Background: Over the years, the use of organic materials in farming has reduced due to the increase in the use of chemical fertilizers which are rich in readily available plant nutrients. Intensive use of inorganic fertilizers may have depressing effect on yield of watermelon. Field experiment was conducted at the Teaching and Research Farm, Kwara State University Malete, Kwara State, Nigeria, to study the effects of different rates of Organomineral fertilizer Grade A, un-amended compost Grade B and NPK mineral fertilizer on the growth and yield ofCitrullus lanatus.
Results: There were significant differences (P<0.05) among the treatments in relation to vine length, number of leaves, average weight of fruits and yield. NPK at 200 kg/ ha had the highest vine length of 294.67 cm followed by organomineral fertilizer Grade A applied at 2.5 t/ha which had the value of 268.0 cm. Un-amended compost Grade B at 1.5, 2.0 and 2.5 t/ha had vine length values of 257.7, 259.0 and 259.7, respectively. All the fertilizer treatments significantly (P<0.05) had higher number of leaves than control. The highest fruit yield of watermelon (36.7 t/ha) was obtained from organomineral fertilizer Grade A at 2.5 t/ha and NPK.
Conclusion: From this study, the use of organomineral fertilizer in the cultivation of watermelon could be used as alternative to mineral fertilizer, although cost effective but difficult to procure and cannot substantially redress the physical fragility of the soil. It is recommended that organomineral fertilizer Grade A at 2.5 t/ha be adopted for watermelon cultivation in the study area.