WHAT’S NEW
Debunking myths around soil fumigants and their impact on soil health Soil fumigation has been an important tool in New Zealand crop production for decades because it is highly effective at managing soil pests that cause crop disease. However, it is often criticised for being detrimental to soil health. There is a persistent myth that soil fumigants harm the microbiological diversity and abundance of beneficial microbes in the soil, despite extensive evidence to the contrary. In light of a global focus on agricultural sustainability, it is essential to understand the real impacts of soil fumigants on soil health, using sciencebased criteria and the best technology available. Major advances in automated, genetic sequencing technology combined with commercially available services, such as Biome Makers (www.biomemakers.com), can now provide a detailed and comprehensive analysis of the types and relative abundance of microorganisms in the soil. Dr John Washington, a plant pathologist and microbiologist, is research and development director in the Trical Group, based in Florida in the United States. “I have enthusiastically embraced these new and powerful tools that allow us to study and characterise the soil microbiology genome in soils treated with our soil fumigant products globally,” he says. “It’s a kind of genetic barcoding: the technology can identify every organism group and their relative amounts. We can compare treated versus non-treated soils, soil fumigants versus fumigant alternatives, and the dynamics of soil microbiology and how it changes over time following any agricultural input. These tools are key in allowing the scientific and agricultural community to more fully understand the soil biology component of soil health in an objective and scientific manner, looking for positive or negative effects of our inputs and whether or not we can manipulate the soil biome to enhance crop production. Concurrently it allows us to get past the old myths and gross misinterpretation of soil fumigant impacts, for instance, and focus on specific and real effects.” 66
The ORCHARDIST : MAY 2022
Soil treatment for apples
“For example,” John says, “microbiome analysis shows that soil-applied chloropicrin and 1,3-dichloropropene alter the soil biology in important but non-destructive ways. Across different crops and locations including apples and blueberry in Michigan, and ornamental and vegetable crops in Florida, our research is clearly showing that Trichoderma, a well-known group of beneficial fungi, increased 20 to 100fold following soil fumigation. Population benefits lasted the entire season, and even extended into the next season in some settings, where significantly higher populations of Trichoderma persisted over the winter in northern tree crop soils. Additionally, the beneficial root-colonising bacteria Bacillus and Pseudomonas, which produce plant-active hormones, increased dramatically following soil fumigation. This likely explains why we see major increases in healthy root growth in crops where soils were fumigated prior to planting. And one of the most surprising findings is that no evidence was found that diversity or abundance of soil microorganisms suffered when soil samples collected 30 to 90 days after treatment were analysed.” John Washington is now working with Leicesters Soil Solutions in New Zealand, coordinating the soil biome research on melons with Moffett Orchards, and on blueberries with Gourmet Blueberries. “We are initiating these studies with these growers in mid-May and this will provide us with specific and comprehensive data on New Zealand crops, something we plan to present locally when the results are complete,” John says. For more information Phone 06 843 5330 or visit www.leicesters.co.nz
