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Pedotransfer functions: an answer to the lack of hydrophysical soil properties for sustainable land management in the South-Western part of the Congo Basin

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Abstract
The south-western part of the Congo Basin (i.e., Lower Congo) has been an active research area in the field of soil sciences since the 1940s. This resulted in a comprehensive soil database, completed with climatological and agricultural data, for this region. However, information on hydraulic and physical properties such as the soil water retention curve (SWRC) and bulk density (BD) of soils is still missing. Reliable data on the SWRC are necessary for simulating the soil water balance and estimating crop yields under various management scenarios that are subjected to different rainfall regimes. The crop cycle of common crops in the Lower Congo can be fitted into the growing period taking into account climate-, soil- and crop-specific sowing dates and as such avoiding water stress conditions. Data on BD are needed for estimation of carbon stocks and nutrient status of soils. Measuring these hydrophysical properties is labour-intensive, time-consuming, expensive and causes additional difficulties in developing countries, like the DR Congo, ranging from staff training to the acquisition of the necessary equipment. Hydropedology, a recent discipline which bridges hydrology and pedology, has tried to circumvent this problem by the application of pedotransfer functions (PTFs). These are empirical relationships relating the soil hydraulic parameters to more easily measurable soil data such as soil texture, BD, organic matter content and/or other data routinely measured in soil surveys. Yet, most published PTFs have been developed for soils in the temperate areas and less effort has been dedicated to develop PTFs valid for soils of the humid tropics. The most-widely published PTFs have been evaluated based on water-retention measurements of several representative soils of the Lower Congo. Results showed that there is not one single set of PTFs valid for application to the soils of this region. This preliminary study recommended developing PTFs for estimating hydrophysical properties such as the SWRC and BD designed for the Lower Congo region. This will allow full exploitation of the available natural resources data. We tested various state-of-the-art approaches (e.g., multiple linear regressions, k-nearest neighbour and the pore-solid fractal theory) for developing such PTFs. These functions were then used to construct a preliminary map of hydraulic information for soils of the Lower Congo. This map, combined with the soil and terrain (SOTER) database for DR Congo, will help to define guidelines for the optimisation of agricultural production and environmental protection at different spatial scales.
Keywords
Soil Water Retention, K-nearest Neighbour, Soils of the Humid Tropics, Lower Congo, Pedotransfer Functions

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Chicago
Botula Manyala, Yves-Dady, Geert Baert, Attila Nemes, Jan Baetens, Paul Mafuka, Ann Verdoodt, Eric Van Ranst, and Wim Cornelis. 2013. “Pedotransfer Functions: An Answer to the Lack of Hydrophysical Soil Properties for Sustainable Land Management in the South-Western Part of the Congo Basin.” In Nutrition and Food Production in the Congo Basin, 53–54. Brussels, Belgium: Royal Academy for Overseas Sciences.
APA
Botula Manyala, Yves-Dady, Baert, G., Nemes, A., Baetens, J., Mafuka, P., Verdoodt, A., Van Ranst, E., et al. (2013). Pedotransfer functions: an answer to the lack of hydrophysical soil properties for sustainable land management in the South-Western part of the Congo Basin. Nutrition and food production in the Congo Basin (pp. 53–54). Presented at the International conference on Nutrition and Food Production in the Congo Basin, Brussels, Belgium: Royal Academy for Overseas Sciences.
Vancouver
1.
Botula Manyala Y-D, Baert G, Nemes A, Baetens J, Mafuka P, Verdoodt A, et al. Pedotransfer functions: an answer to the lack of hydrophysical soil properties for sustainable land management in the South-Western part of the Congo Basin. Nutrition and food production in the Congo Basin. Brussels, Belgium: Royal Academy for Overseas Sciences; 2013. p. 53–4.
MLA
Botula Manyala, Yves-Dady, Geert Baert, Attila Nemes, et al. “Pedotransfer Functions: An Answer to the Lack of Hydrophysical Soil Properties for Sustainable Land Management in the South-Western Part of the Congo Basin.” Nutrition and Food Production in the Congo Basin. Brussels, Belgium: Royal Academy for Overseas Sciences, 2013. 53–54. Print.
@inproceedings{4159804,
  abstract     = {The south-western part of the Congo Basin (i.e., Lower Congo) has been an active research area in the field of soil sciences since the 1940s. This resulted in a comprehensive soil database, completed with climatological and agricultural data, for this region. However, information on hydraulic and physical properties such as the soil water retention curve (SWRC) and bulk density (BD) of soils is still missing. Reliable data on the SWRC are necessary for simulating the soil water balance and estimating crop yields under various management scenarios that are subjected to different rainfall regimes. The crop cycle of common crops in the Lower Congo can be fitted into the growing period taking into account climate-, soil- and crop-specific sowing dates and as such avoiding water stress conditions. Data on BD are needed for estimation of carbon stocks and nutrient status of soils. Measuring these hydrophysical properties is labour-intensive, time-consuming, expensive and causes additional difficulties in developing countries, like the DR Congo, ranging from staff training to the acquisition of the necessary equipment. Hydropedology, a recent discipline which bridges hydrology and pedology, has tried to circumvent this problem by the application of pedotransfer functions (PTFs). These are empirical relationships relating the soil hydraulic parameters to more easily measurable soil data such as soil texture, BD, organic matter content and/or other data routinely measured in soil surveys. Yet, most published PTFs have been developed for soils in the temperate areas and less effort has been dedicated to develop PTFs valid for soils of the humid tropics. The most-widely
published PTFs have been evaluated based on water-retention measurements of several representative soils of the Lower Congo. Results showed that there is not one single set of PTFs valid for application to the soils of this region. This preliminary study recommended developing PTFs for estimating hydrophysical properties such as the SWRC and BD designed for the Lower Congo region. This will allow full exploitation of the available natural resources data. We tested various state-of-the-art approaches (e.g., multiple linear regressions, k-nearest neighbour and the pore-solid fractal theory) for developing such PTFs. These functions were then used to construct a preliminary map of hydraulic information for soils of the Lower Congo. This map, combined with the soil and terrain (SOTER) database for DR Congo, will help to define guidelines for the optimisation of agricultural production and environmental protection at different spatial scales.},
  author       = {Botula Manyala, Yves-Dady and Baert, Geert and Nemes, Attila and Baetens, Jan and Mafuka, Paul and Verdoodt, Ann and Van Ranst, Eric and Cornelis, Wim},
  booktitle    = {Nutrition and food production in the Congo Basin},
  keyword      = {Soil Water Retention,K-nearest Neighbour,Soils of the Humid Tropics,Lower Congo,Pedotransfer Functions},
  language     = {eng},
  location     = {Brussels, Belgium},
  pages        = {53--54},
  publisher    = {Royal Academy for Overseas Sciences},
  title        = {Pedotransfer functions: an answer to the lack of hydrophysical soil properties for sustainable land management in the South-Western part of the Congo Basin},
  year         = {2013},
}