Impacts of a cool spring on cover crops and vegetable crops management

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

At this time in 2006, we were all concerned about the effects of a warm spring on crop production. Then in 2007, we had a more “normal” spring in many regions. This year we have been experiencing a rather cool spring. Temperatures across the state have remained significantly below normal values and that is likely going to have important effects on the entire growing season.

Impact on spring-planted cover crops

Spring cover crops (mainly cool season species like mustards) are generally planted the first half of April, in preparation for June planting of vegetable crops. With the cool weather, growth of those cover crops has been extremely slow and biomass production at this moment is generally less than 50 percent of the expected values. In some cases, the cool temperatures have triggered flowering in some species like yellow mustard at a very young stage when the plant was only four to six inches tall with two to four leaves. Overall, the small biomass produced will reduce the benefits of the cover crops.

Impact on bolting

Bolting is a physiological disorder that results in a premature formation of the seed stack (flowering) in many vegetable crops. The problem is caused by exposure to cool temperatures like those that we have been experiencing over the last two weeks. Different varieties have different levels of bolting susceptibility. Celery and crucifers (Chinese cabbage, cabbage, broccoli, etc.) are some of the crops that growers should watch for this problem.

Impact on earliness

The expression “The early bird catches the worm” is well known by most vegetable growers. Earliness usually involves planting the crop earlier than the rest of the industry. However, under cool weather the efforts of the early bird might not always pay off because the seed does not germinate when the soil is cool, and seedlings stop growing under cool weather. This is probably a year when growers who invested in season extension strategies (low tunnel, row cover, plastic mulch, etc.) may benefit significantly from their investments.

Impact on harvest schedule

Sequential planting is a technique used by many growers (celery, sweet corn etc.) to spread harvests over a long period, therefore providing consumers with fresh, high quality, locally grown produce. Cool weather can delay germination and slow down plant growth. As a result, maturity can be concentrated at a specific time during the season despite a careful planning and staggered planting by the growers. Although it is too early to predict harvest concentrations, this is the time for growers to start developing strategies in the event that unpredicted peaks in maturity occur.

Dr. Ngouajio's work is funded in part by MSU's AgBioResearch.

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