Managing the trade-offs among yield, economic benefits and carbon and nitrogen footprints of wheat cropping in a semi-arid region of China.

It is critical to understand how farming practices affect the carbon and nitrogen footprints of agricultural production. Grain yield, economic return, and carbon and nitrogen footprints of spring wheat (Triticum aestivum L.) were examined under different tillage-mulch practices. Wheat was grown over 15 years (2002-2016) in the semi-arid region of the western Loess Plateau of China under six tillage-mulch practices: traditional plough with no straw mulching (T), no-till without straw mulching (NT), traditional plough with straw mulching (TS), no-till without straw mulching (NTS), traditional plough with plastic mulching (TP), no-till with plastic mulching (NTP). Average wheat yield over 15 years under NTS, NTP, TP and TS was increased by 28, 24, 22, and 13%, respectively, compared to T. Average net return was greatest under NTS and lowest under TP. The soils under all six tillage-mulch practices gained a considerably large amount of soil organic carbon (SOC) over the 15 yr. The increase in SOC in the 0-30 cm soil layer was greatest under NTS and lowest under T. When changes in soil C were included in the calculations, treatments of NT, TS, NTS, and NTP sharply reduced total greenhouse gas (GHG) emission compared to T. Compared to T, the carbon footprint was decreased by 180, 44, and 123% under NTS, NT, and TS, respectively, but was increased by 153% under TP. Compared to T, the nitrogen footprint was 24-26% lower in TP and NTP, but was not significantly different under NTS, NT, and TS. Therefore, NTS enhanced yield and net return, and reduced GHG and the carbon footprint without increasing the nitrogen footprint, and should be adopted to mitigate the environmental impacts of wheat production in the semiarid Loess Plateau.