Review of existing knowledge on soil crusting in South Africa

Laker, M. C.; Nortjé, Gerhardus Petrus

doi:10.1016/bs.agron.2019.01.002

Cited by 33 publications

(35 citation statements)

References 46 publications

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“…Within plot improvements in soil infiltration capacity to reduce overland flow generation (Kuyah et al, 2019; Nishigaki, Sugihara, Kilasara, & Funakawa, 2017) is key as is the improvement of and aggregate stability, for example, with an amendment by organic matter, to reduce risk of soil capping/crusting (Laker & Nortjé, 2019; Smith, Strauss, & Hardie, 2019) and improve overall soil health (Belayneh, Yirgu, & Tsegaye, 2019; Mesfin et al, 2018). While such within‐plot actions can be locally beneficial, analysis in this study has shown that different agricultural plot terraces on the same slope are chained to each other.…”

Section: Discussionmentioning

confidence: 99%

Integrating land‐water‐people connectivity concepts across disciplines for co‐design of soil erosion solutions

et al. 2020

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Soil resources in East Africa are being rapidly depleted by erosion, threatening food, water and livelihood security in the region. Here we demonstrate how the integration of evidence from natural and social sciences has supported a community-led change in land management in an agro-pastoral community in northern Tanzania. Geospatial analysis of erosion risk and extent (based on a drone survey across a 3.6 km 2 sub-catchment) revealed that recently converted land had ca 12-times greater rill density than established slow-forming terraced plots (987 ± 840 m 2 ha −1 vs. 79 ± 110 m 2 ha −1 ). Slope length and connectivity between plots were key factors in the development of rill networks rather than slope per se wherein slope length was augmented by weak boundaries between newly formed plots. Erosion evidence, supported by communication of 'process' and 'structural' hydrological connectivity, was integrated with local environmental knowledge within participatory community workshops. Demonstration of the critical time window of hillslope-scale rill erosion risk during early phases of slow-forming terrace development catalysed a community-led tree planting and grass seed sowing programme to mitigate soil erosion by water. This was grounded in an implicit farmer understanding of the need for effective governance mechanisms at both community and District levels, to enable community-led actions to be implemented effectively. The study demonstrates the wide-reaching impact of integrated and interdisciplinary 'upslope-downslope' thinking to tackle global soil erosion challenges.

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Section: Discussionmentioning

confidence: 99%

Integrating land‐water‐people connectivity concepts across disciplines for co‐design of soil erosion solutions

et al. 2020

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“…The corresponding ESP values (2.46 in organic systems and 1.73 in conventional systems) are lower than what would traditionally be expected to affect hydraulic properties according to the postulated threshold of ESP >15 for sodic soils (Richards, 1954). However, numerous rainfall simulation studies have highlighted that an ESP >1 (du Plessis & Shainberg, 1985) or an ESP >2 (Bloem & Laker, 1994; Laker & Nortjé, 2019) can already lead to a chemical dispersion of aggregates. Increased contents of exchangeable sodium are a widespread soil threat especially in semi‐arid and arid landscapes depending on anthropogenic alteration of water hydrology and the redistribution of salts (Burch, 1986; Rengasamy & Olsson, 1991).…”

Section: Discussionmentioning

confidence: 99%

“…However, numerous rainfall simulation studies have highlighted that an ESP >1 (du Plessis & Shainberg, 1985) or an ESP >2 (Bloem & Laker, 1994;Laker & Nortjé, 2019) can already lead to a chemical dispersion of aggregates. Increased contents of exchangeable sodium are a widespread soil threat especially in semi-arid and arid landscapes depending on anthropogenic alteration of water hydrology and the redistribution of salts (Burch, 1986;Rengasamy & Olsson, 1991).…”

Section: Interactions Of Soil Chemical Properties With Organic Carbon...mentioning

confidence: 99%

Responses of soil organic carbon, aggregate diameters, and hydraulic properties to long‐term organic and conventional farming on a Vertisol in India

et al. 2022

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Organic matter management can improve soil structural properties. This is crucial for agricultural soils in tropical regions threatened by high rainfall intensities. Compared to conventional farming, organic farming is usually deemed to increase organic carbon and improve soil structural properties such as stability and permeability. However, how much, if any, buildup of organic carbon is possible or indeed occurring also depends on soil type and environmental factors. We compared the impact of seven years of organic farming (annually 13.6 t ha−1 of composted manure) with that of conventional practices (2 t ha−1 of farmyard manure with 150–170 kg N ha−1 of mineral fertilizers) on soil structural properties. The study was conducted on a Vertisol in India with a two‐year crop rotation of cotton soybean wheat. Despite large differences in organic amendment application, organic carbon was not significantly different at 9.6 mg C g−1 on average in the topsoil. However, the size distribution of water‐stable aggregates shifted toward more aggregates <137 μm in the organic systems. Cumulative water intake was lower compared to the conventional systems, leading to higher runoff and erosion. These changes might be related to the lower pH and higher exchangeable sodium in the organic systems. Our results indicate that higher application of organic amendments did not lead to higher soil organic carbon and associated improvement in soil structures properties compared to integrated fertilization in this study. Chemical properties may dominate soil aggregation retarding the uptake and integration of organic amendments for sustainable agricultural intensification in tropical, semiarid climates.

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“…Acquired inequality comes from any non-genetic factor that causes plant-to-plant variability and is present under both allo- and self-competition. Pre-emergence factors are the delay and uneven plant emergence due to differences in sowing depth, insects, birds, rodents, herbicide residues (Pommel and Bonhomme, 1998 ), soil pathogens, seed vigor, soil temperature (Hamman et al, 2002 ), seed and seedling characteristics, seedbed components, plant density (Lamichhane et al, 2018 ), and soil crusting (Laker and Nortjé, 2019 ). Post-emergence contributors are age differences and spatial heterogeneity concerning soil, light interception, nutrition, diseases, weeds, and pests (Pan et al, 2003 ).…”

Section: Productivity Vs Competitivenessmentioning

confidence: 99%

Crop resilience via inter-plant spacing brings to the fore the productive ideotype

Tokatlidis

2022

Front. Plant Sci.

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Natural selection favors the competitive ideotype, enabling native plants to survive in the face of intense competition. The productive ideotype is the goal of artificial selection to achieve high crop yields via the efficient use of resources in a self-competition regime. When breeding is established under inter-genotypic competition, the competitive ideotype dominates and may fictitiously become selectable. The productive ideotype becomes selectable at the nil-competition regime, where widely spaced individuals prevent plant-to-plant interference for any input. Principal reasons bring to the fore the productive ideotype that combines low competitiveness and improved plant yield efficiency. Crop spacing via the productive ideotype is mandated to alleviate the varying optimum density and ensure efficient use of resources inter-seasonally, cope with intra-field variation and optimize resource use, compensate for missing plants and promote stability, counteract unpredictable stresses and offer a buffer against environmental diversity, and adopt low-input agriculture to conserve natural resources and the environment. For breeding toward the productive ideotype, nil-competition is the due condition to overcome the confounding effects of competition, maximize phenotypic differentiation and facilitate selection from an early segregating generation, optimize heritability due to moderated environmental variance and experimental designs that sample spatial heterogeneity, apply high selection pressure focusing exclusively on the targeted genotype, and avoid the risk of bias selection or loss of desired genotypes due to proximity to empty hills. The view of a modern crop variety composed of genotype(s) belonging to the productive ideotype is a viable option to reach crop resilience serving sustainability in enormously fluctuating agroecosystems.

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Review of existing knowledge on soil crusting in South Africa

Cited by 33 publications

References 46 publications

Integrating land‐water‐people connectivity concepts across disciplines for co‐design of soil erosion solutions

Integrating land‐water‐people connectivity concepts across disciplines for co‐design of soil erosion solutions

Responses of soil organic carbon, aggregate diameters, and hydraulic properties to long‐term organic and conventional farming on a Vertisol in India

Crop resilience via inter-plant spacing brings to the fore the productive ideotype

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