31 January 2024

Crop yield history reveals details of soil health

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A study by the University of Michigan reveals the link between agricultural yield and soil quality. Using a new metric, key information can be obtained to plan agricultural strategies while reducing environmental impact

by Matteo Cavallito

 

Historical yield analysis can provide vital information about soil health and carbon sequestration. This is supported by research from Michigan State University published in the journal Scientific Reports. “Agriculture is facing major challenges around feeding a growing world population, climate change and environmental damage such as soil erosion and water pollution,” said Bruno Basso, professor and co-author of the study in a statement. “Boosting soil health can play a major role in combatting these issues.”

Historical data replace soil tests

Behind the study was the hypothesis that regions characterized by high yields have higher quality soil. The link, the authors explain, may seem obvious. But the high variability within fields makes data collection and related strategic assessments for reducing environmental impact (through limiting fertilizer use, for example) and maximizing yields complex. In addition, such surveys can be very expensive primarily because they require a large number of soil tests to properly capture yield variability.

Alternatively, research has verified the usefulness of a new analysis metric known as yield stability zones.

By analyzing not only yield level but also its constancy over time, the authors explain, it is possible to offer a broader understanding of the phenomenon by also considering its small-scale and field variability. The survey covered ten corn and soybean fields in Michigan, Illinois and Indiana, in the agricultural region of the American Midwest. The data used showed agricultural profitability over a period ranging from 11 to 18 years.

The study

“Using known relationships between soil health and crop yields, we hypothesize that areas with measured constantly low yield will return low carbon to the soil affecting its health,” the research explains. “On this premises, yield stability zones (YSZ) provide an effective and practical integrative measure of the small-scale variability of soil health on a field relative basis.”

The researchers found that these zones effectively highlight differences between field areas based on statistically distinct factors such as stored carbon and soil health.

“We tested this hypothesis by measuring various metrics of soil health from commercial farmers’ fields in the north central Midwest of the USA in samples replicated across YSZ, using a soil test suite commonly used by producers and stakeholders active in agricultural carbon credits markets,” the study continues. “We found that the use of YSZ allowed us to successfully partition field-relative soil organic carbon (SOC) and soil health metrics into statistically distinct regions.”

Identifying a link between yields and soil quality

For example, “we saw that low-stability zones have shallower or more compacted soils, higher bulk densities and are located on steeper slopes,” explains Basso. “Unstable zones had higher soil organic carbon levels associated with flow accumulation and topsoil accumulation from erosion processes.”

These findings, the research explains, “suggest that YSZ can identify the feedback relationships between soil formation, SOC accumulation, soil health, and yield potential, particularly in terms of increased water and nutrient holding capacity.” In addition, “yield stability maps provide valuable insights into soil health based on the long-term, topographic, and biological drivers of soil formation which are then reflected in spatial and temporal variation of crop yield and SOC accumulation.”