Estimating Nitrogen Availability of Heat-Dried Biosolids

Abstract

As heat-dried biosolids become more widely produced and marketed, it is important to improve estimates of N availability from these materials. Objectives were to compare plant-available N among three different heat-dried biosolids and determine if current guidelines were adequate for estimating application rates. Heat-dried biosolids were surface applied to tall fescue (Festuca arundinacea Schreb.) in Washington State, USA, and forage yield and N uptake measured for two growing seasons following application. Three rates of urea and a zero-N control were used to calculate N fertilizer efficiency regressions. Application year plant-available N (estimated as urea N equivalent) for two biosolids exceeded 60% of total N applied, while urea N equivalent for the third biosolids was 45%. Residual (second-year) urea N equivalent ranged from 5 to 10%. Guidelines for the Pacific Northwest USA recommend mineralization estimates of 35 to 40% for heat-dried biosolids, but this research shows that some heat-dried materials fall well above that range.

Dryland Winter Wheat Yield, Grain Protein, and Soil Nitrogen Responses to Fertilizer and Biosolids Applications

“…Based on previous research on N availability from dewatered and heat-dried biosolids [10] we estimated plant-available N of both biosolids sources as 25% of total N under the conditions of this study and used that estimate for our field application rates ( Table 2). In a more recent study of heat-dried biosolids conducted in western Washington State in 2007-2009, Cogger et al [11] reported much greater N availability from Soundgro, and we adjusted our estimate of available N applied from Soundgro to 50% of total N. The ramifications of this change are discussed later. Biosolids were surface applied at or up to two weeks prior to planting at each location.…”

“…Initial attempts to target biosolids agronomic rates to match the intermediate (56 or 90 kg N ha −1 ) or high (112 or 180 kg N ha −1 ) N fertilizer rates were apparently unsuccessful based on N availability calculations as a fraction of total N in the materials (Table 2). These availability indices were developed from studies in which biosolids were applied in the fallow period of a crop-fallow rotation and were incorporated with tillage [3,18] or broadcast on the surface for a perennial forage crop [11]. In the present study, biosolids were applied shortly before planting and left on the surface.…”

Evaluation of phytotoxicity of three organic amendments to collard greens using the seed germination bioassay

“…Milorganite (Milwaukee Organic Nitrogen) is prepared from heat-dried microbes that digested municipal and industrial wastes from Milwaukee Metropolitan Sewerage District (MMSD) (Archer 2007 ). Milorganite can be used as a soil amendment and fertilizer for the production of diverse crops (Cogger et al 2011 ). According to the label on the packaging materials, the nitrogen contents of milorganite, chicken manure, and cow manure is 6%, 3%, and 0.5%, respectively, which were validated in our lab by analyzing samples from these organic amendments using inductive coupled plasma optical emission spectrometer (Agilent ICP-5100) working with both radial and axial view and C, H, N, and S content using elementar vario Macro tube.…”

“…In addition, the level of nitrogen, the most limiting plant nutrient, in organic amendments is lower than in conventional inorganic fertilizers (Rigby and Smith 2014 ). Moreover, the nitrogen in organic fertilizers and soil amendments is slowly released to plants (Cogger et al 2011 ). Therefore, to meet nitrogen requirements of crops, organic amendments are applied at higher rates (Cogger et al 2011 ).…”

“…Moreover, the nitrogen in organic fertilizers and soil amendments is slowly released to plants (Cogger et al 2011 ). Therefore, to meet nitrogen requirements of crops, organic amendments are applied at higher rates (Cogger et al 2011 ). Besides nitrogen, organic amendments contain plant macro- and micronutrients including phosphorus, potassium, copper, zinc, iron, and heavy metals, such as chromium, arsenic, selenium, nickel, and salts (Alvarenga et al 2015 ).…”