Effect of NPK fertiliser on upper and basal stem diameters and implication on growth habit of tomato

Prostrate growth caused by weak stems and variations in upper and basal stem diameters (USD and BSD, respectively) is inherent in tomato (Solanum lycopersicum L.) and can be aggravated by increased nitrogen fertiliser. Application of a nitrogen fertiliser rate that minimises variation in stem diameters and increases yield can contribute to improved tomato production. The tomato cvs. Buffalo, Cobra, Kerewa, Roma-Savanna, Roma-VF, Tropimech, and UC-82, were grown at Ilara and Imeko with 0, 30, 50 or 80 kg/ha of 15 N-15P-15 K fertiliser. Application of 15 N-15P-15 K increased stem diameter variation. Tomato cultivated in Ilara produced higher number of fruits and fruit weight/plant than those in Imeko but maintained similar habit (40.5° and 42.3°, respectively) in both locations. ‘Buffalo’ and ‘Roma-VF’ had 42.5° and 22.5^° habits and fruit weights (84.4 and 103 g) above average under low (30 kg/ha) and high (80 kg/ha) rates of 15 N-15P-15 K, respectively; ‘Cobra’ combined erect growth (36.3° and 41.2°) and yield above average (107.4 and 101.5 g) under 30 and 80 kg/ha, respectively across locations. Out of 672 plants sampled, 67.4% had USD > BSD, 18.6% USD < BSD, and 14% had USD = BSD. With increased rates of 15 N-15P-15 K fertiliser up to 80 kg/ha, the percent of plants with USD > BSD increased from 49.4 to 76.2% and increased prostrate angle from 26.4^° to 48.4^°. Higher yield combined with erect growth above average can be achieved with 30 kg/ha in ‘Buffalo’ and ‘Cobra’ across the locations. Application of lower rates of 15 N-15P-15 K fertiliser can help in balancing the trade-off between erect growth and higher fruit yield of tomato.