Tillage and haymaking practices speed up belowground net productivity restoration in the degraded Songnen grassland

- Tillage and hay making practices can enhance BNPP and belowground C allocation.
- On average, fBNPP ranged from 0.25 to 0.54.
- Tillage and hay making practices are the feasible management practices.

The improvement of productivity and soil organic matter is a central issue for the restoration of degraded land. Belowground net primary productivity (BNPP) is a major source of soil organic matter. Therefore, understanding BNPP dynamics is crucial to improving our knowledge of belowground C allocation and storage in grasslands. However, how tillage and haymaking practices affect BNPP and belowground C allocation remains poorly understood. To investigate effects of tillage and haymaking practices on BNPP and root fraction (fBNPP), a field experiment set within three fenced areas, one each for maize cultivation, artificial grassland, and natural grassland, was carried out during 2012-2014. The treatments were: maize tillage; maize no-tillage, keeping residues; maize no-tillage, removing residues; artificial grassland, no haymaking; artificial grassland, haymaking; natural grassland, no haymaking; and natural grassland, haymaking. The ingrowth donuts method was used to determine BNPP. Across the years, BNPP varied from 220 to 1331 g m−2. Tillage and haymaking practices significantly increased BNPP and fBNPP in maize cultivation and grassland managements, respectively, suggesting that more C is allocated to soil with BNPP in those land-use practices. On average, fBNPP ranged from 0.25 to 0.54 and was significantly higher in 2014 than in 2012 and 2013, irrespective of the practices, indicating that precipitation is the controlling factor for determining C allocation between belowground and aboveground. Our findings highlight that tillage and haymaking practices can enhance BNPP and belowground C allocation. Therefore, from the perspective of the whole plant, they should be considered as feasible management practices for restoration of degraded grassland.