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Relay-Intercropping does not Reduce Strawberry Yield in a Winter Annual Hill Production System

Relay-intercropping of strawberries grown in a winter annual hill production system is a means for producers to maximize inputs of land preparation, plastic mulch, and drip-irrigation in fumigated soil.  Planting of secondary crops takes place 4-5 weeks before the end of the strawberry production season dependant on strawberry variety.  Common secondary crops are squash, muskmelons, pickles, and peppers.  Once strawberry production becomes unprofitable, plants are removed by hand to allow unimpeded growth of the secondary crop.  This practice allows for earlier harvesting of the secondary crop and enables producers to market secondary crops sooner.  The effect of relay-intercropping these secondary crops with strawberry has not been determined. 

Double-cropping is the production of two crops in the same field in a single year with the crops not growing at the same time.  Double cropping of vegetables and strawberries with muskmelons on plastic mulch has been researched and found to be a profitable management strategy for producers.  Relay-intercropping is the production of two crops in the same field in a single year with both crops in the field for some period of time with the primary crop having a competitive advantage over the secondary crop.  This competitive advantage usually comes from the primary crop being at an advanced stage of development when the secondary crop is planted.  Relay-intercropping suppresses the second crop planted in the field until the first is removed.  This allows for growth of the second crop with minimal competitive impact on the primary crop.    

Strawberry is an insurable crop.  However, insurance policies may not allow for relay-intercropping of strawberry with secondary crops.  The purpose of this study was to determine the effect of intercropping strawberry with the most common secondary crops.

A study was instituted at the Gulf Coast Research and Education Center -Dover to examine the effect of relay-intercropping squash (cv. ‘Gentry’) and pickles (cv. ‘Napoleon’) from seed, and cantaloupe (cv. ‘Athena’) and pepper (cv. ‘Wizzard’) from transplants, on yield of strawberry.  Plantings of secondary crops occurred on 28 Feb, 7 March, and 14 March, 2003 and 2004 into a 16 plant plot of ‘Strawberry Festival’ strawberries spaced 15 inches apart in row and 12 inches between rows.  Cantaloupe spacing was 30 inches in the center of the bed, squash and pickle spacing was 15 inches in the center of the bed, and pepper spacing was a double row on the bed 15 inches between plants and 10 inches between rows.  Fertilization was increased from 0.75 lbs N A/day  to 0.83 lbs N A/day, a 10% increase to compensate for additional plants in the field.  Pesticide applications were adjusted to account for label requirements for all crops and discontinued when no suitable material was available.  Data were collected twice weekly from each plot from the time of planting the secondary crop until the end of the harvest period.  Data was collected for marketable yield, number of marketable berries, and cull fruit, based on deformity, size and disease incidence, until  31 March, 2003 and 1 April, 2004 which corresponded to the end of both seasons for commercial producers.  Secondary crops were destroyed at the end of the experiment due to space and capability limitations at the site.  There were no year by treatment interactions therefore, data were combined for years and analyzed for each planting date using ANOVA procedures using SAS statistical software.

No differences were detected among treatments for yield (Fig. 1), or number of fruit or cull fruit (data not presented). This suggests that is there is no detriment to strawberry fruit yield from relay-intercropping with squash, pickles, cantaloupe, or peppers planted up to 31 days before the end of fruit harvest.  This is only true when the strawberry population of the field has been maintained and no plants removed for the planting of the second crop.  If strawberry plants are removed, a corresponding decrease in yield/acre would be expected. Anecdotal evidence suggests that ease of harvest for strawberries was not affected by any secondary crop.  Relay- intercropping does not reduce strawberry yields with test secondary crops therefore, this practice should not be considered a reason to invalidate insurance policies if performed within the last 4 weeks of strawberry production.  However, great care should be taken to apply pesticides that are labeled for both crops planted together in the field.  Furthermore, relay-intercropping is a management strategy that can increase the utility of inputs in an annual hill winter strawberry production system.

(John R. Duval, assistant professor, GCREC-Dover and Alicia Whidden, extension agent, Hillsborough County, Vegetarian 05-01)