2018 ASHS Annual Conference

Florida usually ranks first in the fresh-market tomato (Solanum lycopersicum L.) production in the United States. However, there are limited studies on phosphorus (P) accumulation and distribution in tomato as affected by P rates in calcareous soils. Thus, the objective of this study was to determine the effects of P rates on P uptake and partitioning, soil P budget, and P use efficiency in tomato production in a calcareous soil. A field trial was conducted during the winter season of 2015 in Homestead, FL. Treatments included six P rates: 0, 29, 49, 78, 98, and 118 kg ha^-1, and they were arranged in a randomized complete block design with four replications. Dry P fertilizers were used and banded in the bed prior to transplanting. The stems, leaves, roots, and fruits from one plant per plot were collected 95 days after transplanting (DAT) and measured plant dry biomass, P concentration, and P uptake. Soil samples were collected 82 DAT and analyzed for Mehlich-3 extractable P. Leachate were captured by gravitational lysimeters and analyzed for dissolved reactive P (DRP) concentration. Tomato fruits from ten plants per plot were harvested three times at 88, 102, and 116 DAT. Phosphorus apparent recovery efficiency (ARE) and partial factor productivity (PFP) were calculated. Results showed that total P uptakes (TPU) were not significantly affected by P rates and averaged 12 kg ha^-1. The proportions of stem, leaf, root, and fruit in the TPU ranged from 16 to 22%, 40 to 46%, 0.8 to 1.2%, and 32 to 43%, respectively. The ratio of stem/TPU decreased with increasing P rates and reached a plateau at 106 kg ha^-1, but the proportions of leaf, root, and fruit were not significantly affected. Soil P and cumulative leachate DRP increased linearly with increasing P rates. The rate of 49 kg ha^-1 resulted in a higher ARE than 29, 78, and 98 kg ha^-1. Tomato marketable yield at the first and second combined harvest was predicted by a linear-plateau model with a critical rate of 56 kg ha^-1. There were no significant differences in the total season (three harvests combined) marketable yields, thus, the PFP decreased with increasing P rates. Consequently, in the calcareous soils with 51 mg kg^-1 of Mehlich-3 extractable P, 56 kg ha^-1 was sufficient to meet tomato P requirement.