Tomato Performance Under Humic and Fortified N-Sources

ABSTRACT
This study evaluated the impact of humic acid (HA) fortified nitrogen sources on the growth and yield of tomatoes grown under different conditions. Soil properties, including pH, total organic carbon (TOC), total nitrogen (TN), available phosphorus (Av. P), exchangeable cations, effective cation exchange capacity (ECEC), base saturation (BS), extractable micronutrients, and particle size distribution, were analysed pre-planting. The soil exhibited a loamy sand texture with moderate organic matter and nutrient levels, and an acidic pH of 5.17, which could affect nutrient availability. Tomato growth and yield were assessed in both open field and screen house environments using four treatments: control (no HA fortification), HA with Tithonia, HA with urea, and HA with NPK, each at a rate of 52 kg N ha⁻¹. In the open field, the HA-fortified treatments showed improved plant height, number of leaves, branches, and fruit yield compared to the control. The screen house conditions further enhanced these parameters, with the HA NPK treatment producing the tallest plants (96.13 cm) and the highest leaf count (248.33), while the HA Tithonia treatment yielded the most fruits (13.65 tons ha⁻¹). Nitrogen use efficiency (NUE) was also evaluated, showing significant improvements with HA-fortified treatments. In the open field, HA urea achieved the highest NUE (80.84), while in the screen house, HA urea also led with 76.75, although NUE values were generally lower in the controlled environment. Overall, the results demonstrated that HA-fortified nitrogen sources, particularly with Tithonia and NPK, significantly enhance tomato growth and yield, with the controlled environment of the screen house providing the most favourable conditions. These findings suggest that HA fortification can be a viable strategy to improve tomato cultivation, optimising nutrient use and supporting better plant performance.