Effects of nitrogen rates on summer squash

Bielinski M. Santos, Camille E. Esmel, James P. Gilreath


Three trials were conducted to evaluate the growth and yield responses of summer squash (Cucurbita pepo L.) to N rates. Preplant fertilizer rates were 50, 100, 150, 200, 250, and 300 lb/acre of N. In Ruskin, summer squash plant vigor increased linearly with N rate. However, this constant increase in vigor did not reflect on total yield, which sharply increased between 50 and 100 lb/acre of N, remaining stable afterwards. In Balm, a linear equation characterized the effect of N rates on plant vigor. However, this response was not expressed as increased total yield, since there was no significant N rate effect. At all N rates and in both locations, petiole sap N-NO3 readings at 8 weeks after treatment (WAT) ranged from approximately 700 to 2000 ppm, which are within sufficiency levels for the crop. These results indicated that between 50 and 100 lb/acre of N could be sufficient to maximize summer squash production, depending on potential amounts of N in the soil from previous growing seasons. In this particular case, the estimated N release (ENR) potential of Ruskin soils, which was determined through wet-ashing of the organic matter, was only 25 lb/acre, whereas the ENR in the two Balm sites were 45 and 75 lb/acre of N. It is suggested, as an appropriate nutrient management practice, perform soil analysis prior to planting summer squash as a double crop to estimate residual N amounts and consequently adjusting N application rates.


Cucurbita pepo; cucurbits; soil nutrients; nutrient requirements

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283