PENGARUH PEMBERIAN ABU VULKANIK DAN PUPUK KANDANG TERHADAP pH, KTK DAN BASA-BASA TERTUKAR TANAH ULTISOL = EFFECT OF VOLCANIC ASH AND COW MANURE APPLICATION ON pH, CEC AND EXCHANGABLE ALKALINE OF ULTISOL - TAMPUBOLON, WIDYA NANDA SARI (2018)