DEMELASH KEFALE, SENARATNE RANAMUKHAARACHCHI, MICHAEL ZÖBISCH
Asian Institute of Technology, Agricultural Systems and Engineering, Thailand
Growth and flowering patterns of three Ethiopian maize varieties (viz. A-511, ACV" 6 and Katumani) were tested at five different soil-moisture regimes (i.e., no drought stress throughout the growth - control, and soil-moisture stress induced at one week before tasseling, at silking, at grain filling, and throughout the growth). The study was carried out under field conditions (in Ethiopia) and in a greenhouse (Thailand). Mean daily air temperatures in Ethiopia were 21°C and in Thailand 28°C.
Under field conditions, the drought-stress regimes significantly modified the flower development of all tested varieties when compared to the control. Moisture deficit throughout the growth period prolonged the time to tasseling (). This shortened the interval between tasseling and silking (TSI) (). On the other hand, drought stress induced at one week before tasseling delayed silking () without an affect on the time to tasseling. This widened the TSI by 36% ().
In the greenhouse study, induced drought stresses at different growth stages did not show significant differences in flowering. However, the overall average days to tasseling and silking were reduced by 18% and 22%, respectively, while the average TSI of the three varieties increased by 47% compared to the experiment conducted under field conditions. In the greenhouse, the cumulative heat-unit requirement in terms of growing degree-days (GDD) showed an increase of 9% for tasseling and 15% for silking. The general thermal index (GTI) showed changes of 9% for tasseling and for silking.
The response of the three maize varieties to drought stress -- due to the changes in temperature -- was significantly different in respect to the time to tasseling and silking, and the required average heat units for flowering. These are critical determinants of grain yield of maize.
Keywords: Flowering pattern, growing days, Ethiopia