MANAGEMENT-PRACTICES TO IMPROVE LOWLAND SUBTROPICAL SUMMER TOMATO PRODUCTION - YIELDS, ECONOMIC RETURNS AND RISK

Four experiments were conducted in southern Taiwan to evaluate the yie ld and economic benefits of management practices aimed at alleviating the effects of high temperature and heavy rain on tomato production. F ollowing tropical storms, waterlogging caused willing which was more e vident in tomatoes grown in beds 20 cm in height than in those grown i n raised beds 40 cm in height. This indication of crop water stress in duced by flooding was quantified by measurement of the difference betw een canopy surface and air temperature at a specified saturation vapou r pressure deficit. Canopy heating was less on the raised beds, especi ally when straddled by rain shelters. Nevertheless, waterlogging stres s for the low-bed treatment did not result in loss of stand. In crops which experienced heavy rain, application of a synthetic fruit-set hor mone enhanced fruit numbers as did the simple transparent polyethylene rain shelters. While planting on raised beds was without yield benefi t the use of fruit set hormone improved yield by at least 10 t ha(-1). A further 4-6 t ha(-1) yield was gained through the additional use of rain shelters. Partial budget analysis showed positive returns to the use of fruit-set hormone (US$6600 ha(-1)) but, unless rain shelters c ould be constructed with cheaper frame material or used for two tomato crops throughout the summer, their use would be uneconomical. Using e xisting frame material, net returns to rainshelters reached US$8000 ha (-1). The likelihood of high temperatures, tropical storms and typhoon s will influence economic returns to summer tomato production. Data fr om this study may be subjected to economic analyses using values for i nputs and tomato prices from other countries with similar climatic con ditions.