Landscape-scale variability of soil health indicators: effects of cultivation on soil organic carbon in the Usambara Mountains of Tanzania

Leigh Winowiecki, Tor Gunnar Vågen, Boniface Massawe, Nicolas A. Jelinski, Charles Lyamchai, George Sayula, Elizabeth Msoka

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


Land-use change continues at an alarming rate in sub-Saharan Africa adversely affecting ecosystem services provided by soil. These impacts are greatly understudied, especially in biodiversity rich mountains in East Africa. The objectives of this study were to: conduct a biophysical baseline of soil and land health; assess the effects of cultivation on soil organic carbon (SOC); and develop a map of SOC at high resolution to enable farm-scale targeting of management interventions. Biophysical field surveys were conducted in a 100 km2 landscape near Lushoto, Tanzania, with composite soil samples collected from 160 sampling plots. Soil erosion prevalence was scored, trees were counted, and current and historic land use was recorded at each plot. The results of the study showed a decline in SOC as a result of cultivation, with cultivated plots (n = 105) having mean topsoil OC of 30.6 g kg−1, while semi-natural plots (n = 55) had 71 g OC kg−1 in topsoil. Cultivated areas were also less variable in SOC than semi-natural systems. Prediction models were developed for the mapping of SOC based on RapidEye remote sensing data for January 2014, with good model performance (RMSEPcal = 8.0 g kg−1; RMSEPval = 10.5 g kg−1) and a SOC map was generated for the study. Interventions will need to focus on practices that increase SOC in order to enhance productivity and resilience of the farming system, in general. The high-resolution maps can be used to spatially target interventions as well as for monitoring of changes in SOC.

Original languageEnglish (US)
Pages (from-to)263-274
Number of pages12
JournalNutrient Cycling in Agroecosystems
Issue number3
StatePublished - Jul 1 2016

Bibliographical note

Funding Information:
The fieldwork and soil analysis for the samples were funded by the CGIAR Research Program, Climate Change, Agriculture and Food Security (CCAFS). Additional data analysis efforts were made possible with funding from the International Fund for Agricultural Development (IFAD). A special thanks to Scholastica Morrison and the soil processing team in Arusha, Tanzania as well as the entire staff of the ICRAF Soil and Plant Spectroscopy Laboratory in Nairobi, Kenya. Finally, special acknowledgements are extended to Maafaka Ravelona, Phillip Kimeli, Swadakati Juma, Moses Kamau, and all of the farmers in the Lushoto district for contributing to field sampling efforts. Thank you also to the CCAFS East Africa office including James Kinyangi, John Recha, and Maren Radeny for their support. Finally, thank you to Peter Läderach, Anton Eitzinger, Jennifer Twyman, Kelvin Shikuku, Beatriz Rodriguez and Caroline Mwongera for their input.

Publisher Copyright:
© 2015, The Author(s).


  • Cropping diversity
  • Land health
  • Land-use change


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