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Validation of Dras Model for Boro Rice Irrigation at Gazipur Area-2007

Dr M A Rashid
CSO and Head
IWMD, BRRI

M Ibrahim
CEGIS

Abstract/ Executive Summary:

An experiment were carried out to validate DRAS model at BRRI farm, Gazipur. Nine water treatments were applied with BCBD design. Evapotranspiration (ET) is considered the minimum amounts of water needed for optimum yield of rice. But it is difficult to maintain continuously saturated condition in rice field to avoid water losses other than ET. Therefore, ET and seepage and percolation (S&P) are considered water requirements for rice grown under low land environments. Total ET demand was 383 mm during the growth span of rice, whereas S&P requirements were variable due to variable water regimes imposed for rice culture. Therefore, total water requirements for rice was varied from 705 to 968 mm depending on the variable water regimes imposed in the rice field.It is noted that irrigation water application was similar and less in all the treatments except about 52% 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. The plant height and panicle length was almost similar in all the treatments. BRRI dhan29 produced almost similar grain weight, but the effective tillers per square meter and percent filled grains varied among water regimes. The highest number of effective tillers per square meter was found in T₃ and was similar to other treatments except T₁, which produced the lowest. 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 7.0 t/ha yields irrespective of water treatments. Rice yield did not differ significantly among the irrigation regimes compared to T₁.

Keywords: DRAS model, NIR, CEGIS

Location: BRRI farm, Gazipur

Start Date: 30-12-2006

End Date: 30-06-2007

Program Area: Crop-Soil-Water Management

Commodity: Water management

Objectives:

To compare model predicted net irrigation requirement (NIR) with BRRI recommended water application for rice irrigation

Methodology:

Experiment was set-up in randomized complete block design (RCBD) at BRRI farm, Gazipur.The treatments were:

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. Seedlings were raised outside the experimental field and 47 days old seedlings 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. Irrigation water was applied as per model predicted NIR based on the water treatments and was measured by volumetric method. Seepage and percolation was measured by using a vertical gauge installed in the middle of experimental plot. A USWB Class A evaporation pan and a rain gauge was installed near the vicinity of the experimental field for determining rainfall and evaporation values during the growing season of rice. All the data were recorded at 7:30 AM daily to determine S&P, rainfall and evaporation from the experimental field.

Source of Information: Proceedings of BRRI Annual Internal Review for 2007

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

ET and seepage and percolation (S&P) are considered water requirements for rice grown under low land environments. Total ET demand was 383 mm during the growth span of rice, whereas S&P requirements were variable due to variable water regimes imposed for rice culture. Therefore, total water requirements for rice was varied from 705 to 968 mm depending on the variable water regimes imposed in the rice field. It is noted that irrigation water application was similar and less in all the treatments except about 52% 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. BRRI dhan29 produced almost similar grain weight, but the effective tillers per square meter and percent filled grains varied among water regimes. The highest number of effective tillers per square meter was found in T₃ and was similar to other treatments except T₁, which produced the lowest. 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 7.0 t/ha yields irrespective of water treatments. Rice yield did not differ significantly among the irrigation regimes compared to T₁.

Knowledge Management: Report/Proceedings