Till in several inches of well-aged manure or compost into the berry beds before planting to boost the soil fertility. Remove all clumps and stones from the soil.
Mix in a 10-10-10 slow-release fertilizer into the top 3 to 6 inches of soil, using 2 1/2 lbs. of fertilizer for every 100 square feet of planting soil, just before planting time in the spring.
Water the fertilizer into the soil very lightly and wait two to five days before planting your berry plants in the amended and fertilized soil.
Fertilize established berry beds over the soil or mulch in middle to late April with a fertilizer with a guaranteed analysis of 10-10-10 or an organic equivalent. Follow the product label dosing directions, but do not exceed application rates of 2 1/2 lbs. for every 250 square feet of plantings or 3 lbs. for every 250 square feet if you have a heavy mulch over the soil.
Repeat a second identical application four to six weeks after the first to keep the plants in a high-production growth mode.
Water each fertilizer application in lightly to begin distributing the nutrients. Provide a minimum of 1 to 2 inches of water a week thereafter.