Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 10/17/2002
Publication Date: 10/17/2002
Citation: Amer, K.H., Hatfield, J.L. 2002. Canopy Resistance as Affected by Soil and Weather Factors in Potato Irrigation Scheduling [CD-ROM]. Egyptian Irrigation Conference Proceedings. Cairo, Egypt.
Technical Abstract: Irrigation requires a method of quantifying the crop water status or root zone depletion of water. A direct measure of canopy resistance has the potential of being used as a crop water status indicator for irrigation management. Canopy resistance as affected by soil and weather factors has been used to incorporate automatic feedback of water into the plant root zone through an irrigation system. A study was conducted on potato (Solanum tuberosum) grown in northern Egypt at Shibin El-Kom on a loam soil for winter (2001/2002) and spring (2002) seasons. Plant height and leaf area index (LAI) were measured from emergence to maturity. Air, soil, and canopy temperatures, relative humidity, wind speed, net radiation, heat flux and soil water content were recorded as averages every 30 min throughout both seasons. Diurnal canopy resistance was determined for well-watered conditions and achieved minimum value of 20 and 10 s/m at noontime during winter and spring periods, respectively. A power relationship for well-watered condition was developed between canopy resistance and net radiation at various plant growth stages. The power was around 0.86 for all growth stages but the equation constant differed based on LAI for early growth and mature stages. In deficit soil water conditions, canopy resistance increased linearly with decreasing available soil water with a change in potato canopy resistance of 0.75 and 0.387 s m**-1 / % available soil water for 1 and 2 MJ/m**2/h of net radiation at mid-growth, respectively. A ratio of actual/potential canopy resistance was derived to normalize the meteorological differences between growing seasons. This ratio was 2.5 when 50% of available soil water was removed and can be used as a parameter to schedule automatically irrigation system using weather factors and canopy temperature. Canopy resistance increased linearly with increasing soil solution salinity, EC, when the soil solution was above the threshold soil salinity value. A ratio of rc/rcp was found in use for potato irrigation scheduling for both saline and water deficit conditions. Canopy resistance can be used as a method to schedule irrigations in potato.