Crop plants are exposed to several environmental stresses, which all affect plant growth and development and consequently hamper the productivity of crop plants. Drought is considered to be the most devastating environmental stress, which decreases crop productivity more than any other environmental stress.
Drought severely affects plant growth and development, with substantial reductions in crop growth rate and biomass accumulation. In relation to hop plants, drought negatively affects the quantity and quality of the hop yield. More specifically, shortage of water in the soil causes lower yields, uneven ripening, uneven size of cones and a reduction in the quantity of lupulin. Irrigation has a direct impact on the amount of water in the soil. It can be defined as the practice of supplying water to the root zone of the crop so as to permit farming in arid regions and to offset drought in semiarid or semi humid regions.
Intensive production of hops in the gravelly areas of Savinja Valley soon showed that irrigation is a very necessary technological process. Various irrigation technologies and equipment have been tested at the Institute of Hop Research and Brewing (IHPS) since its establishment.
The first irrigation studies started in 1958, when an irrigation method in which water is sprayed with sprinklers above the wired structure (wirework or trellis) was tested. In 1960, sprinkler irrigation tests with sprinklers attached to wooden or concrete poles were carried out. Five years later half-stable irrigation equipment in hop plantations was evaluated, which included tests of spraying plant protection products through the irrigation system.
After 1982, extensive research with hose-pull irrigators began. Since 1995, the research focus has mainly been on the implementation of drip irrigation systems in the sector of hop production. It should be noted that the hop industry is one of the first sectors in agriculture in which the country has invested in irrigation systems. Due to the good organization in the hop industry sector, running and maintenance of irrigation equipment and irrigation systems is one of the most exemplary in Slovenia.
In connection with irrigation, an evapotranspiration station (lysimeter) was built in 1974. In the same year, researchers started measurements of hop evapotranspiration, in parallel with research into the possibilities of predicting the need for irrigation in hop plantations. Based on these studies, an irrigation prognosis for hop plants has been established since 1980.
Today, IHPS predicts the need for irrigation for several types of soil for a sprinkler type of irrigation method (hose-pull irrigators). In addition, in the field of hop irrigation, IHPS performs various irrigation experiments and research within Slovenian and European projects.
Hop irrigation is a subject that is gaining a lot of attention as a result of climate changes. In the past twenty years Slovenia has experienced six droughts that had a significant impact on agriculture and were classified as natural disasters. In the past twenty years drip irrigation technology studies and their influence on the quantity and quality of the hop crop, as well as the development or support of irrigation decision making (irrigation forecasts) have received the most attention in irrigation research. We have recently concentrated on modelling water distribution in the soil beneath the above-ground drip irrigation system used in hop farms. Our recent activities have involved updating, refining, modernizing and building new irrigation systems in the Savinja Valley where our collaboration with the Chamber of Agriculture and Forestry of Slovenia and the Agriculture and Forestry Institute Celje has been excellent.