Abstract
Actual evapotranspiration and crop coefficient (Kc) of Amaranthus cruentus grown in weighing lysimeter was determined under a screen house. The weighing lysimeter was made of a cylindrical plastic of circular cross-sectional area of 0.076 m2 and diameter 0.3 m. Climatic variables such as solar radiation, relative humidity, air temperature and wind speed were collected for the estimation of reference evapotranspiration (ETr) using the FAO-Penman Monteith model. Actual crop evapotranspiration (ETc) was measured directly from the daily drop in the level of water in the burette that was connected to the lysimeter. Crop factor (Kc) was estimated from the ratio of ETc /ETo. The ETc of the crop rose gradually from the period of emergence (4.5 mm week-1) during the 1 week after planting (WAP) to a maximum value of 14.3 mm week-1 during the 7 WAP. Kc for the emergence and maturity stages of Amaranthus cruentus were 0.15 and 0.36, respectively. The highest leaf area index (LAI) and leaf coverage area were 11.39 and 0.866. The optimum soil moisture content for the highest Kc value (0.36) was 11.7%. The output of this research will be useful for farmers who are into vegetable production for enhanced productivity at farm levels. Key words: Lysimeter, Amaranthus cruentus, crop factor, soil water content, leave area index.
Highlights
A detailed knowledge of crop evapotranspiration from the period of crop emergence to maturity is essential for the assessment of water resources and storage requirements, the capacity of irrigation systems, optimal allocation of water to crops and for the decision making in agriculture (Oguntunde, 2004)
Throughout the course of the research (April to June), the relative humidity had a minimum value of 75.5% (± 4.73) which was recorded in the 1 week after planting (WAP) and highest relative humidity was recorded in the 8 WAP with a value of 85.1% (± 2.47) (Figure 3)
This study shows the crop evapotranspiration (ETc) and the crop coefficient (Kc) of Amaranthus cruentus growing in a lysimeter placed in a screen house
Summary
A detailed knowledge of crop evapotranspiration from the period of crop emergence to maturity is essential for the assessment of water resources and storage requirements, the capacity of irrigation systems, optimal allocation of water to crops and for the decision making in agriculture (Oguntunde, 2004). Knowing the crop’s evapotranspiration is very much essential in determining the crop’s irrigation requirement. It helps to save water by controlling water supply through better determination of crop water requirements and development of biological and physical criteria (Katerji et al, 1997) leading to precise determinations of irrigation schedules for efficient performance of irrigation systems supplying water to field (Pereira et al, 2002; Ramirez and Harmsen, 2011); and to improve the water use efficiency of species and plant varieties that are cultivated.
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