Effect of phosphorus and potassium fertility on fruit quality and growth of Tabasco pepper (Capsicum frutescens) in hydroponic culture

Abstract

Effects of P and K fertilization on Tabasco plant growth and fruit quality were evaluated in a preliminary experiment conducted in fall 2002; 4 levels of P (0.25, 1.0, 1.75, and 2.5 mM) and 4 levels of K (0.75, 1.75, 2.75, and 3.75 mM) in hydroponic culture with a factorial randomized design. The main growth experiment was conducted in spring/summer growing period of 2003. This experiment consisted of 8 treatments; 4 levels of P (P1 0.25, P2 1.25, P3 2.5, and P4 3.75 mM) and 4 levels of K (K1 0.25, K2 1.25, K3 2.5, and K4 3.75 mM). The same treatments were used to evaluate fruit quality characteristics in an experiment conducted simultaneously. Tabasco pepper "McIlhenny Select" seed were sown in trays; at the fourth true leaf stage, individual plants were transplanted into 3-gallon round plastic pots filled with agricultural grade perlite. Plants were harvested once every month; stem diameter and plant measurements were taken every fifteen days. The Preliminary growth experiment showed that P affected plant height, leaf area, root, stem and leaf dry weights as well as overall plant dry weight. Potassium affected root dry weight at both harvests with no influence on other growth variables. Dry root weights of plants grown with the highest K rate (K4) were significantly higher than the lowest k rate (K1). Potassium source was changed for the main plant growth experiment. Phosphorus and potassium rates significantly affected plant growth, increasing height, weight, stem diameter, leaf area, and dry weights of plant sections with increasing rates in nutrient solution. For fruit quality experiment, all plants grew until the flowering stage with the same nutrient solution (2 mM P; and 3.75 mM K). At the beginning of the flowering stage different nutrient treatments were applied. Increasing P and K rates also affected plant yield and some fruit quality variables. Results were consistent for most of the variables, suggesting that the 0.25 mM concentration for both P and K was insufficient for pepper production. Concentrations higher than 1.25 mM and close to 2.5 mM are the most appropriate for hydroponic tabasco pepper production.