Processing tomato phosphorus utilization and post-harvest soil profile phosphorus as affected by phosphorus and potassium additions and drip irrigation

Phosphorus (P) applied in agricultural land not only affects crop P utilization, but can also cause environmental concerns when excessive P applied moves off-site to surrounding water systems. A 2-yr study, 2007-2008, was conducted to determine the effects of fertilizer P (four rates: 0, 30, 60, and 90 kg P ha-1) and potassium (K) (four rates: 0, 200, 400, and 600 kg K ha-1) additions and drip irrigation on crop P utilization and post-harvest agronomic (i.e., Olsen P) and environmental [i.e., water extractable P (WEP)] soil test P under processing tomato in loamy sand soils. Plant P uptake increased, but apparent P recovery decreased with increases in fertilizer P rate. Cumulative soil WEP in the 0- to 100-cm soil profile and Olsen P in the 0- to 20-cm depth increased linearly with increases in fertilizer P rate, regardless of water management. No effects of K were found on plant P utilization, soil WEP, or soil Olsen P. Drip irrigation increased plant P uptake by 35% and apparent P recovery by 44%, relative to non-irrigation. Drip irrigation consequently decreased the post-harvest soil profile WEP by 14% and Olsen P by 6.5% averaged across the 2 yr, compared with non-irrigation. Drip irrigation reduced the potential for post-harvest soil P losses by improving P utilization. the addition of fertilizer P needs to be optimized by considering crop P needs in association with actual yield production to ensure processing tomatoes are produced in an environmentally sustainable manner.