I planted an apple sapling of the Antonovka variety in the spring in open ground. I'm not entirely sure how often to water it during the summer so it takes root and the root system doesn't rot. I live in the central part of the country, and summers are usually dry here.
An important clarification: watering frequency depends less on the calendar and more on how quickly the soil dries out after the previous watering. Water when the top layer of soil in the root zone (about 5-7 centimeters) feels dry to the touch - this might be once a week, or more often if the summer is hot and windy. Here's a pitfall people often miss: right after planting, people tend to overwater the seedling out of sympathy, and then they're surprised when the root collar rots. Make sure the water soaks into the soil rather than pooling up - if you see standing water, that means you've already overdone it.
In its first year, a young apple tree needs regular moisture, but don't go overboard. The main principle is that the soil should be moist, but not waterlogged. In summer in the middle zone during dry weather, water generously once a week (5-10 liters per sapling) to soak the soil to the depth of the roots. If it rains, count that as your watering and skip your own. The key thing is don't water after every day without rain - that's a guaranteed path to root rot.
Go by the soil's condition: check with a stick or just your hand at a depth of 10-15 cm. If the soil is dry, it's time to water. In the first month after planting, you can water more often (every 3-4 days), then switch to a weekly schedule. Toward the end of summer, reduce watering - this will help the plant prepare for the cold. After each watering, lightly loosen the soil around the tree so a crust doesn't form.
Mulching is a lifesaver: if you put a layer of grass or wood chips around the sapling (but not right against the trunk), moisture will stay longer, and you'll have to water less often. In your conditions that will help a lot.
Guys, I'll add something about mulching - if you mulch the tree circle after planting with a 5 - 7 centimeter layer (sawdust, straw, cut grass), the soil moisture lasts much longer, and you won't need to water as often. In a dry summer it's a lifesaver, especially if you forget to water on time.
Antonovka is quite drought-tolerant, but in the first year, while the roots haven't gone deep yet, that doesn't help - a young seedling really does need regular watering. The main thing I'll point out: check the moisture at a depth of 20-30 centimeters, not just on the surface, because the top layer dries out quickly while there might be excess moisture below. If summer in the middle belt is dry, then watering once a week makes sense, but after rain don't rush - skip the watering, otherwise instead of helping you'll end up with root rot.
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