Atributos do solo e qualidade de frutos nos sistemas convencional e orgânico de produção de maçãs no Sul do Brasil1

Abstract

The present study aimed to evaluate the physical, chemical and biological characteristics of the soil, and the mineral composition and quality of the fruit, in orchards of 'Royal Gala' apple, under conventional (CON) and organic (ORG) production systems, in a Haplic Nitisol. Under ORG, the soil in the cultivation furrow showed better physical quality (higher values for aggregate stability, saturated hydraulic conductivity and porosity, and lower density), chemical quality (lower acidity and higher values of exchangeable Ca and Mg, total organic carbon (TOC) and total nitrogen (TN)) and biological quality (higher values for microbial biomass carbon (Cmic) and ratio of Cmic to TOC), in the 0-20 cm layer compared to CON. Because under the ORG system synthetic chemicals for breaking dormancy were not used, commercial fruit harvesting took place one month after that of the CON system. Despite this difference in the time of harvest, fruit grown under the ORG system have, when harvested, a lower starch-iodine index and higher values for firmness and soluble solid content, when compared to values obtained in fruits grown under the CON system. Fruit under ORG has a higher percentage of red skin coloration, but more severe russeting, in relation to that under CON. During conventional cold storage (four months at 0 ± 0.5 o C / 90-95% RH), fruit grown under the ORG system show a high loss in pulp firmness, which may be associated with the high levels of K and Mg in the pulp and of N in the skin, compared to fruit grown under the CON system. Therefore, even under the ORG system, the supply of these elements may be too high, compromising the preservation of the postharvest quality of the fruit.