Potássio, fósforo, boro e irrigação na distribuição espaço-temporal da cercosporiose do cafeeiro

Abstract

Brown eye spot (Cercospora coffeicola) is one of the major diseases of coffee, and its occurrence affected the supply of water and nutritional imbalance. The supply of water, which is primarily carried out by rain, but can be done by drip irrigation or sprinkling. Poor or unbalanced mineral nutrition may predispose plants to infection by the fungus. Little is known about the influence of mineral nutrition, particularly in relation to the elements boron (B), phosphorus (P) and potassium (K), and soil fertility in the intensity of the disease and its spatial distribution. Thus, three experiments were carried out in the field, being the first experiment aimed to evaluate the interaction between water slides with different phosphorus levels (5 irrigation depths x 4 levels of phosphorus). Evaluations were performed on leaves of brown eye spot every 30 days. The average progress curve of the incidence of brown eye spot varied between the two years, in Year 1 (November 2011 to December 2012), the incidence of brown eye spot peaked at 22/08/2012 (22.45%) while, in Year 2 (January 2013 to January 2014), the incidence reached its highest level in the evaluation on 12/09/2013 (16.29%). There was interaction between irrigation and phosphorus levels in the evaluation held in 10/07/2012. Increased levels of P in smaller irrigation levels and in the absence of phosphate fertilizers in higher irrigation levels was obtained higher incidences. In the second experiment aimed to evaluate the interaction between doses of K and B (4 doses of K, with 0, 100, 200 and 400 kg/ha of K x 4 doses of B, the doses being 0, 1, 2 and 4 kg/ha B). They performed Twenty-four evaluations of brown eye spot on coffee leaves, every 30 days. The average progress curve of the incidence of brown eye spot was between the two years of evaluation. The peaks of incidences occurred in 28/02, 23/05 and 12/09 of 2013, 24/02 and 22/05 of 2014 respectively. In 2014, the incidence was lower compared to the year 2013, even with high load pending, possibly because the largest recorded temperatures. There was a significant interaction between doses K and B with the area under the impact of the progress curve (AACPI) in which doses above 200 kg/ha of K at doses below 1 kg/ha of B showed the higher levels of disease. And in the third experiment aimed to evaluate the spatial pattern of the relationship of brown eye spot with soil fertility and plant nutrition in irrigated coffee crop drip and center pivot. In two experimental areas, one with a drip irrigation system of 11 ha, with 52 georeferenced sampling points, and the other central pivot area of 17 ha, with 50 sampling points. At each point leaves the five plants was evaluated every 60 days. There was a positive correlation with the incidence of AACPI on 04/17/2013, 08/24/2013, 06/04/2014 and 18/08/2014, and foliar B, P and K. In geostatistical analysis for the system drip irrigation, the list of variables for 2014, the right side of the area, the lowest yields were observed, the highest intensities of gray leaf spot and major foliar K, P and B while for the system by central pivot, in list of variables for 2014, the right side of the area, the lowest yields were observed, the highest intensities of gray leaf spot and higher foliar P and K and lower content of B.