Organic carbon and nitrogen accumulation in orchard soil with organic fertilization and cover crop management: A global meta-analysis

In orchard systems, organic amendments and cover crops may enhance soil organic carbon (SOC) and total nitrogen (STN) stocks, but on a global scale a comprehensive understanding of these practices is needed. This study reports a worldwide meta-analysis of 131 peer-reviewed publications, to quantify potential SOC and STN accumulation in or-chard soils induced by organic fertilization and cover cropping. Annual gains of 3.73 Mg C/ha and 0.38 Mg N/ha were realized with the introduction of organic fertilizer, while cover crop management led to annual increases of 2.00 Mg C/ha and 0.20 Mg N/ha. The SOC and STN accumulation rates depended mostly on climatic conditions and initial SOC and STN content. The SOC and STN accumulated fastest during the first three years of cover crop im-plementation, at 2.98 Mg C/ha/yr and 0.25 Mg N/ha/yr and declined thereafter. Organic fertilization caused signifi-cantly more annual SOC and STN accumulation at higher (400-800 mm) than lower (< 400 mm) rainfall levels. When cover cropping for more than five years, SOC accumulated the fastest with < 800 mm of mean annual rainfall. Organic fertilization led to faster SOC accumulation with mean annual temperature between 15 and 20 degrees C than > 20 degrees C. Organic amendments led to the slowest SOC accumulation rate when the initial SOC concentration was < 10 g C/kg. This study provides policy makers and orchard managers science-based evidence to help guide adaptive management practices that build SOC stocks, improve soil conditions and enhance resilience of orchard systems to climate change.

Automated summary

This study demonstrates the potential of organic fertilization and cover cropping in enhancing soil organic carbon and total nitrogen stocks in orchard systems. Organic fertilizer can result in annual gains of 3.73 Mg C/ha and 0.38 Mg N/ha, while cover crop management can lead to annual increases of 2.00 Mg C/ha and 0.20 Mg N/ha. The rates of accumulation depend on climatic conditions and initial soil organic carbon and total nitrogen content.