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Residual Effects of Azolla and Urea on the Yield of Rice

M. H. MIAN
Department of Soil Science, BAU, Mymensingh.

Abstract/ Executive Summary:

A field study was carried out to test the residual effects of Azolla and urea applied to the first rice crop (BR11), on the yield of consecutive second (BR3) and third rice (BR11) crops. The isotopic study showed that the grain yield of the first rice crop increased significantly due to the application of Azolla (4.38 t ha-1 ) and urea ( 4.08-4.14 t ha-1) over the control (2.36 t ha-1). These yield increases were due to increased N uptake by the rice plants from Azolla-treated (136 kg ha-1) and urea-treated (116-121 kg ha-1) soiIs over the control (63 kg ha-1). The second rice crop registered some residual effects of Azolla and urea but the yields were much lower compared to the first crop. The Azolla (3.65 t ha-1) showed significant residual effects over urea ( 2.87-2.94 t ha-1 ). The third crop failed to register any significant residual effects. The ¹⁵N tracer showed that the first rice crop received 35% of total N applied as Azolla while the second crop received only 8%. In case of urea, the first and second rice crops received 28-30% and 2-3% of total ¹⁵N applied, respectively. No ¹⁵N was detectable in the third crop.

Keywords: Azolla, 15N tracer, Residual effect, Urea

Location: Field laboratory of Department of Soil Science, BAU, Mymensingh

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Rice

Objectives:

In the present study the 15N- labeled Azolla and urea were used once to grow three successive rice crop to assess the expected residual effects.

Methodology:

Soil: The experiment was carried out in the field laboratory of Department of Soil Science located at the southern part of the Bangladesh Agricultural University Farm. The soil belong, to sonatola series of Noncalcareous Dark- Grey Floodplain type. It had the following initial characteristics: pH 7.0, organic carbon 0.89%, available P 12 ppm, available K O. 14 meq 100 g-1 and 0.09% total N. Experimental Layout: The randomized block design was followed to set up the experiment. There were five replications. Each plot had a 1 m X1 m = 1 m² area. The bunds were Iined with thick polythene paper to check outward Iikages. The P and K were applied as basal to all plots at final land preparation. The treatments were: 1. Control (No N applied). 2. 60kg N ha-1 as Azolla (1/2 ¹⁵N--labelled+1/2 unlabelled); 2-splits. 3. 60 kg N ha-1 as urea (1/2 ¹⁵N- labelled + 1/2 unlabelled); 2- splits. 4. 60kg N ha-1 as urea (¹⁵ N- labelled) ; 3-splits. Azolla and urea application: Azolla pinnata, a local strain, was labelled with ¹⁵N in 2mX2m size polythene lined field plots grown for 21 days. The fronds were harvested, washed well and nitrogen content was determined. The requisite amount of Azolla on the basis of N-content was incorporated into soil to supply approximately 30kg N ha-1 at transplanting. Similarly, another amount of Azolla was incorporated (unlabelled) in between rice rows at 45 DAT to supply approximately 30kg N ha-1. In case of 2-split incorporations of urea, 30 kg N ha-1 was added at transplanting (¹⁵N -labelled) and the rest 30kg N ha-1 was incorporated (unlabelled) at 45 DAT. In case of 3-split incorporations of urea, 20 kg N ha-1 was incorporated at transplanting, 20kg N ha-1 at 25 DAT and the last 20 kg N ha-1 at 45 DAT. About 5-6 cm water layer was maintained up to 15 days of harvest.

Source of Information: Proc. BAU Res. Prog. 6: 133-139, 1992

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The ¹⁵N tracer showed that the first rice crop received 35% of total N applied as Azolla while the second crop received only 8%. In case of urea, the first and second rice crops received 28-30% and 2-3% of total ¹⁵N applied, respectively. No ¹⁵N was detectable in the third crop.

Knowledge Management: Journal