Laura L. Van Eerd and Steven Loewen, Ridgetown Campus, University of Guelph
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We know the value of a good soil and a healthy root system. This was evident in the summer of 2009, when processing tomato growers in southwestern Ontario noticed unusual crop symptoms, which resulted in an estimated 30% or higher yield loss in some fields. This came to be known as ‘vine decline complex’ and appeared to be due to mix of several root diseases. This makes management challenging because conditions that suppress one fungus may amplify others. While plant breeder Steven Loewen worked on developing resistant varieties, Prof. Laura Van Eerd decided to take an alternative strategy. Her approach was to focus on the soil and test a variety of soil amendments. The hope was that these treatments might promote healthier bacterial and fungal populations in the tomato root zone thereby tipping the balance to healthy plant roots and good tomato yields.
Field trials were conducted in commercial processing tomato growers’ fields from 2011 to 2013, in a total of 4 locations.
Fields with a high incidence of vine decline complex were selected. Soil amendments were applied in the spring and incorporated into the soil, with tomatoes being transplanted two to three weeks later. Growers followed their typical management production practices for fertility and pest management.
In all growing seasons and locations, soil amendments of poultry manure, mushroom compost, thermophilic compost, and MPT MustGRO® mustard seed meal gave equal or higher yields of processing tomatoes than the unamended control. In all years, poultry manure had greener, lusher plants and delayed maturity, likely due to the extra nutrients provided by the manure. Based on plant growth and soil testing, researchers do not believe that the yield increases with soil amendments were strictly due to nutrients.
Work is underway to gain a better understanding of the microbial community in and around tomato roots. Researchers at Ridgetown Campus and A&L Canada Laboratories in London, Ontario, are continuing to work together to learn more about the vine decline complex and how to manage it. The positive results from these trials are providing optimism for future breakthroughs.
So, why did the soil amendments improve tomato yields? Perhaps, the carbon in the amendments provided food for the microbes and good soil conditions for growth and a healthy root system, which lead to good crop yields. It is speculated that the soil amendments changed the type of microbes around the root to the advantage of tomato yield. Thus, practices such as soil amendments that appear to improve soil and root health provided an advantage to crop yields.
Researchers are grateful for the valuable assistance from growers and ConAgra Foods Canada Inc. in Dresden; project funding by Ontario Tomato Research Institute and the Ontario Ministry of Agriculture and Food and Ministry of Rural Affairs.