Evapotranspiration by stages of development in celery (Apium graveolens)

The aim of the study is to determine the evapotranspiration by stages of development, with which, in an indirect way, quickly and easily predict and manage the irrigation regime of head celery. A field experiment was conducted with celery in the Plovdiv region, grown under irrigated conditions. There are six options, irrigated with different irrigation rates, are set as follows: option 1) 130%, option 2) 100%, option 3) 70%, option 4) 50% and option 5) 30% of the calculated rate, option 6) without irrigation. In the hypothetical optimal variant, a pre-irrigation humidity of 80% of the FC (field capacity) was maintained in the 0-40 cm layer. The development period is divided into three sub-periods: 1 - from the interception of seedlings to the beginning of root formation; 2 - beginning of growth of the root crop and 3 stage - Intensive growth until harvesting. ETc was established by phases of development for celery, and in the layer 0-0.4m a maximum (3.8 and 4.42) was recorded in phase 2 - the beginning of the formation of the root crop, respectively for the variants irrigated with 100% and 130 % of the norm. With the same options, but at a depth of 0-0.5m ETc is 4.81 and 5mm. In the first phase of development, celery spends about 155 mm in variants 1 and 2, between 110 and 95 in variants 3 and 4 and between 78 and 60 mm in variants 5 and 6.