The EU Directive on the promotion of the use of biofuels or other renewable fuels for transport (CO M 2003/30/EC) states that the proportion of biofuels in 2010 must make 5.75% of non-renewable fuels, but in 2020 - 10%. The only way for Latvia to fulfil the Directive 2003/30/EC is to use winter rye because it is one of the oldest cereals grown in Latvia, and Latvia has a long-lasting experience in growing it. A field trial of winter rye (Secale cereale L.) was arranged in the Agricultural Science Centre of Latgale from 2005 to 2007. The influence of four winter rye varieties and five fertilizer rates on grain yield and starch content was researched for three years. The year (factor A), the varieties (factor B), the fertilizer rates (factor C), and the interaction of factors AB, AC , BC, and ABC significantly influenced the yield of grain and the starch content with 95% probability. It is recommended to use good quality grain with high starch content and low protein content for bioethanol production. The varieties of winter rye 'Kaupo', 'Amilo', and 'Walet' are the most suitable for ethanol production in Latgale region.

Sour cherries become more popular due to their food value. Therefore sour cherries could be a profitable crop for fruit growers in Latvia. Information about sour cherry response to soil moisture adjustment is needed, because based on previous studies it is not possible to predict the influence of irrigation and mulch on sour cherry growing. The trial was carried out at the Latvia State Institute of Fruit Growing in 2007 to determine the effect of soil moisture adjustment on the growth of different sour cherry cultivars. Woodchip mulch and drip irrigation were used as main factors, cultivars 'Bulatnikovskaya', 'Desertnaya Morozovoi', 'Latvijas Zemais', 'Orlica', 'Shokoladnica', 'Tamaris', 'Zentenes' were used as a secondary factor. Vegetative growth, branching angles of lateral shoots, proportions of pruned shoots, spurs and twigs were determined to characterize the response of cultivars to mulching and irrigation. In general use of drip irrigation increased vegetative growth of sour cherries, but the use of woodchip mulch decreased this growth. Branching angles were wider in variant with woodchip mulch. Cultivar 'Zentenes' most positively responded to use of woodchip mulch and drip irrigation.

Willows (Salix sp.) and reed canary grass (Phalaris arundinecea L.) (RCG) are fast growing perennial energy crop and potential cultures for recovering of cutaway peat lands. Cut away peat land soils are characterized by high acidity (pHKCl 2-3), high NH4**+1, and lack of P and K. Wood ash could be good liming agent and resource of potassium. Waste water sewage sludge (WWSS) compost is effective fertilizer and source of phosphorus. The objective of the study was to investigate the effect of application of WWSS compost and wood ash fertilizers of different doses on ingrown of willow cuttings and RCG in potted cultures. The wood ash addition of 10 g lE-1 and 20 g lE-1 to WWSS compost mix with peat from used query in proportions 1:1 and 4:1 were tested. The length of shoots and dry mass of shoots and roots were assessed to determine the effect of fertilization on growth of crops. Chemical analyses of growing media were performed to determine the content of main nutrient elements and pHKCl changes during season. The positive effect of fertilization on growth of crops was observed - an optimum dose for willows is (10 g lE-1) equivalent to 10 tDM haE-1 wood ash with mix of WWSS compost with peat. RCG produces more biomass in growing media containing largest doses of wood ash and WWSS compost premix. The willows produced bigger amount of biomass and accumulated more nutrients from growing media than RCG.

The yield and quality (volume weight, 1000 kernel weight, protein content, falling number, gluten content, gluten index, gluten content in dry matter) of winter wheat was studied in variety 'Portal'. The wheat was part of the five-year crop rotation experiment where red clover (Trifolium pratense L.), winter wheat (Triticum aestivum L.), peas (Pisum sativum L.), potato (Solanum tuberosum L.) and barley (Hordeum vulgare L.) were following each other. There were two production variants which followed the crop rotation. In one variant mineral fertilizers and pesticides were used, and the other variant was conversion to organic without any synthetic agrochemicals. In mineral fertilizing variant, on the background of P25 and K95 kg haE-1 the N amount varied from 0 to 150 kg haE-1 and herbicide Mustang (preparation norm 0.5 L haE-1, active substance florasulam, 6.25 g LE-1; 2.4-D, 300 g LE-1), insecticide Fastac 50 (preparation norm 0.2 L haE-1, active substance 50 g LE-1 alphacypermethrin) fungicide Falcon EC 460 (preparation norm 0.4 L haE-1, active substances 167 g tebuconazole, 250 g spiroxamine, 43 g triadimenol) and growth regulator Moddus (preparation norm 0.4 L haE-1, active substance 250 g LE-1 trinexapac-ethyl) were used. In conversion to organic the winter wheat grains which followed the red clovers after effect had higher volume weight, 1000 kernel weight and gluten index compared to the variants where mineral fertilizers were used. The yield, protein content, falling number and gluten content in dry matter increased with increase of the amount of mineral N. The wet gluten content was significantly higher compared to the other variants where the N amount was 50 kg haE-1.

Wood based ash can be used as a liming material and fertilizer in forest, thus providing a solution for utilization of wood ash and formation of additional increment of trees, especially on organic soils, where lack of potassium and phosphorus is a well-known factor limiting the growth of trees. Yet, many studies have been made with adverse results mostly because of different soil types and species investigated. However, by now the best results on fertilization with wood ash have been found on drained peatlands, where some nutrient deficiencies have emerged. The aim of this study was to find out the growth response of Norway spruce on drained organic soils after spreading of potassium sulphate (K2SO4) and wood ash (WA). The experiment was carried out in three middle aged Norway spruce (Picea abies) stands on drained mineral and peat soil. Experiment consisted of three replications of each treatment in each stand including WA, K2SO4 and the control on 400 square meter sub-sample plots each. The diameter and height of trees were measured. The samples of increment cores were collected 4 years after fertilization to determine the additional volume increment, which varied from 8.5 m**3 haE-1 in WA plots and from 9.7 m**3 ha-1 to 17.2 m**3 haE-1 on K2SO4 plots. Both - the wood ash and potassium application - significantly increased the increment of Norway spruce on drained mineral and peat soil, although no significant differences were found between the treatments (p = 0.82, α = 0.05).

The research was conducted during the period of 2007-2011 in the fields fertilized by manure of pig breeding complex. According to the fertilization value of manure, the following total nitrogen levels reached the fields each year: 2007 – 169, 2008 – 167, 2009 - 168, 2010 - 168, 2011 – 168 kg haE-1. Ptotal reached the fertilized fields accordingly: 2007 – 9.4, 2008 – 18.9, 2009 – 12.0, 2010 – 10.8, 2011 – 13.5 kg haE-1. The aim of the research was to explore the impact of manure fertilized fields of a pig breeding complex on the water quality of streams. Streams, flowing through fields fertilized with manure, are usually polluted with nitrogen. The increase in Ntotal concentrations in streams’ water below fertilized fields was affected by precipitation (r = -0.31), fertilization rate (r = 0.41) as well as mineral nitrogen reserves in the soil (r = 0.20). Phosphorus concentrations in streams’ water were low and corresponded to a very good streams’ water ecological condition, except in times, when the water inflowing into the fertilized fields was already contaminated with this element. It was determined that an extremely high impact on streams’ water quality below fertilized fields comes from Ptotal concentration in streams’ water above fertilized fields (r = 0.91) as well as from the drainage water inflowing from fertilized fields into the streams (r = 0.71). Neither Ntotal, nor Ptotal pollution was observed in drainage water, because the highest concentrations during the research period were lower than the maximum allowable concentrations by 1.1 and 6.5 times respectively.

The investigations were carried out during the period 2006-2011 in the land of the Water resources management institute of ASU, in the village of Lipliūnai on Endocalcari Endohypogleyic Cambisol (CMg-n-w-can). The base of investigations is 3 drainage systems, which contain cereals differing in fertilization and grass crop rotations. The aim of investigations is to determine the crop rotations differing in fertilization and these relations with cycles of phosphorus in agroecosystem. Higher productive was perennial grass crop rotation. In the conditions of cereal crop rotations this productive was 3-46% lesser. The highest concentration of P-PO4 3- in drainage water was received in the conditions of higher fertilization cereals crop rotation while highest concentration of total P was in the conditions of grass crop rotation. The concentration of P-PO4 3- in drainage water essentially depends on amount of mobile P2 O5 in soil, fertilization, productivity of field crops, drainage runoff as well as cumulative balance of P. The highest leaching of P-PO4 3- and total P by drainage was received under the conditions of higher fertilization cereals crop rotation. The leaching of P-PO4 3- essentially depends on fertilization, drainage runoff as well as cumulative and yearly balance of P. The application of all crop rotations was distinguished by positive P balance.

To promote the future of abandoned lands management and the reduction of fossil energy consumption in Latvia, the establishment of energy crops plantation facilities, including perennial grasses, was investigated. The objective – suitability of several perennial grasses for bio-energy production under condition of Latvia. The aim of the current research to evaluate the experimental field conditions for the cultivation of perennial grasses. The perennial grasses are modest in terms of soil conditions, they are environmentally friendly, as well as provide high yields of biomass with adequate quality for bio-energy production without large investments. With increasing amounts of bio-energy production the amounts of various by-products which are profitable to utilize as energy crops fertiliser will also increase. It is essential that plant nutrients return back into circulation by creating a complete cycle. In order to test in practice the possibility of creating this complete cycle of growing perennial grasses, an experimental field was chosen at the Research Institute of Agriculture in Skriveri. In the summer of 2011, before trials establishment, the conditions of soil were examined at four depths: 0 – 20 cm; 20 – 40 cm; 40 – 60 cm and 60 – 80 cm. The analyses showed that the experimental field conditions were appropriate for growing of perennial grasses. The results of the soil agrochemical analysis will be a base for future studies of usage efficiency of different fertiliser types on perennial grass productivity and nutrient recycling opportunities in energy crop plantations.

Abstract Studies comparing slurry injection versus spreading have reported inconsistent results so far. The objective of the study was to compare two slurry application methods, injecting and spreading, in terms of influence on sward yields and leaching of nitrogen (N) and potassium (K) from grassland. The experiment was conducted from 2008 to 2011 at the Eerika Experimental Station, Estonian University of Life Sciences. Mini-lysimeters filled with loamy sand soil embedded in three swards (three-species grass mixture (Phleum pratense, Lolium perenne and Poa pratensis), grasses mixture with white clover (Trifolium repens), and grasses mixture with lucerne (Medicago sativa)) were used. Three annual nitrogen rates (60, 120, 180 kg haE-1) in conjunction with the two slurry application methods (injecting and spreading) were applied. Percolated water quantities, N and K content in leachate and the sward yield were measured. N leaching was significantly less with slurry injection while K leaching did not depend on slurry application method. N and K leaching was more affected by sward botanical composition and applied N rate and N:K ratio n slurry than by slurry application method. Sward yields did not depend significantly on slurry application method. Slurry injection is rational only in grasses sward when used N rates are above 120 kg haE-1 yrE-1. Slurry injection may have negative influence on the distribution of white clover in the grasses + white clover sward and thus lead to sward yield decrease.

Bioenergy production growth rates in the recent years are leading to waste – digestate and wood ash amount increases, which are essential to be managed in the most efficient and safe way. In the formation of plant nutrient recycling these waste products are useful to be included in the energy crop fertilisation plan. In order to study the waste products application options for energy crops – reed canary grass (Phalaris arundinacea L.) and festulolium (×Festulolium pabulare) fertilisation trials were arranged in 2012 at the Skriveri Latvian University of Agriculture (LLU) Research Institute of Agriculture. In all fertiliser treatments: wood ash; digestate one time per season; digestate two times per season and mineral fertilisers the same doses of the main plant nutrients (N, P, K) were provided, the missing quantities of elements compensating with mineral fertilisers. To obtain the grass biomass, two cutting regimes were used – two-cut and one-cut harvest system. This article summarizes the findings on the productivity of the 1st year of use grassland swards and sward structure data. The productivity of perennial grass biomass was dependent on the type of applied fertilisers, grass species and cutting regime. In the first production year the highest average dry matter yield (7.30 t haE-1) was produced by reed canary grass. The highest DM yields in average for both grass species were obtained by mowing once per season – in autumn at crop senescence (7.01 t haE-1) and in fertilisation treatments of wood ash (WA) – 8.06 t haE-1 and mineral fertilisers (MF) – 7.24 t haE-1.