Five-year impacts of biomass crop monoculture on soil enzyme activity, nitrogen pools, and other soil health indicators

Soil health and nitrogen cycling are critical for sustainable biomass production, yet the long-term effects of monoculture biomass cropping on these factors remain underexplored. This study examines the five-year monoculture cultivation effects of giant reed ( Arundo donax L.), miscanthus ( Miscanthus x giganteus ), and sida ( Sida hermaphrodita ) on soil biochemical properties, nitrogen species, and biomass yield stability under field conditions. Soil samples collected in autumn 2014 and spring 2015 revealed significant seasonal and crop-specific impacts on soil health indicators. Giant reed cultivation resulted in the highest urease activity in autumn (346 μg NH 4 + g −1 soil h −1 ), supporting enhanced nitrogen cycling, while miscanthus increased soil organic matter (SOM) to 4.77 % in spring, aiding carbon sequestration. Sida contributed to the highest dehydrogenase activity, indicating robust microbial activity, alongside increased organic nitrogen (4.92 mg kg −1 ) and total nitrogen levels (17.0 mg kg −1 ) in spring. Soil respiration and electrical conductivity varied by season, with pH values slightly higher in spring. Across all crops, nitrogen forms (nitrate, ammonium, and organic nitrogen) were generally higher in spring than autumn, highlighting seasonal dynamics. Yield stability was greatest in giant reed (2.01 kg m −2 on average), while miscanthus and sida averaged 1.62 and 0.86 kg m −2 , respectively. The findings underscore these crops' potential for sustainable biomass production and improved soil health in low-input systems. • Enzyme activities revealed seasonal variations under different biomass crops. • Miscanthus promoted spring phosphatase activity, enhancing phosphorus availability. • Sida resulted in the highest organic and total nitrogen levels. • Giant reed exhibited the highest urease activity, supporting enhanced N cycling. • Miscanthus contributed the most to SOM, aiding carbon sequestration.