Fragile Soils Research Articles

Effect of rhizobia, mycorrhizal fungi and phosphate-solubilizing microorganisms in the rhizosphere of native plants used to recover an iron ore area in Brazil

The iron-ore deposits in Minas Gerais state are concentrated in an area named Ferruginosous Quadrilateral, in which the dominant vegetation belongs to the Cerrado biome (savanna type, called campo rupestre or rupestrian field). This vegetation occurs in altitudes higher than 1000 m and is one of the most endangered biomes of the world. This study aimed to restore an area of rupestrian field used to keep iron-ore products, in which vegetation had been cut and thus resilience did not occur, worsening the low fertility of the fragile soil. Therefore, a revegetation model was proposed using two native species, Centrosema coriaceum (Leguminosae) and Tibouchina multiflora (Melastomataceae), inoculated with selected strains of arbuscular mycorrhizal fungi (AMF) and/or a rhizobium strain. After 48 months of plantation, the plant growth, survival index, physical and chemical soil properties, leaf nitrogen (N) and phosphorous (P), and P soil were evaluated. Inoculated plants benefited in all the analyzed aspects. While T. multiflora presented increased P content in leaves and soil rhizosphere only in inoculated plants, C. coriaceum showed the highest P content in both leaves and soil independently of inoculation. Although the inoculated plants presented more intense root colonization (AMF), the same mycorrhizal species were found in both inoculated and non-inoculated plants of C. coriaceum and T. multiflora. However, species of the Gigasporaceae family were favored in the C. coriaceum rhizosphere, as compared with T. multiflora. In addition, C. coriaceum was able to select in its rhizosphere a rhizobia strain efficient in P solubilization and a large and efficient population of phosphorus solubilizing microorganisms (PSM), preferentially composed of fungi. Through the similarity of their Internal Transcribed Spacer (ITS) sequences, the PSM fungi were identified as Fusarium oxysporum and Aspergillus fischeri using the BLAST database. The data presented suggest that C. coriaceum showed a strong rhizosphere effect in favor of a tripartite action of rhizobia, fungi and AMF populations as strategies to solubilize soil phosphate for survival and plant growth in the rupestrian field. Therefore, the inoculation of these microorganisms is desirable for mine recover.

Laws of sustainable soil management

The challenge of doubling the world’s food grain production by 2030 is even more daunting because of the decrease in per capita arable land area and renewable fresh water resources; increase in risks of soil and environmental degradation; and threat of decrease in use efficiency of inputs because of the projected climate change. Thus, the need for identifying processes, practices and policies that govern sustainable management of soil resources is more critical now than ever before. The goal is to minimize risks of soil degradation by enhancing its resilience and improving ecosystem services of the finite and fragile soil resource. Here, 10 principles are given for sustainable management of soil. This report is an introductory article of the book Sustainable Agriculture, published by Springer, EDP Sciences (Lichtfouse et al. 2009).

Improving Livestock Production Through Alley Farming Practice In Anambra State

Alley Farming is a system where food crops are planted in the alleys between hedgerows of leguminous trees. An appraisal study was undertaken to review the importance and need to combine alley farming with livestock production in fragile soil of Anambra State using structured questionnaire and oral interview method. Results showed that the system offered a means of integrating livestock with crop production. When practiced on sloppy lands, the trees help to check erosion and conserve the soil. The trees chosen for the system were capable of maintaining and improving soil fertility, remain productive under pruning, allow improved crop production and provide nutritious and palatable livestock feed. Leucaena Leucocephala (Leucenia), Cajanus Cajan (pigeon pea), Diallium guineense (Icheku) found to be most suitable under Anambra environment. The system was found to have increased crop yield and animal productivity in the area of study. It is therefore recommended to cash-strapped poor farmers and government agencies in Anambra state. Journal of Research in National Development Vol. 4 (1) 2006: pp. 35-39

Practices to Reduce Failures: Undermining and Underpinning—Suggestions for Minimizing Damage to Adjacent Buildings during Construction

• Recommend that test pits be made to determine the character, depth, and condition of the adjacent foundations. • Request access into the adjacent buildings for the purpose of determining the type of construction, general condition, and depth of the basement and cellars. • Attempt to obtain drawings for the adjacent structures. • Recommend that a preconstruction visual survey of the adjacent properties be performed for the purpose of documenting the condition of the properties. Consider providing a copy to the owners of the adjacent properties. • If underpinning will be needed, identify problematic conditions such as fragile foundations and difficult soils.

Effect of straw and plastic film management under contrasting tillage practices on the physical properties of an erodible loess soil

The current cropping system of excessive tillage and stubble removal in the northwestern Loess Plateau of China is clearly unsustainable. A better understanding of tillage and surface cover management on surface soil structure is vital for the development of effective soil conservation practices in the long term. Changes in surface soil structure and hydraulic properties were measured after 4 years of straw and plastic film management under contrasting tillage practices (no tillage vs. conventional tillage) in a silt loam soil (Los Orthic Entisol) which had been under conventional management for hundred of years in the northwestern Loess Plateau, China. Surface soil (0–10 cm) under no tillage with straw cover had the highest water stability of macro-aggregates (>250 μm) and the highest saturated hydraulic conductivity. Compared with straw cover, plastic film cover did not change macro-aggregate stability and the soil had the lowest saturated hydraulic conductivity ( K sat) but the highest % <50 μm soil particles. Significant correlation was found between water stable macro-aggregates and soil organic carbon content, indication the importance of the latter on soil structural development. No tillage on its own (without straw cover) was not sufficient to improve structural stability probably due to lack of organic carbon input. While use of plastic film cover might lead to short term yield increases, results indicated that it did little to improve soil physical fertility. On the other hand, no tillage with straw cover management should lead to long-term improvement of physical quality of this structurally fragile soil.

Fragile soil

Guatemalan lake sediments reveal decoupling of soil erosion rates from population density during ancient Maya settlement

Crop Residue Coverage of Soil Influenced by Crop Sequence in a No‐Till System

Field research was conducted to determine the influence of crop and crop sequencing on crop residue coverage of soil with 10 crops [buckwheat (Fagopyrum esculentum Moench), canola (Brassica napus L.), chickpea (Cicer arietinum L.), corn (Zea mays L.), dry pea (Pisum sativum L.), grain sorghum [Sorghum bicolor (L.) Moench], lentil (Lens culinaris Medik.), oil seed sunflower (Helianthus annuus L.), proso millet (Panicum miliaceum L.), and hard red spring wheat (Triticum aestivum L.)]. Crop residue production was obtained. Crop residue coverage of the soil surface was measured with a transect technique at the time of seeding spring wheat. Crop residue coverage varied and was more clearly associated with the second‐year crop than with the first‐year crop of a 2‐yr crop sequence. Crop sequences composed of spring wheat, proso millet, and grain sorghum had higher crop residue coverage compared with sequences composed of the other crops. When these three crops and three crops that provide lower crop residue coverage of soil the subsequent year (lentil, chickpea, and sunflower) were analyzed as a subset to compare various sequences of crops providing a range of residue coverage, for example, lower (first yr)/lower (second yr), the surface residue coverage ranged from 65% for the lower/lower combination to 93% for the higher/higher combination in 2004 and from 56 to 94% in 2005, respectively. A producer operating on more fragile soil and concerned about reducing soil erosion hazards would be advised to grow crops that provide higher residue coverage in the year before crops that provide lower residue coverage.

Impacts of tillage, cover crop, and nitrogen on populations of earthworms, microarthropods, and soil fungi in a cultivated fragile soil

The impacts of tillage regime, cover crop, and nitrogen on various soil organisms inhabiting a fragile sandy soil (Brunosolic Gray Brown Luvisol) were determined. Soil samples were collected between 2000 and 2003 from a long-term tillage experiment, established in 1988 to determine the effect of tillage systems on yield of corn ( Zea mays), soil quality, and weed populations. Populations of several of the soil organisms studied were significantly affected by one or more agronomic treatments. A single earthworm species, Aporrectodea turgida, was found in the experimental area. Worm populations were generally low and dominated by juveniles. Spring-sampled populations were significantly higher in no-till plots than in conventionally tilled plots. Fall-sampled populations were not affected as greatly by tillage, but were generally higher in no-till plots not receiving additional nitrogen or in plots overseeded with a rye ( Secale cereale) cover crop. Soil microbial biomass, as represented by extractable soil DNA, was higher in the spring than in the fall. Populations of the soilborne stramenopile Pythium were generally higher in conventionally tilled plots, and were increased by a rye cover crop. Higher rates of nitrogen increased populations of total soil fungi but nitrogen had little effect on prostigmatid or cryptostigmatid mites; prostigmatid populations were generally higher in no-till plots. Spring populations of mesostigmatid mites were higher in plots with a rye cover crop than in plots without an overwintering plant cover. Conventional tillage stimulated populations of astigmatid mites during periods of high rainfall. Collembola populations were dominated by the families Onychiuridae and Isotomidae, but neither was greatly affected by any tillage treatment. Principal component analysis showed that populations of A. turgida and soil aggregation tended to be positively associated with one another, but that variations in populations of Onychiuridae springtails, prostigmatid mites, and Pythium tended not to be associated with changes in other variables. Overall, effects of tillage treatments on soil organisms were found to differ from previous reports in several respects, suggesting that soil type may impose conditions that over-ride the impacts of agronomic cultivation systems on populations of soil organisms.

An environmental analysis model: interactions among soil, society and economy

O modelo apresentado estabelece três dimensões de análise: a biofísica, a econômica e a social. A hipótese apresenta a existência de relações entre as variáveis, tornando possível estabelecer áreas homogêneas no território. O objeto de análise é um espaço rural de 1.346.486 ha., no qual vivem 12.147 pessoas em 2.402 estabelecimentos rurais. O método de trabalho consistiu na aplicação dos principais componentes, em três matrizes de dados, montadas sobre um Sistema de Informação Geográfico. A análise quantitativa foi complementada com entrevistas em profundidade. A erosão dos solos foi o aspecto central da dimensão biofísica, que foi relacionado com aspectos sociais, particularmente a pobreza rural e a produção agropecuária. O método de componentes principais, combinado com o Sistema de Informação Geográfico, mostrou-se adequado para interpretar a atual distribuição de áreas homogêneas em Paissandu. O espaço rural se caracteriza por quatro áreas: a pecuária extensiva, com pouca densidade populacional e escassa erosão; a pecuária de estabelecimentos agrícolas médios, sobre solos frágeis, com habitações pobres; a agrícola-leiteira-florestal, sobre solos frágeis e erodidos, com habitações pobres e área com população desruralizada. A erosão do solo está associada com o uso agrícola sobre solos frágeis, em explorações pequenas, como a dos colonos. A pobreza rural está relacionada com áreas de solos agrícolas frágeis, elevada divisão de edificações, associadas a grandes extensões da pecuária e florestal. O modelo permite avaliar a situação atual do território, como base para o planejamento ambiental.

Innovative Technologies: Sweet Deal for Cocoa Production?

Innovative Technologies: Sweet Deal for Cocoa Production?

Chemical Partitioning of Fe, Mn, Zn and Cr in Mountain Soils of the Iberian and Pyrenean Ranges (NE Spain)

The bioavailability of heavy metals, and thus their possible harmful impact on ecosystems and humans, depends on metal partitioning. This study describes the chemical partitioning of iron, manganese, zinc and chromium, because the potential effect of soil contamination is better assessed through the knowledge of the forms in which a given metal is present rather than the use of its total concentration. In four soil types representative of mountain soils in the Iberian and Pyrenean ranges in Aragón, a total of 16 selected sites have been sampled and five subsamples were taken in each site to create a composite sample. The 4 heavy metals have been extracted by the sequential extraction procedure of Tessier et al. (1979) and analyzed by emission atomic spectrometry of solid state (ICP OES). Little Fe, Mn and Zn (< 1, 2.4–35.9, < 1–24.5 mg/kg, respectively) were retrieved from the exchangeable phase, a readily available phase for biogeochemistry cycles in the ecosystems. Chromium was not detected in the potentially bioavailable forms. The largest contents of Fe, Zn and Cr were retrieved from the residual phase with mean values of 21100, 72 and 60 mg/kg, and maximum values of 35700, 279 and 271 mg/kg, respectively. Mn was mainly bound to oxide phases with mean and maximum values of 236 and 887 mg/kg, respectively. For all metals, the highest contents are found in Leptosols on igneous rocks due to the rich and diverse mineral composition of their parent materials. The knowledge of the chemical partitioning of Fe, Mn, Zn and Cr provides information to identify the soils in which their mobile forms may be transferred to the soil-water-plant system. This information is of interest for the management of fragile mountain soils to avoid the environmental risk of cycling these metals in the environment.

Where is the Poverty–Environment Nexus? Evidence from Cambodia, Lao PDR, and Vietnam

Summary This paper investigates the poverty–environment nexus at the provincial and district levels in Cambodia, Lao PDR, and Vietnam. The analysis focuses on spatial associations between poverty populations and five environmental problems: deforestation, fragile soils, indoor air pollution, contaminated water, and outdoor air pollution. The results suggest that the nexus is quite different in each country. We conclude that the nexus concept can provide a useful catalyst for country-specific work, but not a general formula for program design. Joint implementation of poverty and environment strategies may be cost effective for some environmental problems, but independent implementation may be preferable in many cases as well.

Total soil organic matter and its labile pools following mulga (Acacia aneura) clearing for pasture development and cropping 1. Total and labile carbon

Mulga (Acacia aneura) dominated vegetation originally occupied 11.2 Mha in Queensland, of which 12% has been cleared, mostly for pasture production, but some areas are also used for cereal cropping. Since mulga communities generally occupy fragile soils, mostly Kandosols and Tenosols, in semi-arid environments, clearing of mulga, which continues at a rate of at least 35 000 ha/year in Queensland, has considerable impact on soil organic carbon (C), and may also have implications for the greenhouse gas emissions associated with land use change in Australia. We report here the changes in soil C and labile C pools following mulga clearing to buffel pasture (Cenchrus ciliaris) and cereal (mostly wheat) cropping for 20 years in a study using paired sites. Soil organic C in the top 0.05 m of soil declined by 31% and 35% under buffel pasture and cropping, respectively. Land use change from mulga to buffel and cropping led to declines in soil organic C of 2.4 and 4.7 t/ha, respectively, from the top 0.3 m of soil. Using changes in the δ13C values of soil organic C as an approximate representation of C derived from C3 and C4 vegetation from mulga and buffel, respectively, up to 31% of soil C was C4-derived after 20 years of buffel pasture. The turnover rates of mulga-derived soil C ranged from 0.035/year in the 0–0.05 m depth to 0.008/year in the 0.6–1 m depths, with respective turnover times of 29 and 133 years. Soil organic matter quality, as measured by the proportion/amount of labile fraction C (light fraction, &lt; 1.6 t/m3) declined by 55% throughout the soil profile (0–1 m depth) under both pasture and cropping. There is immediate concern for the long-term sustainable use of land where mulga has been cleared for pasture and/or cropping with a continuing decline in soil organic matter quality and, hence, soil fertility and biomass productivity. In addition, the removal of mulga forest over a 20-year period in Queensland for pasture and cropping may have contributed to the atmosphere at least 12 Mt CO2-equivalents.

Hemp Production in Aotearoa

Abstract Hemp is new to Aotearoa, the indigenous name of New Zealand (NZ). The NZ government approved the experimental cultivation of hemp in 2001. Eleven cultivars have been cultivated to date, ‘Anka’, ‘Carmen’, ‘Fasamo’, ‘Felina’, ‘Finola’, ‘Futura 77’, ‘Kompolti’, ‘Uniko B’, ‘USO 14’, ‘USO 31’, and ‘Zola’. Crops have been planted at 19 sites the past two seasons, in a wide range of latitudes, climates and soil types. NZ's fragile soil necessitates careful management of its fertility. Hemp fits into the paradigm of sustainable stewardship, organic soil fertilization, and responsible crop rotation. It can be rotated with existing fodder crops and vegetable crops. Hemp's well-known ability to suppress weeds makes its rotation with pasture an attractive way to clean soil banks of weed seeds. Hemp cultivated for seed produced maximal yields of 2800 kg ha−1; and fiber crops yielded stalk biomass (dry matter) as high as 13,900 kg ha−1. These yields are consistent with or greater than reports from the European...

DOMESTICATING PRIORITY MIOMBO INDIGENOUS FRUIT TREES AS A PROMISING LIVELIHOOD OPTION FOR SMALL-HOLDER FARMERS IN SOUTHERN AFRICA

ISHS XXVI International Horticultural Congress: Citrus and Other Subtropical and Tropical Fruit Crops: Issues, Advances and Opportunities DOMESTICATING PRIORITY MIOMBO INDIGENOUS FRUIT TREES AS A PROMISING LIVELIHOOD OPTION FOR SMALL-HOLDER FARMERS IN SOUTHERN AFRICA

Carbohydrates and aggregation in lowland soils of Nigeria as influenced by organic inputs

We evaluated the influence of several organic matter management practices on the characteristics of carbohydrates in water-stable aggregates and soil aggregate stability at three Nigerian locations (Abakiliki, Nsukka and Umudike) where forests had been converted to arable farming. The effect of management practices to enhance aggregate stability was site-specific. The highest aggregate stability was obtained with Gliricidia sepium at Abakiliki, with Cajanus cajan followed by rice mill wastes (RW) at Nsukka and with the forested soil at Umudike. While none of the treatments at all sites was able to enhance the C and N contents of the soils to the levels obtained in the forested sites, a net improvement in carbohydrate and organic carbon (OC) content was found for some management practices. The carbohydrate status increased with G. sepium at Abakiliki, and with Dactylodenae bacterii alone or in combination with Pentaclethra species at Umudike, while at Nsukka all organic inputs increased carbohydrate content over the control and forested soils. However, neither total OC nor the carbohydrate content were significantly correlated to the variability in aggregate stability of these soils. The δ 13 C values found for acidic hydrolysates were constant within the soil aggregate sizes and generally distributed around −29 to −30‰, suggesting that the OC from these sites originated from C3 plants. Our results indicate that in these tropical Nigerian soils, aggregate stability and OC content are generally preserved by alley-cropping in well structured soil, whereas treatments with organic wastes are sustainable management practices in more fragile soils.

EVALUATING THE ECONOMIC COST OF ENVIRONMENTAL MEASURES IN PLANTATION HARVESTING THROUGH THE USE OF MATHEMATICAL MODELS

An important issue being discussed for Chilean pine plantation policies is the application of environmental protection measures when managing its timber areas. Typical measures, already in place in more developed countries, include imposing riparian strips and protecting fragile soils from the use of heavy machinery. While environmental protection measures have been considered vital for decades, so far there has been almost no attempt to quantify both the benefits and costs of these measures. This paper attempts to measure the costs associated with the main measures which can help both the forestry firms and the government evaluate the cost impact of the new environmental protection regulations being studied. The analysis for different environmental scenarios is carried out by modifying a mixed integer LP, currently used for tactical planning by one forestry firm.

MINERAL NUTRITION, GROWTH AND YIELDS OF ANNATTO TREES (BIXA ORELLANA) IN AGROFORESTRY ON AN AMAZONIAN FERRALSOL

Permanent tree crop agriculture and multi-strata agroforestry are among the most promising options for the agricultural use of the mostly nutrient-poor and physically fragile soils of central Amazonia. In general, though, information on the optimum management of local tree crops under these conditions is inadequate. Annatto (Bixa orellana) is a small tree of tropical American origin whose seeds contain a non-toxic, carotenoid dye that is used widely in food and cosmetic products. The authors studied seed yields at ages four to seven years, biomass at seven years, nutrient accumulation and mineral nutrition of annatto trees growing in multi-strata agroforestry with different inputs of fertilizer and lime on a xanthic Ferralsol in central Amazonia. Leaf samples of three age classes were collected four times during one year, and nutrient concentrations were related to soil nutrient status, growth and yield of the trees in order to develop an optimum sampling scheme for foliar analysis. Growth and yields of the trees showed a pronounced response to increased fertilizer and lime input, which seemed to be due mainly to improved availability of phosphorus. Nitrogen fertilizer had no effect and may not be necessary for well-established trees on this soil. High litter quality and substantial nutrient recycling with annual pruning make annatto a valuable component for agroforestry systems. In this experiment, however, yields were low and decreased after the fifth year, presumably as an effect of infertile soil, shading by larger trees and, possibly, a negative effect of the drastic annual pruning with removal of the entire leaf and small-branch biomass on the vitality of the trees. Annatto is probably best suited for associations with small tree crops. Less drastic pruning treatments than those practiced in this experiment may be preferable.

Cynodon dactylon control in sunflower (Helianthus annuus) with postemergence graminicides in a semi-arid environment

Field experiments were conducted during two cropping seasons in southeastern Botswana to investigate the efficacy of postemergence graminicides in controlling Cynodon dactylon in sunflower ( Helianthus annuus L.). Treatments consisted of haloxyfop applied at 1.08 and 2.16, fluazifop-p at 0.250 and 0.500, and sethoxydim at 0.150 and 0.300 kg ha −1 plus handweeded and unweeded controls. In 1998, haloxyfop and fluazifop-p applied at high rates reduced C. dactylon shoot dry weight by 80, and 59%, respectively; however, in 1999 they reduced grass shoot dry weight by 77 and 86%, respectively. Sethoxydim was less effective in controlling the perennial grass than haloxyfop and fluazifop-p. Visual assessment indicated that fluazifop-p and haloxyfop provided satisfactory grass control after a single application. Postemergence herbicides offer good weed control on fragile soils in a semi-arid environment.

Carbohydrates in water-stable aggregates and particle size fractions of forested and cultivated soils in two contrasting tropical ecosystems

Information on changes in storage and loss of soil organic carbon (SOC) when tropical forests are converted to cropland is needed for evaluating soil structural degradation and for selecting appropriate sustainable soil management practices. We evaluated changes in SOC storage of organic carbon and acid-hydrolyzable carbohydrates content of aggregated classes and particle size fractions of adjacent forested and cultivated soils in eight agroecosystems from Ethiopian highlands and Nigerian lowlands. In all agroecosystems, SOC content was two to four times higher in the forested than the cultivated soils. Higher SOC content was found in Ethiopian (20.2–47.3 g.kg−1) than Nigerian (12.0–24.0 g.kg−1) forested soils. The magnitude of reduction in SOC and total carbohydrates with cultivation was soil-specific, being generally higher in the sandy than the clayey soils. The smaller aggregate classes (< 1.00 mm) and the sand-sized particles (2000–63 µm) of the forested soils were preferentially enriched in carbohydrates relative to larger aggregates (4.75–1.00 mm). Carbohydrates were more concentrated in the clay-size fraction of the forested than in that of the cultivated soils. Cultivation reduced aggregate stability, increased the proportions of the smaller size aggregates and their associated carbohydrates relative to the forested soils. The susceptibility of the cultivated soils to loss in structural stability reflected this initial aggregation which was greater in the more stable clayey than the fragile sandy soils. The aggregate stability of either the forested or the cultivated soil could not be accounted for by the levels of OC or total carbohydrates in the soil.