Abstract

The status, availability and distribution of moisture distribution within a crop’s root zone depths affect the yield and growth of crops. An experiment was carried out to determine the influence of three drip irrigation regimes on pattern of moisture distribution within the soil profile of Amaranthus cruentus field. Irrigations were carried out at 50 KPa (Low stress), 60 KPa (Medium stress) and 70 KPa (Severe stress) levels. The pattern of soil water extraction differed significantly among treatments (P<0.05). A. cruentus extracts water for its use depending on available moisture within depths of the root zone. The surface soil at 0.1 and 0.2 m depths, rapidly losses moisture at the peak of the dry season in treatment 70 KPa (severely stressed level). Soil hydraulic charge was high (-80.6 and -70.9 KPa) at crop emergence in the root zone of A. cruentus during the dry season experiment of 2005 and 2006 respectively. It however reduced to as low as -5.7 KPa at crop maturity (71 – 76 DOY) due to occasional rain showers experienced around the period of crop maturity. Relationship between soil hydraulic charge and soil moisture storage gave r² = 0.82 and standard deviation ± 1.19 at P < 0.05. The findings from this research may be useful at determining the appropriate moisture stress level at which irrigation is best carried out in vegetable field for optimum yield.

Key words: Irrigation, moisture deficit, hydraulic charge, moisture storage, root zone.