ABSTRACT Potato cultivation requires fertilizers to sustain crop yields, but a significant percentage of added nutrients is lost by leaching. The use of coating materials for fertilizers is currently being considered to reduce these losses. The objective of this study was to determine if a carrageenin based hydrogel (CBH), used to coat fertilizer, decreases NH4 + and K+ leaching from a potato crop without affecting growth, specific gravity, and tuber yield. The CBH was tested in a diploid potato crop, cultivar Criolla Colombia (Solanum tuberosum L., Phureja Group) using a randomized full block design including the treatments noncoated fertilizer (T1), CBH coated fertilizer (T2), and no fertilizer (T3). Mineral nutrients in soil leachates together with dry biomass, foliar area, chlorophyll, tuber specific gravity, and yield were quantified. The nutrient content in leachates from T2 were below those from T1. No significant differences between treatments were observed for growth factors, yield, and tuber specific gravity. This study confirms the controlling effect of the CBH, ensuring the retention of the nutrients added in the fertilizer and preventing them from easily leaching. Future field studies are worthwhile to establish the amount of fertilizer this coating could save.

RESUMEN El cultivo de papa requiere fertilizantes para mantener su rendimiento. Sin embargo, un porcentaje significativo de los nutrientes anadidos se lixivia. Actualmente el uso de materiales de recubrimiento para los fertilizantes se está considerando para disminuir estas pérdidas. El objetivo de este estudio fue determinar si un hidrogel a base de carragenina (CBH, por sus siglas en inglés), utilizado para recubrir el fertilizante aplicado, puede disminuir la lixiviación de NH4+ y K+ en un cultivo de papa, sin afectar el crecimiento, gravedad específica y el rendimiento de tubérculo. El CBH se probó en un cultivo de papa diploide, cultivar Criolla Colombia (Solanum tuberosum L., Grupo Phureja) utilizando un diseno de bloques completos al azar. Se evaluaron los tratamientos: fertilizante sin recubrimiento (T1), fertilizante recubierto con CBH (T2) y sin fertilizante (T3). Se cuantificaron los nutrientes minerales en los lixiviados junto con biomasa seca, área foliar, clorofila, gravedad específica del tubérculo y rendimiento. Los conteni-dos de nutrientes en los lixiviados de T2 fueron inferiores a los de T1, y no se observaron diferencias entre estos tratamientos para factores de crecimiento, rendimiento y gravedad específica. Los resultados evidencian que el CBH tiene potencial como material de recubrimiento para fertilizantes en papa y, se debe complementar con otros ensayos para determinar la cantidad de fertilizante que este recubrimiento podría ahorrar.

Abstract The release kinetics of nitrogen and phosphorous of a granulated fertilizer, encapsulated in a κ-carrageenan-based hydrogel (CBH), was evaluated in order to determine its release mechanism given the potential this hydrogel has as coating material for controlled release fertilizers (CFRs). The effect of pH on the release properties was also investigated. The relationship between the NH4+, NO3-, and PO43- release of encapsulated fertilizers and time was determined by short- and long-term laboratory incubations. The mechanism of the release of nutrient ions was determined by comparing the release data with the zero-order, first-order, Higuchi, Hixon-Crowell and Korsmeyer-Peppas kinetic models. The findings showed that the Korsmeyer-Peppas model could be used to describe the release characteristics of the nutrients in the encapsulated fertilizers and that non-Fickian diffusion is the main release mechanism. The experimental hydrogel showed a high water retention capacity able to absorb 300 times its weight water.