Water Solubility and Physical Losses and Sulfur and Phosphorus from S-Coated Triple Superphosphates

Abstract

Coated fertilizer must retain the coating during transport and handling, but the nutrients in the coat must be
released readily in the soil to meet plant demand. Three experimental fertilizer where S is adhered to TSP granules
using AD1, AD3 or AD2 adhesive were compared with a commercial S coated TSP, Hifert (HF) Goldphos-10.
Fertilizer S loss from the granule was measured in a rotating drum friabilator. The highest particle loss was recorded
wit HF, and there were no significant differences recorded between AD1, AD2 and AD3. Release of S from the coated
fertilizers was measured by placing the fertilizers between 500 pm nylon mesh and leaching with distilled water
at 20 mL min-1 for up to 96 h. In all release was fastest from AD1 and AD3, and the amount of Ca and P released
from the granule was also highest with these two products. Granules were scanned in the electron microscope, and
electron microprobe both before and after leaching. Dispersion in distilled water was also recorded. The microprobe
scan confirmed the leaching data with more S remaining in the granule with HF than AD1 or AD3. These data
confirm earlier studies that the method of adhesion of S to TSP can markedly alter the agronomic performance of
the fertilizer.