Release of essential plant nutrients from manure- and wood-based biochars

Mahmudul Islam Piash,Kazunori Iwabuchi,Takanori Itoh,Koki Uemura

doi:10.1016/j.geoderma.2021.115100

Abstract

Several biochars have a considerable amount of essential plant nutrients; however, the release of those nutrients in soil is not well understood. Therefore, in this study, six biochars with varying nutrient contents were produced from Japanese larch (Larix kaempferi, JL), dairy manure (DM), and chicken manure (CM) at 300 and 500 °C and incubated in a temperate clay loam soil to investigate their nutrient release dynamics. The available N, P, and K release patterns of the biochars (2% dry-basis) were compared with the recommended fertilizer dose of sweet corn (Zea mays convar. saccharata) for 120 days. The results indicated that only chicken manure biochars (C/N ratio < 8) have the potential to satisfy plant needs by releasing sufficient N, P, and K. Fourier-transform infrared analysis revealed that N-containing amide dissolution was the major mechanism behind the 49% N release from the CM300 biochar. A higher production temperature (500 °C) diminished most of these amides, resulting in lower N release from CM500 (8.9%). Nitrification-induced reduction of soil pH caused Ca/Mg-P dissolution from manure biochars and enhanced P release. Much of the released phosphates later became unavailable in the soil by aluminosilicate complex formation. DM biochar also released adequate P and K, and production at 500 °C generally performed better than at 300 °C. Effect of coexisting ions on some nutrient release was found, though was statistically nonsignificant. Overall, results revealed that low-temperature (≤500 °C) CM and DM biochars can become comprehensive or complementary sources of plant nutrients, respectively, with some enhanced nutrient-retaining potential, although inherent soil properties may play a significant role.

Highlights

Recent increases in global crop production have been mainly achieved by greater inputs of chemical fertilizer (Tilman et al, 2002), and the input is expected to increase further with future food demand.the manufacturing process of these synthetic fertilizers is energy-intensive, and mineral stocks for production are limited.the environmental cost of fast-releasing chemicals has been substantial, including water quality degradation, eutrophication, photochemical smog formation, and nitrous oxide emissions (Vitousek et al, 2009)
All the biochars had alkaline pH, except the JL biochar pyrolyzed at 300 ◦ C
Under the described pyrolysis conditions, the biochar yields ranged from 29.11% to 69.82%, with the highest for the CM300 biochar

Summary

Introduction

Recent increases in global crop production have been mainly achieved by greater inputs of chemical fertilizer (Tilman et al, 2002), and the input is expected to increase further with future food demand.the manufacturing process of these synthetic fertilizers is energy-intensive, and mineral stocks for production are limited.the environmental cost of fast-releasing chemicals has been substantial, including water quality degradation, eutrophication, photochemical smog formation, and nitrous oxide emissions (Vitousek et al, 2009). Biochar might become a reasonable alternative in this regard, which can efficiently supply soil nutrients and maintain microbial biodiversity for sustainable crop production (Guo et al, 2016; Lehmann and Joseph, 2015). While most organic fertilizers like manure and mulches undergo fast microbial decomposition, biochar with a large proportion of recalcitrant carbon remains in the soil for a considerably longer period (Duku et al, 2011; Lehmann and Rondon, 2006). Biochar has the potential to improve some physical, chemical, and biological properties of soil (Guo et al, 2016; Igalavithana et al, 2016). Most studies so far have mainly focused on the ability of biochars to sequester carbon, remove pollutants, and improve soil physical properties (Kamali et al, 2020). Very few studies have emphasized its nutrient supplying potential, this could be the key point to encourage marginal farmers for extensive biochar use

Methods

Results

Conclusion