Koreh AA, Widowati, Julianto RPD. Long-term residual effects of biochar from tobacco scraps on red spinach (Amaranthus tricolor) growth in Entisols: a five-year field experiment with urea fertilizer addition. J. Ilm. Pertan. 2023;20(2):153-164. doi:10.31849/jip.v20i2.13451