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.

The field experiment of IOSDV (set up in Tartu in 1989) with application of mineral nitrogen fertilizer in combination with different forms of organic fertilizer (manure, straw) during 2 years has led to changes in mineral nitrogen level depending on fertilization regime used. Crop rotation was the following: potato-spring-wheat-spring-barley. The weather conditions during the period of the study were rather different and it appeared that weather conditions are more important factors in determining mineral nitrogen content and crop yields than applying fertilizers.

By using city of Jelgava and its separate districts as an example, the article investigates the practical applicability of some theoretic investigations related to the life in cities.

The change from large scale agriculture to private small scale farming has resulted in a severe lack of plant protection means. Fields of Latvia have become more weedy for last four years. This fact shows the necessity for a change in the strategy of weed control. The effect of inexpensive and wide-spread herbicides 2.4-D and MCPA is insignificant in weed control. From 1994 Latvian State Centre of Plant Protection has been studying the occurance of weed species in the Central part of Latvia (Vidzeme), to make use schedules of necessary herbicides. The research was carried out jointly with the Latvia University of Agriculture. During the research carried out from 1997 to 2000, 60 weed species were established, but in all the crop sowings 10 species were predominant. The number of Elymus repens, Myosotis arvensis and Viola arvensis has increased during last four years. In Vidzeme region, from 1997 to 2000, it was stated that soil infestation of weed seeds varies from 4.5 to 11.1 thousand seeds per square metre on the average. Perennial dicot-weeds have shown the lowest variation coefficient, compaered with other weed groups.

It is well known that secretion of gastric acid is regulated neurally by the stimulation of n.vagus and humorally by the activation of histamine H2 receptors in parietal cells. The purpose of the investigation was to clear up neural and humoral regulation mechanisms of gastric acid secretion in the postnatal ontogenesis of calves. Four calves from 5 to 14 weeks of age with chronical fistulae in abomasum have been investigated. Two electrode pH-probe has been used for measures. Atropine sulphate (0,06 mg kg*[-1) IV infusion) has been used to stop function of n.vagus, and cimetidine (0.16 mg kg*[-1) IV infusion) to block humoral regulation. The results clearly show that both, atropine sulphate and cimetidine, demonstrate some blocking influence on the HCL of abomasum in calves of different age.

The quality of forage grass mostly depends on the harvesting time. In early vegetation stages, grasses have a high protein and energy content and high dry matter digestibility. The data on the protein content and energy value of different grasses gives a possibility to choose the best conservation method. Changes in the chemical composition of perennial grasses during the vegetation were investigated at the Laboratory of Biochemistry of the LUA Research Centre "Sigra". The dynamics of the content of amino acids was evaluated.

During the last decade economy of Latvia has experienced a decrease, crises and also depression. Further development process of Latvia could lead to a rapid economical boom. The application of scientific researches into the development of nationaly economy of Latvia is one of the important aspects. Though the globalisation and commercalisation of scientific researches must be taken into account as well. Science development is opening wide range of possibilitities for research perfection. Most of the Latvian, Lithuanian and Slovakian entrepreneurs are 30-40 years old, who suddenly appeared in the circumstances of conventionally free economy in their twenties.

It is very important to use the exact investment model for energy enterprises. Giant investment is necessary for establishing continued energy systems using renewable energy resources. Demand of the heat energy usually is higher in a winter period compare to the summer time. Program combinations of different heating modus are researched using EnergyPRO.

This paper deals with the results of focus group discussions concerning the Baltic Pulp project carried out among inhabitants of Jekabpils district in February and March 2001. Group discussions were a base for qualitative analysis where differences between opinion within different social groups had been fixed. This gives an insight into opinions as well as suggestions concerning ecological, economical and social factors, connected to the planned pulp mill.