Maitree Kaewtubtim* Montree Issarakrisila and Somsak Maneepong
Effect of nitrogen on fruit quality of pummelo cv. Tubtim Sayam was carried out between January 2013 to February 2014 at a pummelo orchard in Sub-district Klong-Noy, Pak Panang District, Nakhon Si Thammarat Province. The objectives of the study were to examine the nitrogen rate that affect on fruit quality. The study in relation to application of nitrogen, there were three treatments: no application of nitrogen-fertilizer (T1), application of nitrogen at farmers’rate (T2), and application of farmers’rate with additional 40 kg of calcium nitrate per rai (T3).Tubtim Sayam pummelo fruits were harvested 28 weeks after the flowers bloomed, it was found that those from the three treatments did not show significant difference in their weight, width, height, peel thickness, fresh pulp weight, fresh peel weight, dry pulp weight, dry peel weight, total soluble solid (TSS), total acid (TA), andvitamin C. The trees receiving nitrogen at farmers’rateproduced fruits which had high levels of sucrose, glucose, fructose, and total sugar as 124.06, 50.61, 16.59, and 191.26 g/l. respectively, significantly different from the trees receiving no fertilizer. As for the trees receiving nitrogen and additional calciumnitrate, their fruits had the lowest level of limonin (1.99 mg/l) and highest levels of lycopene and anthocyanin (2.38 and 7.01 mg/100 ml). The fruits of the trees receiving no fertilizer had the highest level of b-Cerotene (0.54 mg/100 ml).