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Evaluation of Nitrogen Management Based on Chlorophyll Meter (spad) Value in Modern Rice Varieties Under Wet and Dry Seasons

M. Sh. Islam
Agronomy Division Bangladesh Rice Research Division, Gazipur 1701

M.R. Islam
Soil Science Division Bangladesh Rice Research Division, Gazipur 1701

Z.U. Ahmed
Soil Science Division Bangladesh Rice Research Division, Gazipur 1701

Abstract/ Executive Summary:

Two field experiments were conducted at Bangladesh Rice Research Institute (BRRI) farm, Camilla to evaluate the dose and timing of urea-N application based on chlorophyll meter (SPAD value) in comparison with conventional split application method for modern rice varieties grown in wet and dry seasons. In wet season, BRRI Dhan 31 gave the highest grain yield of 4.3 t/ha at recommended N dose (90 kg N/ha), SPAD-37 with basal, and 90% of over fertilized reference SPAD with basal treatments. The grain yield produced by over fertilized (200 kg N/ha) treatment was the lowest (3.4 t/ha) which was statistically similar to that of control. Agronomic efficiency and partial factor productivity of nitrogen were the highest in 90% of over fertilized reference SPAD without basal and lowest in over fertilized (200 kg N/ha) treatment. In dry season, BRRI Dhan29 gave the highest grain yield of 5.8 t/ha in SPAD 35 and SPAD 37 threshold with basal dose which, were statistically similar to recommended dose, over fertilized reference and some SPAD value based without basal treatments. The treatments with basal dose produced higher grain yield compared to without basal. Agronomic efficiency and partial factor productivity of nitrogen were the highest in 90% of over fertilized reference SPAD with basal and lowest in over fertilized (250 kg N/ha) treatment. The relationship between grain yield and applied N was stronger in Boro than that of T.Aman season; crop response to applied N was higher in Boro than in T.Aman season. Leaf colour chart (LCC) can be used as N management tool like chlorophyll meter.

Keywords: SPAD value, Leaf color chart (LCC), Chlorophyll meter, Agronomic etticiency

Location: Regional Station, Comilla of Bangladesh Rice Research Institute

Start Date: 00-00-1998

End Date: 00-00-1999

Program Area: Crop-Soil-Water Management

Commodity: Rice

Objectives:

To evaluate the efficiency of chlorophyll meter based N management practices in comparison with conventional split application in terms of grain yield & N-use efficiency
To observe the seasonal effects on N response
To calibrate LCC with SPAD value in transplanted modem rice varieties under Boro-T.Aman cropping pattern.

Methodology:

The experiments were carried out at Regional Station, Comilla of Bangladesh Rice Research Institute during the T.Aman, 1998 and Boro 1999. The experiments were laid-out in RCBD with 4 replications. Unit plot size was 4 m x 5 m. In both seasons, the laid-out was the same. The variety under study was BRRI Dhan31 in wet and BRRI Dhan29 in dry season. Leaf-N status was assessed by a chlorophyll meter (Model: SPAD 502, Minolta Camera Co., Osaka, Japan) while reading was expressed as SPAD (soil plant analysis development) value and threshold levels were 35 & 37. Data were taken from the middle portion of the fully expanded upper most leaves. Leaf colour was also assessed at the same time and same portion of leaves by LCC- a handy plastic ruler (a Japanese prototype) with 6 shades of green (from yellowish green to dark green) on it to simulate the colour of rice leaves, but time of N top-dressing was determined on the basis of SPAD value at different growth stages. Leaf N status was assessed every week in all treatments from 21 to 63 days after transplanting (DAT) in both seasons, but 30 kg N/ha was applied in only the SPAD-value treated plots when the SPAD value dropped below the threshold level. Basal dose of 30 kg N/ha was applied in assigned plots in both seasons. Each plot received blanked dose of P, K, Sand Zn as triple superphosphate, muriate of potash, gypsum and zinc sulfate respectively at the time of final land preparation. Thirty-day and 45-day old seedlings were transplanted at 20 cm x 20 cm spacing during the wet and dry seasons respectively. Other intercultural operations like weeding, mulching etc. were done as and when necessary. The treatments were as follows: T ₁ = Control (No) , T₂= Recommended dose (90 kg N/ha in wet and 120 kg N/ha in dry season) in 3 equal splits at 20, 35 & 50 DAT, T₃ = Farmer's practice (60 kg N/ha in wet and 80 kg N/ha in dry season) in 2 equal splits at 20 & 40 DAT, T₄ = Nitrogen applied as top-dress based on SPAD 35 without Basal, T₅ = Nitrogen applied as top-dress based on SPAD 35 with Basal (30 kg N/ha), T₆ = Over fertilized ref. (200 kg in wet & 250 kg N/ha in dry season) in 4 equal splits at basal and 20, 35 & 50 DAT, T₇ = *90% of over fertilized reference SPAD without Basal, T ₈ = *90% of over fertilized reference SPAD with Basal (30 kg N/ha) , T ₉ = Nitrogen applied as top-dress based on SPAD 37 without Basal and T₁₀ = Nitrogen applied as top-dress based on SPAD 37 with Basal (30 kg N/ha). Data taken on different parameters were statistically analyzed by IRRISTAT program and DMRT was used for treatment mean comparisons.

Source of Information: Bangladesh Agron. J. 1998,8 (1 & 2): 37-45, ISSN 1013-1922

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

It may be concluded that N management on the basis of SPAD value is feasible in both wet and dry seasons under transplanted condition. Basal N application may be effective in dry season only. The suitable threshold value might be 37 for BRRI Dhan31 in wet season and 35 for BRRI dhan29 in dry season. Crop response to N is higher in dry season compared to wet season. Leaf Colour Chart (LCC) can be used as N-management tools like chlorophyll meter in wider scale, where the critical threshold value is 3.0-3.5 in both wet and dry seasons.

Knowledge Management: Journal