EFFECTS OF FERTIGATION MANAGEMENT ON GROWTH AND PHOTOSYNTHESIS OF TOMATO PLANTS GROWN IN PEAT, ROCKWOOL AND NFT

A greenhouse experiment was conducted to determine the effects of subs trate, irrigation scheduling and nutrient solution electrical conducti vity (EC) on plant growth and photosynthesis of tomato plants. The pla nts grown in peat-bags were irrigated by a potential evapotranspiratio n (PET) dependent irrigation system. The first peat-bag treatment (con trol) was irrigated when the soil water potential reached -5 kPa. EC w as fixed at 2.5 dS m(-1). EC of other two peat-bag treatments was vari ed between 1 and 4 dS m(-1) with a soil water potential setpoint (SWPS ) of either -5 or -9 kPa. Plants grown in rockwool and by the nutrient film technique (NFT) were treated with EC levels of 2.5, 4.0 and 5.5 dS m(-1). EC variation resulted in higher photosynthetic capacity (P-c ), quantum use efficiency (QUE) and dry matter production (DMP) under high SWPS compared with the control. The increase in DMP resulted main ly from fruit yield increase. In the treatment of EC variation with lo w SWPS, P-c and DMP were lower than in treatment of EC variation with high SWPS, but not different from that in the treatment of fixed EC. T he high EC treatment of 4.0 dS m(-1) decreased DMP in NFT, but did not in rockwool. EC of 5.5 dS m(-1) decreased fruit yield but did not aff ect shoot DMP. However, high EC treatments, especially EC of 4 dS m(-1 ), increased P-c as well as QUE in rockwool and in NFT. DMP and P-c wa s not positively correlated with each other for EC treatment, However, it is concluded that PET-dependent EC variation increases photosynthe tic capacity, plant growth and fruit yield of greenhouse tomato plants .