Abstract
An experiment was conducted to determine the effect of humic acid (HA), substrates, and boron (B) rates on the growth of papaya (Carica papaya L.) seedlings in the nursery stage. Papaya transplants were grown directly from seed on (1) sandy soil (SS), (2) a commercial substrate based on sphagnum peat moss (SM), (3) a 1:1 SS and bovine manure (BM) substrate, (4) a 1:1:1 SS, SM, and BM substrate, (5) 1:1 coconut coir and SS, and (6) 1:1 SM and SS substrate, amended with HA (0 or 5 mL. L[sup-]of substrate), and fertilized with different B rates (0, 0.07, 0.14, 0.21, 0.28, or 0.35 mg.transplant[sup-]). Transplant growth (shoot height, stem diameter, leaf number, leaf area, and shoot dry matter) was measured during the experiment. There were significant differences in papaya transplant growth due to substrates and B rates, but not HA. At 35 days after emergence, the best overall papaya transplant growth was found with the B rate of 0.07 mg per transplant and either the 1:1 SS + BM substrate, the 1:1:1 SS + BM + SM substrate, or the 1:1 CC + BM substrate.
