Manejo nutricional e práticas de raleio como estratégias para o aumento da produtividade e qualidade dos frutos de Prunus persica

Abstract

Costs reduction and high efficiency are challenges that the production sector will have to face in the next decades. Strategies aming to increase peach productivity and fruit quality in southern Brazil, may include two cultural practices: fruit thinning and nutrient management of plants. Therefore, this study aimed at evaluating new fruit thinning techniques and the management of plant nutrition in the search for production efficiency and maintenance of Prunus persica quality. Assays were reported in the following eight papers. Article 1, whose title is “Mechanical flower thinning in peach trees”, aimed at evaluating effects of mechanical thinning on flowers in peach trees by different equipment. Results showed that peach production was affected by mechanical flower thinning and that pruning shears (Carpa Electro® ) and trimmers are efficient not only to carry out mechanical thinning but also for reducing the time needed for this task. Article 2, which is entitled “Mechanical thinning as an alternative in peach tree cultivation”, evaluated the efficiency of mechanical thinning carried out by pruning shears (Carpa Electro® ) and trimmers in fruits and flowers of peach trees. Both apparatus were found to be efficient to carry out thinning and to decrease operational time. Manual fruit thinning and mechanical flower thinning by a trimmer led to increase in both productions per plant and fruit diameter. Article 3 – Mechanical fruit and flower thinning in peach trees – aimed at testing the efficiency of two mechanical apparatus in fruit and flower thinning in peach trees and their influence on production characteristics and fruit quality. Results showed that mechanical thinning associated with manual thinning in peach trees is a viable alternative to replace manual fruit thinning. Both apparatus under investigation may be used for carrying out thinning in peach trees, since they affect neither production rates nor fruit quality. Article 4, entitled “Nitrogen fertilization on productivity and mineral composition of peach tree genotypes”, aimed at evaluating effects of nitrogen maintenance fertilization on mineral composition of leaves, plant development and production of different genotypes of peach trees grown at high densities. The best N dose could not be determined, since doses up to 180 Kg ha-1 were not enough to reach maximum yield. Increase in N doses also increases N content on leaves, but nitrogen fertilization does not affect leaf contents of potassium, calcium and magnesium. Article 5 – “Nitrogen fertilization associated with cold storage and its impacts on the maintenance of peach quality” – evaluated the effects of the association between doses of nitrogen fertilization and different cold storage periods on physicochemical and phytochemical characteristics of peaches in the post-harvest period. The more N in the soil and the longer the storage period, the more phenolic compounds and antioxidant activity decrease. Article 6, whose title is Potassium fertilization and its impact on production and mineral composition of peach trees”, aimed at evaluating production parameters of peach trees submitted to different doses of potassium fertilization and at establishing its critical level in soil and on leaves. Potassium fertilization increased potassium contents on two layers of soil depth (0-10 and 10-20 cm deep) and on peach tree leaves. Peach tree productivity was affected by potassium application and the critical level established between production and K content was 28.4 g kg-1 on peach tree leaves. Article 7, entitled “Effect of potassium fertilizers associated with cold storage on peach quality”, aimed at evaluating effects of the association between doses of K fertilization and different cold storage periods on physicochemical and phytochemical characteristics of peaches. Doses of 40 and 160 kg ha-1 K2O led to high contents of phenolic compounds and antioxidant activity, while 160 kg ha-1 K2O decreased mass loss after 20 + 1 storage days. Pulp firmness, phenolic compounds, antioxidant activity and carotenoids of peaches decreased throughout cold storage. Article 8, whose title is “Organic fertilization and fruit load on mineral composition, production and quality of nectarines in Italy”, it aimed at evaluating efficiency of organic fertilizers in two nectarine cultivars with high and low fruit loads in order to analyze their effect on soil, plant nutritional status and production rates. Cattle manure and its compost affected ammonium and nitrate concentrations in the soil. Organic fertilization did not influence production per plant, number of fruits per plant, fruit mass and soluble solids in any cultivar. Results of this study represent an opportunity to consolidate new thinning practices and nutrient management of plants as a technological response to help the production chain of Prunus persica.