Thesis Abstract of AGS Students

Effects of staking, plant density and potasium fertilizer on yield and quality of tomato

Zhong Li (1991)

Tomato (Lycopersicon esculentum M.) is one of the economic crops in Chiang Mai Valley. It is mainly grown during the cool season after rice. A formal Survey conducted during June to July 1990 showed that the yields in San Sai and Chom Thong districts were 33.0 t/ha and 19.3t/ha, respectively. These are relatively low compared with the 64.6 t/ha recorded in Chiang Mai University experimental station. It also has been observed that tomato fruits often show nonuniform red color at maturity. Staking culture, plant density, and K fertilizer are hypothesized to affect the yield and quality of tomato.

A field experiment was conducted from November 1990 to April 1991 on a sandy loam soil (San Sai series) at the Irrigated Agricultural Research Station, Faculty of Agriculture, Chiang Mai University. The purpose of the study was to examine the effects of management practices with emphasis on staking, plant density, and potassium fertilizer on the yield and quality of tomato.

Cultivar VF 134-1-2 was tested in a factorial experiment arranged as a split-split-plot design with three replications. Staking and nonstaking treatments were in the main plots; plant density with three spacing levels (75 x 15 cm, 75 x 30 cm, and 75 x 45 cm) was arranged as the subplots; and K fertilizer at four levels (0, 100, 200, 300 kg K2O/ha) was treated in the sub-subplots. The same rate of 150 kg/ha of N and 100 kg/ha of P2O5 were applied to all experimental plots.

The results of the experiment revealed significant interactions between plant spacing and staking. No significant differences in marketable yields among plant spacing and staking treatments were detected except at 15 cm spacing within rows which resulted in the population density of 88,889 plants per hectare. At this density if staking was not used, the marketable yield was significantly lower than that from the staking treatment and it was also lower than other combinations of wider spacing and staking treatments. The results of economic analysis shows that the net gain of staking treatments at 15 cm spacing is -12 baht/ha comparing to the nonstaking treatment due to the high increment labor cost for staking. The net gain of this treatment would be 16,628 baht/ha if labor cost is not taken into consideration. Staking also reduced the unmarketable yield significantly.

Higher rate of K had beneficial effect on the quality of tomato fruits in terms of the total acidity and the color. K fertilizer also had interaction effects with staking regarding the total solids and had an interaction effect with plant spacing in terms of the soluble solids. Staking and plant density did not have significant effects on total acidity, soluble solids or total solids of tomato fruits.

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