Land husbandry in drought prone areasMSc 556

Seminar topic: Influence of termites on soil properties

Date: 10th April 02

Course Organiser: Mr. Paul D Smith

Franco Cube Kalisto

Introduction

•Termites are social insects which live in nests known as termitaria• termites are sometimes known as white ants• approximately 1900 living and fossil species so far known• majority are found in the tropics• the termitaria serve to house and protect the colony

• store food and maintain optimum environment• It produces a condition of homeostasis by

• self regulation of optimum conditions for development•maintenance and reproduction of the society (Emerson; 1956)

Classification of termites

• The colony of termites consists of several castes•which are morphologically distinct

• control of the proportion of the different castes is by• selective cannibalism of soldiers or • reproductive on the part of the workers

• the reproductive castes consist of • males (kings) and females (queens)

• Sterile castes are the workers and soldiers

Castes development

Soldiers develop from nymph Workers comprise the bulk of

the population Reproductive castes develop

from alates

Reproductive castes/Queen

Gravid female

Reproductive castes/Drone

Sterile castes

Are the workers and soldiers the sexual organs is suppressed

soldier

Soldiers have modified mouthparts

Larger heads and pigmented

Classification/ cont.

Termites can also be classified base on the type of nests they construct the most important types are the Colorado, the

subterranean ground nesting termites responsible for damage to constructions construct earthen tubes from the nest to food source a break in the nest would quickly be detected and

repaired by the workers

Termitarium/mound

Section through mound

Effect of termites on soil properties

Termites can affect soil properties by their burrowing and excavation when searching for food, constructing living space or

storage chambers in the soil or above the ground the burrowing and excavation activity bring much of the fine materials to

the surface and cement into concrete like material to the underlying soil arresting normal soil development processes

Soil porosity is reduced in soils without termites more silt and sand added to soils in areas where termites present

Effect of termites on soil properties/ cont. Termites play a major role in flocculation of soil organic matter

soils with low OM and low active clay content termites control soil aggregation

Form aggregates by cementing soil particles into massive structures that are extremely resistant to erosion

Termites worked materials are stable than surrounding ground mass because of the saliva added when building their structure

Soil aggregates resulting from termites activity are more stable and not easily dispersed in water compared with soil undisturbed by termites presence

The pH of mounds is higher than that of soil from which is constructed increased in pH is associated with accumulation of calcium carbonate decreased in pH is associated with high organic matter content in mounds

Effect on soil/cont

Termites activity accelerates soil erosion By removing plant cover consequently exposing the bare soil surface to

erosive forces ingest or remove organic matter which would otherwise be incorporated

into the soil and thus making the soil more susceptible Bulk density of termites modified soils is lower compare with soils not affected

by termites activity because of increased porosity or incorporation of organic matter re-packing of soil by termites also minimises soil pore spaces which

increases soil bulk density

Crusted/degraded soil

Termites activity repair the damage caused by soil degradation or crusting through excavation across crusted surfaces

Improving soil porosity and water infiltration Transport of materials to soil surface loosens the soil

This has a critical influence on soil properties enabling the soil to resist the degrading processes of soil

such as water erosion and logging Termites activity enhances the water balance of the crusted soil

by increasing infiltration amount, soil water storage and drainage

Soil macro-nutrients

Termites mounds contain more nutrients than the underlying soil mainly because of nutrient enrichment by the soil feeding capacity

to select organic particles from poor medium use of organic materials (saliva & faecal) to cement soil particles

or aggregates The enrichment in the mound affects carbon/nitrogen ratio of the internal and

external wall Due to activity of soil micro-organisms in the mound compartment

Mounds of fungus feeding species has low carbon /nitrogen ratio

Soil macro-nutrient/ cont.

However, soil feeding termites retain SOM in each fraction of their mounds SOM is protected from active mineralisation due to its distribution within

the soil fraction The SOM enrichment of the mound soil indicates that the structure is not

merely shelter Because of the ecological significant of the soil feeding termites mound

in terms of termites nutrition and SOM cycling Calcium content of mounds is higher than that of the soil from which they are

built calcium is derived from ingested plant tissues

Effects on availability of soil nutrients

Termites affect nutrient availability by transporting soil and organic matter to mounds and surrounding structures

eventually redistribution of these elements by erosion and decomposition enriches the surrounding soils

Great amount of nitrogen leaves with the colony annually in the bodies of alates when moving to establish a new colony

majority die before establishing a new colony the decomposed bodies make significant contribution to the

accession of nitrogen

Alatecarps/white ants

Water infiltration

Termites harvesting activity create dense networks of underground galleries connected to soil surface by foraging holes through which water penetrates

Infiltration capacity of foraging holes is very high as it does not limit water penetration

Rather the limiting factor to the influence of micro-pores on infiltration is the ability for micro-pore to intercept running water

Sometimes despite presence of micro-pores effect of runoff is not measured mainly because the micro-pore location is not favourable for

intercepting runoff

Influence on Infiltration

Gallery systems resulting from termites activity have profound effect on;

Soil pore space, infiltration of water into the soil, aeration and penetration of plant roots

By increasing infiltration termites increase soil water storage capacity and promotes vegetation development

Termites however, decreases the infiltration rate by reducing the amount of litter

Soil water storage, Evapo-transpiration and drainage

The influence of termites on soil enhances soil hydraulic conductivity and infiltration

because the soil structure has been modified and amount of water input by infiltration

ET rate of soil affected by termites activity is low compare with soil without attributed to improved drainage by termites activity

in deeper soil layers termites activity enhances soil water recharge water being protected from evaporation when it drains to deeper soil

layers activity of termites and mulch increases the water storage capacity of the soil

reduce runoff and increase soil water content through vegetative growth

Soil water storage

Plant production

Termites play an important role in primary production affecting growth through two main processes

improves soil structure by loosening and water infiltration enhances decomposition of surface applied organic

materials stimulating nutrient release which can be used by growing plant

Affect root growth through their influence on soil structure pore space, permeability and water logging capacity,

aggregation and stability of aggregates

Economic importance

They are abundant in tropical and subtropical environments where they help break down and recycle up to one of annual production of the dead wood

become pests when their appetite for wood and wood products extends to human homes, building materials, forests and other commercial products

in US annual losses to termites infestation are estimated at more than $ 800m consume standing forage plants that would otherwise be eaten by livestock

Economic importance/ cont

Destroy valuable pasture plants such as legumes consume dry grass and mulch resulting in increased soil moisture evaporation cemented materials from mounds of variety of species have been used for

roads and path, construction, tennis court, earth floor in buildings, bricks for construction

in Africa wet termites mound soil is used as medicine for curing chicken pox

eaten make excellent human diet and used for marriage

Control

In plantation seedlings can be protected by mechanical cultivation and using dieldrin in the planting holes

destroy the mounds and remove the queen treat soil with insecticide fumigation clearing rubbish around construction