Nitrogen Assessment of Shallow Florida Histosols

Abstract

ABSTRACT The soils of the Everglades Agricultural Area (EAA) are mainly organic soils (Histosols), and their artificial drainage promoted aeration and resulted in soil subsidence. Sugarcane (Saccharum spp.) nitrogen (N) requirement has been fulfilled historically by organic matter mineralization, so very shallow soils could be limiting N availability for the crop. The objectives of this study were to measure sugarcane leaf N concentration and levels of available N across EAA organic soils with variable soil depth and then determine if there are relationships among soil depth, soil N concentration, and sugarcane leaf N concentration in Florida Histosols. A total of 60 plots were established in 30 commercial sugarcane fields in the EAA with soil depth varying from 15 to 145 cm over limestone bedrock. In each location, soil depth, soil, and leaf nutrient concentrations, and leaf chlorophyll measurements were determined during the grand growth period (June 1 – October 15) of the crop. There were no significant correlations between soil depth and either leaf N concentration or leaf chlorophyll measurements. There were positive correlations between soil water and soil NH4 +-N concentration and between soil NO3 –N concentration and leaf N concentration. Our results determined that mineralization is still providing adequate N supply for sugarcane.