Authors: Natalie Hoidal & Marissa Schuh
This is one of the busiest weeks of the summer and it’s hard to take breaks or slow down, but working in this heat and smoke is dangerous, both for your immediate and long term health. Take good care of yourselves and your people.
We realize we’ve talked about heat a lot in this newsletter this summer, but that’s the reality we’re living with. We also realize telling farmers not to work is unrealistic, as there’s so much that needs to happen on the farm this time of year. So, let’s quickly break down the heat safety guidelines for the conditions we’re experiencing right now. Keep in mind that the following guidelines are for healthy people without underlying conditions. If you have asthma, diabetes, or other conditions that make you sensitive to heat, follow even more stringent precautions.
August and even September bring opportunities to plant greens for late fall and even winter harvest. We’re really excited about an upcoming field day at 10th Street Farm in Afton. They do a really good job of thoughtful succession planting to ensure continued harvests throughout the fall and early winter. Consider making the trip to learn about their succession planning for fall harvests, moveable high tunnels, and soil health practices. More details about the field day here.
Carrots: As carrot harvest picks up, we always receive a few questions from folks with very misshapen carrots. There are a few causes, and it's important to figure out which one (or ones) is causing deformations so you can make changes next year.
Potatoes: Your potatoes are probably the last thing on your mind right now, but believe it or not, now is one of the most critical management windows for potato crops. As flowering slows down, potatoes begin to shift their energy into tuber production. This is the time where very consistent watering pays off. Inconsistent moisture during tuber formation leads to two major problems: hollow heart and scab. So, while your other crops need water too, now is a good time to focus on keeping your potatoes watered as consistently as possible.
Tomatoes: This is the time of year when we start to see yellow shoulder, a physiological disorder that is more likely to occur in hot, humid conditions, and also in situations where plants don't have enough potassium, or where they have too much nitrogen. It is also more common in compact or waterlogged soils. If you're seeing yellow shoulder, take note and make sure to re-assess your nutrient management program and / or irrigation program next year. In the meantime, foliar applied potassium may help fruit that is just beginning to develop.
Vine crops: Heat can cause flowering and pollination issues in a variety of crops, but cucurbits are particularly sensitive. There's not actually a distinct temperature at which pollination stops or at which flowers or fruit abort; rather, hotter temperatures cause the plants to shift their balance of male and female flowers. Some varieties simply stop producing female flowers when it gets too hot. Usually there's more of a gradual shift and imbalance vs. completely stopping female flower production. Typically we can expect to see problems when temperatures reach 90 degrees during the day, and stay above 70 degrees at night. High light levels help to mitigate this a little bit, and so adequate spacing and pruning can help to prevent fruit and flower abortion. It’s also possible for pollination to be incomplete and rather than completely losing the fruit, you’ll see misshapen fruit. There is potential for a drop if harvest frequency and yield until the next set of flowers post-heat form and get pollinated.
This is one of the busiest weeks of the summer and it’s hard to take breaks or slow down, but working in this heat and smoke is dangerous, both for your immediate and long term health. Take good care of yourselves and your people.
What does it mean to work safely in this heat (and now smoke)?
Farm workers are among the most at risk people for heat related deaths, and the numbers are likely under reported. The risks are exacerbated by smoke.We realize we’ve talked about heat a lot in this newsletter this summer, but that’s the reality we’re living with. We also realize telling farmers not to work is unrealistic, as there’s so much that needs to happen on the farm this time of year. So, let’s quickly break down the heat safety guidelines for the conditions we’re experiencing right now. Keep in mind that the following guidelines are for healthy people without underlying conditions. If you have asthma, diabetes, or other conditions that make you sensitive to heat, follow even more stringent precautions.
- We’re starting with smoke because in the last week, we’ve gone from a summer with pretty good air quality to some of the worst air quality Minnesota has ever seen. Large swaths of the state have surpassed 400 AQI; anything above 150 is considered unhealthy for everyone, and people are advised to stay indoors. If you have to be outside for any amount of time, wear a respirator (we know it’s hot and uncomfortable, but air quality this bad is nothing to mess with). Making sure you have clean air to breathe while you’re not working is important too - if you have central air, check your filters and make sure they are clean. If you don’t, invest in an air filter or build your own. We run a DIY Corsi-Rosenthal air filter in our house, and it’s very effective at improving indoor air quality.
- The good news is that air quality is not universally bad, and is expected to fluctuate throughout the week, meaning there should be pockets of time when you can be outside safely. Keep a close eye on your local monitoring systems, and consider an air quality monitor at your farm to help you make informed decisions hour by hour.
- Temperatures in southern MN are hovering around 92 degrees F in the afternoons, with a real feel temperature closer to 96. That puts us squarely in the “Extreme risk” category. At these temperatures, your body requires around 1 litre of water (1 quart) per hour, and you should be drinking electrolytes. Doing moderate work (picking veggies, walking around), you should be working only 20 minutes per hour and resting in a cool area in between work. For heavy work (shoveling, hoeing, loading), you should only be working for 10 minutes per hour.
- In the mornings, we’re still reaching moderate risk conditions, where only 30-40 minutes of work per hour is recommended, with 20-30 minutes of rest in a cool place in between work intervals.
- Know the signs of heat exhaustion and stroke. *Heat exhaustion and stress can give you brain fog, and make you less likely to recognize the symptoms you’re experiencing. Keep a close eye on your coworkers (and yourselves).
- Heat exhaustion: heavy sweating, cold clammy skin, fast, weak pulse, nausea, muscle cramps, dizziness, or headaches. Get to a cool place immediately, loosen your clothes, put cool, wet cloths on your body, and drink water. If your symptoms persist more than an hour or get worse, seek medical attention immediately.
- Heat stroke: high body temperatures (103 F), hot or red skin, a fast, strong pulse, a headache, dizziness, nausea, confusion, and passing out. If someone is experiencing these symptoms call 911 immediately and try to cool their body, but do not provide liquids until emergency responders arrive.
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| A smoky sunrise in Northern MN this morning. Photo: Troy Salzer |
Transitioning to fall crops
We are reaching the final few successions of summer planted crops for fall harvest.You likely have had a few things not work out quite as planned, and you may have some gaps in your fields where crops ended more quickly than anticipated. If so, what can you still plant for fall harvest? In general, the next 10 days or so are a great time to plant carrots, beets, broccoli and other brassicas, chard, green beans, peas, and herbs for fall harvest. Check out our crop planning tools to help you figure out what you can still plant, what yields you can expect, and variety recommendations. Full disclosure: the web version of these tools is not very pretty or user friendly. You can email Natalie (hoida016@umn.edu) for the spreadsheets in their intended format.August and even September bring opportunities to plant greens for late fall and even winter harvest. We’re really excited about an upcoming field day at 10th Street Farm in Afton. They do a really good job of thoughtful succession planting to ensure continued harvests throughout the fall and early winter. Consider making the trip to learn about their succession planning for fall harvests, moveable high tunnels, and soil health practices. More details about the field day here.
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| Photo: October greens at 10th Street Farm, photo by Ellen Badger Hanson |
Crop updates
Basil & cut flowers: Japanese beetle damage is starting in earnest. Drought in the previous year can really put a damper on their populations. Physical removal in the morning when the beetles are moving slowly could work in small planting.Carrots: As carrot harvest picks up, we always receive a few questions from folks with very misshapen carrots. There are a few causes, and it's important to figure out which one (or ones) is causing deformations so you can make changes next year.
- If your soil is very rocky or compact, carrots can fork - growing on raised beds can reduce compaction and provide better drainage.
- Too much nitrogen can cause carrots to branch. If you're seeing a lot of branching and your soil isn't especially compact or rocky, think back to the amount of nitrogen you applied (this is especially relevant for faster release sources). Carrots need about 120 lbs N on low organic matter soil, 100 lbs on medium organic matter soil, and 80 lbs on high organic matter soil.
- Pythium is a soil borne disease that can cause excessive branching and stubbiness. This is typically an issue in fields without good drainage that receive excess water: while most of Minnesota is dry, some areas have received excessive rainfall. Pythium is often accompanied by cavity spot symptoms.
- Root knot nematode also causes branching, but it's typically accompanied by nubs all over the roots, and often excessive hairiness. Hairiness is also a symptom of aster yellows, but carrots with aster yellows should not have distinct nubs.
Potatoes: Your potatoes are probably the last thing on your mind right now, but believe it or not, now is one of the most critical management windows for potato crops. As flowering slows down, potatoes begin to shift their energy into tuber production. This is the time where very consistent watering pays off. Inconsistent moisture during tuber formation leads to two major problems: hollow heart and scab. So, while your other crops need water too, now is a good time to focus on keeping your potatoes watered as consistently as possible.
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| Hollow heart in potato, Ben Phillips, Michigan State University, Bugwood.org |
Tomatoes: This is the time of year when we start to see yellow shoulder, a physiological disorder that is more likely to occur in hot, humid conditions, and also in situations where plants don't have enough potassium, or where they have too much nitrogen. It is also more common in compact or waterlogged soils. If you're seeing yellow shoulder, take note and make sure to re-assess your nutrient management program and / or irrigation program next year. In the meantime, foliar applied potassium may help fruit that is just beginning to develop.
Vine crops: Heat can cause flowering and pollination issues in a variety of crops, but cucurbits are particularly sensitive. There's not actually a distinct temperature at which pollination stops or at which flowers or fruit abort; rather, hotter temperatures cause the plants to shift their balance of male and female flowers. Some varieties simply stop producing female flowers when it gets too hot. Usually there's more of a gradual shift and imbalance vs. completely stopping female flower production. Typically we can expect to see problems when temperatures reach 90 degrees during the day, and stay above 70 degrees at night. High light levels help to mitigate this a little bit, and so adequate spacing and pruning can help to prevent fruit and flower abortion. It’s also possible for pollination to be incomplete and rather than completely losing the fruit, you’ll see misshapen fruit. There is potential for a drop if harvest frequency and yield until the next set of flowers post-heat form and get pollinated.
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