Effects of Veld Degradation on Biomass Production in the Arable Lands of South Africa

Abstract

This paper reviews the impacts of veld degradation on species diversity, veld ecological condition. The major focus of this review is to assess the major critical factors that contributeto veld degradation. It is imperative to revitalize information on the effects of veld degradation in the South African pastoral farming systems. Current studies have indicated the limited research gaps that identify the adverse effects of veld degradation on species composition and biomass production. Grazing behavior in different grazing patterns has not been clear. Finally, this review will assist farmers, policymakers, and pastoralists to broaden their knowledge on policy development, and appropriate the veld management practices, coping measures of veld degradation, particularly those from resource-poor communities. Whereby, livestock production is the focus for food security and poverty alleviation. However, the use of legumes intercropped with temperate grass species can improve animal performance and herbage production during critical periods. The review further evaluates the veld management practices and their ability in providing adequate foliar cover with the use of the edible perennial grass plant that ensures long-term sustainable production with maximum economic returns during critical grazing seasons.

1. Introduction

Land degradation is one of the most serious global environmental issues of our time [1]. Land degradation is referred to as a major pillar that threatens most environmental issues that trigger poor land productivity, vegetation decline in most global arable lands. According to Wessels et al. [1], land degradation is defined as the persistent reduction of land’s biophysical and economic production potential or can be regarded as the long-term loss of land ecosystem functions and services. Generally, land degradation is reported as the most critical factor that triggers most global environmental issues, such as climate change [2]. Land degradation has also been reported in South Africa as one of the very common environmental problems that affect biomass production across pastures and rangelands, which often lead to soil erosion and nutrient depletion [3]. In some instances, veld degradation has been reported to have a tremendous impact on nitrogen and phosphorus inputs that can potentially have adverse effects on water resources in many parts of the world. Rangeland degradation has also been regarded as a major threat to sustainable livestock production in South Africa [4]. Approximately, 69% of agricultural land in South Africa has been reported to use extensive grazing systems, of which it is unsuitable to produce quality livestock commodities for commercial purposes [5]. However, based on the current studies, the land degradation issue has become a topical subject in many parts of the world, due to the lack of relevant information on processes that lead to veld degradation as well as ineffective programs for sustainable biomass production of livestock [3]. Concurrently, communal grazing in the areas that are commonly used in South Africa has declined in the 1990s, due to expanding human settlements, land reform dynamics, climatic changes, agricultural activities (such as crops, forestry, conservation, and mining). It is also vital in assessing the threat that veld degradation poses to people on the urban-wildland interface. Recently, it has been reported that South Africa is a drought-prone country, which is attributed to rainfall distribution that is erratic and unpredictable. According to Oluwole et al. [3], argues that very clear and detailed information on factors causing veld degradation is still limited. On the other hand, Mapiye et al. [4] reported that the low quality and quantity of feed produced during the dry season can have a negative impact on the off-takes rates; therefore, nutritional improvements are crucial in order to understand the nutritional status of the rangeland. For example, protein, energy, and minerals are the most critical nutrients for animal productivity in the semi-arid-communal production systems [4]. Generally, “veld condition” is defined as the ecological status of the veld, in terms of its botanical composition and cover, as well as its fodder value, productivity, and palatability.

2. Types of veld degradation

There are six major forms of soil and veld degradation, which were identified in South Africa. These include the loss of cover, species composition, bush encroachment, alien plant invasions and deforestation, and general category of the other [5]. However, the loss of vegetative cover and species composition are the most prominent forms of degradation, although it remains difficult to separate changes in veld condition due to environmental factors (such as in mean annual precipitation) from those due to mismanagement per se. It is argued that the change does not always equate with veld degradation, hence, the changes in species composition can occur as a consequence of natural variably, for example, the precipitation inputs [5].

However, the environmental factors and land management are clearly subjected to significantly elevated levels of soil erosion expressed, such as sheet, rill, and gully erosion.

3. Causes of veld degradation

According to Oluwole et al. [3], it is reported that the major factor that triggers land degradation in rangelands is excessive utilization often termed overgrazing. However, Mandal et al. [6] argues soil and water erosion are the most important natural resources which are major causes of land degradation. The poor farming practices as well the trend toward agricultural intensification have been considered to be a major cause of soil erosion. The prolonged soil erosion causes irreversible soil loss over time (temporal), thus, reducing the following rangeland parameter can be negatively affected (biomass production) and hydrological functions (e.g., filtering, infiltration, and water holding capacity) of soil [7]. Veld condition is determined by the following factors e.g., species composition; the vigor of palatable grass species; basal cover; soil surface condition [8]. In South Africa, bush encroachment is a common phenomenon which is problematic because it reduces the forage quality in arable lands.

The problem of Acarcia.karroo, bush encroachment is most prevalent in the arable areas. Therefore, the understanding of constraints by a communal farmer is critical because the high stocking rates are often practiced by communal farmers can adversely affect growth performance and reproductive efficiency, and ultimately affect cattle market value. Thus, Communal ownership of rangeland resources also complicates the introduction and of improved rangeland management. A.karro is commonly dominant in most arable in the false thorn veld region of the Eastern Cape in South Africa. Where in most cases is regarded as the invader. The high stocking rates observed in most communal areas have the consequence of degrading the rangelands and reducing the feed resource base for cattle [4].

This, in turn, adversely affects growth and reproductive performance, and ultimately cattle market value. Communal ownership of rangeland resources also complicates the introduction and adoption of improved rangeland management practices in the communal areas. Information on farmers’ challenges and perceptions on rangeland management, which is useful in developing sustainable communal rangeland and cattle health management practices, is still poorly understood [9].

4. Spatial heterogeneity

Spatial heterogeneity of resources, and particularly the seasonal separation of resource use, leads to distinction between equilibrium (static events) and non-equilibrium(stochastic events) [10]. Similar results obtained by Sainge et al. [11] reported that the changes in species composition, vegetation structure, and diversity across environmental and geographic gradients vegetation structure are influenced strongly by elevation [12]. Factors controlling the spatial distribution of grazing pressure may be less familiar to some ecologists [13]. Changes in spatial heterogeneity caused by grazing imply changes in habitat diversity and influence the diversity of consumers ranging from insects to birds and mammals.

Selective grazing under continuous pattern is a common grazing pattern in most arable lands that have been affected by degradation in South African pastoral farming system. The literature has reported various experiments and interesting results. Some of the findings indicate that strategies and techniques to enhance biomass production must be geared around water conservation, soil management practices, protective irrigation, and maximizing the use of fertilizers, indigenous crop varieties [14].

Equilibrium areas are referred to as those areas in which animals are in some sort of balance with their resources because of their dependence on them during the dry season. Climatic variation will cause a balance to fluctuate annually. None equilibrium areas support animals in the season of plant regrowth but the size of the animal population is not determined by these resources [15]. It is on these non-equilibrium areas that variable and periodically high defoliation intensity may be imposed because of climatic variation, causing fluctuations in the ratio of animal population size to resource abundance.

Vegetation use during the dry season range is unlikely to suffer such impacts because there is a likelihood of such vegetation being insensitive to defoliation during dry season. Vegetation cover plays important role in preventing soil cover from land degradation [3].

Together with spatial localization of herbivore impacts, due to seasonal grazing behavior and plant species, and patch-level selection, this is likely to make these environments more, and not less, prone to ecological changes [5]. Ecologists and policymakers should seek to identify the characteristics of grazing systems that predispose such systems to veld degradation, while others appear to be resistant [16].

5. Effects of animal grazing patterns on arable lands

FAO [17], indicated that the utilization-animal relationship may be described by developing the model of animal responses and production per hectare, where it can be noticed that the production per hectare rapidly declines at optimum stocking rate. However, under-grazed areas with few animals can produce a greater total production than overgrazing with more animals. Consequently, the retrogression which is referred to as the replacement of community plants of high ecological order with a community of low ecological order can result [18]. In turn, the cattle grazing pattern often changes during the dry season, which results in high mortality rates and high cull rates in smallholder farmers. In South Africa, rangelands are divided into two veld types, which are Sweetveld type and Sourveld types. Sweetveld types are generally characterized by palatable grass species and low rainfall distribution, whereas Sourveld type is characterized by unpalatable grass species with low rainfall distribution.

Invaders are also commonly found in degraded areas. Invaders are defined as the species that were absent or present in a small amount in the original vegetation, which invade the following disturbance of continued grazing overgrazing.

Invader is less productive than increasers and is of little value as regards soil and water conservation. In some instances, animals often refrain from drinking water, giving nothing in return, and livestock refuses to graze some species. Eventually, the animals are forced to graze even unpalatable species or die due to starvation, which more productive animals and leaves those unproductive and demanding animals which manage to survive, resulting in reduced economic returns.

Hoffman et al. [19], reported that keeping animals too long in a paddock results in reduced grass vigor. Not allowing a grassland sufficient time to restore the carbohydrates reserves. Increased grazing capacity results in decreased grassland productivity, decreased biodiversity, and ultimately lead to soil erosion and loss of nutrients [2].

6. Forage legumes effects on veld degraded areas

Most of the forage is available over much of the year to dairy cattle in the tropics is its low quality compared to temperate areas. It can be overemphasized that higher production can be obtained for certain grass species, for example, Paspalumdilatatum incorporated with white clover (Trifoliumrepens) [20].

However, once pastures are established, without doubt, the most critical aspect of dairy production is maintaining pastures at a level to provide sufficient quality to enable genetically high producing dairy animals to reach their genetic potential.

7. In-situ (in site) economic impact on soil loss

Different cropping, tillage, management systems often change the structurally related soil’s physical and biological properties. Compaction caused by farm implements and grazing animals increases soil bulk density and reduces infiltration rates. Furthermore, the foliar cover [18] of live plants or crop residues can reduce water runoff by reducing the impact of rainfall on bare patches, reducing the detrimental impact of rainfall, crusting, and ultimately reducing soil water evaporation [21].

8. Ex-situ (offsite) economic impact on soil

The approaches of soil conversation must be practiced with a clear understanding of the impacts of grazing forage production. The significance of the socio-economic impact of ex-situ practices on the environment should consider higher than that of in situ conservation. It is imperative that the complexities associated with biodiversity, rapid loss of biodiversity, and their realizationis increased to implement cost-effective programs, in turn, developing realistic and viable strategies and setting priorities for effective conservation and management of genetic resources will always be necessary, particularly a profound indigenous knowledge of potential benefits of indigenous forage legumes still warrant further investigation.

9. Conclusion and recommendations

It is imperative that assessment of veld condition scoring is aligned in the context of biodiversity with different approaches. Relevance of information on extension, advisory services of biomass production of veld degraded area for determining grazing capacity, stocking rates & monitoring changes in herbaceous species composition must be maintained in the optimization of livestock production. The knowledge and research still need further investigation on introduction of local adaptable, drought-tolerant, resistant forage crops that could assist farmers to diversity on feed availability and cheaply supplementation of protein in cases of nutritional deficiency in mitigating effects of veld degradation. It is recommended that veld management for decision making should be aimed at the development vegetation, adaption, and mitigation measure should then a priority in veld rehabilitation programs in areas that are prone to veld degradation. It is necessary to curb human population growth, which is the major driving force for environmental and socioeconomic problems. There is a need to take urgent actions and interventions to protect biodiversity from threats including climate change; To ensure the maintenance of biodiversity in arable lands of South Africa.