Contamination of urban areas is directly connected with the lack of adequate waste management planning. Problems mostly arise in former military bases, garages, warehouses and areas with other facilities. For many decades environmental problems caused by pollution in areas of military use were not managed in Latvia. The aim of this research is to assess visual environmental quality and study heavy metal contents in soil of ‘Jaunais Mežaparks’ after demolishing works in the capital of Latvia – Riga, as well as to provide comparison to the former military ‘Daugavgrīva’ site. Research was carried out from November 2011 to February 2012 by soil sampling and further analysis and comparison of the heavy metal content in soil with target and boundary levels in legislation. ‘Jaunais Mežaparks’ is a former military area which is planned to be reused in future. The former military site is planned to be used as the residential neighborhood and is situated close to important recreational object in Mežaparks area – Lake Ķīšezers. According to Riga Development Plan old military sites must be remediated in accordance with environmental legislation if the contamination exceeds critical concentration values. Thus, this case study includes assessment of visual pollution as well as soil heavy metal contamination study. Recommended actions as well as direct remediation technologies to reduce the poisonous impact of contamination to environment in this area are proposed.

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.

Blueberry cultivation is becoming more and more popular in Latvia, and several commercial plantations have been established recently. Highbush blueberries (Vaccinium corymbosum L.) are perennial and can grow without replanting for 50 years; therefore a choice of soil and its preparation have a great role. This article summarizes results of research carried out in commercial blueberry plantation established in 2004 on loamy Haplic Cambisol. Soil properties, especially reaction and organic matter content, initially were not suitable for blueberry cultivation, therefore deep tillage and application of soil conditioner (acid sphagnum peat) were done before planting and similar peat mulch was applied every second year. Berry yield of 4 blueberry cultivars, soil properties and the nitrogen, phosphorous and potassium content in growing plant leaves were determined. The obtained results showed that sphagnum peat is an effective material for lowering of soil pH in plant root layer (0 – 40 cm). Data about plant nutrient content in topsoil and subsoil as well as in growing plant leaves will help to develop criteria for soil fertility assessment and diagnosis of plant nutrition.

The agronomic role of legumes in cropping systems is well understood with the respect to N2 fixation, mechanisms of precrop effects, and environmental impacts. The combined inoculation and tripartite symbiosis between leguminous plants, Rhizobium spp. and vesicular-arbuscular mycorrhizal fungi has been the subject of intensive research. Less attention has been paid to their effects on subsequent crops. Pot experiments were carried out in the greenhouse of Latvia University of Agriculture in 2015 and 2016. Soil used for this experiment was taken from the previous trial, where broad beans (Vicia faba var. major Harz.) were grown. Bean seeds, depending on the variant, were inoculated with rhizobia bacteria or mycorrhiza fungi, or the mixture of both microorganisms. Onions were grown as a subsequent crop. During the experiment, fresh and dry weight of onion leaves was determined. Onion root mycorrhizal colonization frequency and arbuscule abundance in the onion root system were determined. The activity of soil microorganisms was determined by soil respiration intensity. Results showed that the use of microsymbionts increased the subsequent onion leaf harvest in 2014 by 2.3% and in 2015 by 9.5%. In 2015 the highest increase of onion leaf yield was detected in variants were rhizobia strain RP023 was used. Rhizobia strain RV407 gave a positive effect only in combination with mycorrhiza fungi. Precrop treatment with mineral nitrogen fertilizer increased the onion yield in both years – by 12.4 and 14.3%, respectively. In all treatments, a decrease in dry matter content was observed. The highest incidence of mycorrhiza fungi structures was detected under mycorrhiza treatment. Tripartite symbiosis promoted the soil respiration rate.

Since the middle of the last century rapid intensification of agricultural production systems has resulted in dramatic increase in fertilizer consumption as fertilizer has been considered as one of the most important factors for increased yields. However, not all the nutrient ions in a fertilizer applied to soil are taken up by crops, thus certain amount of the applied fertilizer is lost from agricultural fields leading to increases in nitrogen surplus, nitrogen losses to the environment and harmful impacts on biodiversity, air and water quality. This study aims to focus on crop fertilisation planning which is based on the knowledge of physical and chemical properties of soil and involves performing soil tests, designing a fertilisation plan and its practical implementation as well as calculating the balance of N, and to evaluate crop fertilisation planning as a tool for achieving balanced economic and environmental benefits in crop farming, which play an important role in efficient farming. In this study, the authors have analysed current situation in Latvia regarding requirements for fertilization planning in crop farms and have assessed potential costs and benefits from fertilisation planning. The research finds out that total cost of introducing of fertilisation planning ranges from 34 to 22 EUR haE-1, however, fertilisation planning is a neutral measure where costs are compensated by savings from N inputs which ranges from 10 to 40 kg N haE-1.Fertilisation planning generates environmental benefits, i.e. – reduces direct N2 O emissions from agricultural soils by 47 – 187 kg CO2eq haE-1 through reduced N fertilizer inputs.

The objective of this study was to evaluate the main plant nutrient: mineral nitrogen (NH4 + -N and NO3 -N) dynamic in soil under fertilizing for obtaining high grain yields of winter wheat (Triticum aestivum L.) and to determine relationships between nutrient uptake and winter wheat productivity. The field study was carried out at the Research and Study farm ‘Vecauce’ of the Latvia University of Agriculture for two years 2012/2013 and 2013/2014 with winter wheat variety ‘Kranich’. Different nitrogen application rates (0, 85, 153, 150, 175, 180 and 187 kg haE-1) and timing were used for winter wheat. The content of nitrates NO3 -N and ammonium nitrogen NH4 -N was determined in the soil layers 0-0.20 m, 0.20-0.40 m, 0.40-0.60 m. Nitrogen management strategy during the plant growth period based on soil Nmin evaluating can improve N use efficiency and reduce environmental contamination. The maximum of mineral nitrogen content in soil in the vegetation period was observed at the beginning of stem elongation with a tendency to decrease. A significant impact (p is less than 0.05) of nitrogen fertilizer application was noted on the mineral nitrogen content in soil layer 0-0.20 m deep in both trial years. The increasing doses of nitrogen fertilizer raised the amount of mineral N in the soil profile. The significant impact (p is less than 0.001) of nitrogen application and year conditions was observed on grain yield. Close positive correlation significant at 99% probability level was observed between the grain protein content and nitrogen concentration mostly in all soil layers, but it was not found between the grain yield and nitrogen content.

Natural processes and human activity play a crucial role in altering the nitrogen cycle and increasing nitrogen oxide (N2O) emissions. Nitrous oxide isotopes 15N and 18O are important parameters that can help to explain the sources of N2O gas, as well as their circulation under different soil physical properties. The main goal of the study is to analyse the possibilities of using dinitrogen isotopes 15N and 18O, measured in soil samples, for the identification of N2O sources. A total of 16 plots were sampled. Each soil sample was assigned a code. Wetting of the samples was carried out to create wet aerobic conditions and wet anaerobic conditions. N2O measurements were performed in laboratory conditions using the Picarro G5131-i device. The 15Nα and 15Nβ values obtained in the measurement data were used to calculate the δ15NSP and δ15Nbulk values. The obtained δ15NSP and δ15Nbul values were analysed using two methods – descriptive statistics and Kruskal-Wallis test. The test showed that there are statistically significant differences between δ15NSP values (p-value <0.0001), and δ15Nbulk there was no significant difference (p-value 0.885).