How does agro-pastoralism affect forage and soil properties in western Serengeti, Tanzania?

Pius Yoram Kavana,Bukombe John,Ephraim J Mtengeti,Anthony Sangeda,Robert Fyumagwa,Christopher Mahonge

doi:10.17138/tgft(9)120-133

Abstract

The impacts of agro-pastoral activities on soil properties, plus nutritive value and residual standing biomass of herbaceous plants in areas of different land uses in western Serengeti, were evaluated. Vegetation and soil were sampled along 4,000 m transects laid across fallow land, areas grazed only by livestock, mixed grazing (livestock and wildlife) and wildlife grazing only. A total number of 123 plant species were encountered during sampling. Analyses of soil and vegetation samples were conducted at Sokoine University of Agriculture laboratories. The estimated average density of grazing animals encountered was 160 TLU/km2 on transects within livestock-dominated grazing lands, 129 TLU/km2 for mixed grazing and 83 TLU/km2 for wildlife grazing only. Results indicated that ADF, IVDMD, IVOMD, ME and TDN in residual herbaceous forage at flowering were significantly (P<0.05) affected by land use type but CP, NDF and ADL were not affected. Soil pH, OC, CEC, C:N ratio and Ca differed significantly (P<0.05) between land use types. An overall evaluation indicated that regardless of climatic conditions, residual biomass of herbaceous plants in western Serengeti is determined by intensity of grazing, soil C:N ratio and concentrations of Ca and P in the soil. We conclude that agro-pastoral practices conducted in western Serengeti affected residual standing biomass of herbaceous plants and soil properties. We recommend that grazing pressure in communal grazing lands be reduced by either reducing number of grazing animals or duration of grazing in a particular grazing area, and specific studies be conducted to establish stocking rates appropriate for specific communal grazing lands in villages.

Highlights

Agro-pastoralism as a livelihood strategy involves some traditional and contemporary ‘best-bet’ practices such as deferred grazing, in Tanzania traditionally known as Ngitiri or Alalili, grass band cultivation, zay pit cultivation, traditionally known as Ngoro system, and controlled grazing
Average density of grazing animals observed on the various land use types was estimated as 160 tropical livestock units (TLU)/km2 on livestock-dominated grazing lands, 129 TLU/km2 on transects dominated by mixed grazing and 83 TLU/km2 on wildlife grazing areas
The negative association of Cynodon dactylon with other herbaceous plant species becomes more prominent under the influence of livestock grazing, while negative association of Dactyloctenium aegyptium with other herbaceous plant species became more prominent under the influence of mixed grazing of livestock and wildlife

Summary

Introduction

Agro-pastoralism as a livelihood strategy involves some traditional and contemporary ‘best-bet’ practices such as deferred grazing, in Tanzania traditionally known as Ngitiri or Alalili, grass band cultivation, zay pit cultivation, traditionally known as Ngoro system, and controlled grazing. Some agro-pastoral practices, such as keeping large herds of livestock within a small grazing area, exert high grazing pressure on plant species and soil (Veblen 2008), affecting species composition and abundance Other practices, such as unlimited expansion of cultivated land, affect availability of herbaceous species due to land clearing, thereby reducing the feed resource base for grazing animals. Both livestock keeping and cultivation are important for the livelihood of people in western Serengeti, so good land use planning is needed to accommodate both activities Both land clearing and cultivation disrupt stable ecosystems (Cassman and Wood 2005) and result in changes in species composition of vegetation that influence the quantity and quality of herbaceous plants available (Butt and Turner 2012). This suggests a need for careful consideration when allocating specific areas for either grazing or cropping as establishing cultivation within grazing lands might reduce availability of natural feed resources but availability of crop residues could offset the reduction

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Conclusion