You can add the taxon ID to tab-delimited BLAST+ output using the -outfmt option, like this:

-outfmt "6 qseqid sseqid pident length mismatch gapopen qstart qend sstart send evalue bitscore staxids"

You could then use EUtils/efetch to fetch taxonomic data for each taxon ID in XML format and parse it for the kingdom. I recently did this in Ruby, it looks something like this:

require 'bio'
require 'nokogiri' # XML parsing

Bio::NCBI.default_email = "me@me.com"
xml = Bio::NCBI::REST::EFetch.taxonomy(9606, "xml") # taxon ID 9606 = H. sapiens
doc     = Nokogiri::XML(xml)
names   = doc.xpath("//Taxon/ScientificName").children.map { |child| child.inner_text }
kingdom = names[2]
puts kingdom
# => "Eukaryota"

but you could use whatever implementation of EUtils you like e.g. EDirect.

1. Get the taxdb and uncompress it where .ncbirc BLASTDB points
2. Use -outfmt '6 std sskingdoms'
3. Sort for best hits
4. Time to grep
5. You now assigned kingdom level taxonomy based on best-hit criteria
6. One alternative way would be to feed you blast output to blast2lca

I wrote a recursive XSLT stylesheet reading a BLAST XML format and appending the NCBI taxonomy:

https://github.com/lindenb/xslt-sandbox/blob/master/stylesheets/bio/ncbi/blasttaxonomy.xsl

xsltproc --novalid blasttaxonomy.xsl blastp.xml

Something like:

  <Hit_num>1</Hit_num>
  <Hit_id>gi|302699245|ref|NP_001181875.1|</Hit_id>
  <Hit_def>eukaryotic translation initiation factor 4 gamma 1 isoform 6 [Homo sapiens] >gi|302699247|ref|NP_001181876.1| eukaryotic translation initiation factor 4 gamma 1 isoform 6 [Homo sapiens]</Hit_def>
  <Hit_accession>NP_001181875</Hit_accession>
  <Hit_len>1606</Hit_len>

is replaced by:

          <Hit_num>1</Hit_num>
          <Hit_id>gi|302699245|ref|NP_001181875.1|</Hit_id>
          <Taxon>
            <TaxId>9606</TaxId>
            <ScientificName>Homo sapiens</ScientificName>
            <OtherNames>
              <GenbankCommonName>human</GenbankCommonName>
              <CommonName>man</CommonName>
              <Name>
                <ClassCDE>authority</ClassCDE>
                <DispName>Homo sapiens Linnaeus, 1758</DispName>
              </Name>
            </OtherNames>
            <ParentTaxId>9605</ParentTaxId>
            <Rank>species</Rank>
            <Division>Primates</Division>
            <GeneticCode>
              <GCId>1</GCId>
              <GCName>Standard</GCName>
            </GeneticCode>
            <MitoGeneticCode>
              <MGCId>2</MGCId>
              <MGCName>Vertebrate Mitochondrial</MGCName>

(...)