Abstract:
Tomato is produced in eastern Ethiopia for fresh fruit and cash-generating for growers. However, the productivity of the crop is low due to many constraints of which the types and rates of fertilizers used irrespective of varietal and soil type’s differences are among the major constrains. The experiment was therefore, conducted to assess the effect of NPS fertilizer rates on yield, yield related and fruit quality traits of tomato varieties, and to estimate cost-benefit of NPS fertilizer rates for tomato production at Dire Dawa. The treatments consisted of seven rates of blended NPS (0, 50, 100, 150, 200, 250 and 300 kg ha-1) and three tomato varieties (Shanty PM F1, Shanty N F1 and Galilea) in factorial combination. The experiment was laid out in randomized complete block design with three replications. Results from analysis of variance showed that NPS fertilizer had significant effect on days to 50% fruiting, number of harvest and duration of harvest, plant height, stem diameter, number of primary and secondary branches, leaf area index, number of clusters per plant, number of flowers per cluster, number of fruits per cluster and fruit set percentage. Average fruit weight, mean fruit length, mean fruit width, number of marketable and unmarketable fruit/ per plant, marketable, unmarketable and total fruits yield were also significantly influenced by NPS fertilizer. Variety and blended NPS fertilizer had significant effect on days to 50% flowering,days to maturity, fruit shape index, mean pericarp thickness, fruit juice content. Total soluble solids was significantly influenced by NPS fertilizer and interaction of variety x NPS fertilizer whereas the two main factors and interaction of variety x NPS fertilizer had significant effect on titratable acidity and sugar to acid ratio. The application of 300 and 250 kg ha-1 NPS fertilizer delayed days to flowering, fruiting and maturity and increased all growth, fruit set characteristics, fruit physical quality parameters and fruit juice content of varieties. The highest marketable and total fruit yields of 73.98 and 87.03 t ha-1, respectively, obtained by application of 250 kg ha-1 NPS fertilizer, however, it nonsignificant difference with marketable and total fruit yields of 73.27 and 86.5 t ha-1, respectively, obtained by application of 300 kg ha-1 NPS fertilizer. Galelia variety with the application of 250 kg ha-1 NPS fertilizer had highest sugar to acid ratio. The partial factor productivity of fertilizer was significantly influenced only by rates of NPS suggested the tomato varieties had similar production efficiency for the applied fertilizer rates. The application of 250 kg ha-1 NPS fertilizer gave the highest net benefit, benefit-cost ratio and marginal rate of return of 894945.2 Birr ha-1, 8.62 and 8404.24%, respectively. However, the producers also had an option to maximize the net benefit, benefit-cost ratio and marginal rate of return to 955155.2 Birr ha-1, 9.2 and 9347.14%, respectively, by growing Galelia variety supplied with 250 kg ha-1NPS fertilizer. Thus the application of 250 kg ha-1 NPS fertilizer was suggested for the fruit production of tomato varieties at Dire Dawa