Biochar improves diary pasture yields by alleviating P and K constraints with no influence on soil respiration or N2O emissions

Abstract

Dairy pastures can be a major source of soil nitrous oxide (N 2 O) emissions due to the combination of intensive nitrogen (N) fertiliser use and high soil water content, from either rainfall and/or irrigation. Biochar application is a promising approach to lower soil greenhouse gas emissions, particularly under high soil moisture conditions where denitrification is the primary N-transformation pathway. In a replicated field trial, we evaluated the effects of two contrasting biochars derived from poultry litter and from hardwood on soil N 2 O emissions, soil ammonium (NH 4 +) and nitrate (NO 3 −) status, pasture productivity and herbage nutrient content. A liming treatment to mimic the liming equivalence of the poultry litter biochar was used to separate any effects observed from changes in soil pH. To further separate the effects of biochars on soil N status, N 2 O emissions and pasture N uptake, high and low N fertiliser doses (annual application of 672 kg N ha −1 , 336 kg N ha −1) were superimposed across all of the treatments. The N fertiliser dose had no significant impact on pasture yield. Application of poultry litter biochar resulted in significant increases in pasture productivity under both high and low N inputs. This was achieved by alleviating soil P, and possibly K nutritional constraints that are typical in Australian Ferralsols. Under the high N fertiliser dose, emissions of N 2 O from the treatments and control were not significantly different (p > 0.05) and ranged between 1.14 and 1.78 kg N 2 ON ha −1 across the 11-month study. The low N dose resulted in significantly lower emissions of N 2 O of between 0.80 and 0.84 kg N 2 ON ha −1 , but biochar had no significant effect on net emissions across the season. The lack of impact of biochar on N 2 O emissions was attributed to the relatively dry conditions over the trial period resulting in nitrification being the most likely N-transformation pathway. During brief episodes of high soil moisture, peak emissions from the biochar plots were lower than from the control or lime treatment, but these differences did not impact on the emission budget over the 11-month sampling campaign.

Surface-applied or incorporated biochar and compost combination improves soil fertility, Chinese cabbage and papaya biomass

“…The higher P in the amended soil increased P availability and subsequent plant uptake, which was supported by other similar studies (Agegnehu et al 2016c;Bass et al 2016;Manolikaki and Diamadopoulos 2019;Van Zwieten et al 2019). Greater plant P uptake from amended soil was particularly evident in the Andisol, a soil inherently deficient in P (Uehara and Ikawa 2000).…”

Role of biochar in promoting circular economy in the agriculture sector. Part 1: A review of the biochar roles in soil N, P and K cycles

“…Amendment with biochar from K-rich crop residues, particularly those made from wheat straw, increased available K in sandy loam soil [104]. Application of poultry litter and hardwood biochar improved diary pasture yield in Australian Ferralsols, which was attributed to the alleviation of K and P nutrient constraints in the Ferralsol regardless of the N fertiliser dose applied [48].…”

“…According to Borchard et al [38], in general, the reduction of N 2 O emission due to biochar application tends to have a minor effect after 1 year. The benefits of biochar on soil greenhouse gas emissions are also highly influenced by soil conditions, especially the water content, which controls N-cycling pathways [48]. Considering the many types of biochars that affect the soil N 2 O emissions differently, further research into the use of these materials in crops under different field conditions is required [49].…”

Biochar-induced changes in metal mobility and uptake by perennial plants in a ferralsol of Brazil’s Atlantic forest

“…The soils were initially in a suboptimal state for the growth of manioc, mainly due to low pH (close to the critical levels of pH 4.6) and because of the low potentially mobile concentrations of K, Ca, and Mg (refer to chapter 9 in Howeler 2014). K and P are particularly critical nutrients in ferralsols (van Zwieten et al 2019). Potassium is a particularly critical nutrient for manioc (Fernandes et al 2017), and it can become more important than P in South America's subtropical regions (Baligar et al 2001).…”