Anita Osvalde

Vermicompost from municipal sewage sludge affects growth and mineral nutrition of winter rye (Secale cereale) plants

ABSTRACT The aim of the study was to investigate sewage sludge vermicompost application effects on growth and mineral nutrition of winter rye (Secale cereale L.) plants as compared to two initial levels of mineral nutrient availability, pure sand and sand enriched with inorganic nutrients at the optimal level. Addition of sewage sludge vermicompost significantly inhibited rye seed germination at 20 to 50% sand substitution independently on mineral nutrient supplement. Growth inhibition was evident at early stages of plant development. However, at the later stages, sewage sludge vermicompost acted both as mineral fertilizer and plant growth-promoting agent. Significant stimulation of mineral uptake was seen only at high rates of vermicompost substitution (40 and 50%) already causing decrease in shoot dry matter accumulation. Vermicompost substitution resulted in a significant increase of leaf chlorophyll content. Beneficial effect of sewage sludge vermicompost in conditions of optimal mineral supply can result mainly from plant growth-promoting activity.

Influence of De-Icing Salt on K Supply and Street Trees Ecological Status in Riga, Latvia

The study was conducted to evaluate the toxic effect of soil and plant pollution with Na and Cl− on K supply and ecological condition of the street trees (Tilia × vulgaris H.) in Riga during 2005 and 2007. The results revealed that the ecological status of street trees could be characterized as seriously injured due to high concentrations of Na and Cl− in soil (maxNa 1,568.1 mg/kg; maxCl 744.9 mg/kg) and lime leaves (maxNa 1.93%; maxCl 3.00%). The concentrations of Na and Cl− in lime leaves demonstrated a marked tendency to increase during summer, while the concentrations of K in leaves decreased (min. 0.15%). There were close correlations between the concentration of Na and Cl− in lime leaves and the extent of leaf necrosis, although unfavorable K/Na ratio has additive negative impact.

Effect of Humic Substances on Nutrient Status and Yield of Onion (Allium Cepa L.) in Field Conditions

Humic substances (HS) extracted from various organic materials have been shown to stimulate plant growth. However, scarce information is available on the impact of different methods of application of HS on nutrient status of vegetable species, especially in soil and climate conditions of the temperate zone. The goal of the present study was to evaluate the effect of pre-plant (bulblet soaking) and foliar application of commercially-produced peat and vermicompost-derived HS preparations on nutrient status and yield of onion (Allium cepa L.) in field experiments using two farming systems - conventional and organic. Although the effect was variable between nutrients, dependent on timing, application methods and farming systems, pre-plant and foliar HS tested was hardly effective in preventing nutrient (S, Zn, B) deficiencies limiting onion yield. Moreover, HS induced changes that significantly reduced nutrient status of organically grown onion and had detrimental effect on yield. Although one-year results did not suggest a benefit from HS application, further studies are necessary to evaluate the possible effectiveness of peat and vermicompost extracts on onion production in Latvia.

Comparative Chemical Characterisation of Soils at Cypripedium Calceolus Sites in Latvia

Abstract The main aim of the study was to evaluate the soil chemical characteristics of Cypripedium calceolus sites in Latvia for understanding of the species ecology, and its conservation problems and possibilities. Soil for 27 C. calceolus sites in Latvia was analysed during 2007-2015. The concentration of plant available essential nutrients (N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, Mo, B), soil pH, electrical conductivity and concentration of organic matter were determined. Nutrient concentration of C. calceolus leaf samples from six sites were determined. The results demonstrated high heterogeneity in soil chemical composition with high variation for Ca, Mg, and Mn. The results suggest some relationship between soil organic matter content and size of the orchid population. Soil pH and Ca concentration did not affect the size and vitality of C. calceolus populations in Latvia. There was no significant correlation between nutrient concentration in soil and C. calceolus leaves suggesting strong impact of other soil-related factors in determining the availability of nutrients. In general, the levels of N, P, K, Ca, Mg, Fe, Mn, and Zn concentrations in C. calceolus leaves were adequate or slightly decreased for successful orchid growth. The study showed deficiency of S, Cu, and B in the vast majority of leaf samples. C. calceolus sites in Latvia occur mainly on organic soils or mineral soils with high content of organic matter. There was a weak positive correlation (r = 0.21) observed only between total number of ramets of C. calceolus in site and Ca concentration in the soil, suggesting that soil properties are not a main factor affecting species abundance in the site.

Mineral Nutrition of Young Ash in Latvia

Abstract The research objectives were: 1) to determine healthy young ash supply with nutrients and their concentrations in natural growth conditions; 2) to estimate nutrient balance and inter-correlations within a system “soil-plants”; and 3) to determine the potential effect of environmental conditions (forest type, plant phytosociological group, soil group, etc.) on nutrient accumulation in soil and leaves of young ash. The investigation was conducted in 28 different forest sites with young ash in Latvia. The results demonstrated that young ash grows well on a wide range of site types in terms of soil composition, forest type and phytosociological tree group. Although highly heterogeneous, soil in ash stands in Latvia can provide a sufficient supply of nutrients. Therefore, the nutrient status of healthy young ash leaves can be characterized as sufficient, although low levels of P, Zn, and K in leaves was found for most sites. Significant impact of soil group and forest type was found on nutrient composition of ash soil, while leaf nutrient concentrations were more dependent on the forest type and phytosociological tree group. The obtained results confirmed the ability of ash to accumulate nutrients within a certain range from soils of different fertility, organic matter content and soil reaction in Latvia.

Chemical Composition of Scots Pine Bark as a Bioindicator of Environmental Quality in Riga, Latvia / Priežu Mizu ķīmiskais Sastāvs Kā Vides Stāvokļa Bioindikators Rīgā (Latvija)

Abstract The chemical composition of pine bark was used for the determination of environmental quality in Rīga. Bark samples were collected at 54 sites in Rīga differing in vegetation and building area characteristics (urban forests, parks and cemeteries, dwelling houses, and streets and railway zones) and at 52 sites from rural areas in Latvia (background level). Concentrations of Ca, Mg, Na, K, Fe, Mn, Zn, Ni, Cu, Cd, Pb, and pH was determined in the samples. The results showed significantly higher concentrations of chemical elements in pine bark collected in Rīga, compared to background levels: Fe and Cu concentrations three times higher, and other elements - up to 1.8 times. The highest element concentrations in Rīga were near streets (Sarkandaugava, Jaunmīlgrāvis, Daugavgrīva, Čiekurkalns, Imanta area, etc.). Element concentration and pH was significantly dependent on the distance from the closest street. The lowest element concentrations were found in urban forests (Jugla, Biķernieki, Beberbeķi) and parks and cemeteries (I Forest Cemetery, Jaunciema Cemetery). Mežaparks (forest), Sarkandaugava, Jaunmīlgrāvis, and Vecmīlgrāvis together formed the most polluted area in Rīga due to the close location near and downwind from the harbour. Vides stāvokļa novērtēšanai Rīgā kā bioindikators izmantots priedes mizas ķīmiskais sastāvs. Paraugi tika ievākti 54 vietās pilsētā atkarībā no veģetācijas un apbūves īpatnībām: urbānie meži, parki un kapsētas, dzīvojamās mājas un ielu malas un dzelzceļa zonas. Fona līmeņa raksturošanai izvēlētas 52 vietas Latvijā ārpilsētas mežos. Visos paraugos noteikta Ca, Mg, Na, K, Fe, Mn, Zn, Ni, Cu, Cd, Pb koncentrācija un pH. Rezultāti parādīja, ka Rīgā, salīdzinot ar fona līmeni, bija lielāka visu priedes mizā analizēto ķīmisko elementu vidējā koncentrācija. Fe un Cu koncentrācija pilsētvidē bija trīs reizes, bet pārējo ķīmisko elementu koncentrācija - līdz 1,8 reizes lielāka, salīdzinot ar lauku vidi. Pilsētvidē lielākās ķīmisko elementu koncentrācijas konstatētas gar brauktuvēm (Sarkandaugavā, Jaunmīlgrāvī, Daugavgrīvā, Èiekurkalnā, Imantā un citur). Konstatēts, ka ķīmisko elementu koncentrācijas būtiski izmainās, attālinoties no brauktuves. Viszemākās ķīmisko elementu koncentrācijas priedes mizā bija pilsētmežos (Jugla, Biķernieki, Beberbeķi), kā arī parkos un kapsētās (I Meža kapi, Jaunciema kapi). Tomēr Mežaparks (mežs) līdz ar Sarkandaugavu, Jaunmīlgrāvi un Vecmīlgrāvi bija stiprāk piesārņotais Rīgas rajons, jo tas atrodas ostas kompleksa un valdošo rietumu vēju tiešā ietekmes zonā.