Biochar boosts tropical but not temperate crop yields

Abstract

Applying biochar to soil is thought to have multiple benefits, from helping mitigate climate change [1,2], to managing waste [3] to conserving soil [4]. Biochar is also widely assumed to boost crop yield [5,6], but there is controversy regarding the extent and cause of any yield benefit [7]. Here we use a global-scale meta-analysis to show that biochar has, on average, no effect on crop yield in temperate latitudes, yet elicits a 25% average increase in yield in the tropics. In the tropics, biochar increased yield through liming and fertilization, consistent with the low soil pH, low fertility, and low fertilizer inputs typical of arable tropical soils. We also found that, in tropical soils, high-nutrient biochar inputs stimulated yield substantially more than low-nutrient biochar, further supporting the role of nutrient fertilization in the observed yield stimulation. In contrast, arable soils in temperate regions are moderate in pH, higher in fertility, and generally receive higher fertilizer inputs, leaving little room for additional benefits from biochar. Our findings demonstrate that the yield-stimulating effects of biochar are not universal, but may especially benefit agriculture in low-nutrient, acidic soils in the tropics. Biochar management in temperate zones should focus on potential non-yield benefits such as lime and fertilizer cost savings, greenhouse gas emissions control, and other ecosystem services.

Biochar and/or Compost Applications Improve Soil Properties, Growth, and Yield of Maize Grown in Acidic Rainforest and Coastal Savannah Soils in Ghana

“…According to Duku et al [2], the impact of biochar application is most seen in highly degraded acidic or nutrient-depleted soils. Results from Jeffery et al's [11] study also show that biochar can be B0 � control with no amendments; B20 � biochar 2%, w/w; C20 � compost 2%, w/w; BC � combined biochar and compost rate 1% compost + 1% biochar; LSD � least significant difference at 0.05. Means with different letters differ significantly at P < 0.05 and with same letters do not differ significantly.…”

“…Furthermore, application of biochar to soils has been identified as a low-cost technology that can stabilize organic carbon, reduce greenhouse gas emissions [10], improve soil physical and chemical properties, and boost crop yield and productivity [11,12] and farm incomes. Biochar application can lead to a reduction in inorganic fertilizer use by farmers [2].…”

Biochar reduces yield-scaled emissions of reactive nitrogen gases from vegetable soils across China

“…The application of biochar is usually intended to increase crop yields, and evidence suggests that this may be successful (Schulz et al, 2013;Li et al, 2017;Jeffery et al, 2017). Due to its liming effect, biochar helps to improve the supply of essential macro-and micronutrients for plant growth (Chan and Xu, 2009;Major et al, 2010).…”

“…Enhancement of vegetable yield with biochar amendment occurred in Cambisol and Phaeozem (Table 3e). Additionally, the effects of B m and B w on vegetable yield differed, which was probably due to large differences in physicochemical characteristics between the two biochars (Jeffery et al, 2017). First, compared to B w , B m has a higher DOC content (Table S1), through which more nutrients may be directly introduced to the soil (Rajkovich et al, 2012).…”

“…The amendment of agricultural ecosystems with biochar has been proposed as an effective countermeasure for climate change (Smith, 2016). These additions have been suggested to increase soil carbon storage (Mukherjee and Zimmerman, 2013;Stavi and Lal, 2013), decrease greenhouse gas emissions (Li et al, 2017), and improve soil fertility and crop production (Major et al, 2010;Liu et al, 2013;Jeffery et al, 2017). However, some recent studies have reported no difference or even an increase in soil N 2 O emissions induced by biochar application for various soils (Saarnio et al, 2013;Wang et al, 2015a).…”