Evapotranspiration and Water Use Efficiency of Wheat as Affected by the Variations in the Availability of Soil Moisture

Abstract

The influence of variations in the availability of soil moisture, with or without mulches, on the evapotranspiration (ET), yield and water use efficiency (WUE) was investigated using wheat as a test crop, growing in Wagnar pots (1/2000 a). Three soil moisture conditions as pF1.8, pF2.5 and pF 1.82.8 with no or straw or vinyl mulch was imposed on the wheat, variety Omase. Seasonal total and mean ET varied among the soil moisture conditions and mulch types. The highest ET was observed at pF1.8N2.8 without mulch. Mulch efficiently conserved moisture suppressing soil evaporation. ET increased from the tillering to the panicle initiation stages, remained similar till the dough stage and decreased up to maturity. Eliminating the influences of meteorological factors, the ET/Epan ratio was calculated and showed that the ratio increased from tillering to panicle initiation and decreased gradually in the following stages. Continuous wet conditions with excess moisture at pF1.8 hampered root growth, affected crop performance and resulted in a reduced ET, yield, harvest index (Fil) and WUE. At pFl.8 and pF2.5 more grams per panicle and bolder grams contributed to the relatively higher grain yield with straw mulch while at pF 1 bolder grams contributed to the highest grain yield under the no mulch condition. Dry matter yield (DMY) reduced under the dry condition at pF 2.5 compared to the standard condition (pF 1.8'2.8). Use of mulch decreased DMY under dry condition at pF 2.5 relative to the ideal irrigation condition, but increased the WUE reducing ET. ITI decreased under wet or dry conditions but use of mulch improved the Hl. However, the continuous wet conditions reduced the effectiveness of moisture and at pF 1.8N2.8 with or without mulches were conducive for increased. These results may be useful for the appropriate husbandry of the limited soil moisture, where soil moisture is the principal source of water for cropping in the water shortage areas.