Potassium nutrition as a strategy to mitigate salt stress in melon grown under protected cultivation

Abstract

The use of saline water is one of the major challenges of agriculture, as it can cause nutritional imbalances and thus reduce crop yield. This study proposes to examine the efficiency of potassium nutrition as a salt stress-mitigating agent in melon grown in a protected environment. The experiment was laid out in a randomized-block design with ten treatments in a 2 × 4 factorial arrangement represented by two melon cultivars (McLaren and SV1044MF) and four nutrient solutions (S1 - standard nutrient solution, 2.5 dS m-1; S2 - nutrient solution salinized with NaCl, 5.0 dS m-1; S3 - nutrient solution salinized with NaCl + 50% K, 6.5 dS m-1; and S4 - nutrient solution salinized with NaCl + 100% K, 7.5 dS m-1). Yield (average fruit weight, production, fruit diameter, internal cavity, and pulp thickness), quality (pulp firmness, total sugars, soluble solids [SS], vitamin C, pH, titratable acidity [TA] and SS/TA ratio) and nutritional (K, Na and K/Na ratio) variables were evaluated. Plants fertigated with standard nutrient solution showed the highest values for fruit weight (1,190.6 g), production (2,381.3 g per plant), fruit diameter (13.6 cm) and pulp thickness (2.6 cm). Cultivar McLaren produced heavier fruits (931.4 g) with larger diameter (12.4 cm) and pulp thickness (2.4 cm). The addition of NaCl to nutrient solution induced a reduction in the yield variables but did not influence fruit quality. The addition of extra K to salinized nutrient solution did not mitigate the deleterious effect of salinity on the yield of melon.

Post-harvest quality of melon accessions subjected to salinity

“…Analysis of variance of the characteristics FM-fruit mass (g); TP-total production (g); FF-fruit firmness (N); PF-pulp firmness (N) L-length (cm); W-width (cm); IC-internal cavity (mm) and PT-pulp thickness (mm) of genotypes A24, A35 and Sancho the of melon (Cucumis melo L.) produced in saline conditions (0; 1.5; 3.0; 4.5 and 6.0 dS m -1 ). with tolerance to transport, and these results are similar to those found by , Dias et al (2018) and Oliveira et al (2021).…”

“…An adequate fit was not possible in Figure 2B with ŷ = 0.4091ECw + 10.202 and R 2 = 0.55. The linear increase in fruit and pulp firmness (Figures 2A and B), with increasing salinity is an important quality indicator, since fruits with greater firmness are more resistant to mechanical injuries during transport and marketing (Oliveira et al, 2021), in addition to longer shelf life and post-harvest conservation. This result being similar to those observed by Pereira et al (2017), Morais et al (2018a) and Oliveira et al (2021).…”

“…There is little information in the literature on the composition of flavonoids in melon pulp Mallek-ayadi et al (2017). andAli and Ismail (2014) found an increase in the concentration of flavonoids in tomato fruits after application of salinity.Increasing EC doses of irrigation water increased vitamin C with a positive linear effect only between doses (Figure6C) Oliveira et al (2021). found an increase in vitamin C levels when submitted to a second dose of salinity.…”

“…The titratable acidity was significant only as a function of the ECw of the irrigation water (Figure 5A). Oliveira et al (2021) also showed that increasing levels of salinity increased titratable acidity. Possibly because salinity has a direct effect on the total titratable acidity of the fruits, since the increase in acidity is related to the nutrition provided to the crops (Prado, 2008).…”

Agronomic Performance and Fruit Quality of Yellow Melon Fertilized With Doses of Nitrogen and Potassium

“…This increase in the concentration of sugars in the fruit may be associated with the role that K plays in apoplastic co-transport during the sucrose loading between the mesophyll and the phloem (WHITE; KARLEY, 2010). The literature is rich in approaches that confirm the positive effect of an increase of K on TSS in this crop, as found in Lin, Huang and Wang ( 2004), Demiral and Köseoglu (2005), Bouzo, Céccoli, and Muñoz (2018), Yang et al (2019) and Oliveira et al (2021). Thus, maintaining an adequate supply of K for melon plants ensures a better quality of the fruits, with regard to the degree Brix.…”