Wood-based ash landfilling is increasing issue not only in Latvia but in the whole world as more biomass is used for energy production. Utilization of wood burning waste as fertilizer is already used worldwide, but there is lack of information about chemical composition of wood ash obtained from Latvia plants, so the aim of this study was to determine chemical composition and analyse possible utilization options of wood-based ash from Latvia plants. Therefore wood ash samples from 53 companies were collected, sieved and chemical composition of samples was determined. It was concluded that within higher capacity of furnace more coarse fraction of wood ash was observed which is less valuable as fertilizer. Wood ash is good liming material consisting alkali compounds and other biogenic elements but also heavy metals, which are pollutants and could cause environmental problems.

The growth data and the potential returns from 15-year-old plantations of pine Pinus sylvestris L. (6 trial sites), spruce Picea abies Karst L. (9 trial sites) and silver birch Betula pendula Roth (13 trial sites), established in abandoned agricultural lands in a variety of soil types (sod calcareous, anthrosols, podzolic, podzols, gley, podzolic gley, alluvial), using the planting density 2,500 and 3,300 and also 5,000 trees/ha are analysed.For tree plantations in agricultural soils (alluvial sod-gley, gley-sod podzolic, sod-podzolic gley, typic podzol) at the survival of 80-98% the stock volume for 15-year pine is as high as 102-155 m³ha⁻¹ with the volume growth 5.72-8.94 m³ha⁻¹ per year; the same indices for spruce in agricultural soils (gley sod-calcareous, sodpodzolic, cultivated, sod-podzolic gley, alluvial sod-gley, base-unsaturated brown) are 75-98 m³ha⁻¹ and 10.26-15.76 m³ha⁻¹, respectively. For 15-year plantation birch the mentioned indices may vary from 61 to 169 m³ha⁻¹ and from 7.54 to 29.82 m³ha⁻¹ per year. The lowest volume growth (4.66 m³ha⁻¹ per year) is for birch in heavy clay soil (gleyic sod-podzolic), the highest (29.72-29.82 m³ha⁻¹ per year) – in cultivated soils and pseudogley soil.Plantation cultivation of pine, spruce and birch in agricultural lands may by the age of 15 years yield with a profit such forest products as pulpwood, fire wood and woody biomass. The gross income gained from first commercial thinnings of plantation pine, utilizing pulpwood, fire wood and logging residue biomass, may vary from 679-2267 EUR ha⁻¹, for spruce the same indices are 1644-3272 EUR ha⁻¹, for birch - 683-2188 EUR ha⁻¹.

The main aim of this paper is to fuzzify the kinetic parameters, which have crisp nature, in order to obtain the realistic and accurate results. In the present study, the variance, upper limit of ‘dE’ and the frequency factor are assumed to be fuzzy numbers. The Gaussian distribution is considered as the distribution function, f (E), of Distributed Activation Energy Model (DAEM). The membership and the non-membership functions are evaluated by the trapezoidal fuzzy number. Thermo-analytical data has been found experimentally with the help of TGA/DTG analysis. The approximated solution of DAEM is obtained with the help of asymptotic expansion.

Three treatments were tested with four replications at RCBD, namely cassava monoculture, corn twice under cassava intercropping, and corn with corn monoculture where the second corn was planted 5 days after harvested. Planting distance of cassava in monoculture was 100x100 cm, and in intercropping was 200x50 cm, by which corn was planted in 50x30 cm, 1 seed per hole. All plots received dairy cattle manure 5 t haE-1. Fertilizer applied for cassava was Urea 100 kg haE-1, Ponska 200 kg haE-1 and KCl 100 kg haE-1 split into two applications two weeks after cassava planting, then when first of corn was harvested. Corn fertilization was Ponska 150 kg haE-1 + Urea 100 kg haE-1 every 3 months and split into two applications: 1 week and 4 weeks after corn was planted. Cassava and twice corn fertilization was Urea 300 kg haE-1 + Phonska 400 kg haE-1 + KCl 100 kg haE-1. Results showed that cassava monoculture can be improved by inserting of twice corn in between rows. Under sole cropping cassava, the B/C ratio was the highest 1.61, however with incorporating twice of corn the B/C ratio was 1.58. Intercropping cassava and twice of corn resulted in the Land Equivalent Ratio 2.146. By intercropping cassava with corn twice at the end of dry season, there was an opportunity to find corn biomass for dairy cattle. Under intercropping, cassava was able to produce 21.5 t haE-1 of fresh roots, while first and second of corn produced fresh biomass of 34 t haE-1 and 28 t haE-1 respectively.

Climatic conditions for soybean cultivation in Latvia are challenging because of their variability. In addition, the sum of sunlight hours and the ratio of temperature and precipitation required to produce a quality crop are unpredictable. There is a risk that even early soybean varieties will not ripen due to weather conditions in a region. Studies show that soybean plants, including the green part of the crop, are well suited for animal nutrition prepared as hay or silage. The aim of this study was to evaluate the chemical composition of different soybean varieties harvested before ripening and assess them as hay or silage raw material. Weight, protein, fat, ash, fibre, acid detergent fibre (ADF) and neutral detergent fibre (NDF) of soybean varieties ‘Erica’, ‘Bolgar’ and ‘Viola’ green mass were determined at different stages of maturity. The results of the study showed a significant increase in protein (from 9.18% to 12.06%) and fat (from 1.18% to 4.40%) content of the dry matter variety ‘Bolgar’ from September to October. The protein content of the dry soya green mass was not affected by variety at the same developing stage but significantly changed among different stages of maturity. As the plant develops, the sucrose content in the green mass increases, the same as the total sugar content.

The article presents the results of studies of two samples of fenugreek: blue (Trigonella coerulea (Desr.) Ser.) and hay (Trigonella foenum graecum L.) on the set of economic, biological and biochemical parameters. The researched samples of fenugreek have a wide range of variability of indicators depending on the terms of sowing and weather conditions. More rapid development was shown by fenugreek species on the summer sowing dates (III decade of June) with a vegetation period of 36–37 days. To obtain a high yield of green mass of fenugreek plants, the early spring (II–III decade of April) and late spring (I decade of May) sowing terms were more suitable. The obtained green mass yield was: 5.7–6.9 t∙haE–1 – blue fenugreek, and 7.3–9.3 t∙haE–1 – hay fenugreek, with the content of the dry matter being 12.4–28.4%, the sum of sugars 2.5–5.0% and vitamin C – 38.0–51.8 mg∙(100 g)E−1. To obtain spices called “mushroom grass”, it is promising to use hay fenugreek with early spring (II–III decade of April) and late spring (I decade of May) terms of sowing, as a more developed vegetative mass is formed with the dry weight yield of plants 1.3–1.4 t∙haE–1. An increase in the amount of precipitation by 1 mm resulted in fluctuations of green mass yield from 15.0 to 77.3 kg∙haE–1 and dry mass yield from 0.693 to 25.9 kg∙haE–1.