The aim of the paper is to determine the relationship between meteorological drought and hydrological drought in the agricultural basin of the River Osa (northern Poland) in the years 1966-2015. Meteorological droughts appear as a result of insufficient amount or lack of atmospheric precipitation. As a consequence of meteorological droughts occurrences, there appear hydrological droughts which are characterized by low discharges of a river. Standardized Precipitation Index (SPI) and Standardized Runoff Index (SRI) indicators were used for the identification of droughts at various accumulation periods, i.e. 1, 3, 6, 9 and 12 months. In the years 1966-2015, there were identified from 63 (SPI-1) up to 10 meteorological droughts (SPI-12), while hydrological droughts – from 22 (SPI-1) to 8 (SPI-6, 9 and 12). The strongest relationship between the two kinds of droughts occurred in the periods of accumulation from 9 to 12 months. The values of the correlation coefficient between the meteorological and hydrological droughts were above 0.5 in those cases. Those indicators can be used for a system of early drought warning, which is of particular importance for crop production in agricultural areas. Long-lasting meteorological droughts contribute to increase of water intake for irrigation purposes, thus deepening the hydrological drought. As a consequence of the prolonged and intense hydrological drought, further irrigation may be impossible due to too low river discharges.

Spring barley grain of the new registered Lithuanian variety 'Alsa' and German malty variety 'Otis' cultivation, the influence of different rates of nitrogen fertilisers and fungicide Tango on their yield and quality was investigated in the Rumokai Research Station of the Lithuanian Institute of Agriculture in 1998-2000. It was established that nitrogenous fertilisers have been increasing grain yield in the spring barley 'Alsa' every year. The influence of nitrogen fertiliser was negative on the spring barley 'Otis' only for the 1998 yield due to meteorological conditions, that were favourable for spreading leaf diseases. Fungicide Tango gave a reliable yield increase - from 0,21 to 1,14 t ha*[-1) - through the whole investigation period. The amount of proteins in grains was reliably increasing due to nitrogenous fertilisers within all the years of investigation, excluding the year 1999. Meteorological conditions made a great influence on protein amount in 1999. No reliable interaction was established between nitrogenous fertilisers, grain size and starch. Medium or strong negative correlation was observed between the grain size and proteins (correlation coefficient was deviating from 0,40 to 0,81). A reliable positive correlative relation was established between starch and grain size in 1998 only.

Weather conditions in Latvia are very favourable for the development of potato late blight caused by Phytophthora infestans (Mont) de Bary. The control of potato late blight can be performed using different approaches: standardised technology, prognoses of the first infection and prognoses of the progress of disease development. The negative prognosis model Negfry is based on the last two mentioned above. For the control of potato late blight in Latvia mainly has been used - standardised technology. The first field treatment was made during the row closing or according to prognoses. Regular treatments were made each 8-14 days. The use of NegFry model started in Latvia in 1998. Local varieties and weather data have been used for the trial. For the control of potato late blight in field trials standartised fungicide application was compared with the NegFry model and the untreated variant. The major task of the use of the model is possibility to reduce the number of fungicide treatments. The NegFry model helps to realise an integrated plant protection system, which decreases fungicide application and increases economical efficiency.

Late blight (Phytophthora infestans) is one of the most serious potato diseases. The light blight forecasting is a very important factor for the protection of potato plants. NEGFRY is a decision support system for scheduling the chemical control of potato late blight. Trials were carried out in 2000-2001 at the Lithuanian Institute of Agriculture (LIA) in Dotnuva in medium early and moderately susceptible to late blight varieties. Ordinary plant protection systems against late blight and different NEGFRY models were compared. Results of two years' investigations show that by using NEGFRY models we can obtain satisfactory protection of potato crop and get higher yield using fewer spray applications.