One of the most serious diseases of the potato crop worldwide is late blight caused by Phytophthora infestans (Mont.) de Bary. Most growers control the disease by applying fungicides at regular intervals of 8-10 days from the time of row closing until the end of the growing season. The NEGFRY model is used for timing the chemical control of potato late blight. The NEGFRY model is based on two existing models, the "negative prognosis", for forecasting the risk of primary attacks, and a model for timing subsequent fungicide applications during the season. The main objective of NEGFRY is to get high yield and quality with minimum use of fungicides. Present work underlies the experiments that were arranged in 2000 and 2001 at the Jogeva Plant Breeding Institute. Two potato varieties with different resistance to late blight were taken to the experiment in both years: susceptible 'Adora' and modarately resistant 'Anti' in the year 2000 and susceptible 'Berber' and 'Anti' in 2001. NEGFRY gave highest economical effect among six tested treatment regimes.

Evaluation of virulences of Blumeria graminis f.sp. hordei was started in Latvia in 1981, first in the Baltic States. Until 1994 the observations were carried out only in the central part of Latvia - Salaspils. As the climatic factors and the used barley varieties in various parts of Latvia are different, in 1995 we started regular observations of the particularities of the genetic structure of the pathogen population also in Daugavpils. The aim of this investigation was to detect particularities of the genetic structure of the pathogen population in different parts of Latvia in 1996-2000.

In order to identify the quality of natural Silver birch stands in Latvia, fifteen sample plots covering all country's regions were established. Stem quality affecting morphological traits - stem straightness, branch angle, branching thickness and branching patterns were measured and assessed to all birches in sample plots. To compare the stand's quality, the integral quality indicator was introduced. According to results obtained in plots, most quality birch stands in Latvia are located in East and North parts of Latvia. The best stands proved to be in Aluksne and Smiltene. Birch stands in West part of Latvia had stems of substantially lower quality. The best quality stand in this region was birch stand located in Tukuma's head forestry.

The goal of the present research was to study formation of the productivity of perennial ryegrass at different rates of mineral fertiliser use. Field experiments were carried out on Sod-Podzolic soils during 1999-2001. The following mineral fertiliser rates were used: N and P205 each - 0, 30, 60, 90, 120 kg ha*[-1); K20 - 0, 40, 80, 120, 160 kg ha*[-1). The productivity of DM and seeds was dependent on genetic characteristics of the particular variety, on the rates of mineral fertiliser and as well as on the meteorological conditions prevailing in each investigation year. The average DM yield, depending on the particular variety, constituted 2.21-6.07 t ha*[-1), and the average seed yields were 255-672 and 133-400 kg ha*[-1) in 1st and 2nd years of stand uses, respectively.

Flooding of Nemunas floodplain preserves the natural retention capacity of pollutants in water of the main canal as well as improves farming conditions on the inundated meadows of the valley. It was established that nitrogen concentration was decreasing by 20-50 % causing self - purification process on the flooded meadows. Nitrogen retention is mostly observed in the zones of stagnant water. It depends on the velocities of flood current. Heavy metals and nutrients are absorbed by tiny clay and silt particles deposited in the meadows. By the means of mathematical modelling it was established that about 37% of suspended sediments deposited in the flood plain. During the study period (1950-1991), the soils in the valley were covered by 50-60 t ha*[-1) of deposits and were naturally fertilised with 250 t of potassium, 950 t of phosphorus, 38.000 t of calcium and 147.000 t of organic matter saturated with nitrogen. In order to increase those quantities it would be efficient to increase the water discharge and bush cover in the Delta.

The author of this publication offers to analyse and appraise development problems of a pupil's personality in pedagogical environment. This ensures respect for the holistic principle in scientific investigation. Pupil's qualities of personality, its structure and advance, dynamics of development, in the author's opinion, are necessary to be investigated not only in different separate spheres of their activity and manifestation, but in a unity determined by the holistic principle in pedagogy. The development of a personality takes place through interaction with the environment. The aim of the publication is to present a characteristic of interaction between a pupil's personality and rural school as a pedagogical environment in the context of topicality, contradictions, tendencies and problems in today's education.

Agriculture more than any other branch of production is influenced by various natural, anthropogenic and economic risk factors on which the profitability of production and preservation of the environment in rural areas depend. The prerequisite of prevention or alleviation of risks is their all-round knowledge and consideration. In order to understand the nature of risks, they will be dealt with in the present study on the example of the cultivation of the most common cereal in Estonia - barley. The difference in barley yields, resulting from the pedoclimatic coditions of Estonia, may be 2-4-fold in different regions and in different years. At the same time, differences in the profitability of barley cultivation, depending on economic factors and on the specificity of production, may be up to 6-fold.

Training of a vocational teacher at a professional education oriented university is in parallels to concentric integration of profession and pedagogic (psychology) resulting in formation of student's professional consciousness that ensures a new quality of professional orientation.

Weed surveys showed that annual broad-leaved weeds were dominant in spring barley sowings in central Latvia. Field trials on broad-leaved weed control in spring barley showed that herbicides Granstar and Duplosan Super at 0,5 and 0,25 doses gave good weed control. There were statistically significant relationships between the abundance of broad-leaved weed and the yield of spring barley when barley yield and broad-leaved weed population were both high.