Soil health as it relates to yield – a Tier Two update (St. Clair Region)

Submitted by: Anne Verhallen, Soil Management Specialist Horticulture – OMAFRA

The purpose of this project is to compare A&L Canada Laboratories’ new soil health analysis to yield and plant performance. Each year of the project, up to 7 co-operators from each county (Lambton, Kent and Essex) will provide corn fields to be sampled. One stressed area and one healthy area is sampled in each field.

Corn root ball

Root ball samples ready for tags and bagging. Each location is assigned a number. “good” and “bad” sites are randomly assigned an “A” or “B” code

2020 marks the third and final year for this project. Each year has posed some challenges as we learned the site selection and sampling methods, worked around late planting and now in 2020, a cold spring with replants, market stresses and COVID-19. The project looks at the connections between soil health measurements, the functions of the soil microbiome and yield. This year the number of sample fields was capped at 14 due to a combination of sampling constraints and previous cooperators with limited suitable corn acreage. The sample sites are spread across the St Clair Region from Harrow to the north end of Lambton county.

Once the fields were identified, cooperators were asked   to provide background information. In particular, we looked for historical yield maps, fertility maps and even personal insight into performance and underlying factors. Soil and topographic maps  were  consulted. Which was a refinement from the first year’s sampling. Cory Cowan and Agris staff provided Taranis NDVI imagery. Project sampling involved collecting samples from “good “ and “bad” locations; bad being where the crop was stressed and didn’t consistently yield as well. In particular, we looked for locations where crop growth and yield were different over time but there was no obvious reason why. Cloudy conditions through the middle of July did pose a challenge for obtaining a good series of NDVI imagery for some sites.

The 14 fields were sampled through July and early August. In each “good’ and “bad” area 5 corn plants were harvested, growth stage and weed control were recorded and the root balls individually packaged for lab analysis. A separate composite sample was collected at each site for aggregate stability testing and the depth of the A horizon or the topsoil depth was also recorded. Even with the revisions to the site selection approach, underlying soil profile differences still seemed to help explain some of the crop response. Often it seemed the difference of an inch or two of topsoil made a significant difference in crop response, particularly under the hot and dry conditions of mid July 2020.

The root balls were delivered to A & L Canada in London; where the soil in each root ball was sampled using the Vitellus soil health method. Vitellus includes soil fertility measurements, Solvita and a number of other soil health measures. This year, due to a lack of student labour and lab access, as a resut of COVID-19, the aggregate stability samples will be sent to SGS Labs for analysis. They provide a physical or soil structural measurement as part of the soil health assessment.

At harvest, hand and combine yields will be collected and analysed in combination with the data collected in the summer. Dr. Laura Van Eerd and Inderjot Chalal will be assisting with this. Previous years data has not suggested strong connections with many of the soil tests and crop yields, but refining the site selection may help with this.

Each site was signed near the road. The entrances are also marked with flags and flagging tape to supplement GPS records and ensure harvest samples are taken at the correct locations.

Weed control is recorded for each site. In this case the poor grass control was found at both the “good” and “bad” sites. Weed control was not the cause of differences seen in the NDVI map. There did appear to be a slight change in soil texture and topsoil depth. 

Soil Probe

The depth of the A horizon was checked with a soil probe at each sampling site. Dry soil conditions at some did make this difficult. Often there was a small difference in topsoil depth.

Thank you to the on-farm cooperators, A & L Labs, Agris Cooperative and the University of Guelph.

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