Combined Effects of Soil Biotic and Abiotic Factors, Influenced by Sewage Sludge Incorporation, on the Incidence of Corn Stalk Rot

Abstract

The objectives of this study were to evaluate the combined effects of soil biotic and abiotic factors on the incidence of Fusarium corn stalk rot, during four annual incorporations of two types of sewage sludge into soil in a 5-years field assay under tropical conditions and to predict the effects of these variables on the disease. For each type of sewage sludge, the following treatments were included: control with mineral fertilization recommended for corn; control without fertilization; sewage sludge based on the nitrogen concentration that provided the same amount of nitrogen as in the mineral fertilizer treatment; and sewage sludge that provided two, four and eight times the nitrogen concentration recommended for corn. Increasing dosages of both types of sewage sludge incorporated into soil resulted in increased corn stalk rot incidence, being negatively correlated with corn yield. A global analysis highlighted the effect of the year of the experiment, followed by the sewage sludge dosages. The type of sewage sludge did not affect the disease incidence. A multiple logistic model using a stepwise procedure was fitted based on the selection of a model that included the three explanatory parameters for disease incidence: electrical conductivity, magnesium and Fusarium population. In the selected model, the probability of higher disease incidence increased with an increase of these three explanatory parameters. When the explanatory parameters were compared, electrical conductivity presented a dominant effect and was the main variable to predict the probability distribution curves of Fusarium corn stalk rot, after sewage sludge application into the soil.

Contribution of organic amendments to soil properties and survival of Stenocarpella on maize stalk

“…The increase in Ca content is related to the Ca content in wastes, around 20, 49, and 41 g kg -1 in sewage sludge, poultry litter, and swine manure, respectively (Table 1). Considering the negative correlation between Ca and Ct (Table 3) observed in the assay conducted in Sete Lagoas, the nutrients may definitively have an impact on the pathogen establishment, as previously demonstrated for Fusarium graminearum, another necrotrophic pathogen of maize that is favored by the Mg content buildup in the soil (Ghini et al, 2016). Ghini et al (2016), in a study that incorporates two types of sewage sludge into the soil, observed that the incidence of maize stalk rot caused by Fusarium graminearum was directly proportional to the content of sewage sludge applied to the soil and with the increasing Mg content.…”

“…Considering the negative correlation between Ca and Ct (Table 3) observed in the assay conducted in Sete Lagoas, the nutrients may definitively have an impact on the pathogen establishment, as previously demonstrated for Fusarium graminearum, another necrotrophic pathogen of maize that is favored by the Mg content buildup in the soil (Ghini et al, 2016). Ghini et al (2016), in a study that incorporates two types of sewage sludge into the soil, observed that the incidence of maize stalk rot caused by Fusarium graminearum was directly proportional to the content of sewage sludge applied to the soil and with the increasing Mg content. Although nutrients could be limiting factors in stalks (Torma et al, 2017), when supplied at higher amounts, such as those amended in poultry litter, nutrients may lead to Stenocarpella inoculum buildup.…”

“…These organic wastes also interfered with the Sternocarpella inoculum in maize stalks (Figure 2). The potential of organic residues to change the soil characteristics has been reported in numerous studies (Baker and Cook, 1974;Lazarovits et al, 2009;Bonanomi et al, 2007;Ghini et al, 2016).…”

“…After poultry litter and sewage sludge application, the Ca content was changed in the assay conducted in Lavras, according to the soil classification of Alvarez et al (1999). Other studies showed changes in Ca content when sewage sludge and swine manure were incorporated into the soil (Ghini et al, 2016;Choudhary et al, 1996).…”

Soil properties related to suppression of Rhizoctonia solani on tobacco fields from northwest Argentina

“…Thus, the high pH (greater than 7) found in CH tobacco fields in the present study could have been a limiting factor for the development of R. solani inoculum potential. Interestingly, in previous research, high SOM and clay contents were also related to soil suppression of other soilborne pathogens, such as Fusarium (Ghini et al , ) and the oomycete Pythium (Löbmann et al , ). These reports support the idea that these abiotic properties contribute to the general suppression (fungistasis) by soil of different phytopathogens, including R. solani .…”