Current orange tree cultivation practices in the Brazilian State of Amazonas present several production problems, being the inadequate weed management the most important one, and significantly affecting fruit productivity. However, if weeds are managed properly, their coexistence with orange cultivars does not affect the fruit yield of orange trees. Thus, the objective of this research was to identify the period of longer weed interference in orange production. The treatments were conducted during the 2013 and 2014 harvests as follows: one control treatment with no coexistence of weeds and crop throughout the growing season; and six periods of coexistence (October to January, February to May, June to September, October to May, October to January, June to September, and February to September). The coexistence of weeds from October to May with orange trees increased the fall of unripe fruits and reduced the yield and the number of oranges per plant. Therefore, this period was considered as the most critical one for the control of weeds in orange trees.

AbstracThe productivity of citrus plants has not reached its maximum potential due to the action of several factors that directly affect agricultural profitability. Among these factors, weed interference has a great importance since it causes a reduction in crop productivity. The aim of this study was to assess the effect of different cover crops on suppression of weeds in an orange orchard. The research was conducted in a commercial orange production area located in Rio Preto da Eva, AM, Brazil. The experimental design was a randomized block design with six treatments and four replications. Treatments were control, millet, jack bean, forage turnip, brachiaria, millet + jack bean. The evaluated characteristics were weed density, soil cover percentage, total weed dry matter, total cover plant dry matter and growth indices (leaf area index, leaf area ratio, and specific leaf area). Cover plants provided a good dry matter production and had a suppressive effect on weed growth, except for forage turnip. Brachiaria and jack bean presented the highest values of leaf area index and leaf area ratio.

The cultivation of orange trees in Amazonas, Brazil relies predominantly on grafted plants combining ‘Pera’ scion and ‘Rangpur’ lime rootstock. Alternative rootstocks better adapted to the conditions of the region have not been investigated. Therefore, the objective of this research was to test seven rootstocks for the production of high-quality oranges under the typical conditions of the Amazon. Citrus production was evaluated from May to August between 2017 and 2019, based on the variables of cumulative yield, yield efficiency, and crop-yield index over the study period. The fruit physicochemical quality was evaluated by quantification of total soluble solids, total titratable acidity, ratio, juice percentage, and technological index. ‘Indio,’ ‘BRS Bravo’, and ‘Riverside’ genotypes combined with ‘Pera’/CNPMF scion had the highest yield and good fruit quality. They are potentially the most suitable combinations to grow sweet oranges in the Amazon.

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