Ligita Baležentienė

Sezoninė C apykaita žolių ir kviečių agroekosistemose

Nors svarbu pasirinkti aplinkos tvarumą palaikančius pasėlius, siekiant įvertinti jų poveikį klimato kaitai, tačiau tikslių ir apibendrintų anglies apykaitos duomenų Lietuvos pasėlių agroekosistemose nėra sukaupta. Todėl, norint įvertinti C apykaitą intensyviosios žemdirbystės daugiamečių žolių ir žieminių kviečių (Triticum aestivum L.) agroekosistemose skirtingais sezonais, išmatuojant augalų ir dirvožemio kvėpavimo CO2 emisiją (Ra+s) ir fotosintezės asimiliuotą CO2 kiekį bei nustatant aplinkos veiksnių ir įtaką žemdirbystės tipo poveikį, 2013–2014 m. ASU Mokomajame ūkyje buvo atlikti tyrimai. Žolių ilgesnis pasiruošimas žiemoti lėmė intensyvesnį dirvožemio kvėpavimą (0,334 μmol m–2 s–1) negu kviečių (0,268 μmol m–2 s–1) rudenį, o peržiemojus – intensyvesnį kviečių (1,509 μmol m–2 s–1) nei žolių (1,413 μmol m–2 s–1). Dirvožemio CO2 emisijos priklausė ir nuo aplinkos sąlygų, ypač oro temperatūros. Vidutinė bendroji pirminė produkcija buvo 12,79 μmol m–2 s–1 žolių ir 13,28 μmol m–2 s–1 kviečių. Grynoji CO2 apykaita rudens sezoną didesnė buvo žolių – 4,15 μmol m –2 s–1, kviečių – 3,9 μmol m–2 s–1. Tačiau visos augalų vegetacijos NEE nežymiai didesnė buvo kviečių – 10,83 μmol m–2 s–1, žolių – 10,30 μmol m–2 s–1. Reikšminiai žodžiai: respiracija (R), bendroji pirminė produkcija (GPP), grynoji agroekosistemos apykaita (NEE), aplinkos sąlygos.

ALLELOPATHIC ACTIVITY OF INVASIVE SPECIES SOLIDAGO CANADENSIS L.

Solidago canadensis L. ( Asteraceae ) spread throughout the world and also is enlisted in the National list of invasive species (2012). Here the allelopathic activity of the species was assessed in terms of further understanding of their distributions over the range of native spread. The invasion success of S. Canadensis was tried to base on the estimation of the total phenolics content (TPC) in the plant aqueous leachates at different growth stages. Allelopathic impacts (total phenolics content, total concentration and dynamic, conventional coumarine units, CCU) of S. canadensis were examined during 2012-2013 in Laboratory of raw materials, agro and zootechnics research, Aleksandras Stulginskis University. The plants were sampled in spring (May, rosette), summer (June, flowering) and autumn (September, seed maturity) for preparing the aqueous extracts. The biochemical (allelopathic) characteristics of S. canadensis aqueous extracts were examined at different plant growth stages. Principal (0–9) and secondary (0–9) growth stages as per universal BBCH scale description and coded using uniform two-digit code of phenologically similar growth stages of all mono- and dicotyledonous plant species. The TPC ranged between 0.968 mg ml -1 to 23.591 mg ml -1 depending on the plant ontogenetic stage, plant part and extract concentration (r = -0.7). Due to accumulated allelochemicals, the invasive S. canadensis , might acquire distribution advantage in new territories outside the native habitat range, through the inhibitory effects on germination of native plant species. Keywords : Solidago canadensis, allelopathy, phenolics. Article DOI: http://doi.org/10.15544/RD.2015.037

Indicating Soil Quality Using Urease and Saccharase Activity in Abandoned Grassland and Differently Managed Crop Fields

In order to ascertain and make a comparison of bioactivity variation during vegetation period, soil samples were collected in fields of different fertilizing and farming systems: extensive (ExF), conventional (CF) and organic (OF) in order to determine the saccharase and urease activity responses to different land management systems and main soil quality indices: soil organic carbon (SOC), total nitrogen (N), and C/N ratio. Assessed hydrolases were observed as sensitivity indicators suitable to evaluate parameters of soil quality. The highest decrease and the lowest rates of urease (1.13 mg NH4 +–N g−1) and saccharase (8.40 mg CG g−1 24 h−1) activities were observed in abandoned grassland soil where mineral fertilizers were not applied. Enzyme activity correlated stronger with SOC (r = 0.7) or C/N ratio (r = 0.6) than that with total nitrogen content (r = 0.5 − 0.6). A significantly higher 3 year mean value of saccharase (27.00 and 12.6 mg CG g−1) and urease (5.78 and 4.16 mg NH4 +–Ng−1 24 h−1) activities were observed in soil under conventional and organic management compared with abandoned grassland. Thereafter enzyme activities might be related to the different levels of soil fertility.