Nutrient leaching from soil amended with apple waste

Overview & Synopsis

Among the possibilities for disposing of overproduction of apple, land application is flexible and inexpensive. Six soil columns receiving 0, 200 or 500 Mg of apple waste$\cdot$ha$^{-1}$ were studied in laboratory experiments with various irrigation depths and timing, and alternate irrigated and drying periods. Leaching solutions were collected at different times for chemical analyses. Organic matter input stimulated microbial activity that used O$_2$ and released CO$_2$, then reduction occurred. Major cations like Ca$^{2+}$, Mg$^{2+}$, and K$^+$ involved in mineral dissolution or soil solution exchange were released. High N immobilization and possibly denitrification occurred, organic C was leached, while decreasing redox potential led to Mn dissolution and sulfate reduction. The reoxidation of the soil during drying helped to restore the soil to a condition which pollutes less. Quantities of apple waste deposition less than 200 Mg$\cdot$ha$^{-1}$ are recommended to minimize environmental damage.