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In 2013-2014, research was carried out on a Bathihypogleyi-Haplic Luvisol (LVh-gld-w) soil with predominant sandy loam and pH KCl 4.9-5.2 with a view to finding out how composts produced from sewage sludge, green waste and biogas production waste influenced grain and straw yields of winter wheat grown in the first year after compost incorporation and spring barley grown in the second year after incorporation as well as the concentrations of nitrogen, potassium and heavy metals in grain and straw. The field experiment was conducted in the fields of Elmininkai Experimental Station (Anykščiai distr., Eastern Lithuania) of the Lithuanian Research Centre for Agriculture and Forestry. The investigations proved that the composts incorporated without mineral fertilizer did not increase grain and straw of winter wheat grown in the first year after incorporation. During the second year, the composts increased the spring barley grain yield as follows: biogas -by 72.9%, green waste -68.6%, cattle manure -58.9% and sewage sludge -45.2%. The application of composts on the background of mineral fertilizers did not significantly increase winter wheat and spring barley grain and straw yields compared with mineral fertilizers. The concentration of chemical elements in plants depended on the compost degradation process in soil. During the first year after incorporation of composts, nitrogen (N) concentration in winter wheat grain was increased by biogas, and during the second year -by sewage sludge and green waste composts in spring barley grain. Potassium (K) concentration in winter wheat and spring barley straw was increased by cattle manure, biogas and sewage sludge composts. During the first year, all composts increased phosphorus (P) concentration in winter wheat straw. The concentrations of heavy metals (Cd, Ni, Pb, Zn, Mn and Cu) in grain and straw were close to the background levels. The composts used in the study increased the content of nickel in winter wheat and spring barley grain and straw somewhat more significantly.

Please use the following format when citing the article: Arbačauskas J., Masevičienė A., Žičkienė L., Staugaitis G. 2018. Mineral nitrogen in soils of Lithuania's agricultural land: comparison of oven-dried and field-moist samples. Zemdirbyste-Agriculture, 105 (2): 99- AbstractMineral nitrogen (N min = N-NH 4 + + N-NO 3 − ) in oven-dried and field-moist samples was investigated in 2011-2014 in five areas of Lithuania with soils of different texture (sand, sandy loam, loam and clay) and different mineral nitrogen (N min ) content. The samples were taken in spring (from late March to early April) and autumn (late October -early November), from the 0-30, 30-60 and 60-90 cm as well as from 0-60 cm soil layers. The aim of the research was to determine the influence of different methods of soil sample preparation on the concentrations of ammonium (N-NH 4 + ) and nitrate (N-NO 3 − ) nitrogen in oven-dried and field-moist samples and to assess the suitability of the obtained results for the development of agricultural plant fertilisation plans. According to the research results, drying of soil samples at a temperature of 35°C for 12 hours resulted in significantly higher levels of N-NH 4 + compared to those of field-moist samples. The N-NO 3 − concentrations in the field-moist samples, when stored at a 4°C temperature for 3 days, increased marginally compared to the oven-dried soil samples. Weak or moderate, however, statistically significant correlations were observed between N-NH 4 + concentrations in the oven-dried and field-moist samples. In order to perform faster chemical analyses of soil N min for making agricultural plant fertilisation plans, it is necessary to carry out analyses on oven-dried soil samples, and using the linear correlation equations, to convert the results of N-NH 4 + analyses into field-moisture data.Keywords: ammonium and nitrate nitrogen, preparation of samples for analysis.

Soil microorganisms are one of the main indicators used for assessing the stability of the soil ecosystem, the metabolism in the soil, and its fertility. The most important are the active soil microorganisms and the influence of the fertilizer applied to the soil on the abundance of these microorganisms. We aimed to investigate how the applied organic fertilizers affect the most active soil microorganisms, which determine the soil fertility and stability. Fungi, yeast-like fungi abundance, and abundance of three physiological groups of bacteria were analyzed: non-symbiotic diazotrophic, organotrophic, and mineral nitrogen assimilating. This study is valuable because relatively few similar studies have been performed on infertile Lithuanian soils. The first results of a long-term study were obtained. The results show the effect of fertilizers on trends in the changes of microorganism community diversity; however, more analysis is needed to assess the impact of organic fertilizers on the most active soil microorganisms. Therefore, the investigation was continued. The results of the 2020 quantitative analysis of culturable soil microorganisms show that the highest abundance of organotrophic and non-symbiotic diazotrophic bacteria were recorded during the summer season. Meanwhile, the abundance of bacteria assimilating mineral nitrogen and fungi was higher in autumn. Agrochemical parameters were determined at the beginning of the experiment. The highest concentration of Nmin in the soil was determined after fertilizing the plants with the combination of granulated poultry manure (N170) + biological substance Azotobacter spp. The yield of barley was calculated. It was found that the highest yield of spring barley in 2020 was obtained by fertilizing the experimental field with organic in combination with mineral fertilizers.

The monitoring of mineral nitrogen (N min ) concentration in Lithuanian soils was conducted during the period 2005-2014 in 206 test sites of 20 × 20 m size located in 15 different soil regions considering the appropriate geographical units. The soil regions are distinguished from one another by relief, soil type, soil texture, climatic conditions as well as the specialisation and intensity of agricultural activities. It was found that soil N min concentration in spring differed not only between years, but also between the geographic climatic zones of Lithuania. The most important factors and their interactions affecting the soil N min concentration in spring were crops and pre-crops, soil texture, winter air temperatures and precipitation levels. The lowest N min concentration in 0-60 cm soil layer in spring was recorded in perennial grass fields and pastures, in fields where pre-crops were spring cereals and spring rape, in sandy loam and particularly sand soils, when precipitation levels during the November-March period were high and especially when this level exceeded 250 mm, when predominant winter air temperature was above 0°C. The soil N min concentration tests taking into account the territorial division of Lithuania into 15 soil regions enabled us to assess the long-term fluctuation of this indicator as affected by the local conditions. The accumulated and processed multiannual data can be used as a reference for the assessment of the results of the future tests.