Nutrient Management Research Database

http://ucanr.edu/sites/Nutrient_Management_Solutions/files/212720.pdf

Optimizing nitrogen (N) management in organic strawberries on the central coastal California is a challenge because of high N sensitivity and the long growth period of strawberries, transplanting immediately followed by the winter rainy season and unpredictability of N mineralization from organic fertilizers and soil organic matter. Moreover, research-based information on N fertility management in organic strawberries is lacking. In a replicated on-farm organic rotation trial in Moss Landing, California, N dynamics in an organic strawberry production system was monitored for two years. In the first year, we examined the grower’s current N-management practice, and an improved N-management practice was demonstrated in the second year. Fertility management practices, soil inorganic N content (0-60cm deep), and fruit yield, plant biomass, and N content of strawberries (cv. Aromas) were monitored. Changes in cumulative daily N uptake of strawberries were calculated and N- loss from the root zone (0-30cm deep in the bed area) during the winter rainy season was estimated. We used a Monte Carlo simulation method to express statistical variability of the results. In the winter rainy season of the first year, we observed 214 kg-N ha-1 of inorganic N –loss from the root zone within 20 weeks after planting. Plastic mulch was applied 7 weeks after the planting. Marketable fruit yield was 38.7 tons ha-1 with a total N application rate of 255 kg ha-1. Total N uptake of strawberries was ~120 kg ha-1 and about 80% of this occurred in the later half of the growth period. In the second year, we adopted pre-plant plastic mulch application and adjusted basal/supplemental organic fertilizer-N rates to better synchronize the N supply with the plant N demand. As a result, although the residual soil inorganic-N was much lower than the first year, the N-loss during the rainy season was decreased to 13 kg-N ha-1, while maintaining fruit yield a similar to the first year.

An organic vegetable/strawberry rotation was implemented starting in 2001 on a grower's ranch in Monterey County, California.  255 kg-N ha^-1 was applied from organic sources in year 1 and 328 kg-N ha^-1 was applied in year 2.

Soil sampling for inorganic soil N was done once per month from soils 0-60 cm and N loss was estimated by final soil N content and N content in the plants from initial soil inorganic N content and N applied in organic fertilizer.  any N-loss was assumed to be in the form of leached-N and denitrified-N.  

Fruit yield was also measured 1-2 times per week from designated harvest plants in the middle two beds.

Highlights of the results include:

• After the first growing season 214 kg-N ha^-1 was estimated to have been lost since planting.
• Cumulative N uptake of strawberry plants showed that approximately 80% of N uptake took place in the second half of the growing period.  
• The grower modified his fertility management during the second year, adding a pre-planting plastic mulch and the amount of N-loss during the rainy season was reduced to 13 kg -N ha^-1.
• It should be noted that residual soil N was much lower at the time of planting during the second year and precipitation also decreased by 15%.  

nitrogen, plastic mulch, strawberry, fertilization (organic)