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Sirvi Autor "Petaja, G." järgi

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  • Pisipilt
    Kirje
    Carbon and nitrogen accumulation by agricultural crop residue under three cropping systems
    (Estonian University of Life Sciences, 2025) Rancāne, S.; Lazdiņš, A.; Petaja, G.; Purviņa, D.; Zute, S.; Jansone, I.; Damškalne, M.; Putniece, G.
    Agricultural crops produce different biomass during their growth, including varying amounts of residue which accumulate a significant amount of carbon (C) and nitrogen (N). Assimilation capacity depends largely on species, variety and growing condition. Carbon accumulation in soil contributes to both - the agricultural production and maintenance of environmental quality reducing atmospheric C and greenhouse gas emissions. In this study, the amount of plant residue left on the field by above-ground and below-ground residue and the amount of C and N accumulated in them in three different cropping systems: organic (Bio); integrated with a low input of N fertiliser (Int-low-N) and; integrated with a high input of N fertiliser (Int-high-N) were evaluated. The most commonly grown cereal crops in Latvia were tested: winter wheat (WW); summer wheat (SW); winter rye (WR); winter triticale (WT); summer barley (SB); summer oat (SO); and buckwheat (BW) as pseudo-cereal crop. The highest biomass of dry matter of total harvest residue in all cropping systems was recorded in WR: 853.3 ± 40.76 g m-2; 1,482.0 ± 105.06 g m-2; 1,628.3 ± 115.49 g m-2 - in Bio; Int-low-N; Int-high-N cropping systems, respectively. The highest amount of carbon (g C m-2) using organic cropping system was accumulated by residue of: WR (268.6 ± 28.68), BW (239.4 ± 10.50) and WW (234.5 ± 27.41). The highest amount of carbon (g C m-2) using integrated cropping system was accumulated by residue of: WR - 473.8 ± 64.9; 496.6 ± 62.54 and WT - 458.2 ± 32.57; 521.1 ± 46.26 in Int-low-N and Int-high-N, respectively. Higher proportion of root biomass cereals formed using organic cropping system.
  • Pisipilt
    Kirje
    Evaluation of greenhouse gas emissions and area of organic soils in cropland and grassland in Latvia – integrated National forest inventory data and soil maps approach
    (2018) Petaja, G.; Okmanis, M.; Polmanis, K.; Stola, J.; Spalva, G.; Jansons, J.
    The aim of the research was to assess distribution of organic soils in farmlands for the time period between 1990 and 2015, as well as to carry out a recalculation of GHG emissions from organic soils in grassland and cropland. We evaluated the area of typical organic soils using digitized soil maps created between 1960s and 1980s there were 183,000 ha of cropland and grassland on organic soils. A selected number of areas on organic soils intersecting with the National forest inventory (NFI) plots were surveyed. We found that 66 ± 10% of surveyed plots still conforms to criteria for organic soils according to Intergovernmental Panel on Climate Change (IPCC) guidelines; in the rest of plots soil organic matter has been mineralized and these areas do not conform to IPCC criteria of organic soils. The following distributionof organic soils was estimated in cropland – 6.3 ± 3.3% in 1990 and 4.1 ± 3.4% in 2015, but in grassland – 11.6 ± 3.6% in 1990 and 7.7 ± 3.9% in 2015. The annual reduction of GHG emissions due to reduction of area of organic soils in cropland in 2015 corresponds to 1,400,000 tonnes CO2 eq. in comparison to 1990 and in grassland – to 1,100,000 tonnes CO2 eq. The estimated reduction of the GHG emissions due to conversion of organic soils into mineral soils, comparing the average value in 2005–2009 with the projection for 2021–2030 on average will correspond to 313,000 tonnes CO2 eq. annually, however LULUCF sector still won’t become a net CO2 sink according to the GHG inventory data on other land use categories and carbon pools.