Effects of copper rates and soil pH on growth and nutrient uptake by citrus seedlings

Soil properties, primarily pH and organic matter, influence phytotoxicity o f copper(Cu). A pot experiment was conducted to evaluate the effects of cop per additions (0, 25, 50, 100, 200, and 400 mg kg(-1)) to three different s oils [Myakka fine sand (pH 5.7), Candler fine sand (pH 6.5), and Oldsmar fi ne sand (pH 8.2)] on growth, and uptake of phosphorus (P), potassium (K), c alcium (Ca), magnesium (Mg), and copper (Cu) by Swingle Citrumelo (SC) seed lings. In unamended soils, the seedling growth was similar in the Myakka an d Candler fine sands (pH 5.7 to 6.5), but was significantly greater in the Oldsmar fine sand (pH 8.2). Increasing the rate of Cu from 0 to 400 mg kg(- 1) decreased the soil pH by 0.98 unit in the Candler fine sand, by 1.57 pH unit in the Myakka fine sand, and negligible effects on the pH of the Oldsm ar fine sand. The growth of SC seedlings decreased significantly with an in crease in Cu rates in the Myakka and Candler fine sands, but not in the Old smar fine sand. The Cu concentration in the leaves and roots increased subs tantially with an increase in the Cu rate applied to the Candler and Myakka fine sands while the effect was marginal in the Oldsmar fine sand. The abo ve effect wars more pronounced on fire Gu concentration in the roots than i n the leaves. Increased rate of Cu application decreased the uptake of P, M g, Ca, and K in the roots and leaves of the seedlings grown in the Myakka a nd Candler fine sands but not in the Oldsmar fine sand.