Appropriate tillage practices reduce a crop’s carbon footprint (CF) and mitigate climate change. However, little is known about the CF of winter wheat and spring maize production under different tillage practices in the Loess Plateau of China. To quantify the tillage differences and crop type differences in CF, a field experiment was established in 2007 in which the following six tillage practices were evaluated: plow tillage (PT), no-tillage (NT), subsoil tillage (ST), PT/NT rotation, NT/ST rotation and ST/PT rotation. The results showed PT had the positive CF value (488 kg CO2-eq ha
۱ ), indicating a carbon source. However, NT, ST, ST/PT, PT/NT and NT/ST significantly decreased the CF (
۶۲۸,
۱۳۸۲,
۲۳۲۸,
۳۰۳۸ and
۳۵۴۵ kg CO2-eq ha
۱ ), demonstrating these tillage practices served as carbon sinks. The functional unit-scaled CFs (yield-scaled CF, cost-scaled CF, production value-scaled CF and net income-scaled CF) were similar to the trend of CF, which exhibited the following order: NT/ST > PT/NT > ST/PT > ST > NT > PT. The CF and functional unit-scaled CFs of winter wheat production were significantly higher than those of spring maize production. The CF and functional unit-scaled CFs decreased as planting year increased. In addition, increasing SOC storage and grain yield were benefit for decreasing CF. The results of this study showed NT/ST rotation produced the highest grain yield and SOC storage with the lowest CF and functional unit-scaled CFs and was thus determined to be the best tillage practice for balancing sustainable production with the environment in the Loess Plateau.

Introduction

Climate change is a global issue. Greenhouse gases (GHGs) from human activities are continuously emitted into the atmosphere from industrialization, energy and agricultural activities (Linquist et al., 2012). Globally, agricultural activity-produced total non-CO2 GHG emissions comprised 10e12% of the anthropogenic emissions recorded in 2010 (Edenhofer et al., 2014). In China, GHG emissions from agricultural activities were 0.94 Gt CO2-eq$yr
۱ in 2012 (NDRC, 2016). Therefore, promoting cleaner production technology with less GHG emissions is necessary to mitigate global climate change and realize sustainable agricultural development. Carbon footprint (CF) is used to effectively evaluate the GHG emissions of a product (BSI, 2011) and have been used recently as a robust research approach to study climate change phenomena. Pishgar-Komleh et al. (2017) quantified the CF variability of tomato production in two farms in Iran. Ali et al. (2017) estimated the effect of 12 management practices on CF in Italy. Yang et al. (2014) compared the CF of five cropping systems in the North China Plain. These studies aimed to attain proper measures for reducing GHG emissions in the local crop production by comparing CF. In addition, different CF have been observed in major grain crops production. Previous studies have reported the CF of wheat production was higher than that of maize production (Huang et al., 2017; Yan et al., 2015).