Ontario, Wisconsin compared | Vegetable crops affected most by number of days with rain and mean temperature
LINDELL BEACH, B.C. — Ontario and Wisconsin share a long-term climate, but the weather might be dramatically different from year to year.
Researchers from the University of Guelph wanted to know how close the association is between the two regions, which could help find causes to common problems shared by many regions around the world.
To find out, they examined crop yield data of 11 horticultural crops and one field crop over a 55-year period in Wisconsin.
The researchers obtained production yield data from the U.S. Department of Agriculture’s National Agricultural Statistics Service for beets, cabbage, carrots, cucumber, green peas, onions, potatoes, snap bean, sweet corn and grain corn.
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“This study showed the impact of weather on vegetable crop yield and the use of long-term weather parameters in determining how weather affects crop yield,” U of G researcher Michael Tesfaendrias said in a reply to emailed questions. His findings were published in the journal HortScience with colleagues Mary Ruth McDonald and Jon Warland.
“The study also showed that there were a number of similarities between weather parameters of Wisconsin and southern Ontario. While rainfall and temperature were somewhat related, the greatest similarities between the two regions were growing season temperatures and the number of hot days. However, the results demonstrated that they were different enough to be reasonably independent samples. This could be due to local practices or other non-weather factors.”
The goal was to test the findings from their work in Ontario to see if they were applicable to other growing areas or only specific to the province.
“Of course, we expected them to be applicable to other areas, but we needed a good test,” he said.
They focused the study on the region where most of the vegetable crops are grown in Ontario and Wisconsin. As was expected, they found many similarities, and the strongest relationships were during those periods measured by the number of rainfall days and mean seasonal temperatures.
“The most important point is that the response of the crops is the same, even if the weather patterns in any one year are different,” said Tesfaendrias.
“That means that we are even more confident that the way the crops respond, especially the reduction in yield with high temperatures, is a common occurrence, not just something that happens in Ontario. Thus, growers of these same types of vegetable crops could expect the same responses, whether they are in North America, Europe or some other part of the world where similar crops and cultivars are grown.”
For rainfall, the number of days was more important than total rainfall amount, and the number of days with hot temperatures, especially during July and August, was the most important weather trigger to measure estimated yields.
Tesfaendrias said individual vegetable crops respond differently to varying weather conditions.
Crops grown in Wisconsin that showed reduced yield with increasing high temperatures were beets, green peas, onions and sweet corn for processing. Other associations were found when the data for each month of the growing season was examined, including the effects of high temperatures on yields of cabbage, cucumbers, grain corn, onions, snap beans and sweet corn.
The study showed that there have changes in weather over the 55 year period with a fluctuating pattern.
“In general, there was a period with several years of hot summer weather in the late 1940s and the 1950s, followed by a relatively cool period in the ’60s, ’70s and ’80s and then more variable weather with more years with hot summers after that.”
It was the 30 year period from 1960-90 that triggered the study because cabbage yields were higher in the 1980s than the 1990s.
“The yield response to various weather parameters was different.
“For instance, the number of hot days in a growing season was negatively correlated with yields of most vegetable crops evaluated in this study. A high number of days with precipitation in May and July were associated with higher yields of most vegetables and grain corn in Wisconsin. These results indicated the importance of the total and frequency of seasonal precipitation and the negative effect of exposure of crops to extreme temperatures on yields of vegetable crops.”
Tesfaendrias said high temperatures can be the most difficult weather factor to modify.
“For the crops that need irrigation, growers may irrigate more often during hot days to prevent heat stress, but this works best with overhead irrigation,” he said.
“Keeping crops cool is quite difficult. For some high value crops, reflective mulches or living mulches may keep the soil a bit cooler.”
The research shows that it is becoming increasingly important to breed vegetable crops that can tolerate heat and conserve water to cope with a warming climate.
