Volume 32 (2014): Edition 1 (December 2014)

Traditionally forest resources are estimated in each compartment or stand with ocular standwise forest inventory. However, this inventory technique has shortages with measurement accuracy. In the study the accuracy of the standwise forest inventory was estimated by comparing the growing stock volume of the standwise inventory with the accurate (instrumental) re-measurements. Comparison was done with 4515 mature stands of pine (Pinus sylvestris L.), spruce (Picea abies (L.) Karst.), birch (Betula spp.), aspen (Populus tremula L.) and black alder (Alnus glutinosa L.). The stands’ measurements by callipers or by harvesters (recalculated to growing stock volume) were used for accurate re-measurements. The study results show that the volume of standwise forest inventory have relative bias of 17.6% (volume is underestimated by 17.6%) and relative root mean square error 27.5 % for the whole data. Spruce stands are more accurately measured and black alder stands - inaccurately. The accuracy of pine, birch and mixed stands was similar to overall trends. Stands with volume 200 - 300 m³ ha^-1 are more accurately measured and stands with the volume less than 200 m³ ha^-1 - most inaccurately. The accuracy of stands with the volume more than 300 m³ ha^-1, decreases by increasing the volume of stands. The volume estimation of individual species has different trends in standwise forest inventory. The volume of pine and birch is overestimated and the volume of spruce, aspen and black alder is underestimated.

The lack of suitable plum rootstocks for Baltic conditions has become a problem during recent years due to changing climatic conditions. Rapid temperature fluctuations between freezing and thawing are occurring more frequently. The winter-hardiness of rootstocks is essential for overwintering of trees in such conditions. The content of accumulated reducing sugars is an important physiological factor influencing wintering ability of trees. The dynamics of reducing sugars was investigated during two winter seasons (2010/2011 and 2011/2012) in one-year-old ‘Kubanskaya Kometa’ (Prunus x rossica Erem.) hybrid plum shoots from two orchards planted in 2001 at Pūre Horticultural Research Centre (Latvia) and Polli Horticultural Research Centre (Estonia). Cultivar ‘Kubanskaya Kometa’ was grafted on eight clonal rootstocks: ‘St. Julien A’, ‘Brompton’ cuttings, ‘Ackermann’, ‘Pixy’, GF8/1, G5/22, GF655/2, ‘Hamyra’ and eight seedling rootstocks: ‘St. Julien INRA 2’, ‘St. Julien d’Orleans’, ‘St. Julien Noir’, ‘Brompton’ seedlings, ‘Wangenheims Zwetsche’, ‘St. Julien Wädenswill’, ‘Myrobаlan’ and Prunus cerasifera var. divaricata. Trees were planted at 5×3 m spacing in four replications per rootstock with three trees per plot. Shoot samples were harvested five times during the winter period. The concentration of reducing sugars (mg g^-1 dry weight) was determined with Bertran’s method. Significant differences in concentration of reducing sugar were found between samples coming from different locations and in two seasons. The maximum concentration of reducing sugar was found in December or January depending on growing location and meteorological conditions

Production of refuse derived fuel from municipal solid waste in future shall play a strategic role in an integrated waste management system. The amount of landfilled biodegradable materials thus will be diminished according to provisions of the 1999 Waste Landfill Directive. The aim of this article is to evaluate cost effectiveness based on cost evaluation of the different complication of the waste pre-treatment equipment complectation and based on regenerable waste quantities in Latvia. The comparison of cost estimates is done in 3 scenarios considering potential waste quantities in Latvia: Scenario I - planned annual waste quantity is 20 kT; Scenario II - 40 kT and Scenario III - 160 kT. An increase in amount of waste and processing capacity means the decrease in costs of mechanical pre-treatment of 1 ton of waste. Thus, costs of mechanical sorting line under different scenarios with capacities of 10 t h^-1, 20 t h^-1 and 80 t h^-1 are EUR 32 per t, EUR 24 per t and EUR 15 per t, respectively. Most feasible cost for a set of mechanical pre-treatment equipment for the capacity of 10 t h^-1 is EUR 32 per t by using rotating drum screener with the following manual sorting. Mechanical pre-treatment equipment of unsorted municipal waste is economically nonbeneficial, when the use of fine (biologically degradable) fraction is not possible. As the sorting of biodegradable kitchen waste is not developed under the current waste management system in Latvia, the lines for mechanical pre-treatment of household waste would be better to install in landfills.

Commercial products with humic substances have often been recommended for plant growth stimulation and yield improvement. The aim of this study was to clarify the effects of two products, containing cavited peat and vermicompost respectively on the soil biological activity. Vegetation experiments with garden cress and cucumbers were arranged in pots with a peat substratum in the greenhouses of the Latvia University of Agriculture. The plants were treated with the preparations once a month. The first treatment was done at sowing. Dose of 20, 2, 0.2 mL per m² during each treatment time were used. A control variant was without peat or vermicompost preparation. Field experiments with onions were carried out in the organic farming experimental field of the Latvia State Institute of Cereal Breeding. Plant growth and soil (substratum) biological activity (respiration and enzymatic activity) were tested. Plant growth and response to the different preparations depended on the plant species and its development stage. The effect of preparations decreases during plant development. The impact of peat or vermicompost preparation on soil biological activity depended not only on the concentration of preparation, but was influenced by the soil or growth media type. The decrease of onion yield in field conditions as a result of preparations was observed.

Milk composition is of prime economic importance for farmers. Milk total proteins are composed of casein, whey proteins and non-protein nitrogen. The objective of this work was to establish milk crude protein, non-protein nitrogen (NPN) and urea content in dairy cow milk produced in different farms in Latvia. Cow milk samples (n=30) were collected in September 2012 from four different farms breeding diverse cow breeds. Average crude protein, casein and urea content in milk varied significantly among farms. NPN content in cow milk varies among farms - from 0.194% to 0.232%. Average crude protein and casein content was significantly higher (p<0.05) for Latvia Brown breed cows, while NPN content did not differ significantly among breeds. Regression between NPN and urea content in milk was R² = 0.458. Correlation between NPN and urea content was significant (r = 0.677). This study allowed establishing that crude protein and NPN content in milk varied significantly (p<0.05) in farms with differing dairy cow housing and feeding technologies

Cereal yield loss from eyespot directly depends on the severity of the disease. The aim of this study was to establish the relationship between eyespot damage in winter wheat and components of yield of winter wheat cultivars Ada, Mulan and Tukan in Lithuania in the 2011/2012 cropping season. Several eyespot did not decrease the grain number per ear cv. of Tukan while for cvs. Ada and Mulan the decrease was 14 and 15%, respectively; however, the grain number per ear of moderately eyespot-affected stems of cv. Ada did not differ from that of visually healthy stems. For cv. Ada, the grain weight per ear of moderately affected stems was 5.8% less and that of severely affected stems was 12.8% less than that of healthy stems, while for cv. Mulan the decrease in grain weight per ear was 40.3 and 35.5%, respectively and for cv. Tukan it was 59.0 and 63.2%, respectively for moderately and severely affected stems. The decrease in thousand grain weight of moderately eyespot-affected stems of cv. Ada was less (6.5%) compared with that of cv. Mulan (31.3%) and cv. Tukan (55.8%). Thousand grain weight of severely eyespot-affected stems of cvs. Ada, Mulan and Tukan was 22.2, 26.0, and 65.0%, respectively, less than that of healthy stems. Screening of healthy, moderately and severely affected plants of the winter wheat varieties Ada, Mulan and Tukan for grain number per ear, grain weight per ear and TGW revealed that these varieties differed in tolerance to eyespot

Changes in Fusarium species composition from naturally contaminated spring and winter wheat grain from the years 2005-2007 to 2011-2013 are presented. In general, Fusarium infection spring wheat grain was much more frequent than in winter wheat. In 2005-2007 F. avenaceum was dominant in both crops, with F. sporotrichioides, F. poae and F. culmorum isolated at lower levels, and F. graminearum, F. tricinctum, F. equiseti and F. oxysporum were occasionally found on both spring ant winter wheat. In 2011-2013, F. avenaceum lost its dominating status among Fusarium isolates in both crops, but the species composition of most frequently isolated fusaria in spring and winter wheat was quite different: F. graminearum, F. sporotrichioides, F. culmorum and F. avenaceum constituted the major part of fusaria isolated from spring wheat grain, while in winter wheat F. poae, F. sportotrichooides and the declining F. avenaceum were dominant.