Is phosphorus fertilization necessary for watermelon production on high phosphorus soils?

Abstract

Nutrient loading has created water quality problems in the Chesapeake Bay watershed of the United States. This study was designed to examine if a high yield of quality watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] can be produced with reduced phosphorus (P) fertilizer inputs and the use of a preceding cover crop on high P soils of the Eastern Shore of Maryland. Watermelon was planted on a Norfolk soil (fine loamy, siliceous, thermic type kandiudults) in a split plot design, with four replications. The main plot treatments were cover crops (rye versus no cover) and the sub-plot treatments were five different P-fertilizer rates ranging from 0 to 60 kg P ha-1, at 15 kg ha-1 increments. Following harvest, all P fertility regimes left behind “excessive” P levels based on soil tests. The addition of P-fertilizer to these soils was unnecessary for the production of a high yield of marketable quality watermelons. In two of three sites, the use of cover crops preceding the watermelon crop increased yields and fruit size. Use of a rye cover crop and reduced P-fertilizer inputs could have a positive environmental impact by reducing the risk of P over-loading without negatively impacting watermelon yield and quality. Key words: Watermelon quality, phosphorus-reduction, rye cover crop, phosphorus loading