Effects of Meteorological Parameters and Irrigation on Cotton Phenology in Greece
Sep 12, 2018
The influence of temperature, relative humidity, rainfall and irrigation on the duration of cotton phenological stages was studied in the cotton producing zone of Greece during a 10 year period (1986-1994). Influence was found to be parameter and stage dependent. Temperature was the most time affecting parameter. More specifically, the minimum temperature in the early stages and the maximum temperature in the late stages played the most significant (negative) role. Within the temperature range encountered, the variability between temperature (Ta) and time to a certain phenological stage (N) was explained only slightly better by an exponential than a linear function. By fitting a linear regression between 1/N and Ta, the thermal time required above a threshold temperature (To) was estimated for each developmental stage between sowing and harvesting and for the whole cotton cultivation zone. Rain lengthened cotton developmental stages, particularly when falling between sowing and anthesis or boll opening and harvest. Addition of irrigation water to rainfall, weakened regressions. The role of the relative humidity in regulating cotton phenology was insignificant, except occasionally after squaring. Multiple regression analysis, taking into account together all parameters studied, was justified as the coefficient of variation was usually increased. However, in many cases one or more parameters, apart from temperature, could be omitted as non-significant. Predictability of the relations established is discussed.