Energy balances and SOC and N stocks as affected by organic amendments and inorganic N fertilization in a semi-arid environment (IOSDV-Madrid)
A long-term field experiment (1984-2011), was conducted on a Calcic Haploxeralf from semi-arid central Spain to evaluate the combined effect of three treatments: farmyard manure (FYM), straw and control without organic amendments (WOA) and five increasing rates of mineral N on: (1) some energetic parameters of crop production, and (2) the effect of the different treatments on soil organic carbon (SOC) and total N stocks. Crop rotation included spring barley, wheat and sorghum. The energy balance variables considered were net energy produced (energy output minus energy input), the energy output/input ratio and energy productivity (crop yield per unit energy input). Results showed small differences between treatments. Total energy inputs varied from 9.86 GJ ha-1 year-1 (WOA) to 11.14 GJ ha-1 year-1 in the FYM system. For the three crops, total energy inputs increased with increasing rates of mineral N. Energy output was slightly lower in the WOA (33.40 GJ ha-1 year-1) than in the two organic systems (37.34 and 34.96 GJ ha-1 year-1 for FYM and straw respectively). Net energy followed a similar trend. At the end of the 27-year period, the stocks of SOC and total N had increased noticeably in the soil profile (0-30 cm) as a result of application of the two organic amendments. Most important SOC changes occurred in the FYM plots, with mean increases in the 0-10 cm depth, amounting an average of 9.9 Mg C ha-1 (667 kg C ha-1 year-1). Increases in N stocks in the top layer were similar under FYM and straw and ranged from 0.94 to 1.55 Mg N ha-1. By contrast, simultaneous addition of increasing rates of mineral N showed no significant effect on SOC and total N storage.
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| Format: | artículo biblioteca |
| Published: |
Taylor & Francis
2013
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| Subjects: | Carbon, Energy analysis, Nitrogen fertilization, Organic amendments, Semi-arid conditions, |
| Online Access: | http://hdl.handle.net/10261/244496 http://dx.doi.org/10.13039/501100007273 http://dx.doi.org/10.13039/501100011698 |
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