Abstract
Soil suppressive to the soybean cyst nematode (SCN), a major yield-limiting pathogen of soybean, plays an important role in biological control. Field and greenhouse experiments were conducted to evaluate the effects of tillage, crop sequence, and biocide application on SCN suppression in corn-soybean cropping systems in Minnesota. The experiment was a split-plot design with no-tillage and conventional tillage as main plots, and six crop-biocide treatments (CRCS, CSCS, SSSS, SSSS + streptomycin, SSSS + captan, and SSSS + formaldehyde – the four letters represent crops in 2009 to 2012, respectively; C is corn, R is SCN-resistant soybean, and S is SCN-susceptible soybean) as subplots with four replicates. Soil samples were taken from each plot at planting, midseason, and harvest each year for SCN egg counts, and soybean yield was determined. In addition, soil samples collected from each plot at midseason were assayed for suppressiveness to SCN. Tillage had minimal effect on SCN population density and soybean yield. Annual rotation with corn reduced SCN population density, but also reduced soil suppressiveness as SCN egg population density increased in the following SCN-susceptible soybean compared with soybean monoculture. Rotation with SCN-resistant soybean and corn was the most effective in reducing SCN population density. The bactericide streptomycin did not affect SCN populations but the fungicide captan increased SCN population density. The biocide formaldehyde was the most effective in reducing the level of suppressiveness to SCN. The greenhouse study confirmed that the soil was suppressive to SCN, but failed to detect effects of tillage, crop sequence, and biocide field treatments. This study demonstrated that the soil in the fields was suppressive to the SCN, and biological agents, especially fungal antagonists, were involved in nematode suppression.
Highlights
Biological control, Captan, Crop rotation, Formaldehyde, Heterodera glycines, Nematode-suppressive soil, Soybean, Soybean cyst nematode, Streptomycin, Tillage
We investigated the effect of tillage, crop rotation, and biocide treatments on soybean cyst nematode (SCN) soil suppression in the field, and validated soil suppression in subsequent greenhouse bioassays
Conventional tillage increased soybean yield (3.89%) only in the second year at Site 1, but decreased soybean yield (7.38%), the first year at Site 2
Summary
Biological control, Captan, Crop rotation, Formaldehyde, Heterodera glycines, Nematode-suppressive soil, Soybean, Soybean cyst nematode, Streptomycin, Tillage. Soybean cyst nematode (SCN), Heterodera glycines nematode has become a major yield-limiting factor in Ichinohe, is widely distributed throughout most soy- soybean production and causes an estimated annubean producing regions in the world (Riggs, 2004) This al yield loss of about $1 billion in the USA Reduction of SCN population densities by no-tillage is reported from field experiments in western Kentucky (Hershman and Bachi, 1995) and Indiana (Westphal et al, 2009) These individual experiments agree with a survey of the north central USA (Workneh et al, 1999). These differences may be due to different cropping systems, soil types, environmental conditions, and their interaction with the nematode
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