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Validation of Dras Model for Boro Rice Irrigation-2006

Dr Manorangan Mondal
SSO
IWMD, BRRI

Abstract/ Executive Summary:

A field experiment was conducted to compare the model predicted NIR with the BRRI recommended water application for rice cultivation; and to determine rice yield by adopting model predicted NIR and BRRI recommended irrigation practices in Boro seasons. Nine water treatments were followed as T₁= Application of 50-70 mm irrigation water 3 days after ponded water disappeared from rice field (BRRI recommendation), T₂= NIR application considering ET, S&P and RF at 0.50p, T₃= NIR application considering instantaneous ET, S&P and RF, T₄= NIR application same as T₂ except seepage i.e., using reported percolation only and levee protected by poly sheet, T₅= NIR application same as T₃ except seepage i.e., using reported percolation only and levee protected by poly sheet, T₆= NIR application same as T₂ but considering 0.20 allowable depletion, T₇= NIR application same as T₃ but considering 0.20 allowable depletion, T₈ = NIR application same as T₃ but considering 0.40 allowable depletion, T₉ = NIR application same as T₃ but considering 0.60 allowable depletion. The drought assessment (DRAS) model was developed by the Center for Environment and Geographical Information Services (CEGIS) to predict net irrigation requirement (NIR) of different crops under different agro-ecological environments and yield loss, if any occurred due to climatic variations in wet and dry years. To predict the model an experiment was conducted with 9 irrigation treatment at BRRI farm, Gazipur. The DRAS model predicted relatively optimum NIR for rice cultivation in Boro/dry season in various water regimes imposed in the field for rice cultivation, it seems to provide irrigation water requirements for rice with sufficient accuracy for the farming community. The study should be conducted further for fine tuning of the model in rice cultivation.

Keywords: DRAS model, NIR, Water management

Location: BRRI farm, Gazipur

Start Date: 01-11-2005

End Date: 30-06-2006

Program Area: Crop-Soil-Water Management

Commodity: Water management

Objectives:

To compare the model predicted NIR with the BRRI recommended water application for rice cultivation; and
To determine rice yield by adopting model predicted NIR and BRRI recommended irrigation practices in Boro seasons.

Methodology:

A field experiment was conducted to compare the model predicted NIR with the BRRI recommended water application for rice cultivation; and to determine rice yield by adopting model predicted NIR and BRRI recommended irrigation practices in Boro seasons. Nine water treatments were followed as T₁= Application of 50-70 mm irrigation water 3 days after ponded water disappeared from rice field (BRRI recommendation), T₂= NIR application considering ET, S&P and RF at 0.50p, T₃= NIR application considering instantaneous ET, S&P and RF, T₄= NIR application same as T₂ except seepage i.e., using reported percolation only and levee protected by poly sheet, T₅= NIR application same as T₃ except seepage i.e., using reported percolation only and levee protected by poly sheet, T₆= NIR application same as T₂ but considering 0.20 allowable depletion, T₇= NIR application same as T₃ but considering 0.20 allowable depletion, T₈ = NIR application same as T₃ but considering 0.40 allowable depletion, T₉ = NIR application same as T₃ but considering 0.60 allowable depletion, BRRI dhan29 was used as the test variety for Boro season and recommended cultural and fertilizer management practices were followed in growing rice (BRRI 2004). Seedlings were raised outside the experimental field and 39 days old seedlings for Boro were transplanted after proper land preparation with 20 x 20 cm spacing. Individual plot size was 3m x 5m having 1.0m x 1.5m buffers space around each experimental unit. Fertilizer was applied as per BRRI recommendation. The whole amounts of P, K, Zn and S were applied as basal at the time of final land preparation. Urea was top-dressed in three equal splits. Weeding and spraying were done twice to control weeds and attack of insect-pest in each season. Rice yield was assessed on the basis of whole plot yield. Harvested paddy was threshed, cleaned and weighed to determine yield. Finally, the yield was adjusted to 14% moisture content to determine yield per hectare.

Source of Information: Proceedings of BRRI Annual Internal Review for 2006

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

ET and seepage and percolation (S&P) are considered water requirements for rice grown under low land environments. Therefore, total water requirements for rice was varied from 715 to 852 mm depending on the variable water regimes imposed in the rice field.The lowest amount of water applied in treatment T₉, which was close to ET demand for rice during its growth span. About same water was applied in T₁in comparison with that of ET requirements and it was almost similar in T₄, T₅, T₈ and T₉. Water applied in other treatments was about 22-47% higher than that applied in T₁ mainly because of the presence of continuous ponded water in rice field in those treatments in comparison with intermittent water application in T₁. The highest amount of water was applied in T₂ and T₆. In BRRI recommended practice, irrigation water applied in almost all the decades except decade 10 and 11, due to 59 and 13 mm rainfall occurred in these decades. But application of irrigation water was needed in all decades as per model predicted value. It was observed that NIR prediction on the basis of current year rainfall data was almost similar to BRRI recommended water management practice. It is interesting to note that irrigation water application was similar and less in all the treatments except about 35% more water was applied in treatments T₂and T₆ compared to actual requirements for optimum yield of rice. Therefore, the model predicted reasonably accurate NIR for rice in Boro/dry season. Rice yield was almost similar in all the water regimes mainly due to the application of more irrigation water than the ET demand for rice. BRRI dhan29 produced about 8.0 t/ha yields irrespective of water treatments. Although rice yield did not differ significantly, about 3% yield difference was observed in T₆ and T₄in comparison to T₁.

Knowledge Management: Report/Proceedings