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Total Water Potential as an Indicator of Crop Water Deficit

M. S. U. Talukder
Department of Irrigation & Water Management, Bangladesh AgricuItural University Mymensingh

Abstract/ Executive Summary:

Lyslmeters placed in the field and protected from rain by a mobile glass roof were used to study the effects of soil moisture stress applied at various growth stapes on the total water potential of wheat plant (Triticum eestivum L. ). Soil moisture stress treatments consisted of single drought period without irrigation. It was found that none of the stress treatments showed consistent decrease of total water potential till the end of heading compared to fully irrigated plants. The results revealed that total water potential in wheat leaves decreased with the decrease of soil matric potential when stress occurred from mid-shooting to grain filling stage,

Keywords: Soil moisture stress, Crop water deficit, Total water potential

Location: Department of Irrigation & Water Management, Bangladesh AgricuItural University Mymensingh

Start Date: 00-00-1980

End Date: 00-00-1980

Program Area: Crop-Soil-Water Management

Commodity: Water management

Objectives:

To assess the value of this measure as indicator of the onset of water stress and of the severity of stress as a possible aid in irrigation scheduling.

Methodology:

Soil moisture stress at different periods during the growth of spring wheat (Triticum aestivum L. cv, 'Sappo') was studied during summer of 1980 in Iysimeters at Hojbakkeqaard, Taastrup, 20km west of Copenhagen (55⁰40 'N 12⁰18'E), 28 m above sea level. The summer of 1980 was cloudy and rainy and the temperature varied between 12 to 18? beginning mid-May to the end of August. The lysimeter soil Was a clay loam with about 15% clay at 0-30 cm soiI depth and about 18 to 20% clay at 30-100 cm soil depth. The bulk density of the whole soil profile was about 2.79 g cm-³ and the organic matter content was 2 to 3% in the upper 0-30 cm soil layer. Soil water content in the tank was viz. 260 mm at field capacity and 80 mm at permanent wilting. thus, available soil water was 180 mm. Spring wheat was sown on April 16, 1980 at a rate of 200 kg ha ^-1. The crop emerged on May 5, 1980 and was harvested on August 25. 1980. The average plant density before tillering was 320 x 10⁴ ha^-1. Each Iysimeter tank measuring 4.0 m² (2 x 2m) received a single dose of fertilizer at the rate of 125 kg N, 39 kg P and 94 kg K ha^-1 prior to the sowing. Briefly. it consists of 36 tanks, each 2 x 2m by 1 m deep. A mobile glass roof automatically protects the crop against rain. The present investigation was carried out in 18 tanks (tanks 19-36) containing clay loam soil stratified in three layers. The moisture stress treatments were as follows: To-Irrigation was withheld during the entire crop growth period (0-113 days); ( tanks 19-24); (fully stressed) . T₁- Irrigation was withheld tram emergence to shooting (0-42 days ): (tanks 25-26); (stress at shooting). T₂-Irrigation was withheld from midtillering to heading ( 21-55 days); (tanks 27-28): (stress at heading) T₃ -Irrigation was withheld from mid- shooting to grain filling stage (37-92 days); (tanks 29-30); stress at grain formation. T₄ -Fully irrigated during the entire crop growth period (0-113 days ); (tanks 31-36); (control). Total water potential study was made on 5 treatments having 1 randomly selected tank for each treatment. It was measured daily at 1200-1400 hours during each drying cycle in three fully expanded second youngest leaf (next to the flag leaf). The total leaf water potential was measured by pressure chamber technique.

Source of Information: Bangladesh Journal of Agricultural Science. Vol 16, (No-2), pp: 247-251, ISSN 0379-4296, July-1989

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

It was found that none of the stress treatments showed consistent decrease of total water potential till the end of heading compared to fully irrigated plants. The results revealed that total water potential in wheat leaves decreased with the decrease of soil matric potential when stress occurred from mid-shooting to grain filling stage.

Knowledge Management: Journal