Soil Degradation-Induced Decline in Productivity of Sub-Saharan African Soils: The Prospects of Looking Downwards the Lowlands with the Sawah Ecotechnology

Table 1

Erosion-productivity relationship for soils of Sub-Saharan Africa (desurfacing experiments).

Soil loss (cm)	Yield reduction (%)	Soil order	Climate/location	Country	Source
Maize (Zea mays L.) as a test crop
2.5, 5, 7.5, 10, 12.5	23, 38, 49, 53, 56	Alfisol	Subhumid Ibadan	Nigeria	[19]
5, 10, 20	72.5, 82.6, 99.5	Alfisol	Subhumid Ilora	Nigeria	[40]
5, 10, 20	30.5, 73.6, 93.5	Alfisol	Subhumid Ikenne	Nigeria	[40]
5, 10, 20	95.4, 95.4, 100	Ultisol	Humid Onne	Nigeria	[40]
5	54.9	Alfisol	Subhumid Ilora	Nigeria	[36]
5	30	Alfisol	Subhumid Ikenne	Nigeria	[36]
5	15	Inceptisol	Subhumid Nsukka	Nigeria	[36]
5	69.7	Ultisol	Humid Onne	Nigeria	[36]
5	64.2	Ultisol	Subhumid Nsukka	Nigeria	[36]
10, 20	39.2, 81.7	Alfisol	Subhumid Ibadan	Nigeria	[14]
2.5, 7.5	50, ≫100	Ultisol	Humid Douala	Cameroon	[14]
5, 10, 20	47, 48, 63	Lateritic Alfisol	Semiarid Ouagadougou	Burkina Faso	[14]
3, 6	23, 55	Ultisol	Subhumid Nsukka (1)	Nigeria	[3]
3, 6	50, 95	Ultisol	Subhumid Nsukka (2)	Nigeria	[3]
5, 10, 15, 20	56.0, 82.5, 90.0, 95.5	Oxisol	Subhumid Ile-Ife	Nigeria	[27]
15, 25	17, 67 (upper slope); 65, 76 (lower slope)	Gravelly Alfisol	Subhumid Ibadan	Nigeria	[29]
Cowpea (Vigna unguiculata L.) as a test crop
5, 10, 20	42.6, 33.1, 80.5	Alfisol	Subhumid Ilora	Nigeria	[40]
5, 10, 20	1.5, 59.1, 65.1	Alfisol	Subhumid Ikenne	Nigeria	[40]
5, 10, 20	62.0, 70.6, 68.3	Ultisol	Humid Onne	Nigeria	[40]
Cassava (Manihot esculentus C.) as a test crop
10, 20	35.7, 53.7	Alfisol	Subhumid Ibadan	Nigeria	[40]

Quantification was achieved where both the depth of soil loss and the yield reduction were given by the authors or could be calculated from the information they presented.