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Effect of Soil Bulk Density and Moisture Regime on the Root Development of Wheat (tridcum Aestivum)

M. A Mazid Miah
Soil Science Department, Dhaka University, Dhaka

S. M. A. Faiz
Soil Science Department, Dhaka University, Dhaka

T. H. Khan
Soil Science Department, Dhaka University, Dhaka

M. K. Alam
Soil Chemistry Division, Bangladesh Rice Research Institute, Gazipur

Abstract/ Executive Summary:

An experiment was conducted in the greenhouse of the Soil Science Department, Dhaka University, to study the effect of four levels of soil bulk density (1.46, 1.51, 1.55 and 1.63 g/cm³ at five soil moisture levels (7, 10, 15, 20 and 25%) on the root development of wheat. At lower moisture levels (7 and 10%}, an increase in soil bulk density upto 1.51 g/cm³increased the length, surface area and weight of wheat roots while at higher moisture levels increasing soil bulk density beyond 1.46 g/cm³ decreased these root parameters. The total length of roots was much higher in the lower depths of soil in the pots at lower bulk density levels f1.45 and 1.51g/cm³ , than in pots containing soil at higher bulk density ( 1.55 and 1.63 g!cm ). An increase in soil water content upto 20%, increased the root length and surface area in the upper layers of soil. This was true for all bulk density levels. A soil bulk density of 1.46 g!cm 3 associated with 20% moisture favoured the maximum growth of roots.

Keywords: Soil, Bulk density, Soil moisture, Wheat

Location: The Green House of the Soil Science Department of Dhaka University, Bangladesh

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Wheat

Objectives:

To find out the effects of soil bulk density and moisture on the root development of wheat.

Methodology:

The experiment was conducted in the green house of the Soil Science Department of Dhaka University. The soil was collected from the BARCfarm, Kashimpur, Gazipur. It represents soil of the Kashimpur series (Madhupur tract). The soil was air-dried and ground to pass through a 2 mm sieve. Sub samples of the soil was used for physical and chemical analyses. The treatment in this experiment consisted of four levels of bulk density (initially maintained at 1.30,1.40, 1.50, and 1.60 g/cm³ and five levels of moisture (7, 10, 15,20 and 25% on weight basis which represented 28, 40, 60, 80 and 120% of field moisture capacity. Wheat (Triticum aestivum cv.) was the experimental crop. All possible combinations of these treatments were tested. The experiment was carried out in dark plastic pots of uniform diameter and height. In each pot, 4 kg of soil was placed. Bdore potting, NPK fertilizers at the rates of 100, ·80, 60 mg!kg soil as urea, T.S.P. and MP were mixed thoroughly with soil and then the fertilizer treated soil was slightly moistened with tap water. A portion ·of the 4 kg soil was first placed in the pot spread uniformly and compacted evenly with the help of a wooden hammer of about 15cm diameter. This process was repeated until the 4 kg of soil attained a definite height in side the pot to reach the desired density level. The total length of the 50 roots and their average diameter were calculated. The measured roots and the remainder of each portion were oven dried separately and weighed. The dry weight of the measured roots was then related to that of the remainder of each portion to determine the total length for each average root diameter. The total surface area of roots in each portion was calculated separately from the total length and diameter. The values in each section were added together to give the ' grand total. The surface area of root was measured by using the formula: Surface area = 2 rh were, r is the radius and h is the length of roots.

Source of Information: Bangladesh J. Soil Sci. 21(1):30-35, 1990, Vol. 21, No. 01, ISSN 0253-5440

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Both total length and surface area of roots were very low at 7% soil moisture and in creased with the increase in soil moisture content upto 20% and then declined with a further increase in moisture level. The decrease in total length of roots obtained at 25% moisture may have been as sociated with poor aeration in the soil. At 7 and 10% soil moisture levels, the increase in bulk density from 1.46 to 1.51 g/cm³ increased the total length and surface area of roots and the increase was prominent at 7% moisture level. At comparatively high soil moisture levels, poor aeration may limit the root growth of wheat plants. An increase in bulk density upto a certain limit at low moisture levels may establish better root-soil or root-soil solution contact which may increase the availability of both water and nutrients ac celerating root development. As the soil is compacted beyond a certain limit, soil mechanical impedance begins to hamper root development and the growth, nutrition and yield of wheat may be adversely affected. The optimum moisture level for nor mal root development in a specific soil depends on its bulk density. At the same time, the optimum soil bulk density depends on the moisture status of the soil. It appears that soil compaction upto a limit may be beneficial for wheat depending on the soil moisture content. While using tillage implements, care should be taken so that the soil bulk density does not exceed the optimum level. The total length of roots was much higher in the lower depths of soil in the pots at lower bulk density levels f1.45 and 1.51g/cm³ , than in pots containing soil at higher bulk density ( 1.55 and 1.63 g!cm ). An increase in soil water content upto 20%, increased the root length and surface area in the upper layers of soil. This was true for all bulk density levels. A soil bulk density of 1.46 g!cm 3 associated with 20% moisture favoured the maximum growth of roots.

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