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Available Phosphorus (available + phosphorus)
Selected AbstractsEffect of soil and physiographic factors on ecological plant groups in the eastern Elborz mountain rangeland of IranGRASSLAND SCIENCE, Issue 2 2010Mohammadreza Tatian Abstract To investigate the cause of differences among ecological plant groups in the east of the Elborz mountain rangeland, the role of edaphical and topographical characteristics was considered. Two ordination techniques, detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA), were used. The values of slope, aspect, altitude and lithology information were provided by Geographic Information System (GIS), and geomorphological land units were determined by intersection of overlaid data layers. Plant sampling was undertaken within nine land units with similar lithology and altitude but which differed in slope and aspect, using 30 randomly selected 1 m2 plots per land unit. Soil samples were taken from two depths (0,20 and 20,50 cm) in each plot. Organic matter, bulk density, texture, calcium carbonate, total nitrogen and available phosphorus and potassium contents were determined. The results indicated that plant species have different responses to edaphical and topographical parameters. The invader species group had a balanced amount of influence from all soil components and topographic factors, whereas the native grasses were located in productive soils, which typically have a low grazing intensity, such as the north facing slopes. Coniferous bushy trees, cushion plants and some shrub plant groups were found on steep slopes with alkaline soils. The broad-leaved bushy trees plant group was abundant in fine texture soils on low and humid slopes. [source] Effect of physical, chemical and environmental characteristics on arbuscular mycorrhizal fungi in Brachiaria decumbens (Stapf) pasturesJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2008R.H. Posada Abstract Aim:, To evaluate the effects of soil physical and chemical factors (pH, conductivity, humidity, available phosphorus and organic matter) and environmental factors (temperature, relative air humidity, altitude and atmospheric pressure) on arbuscular mycorrhizal fungi (AMF),Brachiaria decumbens grass relationship. Furthermore to establish patterns of microbiological responses that allow to differentiate the study sites in two relief types. Methods and Results:, Mycorrhizal characteristics (spore density, external hyphae and root colonizations by hyphae, vesicles and arbuscules), physical and chemical factors in soil and environmental factors were measured. Conclusions:, The effect of physical, chemical and environmental factors on microbiological variables was related to the type of relief ,valley and hilly terrain'; the AMF behaviour was affected only over narrower ranges of evaluated variables. Similarly, the colonization of B. decumbens roots by AMF hyphae, vesicles and the mycorrhizal spore density follow different patterns according to the relief type. Significance and Impact of the Study:, The type of relief is one of the factors to be taken into consideration to evaluate the AMF inoculum and root colonization of these pastures, because of the influence of slope , as physical property of soil , on AMF. [source] Structural response of Caribbean dry forests to hurricane winds: a case study from Guánica Forest, Puerto RicoJOURNAL OF BIOGEOGRAPHY, Issue 3 2006Skip J. Van Bloem Abstract Aim, Tropical dry forests in the Caribbean have an uniquely short, shrubby structure with a high proportion of multiple-stemmed trees compared to dry forests elsewhere in the Neotropics. Previous studies have shown that this structure can arise without the loss of main stems from cutting, grazing, or other human intervention. The Caribbean has a high frequency of hurricanes, so wind may also influence forest stature. Furthermore, these forests also tend to grow on soils with low amounts of available phosphorus, which may also influence structure. The objective of this study was to assess the role of high winds in structuring dry forest, and to determine whether soil nutrient pools influence forest response following hurricane disturbance. Location, Guánica Forest, Puerto Rico. Methods, Over 2000 stems in five plots were sampled for hurricane effects within 1 week after Hurricane Georges impacted field sites in 1998. Sprout initiation, growth, and mortality were analysed for 1407 stems for 2 years after the hurricane. Soil nutrient pools were measured at the base of 456 stems to assess association between nutrients and sprout dynamics. Results, Direct effects of the hurricane were minimal, with stem mortality at < 2% and structural damage to stems at 13%, although damage was biased toward stems of larger diameter. Sprouting response was high , over 10 times as many trees had sprouts after the hurricane as before. The number of sprouts on a stem also increased significantly. Sprouting was common on stems that only suffered defoliation or had no visible effects from the hurricane. Sprout survival after 2 years was also high (> 86%). Soil nutrient pools had little effect on forest response as a whole, but phosphorus supply did influence sprout dynamics on four of the more common tree species. Main conclusions, Hurricanes are able to influence Caribbean tropical dry forest structure by reducing average stem diameter and basal area and generating significant sprouting responses. New sprouts, with ongoing survival, will maintain the high frequency of multi-stemmed trees found in this region. Sprouting is not limited to damaged stems, indicating that trees are responding to other aspects of high winds, such as short-term gravitational displacement or sway. Soil nutrients play a secondary role in sprouting dynamics of a subset of species. The short, shrubby forest structure common to the Caribbean can arise naturally as a response to hurricane winds. [source] Determination of the soil organic carbon, nitrogen, available phosphorus and the combined aboveground plant materials in the semi-arid Mbulu District, TanzaniaAFRICAN JOURNAL OF ECOLOGY, Issue 3 2009Mligo Cosmas Abstract Soil of the semi-arid Mbulu District is part of the tropical soils, covered with sparse trees, shrubs or grasses in which domestic grazing animals have prevented the wide spread of vegetation cover. The study aimed at determining soil organic carbon (OC), total nitrogen (N), available phosphorus (P) and the combined aboveground plant materials. Six study sites were established in which soil samples were collected at the depths of 0,5, 6,10 and 11,20 cm. Soil samples were analysed for OC, N and P as well as the levels of N and P in the combined aboveground materials of Panicum coloratum and Hyparrhenia filipendula. The percentage concentrations of OC, N and P were high in the top soil than in the deeper soil horizons. However, analysis of variance showed significant differences of OC in some sites whereas no difference for N and P between soil depth classes. OC was highly related with N and P along soil depth classes. It was concluded that the availability of N and P was because of the decomposition of organic matter in the soil. Soil N and P were highly related with the same in the combined aboveground plant materials. It was concluded that the increased concentration of N and P in the soil resulted into availability of the same in P. coloratum and H. filipendula. There was a very high variation in N and P among sites with different levels of intensity of grazing. It was concluded that grazing animals contributes to the redistribution of soil elements in the rangelands because they graze upon plant parts but the excreta are dropped away from the grazed spot. Résumé Le sol du district semi-aride de Mbulu fait partie de ces sols tropicaux couverts d'arbres, de buissons et d'herbes rares où le pâturage des animaux domestiques a empêché une large dispersion du couvert végétal. L'étude visait à déterminer le carbone organique (CO) du sol, l'azote (N) total, le phosphore (P) disponible et l'ensemble combiné de la matière végétale aérienne. Six sites d'étude furent établis, où l'on a récolté des échantillons de sol à des profondeurs de 0 à 5 cm, 6 à 10 cm, et 11 à 20 cm. Les échantillons de sols ont été analysés pour le CO, le N et le P ainsi que les niveaux de N et de P dans la matière végétale aérienne composée de Panicum coloratum et Hyparrhenia filipendula. Le pourcentage des concentrations de CO, N et P était plus élevé dans la couche supérieure du sol que dans les couches plus profondes. Cependant, une analyse de variance a révélé des différences significatives du CO dans certains sites alors qu'il n'y avait pas de différences pour N ni P aux différentes profondeurs de sol. Le CO était fortement liéà N et à P selon les classes de profondeur. On en a conclu que la disponibilité de N et de P était due à la décomposition de la matière organique dans le sol. Le N et le P du sol étaient fortement liés aux mêmes éléments présents dans la matière végétale aérienne combinée. On a conclu que la concentration accrue de N et de P dans le sol résultait de la concentration de ces mêmes éléments dans P. coloratum et H. filipendula. Il y a avait une très grande variation de N et de P entre des sites où l'intensité de pâturage était différente. On a conclu que les animaux qui pâturent contribuent à la redistribution des éléments du sol dans tous les endroits fréquentés étant donné qu'ils mangent des plantes à certains endroits mais que leurs excréments peuvent être rejetés ailleurs que les zones pâturées. [source] Phosphorus status on Canadian organic farmsJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 15 2007Ralph C Martin Abstract In eastern North America, many conventional livestock farms, especially dairy farms with high inputs of feed and fertiliser have excess soil phosphorus levels and an annual phosphorus surplus. However, a Canadian dairy farm in transition to organic, without fertiliser inputs reduced its farm P surplus to a marginal level. On long-term organic dairy farms in Ontario, most soils tested low to very low in available P as measured by a standard soil test. Canadian Prairie organic grain farms also consistently demonstrate deficiencies in available soil P. Organic producers have few viable alternatives for P management. Phosphate rock can be acceptable to organic standards (provided they are low in heavy metals, and not processed synthetically), but the P in these becomes available slowly, especially in high pH soils common on most organic farms in Canada. An alternative is to increase soil P availability. Enhanced microbial activity in organically managed soils may make P more available. Livestock manures are rich sources of available phosphorus, but a majority of organic farmers in Canada do not keep livestock. Off-farm manure sources are subject to organic regulations and hauling costs, both of which may be prohibitive. Furthermore, manure from conventional farms in Canada may be contaminated by genetically modified material from corn and soybean feed. Additional research is required to improve short-term availability of soil P and long-term replacement. Copyright © 2007 Society of Chemical Industry [source] Nutrient requirements of ephemeral plant species from wet, mesotrophic soilsJOURNAL OF VEGETATION SCIENCE, Issue 3 2001Emiel; Brouwer van der Meijden (1996) Abstract. Nanocyperion plant communities occur on wet, more or less nutrient-poor and sparsely vegetated soils in temperate climates and are characterized by tiny, very shortlived plant species. Most of these have become locally extinct. It is generally assumed that drainage and eutrophication were the most important reasons for this decrease. However, chemical analysis of soil pore water from plots on growth sites of these ephemerals showed that phosphorus availability was relatively high. In a greenhouse experiment, the growth of ephemeral species was strongly limited by the amount of available phosphorus, whereas there was little or no limitation to the growth of other plant species from this habitat. At low phosphorus concentrations, the ephemeral species reached their reproductive phase within the same period, but showed a strong reduction in the amount of flowers that were produced. We concluded that ephemeral species in particular require a minimum amount of phosphorus for reproduction. Other species on nutrient-poor, wet soils have a longer life span and can postpone flowering in nutrient-poor soils. In contrast to other short-lived plant species from the same habitat, the growth of ephemeral species was barely stimulated by enhanced nitrogen availability. Apparently, the ephemerals are adapted to low nitrogen concentrations. The occurrence on nitrogen-poor and relatively phosphorus-rich soils suggests that this community may be very sensitive to nitrogen deposition. Reduced phosphorus availability below the minimum requirements of ephemerals, for example after acidification or the exclusion of human activities, has possibly contributed to the decrease of ephemeral plant species. [source] Sediment-bound nutrient export from micro-dam catchments in Northern EthiopiaLAND DEGRADATION AND DEVELOPMENT, Issue 2 2008N. Haregeweyn Abstract The losses in soil nutrients (nitrogen (N), available phosphorus (Pav), organic carbon (OC), potassium (K), calcium (Ca) and magnesium (Mg)) in the catchment and the storage in the reservoir as a result of sediment delivery were assessed in 13 catchments/reservoirs in Tigray, Northern Ethiopia. This specifically dealt with factors controlling the losses, the fertility status of the deposited sediment, the nutrient export (NE) rates and associated costs. Enrichment ratio (ER) values >1 were observed for the plant nutrients and the finer soil fractions. The high ER is associated with the preferential transport of nutrients bound to finer soil fractions and the parent material dissolution and its transport via runoff. However, the fertility status of the deposited sediment is not sufficient by itself to support a sustainable crop growth and hence external addition is necessary, mainly for N and Pav fertilizer. Generally, rates of NE were high. The high OC export on the other hand dictates the potential of reservoir sediments for OC sequestration. The cost price of loss of only N and Pav, eroded from the catchment slopes, was estimated at ,34·2 million (Euros) in March 2006 for the Tigray. Pity enough, policy makers and beneficiaries do not realize the magnitude of the problem, which forms a major threat for the crop production in the country. Therefore, it is important not only to make the public aware of the problem but also of implementing integrated soil fertility management practices. Copyright © 2007 John Wiley & Sons, Ltd. [source] Land use legacies in post-agricultural forests in the Doupovské Mountains, Czech RepublicAPPLIED VEGETATION SCIENCE, Issue 2 2009Martin Kopecký Abstract Questions: Do differences in previous land use cause long-lasting changes in soil chemistry? Is vegetation composition affected by the previous land use after 50 years of secondary succession? Is the effect of previous land use caused by pre-existing differences in environmental conditions or mediated through changes in soil chemistry? How important is the effect of previous land use in relation to other factors? Location: Doupovské Mountains, Czech Republic. Methods: A stratified random sampling design was used to collect 91 vegetation relevés with accompanying soil samples. The effects of previous land use (arable field, meadow, pasture) on soil pH, organic carbon (C), total nitrogen (N), C:N ratio and available phosphorus were tested by an analysis of covariance. A canonical correspondence analysis and variation partitioning procedure were used to reveal relationships among previous land use, environmental factors and species composition. Results: Organic C, total N and C:N ratio were significantly influenced by previous land use, while available phosphorus and soil pH were not. Previous land use explained a significant part of the variation in species composition and its effects only partly overlapped with the effects of soil chemistry and terrain attributes. However, the species composition of post-agricultural forests was mostly determined by environmental factors not modified by previous land use. Conclusions: Forest communities that originate on abandoned agricultural land are primarily determined by natural environmental conditions. Nevertheless, the type of previous land use also modifies the species assemblages of these forests and needs to be considered as an important determinant of their composition. [source] Phosphorus requirement of Catla (Catla catla Hamilton) fingerlings based on growth, whole-body phosphorus concentration and non-faecal phosphorus excretionAQUACULTURE RESEARCH, Issue 2 2009Krishna Sukumaran Abstract A 120-day feeding trial was conducted to determine the dietary requirement of phosphorus for Indian major carp, catla (Catla catla) fingerlings. Four hundred and eighty fingerlings (mean body weight: 4.23±0.87 g) were randomly distributed among eight treatment groups with three replicates each. Eight isonitrogenous and isocaloric semi-purified diets (crude protein: 35% and crude lipid: 8.5%) were formulated with graded levels of phosphorus using KH2PO4 (T1: control, 0.1%; T2: 0.3%; T3: 0.5%; T4: 0.7%; T5: 0.9%; T6: 1.1%; T7: 1.3%; T8: 1.5%) and fed to the respective groups. Twenty fish were stocked in 150 L plastic tanks and fed to apparent satiation twice a day. Specific growth rate (SGR) significantly (P<0.05) increased with increasing dietary phosphorus concentration from 0.73% to 1.27%, after which there was a slight decline in growth at 1.1% available phosphorus (aP) and remained constant thereafter. The quadratic broken-line model based on growth was Y=317.5,581(0.64,x) (0.64,x); R2=0.73. Moisture and crude protein contents of whole body were similar among all the treatments. However, the ether extract in T1 group was significantly (P<0.05) higher than all the other treatments. The whole-body phosphorus content increased significantly (P<0.05) with an increase in phosphorus in the diets. The one-slope broken-line model based on whole-body phosphorus concentration was Y=4.07,1.63 (0.71,x); R2=0.48. The one-slope broken-line model for non-faecal phosphorus excretion as inorganic phosphorus (Pi) for 24 h revealed a trend of Y=12.67+73.96 (x,0.6); R2=0.81. Minimum aP requirements based on weight gain (%), whole-body phosphorus content and phosphorus excretion were 0.64%, 0.71% and 0.6%, respectively. Hence, the dietary aP requirement of catla fingerlings ranges from 0.6% to 0.71%. [source] | |||||||||||||