Soil pH. Optimal strawberry production requires a favorable root environment and the availability of essential nutrients. Soil pH is a key factor in maintaining a favorable root environment. Soils with a pH between 6.0 to 6.2 promote the best growth. A soil test can indicate what amendments need to be added to correct the pH. Soil testing services are available from NCDA&CS regional agronomists.
Low pH is one of the most frequent problems identified on soil samples. Because the problem cannot be corrected after planting and low calcium (Ca) usually accompanies a low soil pH, testing and liming the soil as needed is especially important. Incorporate the lime based on the soil test recommendation at least two months before transplanting.
Soil moisture. Strawberry plants require a continuous supply of water during periods of active growth, and drip irrigation is the most efficient method for slowly applying small amounts of water directly to the strawberry plant’ s root zone in the pre-bloom, bloom and harvest period. It is important for growers to keep in mind that a standard 8- to 10-inch strawberry plasticulture bed has very poor capillary water movement and a drip irrigation system is going to be required to meet most of the moisture requirements of the crop. But, with good management of a drip irrigation system, strawberry root zone moisture content can be maintained close to optimum for plant growth, or near what is called “field capacity.”
In North Carolina, it is common practice to use the drip system to establish plug transplants in the late summer, but some overhead sprinkler irrigation should still be applied for the first two to three days after transplanting. It is also recommended that growers hook up their drip systems soon after planting for a post-plant chemical injection of Ridomil Gold if transplants are suspected to be infected with crown rot (Phytophthora cactorumi), or when a field has a history of this disease. To aid transplant establishment in October and November, it may be necessary to run the drip system for a few hours every few days during weeks of little or no rainfall. Drip systems are “winterized” in the late fall and are not re-connected until early March (around the time of new leaf development). Water loss from plants is much less during the dormant season (December to early February), and winter rains generally furnish adequate soil moisture through early March. However, in warm periods during mid-March (pre-bloom) it is not unusual for the crop’s water requirement to approach 1 inch/acre/week. On a daily basis this is about 3,880 gallons (1 acre-inch of water = 27,154 gallons). During the bloom, fruit set and harvest period, crop water usage will climb to 1.5 inches/acre/week (0.2 inches/acre/day), and in warm/hot weather it becomes necessary to apply as much as 1.75 inches/acre/week (0.25 inch/acre/day).
Soil erosion and surface water management. Although raised beds encourage water drainage within the soil, plasticulture growers frequently encounter problems with getting rid of excess surface water. Because 50 percent of a plasticulture strawberry field is covered with an impermeable plastic film, the field should have enough slope that surface water drains uniformly and gently from the field after periods of heavy precipitation without causing erosion or leaving puddles. On fields with more than a two percent slope (a two-foot drop over 100 feet), continuous overhead sprinkling for establishment of fresh dug plants may cause severe soil erosion. It is often a good idea to broadcast annual ryegrass at a rate of approximately 50 pounds per acre over the entire field the same day you finish fumigating (before planting holes are punched). Ryegrass will reduce soil washing in the aisles after heavy rains or establishment irrigation on sloping terrain. The ryegrass should be killed or stunted by an application of post-emergence grass herbicide when it is about six inches tall or prior to applying the winter row cover.