Growing Berries in Your Backyard
Watering. Raspberries require 1 to 2 inches of water per week from mid-May June through September, and about half that amount when the weather is cooler in early spring and fall. It is important to keep the soil moist at all times without saturating the soil and causing the roots to rot. Hot and windy weather conditions increase the water requirements. If raspberries are fruiting during warm weather, daily irrigation may be required. In general, apply water twice per week. Overhead irrigation promotes fruit rot and leaf rust diseases, so is not recommended for raspberries. The best irrigation systems are drip lines that have numerous emitters (spaced every 6 to 12 inches) that wet an entire band of soil underneath the foliage. With drip irrigation, raspberries should be watered daily for 1 to 2 hours, especially during fruiting or hot weather. Avoid wetting the foliage with mini-sprinklers.
Fertilizing. Apply inorganic fertilizers in early spring when new growth starts at a rate of 4 to 6 pounds of 20-20-20 or ammonium sulfate (21-0-0) per 100 feet of row. Fall-bearing raspberries require an additional fertilizer application before fruiting. When new canes start to bloom, spread 1 to 2 pounds of ammonium nitrate or 1.5 to 3 pounds of ammonium sulfate, or 3 to 6 pounds of blood meal, fish meal, or feather meal per 100 feet of row. Inorganic fertilizers should be spread over the surface of the soil in the row in early spring just when growth is starting. If you use manure or compost, apply it in the late fall or early winter to allow leaching of excess salts by rain.