, the effect of climate change is likely to be more pronounced (Milly, 1994; Milly and Dunne, 1994).

Because of population growth, it is necessary to increase the production and productivity of rice, the most important staple food, to provide food security in India. But the production potential of rice in different location under probable climatic situation must be assessed. To predict the yield and yield potential of a locality under a given climatic condition/ changed climatic condition, crop growth models can be used successfully. This study reports an investigation on the impact of climate change on rice production in the Gangetic Alluvial Zone of West Bengal, India.

Materials and methods

The model

The WOFOST (WOrld FOod STudies) model was used to simulate growth and production of the rice. WOFOST was originally developed as a crop growth simulation model for the assessment of the yield potential of various annual crops in tropical countries (Boogaard et al., 1998).

The WOFOST model considers three growth levels correspond to crop production, namely,

  • Potential production: Crop growth is determined by irradiation, temperature and plant characteristics only. Atmospheric CO2-concentration is assumed to be constant. All other factors are assumed to be in ample supply.
  • Limited production: In addition to irradiation, temperature and plant characteristics, the effect of the availability of water and plant nutrients is considered. If the supply of water or nutrients is sub-optimal during (parts of) the growing season, this leads to water- and/or nutrient-limited production, which is normally lower than potential production. This holds for biomass production, in some cases water limited yield may be higher than potential yield because of more favorable harvest index.
  • Reduced production: At this level, the possible reduction in crop yield by mostly biotic factors like weeds, pests and diseases is taken into account.

The potential production represents the absolute production ceiling for a given crop when grown in a given area under specific weather conditions. It is determined by the crop's response to the temperature and solar radiation regimes during the growing season. In the present study the variation of potential production of rice in the in the Gangetic West Bengal was considered under different climatic scenario.

Field experiment

In this study, MTU 7029 (Swarna) a popular rice cultivar grown in the New Alluvial Zone of West Bengal was used. Experiments on different dates of sowing were carried out to determine the phonological characteristics, thermal time requirement for different phenophases, yield, yield attributes, etc., which in turn were used to validate the crop growth model.

Result and discussion

Model evaluation

The performance of the WOFOST model was evaluated for different dates of sowing of rice. If the crop is transplanted on 15th July in a year, it is observed that difference between predicted and actual yield is only 37 kg/ha. As in Gangetic West Bengal, the normal date of transplanting is 15th July, so it can be concluded that the model can predict the yield well. The leaf area changes were measured and the measured value was tallied with the predicted one. Similarly, the predicted values of yield and biomass are very much close to the observed (actual) values. The results showed that WOFOST can able to simulate the temporal changes in leaf area index and biomass for different treatments satisfactorily. Only for phasic development study, the duration of pre-anthesis phase and maturity are under-predicted. Although the phasic development is under-predicted, the model can safely be used for climate change impact study as the deviation from the normal is usually observed for such study.

Impact of climate change

The yield decrease due to temperature increase by 1C (both maximum and minimum) is in the tune of 300 kg/ha. If the temperature is increased by 2C, the potential yield may be reduced to about 800 kg/ha (Table 1). In the initial period, the above ground biomass is slightly increased under warmer temperature conditions (Fig. 1).

Table 1. Effect of climate change on crop duration and yield of rice

 

Duration of pre-anthesis phase (Days)

Maturity
(Days after emergence)

Yield
(Kg/ha)

Predicted under normal temperature condition

74

118

5650

Predicted under 10C temperature increase

72

114

5315

Predicted under 20C temperature increase

72

113

4773

Fig. 1: Probable change of biomass due to 10C and 20C temperature increase over normal

Similar results are also observed in case of dry stem and leaf weight (Fig. 2 and 3). Due to temperature increase the rate of tillering is more, hence in initial period the predicted biomass and other related parameters are also higher than the normal situation. With the progress of crop growth period, the predicted biomass under normal climatic condition is more. If the mean temperature is greater than 1C, the model output shows a decrease of dry matter accumulation of 6 kg/ha/day. This may be due to higher evaporative demand and reduction of photosynthetic rate. Due to temperature increase as the crop matures earlier, the biomass and ultimately the yield is reduced.

Fig. 2: Variation of dry stem weight under changing climatic condition

Fig. 3: Variation of leaf dry weight under changing climatic condition

Conclusion

In this study, the simulated impact of climate change on rice production is negative mainly due to increased temperature reducing yield and biomass. Suitable agronomic and other management option must be identified to reduce the yield gap. One suggested practice is more frequent irrigation without changing the total irrigation amount. It is important that the crop is sown within the proper sowing window.

References

Boogaard, H.L. , C.A. van Diepen, R.P. Rtter, J.M.C.A. Cabrera, H.H. van Laar, 1998. WOFOST 7.1; user's guide for the WOFOST 7.1 crop growth simulation model and WOFOST Control Centre 1.5. Wageningen (Netherlands), DLO Winand Staring Centre, and Los Baos (Philippines), International Rice Research Institute. Technical Document 52.

Milly, P.C.D. 1994. Climate, interseasonal storage of soil water, and the annual water balance. Adv. Water Resour. 17:19–24.

Milly, P.C.D., and K.A. Dunne. 1994. Sensitivity of the global water cycle to the water-holding capacity of soils. J. Clim., 7:506–526.

Top Of PageNext Page