Replenishment and depletion of soil moisture in the northern rainfed areas of East Jordan. III-Soil Series 15.

A study to determine the amount of water stored in the root and the amounts removed by evapotranspiration under different management systems was carried out over a two year period. Observation was made on seven different farms on two slope classifications (0-3%, 3-8%) of soil series 15 in the Bishra-Irbid area. Crop management systems studied were: wheat-fallow; fallow-fallow; lentil-fallow. One system, tobacco-fallow, was discontinued because of uncontrolled experimental errors. During the first season fallow soils, 0.3% slope, stored 44 mm more water than the lentil planted area and 15 mm more than the wheat planted area. A field left fallow for two consecutive years accumulated and additional 22 mm water for the second year; 192 mm and 224 mm were the depths of total soil moisture at the end of the first season for the fields left fallow. During the second season the depths for the same sites under fallow were 181; 214 mm. Considering the texture of those very heavy soils (70% clay), nearly all this moisture won't be available for plant consumption. Soil moisture depletion in the fallow treatment was 208 mm (this value was obtained by subtracting moisture content at the end of the season, or at harvest from max. moisture attained during the season) during the first season, and 120 mm during the second season. The depletion from wheat planted areas during the first season was 178 mm. The higher depletion value in the fallow (208 vs. 187 mm) when compared to wheat is probably due to the greater abundance of weeds in the fallow land, where they have a longer growing season than wheat. Evapotranspiration for wheat was found to be 164 to 182 mm; for lentils was 135 mm; for tobacco was 122 mm. In general storage during the first season ranged from 109-13 mm; in the second-from 75-142 mm, for fallow lands. None or very little amount of this water was available to plant in the next season since depletion in this fields was 144-208 mm, first season; 91-120 mm in the second. This implies that moisture stored from the previous years has also been depleted in this season.