Soybean yield and Asian rust(Phakopsora pachyrhizi) severity affected by foliar sprays of potassium sourcesand tebuconazole doses

by de Oliveira, Angelo Fernandes

Abstract (Summary)
Of macronutrients cited in scientific literature, the potassium is the element thatpresents consistent positive results in the reduction the incidence of pests and diseases.Reports show that nutrition potassica adequately reduced the severity of more than 20diseases bacterial, more than 100 diseases fungal and of 10 diseases caused by virusesand nematoides in diverse cultures. Thus, this study evaluated leaf sprays of potassiumsources associated with different doses of the fungicide Tebuconazole (200g a.i. l-1), itseffect on soybean Asian rust (Phakopsora pachyrhizi) severity and progress and ongrain yield. The experimental design was randomized blocks, in a 5 x 4 factorialscheme, using four potassium sources (Nitrate, Sulfate, Phosphite, Silicate), and a nonsprayedcontrol, and four fungicide doses (0, 250, 500, 750 ml ha-1), in a total of 20treatments. The doses of each fertilizer was determined based on the application of 200g ha-1 potassium on the first and second sprays, and 400 g ha-1 potassium on the thirdspray, in a total of 800 g ha-1 potassium. Previously inoculated soybean (M-Soy 8001)was sown on December 05 2006. The following yield components were evaluated:yield, weight of 1,000 grains, agronomic efficacy of the K sources, and efficacy onsupplying K, rust severity and area under the disease progress curve (AUDPC). Thespraying of different potassium sources did not affect soybean yield significantly;potassium silicate was the source with greatest agronomic efficacy and greatest efficacyon potassium supply; rust severity, evaluated on soybean stage R5.4, was slightlyreduced on the lower third in the treatments with potassium sources, regardless of theassociation with the fungicide.
This document abstract is also available in Portuguese.
Bibliographical Information:

Advisor:Carlos Ribeiro Rodrigues; Lísias Coelho; Antonio Nolla; Regina Maria Quintao Lana

School:Universidade Federal de Uberlândia

School Location:Brazil

Source Type:Master's Thesis

Keywords:Phakopsora pachyrhizi Fungicide doses Potassium sources Foliar nutrition Ferrugemasi√°tica


Date of Publication:09/03/2007

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