Kartini, Kartini, et al. “Improving the Productivity of Hybrid Maize through Soil Ameliorant and NPK Fertilizer Applications on Ultisols: Peningkatan Produktivitas Jagung Hibrida Melalui Pengaplikasian Amelioran Dan Pupuk NPK Pada Tanah Ultisol”. Agrifarm: Jurnal Ilmu Pertanian, vol. 14, no. 2, Dec. 2025, pp. 70-77, doi:10.24903/ajip.v14i2.3726.