Plant growth improvement mediated by nitrate capture in co-composted biochar

Abstract

Soil amendment with pyrogenic carbon (biochar) is discussed as strategy to improve soil fertility to enable economic plus environmental benefits. In temperate soils, however, the use of pure biochar mostly has moderately-negative to -positive yield effects. Here we demonstrate that co-composting considerably promoted biochars’ positive effects, largely by nitrate (nutrient) capture and delivery. In a full-factorial growth study with Chenopodium quinoa, biomass yield increased up to 305% in a sandy-poor soil amended with 2% (w/w) co-composted biochar (BCcomp). Conversely, addition of 2% (w/w) untreated biochar (BCpure) decreased the biomass to 60% of the control. Growth-promoting (BCcomp) as well as growth-reducing (BCpure) effects were more pronounced at lower nutrient-supply levels. Electro-ultra filtration and sequential biochar-particle washing revealed that co-composted biochar was nutrient-enriched, particularly with the anions nitrate and phosphate. The captured nitrate in BCcomp was (1) only partly detectable with standard methods, (2) largely protected against leaching, (3) partly plant-available, and (4) did not stimulate N2O emissions. We hypothesize that surface ageing plus non-conventional ion-water bonding in micro- and nano-pores promoted nitrate capture in biochar particles. Amending (N-rich) bio-waste with biochar may enhance its agronomic value and reduce nutrient losses from bio-wastes and agricultural soils.

Action Research into a Flood Resilient Value Chain – Biochar-Based Organic Fertilizer Doubles Productivity of Pea in Udayapur, Nepal

“…The increase in production using biochar is in line with results observed by other authors for many other crops e.g. pumpkin, tomato and potato [2,20,21]. The difference in pea crop yield between NPK and FYM only treatment was not significant, which indicates that substituting chemical fertilizer for FYM would not lead to a meaningful increase in yield.…”

Biochar Application in Malaysian Sandy and Acid Sulfate Soils: Soil Amelioration Effects and Improved Crop Production over Two Cropping Seasons

“…Within this study the performance of rice husk biochar as a soil amendment in combination with the application of standard fertilizer rates was investigated. Further studies on the use of rice husk biochar fortified with nutrients from organic materials such as in Kammann et al [35] and the additional aspect of variable fertilizer rates will provide more alternatives for the utilization of rice husk biochar for improved crop production in Malaysia. Figure S6: Acid neutralizing capacity of the two rice husk biochars, Table S1: Standard fertilizer types and rates used for acid sulphate and sandy soil for corn and rice, Table S2: Soil exchangeable bases at harvest, Table S3: Yields of corn cropped under acid sulphate and sandy soil, and rice cropped under acid sulphate soil (t/ha) including the standard deviation of 4 measurements.…”

Mineral–Biochar Composites: Molecular Structure and Porosity

“…This results in loss of carbon and nutrients from the soil and a very large increase in harmful atmospheric carbon emissions 2 . Biochar production is seen as a key part of a strategy to effectively recycle biomass carbon and nutrients 3 , improve plant growth and mycorrhizal colonization 4 , improve soils physical and chemical properties, provide a source of renewable energy and act as a means for carbon sequestration 1,[5][6][7] . These vast quantities of readily available biomass, which are currently treated as waste for disposal, could be readily, cost effectively and widely converted into valuable biochar 1,[8][9][10] .…”