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Soil Moisture Content and Salinity Dynamics of Ploughed and Unploughed Land in the Coastal Region of Bangladesh

M. M. Alam
Scientific Officer
IWM Division, BRRI, Gazipur-1701

M. K. Mondal
Senior Scientific Officer
IWM Division, BRRI, Gazipur-1701

A. B. M. A. Hossain
Scientific Officer
IWM Division, BRRI, Gazipur-1701

G. K. Bhuiyan
Scientific Officer
FMPHT Division, BRRI, Gazipur-1701

Abstract/ Executive Summary:

Out of 2.85 million hectares of coastal and off-T-shore land, about a million hectare in 64 upazila of 13 districts is affected by varying of salinity with about 100% cropping intensity. T. Aman is the main crop in this region. Irrespective of location, the common trend is an increase in salinity with time from December to April until the onset of monsoon rains. The study was conducted in BRRI farm, Sonagazi to determine suitable irrigation time for Rabi crops as well as suitable seeding depth of Aus and Kharif-I crops. Soil moisture content and salinity for both ploughed and unploughed land were monitored in both root zone (0-45 cm) and seeding zone (0-9 cm) depth of crops at 20 days interval. Both the zones were divided into three sub-layers (root zone: 0-15 cm, 15-30 cm, 30-45 cm and seeding zone: 0-3 cm; 3-6 cm; 6-9 cm). Considering the root zone depth, the study results showed that for both ploughed and unploughed land soil salinity decreased with the depth. But for ploughed land, higher soil salinity was found in the lower layer during the mid February to Mid March. The study was indicated that increase in the soil salinity is associated with decrease in the soil moisture content. The depletion of soil moisture content was more rapid in unploughed than the ploughed land in all the layers. The soil moisture went below the allowable depletion limit during mid February - Mid March in the first layer and mid February to Mid April in the second and third layer. Therefore, irrigation is needed for shallow rooted non rice crops during mid February to Mid March and for deep rooted non rice crops from mid February to Mid April. In the seeding zone, soil salinity reached at the highest and soil moisture content at the lowest level in March. The study also indicated that for both ploughed and unploughed land, the topmost layer is not suitable for seeding in Kharif-I season (March) as it contains higher level of soil salinity in lower level of soil moisture content. As most of the time 2^nd(3-6 cm) and 3^rd layer (6-9 cm) retained a considerable amount of moisture (more than 20%), and lower level of soil salinity (< 3.7dS/m) so these layers are suitable for seeding.

Keywords: Soil Moisture, lrrigation time, Salinity, Ploughed and unploughed land

Location: BRRI farm Sonagazi, Feni

Start Date: 00-00-2002

End Date: 00-00-2002

Program Area: Risk Management in Agriculture

Commodity: Soil salinity

Objectives:

To determine suitable irrigation time for Rabi crops and suitable seeding depth of Aus and Kharif-l crops.

Methodology:

The study was conducted in Rabi season 2002 at BRRI farm Sonagazi, Feni. Soil physical properties were analyzed using different methods: textural classification was done by hydrometer method, bulk density by core-cutter method, and particle density by density bottle method. To determine the moisture content at field capacity, soil was watered sufficiently and covered with polyethylene sheet for 24 hours and the moisture content was determined by gravimetric method. The study was conducted at two different levels- macro and micro which represents the root zone depth and seeding depth, respectively. Both the levels comprised of three sub-layers. In the root zone depth level the sub-layers were 0-15 cm, 15-30 cm and 30-45 cm whereas in the seedling depth level the sub-layers were 0-3 cm, 3-6 cm and 6-9 cm. Soil samples were collected from both ploughed and unploughed land. The soil moisture content and salinity at different layers were monitored regularly from January to May with an interval of 20 days. The soil moisture content was determined by gravimetric method and soil salinity level was determined from saturation extract by using conductivity meter.

Source of Information: Int. J. Sustain. Agril. Tech. 2(2):69-76, February 2006

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The depletion of soil moisture content was more rapid in unploughed than the ploughed land. The soil moisture went below the allowable depletion limit during mid February to Mid March in the first layer and mid February to Mid April in the second and third layer. Therefore, for shallow rooted non-rice crops irrigation is needed during mid February to Mid March while for deep rooted non-rice crops irrigation is needed from mid February to mid April.

Knowledge Management: Journal