Smallholder Farmers’ Practices and African Indigenous Vegetables Affect Soil Microbial Biodiversity and Enzyme Activities in Lake Naivasha Basin, Kenya

Eren Taskin,Vincenzo Tabaglio,Daniel Ndaka Sila,Clifford Obiero,Chiara Misci,Andrea Fiorini,Nic Pacini,Edoardo Puglisi,Francesca Bandini

doi:10.3390/biology10010044

Abstract

Simple SummarySmallholder farmers in Sub-Saharan Africa (SSA) are food insecure. Underexploited African indigenous vegetables (AIVs) are consumed locally without being considered a primary source of food and income. However, AIVs hold great potential for the future challenges of food security and climate change. We investigated the effects of different cropping systems and inclusion of AIVs in farming on the soil biodiversity and fertility status of smallholder farmers in Naivasha, Kenya. Compared to mainstream farming approaches, soil microorganisms under AIV cultivations differed significantly. Tillage, fertilization, soil amendments, and traditional homemade plant protection were singled out as the most important factors. The soil alteration index based on enzyme activity offered a reliable way to determine the alteration status for the first time in SSA. These findings could be useful for farmers to integrate AIVs with correct sustainable practices for a sustainable future and may contribute to the mitigation of food insecurity.Loss of soil biodiversity and fertility in Sub-Saharan Africa (SSA) may put the food security of smallholder farmers in peril. Food systems in SSA are seeing the rise of African indigenous vegetables (AIVs) that are underexploited but locally consumed without being considered a primary source of food and income. Here we present a field study, a first of its kind, in which we investigated the effects of different cropping systems and inclusion of AIVs in the farming approach on bacterial and fungal biodiversity and community structures, enzymatic activity, and the alteration status of soils of the smallholder farmers in Kenya. When compared to mainstream farming approaches, the composition and biodiversity of bacteria and fungi under AIV cultivations was significantly different. Tillage had a significant impact only on the fungal communities. Fertilization and soil amendments caused shifts in microbial communities towards specialized degraders and revealed the introduction of specific microorganisms from amendments. Traditional homemade plant protection products did not cause any disturbance to either of soil bacteria or fungi. The soil alteration index based on enzyme activity successfully differentiated the alteration status for the first time in SSA. These findings could be useful for farmers to integrate AIVs with correct sustainable practices for a sustainable future.

Highlights

Food production and ecosystem services provision in Sub-Saharan Africa (SSA) are closely connected to soil fertility
Our findings indicate that a farming approach in which African indigenous vegetables (AIVs) were rotated with maize and bean intercropping and coupled with moderate use of soil fertilization/amendment was found to be better at increasing soil biodiversity and soil status
Our findings confirmed our hypothesis that farming practices together with AIVs have an impact on soil fertility through the soil microbial community, enzymes, and soil properties, as indicated especially by the results from the fields in which AIVs were integrated with maize and bean intercropping in rotations

Summary

Introduction

Food production and ecosystem services provision in Sub-Saharan Africa (SSA) are closely connected to soil fertility. For smallholder farmers, whose living conditions depend on the quality and quantity of resources obtained from agricultural land, soil fertility loss represents a critical issue [1] by acting as a chronic poverty trap threatening their food security [2,3]. In the last few decades, maize-based farming systems have had a critical role in supporting food security in SSA. Smallholder farmers have yield gaps and severe production constraints in maize-based farming systems without the seeds of improved varieties of maize, adequate inputs, and soil fertility management practices [11]. The future of food systems, especially that of smallholder farmers in SSA, may benefit from the diffusion of African indigenous vegetables (AIVs), which are underexploited but often widespread and consumed in local communities without being considered staple crops [12,13]. Leafy AIVs such as amaranth and spider plant have the advantage of having a relatively short growth cycle (ready for harvest in a month or less) compared to staples such as maize [15,16] and were shown to be good candidate crops for stress conditions [17,18]

Objectives

Methods

Results

Discussion

Conclusion