Nitrogen Forms and Heavy Metals Leachability Following Biosolids Application to Sandy Soil.

Leaching poses a significant concern in dry regions with sandy soils due to their inherent
characteristics of low fertility, coarse texture, very low organic matter content, and limited water
retention capacity. The aim of this research was to minimize environmental consequences of applying
biosolids compost at high rates to sandy soils under arid conditions in terms of inorganic nitrogen and
heavy metals pollution. This investigation used a pot experiment that was incubated at a constant
temperature (25 0C) and comprised four application rates (0.0, 20, 40, and 60 t/ha) of compost, two
methods of application (mulching and incorporating) and two intermittent irrigation intervals (3 and 6
days). Results of this experiment revealed that the nitrate concentration in soil leachate exceeded 50
mg/L, a value considered highly poisonous if it exists in drinking water. Ammonia concentrations
exceeded 20 mg/L in the second leachate fraction but decreased to under detection limits in the last
fifteen leachate fractions for all compost treatments. The suggested maximum contamination level for
groundwater is 1.5 mg NH4-N-1. NO3-N concentrations in all soil leachate fractions were substantially
above the acceptable threshold in drinking water for people (10 mg/L) but far below the recommended
level in drinking water for cattle (100 mg/L). The findings provided strong evidence that the environment
is well safeguarded in terms of heavy metal concentrations in the soil leachate. From this research, it
may be stated that high loading rates of excellent quality compost to sandy soils is agronomically
advantageous with little potential environmental harm if handled effectively.