Período anterior a interferência das plantas daninhas na cultura da cenoura com e sem mulch de palha de aveia preta

Abstract

The carrot (Daucus carota L.) stands out among the vegetables produced in the central-eastern region of Paraná, however, weed interference represents one of the factors that have the greatest impact on the reduction of crop productivity. Therefore, the objective of this work was to determine the period prior to interference (PAI) for Alvorada carrot grown with and without black oat mulch under the soil. The experiment was installed at Fazenda Escola Capão da Onça, in the spring of 2016, with a randomized block design in a 2X5 factorial scheme with 5 replications. The first factor consisted of soil cover with mulch (10 t ha-1 of black oat straw) and no mulch, while the second factor corresponded to five periods of weed cohabitation with the crop (0, 15, 30, 60 and 110 days after the emergency). In the experiment, 10 weed species belonging to 7 botanical families were identified, in which the main ones were Euphorbia heterophylla, Galinsoga ciliata, Eragrotis pilosa, Rhaphanus raphanistrum and Braquiaria plantaginea. The diameter of the carrot roots in both the mulch and mulch plots decreased exponentially over the periods with coexistence with the weeds, with losses of up to 68.51% and 74.57% in relation to the weed beds with mulch. without mulch respectively. The length of the carrot roots in both the mulch and mulch plots reduced linearly over the periods with coexistence with the weeds, with losses of up to 65.91% and 81.5% in relation to the controls in mulch beds. without mulch respectively. The extraction of all evaluated macronutrients (N, P, K and S) were negatively influenced by the coexistence with weeds. The higher levels of coexistence with weeds provided less accumulation of nitrogen, phosphorus, potassium and sulfur in the shoots and roots of carrot plants. The nutrient content most affected by the matocompetition interference was K; in the aerial part losses were observed up to 64.69% and 68.11% in relation to the weed witnesses in the beds with mulch and without mulch respectively and losses in the root of up to 68.68% and 61.52% in relation to weeding witnesses in the beds with mulch and without mulch respectively. The use of the mulch was efficient to increase K content in the aerial part in 13.02% in the weeded witnesses in relation to the weed witnesses in beds without mulch, as well as, during all periods of coexistence. This trend continues for the other nutrients and it has been observed that small reductions in nutrient content in the plant greatly affect productivity in the first 15 (AED). The growth of carrot plants was negatively influenced by weed interference, especially at the beginning of development after 15 (DAE), when the greatest difference in growth speed (TCA) between weed and cohabitation with weeds. The highest TCA was observed in the weed control in the mulch beds and a reduction of 19.80% in the mulch weed control in relation to the mulch weed control, however, in the plants living with weeds the TCA did not evolve over the years. periods of coexistence with the bush. The relative growth rate (TCR) decreased exponentially after 30 (DAE) for all treatments. The highest values were observed in mulch and mulch seedlings and 8% reduction in mulch weed control and 12%, 20% in mulch and mulch seedlings respectively. The net assimilation rate (TAL) was higher in the mulch weed control with a reduction of 30.23% in the weed control without mulch and in the coexisting plants 34.11%, 53.49% in mulch and mulch, respectively. In the root mass ratio (RPR), the weeds in mulch beds obtained a higher ratio with 0.6 (g -1) or 60% of the dry mass at the root, with a 3.3% reduction in weed control in mulch ; 10% in plants living with weeds in beds with mulch and 15% in plants living in beds without mulch in relation to mulch weeded controls. The loss of total root yield was 97.67% in mulch and 94.51% in mulch. The period prior to the interference was 3 and 4 (DAE), considering the total productivity for the crops with and without mulch respectively, and 3 and 3 (DAE) considering the commercial productivity for the crops with and without mulch respectively.