Impact of Potassium Pre-Harvest Applications on Fruit Quality and Condition of Sweet Cherry (Prunus avium L.) Cultivated under Plastic Covers in Southern Chile Orchards

Abstract

In rainy locations, sweet cherry is cultivated under plastic covers, which are useful to prevent fruit cracking but decrease cherry quality such as firmness and acidity. Here we evaluate the impact of pre-harvest K foliar applications on harvest and post-harvest fruit quality and condition of sweet cherry cultivated under plastic covers in southern Chile orchards. The study was performed on two commercial orchards (cv. Regina), located in different regions, during two consecutive seasons. In all cases, a conventional K regime (four sprays) was compared to an intensive K regimen (seven sprays). Results showed that cherries from the most southern region revealed lower acidity but higher soluble solids content weight and size. The intensive K regime improved the firmness and acidity of fruits of covered trees at harvest and post-harvest. Moreover, we found that condition defects were higher in fruits from un-covered trees and that trees grown under intensive K regime showed lower levels of cracking at harvest and pitting at post-harvest compared to trees treated with the conventional K regime. Otherwise, pedicel browning was inconsistently affected by K sprays. Our results revealed that an intensive K regime could improve the quality and condition of fruits at harvest and post-harvest in covered orchards of sweet cherry cv. Regina; however, the impacts can significantly vary depending on season and locality.

Plastic Covers and Potassium Pre-Harvest Sprays and Their Influence on Antioxidant Properties, Phenolic Profile, and Organic Acids Composition of Sweet Cherry Fruits Cultivated in Southern Chile

“…Our results on the composition of organic acids in Regina fruits revealed that the sum of organic acids detected in Regina fruits (malic, citric, tartaric, and oxalic) ranged from 1.19 to 1.51 g kg −1 of FW, depending on the treatment. These values were around 10-times lower than those reported by Kelebek and Selli [ 32 ], which could be explained by the reduced acidity of sweet cherry fruits produced in southern Chile previously reported by Bustamante et al [ 20 ] and Villavicencio et al [ 81 ]. In addition, we found that malic acid was the most abundant organic acid in fruits, followed by tartaric acid, oxalic acid, and citric acids.…”

“…The use of plastic covers is one of the strategies used to mitigate the negative impacts of rainy weather on sweet cherry fruit production and quality. Although covers are useful in overcoming the harmful effect of rainfall during the bloom period and before harvest [ 36 ], they decrease fruit firmness and acidity [ 10 , 20 , 37 ], thus reducing fruit quality and overall condition. Otherwise, potassium (K) has been described as an important regulator of several parameters related to fruit yield and quality due to its functions as a catalyst and enzyme activator in different protein reactions and carbohydrate metabolisms [ 38 , 39 ].…”

“…In plants, these nutrients play a key role in osmotic regulation, cell division, organic acids neutralization, starch and sugar formation, protein synthesis, and photo-assimilate transport [ 40 ]. Recently, we found that an intensive regime of K foliar supply, consisting of 7 sprays during the season, applied from the straw-yellow fruit skin color phenological stage, was useful to increase the quality and condition of sweet cherry fruit produced in covered orchards in the South of Chile [ 20 ]. In agreement with our previous work, our current study showed that sweet cherries (cv.…”

“…A complete discussion about the impact of plastic cover and K foliar supply on the quality and condition of sweet cherry was included in Bustamante et al [ 20 ]. Currently, we also investigated the impact of the canopy zone, related to fruit exposition to light, on sweet cherry quality and composition.…”

“…Adequate K fertilization has demonstrated to increase fruit firmness, caliber and weight, soluble solid content, and acidity in sweet cherries cultivated in Turkey [ 19 ]. We recently found that, despite the fact that plastic covers are useful to reduce fruit cracking in Regina sweet cherry fruits cultivated in Southern Chile, covering caused a significant reduction of fruit firmness and acidity at both harvest and post-harvest stages, which were mitigated by using an intensive K foliar regime [ 20 ].…”