Gross nutrient balance on agricultural land

PREFIX sdmx-measure: <http://purl.org/linked-data/sdmx/2009/measure#> 
PREFIX sdmx-dimension: <http://purl.org/linked-data/sdmx/2009/dimension#> 
PREFIX sdmx-attribute: <http://purl.org/linked-data/sdmx/2009/attribute#> 
PREFIX property: <http://rdfdata.eionet.europa.eu/eurostat/property#> 
PREFIX geo: <http://dd.eionet.europa.eu/vocabulary/eurostat/geo/>
PREFIX nutrient: <http://dd.eionet.europa.eu/vocabulary/eurostat/nutrient/>
PREFIX indic_ag: <http://dd.eionet.europa.eu/vocabulary/eurostat/indic_ag/>

SELECT DISTINCT
year(?date) as ?date
bif:either(?geo = geo:DE, 'Germany', bif:either(?geo = geo:EU, 'European Union', ?ugeo)) as ?ugeo
?nutrient_label
sum(xsd:double(?obsValue)) as ?obsValue

WHERE {
{
  GRAPH <http://rdfdata.eionet.europa.eu/eurostat/data/aei_pr_gnb.rdf.gz> 
    {{
      _:aei_pr_gnb sdmx-dimension:timePeriod ?date . 
      _:aei_pr_gnb property:nutrient ?nutrient .
      #FILTER (?nutrient = nutrient:N)
      _:aei_pr_gnb sdmx-dimension:refArea ?geo . 
      #FILTER (?geo = geo:EU)
      _:aei_pr_gnb property:indic_ag indic_ag:BAL_UAA .
      _:aei_pr_gnb sdmx-measure:obsValue ?obsValue .

    } UNION {
      SELECT xsd:date("2000-01-01") as ?date
             nutrient:N as ?nutrient
             geo:EU as ?geo
             xsd:double(62.7) as ?obsValue WHERE {}
    } UNION {
      SELECT xsd:date("2001-01-01") as ?date
             nutrient:N as ?nutrient
             geo:EU as ?geo
             xsd:double(60.5) as ?obsValue WHERE {}
    } UNION {
      SELECT xsd:date("2002-01-01") as ?date
             nutrient:N as ?nutrient
             geo:EU as ?geo
             xsd:double(59.1) as ?obsValue WHERE {}
    } UNION {
      SELECT xsd:date("2003-01-01") as ?date
             nutrient:N as ?nutrient
             geo:EU as ?geo
             xsd:double(65.1) as ?obsValue WHERE {}

    }}
    ?nutrient rdfs:label ?nutrient_label . 
    ?geo rdfs:label ?ugeo .
    FILTER (year(?date) >= 2000)
  }
}
GROUP BY ?date ?nutrient_label ?ugeo ?geo ?nutrient
ORDER BY ?date