Abstract
The aims of this study were to develop out crop and water-stress coefficients of onion crop under deficit conditions of arid regions. Therefore, field experiments of fully irrigated and deficit conditions with standard agronomic practices of onion crop had been conducted in two successive growing seasons in 2011-2012 and 2012-2013 in order to develop out the crop coefficients of onion plants at different growing stages. Results revealed that crop coefficient values at different growing stages under different management parameter considerations indicated that the observed values of kc are ranged above and dawn of the estimated values of FAO. Meanwhile, data analysis revealed that a general trend of increasing CWU and attributed SCWR from the beginning of cultivation up to the end of bulb formation stage (72 days after sowing seeds), then it decreasing within bulb enlargement and maturity stage.
Highlights
Igbadun and Oiganji stated that the kc values of fully irrigatedonion treatments had ranged from 0.36 to 1.15, while those values of the deficit irrigated treatments varied from 0.24 to 1.13 under Samaro district, Nigeria [1]
This crop water stress index (CWSI) and time threshold (CWSI-TT) was the accumulated time that the CWSI was greater than a threshold value (0.45); and it was compared with a time threshold (CWSI-TT) based on a well-watered crop
Ks values were noticed to have similar trends for agronomic management parameters and drip irrigation systems SD and SSD considerations that imply the impacts of deficit irrigation condition were consistent irrespective of cropping methodologies and onion crop variety
Summary
Igbadun and Oiganji stated that the kc values of fully irrigatedonion treatments had ranged from 0.36 to 1.15, while those values of the deficit irrigated treatments varied from 0.24 to 1.13 under Samaro district, Nigeria [1]. Susan et al [2] speculated that variations of the crop water stress index (CWSI) have been used to characterize plant water stress and schedule irrigations This thermal-based stress index has been calculated from measurements taken once daily or over a short period of time, near solar noon or after and in cloud free conditions. A method of integrating the CWSI over a day was developed to avoid the noise that may occur if weather prevents a clear CWSI signal near solar noon This CWSI and time threshold (CWSI-TT) was the accumulated time that the CWSI was greater than a threshold value (0.45); and it was compared with a time threshold (CWSI-TT) based on a well-watered crop. The greatest value of water use efficiency was obtained at 60% of the field capacity, while 20% of the field capacity caused the lowest water use efficiency
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