It is important to define which of the plant growth factors determines the yield level. During recent years in Latvia, in most cases it was moisture. Grain yield level mostly depends on meteorological conditions during the tillering stage. Plants do not utilize all water from precipitation. Rain water efficacy depends on soil granulometric composition and content of humus. Humus content could be considered as regulated factor. Important is also distribution of precipitation during the vegetation period as well as run-off of rain water which depends on micro-relief, soil tillage type, and direction in accordance with the slope gradient. It is very important for cereal growing in what conditions tillering is done, because during that time productive stems as well as ear sprouts are formed. The aim of this research was to determine the effect of soil moisture on the growth and development of winter wheat Triticum aestivum L. Field trials were carried out during 2005-2007 in Kurpnieki field at the Research and Study farm „Vecauce” of the Latvia University of Agriculture. A total of 47 points (distributed as a grid of 50×50 m) were selected for sampling in the winter wheat field. In both experimental years, the increasing soil moisture in spring had a significant positive effect on the flag leaf area, which, in its turn, increased also the level of grain yield. Partial correlation analysis showed that exclusion of organic matter content and altitude above the sea level as factors, changes soil moisture at different layers of the soil insignificantly.

Modern varieties developed under conventional plant breeding programs do not always perform well under organic and low-input growing conditions. Therefore, organic farmers need varieties adapted to variable environmental conditions. This means emphasis on traits such as nutrient uptake and use efficiency, good weed suppression ability and disease resistance and can be achieved via extended genetic diversity within the varieties: variety mixtures and populations of self-pollinating crops. The aim of the present study was to review published scientific literature about importance and research results on this topic. Scientific articles about the necessity of such studies and results of investigations performed in different countries have been studied. The main results show that variety mixtures have advantages in terms of disease control and yield stabilization and performance of mixtures may be affected by various factors – choice of components and its number, interactions between plants of components, manner of the mixing and growing technology. Depending on parental material, populations contain greater genetic diversity than variety mixtures. There are trends observed in the studies that yield of populations increased over generations and they are more stable than modern varieties, but there is no evidence that they would be significantly more productive. This research direction has recently become topical and is not sufficiently widely covered in the world agricultural science. The obtained results are inconsistent.

The objective of the current research was to investigate effects of germination on chemical composition of hull-less barley (Hordeum vulgare L. var. nudum Hook. f.), hull-less oat (Avena sativa), rye (Secale spp.), and wheat (Triticum spp.) grains for comparison. All the grains were cleaned, washed, steeped and germinated at temperature 35 ± 2 °C and relative humidity 95 ± 2% for 12, 24, 36, and 48 hours. After germination grains were dried till moisture content 14 ± 2%. Main quality parameters such as starch, proteins, b-glucan (in hull-less barley) and individual sugars were determined in cereals during their steeping and germination. Non-germinated grains were used as a control sample. In the present experiments non-significant protein content increase was observed in the analysed hull-less barley, hull-less oat, rye, and wheat during their germination for 48 hours. Starch content in hull-less barley, wheat and rye grains decreased non-significantly during germination for 24 h; opposite results were obtained for hull-less oat grains, where content of starch decreased by 16.7% after steeping and by 26.4% after germination for 24 h. b-glucan content in hull-less barley grains after germination for 48 h decreased by 20.5%. Non-significant changes were obtained in fructose content in analysed cereal grains during germination for 48 h; it was significantly increased after germination for 24 h and in germination for 48 h. Non-significant sucrose content changes were observed in hull-less barley, rye and wheat grains during germination for 12 h and in hull-less oat grains – for 24 h significantly increasing in future germination for 48 h.

After regaining independence the agricultural production in Estonia has undergone a drastic decline. Due to the inadequate application of fertilizers and pesticides, the yield of field crops and grasslands has decreased 1-7 % per year. The balance of nitrogen in the arable soils is negative, particularly respecting fodder crops. At present, in Estonia most of grasslands are practically not fertilized, or they are fertilized in the last order. The amount of nitrogen removed with the yield of fodder crops, cereals and potato are by 45, 20 and 17 kg ha*[-1) higher, respectively, compared with the amounts of N applied to the soil with organic and mineral fertilizers, available for those crops. The effectiveness of nitrogen fertilizers depends largely on weather conditions during the vegetation period and is the lower, the higher is soil humus content. On gleyic and gley soils, whose humus content is higher, the efficiency of nitrogen fertilizers is 2-3 times lower and the agroecological and economic fertilization risks are higher. On sown grasslands, the efficiency of nitrogen fertilizers depends not so much on soil fertility as on soil water supply, humus content and grass sward type. With proper application of fertilizers, use of suitable plant species and varieties, it is possible to increase significantly not only the yield per unit area but also its nutritive value.

Production of cereals is mostly processed by operating the machinery. Operation of machinery influences the yield, i.e. also the income on one side, but it is also one of the biggest sources of expenses from the other side. Increasing the yearly operation time and amount of work of the machinery leads to decreasing costs per unit. Increasing the yearly amount of work is limited by agrotechnical terms. The crop yield depends on the time and duration of field work, and affects the farm income. The methods and formulae to prognosticate the averageoptimum yearly operation time of farm's machinery, i.e. also farm's cereal-growing area was composed by the author, concerning biological, technical and economical factors and relations, affecting cereal production. Farm profit and profitability were used as optimization criteria.

The epidemiology of barley yellow dwarf disease is highly complex, involving numerous interactions between the abiotic environment and the crop, virus and vector - components of the disease. Barley yellow dwarf is the most economically damaging virus disease of grass and cereal crops worldwide. The disease identified as BYD has been reported in all countries in Europe causing losses on barley and oats, wheat and maize; losses on grasses are recognized but more difficult to quantify. There are five different strains of viruses causing BYD disease and all of them induce similar symptoms of chlorosis and stunting in graminaceous hosts. This report represents an overview of system components and their interactions in the epidemiology of barley yellow dwarf disease. As the main components considered here are aphids - (the only vectors of these viruses), host plants and viruses causing BYD disease. Some aspects of interactions between these components are also discussed.

The importance of organic farming has increased rapidly in Estonia in the last few years. Nevertheless the higher prices of organic products are not presented in Estonia yet, but the official subsidies are often the main reason to start organic farming. The Estonian Republic supports organic farming as a branch of environmentally sustainable agriculture. The main theme of this article was to explain - is the organic cereal production profitable for farmers.