The glomalin-related soil protein content as influenced by crop rotation (spring barley monoculture/Norfolk crop rotation), straw application, and tillage

Long-term field experiments were established in 1969 at the gleyic fluvisol to assess the effects of soil management on soil organic matter and glomalin-related soil proteins. Two systems were studied: Hordeum vulgare L. monoculture (spring barley monoculture, SBM) and Norfolk crop rotation (NCR) consisting of the following crops: Trifolium or Medicago spp. (clover/alfalfa), Triticum aestivum L . (winter wheat), Zea mays L. (maize), and Hordeum vulgare L. (spring barley). Experimental factors included: i) tillage-ploughing (PL, 22 cm) vs . chiselling (CC, 12–14 cm); ii) straw management-straw removed (SR) vs . straw incorporated (SI; only in SBM); iii) soil sampling depths-0–10 cm, 10–20 cm, and 20–30 cm. Treatments were arranged as split-strip plots with four replications. Chisel cultivation enhanced total glomalin content and increased carbon in soil organic matter (C SOM ) content compared to ploughing, particularly in upper soil layers (0–20 cm) in the SBM. Straw incorporation promoted C SOM accumulation more effectively under ploughing than under chisel cultivation but had no measurable effect on the easily extractable glomalin-related soil protein content. The Norfolk crop rotation system significantly improved both C SOM levels and the glomalin-related soil protein content. These results highlight that adopting conservation-oriented soil management can improve soil structure and carbon retention, providing practical guidance for farming systems aiming to maintain long-term soil fertility