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Additionally, the positive coefficients for plant height demonstrate a positive linear relationship between SCN population density and mean plant height at 40 DAP. Adjusted R2 was 0.73, showing experiment and mean plant height accounted for 73% of variation in SCN egg population density. At 70 DAP Experiment 1, the linear regression of SCN population density on mean plant height produced a significant model (P �� 0.001) with the following equation: The positive slope coefficient for plant height was also significant (P �� 0.001), indicating a positive relationship between plant height and SCN population density (Fig. 5). However, the adjusted R2 was 0.175, suggesting the model accounted for only 17.5% of variation in SCN egg population. Fig. 5 Linear regression of soybean cyst nematode (SCN) egg population density on mean plant height (both at 70 d after planting��Experiment thiram 1). The regression of SCN population density on plant mass at 70 DAP Experiment 1 also produced a significant (P �� 0.001) model as follows: The positive slope coefficient for plant mass was also significant (P �� 0.001), indicating a positive relationship between plant mass and SCN egg population density (Fig. 6). However, adjusted R2 was 0.198, meaning the model accounted for only 19.8% of variation in SCN population density. Fig. 6 Linear regression of soybean cyst nematode (SCN) egg population density on plant mass (both at 70 d after planting��Experiment 1). Discussion Organic soil amendments��including pennycress seed powder, selleck inhibitor marigold plant material, Cuphea plant material, condensed distiller��s soluble, and canola meal��effectively reduced SCN population density in this study. However, except for canola meal and pennycress seed powder in Experiment 1, amendment efficacy against SCN dissipated by 70 DAP or approximately two generations. This suggests effective amendments caused Protein Tyrosine Kinase inhibitor an acute SCN population density reduction event, possibly because of nematoxic compounds, but SCN population density rebounded after two generations. Short-term amendment efficacy suggests nematicidal compounds in amendments were not persistent long term in the soil (Oka, 2010). In this greenhouse study where soybean root density was high and environmental conditions were managed, SCN egg density was very high by 70 DAP averaging 168,000 eggs/100 cm3 soil. Field conditions��including temperature extremes, water stress, lower root density��rarely support such high SCN population densities (Chen et al., 2001a; Porter et al., 2001; Chen and Liu, 2007; De Bruin and Pedersen, 2008; Rotundo et al., 2010), so amendments may suppress SCN for longer duration at lower SCN population densities that would be present in the field. Despite only short-term SCN suppression in this study, application of soil amendments may still aid in limiting soybean damage from SCN by reducing early SCN infection.