Soil amendment with biochar increases the competitive ability of legumes via increased potassium availability

Abstract

Soil amendment with biochar is currently proposed as a management strategy to improve soil quality and enhance plant productivity. Relatively little is known about how biochar affects plant competition, although it has been suggested that it can increase the competitive ability of legumes. This study tested the impact of a biochar on the competitive ability of legumes through alterations to soil pH and/or nutrient availability. Biochar was produced from aboveground plant biomass from a species-rich semi-natural grassland pyrolysed at 400°C. In a greenhouse experiment, a legume (red clover, Trifolium pratense L.); a grass (red fescue, Festuca rubra L.); and a forb (plantain, Plantago lanceolata L.) were grown in (1) monocultures, (2) in a mixed culture of red fescue and red clover, and (3) in a mixture of all three species. Soil treatments included fertilization with nitrogen (N), potassium (K), phosphorus (P), or micronutrient fertilizer in the presence or absence of biochar; a pHadjusted control soil; and a control (i.e. with no amendment). The competitive ability of red clover was quantified as the proportion of aboveground biomass of this species within the mixtures. Both biochar amendment and K fertilization significantly (P < 0.001) increased red clover biomass, and increased the competitive ability of red clover when grown with red fescue and plantain. Application of N fertilizer, irrespective of biochar amendment, resulted in significantly (P < 0.001) greater red fescue and plantain biomass and eliminated the competitive advantage of red clover. The biochar-mediated pH increase did not affect red clover biomass or its competitive ability. We conclude that biochar has a beneficial effect on red clover under N limiting conditions due to an increase in K availability. Our results suggest a potential role for biochar to maintain the proportion of forage legumes in agricultural pastures or semi-natural grasslands.

Farmer‐led maize biochar trials: Effect on crop yield and soil nutrients under conservation farming

“…By contrast, concentrations of K in maize stover were significantly increased upon biochar addition (Table 4). Increased concentrations of K in red clover, red fescue and plantain in treatments with biochar as compared to no biochar were recently reported by Oram et al (2014). Concentrations were greater and more variable in the stover (3 to 7.1 g kg −1 ) as compared to the grains (3.2 to 3.7 g kg −1 ).…”

Effect of biochar amendment on yield and photosynthesis of peanut on two types of soils

“…Recent studies suggest that K fertilization effect of biochar is critical for promoting growth, biological N fixation and competitive ability of legume species (Mia et al 2014;Oram et al 2014). In our study, the high K concentration in the peanut shell biochar may also contribute to the production response of peanuts, especially on redoxi-hydrosol which displays a very strong K deficiency.…”

Biochar and biochar-compost as soil amendments: Effects on peanut yield, soil properties and greenhouse gas emissions in tropical North Queensland, Australia

“…Because biochar contains ash and so adds nutrients such as K, Ca and Mg to the soil solution, increasing the pH of the soil and providing readily available nutrients for plant growth (Glaser et al, 2002). Recent studies suggest that a K fertilization effect associated with biochar is critical for promoting growth, biological N fixation and the competitive ability of legume species (Mia et al, 2014;Oram et al, 2014;Xu et al, 2015). In this study, high K concentrations in the Com and COMBI treatments may also have contributed to the peanut yield response associated with the organic amendments, where a significant increase in soil available K was observed.…”