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Drying Patterns of a Heavy Textured Soil Under Different Surface Conditions

A. Hamid
Institute of Postgraduate Studies in Agriculture, Salna, Gazipur

Md. M. Rahman
Bangldesh Agricultural Research Institute, Joydebpur, Gazipur

, Md. Mohiuddin
Bangldesh Agricultural Research Institute, Joydebpur, Gazipur

M. Jafarullah
Bangldesh Agricultural Research Institute, Joydebpur, Gazipur

M.A. Akhtaruzzaman
Bangldesh Agricultural Research Institute, Joydebpur, Gazipur

Abstract/ Executive Summary:

A field experiment was conducted on a Grey Terrace soil at IPSA Farm. Salna during 1984 dry season to monitor changes in soil water content over time following irrigation. The soil was allowed to dry for 40 days. Cumulative evaporation as affected by tillage and mulch was approximated. Time to attain falling rate stage of drying after soil saturation under variable surface conditions was evaluated. Both tillage and surface conditions influenced soil drying patterns appreciably. Mulching reduced evaporation and delayed attaining falling rate stage of drying by three days compared to bare soil. Regardless of tillage treatments, bare soil maintained constant rate of evaporation for three days following saturation whereas mulched soil continued for six days. Bare tilled and untilled soils did not differ appreciably in respect of total amount of water evaporated from upper 0 - 20 cm layer. Rate of water loss from the tilled soil was much higher initially which diminished over time. In the untilled soil most of the water was lost from 0-10 cm layer whereas the sub-surface layer (10-20 cm) of tilled soil has substantial contribution to total water loss. Considerable variation in evaporation was observed between tilled and untilled plots. Cumulative evaporation from surface soil during falling rate stage of drying and change in soil water content has been approximated as a function of square root of time.

Keywords: Drying pattern, Textured soil, Surface conditions

Location: Institute of Postgraduate Studies in Agriculture farm, Salna

Start Date: 08-02-1984

End Date: 31-03-1984

Program Area: Crop-Soil-Water Management

Commodity: Land management

Objectives:

To evaluate the drying patterns of a heavy textured soil subjected to varying tillage practices and mulch cover

Methodology:

The experiment was conducted at the Institute of Postgraduate Studies in Agriculture (IPSA) farm, Salna during February 8 through March 31, 1984. A nearly homogeneous field measuring 60 m x 50 m was selected and weeds were removed. The field was equally divided into two parcels. One half of the land was ploughed keeping the other half uncultivated. Rice straw at 10 t/ha was spread uniformly as mulch on half of each cultivated and uncultivated sub-plots making four different treatments, such as uncultivated + mulch, uncultivated bare, cultivated + mulch, and cultivated bare. The land was heavily irrigated for 10 days to saturate the soil. One day after the termination of irrigation, free water from the surface was drained off. Changes in water content in the profile up to one meter depth was monitored gravimetrically daily for one week beginning one day after completion of the drainage. During the second week, soil moisture was monitored every other day. From day 15 onwards, soil moisture was monitored at 5 day intervals. The experiment was terminated on day 40. During the course of investigation weeds were not allowed to grow nor was any surface water allowed to enter the experimental plots. Clay and silt contents were fairly high with low organic matter content. The bulk density ranged between 1.28 and 1.39 g/cc which increased with depth vertically downward. Figure 1 depicts the environmental conditions prevailing during the course of this investigation. Throughout the study period weather was dry with almost clear sky and was no precipitation during the period of experimentation. Relative humidity was fairly low averaging 65 %. Solar radiation averaged 340 cal cm^-2 min^-1. In the absence of cloud cover the solar radiation was relatively high. Difference between daily maximum and minimum temperature was minimal. Day temperature increased progressively over the period reaching 36⁰C on day (March 31).

Source of Information: Bangladesh Agron. J. 1990, 3(1 & 2): 1-7

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Regardless of tillage treatments, bare soil maintained constant rate of evaporation for three days following saturation whereas mulched soil continued for six days. Bare tilled and untilled soils did not differ appreciably in respect of total amount of water evaporated from upper 0 - 20 cm layer. Rate of water loss from the tilled soil was much higher initially which diminished over time. In the untilled soil most of the water was lost from 0-10 cm layer whereas the sub-surface layer (10-20 cm) of tilled soil has substantial contribution to total water loss. Considerable variation in evaporation was observed between tilled and untilled plots. Cumulative evaporation from surface soil during falling rate stage of drying and change in soil water content has been approximated as a function of square root of time.

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