Contents lists available at ScienceDirect Soil & Tillage Research journal homepage: www.elsevier.com/locate/still Original paper Assessment of crop residue and palm shell biochar incorporation on greenhouse gas emissions during the fallow and crop growing seasons of broccoli (Brassica oleracea var. italica) Daniel Basalirwa a , Shigeto Sudo b , Cosmas Wacal a , Fuyumi Akae c , Aung Zaw Oo d , Sho Koyama c , Daisuke Sasagawa a , Sadahiro Yamamoto f , Tsugiyuki Masunaga e , Eiji Nishihara f, ⁎ a The United Graduate School of Agricultural Sciences, Tottori University, 4-101 Koyama-Minami, Tottori, 680-8553, Japan b Institute for Agro-Environmental Science (NIAES), National Agriculture and Food Research Organization (NARO), 3-1-3 Kannondai, Tsukuba, Ibaraki, 305-8604, Japan c Graduate School of Sustainability Science, Tottori University, 4-101 Koyama-Minami, Tottori, 680-8553, Japan d Japan International Research Center for Agricultural Science (JIRCAS) 1-1 Ohwashi, Tsukuba, 305-8686, Japan e Faculty of life and Environmental Science, Shimane University, 1060 Nishikawatsu, Matsue, Shimane 690-8504, Japan f Faculty of Agriculture, Tottori University, 4-101 Koyama-Minami, Tottori, 680-8553, Japan ARTICLEINFO Keywords: Broccoli crop residues Palm shell Biochar Greenhouse gas emission Soil properties N uptake Plant biomass ABSTRACT The impact of broccoli crop residues on greenhouse gas (GHG) emissions may vary with post-harvest manage- ment. The incorporation of biochar together with broccoli residues could have a GHG mitigation potential in soil. A feld experiment was conducted to evaluate the combined efect of broccoli crop residues and palm shell biochar (PSB) incorporation on GHG emissions during the fallow (post-harvest) and crop growing seasons of broccoli. We also evaluated the plant biomass, N uptake, and soil chemical properties after harvest. The treat- ments included; No-residues (NR), Residues (R), Residues + 10 t ha −1 PSB (R10), Residues + 20 t ha −1 PSB (R20) and Residues + 40 t ha −1 PSB (R40), arranged in a completely randomized block design. The fallow season had signifcantly higher GHG emissions than the crop growing season. Incorporation of crop residues in soil signifcantly increased N 2 OandCO 2 emissions but did not signifcantly afect CH 4 emissions when compared to those of the NR treatment. PSB amendment did not signifcantly afect N 2 O,CO 2 and CH 4 emissions from crop residues and also the biomass and N uptake of the crop residues remaining after broccoli harvest. The application of PSB at 40 t ha −1 signifcantly increased the total N, total C, C/N ratio and exchangeable K but did not signifcantly afect soil pH, EC, available P, exchangeable Ca and Mg, and CEC. The large amounts ofN 2 O and CO 2 emissions emitted from broccoli crop residues during the fallow season may necessitate higher biochar application rates to achieve the GHG mitigation potential of biochar while maintaining a high soil nutrient status. The combined incorporation of broccoli crop residues with biochar requires further evaluation in terms of GHG emissions, soil nutrient status and broccoli crop yield in diferent soil types and tillage systems. 1. Introduction Agriculture is among the main anthropogenic sources of greenhouse gas emissions (IPCC, 2013). The anthropogenic N inputs in agricultural systems include N from chemical fertilizer, animal wastes, increased biological N-fxation, cultivation resulting in enhanced organic matter mineralization, and mineralization of crop residues in the feld (Mosier et al., 1998). Crop residue incorporation in the soil is an important strategy to maintain soil fertility but its infuence on greenhouse gas (GHG) emissions should be considered (Lehtinen et al., 2014). A number of studies have shown that crop residue incorporation in soil results in an increase in N 2 O and CO 2 emissions (Neeteson and Carton, 2001; Velthof et al., 2002; Huang et al., 2004; Nett et al., 2015; Gao et al., 2016; Nguyen et al., 2016; Badagliacca et al., 2017; Scheer et al., 2017; Pugesgaard et al., 2017), but has no signifcant efects on CH 4 emissions in upland felds (Nguyen et al., 2016). Vegetables in the brassica family leave large amounts of highly moist and nitrogenous rich residues in the soil which through decom- position, result into a substantial increase in N 2 O emission (Rahn et al., 2003; Nett et al., 2016). For instance, caulifower residues contain 80 to 120kgNha −1 , white cabbage and brussel sprout residues contain 150 to250kgNha −1 (Neeteson and Carton, 2001) while broccoli residues https://doi.org/10.1016/j.still.2019.104435 Received 1 February 2019; Received in revised form 19 September 2019; Accepted 26 September 2019 ⁎ Corresponding author at: Faculty of Agriculture, Tottori University, 4-101 Koyama-Minami, Tottori, 680-8553, Japan. E-mail address: nishihar@tottori-u.ac.jp (E. Nishihara). Soil & Tillage Research 196 (2020) 104435 0167-1987/ © 2019 Elsevier B.V. All rights reserved. T