Assisting smallholder farmers in adopting integrated nematode-soil health management: Changes in soil physiochemistry


This presentation was shared by the team for Managing nematodes and soil health in Guatemala, led by Brent Sipes. The presentation reviews the experimental research conducted that evaluates the relationship between soil physiochemistry and nematode populations. The objective of this is study is to show how various soil amendments can affect soil health.

Experimental design

Soil health was evaluated by designing eight different treatments across two soil types for a total of 16 experimental treatments. The treatments started with three different levels of composted chicken manure (0, 318, or 354 kg/ha), which either included or excluded a biological additive (1.8 kg/ha Puprpureum and Bacillus treatment). These combinations were then tested on two kinds of soils: andisols and mollisols. Across all 16 treatments, the study measured nematode populations as well as soil properties based on important nutrients including potassium (K), carbon to nitrogen ratios (C:N), and the pH.


The Soil Food Web model was used as an applied decision-making tool, where the results of the soil assessment can inform what action should be taken for improved managemet. This tool typifies soils into four categories based on nitrogen availability over time – a crucial indicator for soil health and crop production. Using this model, the best-case scenario is one where nitrogen is available and steady, whereas the worst-case scenario is one where nitrogen is depleted. Intermediate scenarios are ones where nitrogen is available but only in a boom-bust cycle, or where nitrogen is not depleted but it is not available due to low biological activity.


Across all of the treatments in both kinds of soils, the nitrogen levels were considered neither best nor worst case. Instead, nitrogen was not depleted, but it needed biological activity in order for it to be made available. The study concludes that additional work will need to be done to determine how to get soils into the ideal scenario where nitrogen is available at a steady rate.