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. 2017 Sep 6;7(1):10738.
doi: 10.1038/s41598-017-10718-y.

Effects of biochar, waste water irrigation and fertilization on soil properties in West African urban agriculture

Volker Häring  1 , Delphine Manka'abusi  2 , Edmund K Akoto-Danso  2 , Steffen Werner  3 , Kofi Atiah  3 , Christoph Steiner  2 , Désiré J P Lompo  2 , Samuel Adiku  4 , Andreas Buerkert  2 , Bernd Marschner  3
Affiliations

Effects of biochar, waste water irrigation and fertilization on soil properties in West African urban agriculture

Volker Häring et al. Sci Rep. .

Erratum in

Abstract

In large areas of sub-Saharan Africa crop production must cope with low soil fertility. To increase soil fertility, the application of biochar (charred biomass) has been suggested. In urban areas, untreated waste water is widely used for irrigation because it is a nutrient-rich year-round water source. Uncertainty exists regarding the interactions between soil properties, biochar, waste water and fertilization over time. The aims of this study were to determine these interactions in two typical sandy, soil organic carbon (SOC) and nutrient depleted soils under urban vegetable production in Tamale (Ghana) and Ouagadougou (Burkina Faso) over two years. The addition of biochar at 2 kg m-2 made from rice husks and corn cobs initially doubled SOC stocks but SOC losses of 35% occurred thereafter. Both biochar types had no effect on soil pH, phosphorous availability and effective cation exchange capacity (CEC) but rice husk biochar retained nitrogen (N). Irrigation with domestic waste water increased soil pH and exchangeable sodium over time. Inorganic fertilization alone acidified soils, increased available phosphorous and decreased base saturation. Organic fertilization increased SOC, N and CEC. The results from both locations demonstrate that the effects of biochar and waste water were less pronounced than reported elsewhere.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Figure 1
Figure 1
Changes of soil organic carbon stocks over time at 0–20 cm depth for Tamale (a) and Ouagadougou (b). Means were calculated irrespective of irrigation water quantity and quality levels because they had no significant effects on SOC stocks (means ± sd; n = 16). Values after biochar additions (between 0 and 0.5 years) are calculated and have no standard deviation.
Figure 2
Figure 2
Cumulative DOC leaching of rice husk and corn cob biochar relative to control (100%) measured over 12 days with continuous drip wise waste water irrigation (J. Werner, unpublished).
Figure 3
Figure 3
CO2 evolution measured over 60 days in a laboratory incubation of soil amended with rice husk and corn cob biochar at various application rates (A. Neuser, unpublished).
Figure 4
Figure 4
Changes of total N stocks over time at 0–20 cm depth for Tamale (a) and Ouagadougou (b). Means were calculated irrespective of irrigation water quantity and quality levels because they had no significant effects on N stocks (means ± sd; n = 16). Values after biochar additions (between 0 and 0.5 years) are calculated and have no standard deviation.
Figure 5
Figure 5
C/N ratio changes over time at 0–20 cm depth for Tamale (a) and Ouagadougou (b). Means were calculated irrespective of irrigation water quantity and quality levels because they had no significant effects on C/N ratios (means ± sd; n = 16). Values after biochar additions (between 0 and 0.5 years) are calculated and have no standard deviation.
Figure 6
Figure 6
Soil pH changes over time at 0–20 cm depth grouped by irrigation quality and quantity levels for Tamale and Ouagadougou (means ± sd; n = 4).
Figure 7
Figure 7
Changes of available P (Bray) over time at 0–20 cm depth under full irrigation for Tamale (a) and Ouagadougou (b). Means were calculated irrespective of irrigation water quality levels because they had no significant effects on available P (means ± sd; n = 8).
Figure 8
Figure 8
Changes of effective cation exchange capacity (CEC) over time at 0–20 cm depth under full irrigation for Tamale (a) and Ouagadougou (b). Means were calculated irrespective of irrigation water quality levels because they had no significant effects on CEC (means ± sd; n = 8).
Figure 9
Figure 9
Changes of effective base saturation (BS) over time at 0–20 cm depth under full irrigation for Tamale (a) and Ouagadougou (b). Means were calculated irrespective of irrigation water quality levels because they had no significant effects on BS (means ± sd; n = 8).
Figure 10
Figure 10
Changes of exchangeable sodium percentage (ESP) over time at 0–20 cm depth under full irrigation with clean water (a) and waste water (b) for Tamale as well as clean water (c) and waste water (d) for Ouagadougou (means ± sd; n = 4).
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References

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