SOIL SURVEY OF ESSENTIAL AND TRACE ELEMENTS IN A PLOT AMENDED WITH BIOSOLID AFTER THREE SOWING SEASONS

The largest wastewater treatment plant in Mexico located near Monterrey has a production of 150 d.w. tons/day of biosolids that has to be landfilled with a high cost because amendment of biosolid is not permitted due to the lack of regulation. Biosolids can be of great value for farming in our semi-arid soil. The objective of the following survey is to determine the feasibility of amending biosolids to soil, increasing the availability of essential plant nutrients without increasing toxic elements in soil to an unsafe level. A survey was conducted to determine the behavior of the essential nutrients and toxic elements in soil amended with biosolids compared with inorganic fertilizer and control. Three seasons were sown with maize. Soil samples in the second and third season were collected consisting of a mixed of 4 replicates with a soil depth ranging from 0–30cm and were sent to Agricultural Analytical Services Laboratory of Pennsylvania State University. Essential nutrients analyzed were nitrate, ammonium, phosphorus, potassium, magnesium, calcium, manganese, iron, copper, and zinc. Non-essential or trace elements analyzed were lead, nickel, cadmium and chromium. Results indicate that when biosolid was amended higher amounts of essential nutrients of nitrate, phosphorus and zinc were encountered. Amounts added when soils are amended with biosolid are not sufficient for manganese, iron and copper. Potassium, magnesium and calcium could not be compared because the soil where the survey was conducted had high amounts. Extractable and total lead, nickel and cadmium were below tolerance limits in all treatments and total chromium was also below tolerance limits. It was concluded that biosolid amendment is safe in regard to heavy metals and can enhance plant growth at the dosage used in this survey.