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Chemistry of Submerged Soils and Growth and Yield of Rice I. Benefits from Submergence

A. ISLAM
Department of Soil Science, University of Dacca, Bangladesh

W. ISLAM
Department of Soil Science, University of Dacca, Bangladesh

Abstract/ Executive Summary:

Submergence caused a small initial decline followed by a gradual increase in pH values of soil solution. At field capacity too, the pH showed similar trends but the changes were much less pronounced. The redox potential of soil solution decreased sharply and assumed negative value after five weeks of submergence. At field capacity, however, more or less similar values were maintained throughout the growing period of rice plants. Submergence caused an increase in concentration of both water-soluble iron and manganese. The concentration of water-soluble phosphorus increased upon submergence, reached maximum and then decreased. The changes in phosphorus concentration at field capacity were irregular. The concentration of nitrate decreased under submerged condition but the case was reverse at field capacity. Submergence resulted in an accumulation of ammonical nitrogen. At field capacity also the concentration of ammonical nitrogen increased with time, but the increase was much less pronounced. Submergence caused an increase in the concentration of calcium, magnesium, and potassium in the soil solution. The nitrogen, phosphorus, potassium, calcium, and iron contents of rice plants grown under submerged condition were higher than those in plants grown at field capacity condition. The plants grew better under submerged condition than at field capacity condition. The yield of grain was better under submerged condition than that at field capacity condition. Better growth and yield was associated with higher uptake of nutrients by rice plants grown under submerged condition.

Keywords: Submergence, Yield of rice, Ammonical nitrogen, Field capacity

Location: Dacca (Red soil tract) ; Kashore, Mymensingh (Brahmaputra Alluvium) ; Assadpur, Rangpur (Teesta tract) ; Chanchora, Jessore (Gangetic Alluvium), Bayra Khulna (Coastal saline tract) and Ruptali, Barisal (Coastal saline tract

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Rice

Objectives:

To study (a) the chemical and physicochemical changes that take place in submerged soils and (b) their ultimate bearing on the growth and yield of rice.

Methodology:

Soil samples representing 0.6" depth and differing in pH, texture and chemical properties were collected from different parts of Bangladesh, namely Parbata, Dacca (Red soil tract) ; Kashore, Mymensingh (Brahmaputra Alluvium) ; Assadpur, Rangpur (Teesta tract) ; Chanchora, Jessore (Gangetic Alluvium), Bayra Khulna (Coastal saline tract) and Ruptali, Barisal (Coastal saline tract). A greenhouse experiment was set up in the Department of Soil Science, University of Dacca with a total of 36 glazed silica pots arranged in completely randomized design. Two weeks old seedlings of rice (Oryza sativa variety 'Boro') were transplanted at the rate of 3 plants per pot. Each soil was replicated thrice in both field capacity and submerged conditions. The soils in pots at field capacity received sufficient distilled water to bring the soil just to field capacity and every effort was made to keep the moisture content at this leve1 during the experiment by the addition of distilled water whenever needed. The soils under submerged condition were kept continuously submerged and 2', standing water in these pots was maintained by the daily addition of distilled water. The soil solutions used for analysis were the percolates collected from the bottom of the pots at submergence and the displaced soil solutions from the pots at field capacity. they were collected in the strict absence of air in 500 m1erlenmeyer flasks which have previously been filled with nitrogen. The flasks were then stored in a refrigerator till analysis. The soil solutions were collected at the intervals of 0, 1, 3, 5, 9, and 13 weeks from the start of the experiment and were analyzed for the following (a) pH; (b) redox potential (c) nitrate nitrogen; (d) ammonium nitrogen; (e)phosphorus; (f) calcium; (g)magnesium; (h) potassium; (i) iron and (j) manganese. The plants were finally harvested at maturity and their weights were recorded. The dry weights of grains produced were also noted. Plant samples were than analyzed for (a) nitrogen; (b) phosphorus; (c) calcium; (d) magnesium; (e) potassium; (f) iron and (j) manganese.. Soil analysis. The mechanical analysis was done by the hydrometer method according to Piper.Organic carbon was determined volumetrically by wet oxidation method as devised by Walkley and B1ack18. Exchangeable calcium, magnesium and potassium were determined on the normal neutral ammonium acetate leachate of the soil by using flame photometer. pH was determined by using the Pye pH meter. 2. Solution analysis. Nitrate and ammonium form of nitrogen were determined separately from the soil solution following the method described by Piper. Iron was estimated by the method of Fortune and Mellon. Manganese was determined by the method outlined by Willard and Greathouse, and later modified by Peech. Phosphate was analysed by a modification of the benzene-isobutanol method described by Martin and Doty. Calcium, magnesium and potassium were determined directly from the soil solution by using the flame photometer (sp. 900). 3. Plant tissue analysis. Nitrogen in the dried plant tissue was determined by using the method of Pierce and Haenisch10 and later modified by Prince. Phosphorus content in perchloric acid extract of the dried tissue was measured following the method devised by Fiske and Subarrow. Calcium, magnesium, potassium and iron were estimated directly in the perchloric acid extract with the help of a flame photometer (sp. 900). Manganese was determined by the method of Willard and Greathouse and later modified by Peech.

Source of Information: Plant and Soil 39, 555-565 (1973)

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The nitrogen, phosphorus, potassium, calcium, iron, and manganese contents of rice plants grown on soils kept at submergence were higher than those in plants grown at field capacity. These constituents also varied quite considerably with soils at the same moisture level. To relate these variations with nitrogen, phosphorus, potassium, calcium, magnesium, iron and manganese in soil solutions collected at the end of 3rd week from pots both at submergence and field capacity correlation studies were made following the methods devised by Snedecor. Significant positive correlation at 1% level was obtained between nitrogen and manganese in soil solution and those in plants. Significant positive correlation at 5% level was also obtained in case of calcium and phosphorus of soil solution at both submerged and field capacity condition and those in plants.Average nitrogen, phosphorus, potassium, calcium magnesium iron and manganese contents of the aerial vegetative portion of rice plants grown on soils at submerged and field capacity conditions. (Results expressed in per cent)Growth of rice plants as reflected from dry matter production and grain yield on soils at submerged condition varied significantly. This was probably associated with variation nutrients extracted in soil solution. At field capacity growth on Porbata soil was only significantly better than growth on Kashore and chanchora soils. The growth of rice plants, in respect of dry matter production, was better under submerged condition. Significant differences were noticed in case of Chanchora, Assadpur and Bayra soils only.

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