Proper Planning

Irrigation and Fertilization Practices for the Summer Months

Southern highbush blueberries (SHB) experience a significant amount of canopy growth during the summer months following post-harvest pruning. Most of the fruiting wood for next year’s crop is produced during the summer months. Careful irrigation and fertilization management is needed to ensure that the plants have sufficient water and nutrients to support this growth. 


SHB have a shallow root system with no root hairs, which restricts water uptake capacity and increases susceptibility to drought stress. Water use by blueberry plants peaks during late summer (August and September) when plant canopies are large, temperatures are high, and day lengths are long. Proper irrigation management is especially important during this time when canopy regrowth is occurring and plant water demands are high. 

SHB in Florida are typically planted either in pine bark beds prepared on top of the soil, or in soil beds amended with pine bark. Pine bark adds organic matter to the blueberry root zone, and helps keep pH in the range of 4.5 – 5.5, which is necessary for good blueberry growth and nutrient availability. However, pine bark does not retain water very well, and the majority of SHB roots tend to stay within the pine bark layer or in the top 7 to 10 inches of soil. Over-irrigation, especially in this system, can lead to inefficient water use and leaching of nutrients below the root zone.

During periods of high water demand, daily plant water requirements may exceed the amount of water that is retained by the pine bark, or pine bark amended soil, in the plant rootzone. Therefore, during these periods of high water demand, light irrigations applied multiple times per day will increase water use efficiency and reduce potential leaching of fertilizers and pesticides, compared to irrigating less frequently for longer time periods. The frequency of irrigation will depend on weather conditions, cultivar, soil type, and the use of pine bark as a substrate or amendment. 


For young blueberry plants, the focus for fertilization is on maximizing plant growth and ensuring survival. For mature plants, the goal is to maintain a good balance between vegetative and reproductive growth, to promote optimal yield. These goals are accomplished by applying essential nutrients in advance of plant needs. One of the most important nutrients for plant growth is nitrogen (N). Recent research indicated that the highest uptake of N in young SHB blueberry plants takes place from late summer through the middle of fall during rapid canopy growth; this is likely also true for mature blueberry plants. Therefore, it is important to have sufficient N (as well as other nutrients) available during the summer and early fall months to support this growth. 

As is the case with irrigation, the effects of pine bark growing media must be considered when developing a fertilizer program. In addition to low water holding capacity, pine bark has only moderate nutrient holding capacity. This can result in leaching of fertilizer below the root zone during times of heavy rainfall or irrigation, and may require higher applications of N fertilizer. 

More frequent applications of smaller amounts of fertilizer, as opposed to larger single applications, is recommended in order to minimize leaching loss. In addition, new pine bark (either in new beds or added to supplement existing beds) can immobilize the ammonium form of N, leaving an insufficient amount available for uptake by the plants. Growers should consider applying N to new bark beds at least three months prior to planting, and increasing the amount of N applications in the months following the addition of new pine bark to an existing bed, to compensate for the N immobilized by fresh pine bark.

Leaf nutrient analysis should be performed at least once per year to determine plant nutritional status. This is typically done just prior to post-harvest hedging, but can also be performed during the first post-hedging flush (after leaves are fully expanded), or at other times during the year if symptoms of possible nutrient deficiency or toxicity appear. The primary use of this analysis is to assist in designing a fertilizer program, by determining both the current status and the sufficiency over time of essential nutrients in blueberry plantings, considering variables such as weather conditions, management practices, and yield. 

Leaf samples should be mature leaves from the current season’s growth, and should be taken separately for each cultivar. Each sample area should have a uniform soil type, the same fertilization and irrigation program, and not exceed 10 acres.

There is considerable variation in the recommended frequency and volume of fertilizer applications depending on fertilizer type, plant age, climate, soil/media type, and management practices (including irrigation and weed control). Decisions on fertilizer application should be made based on soil and leaf nutrient analysis, levels of plant growth and development, environmental conditions, and grower experience using fertilizer on their site.

CREDIT: Jeff Williamson and Doug Phillips
Share this post:

Comments on "Proper Planning"

Comments 0-5 of 0

Please login to comment