Nitrogen is the most limiting nutrient for pasture production in Florida so annual inputs of N from organic and inorganic sources are needed to produce adequate forage. Various sources of N have been used to meet forage requirements or restore soil productivity including biosolids (Adjei and Rechcigl, 2002), ammonium nitrate (NH₄NO₃) (Blue, 1988a; Petrovic, 1990) ammonium sulfate ((NH₄)₂SO₄) (Blue, 1988b; Adjei et al., 1999) and calcium nitrate (Ca(NO₃)₂) (Blue, 1974).

Ammonium sulfate is a byproduct of the nylon industry with agricultural use. Ammonium nitrate fertilizer is still widely used on pasture while use of calcium nitrate is showing a come back. At a competitive N selling price, ammonium sulfate provides sulfur and calcium nitrate provides calcium, both of which are essential nutrients for plant growth, but ammonium nitrate does not provide any additional plant nutrient. Hence ammonium sulfate and calcium nitrate may be used as substitutes to ammonium nitrate to advantage. Though (NH₄)₂SO₄ may accelerate soil acidification, its inherent capability to increase P availability in soils could outweigh the acidification problem. Moreover, calcareous soils or soils with high pH due to prolong applications of lime-stabilized biosolids may benefit from (NH₄)₂SO₄ but not from Ca(NO₃)₂ substitution. Thus, we propose to study the pros and cons of using (NH₄)₂SO₄ vs. NH₄NO₃ and Ca(NO₃)₂ as pasture fertilizers. Specifically, we will determine the effects of (NH₄)₂SO₄, NH₄NO₃ and Ca(NO₃)₂ on soil characteristics, and forage quantity and quality.