Land degradation impact on soil organic carbon and nitrogen stocks of sub-tropical humid grasslands in South Africa

Dlamini, Phesheya; Chivenge, Pauline; Manson, A. D.; Chaplot, Vincent

doi:10.1016/j.geoderma.2014.07.016

Cited by 128 publications

(88 citation statements)

References 49 publications

(57 reference statements)

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“…There also exists a strong relationship between vegetation cover and the SOC pool, such that excessive reductions in vegetation cover exacerbates risks of soil degradation and SOC depletion. A study conducted in the sub-tropical humid grasslands in South Africa indicated that the decline in grass (vegetative) cover from 100% to 0%-5% reduced the SOC pool by 1.25 kg/m 2 and the soil organic N (SON) pool by 0.074 kg/m 2 [20], There were also attendant declines in the C:N ratio and proportion of SOC and SON in the silt + clay fraction with the decline in aerial grass cover which negatively affected ecosystem functions of the acidic sandy loam soils. Similarly, transformation of a thicket vegetation to an open savanna (dominated by grasses) due to intensive grazing decreased soil quality in the Eastern Cape region of South Africa [21].…”

Section: Soil Organic Carbon and Its Impact On Soil Qualitymentioning

confidence: 99%

Restoring Soil Quality to Mitigate Soil Degradation

2015

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Abstract:Feeding the world population, 7.3 billion in 2015 and projected to increase to 9.5 billion by 2050, necessitates an increase in agricultural production of ~70% between 2005 and 2050. Soil degradation, characterized by decline in quality and decrease in ecosystem goods and services, is a major constraint to achieving the required increase in agricultural production. Soil is a non-renewable resource on human time scales with its vulnerability to degradation depending on complex interactions between processes, factors and causes occurring at a range of spatial and temporal scales. Among the major soil degradation processes are accelerated erosion, depletion of the soil organic carbon (SOC) pool and loss in biodiversity, loss of soil fertility and elemental imbalance, acidification and salinization. Soil degradation trends can be reversed by conversion to a restorative land use and adoption of recommended management practices. The strategy is to minimize soil erosion, create positive SOC and N budgets, enhance activity and species diversity of soil biota (micro, meso, and macro), and improve structural stability and pore geometry. Improving soil quality (i.e., increasing SOC pool, improving soil structure, enhancing soil fertility) can reduce risks of soil degradation (physical, chemical, biological and ecological) while improving the environment. Increasing the SOC pool to above the critical level (10 to 15 g/kg) is essential to set-in-motion the restorative trends. Site-specific techniques of restoring soil quality include conservation agriculture, integrated nutrient management, continuous vegetative cover such as residue mulch and cover cropping, and controlled grazing at appropriate stocking rates. The strategy is to produce "more from less" by reducing losses and increasing soil, water, and nutrient use efficiency.

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Section: Soil Organic Carbon and Its Impact On Soil Qualitymentioning

confidence: 99%

Restoring Soil Quality to Mitigate Soil Degradation

2015

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“…2) suggested that even in the same irrigation scheme, leaching of salts may vary spatially, both laterally and longitudinally. Assessment of the extent and severity of soil salinity in irrigated lands should therefore be treated as other soil factors with spatial variation characteristics, e.g., Carborn stocks (Dlamini et al 2014). However, considering that reversing salinized soils is almost impractical especially in developing countries, timely and cost effective methods such as use of GIS and remote sensing to monitor soil salinity, while at the same time monitoring the spatial variation of soil salinity both in time and space may need to be explored, especially in irrigation schemes with intercropping systems.…”

Section: Soil Salinity Spatial Variationmentioning

confidence: 99%

Matching soil salinization and cropping systems in communally managed irrigation schemes

Malota

Mchenga

2018

Appl Water Sci

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Occurrence of soil salinization in irrigation schemes can be a good indicator to introduce high salt tolerant crops in irrigation schemes. This study assessed the level of soil salinization in a communally managed 233 ha Nkhate irrigation scheme in the Lower Shire Valley region of Malawi. Soil samples were collected within the 0-0.4 m soil depth from eight randomly selected irrigation blocks. Irrigation water samples were also collected from five randomly selected locations along the Nkhate River which supplies irrigation water to the scheme. Salinity of both the soil and the irrigation water samples was determined using an electrical conductivity (EC) meter. Analysis of the results indicated that even for very low salinity tolerant crops (EC i < 2 dS/m), the irrigation water was suitable for irrigation purposes. However, root-zone soil salinity profiles depicted that leaching of salts was not adequate and that the leaching requirement for the scheme needs to be relooked and always be adhered to during irrigation operation. The study concluded that the crop system at the scheme needs to be adjusted to match with prevailing soil and irrigation water salinity levels.

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“…It is known that soil spectral properties are difficult to depict using satellite data during grass growing season; the relative abundance of decreaser and increaser grass species could therefore be used as indicator of soil fertility. In a recent study in South Africa, Dlamini et al (2014) found that land degradation, defined as a reduction in aerial grass cover, impacted significantly on soil N and OC stocks of grassland. Future studies should model areas that might be infested by H. hirta using parameters associated with this species and geospatial modellers.…”

Section: Geocartomentioning

confidence: 99%

“…The differences in these vegetation physiological and morphological properties could therefore result in different vegetation spectral features (Lillesand & Kiefer 2001;Kumar et al 2001). Moreover, grassland degradation could be a result of degraded soil conditions (Dlamini et al 2014). It is known that during the growing season, soil spectral properties are masked out by vegetation cover.…”

Section: Introductionmentioning

confidence: 99%

Multispectral remote sensing for mapping grassland degradation using the key indicators of grass species and edaphic factors

Mansour

Mutanga

Adam

et al. 2015

Geocarto International

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Land degradation is believed to be one of the most severe and widespread environmental problems. In South Africa, large areas of land have been identified as degraded, as shown by the lower vegetation cover. One of the major causes of grassland degradation is change in plant species composition that leads to presence of unpalatable grass species. Some grass species have been successfully used as indicators of different levels of grassland degradation in the country. This paper, therefore explores the possibility of mapping grassland degradation in Cathedral Peak, South Africa, using indicators of grass species and edaphic factors. Multispectral SPOT 5 data were used to produce a grassland degradation map based on the spatial distribution of decreaser (Themeda triandra) and increaser (Hyparrhenia hirta) species. To improve mapping accuracy, soil samples were collected from each species site and analysed for nutrient content. A t-test and machine learning random forest classification algorithm were applied for variable selection and classification using SPOT 5 data and edaphic variables. Results indicated that the decreaser and increaser grass species can be mapped with modest accuracy using SPOT 5 data (overall accuracy of 75.30%, quantity disagreement = 2 and allocation disagreement = 23). The classification accuracy was improved to 88.60%, 1 and 11 for overall accuracy, quantity and allocation disagreements, respectively, when SPOT 5 bands and edaphic factors were combined. The study demonstrated that an approach based on the integration of multispectral data and edaphic variables, which increased the overall classification accuracy by about 13%, is a suitable when adopting remote sensing to monitor grassland degradation.

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Land degradation impact on soil organic carbon and nitrogen stocks of sub-tropical humid grasslands in South Africa

Cited by 128 publications

References 49 publications

Restoring Soil Quality to Mitigate Soil Degradation

Restoring Soil Quality to Mitigate Soil Degradation

Matching soil salinization and cropping systems in communally managed irrigation schemes

Multispectral remote sensing for mapping grassland degradation using the key indicators of grass species and edaphic factors

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