Charcoal Volatile Matter Content Influences Plant Growth and Soil Nitrogen Transformations

Abstract

A series of short‐term greenhouse experiments and laboratory incubations were conducted to evaluate the effect of macadamia (Macadamia integrifolia Maiden & Betche) nut shell (MNS) charcoal with varying volatile matter (VM) content on soil properties and plant growth in two tropical soils. Lettuce (Lactuca sativa L.) and corn (Zea mays L.) were planted in an Andisol amended with four rates of MNS charcoal (0, 5, 10, and 20% w/w) containing relatively high VM content (225 g kg−1) with and without N fertilizer. Increasing rates of charcoal without N caused a significant decline in both lettuce and corn growth. Corn growth declined significantly with or without N at the two highest charcoal rates. In a third experiment, corn growth also declined significantly in an Ultisol amended with the MNS charcoal (5% w/w) with and without fertilizers. In a fourth experiment, charcoals with high VM (225 g kg−1) showed negative effects on plant growth while the low‐VM (63.0 g kg−1) charcoal supplemented with fertilizer showed a significant positive effect on corn growth. Results from the 2‐wk incubation experiments showed that high‐VM charcoal caused a significant decline in soil NH4+–N and a significant increase in soil respiration compared with the soil amended with low‐VM charcoal and the soil alone. We propose that phenolic compounds and other products in the high‐VM charcoal stimulated microbial growth and immobilization of plant‐available N. Our results demonstrate that VM content appears to be an important property of charcoal that has short‐term effects on soil N transformations and plant growth. Longer incubation experiments and field trials are needed to further elucidate the role of charcoal VM content on soil processes and plant growth.

Crop response to soils amended with biochar: expected benefits and unintended risks

“…Commonly available commercial BCs, derived from wood biomass and crop residues, are poor in nutrients, but can positively affect nutrient availability and crop growth only if enriched with nutrients pre-application or if applied in combination with fertilisers (Deenik et al, 2010;Yao et al, 2015). Manure and biosolid-derived BCs, which are used less often than wood BCs, can function as both amendments and biofertilisers given their nutrient-rich original feedstocks Hossain et al, 2015;Cantrell et al, 2012;Subedi et al, 2016aSubedi et al, , 2016b.…”

“…Others have reported no yield effect (Cornelissen et al, 2013;Uzoma et al, 2011;Nelissen et al, 2015;Subedi et al, 2016aSubedi et al, , 2016bNielsen et al, 2014;Tammeorg et al, 2014;Suddick and Six, 2013;Schmidt et al, 2014;Bass et al, 2016). Conversly, few studies have instead described reduced crop yields (Deenik et al, 2010;Baronti et al, 2010;Marks et al, 2014;Nelissen et al, 2014;Bass et al, 2016;Butnan et al, 2015;Laghari et al, 2015). Therefore, interest has emerged to study BC effects that negatively alter crop growth (Jeffery et al, 2011(Jeffery et al, , 2015aSpokas et al, 2012;Biederman and Harpole, 2013;Wang et al, 2016, Olmo et al, 2016.…”

“…organic as well as inorganic (Steiner et al, 2007;Deenik et al, 2010;Subedi et al, 2015). This is probably due to the positive interaction between BC and applied fertiliser that improved the availability of nutrients associated with enhanced plant uptake and reduced losses of these nutrients.…”

“…Despite its many benefits, BC also poses risks, associated with the properties of the original feedstock and thermal process conditions (Deenik et al, 2010;Spokas et al, 2011;Freddo et al, 2012;Barrow, 2012;Quilliam et al, 2013b;Butnan et al, 2015;CampsArbestain et al, 2015;Domene et al, 2015;Genesio et al, 2016). These can range from heavy metal soil accumulation to toxic compound release, and to other negative effects on soil biota and human health.…”

Soil Health, Crop Productivity, Microbial Transport, and Mine Spoil Response to Biochars

“…As the pyrolysis temperature increases (400 to 500°C), most of the volatile material is removed as a gas, and the remaining non-volatile solid material undergoes further structural conversion. Some volatile material can re-condense as tar-like compounds and become associated with the biochar matrix [16]. After the loss of volatile material, biochars will possess an amorphous core matrix composed of aromatic and aliphatic compounds that can have attached carbonyl and hydroxyl functional groups [17].…”