High fertigation frequency and phosphorus level: Effects on summer-grown bell pepper growth and blossom-end rot incidence

The objective was to examine the effects of fertigation frequency and P application rate on bell pepper growth and blossom-end rot (BER) incidence, under hot conditions. The experiment comprised six treatments: two concentrations of phosphorus (3 and 30 mg L-1) combined with three fertigation frequencies (two and eight events per day, and for 1.5 min every 25 min throughout the day). Increasing the fertigation frequency significantly increased the plants' acquisition of nutrients, especially phosphorus and manganese. A significant linear regression was obtained between aboveground biomass, and leaf P concentration in the early vegetative stage. Based on the linear regression, 96% of the dry weight variations could be explained by differences in leaf P concentration, indicating that the main effect of fertigation frequency was related to improved P mobilization and uptake. Increasing the daily fertigation frequency from two to eight and to 30 applications reduced the number of BER fruits from 7 to 3 and to 2 per plant, respectively, and accordingly, increased the yield of export-quality fruits from 6.5 to 10 and to 10.5 per plant, respectively. The Mn concentration in plants exposed to low fertigation frequency were low, probably in the deficiency range, but they increased with increasing fertigation frequency. A negative correlation was found between the accumulated number of BER-affected fruits throughout the experiment and fruit-Mn concentrations. In light of recent findings that BER effects in the fruit tissue include the production of oxygen free-radicals and diminution of anti-oxidative compounds and enzymatic activities, and the known crucial role of manganese in enzyme activities and in detoxification of oxygen free-radicals, the relationships between BER incidence and fruit-Mn concentration may indicate that BER is related to Mn deficiency. Future researches are needed to validate this hypothesis.