Nano-iron and AM fungi inoculation in dryland wheat field: A sustainable alternative to plastic film mulching

Plastic film mulching is a primary cultivation measure in the dryland agricultural areas of northwest China, but comes with the drawback of plastic pollution. To overcome this issue, the biological inoculants such as arbuscular mycorrhizal (AM) with nanotechnology might be a critical pathway, but their positive effects on plants are context-dependent and vary with species, application method, concentration, size, surface charge, and other physio-chemical properties. There is so far limited information available on the combined effects of AM fungi with nanoparticles in agriculture. This study aimed to investigate the potential of iron nanoparticles (FeNPs) in combination with AMF regarding wheat productivity maintenance and its driving mechanism. Herein, we used a completely randomized block design for the field experiments in the years 2018 and 2019. We conducted two field experiments using nanopriming of seeds with iron nanoparticles (FeNPs) and AMF in two growing seasons in 2018 and 2019 on wheat (Triticum aestivum L., cv. Longchun29) in the field. Each plot had a 5 m × 5 m total area having 6 rows of 0.2 m spacing and 0.5 m buffer strip among the neighboring plots. There were 8 treatments in the field experiment, and each treatment was repeated 3 times, including four nano iron concentration seed soaking treatments (0 mg L-1, 5 mg L-1, 10 mg L-1, 15 mg L-1) and two inoculation treatments of arbuscular mycorrhizal fungi (inoculated with Gi and non-inoculated). Combined treatments with arbuscular mycorrhizal fungi and iron nanoparticles led to significant increases in wheat biomass and yield across 2018 and 2019. When compared with control treatment there was an increase of 111% in biomass for the year 2018 and a 102% increase was observed for the year 2019; while the increase in the yield percent when compared to control was 91% in 2018 and 85% in 2019 respectively. Water use efficiency for yield (WUE) increased by 92% in 2018 and 57% in 2019. The colonization rate of AMF + FeNPs 10 mg L-1 treatment increased by 223%, 88%, and 211%, respectively compared with control at the jointing, anthesis, and maturity stage in 2018; and increased by 48%, 37%, and 56% respectively in the year 2019. FeNPs at 10 mg L-1 led to small increases in total organic carbon (TOC), total nitrogen (TN), microbial biomass carbon and nitrogen (MBC), and (MBN), in both growing seasons, and AMF inoculation further significantly increased these carbon fractions by 2.6%, 20%, 21% and 2