The Influence of Form and Rate on the Efficacy of Matrix-Based Fertilizers to Reduce Nutrient Leaching

We tested the efficacy of matrix-based fertilizers (MBFs) to reduce N O 3 , N H 4 , and total phosphorus (TP) leaching compared to Osmocote 14-14-14, a commercial slow release fertilizer (SRF) in greenhouse column studies. The MBFs covered a range of inorganic N and P in compounds that are relatively loosely bound (MBF4) and more tightly bound compounds (MBF5) with A 1 2 ( S O 4 ) 3 ⋅ 1 8 H 2 O and/or F e 2 ( S O 4 ) 3 ⋅ 3 H 2 O and with high ionic exchange compounds starch, chitosan, and lignin. When N and P are released, the chemicals containing these nutrients in the MBF bind N and P to an A l 2 ( S O 4 ) 3 ⋅ 1 8 H 2 O and/or F e 2 ( S O 4 ) 3 ⋅ 3 H 2 O starch- chitosan- lignin matrix. SRF leachate contained a greater amount of N O 3 , N H 4 , DRP, and TP than leachate from MBF4 and MBF5 regardless of whether fertilizers were pellets, banded or broadcast, or fertilizer rate. St Augustine grass growing in soils receiving MBF4 and MBF5 had decreased shoot biomass by 49% to 56% and decreased total biomass by 33% to 46% respectively as grass receiving SRF. Although further greenhouse and field testing are necessary, results of this initial investigation are promising and with further development, testing, and rate calibration should be competitive with commercial fertilizers in environmentally sensitive markets.