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RESEARCH ARTICLE

Impact of arbuscular mycorrhizal fungi and earthworms on soil aggregate stability, glomalin, and performance of pigeonpea, Cajanus cajan

Mary N. Muchane https://orcid.org/0000-0002-7694-4863 A B E , Mirjam M. Pulleman B C , Bernard Vanlauwe D , Joyce Jefwa A and Thomas W. Kuyper B
+ Author Affiliations
- Author Affiliations

A Botany Department, National Museums of Kenya, PO Box 40658, 00100 Nairobi, Kenya.

B Soil Biology Group, Wageningen University, PO Box 47, 6700 AA Wageningen, The Netherlands.

C International Center for Tropical Agriculture (CIAT), KM17 Recta Cali-Palmira, Palmira, Colombia.

D International Institute of Tropical Agriculture (IITA), PO Box 30772, 00100 Nairobi, Kenya.

E Corresponding author. Email: mmurethi@yahoo.com; mnyawira@museums.or.ke

Soil Research 57(1) 53-65 https://doi.org/10.1071/SR18096
Submitted: 6 April 2018  Accepted: 22 October 2018   Published: 11 December 2018

Abstract

Earthworms and arbuscular mycorrhizal fungi (AMF) modify soil physical and chemical properties. However, little is known about how their interactions affect water-stable aggregation, glomalin and crop performance. A greenhouse experiment was run for 9 months to test the effects of earthworms (endogeic, Pontoscolex corethrurus; and epigeic, Dichogaster bolaui) and AMF (none, Glomus etunicatum and Scutellospora verrucosa) on water-stable aggregation, glomalin levels in aggregate size classes and crop performance. The test crop was pigeonpea (Cajanus cajan (L.) Millsp.). The soil material used for the experiment was a humic nitisol from central Kenya mixed with sand (ratio 1 : 1). Grass residue (equivalent to 20 t ha–1) was placed on top. The AMF root colonisation and external hyphal length, water-stable macroaggregates and microaggregates, total and easily-extractable glomalin in aggregate size classes, plant biomass and plant N and P uptake were measured. Earthworms were a major source of variation for soil aggregation, glomalin content and crop performance. The epigeic earthworms (D. bolaui) increased the amount of water-stable macroaggregates (by 10%) and glomalin in microaggregates and improved crop (growth and biomass) performance. The endogeic earthworms (P. corethrurus) reduced external hyphal length, root colonisation and crop performance but had no effect on water-stable aggregates and glomalin levels in in aggregate size classes. A significant AMF × earthworm interaction was observed for plant biomass and concentrations of nitrogen (N) and phosphorus (P). The AMF species together with epigeic earthworms increased plant biomass and N and P concentrations. Our results contribute to the understanding of interactions between AMF and earthworms in relation to soil aggregation, plant productivity and nutrient uptake.

Additional keywords: epigeic, endogeic, soil biota, soil fertility, soil structure, integrated soil fertility management (ISFM).


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