The Structural Quality of Soil Organic Matter under Selected Soil Fertility Management Practices in the Central Highlands of Kenya

Miriam Githongo, Lucy Ngatia, Milka Kiboi, Anne Muriuki, Andreas Fliessbach, Collins Musafiri, Riqiang Fu and Felix Ngetich ()
Additional contact information
Miriam Githongo: Rosewood Futures, Nyahururu P.O. Box 2171-20300, Kenya
Lucy Ngatia: College of Agriculture & Food Sciences, Florida A&M University, Tallahassee, FL 32307, USA
Milka Kiboi: Cortile Scientific Limited, Nairobi P.O. Box 34991-00100, Kenya
Anne Muriuki: National Agriculture Research Laboratories, Kenya Agricultural and Livestock Research Organization, Nairobi P.O. Box 14733-00800, Kenya
Andreas Fliessbach: Department of Soil Sciences, Research Institute of Organic Agriculture (FIBL), Ackerstrasse 113, 5070 Frick, Switzerland
Collins Musafiri: Cortile Scientific Limited, Nairobi P.O. Box 34991-00100, Kenya
Riqiang Fu: National High Magnetic Field Laboratory, Florida State University, 1800 E. Paul Dirac Drive, Tallahassee, FL 32310, USA
Felix Ngetich: Cortile Scientific Limited, Nairobi P.O. Box 34991-00100, Kenya

Sustainability, 2023, vol. 15, issue 8, 1-13

Abstract: As influenced by agricultural practices, soil organic matter (SOM) stability is imperative in maintaining soil fertility and crop production. Integrated soil management practices have been recommended for soil fertility improvement by enhancing soil organic matter. We examined the SOM stability under integrated soil management practices for six consecutive cropping seasons in the high agricultural potential area of the Central Highlands of Kenya. The experimental design was a complete randomized block design with fourteen treatments replicated four times. The treatments were minimum (Mt) and conventional tillage (Ct) combined with sole mineral fertilizer (Mf), crop residue combined with mineral fertilizer (RMf), crop residue combined with mineral fertilizer and animal manure (RMfM), crop residue combined with animal manure and Dolichos Lablab L. intercrop (RML), crop residue combined with Tithonia diversifolia and animal manure (RTiM), and crop residue combined with Tithonia diversifolia and phosphate rock (Minjingu) (RTiP), as well as a control (no inputs). SOC was higher in treatments with organic inputs and a combination of organic and inorganic inputs. Treatments with sole mineral fertilizer and no input recorded lower SOC amounts. The C functional groups followed the sequence: alkyl C (53%) > O-alkyl C (17%) > aromatic C (9%) > carboxyl C (8%) > methoxyl C (7%) > phenolic C (6%). The alkyl C proportion was higher in organic inputs treatments, while O-alkyl C was higher in organic and inorganic fertilizer treatment combinations. Methoxyl C, aromatic C, and phenolic C proportion of SOC was greater in crop residue and mineral fertilizer combination, while carboxylic C was lower than the control in most treatments. In addition, the organic inputs treatments had a higher alkyl C/O-alkyl C ratio, increased aliphaticity, and higher hydrophobicity. Applying organic fertilizers individually or in combination with inorganic fertilizers could potentially increase C storage in the soil, thereby enhancing SOC stocks.

Keywords: 13 C CPMAS NMR; functional group; soil organic matter stability; soil inputs; soil organic carbon (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2023
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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