Conservation agriculture reduces climate change impact of a popcorn and wheat crop rotation

first of its kind. One of its main findings was that conservation agriculture had higher GHG gas emissions than conventional agriculture, due mainly to the cover crop and, to a lesser extent, to compost production and application. However, conservation agriculture sequestered much more SOC, resulting in a much smaller net climate change impact compared to conven- tional agriculture. For both systems GHG emissions consisted for approximately two-thirds of direct emissions, the remaining GHG emissions were due to fertiliser production (including compost), irrigation and field operations. Over time, the soil was a C sink in the conservation scenarios but a C source in the conven- tional scenario (Fig 3). Considering both GHG emissions and changes in SOC stock, the net climate change impact of the conservation scenarios increased over time, eventually overtaking that of the conventional scenario (Fig 5). This was due to the slightly higher GHG emissions of the conservation scenarios and the gradual decrease in the amount of SOC sequestered by the conservation scenarios and released by the conventional scenario. This illustrates that conser- vation agriculture can sequester a large amount of C until the SOC stock reaches a new equilib- rium after a few decades. It would be possible to increase C sequestration of the conservation scenario further by increasing C inputs, for instance by shifting towards more complex systems such as agrofor- estry [44]. In their review, Cardinael et al. [45] indicate that converting an arable system to a

silvo-arable system yielded mean annual C sequestration rates of 0.21, 0.28, and 1.12 t/ha in SOC, below-ground biomass, and above-ground biomass, respectively. 4.3 Effects of the conservation system on other impact categories Conventional and conservation agriculture systems differed strongly in their climate change impact, but differences for other impact categories were relatively small. Terrestrial acidifica- tion was 9% higher for conservation agriculture than for conventional agriculture. This Fig 4. Contribution of direct emissions, seed, compost, other field operations, irrigation, mineral fertilisers, pesticides and transport of inputs to the climate change impact of conservation agriculture popcorn as a function of the percentage of impact allocated to compost: 7.2% (this study), 3.6% (50% decrease), 10.8% (50% increase), and 100% (original life cycle inventory from AGRIBALYSE; Avadi (2020)). https://doi.org/10.1371/journal.pone.0285586.g004 PLOS ONE Conservation agriculture reduces climate change impact of a crop rotation PLOS ONE | https://doi.org/10.1371/journal.pone.0285586 May 23, 2023 13 / 18