Fungal-fermented corn straw as an organic amendment: balancing tomato nutrition, soil functions and antibiotic resistance.

Abstract

<h4>Introduction</h4>Tomato growers need strategies that improve fruit nutritional quality and soil health while reducing dependence on synthetic fertilizers and wasting less crop straw. Fungal-fermented straw products (FSP) are a candidate amendment, but their suitable application rate, placement depth and side effects on soil microbes and antibiotic resistance genes (ARGs) remain unclear.<h4>Methods</h4>An FSP was produced from corn straw via solid-state fermentation for 30 d using <i>Auricularia cornea</i> cv. Yumuer. A single-season greenhouse pot experiment was conducted with an unamended control (no FSP) and six FSP treatments combining different rates (0.5-5% w/w) and soil incorporation depths (3 and 10 cm). Measurements included tomato yield (growth and fruit yield), fruit quality, soil health, biochemical responses, and molecular responses.<h4>Results</h4>FSP at 2% (w/w) incorporated to 10 cm increased yield by about 30% and raised fruit lycopene and vitamin C by 20-40% compared with the control. It also enhanced soil organic carbon, available P and K, humic substances and key enzymes, and shifted microbes toward decomposers and plant-beneficial taxa (e.g., <i>Streptomyces</i>, <i>Sphingomonas</i>, <i>Nocardioides</i>, and <i>Arthrobacter</i>). A high surface dose (5% at 3 cm) increased total ARGs, whereas 2% at 10 cm achieved quality and soil benefits with ARG levels comparable to or lower than the control.<h4>Discussion</h4>These results suggest a practical application pattern that balances agronomic benefits with ARG-related risk for recycling crop residues in intensive tomato systems.