Organic carbon fractions and micronutrient status of soils under some plantation crops in southwestern Nigeria

The organic carbon (OC) fractions and micronutrient status of soil under cashew (Anacardium occidentale), plantain (Musa spp), oil-palm (Elaeis guineensis) and gmelina (Gmelina arborea) plantations were studied to determine their effectiveness for managing converted forest in the derived savanna ecology of southwestern Nigeria. The control secondary forest soil had statistically similar OC (2.11%) at 0–15 cm with gmelina but significantly higher than those of the remaining plantation crops. At deeper depths, however, the OC content of the control forest was lower than those of other plantation crops. Apart from gmelina, other plantation crops had carbon enrichment ratio (CER) <1 at 0–15 cm. Only gmelina sequestered as much non-hydrolysable carbon (NHC) as the control at 0–15 cm depth. Also it was observed that plantain plantation sequestered higher NHC than the control at 15–30 cm depth. At >30 cm depth, however, none of the plantation crops sequestered as much NHC as the control. Using the average NHC at all the soil depth as a quality index, gmelina has a better potential to sequester NHC than the other plantation crops used in this study.     

Copper micronutrient fixation kinetics and interactions with soil constituents in semi-arid alkaline soils

This study examined the fixation pattern and kinetics of plant-available [diethylene triamine pentaacetic acid (DTPA)-extractable] copper (Cu), as well as basic soil properties that influence Cu availability in selected semi-arid soils. Soil samples from six different series were used and data obtained from Cu extraction experiments fitted to various kinetic models. Soils were also characterized for a suite of chemical and physical properties. The majority (80%) of the plant-available Cu fixed over the experimental period of 90 d occurred within the first 14 d. The amount of plant-available Cu fixed within the first 14 d tended to be influenced by the combination of organic matter (OM) and pH. The total amount of Cu fixed at the end of the experimental period of 90 d was influenced by pH and a combination of pH and calcium carbonate. The fixation of plant-available Cu over the experimental period was better described by the power function model [R² = 0.90, Standard Error (SE) = 0.099] but poorly by the other models (R²: 0.58 to 0.59), while reactions within the first 35 d were better described by the second-order model (R² = 0.98, SE = 0.008), suggesting a different fixation pattern. Findings from this study provide a basis for a more mechanistic approach to evaluating and comparing the fixation of Cu micronutrient compounds in these semi-arid soils for more scientific management decision making.     

湖南省几种主要母质发育的水稻土有效态微量元素含量及评价

采用调查采样、室内分析和评价的方法,研究了湖南省几种主要母质发育的水稻土的有效态微量元素含量及丰缺状况。结果表明,土壤有效Fe和有效Mn含量很高,属于丰富级别;土壤有效Cu、有效Zn和有效B含量极低,处于缺素状态,需要补充和施用Cu、Zn和B肥,以保证水稻的正常生长。     

Effect of long-term application of farmyard manure on soil micronutrient status

In a long-term experiment conducted (1967?–?2001) at Hisar, India, pearl millet (Pennisetum typhoides) and wheat (Triticum aestivum) was grown during summer and winter in a rotation. The treatments consisted of farmyard manure (FYM) at the rate of 15, 30 and 45 Mg ha^???1 during one or both the seasons. A treatment without FYM was maintained as a control. This made the total number of treatments 10, along with 2 levels of nitrogen at 0 and 120?kg ha^???1. Samples from 0?–?15, 15?–?30 and 30?–?45?cm soil depths were collected and analysed for DTPA extractable and total content of zinc, iron, manganese and copper. Application of FYM significantly increased the DTPA extractable and total content of all the studied micronutrients in all soil depths. The increase was higher in the surface layer than in the lower depths. The time of application of FYM influenced the content of soil micronutrients. DTPA extractable and total content of micronutrients was higher when FYM was applied in winter as compared to summer. Application of N has no effect on DTPA extractable or total micronutrients content.     

Characteristics and fertility constraints of degraded soils in Leyte,Philippines

Knowledge of the characteristics and fertility status of degraded soil is fundamental to planning suitable soil management strategies for crop production purposes. Such knowledge can be obtained through quantitative appraisal of soil properties and assessment of soil fertility status. Sixty soil samples were collected from five locations at Ormoc, Baybay, Bontoc, Bato and Matalom on the western side of Leyte island, Philippines. An important physical constraint in most of the soils is the high clay content, particularly in the soils of Baybay and Bato where it is a problem for cultivation. The strongly acidic and strongly alkaline pH, low available P and, in some cases, low exchangeable K are the chemical constraints. Variation in the physical and chemical constraints of these degraded soils is directly or indirectly related to the nature of the parent material, geomorphic position and anthropogenic effect. Soil fertility characteristics are distinct within similar soil types, primarily because they are related to the dominant soil-forming processes. Consideration of the soil physical and chemical constraints is essential for the long-term planning of soil management strategies that will lead to sustainable utilization of these problematic soils.     

中国下蜀黄土发育的土壤表层及典型剖面的硫状况

Studies were conducted to examine factors which might influence the status and distribution of S in some surface horizons and typical profiles of soils derived from Xiashu loess on the upper slope (US), middle slope (MS) and lower slope (LS) of Nanjing-Zhenjiang-Yangzhou hilly zone. The total S contents varied from 70.30 to 350.21 mg/kg, and the average for all surface soils was 218.3 mg/kg. The average S contents in the profiles followed the sequence: USo) and the ratio of amorphous iron oxide to free iron oxide (Fe_o/Fe_a), but no significant relationship was found between total S and the ratio of free iron oxide to total iron (Fe_d/Fe_t). Inorganic sulphate in paddy soils (MS and LS) was nearly higher in surface soil than in subsurface soil and subsoil, it, however, remained relatively unchanged with increasing depth for the original soil profile (US). The average organic S accounted for 94% of the total S in the surface soils, but the percentage decreased with depth in the profiles. Like the total S, the organic and inorganic S contents were highly significantly correlated with organic matter, total N, Fe_o and Fe_o/Fe_d ratio, but they were insignificantly related to Fe_d/Fe_t ratio. The C/S and N/S ratios in this study were somewhat lower than the results reported by others. The C/N/S ratios varied considerably within the same profile and among different soils but they fell within the range of values reported worldwide.     

Land use and soil conservation strategies for potentially highly erodible soils of central-eastern Nigeria

In areas susceptible to erosion, there is the need for a comprehensive soil conservation programme so as to be able to prevent catastrophic soil erosion problems. The absence of such a programme in central eastern Nigeria, that has a total land area of 20 000 km², necessitated the drawing up of a soil conservation strategy for the area. The aim was to provide information for better land-use planning and proper environmental and soil management. To achieve this, topographic, soil and landform maps of the area at the scale of 1:50 000 were used to delineate into slope land units, viz: 0–4 per cent, <4 per cent, drainage basins and headwaters. These slope units and estimated soil erosion hazard units using the revised universal soil loss equation (RUSLE) were employed to form a general purpose land classification based on the USDA land capability classification and FAO framework on land evaluation.The soil loss tolerance of the area falls between 1·16 and 1·30 Mg ha⁻¹ yr⁻¹, while the erosion hazard units are considered generally suitable for the various land utilization types, with a number of limitations the main ones being erosion and waterlogging. The soil conservation measures proposed involved the application of bioenvironmental processes in the area and appropriate watershed management. The techniques proposed are those based on low input technology, affordable by rural farmers. It is concluded that these soil conservation measures will be adequate for sustainable agricultural production in the area. Copyright © 1999 John Wiley & Sons, Ltd.     

Farmers' land management practices and status of agricultural land in the Jos Plateau,Nigeria

A wide range of land management practices, including application of fertilizers, contour‐plowing, stone bunds, mulching and agroforestry, have been adopted by farmers in the Jos Plateau to control degradation. This study examined the relative popularity of 13 land management practices based on mainly qualitative primary information collected through a questionnaire survey of 150 farm households and group discussions held during May to August 2007. The results of the analysis revealed four practices, namely, application of chemical fertilizers and farm yard manure, intercropping and crop rotation were highly popular. These practices generally need little technical skills, show positive short‐term benefits and short establishment time, suggesting that the benefits of increased productivity can be obtained quite quickly. Practices like agroforestry, mulching, legume cultivation and crop residue barriers were moderately popular as they take time, sometimes up to 3 years, before some benefits could be manifested. For farmers dependent on the farm income without any financial back‐up, this is too long as many do not have the economic capital to apply a practice that will only start showing benefits after a few years. The least popular practices were stone and earthen bunds, grass strips, alley cropping and contour‐plowing. These prove to be more labour intensive, and with dwindling labour force in the area, the adoption trend favours other practices requiring relative less labour. Farmers could not control land degradation effectively, despite their efforts made to manage land. Broad policy recommendations are made in line with findings of the analysis. Copyright © 2010 John Wiley & Sons, Ltd.     

利用方式和土壤肥力对土壤团聚体和养分的影响

The size distribution of water-stable aggregates and the variability of organic C, N and P contents over aggregate size fractions were studied for orchard, upland, paddy, and grassland soils with high, medium, and low fertility levels. The results showed that > 5 mm aggregates in the cultivated upland and paddy soils were 44.0% and 32.0%, respectively, less than those in the un-tilled orchard soil. Organic C and soil N in different size aggregate fractions in orchard soil with high fertility were significantly higher than those of other land uses. However, the contents of soil P in different size aggregates were significantly greater in the paddy soil as compared to the other land uses. Soil organic C, N and P contents were higher in larger aggregates than those in smaller ones. The amount of water-stable aggregates was positively correlated to their contribution to soil organic C, N and P. For orchard and grassland soils, the > 5 mm aggregates made the greatest contribution to soil nutrients, while for upland soil, the 0.25-0.053 mm aggregates contributed the most to soil nutrients. Therefore, the land use with minimum disturbance was beneficial for the formation of a better soil structure. The dominant soil aggregates in different land use types determined the distribution of soil nutrients. Utilization efficiency of soil P could be improved by converting other land uses to the paddy soil.     

The determination of extractable plant available selenium from soils by electrothermal atomic absorption spectroscopy

Abstract

Plant available selenate was measured in a soil extract by electrothermal atomic absorption spectroscopy. Selenate in soil was first extracted with potassium sulfate then extracted into toluene fron an iodide‐sulfuric acid media. Aliquots of the toluene were injected into the graphite furnace for selenium determination. Quantities of extractable selenium measured using the electrothermal atomic absorption method compared favorably with the results of determinations using a fluorometric technique on aliquots of the soil extract. The simplicity of the procedure allowed for the precise determination of soil selenate in a brief period of time.     

不同土地利用方式对土壤养分及肥力的影响

以山东省临沂市四种典型土地利用方式为例,分析不同土地利用方式对土壤养分及肥力的影响.结果表明:不同土地利用方式对有机质(OM)含量具有显著影响,而对pH、全磷(TP)、全氮(TN)、全钾(TK)和土壤颗粒组成无显著影响.不同土地利用方式土壤OM含量由高到低顺序为:水田>未利用地>林地>旱地;TN含量由高到低顺序为:未利用地>林地>水田>旱地;TP含量由高到低顺序为:未利用地>旱地>林地>水田;TK含量由高到低顺序为:林地>水田>旱地>未利用地.相关分析表明,旱地各养分之间的相关系数要大于水田、林地和未利用地,不同土地利用方式对TP和TN之间的相关系数无影响.主成分分析表明,旱地、水田、林地和未利用地综合肥力指标F值大小顺序为:水田(0.86)>林地(0.78)>旱地(0.51)>未利用地(0.43).     

Various Applications of Seaweed Improves Growth and Biochemical Constituents of Zea Mays L. and Helianthus Annuus L.

In this study, the effect of seaweed on the growth of Zea mays L. and Helianthus annuus L. was investigated. Seeds of the plants have been soaked for 6 hours in 0.5% Gracilaria corticata and 1.0% Enteromorpha flexuosa aqueous extract. The presoaked seeds were sown both in soil irrigated monthly with aqueous extract and in soil mixed with powdered seaweeds. Growth parameters of plants were studied after 60 days of growth. The results revealed that both applications of G. corticata and E. flexuosa enhance shoot length, root length, shoot and root dry weights, photosynthetic pigments, carbohydrate and protein contents, and nutrient uptake. The maximum growth was observed with irrigation by E. flexuosa extract. The element constituent [nitrogen (N), phosphorus (P), potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), iron (Fe³⁺), manganese (Mn²⁺), and zinc (Zn²⁺)] and phytohormones [Indole-3-acetic acid (IAA), gibberellins, and cytokinins] of E. flexuosa extract and powder was higher that of G. corticata. Of the two seaweeds tested, E. flexuosa exhibited better responses.     

福建省变性土的性质、形成和肥力

The zonal soils in the south subtropical zone of Fujian are lateritic red soils.A type of dark clayey soils.which was historically defined as lateritic red soils,derived from weathering products of the basalts was indicated by the investigation results to be markedly different from lateritic red soils and could be classified as Typical Hapluderts.They are distributed as complex zones with the lateritic red soils.The vertisols in this region were considered as a type of lithogenic soils and the vertic characteristics delay and inhibit the soils from allitic processes and then formed an independent soil type.The vertisols have higher fertility and better agricultural production characters than the lateritic red soils.The different ways in utilizing and managing these soils according to their properties and fertility are also suggested.     

Kinetics of phosphorus release from calcareous soils under different land use in Iran

The rate of phosporus (P) release from soils can significantly influence P fertility of soils. The objectives of this study were to investigate the effects of land‐use types on the kinetics of P release under different management practices and the relationship between kinetic parameters and soil physical and chemical properties from calcareous soils. The kinetics of P release in 0.01 M CaCl₂ was studied in surface samples of 30 calcareous soils planted to garlic, garden, pasture, potato, vegetables, and wheat. Trend in P‐release kinetics was similar between land‐use types. Significantly different quantities of P were released under different land use. The maximum amount (average of five soils) (46.4 mg kg^–1) of P was released in soil under potato and the minimum amount (10.4 mg kg^–1) under pasture. The kinetics of P release from soils can be described as an initial rapid rate followed by a slower rate. Different models were used to describe P release. In general, parabolic diffusion and power equation were found to be appropriate for modeling P release. The P‐release rate for the soils was estimated by parabolic equation for the studied land‐use types. The constant b was lower for pasture and wheat than for garlic and potato. The relationship between the rate of P release with Olsen‐P was linear, while it was curved with respect to the CaCl₂‐P, indicating that release of P was diffusion‐controlled. When the kinetic parameters of models were regressed on soil properties, CaCl₂‐P and CaCO₃ appeared to be the most important soil properties influencing P‐release rates in these soils.     

Diversity of arbuscular mycorrhizal fungi in soils of yam (Dioscorea spp.) cropping systems in four agroecologies of Nigeria

The diversity of arbuscular mycorrhizal (AM) fungi in soils under a yam cropping system in four agroecologies of Nigeria was investigated. Soil samples were collected from yam fields at Onne (humid forest, high rainfall area), Ibadan (derived savanna), Abuja (Guinea savanna) and Ubiaja (humid forest, medium rainfall area). Soil characteristics, AM fungi species, spore abundance, Shannon diversity index, species richness and evenness were determined. A total of 31 AM fungi species was isolated from the four agroecologies with a range of 14–20 species found in a single location. Glomus species were the most abundant among AM fungi species with G. geosporum, G. intraradices and G. mosseae occurring in large populations in all locations. Ubiaja, which had a cassava/natural vegetation sequence before yam, had significantly higher spore abundance and species richness than the other locations, which had a yam/legumes or a maize/legume sequence before yam. However, diversity was significantly higher at Abuja, which had a maize/legume sequence with yam, than Ibadan, which had only a yam/legume sequence. The study revealed significant diversity in AM fungal species across agroecologies in yam-growing regions. Further research on the functional consequences of changing composition of AM fungi species across the region is recommended.     

Phosphorus status of some paddy soils in Bangladesh

Abstract

Phosphorus status of Bangladesh paddy soils covering the major paddy soil types was assessed in terms of parent materials and physiography. Total P concentration ranged from 172 to 604 mg kg^?1 in the topsoil and from 126 to 688 mg kg^?1 in the subsoil, and varied with the physiography to which the soils belonged. In most soils, the available P concentration was much higher for the topsoil than for the subsoil. The inorganic P concentration was higher than the organic P concentration, except for one soil series from the Old Himalayan Piedmont Plain, and was significantly and positively correlated with the total P concentration. Among the inorganic forms, only the concentration of Al-bound P showed a significant correlation with that of available P based on the Bray P-2 method in both topsoil and subsoil. In general, the P status was critically low in paddy soils of the terrace area. Normal growth of paddy rice in this area is expected to be difficult without application of P fertilizer.     

生物质炭对酸性土壤改良作用的研究进展

由于生物质炭在农业和环境中的巨大应用前景和对土壤碳的增汇减排作用,近期成为土壤学家和环境学家研究的热点。本文综述了生物质炭对热带和亚热带地区酸性土壤的改良作用及其机制,总结了生物质炭对土壤肥力和养分有效性及作物生长和产量的影响的研究进展,分析了该领域未来的发展趋势,可为酸性土壤改良和管理提供参考。     

Changes in the soil phosphorus status of agricultural land in the Netherlands during the 20th century

The Netherlands has a high cumulative mean phosphorus (P) balance. In the 20th century, cumulative mean P surpluses were ca. 4500 kg P₂O₅/ha. The annual surpluses have levelled off because of manure application limits from 1984 onwards. We report the effect of soil type, land use, and manure policy on changes in soil P of fields in the Netherlands during the 20th century. We used data (>5 million soil P tests) from the soil analysis laboratory BLGG AgroXpertus. Our results show that soil P has increased on average to fairly high and high ratings. Differences between regions and between land use have remained high from the first records in the 1930s; on arable land the increase continued until the end of our study period while on grassland no changes are evident in the last decades. In general regions with high livestock density have high soil P status. Soil P increased in the order bulbfields < grassland < arable land < maize land < horticulture, and in the order loess < clay < peat < sand soils. Spatial variations in P values reflect more the market value of the crops and regional availability of animal manure than (fertilizer) recommendations. Manure policy since 1984 has resulted in increasingly tight restrictions on P application from manure and fertilizers, but the effects are not yet clearly reflected in changed trends in soil P.     

Phosphorus and potassium fertility of some riceland soils in Indonesia

Abstract

Contents of soil phosphorus and potassium vary appreciably in different localities of the Indonesian Archipelago. Data collected for riceland soils from seven irrigation areas (five on Java and one each on Sumatra and Sulawesi) show that average available phosphorus contents in the tilled layer may range from 23 ppm P at the Sumatra location to 203 ppm Pat the Sulawesi location. Average exchangeable potassium contents ranged from less than 0.2 meq/100g. K in the Sumatran soils to over 1.0 meq/100g. in potash‐rich soils of Java. Distinct regional differences in soil fertility of the magnitude observed indicate that blanket fertilizer recommendations cannot be made if rice production is to be increased without wasting chemical fertilizers which are relatively scarce and expensive in Indonesia. Increased emphasis must be placed on soil testing and soil fertility research in order to achieve the national goal of self‐sufficiency in food stuffs.     

Nutrient Mineralization from Deoiled Neem Seed in a Savanna Soil from Nigeria

Abstract

The mineralization of nutrients from deoiled neem seed (neem seed cake), the residue left after oil extraction, was examined in a typical savanna soil with a view to determining its potential for fertility improvement. The neem seed cake (NSC) application rates were 0, 2.5, and 5.0 g kg^?1 soil (0, 5, and 10 tons ha^?1). The concentrations of ammonium‐nitrogen (NH₄‐N) and nitrate (NO₃)‐N mineralized from the neem‐amended soil were two to three times greater than the control. Similarly, exchangeable potassium (K), magnesium (Mg), and cation exchange capacity were significantly greater than the control. The neem‐amended soil maintained organic carbon (OC) at the pre‐incubation level, whereas OC in the control soil declined to significantly less than the pre‐incubation concentration. The electrolytic conductivity of the soil saturation extract with neem application was 8–10 times greater than the control soil. However, the NSC increased exchange acidity markedly and decreased the soil pH significantly. Thus, the benefits of NSC in increasing the concentrations of N, K, and Mg and maintaining OC of the soil must be weighed against the consequences of soil acidity, though it is unlikely that NSC can acidify the soil to the same extent under field conditions as it did in this closed‐system incubation study.