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  • Author or Editor: Rao S. Mylavarapu x
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Qiang Zhu, Monica Ozores-Hampton, Yuncong Li, Kelly Morgan, Guodong Liu and Rao S. Mylavarapu

Phosphorous (P) has a significant role in root growth, fruit and seed development, and plant disease resistance. Currently, no P fertilizer recommendations are available for vegetables grown on calcareous soils in Florida. The objective of this study was to evaluate the impact of different P rates on leaf tissue P concentration (LTPC), plant growth, biomass accumulation, fruit yield, and postharvest quality of tomato (Solanum lycopersicum L.) grown on a calcareous soil. The experiment was conducted with soils containing 13 to 15 mg·kg−1 of P extracted by ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA). Phosphorus fertilizers were applied at rates of 0, 29, 49, 78, 98, and 118 kg·ha−1 of P before laying polyethylene mulch. Tomatoes were grown using drip irrigation during the winter seasons of 2014 and 2015. No significant responses to P rates were found in LTPC during both growing seasons. Plant height, stem diameter, and leaf chlorophyll content at 30 days after transplanting (DAT) were significantly affected by P rates in 2015, but not in 2014. The responses of plant biomass were predicted by linear models at 60 DAT in 2014 and at 30 DAT in 2015. There were no significant differences in plant biomass at 95 DAT in both years. At the first and second combined harvest, the extralarge fruit yield was unaffected in 2014, but predicted by a quadratic-plateau model with a critical rate of 75 kg·ha−1 in 2015. The total season marketable yields (TSMY) and postharvest qualities were not significantly affected by P rates in either year. Phosphorous rate of 75 kg·ha−1 was sufficient to grow a tomato crop during the winter season in calcareous soils with 13–15 mg·kg−1 of AB-DTPA-extractable P.

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Qiang Zhu, Monica Ozores-Hampton, Yuncong Li, Kelly Morgan, Guodong Liu and Rao S. Mylavarapu

Florida produces the most vegetables in the United States during the winter season with favorable weather conditions. However, vegetables grown on calcareous soils in Florida have no potassium (K) fertilizer recommendation. The objective of this study was to evaluate the effects of K rates on leaf tissue K concentration (LTKC), plant biomass, fruit yield, and postharvest quality of tomatoes (Solanum lycopersicum L.) grown on a calcareous soil. The experiment was conducted during the winter seasons of 2014 and 2015 in Homestead, FL. Potassium fertilizers were applied at rates of 0, 56, 93, 149, 186, and 223 kg·ha−1 of K and divided into preplant dry fertilizer and fertigation during the season. No deficiency of LTKC was found at 30 days after transplanting (DAT) in both years. Potassium rates lower than 149 kg·ha−1 resulted in deficient LTKC at 95 DAT in 2014. No significant responses to K rates were observed in plant (leaf, stem, and root combined) dry weight biomass at all the sampling dates in both years. However, at 95 DAT, fruit dry weight biomass increased with increasing K rates to 130 and 147 kg·ha−1, reaching a plateau thereafter indicated by the linear-plateau models in 2014 and 2015, respectively. Predicted from quadratic and linear-plateau models, K rates of 173 and 178 kg·ha−1 were considered as the optimum rates for total season marketable yields in 2014 and 2015, respectively. Postharvest qualities, including fruit firmness, pH, and total soluble solids (TSS) content, were not significantly affected by K rates in both years. Overall, K rate of 178 kg·ha−1 was sufficient to grow tomato during the winter season in calcareous soils with 78 to 82 mg·kg−1 of ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA)-extracted K in Florida.