Effects of fertigation management on growth and photosynthesis of tomato plants grown in peat, rockwool and NFT

Abstract

A greenhouse experiment was conducted to determine the effects of substrate, irrigation scheduling and nutrient solution electrical conductivity (EC) on plant growth and photosynthesis of tomato plants. The plants grown in peat-bags were irrigated by a potential evapotranspiration (PET) dependent irrigation system. The first peat-bag treatment (control) was irrigated when the soil water potential reached −5 kPa. EC was fixed at 2.5 dS m −1. EC of other two peat-bag treatments was varied 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 mainly from fruit yield increase. In the treatment of EC variation with low 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. The 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 affect 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 was not positively correlated with each other for EC treatment. However, it is concluded that PET-dependent EC variation increases photosynthetic capacity, plant growth and fruit yield of greenhouse tomato plants.