Location: Agroecosystem Management Research
Title: On-site assessment of extractable soil nutrients after long-term biosolids applications to perennial forage Authors
Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 28, 2014
Publication Date: N/A
Interpretive Summary: Growing urban populations present a serious waste disposal issue for city services, which must find ways to dispose of municipal waste (such as biosolids) in an environmentally safe, cost-efficient manner. Recycling biosolids by land application can support agricultural production while also providing a cost-effective waste disposal plan. The effects of long-term, repeated land applications on soil nutrients and possible water quality issues from this practice are not clear. At a municipal biosolids recycling facility in central Texas, we found that soil nitrogen and phosphorus increased with application rate, but soil potassium did not change. Losses of nitrogen as nitrate were a greater risk at the highest biosolids application rates (20 and 30 tons per acre per year). Based on soil characteristics, biosolids applications every other year at the lowest rate (10 tons per acre per year) appears to be the most sustainable management practice for this municipal biosolids recycling site.
Technical Abstract: The objective of this study was to evaluate soil nutrient loading and depth distributions of extractable nitrogen (N), phosphorus (P), and potassium (K) after long-term, continuous annual surface-applications of anaerobically-digested Class B biosolids at a municipal recycling facility in central Texas. Commercial forage production fields were surface-applied at 0, 20, 40, or 60 Mg dry biosolids/ha/y for 8 years. Application duration was evaluated in fields applied with 20 Mg dry biosolids/ha/y for 0, 8, or 20 years. Total soil loads of extractable inorganic N and P increased linearly with application rate, but only extractable P increased with duration. Neither total load nor soil distribution of extractable K was affected by biosolids applications. Mineralization of biosolids-derived organic N and P appeared to contribute to elevated soil concentrations of nitrate throughout the profile and of orthophosphate in the top 30 to 40 cm.