One Year Residual Effect of Sewage Sludge Biochar as a Soil Amendment for Maize in a Brazilian Oxisol

Abstract

The thermochemical transformation of sewage sludge (SS) to biochar (SSB) allows exploring the advantages of SS and reduces possible environmental risks associated with its use. Recent studies have shown that SSB is nutrient-rich and may replace mineral fertilizers. However, there are still some questions to be answered about the residual effect of SSB on soil nutrient availability. In addition, most of the previous studies were conducted in pots or soil incubations. Therefore, the residual effect of SSB on soil properties in field conditions remains unclear. This study shows the results of nutrient availability and uptake as well as maize yield the third cropping of a three-year consecutive corn cropping system. The following treatments were compared: (1) control: without mineral fertilizer and biochar; (2) NPK: with mineral fertilizer; (3) SSB300: with biochar produced at 300 °C; (4) SSB300+NPK; (5) SSB500: with biochar produced at 500 °C; and (6) SSB500+NPK. The results show that SSB has one-year residual effects on soil nutrient availability and nutrient uptake by maize, especially phosphorus. Available soil P contents in plots that received SSB were around five times higher than the control and the NPK treatments. Pyrolysis temperature influenced the SSB residual effect on corn yield. One year after suspending the SSB application, SSB300 increased corn yield at the same level as the application of NPK. SSB300 stood out and promoted higher grain yield in the residual period (8524 kg ha−1) than SSB500 (6886 kg ha−1). Regardless of pyrolysis temperature, biochar boosted the mineral fertilizer effect resulting in higher grain yield than the exclusive application of NPK. Additional long-term studies should be focused on SSB as a slow-release phosphate fertilizer.

Pyrolysis of Sewage Sludge: Physical, Chemical, Morphological and Mineralogical Transformations

“…Compared with biochar from multiple feedstocks [19] and with other types of soil amendments [20], SSB has higher P levels, with great potential for use as a P fertilizer. Increases of Ca, Mg, S and micronutrients levels have also been reported in previous studies with SSB at 300ºC [8,17,21].…”

“…The increase in ash content is expected, since up to 600°C most of the mineral material is preserved and volatile compounds are lost, resulting in a higher ash concentration [15]. The pH value was not altered by pyrolysis and it was close to neutrality (6.5), similar to results previously reported for biochars obtained at low temperatures (300ºC) [7,8]. Typically, increases in pH are observed at higher pyrolysis temperatures (> 400°C).…”

“…Among feedstocks used for producing biochar, SS is considered a nutrient-rich material. In addition, recent research has shown that as a soil amendment SSB can provide nutrients and increase the use efficiency of several plant nutrients, resulting in high crop yields [5,7,8].…”

Revamping highly weathered soils in the tropics with biochar application: What we know and what is needed

“…Fading effect of biochar after multiple seasons might be attributed to leaching of alkali metals from biochar, signifying the need of reapplication of biochar. Similarly, Fachini et al (2021) found that positive effect of biochar on crop growth faded over time in an acidic soil of Brazil. Conversely, a few studies demonstrated biochar's positive effects on crop yield from second season onwards, indicating the effect of biochar aging on nutrient retention and supply to plants (Major et al, 2010;Griffin et al, 2017).…”

Phosphorus Footprint in the Whole Biowaste–Biochar–Soil–Plant System: Reservation, Replenishment, and Reception

“…Similarly, Fachini et al also found that the addition of sewage sludge biochar significantly promoted P uptake and maize yield in a three-year consecutive corn cropping system. 54 Figure S7 reveals that in original red soil, paddy soil, and yellow soil, the P uptakes of corn, rice, and wheat were approximately 1, 3, and 1.5 mg per pot as the unit, respectively. However, with the addition of SSBC, the P uptakes of the three plants increased to 4, 7, and 1 mg, respectively.…”