Growth and yield of summer squash: effect of the ionic concentration of nutrient solution

Abstract

With the objective of evaluating the effect of different ionic concentrations of the nutrient solution on growth of summer squash cultivated in raw rice husk substrate with leaching recirculation, two experiments were conducted in two crop-seasons: spring-summer of 2005 and summer-autumn of 2006, in Pelotas, RS. Four ionic concentrations of the nutrient solution (based on electrical conductivity - EC) were studied: 1.3; 1.7; 2.1 and 4.2 dS m^-1. Crop growth was determinated by accumulated dry mass production and partitioning among the different above-ground plant organs (leafs, stem and fruits) at the end of the crop-seasons. Fruit yield was also evaluated. The obtained results indicate that ionic concentrations equal or lower than 1.7 dS m^-1 were limiting for proper growth and yield of the crop. The effect of high ionic concentration of the nutrient solution (above 2.1 dS m^-1) on dry mass production and partitioning varied according to the crop-season. The lower solar radiation availability of the summer-autumn crop season minimized the effects of the different concentrations of nutrient solution on dry mass production and partitioning to the fruits, as well as on the yield. The fruits comprised from 28 to 52% of the total above-ground dry mass production. Fruits represented the largest sink of assimilates of the plant only at 2.1 dS m^-1 ionic concentration of the nutrient solution and in crescent solar radiation availability condition (spring-summer). According the mathematics models, the electrical conductivity that maximizes dry mass production and yield is approximately 3.0 dS m^-1 for both crop-seasons.