Field experiments were conducted to study the possibility of reducing the negative effects of irregular high temperatures (IHT) >30oC on the growth of hard head lettuce and pea plants during one growing season by reducing fertigation solution concentration (FSC) to minimize the chance of plants being exposed to salt accumulation in the plant root zone.
The experimental area was divided into six plots to receive the following FSC treatments: 100, 90, 80, 70, 60, and 50 % of the recommended fertilization rate (RFR) for each crop.
A significant increase was revealed in the yield, fresh weight and diameter of marketable lettuce heads as affected by reducing FSC levels to 70 % from RFR of the lettuce crop. Similar trends were obtained for pea crops in some of its growth parameters such as seed weight and pod production. The contents of N, K, Ca and Mg in lettuce and pea leaves decreased with decreasing FSC treatments. Chlorophylls (A, B and total), and β-carotene contents increased with decreasing FSC treatments to 70 % of RFR. Data showed a significant reduction in the concentrations of superoxide dismutase (SOD), peroxides (POD), Polyphenol oxides (PPO) and proline in both lettuce and pea with decreasing FSC treatments to 70 % then decreased with decreasing FSC treatments lower than 70 % of RFR.
It could be concluded that the reduction in FSC to 70% from the RFR led to an increase in plant resistance to IHT, improved crop yield and economical benefit/cost ratios of lettuce and pea crops grown under IHT.