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1.
Humic substances improve the efficiency of different iron (Fe) sources overcoming Fe deficiency chlorosis of plants. However, applied at high rates, they can promote negative effects on plants. The main objective of this work was to study the potential adverse effect of three humic acids from different origin when they were applied with two effective Fe sources for plants: Fe- ethylenediaminedihydroxyphenylacetic acid (EDDHA) and Vivianite. To this end, an experiment with lupin (Lupinus albus L.) was performed involving two factors: (i) Fe source, and (ii) humic substances from three different origin (composted cork, leonardite, and compost obtained from a mixture of olive husk with cotton gin trash) applied at 0, 0.1, and 0.5 g organic carbon (C) kg?1 of growing media. At the rates used, humic substances promoted adverse effects on plant development, chlorophyll meter readings, and Fe content in lupin grown in calcareous media. Overall, the effect on dry matter and Fe content in plants was more relevant when Fe was supplied with Vivianite, the effect on chlorophyll meter readings being more significant when Fe was applied as Fe-EDDHA. Differences were also observed depending on the source of humic substances, those from leonardite promoting the greatest decrease in dry matter in roots and shoots. These humic substances possessed the highest values of spectroscopy index for aromaticity (A254 ). On the other hand, the application of humic substances from olive husk compost, which exhibited the lower aromaticity index, resulted in the smallest decrease in dry matter production and chlorophyll meter readings. Dry matter in roots decreased logarithmically with increased values of the estimates of the amounts of aromatic compounds accumulated in the growing media (R2 = 0.92; P < 0.01) with Vivianite as Fe source. Thus, the effects decreasing dry matter production, particularly in roots, and chlorophyll meter readings can be ascribed at least partially to the presence of phytotoxic aromatic compounds in humic substances.  相似文献   
2.
Cattle in western Uruguay that were eating Solanum bonariense developed periodic episodes of ataxia, hypermetria, hyperesthesia, head and thoracic limb extension, opisthotonus, nystagmus, and falling to the side or backward. Similar clinical signs were experimentally reproduced in cattle by administration of S. bonariense via rumen cannula at a dose of 1,024 g/kg body mass. No significant gross lesions were observed in field cases or experimentally induced cases. Spontaneous and induced histologic lesions were similar and included vacuolation, degeneration, and loss of Purkinje cells. Axonal spheroids, microcavitations, and other changes of wallerian-type degeneration in cerebellar white matter were also observed. Ultrastructural changes included increased number of electron-dense residual storage bodies in membrane-bound vesicles in affected Purkinje cells, and similar vesicles and mitochondria in axonal spheroids. No histologic lesions were detected in the other examined tissues. The Purkinje-cell swelling and vacuolation with subsequent cerebellar degeneration are suggestive of Purkinje-cell specific toxin that produces abnormal lysosome function and cell specific axonal transport. This is the first report of S. bonariense toxicity.  相似文献   
3.
Developing a magnetic tracer to study soil erosion   总被引：6，自引：0，他引：6  
Soil erosion is commonly measured as the quantity of sediment leaving a plot or watershed. The techniques for measuring soil erosion patterns and sediment redistribution within plots or watersheds by direct monitoring are very limited. The objective of this study was to develop a direct and non-intrusive tracer method to study the sources, patterns and rates of erosion and deposition of sediments in erosion plots. The magnetic tracer developed in this study consisted of polystyrene plastic beads embedded with a magnetic powder (magnetite). The “magnetized” beads, with a mean weight diameter of 3.2 mm and particle density of about 1.2 g cm−3, were uniformly mixed with soil and tested in the laboratory using simulated rainfall and inflow studies to simulate the interrill and rill components of soil erosion, respectively. In the interrill and rill experiments, the tracer was transported in the same proportion it was initially mixed with the soil. Given this fact, a magnetometer, which measures the soil's magnetic susceptibility, could be used to identify areas of deposition or detachment. The magnetic susceptibility would be increased or reduced depending on whether deposition or detachment occurs. To simulate detachment and deposition, a magnetometer was tested for different tracer concentrations and different thickness of soil containing the tracer. The magnetometer promises to be a sensitive, accurate, and useful tool to study the spatial variation of soil erosion when magnetic tracers are used.  相似文献   
4.
Apparent digestibility coefficients (ADCs) for dry matter (ADCdm) and crude protein (ADCcp) of selected feed ingredients were determined in vivo for grouper using passive faeces collection (Guelph System). A reference diet (RF) and test diets (consisted of 70% RF and 30% test ingredient) with 1% Cr2O3 as an inert indicator were used. An RF contained 45% protein, 10% fat and 15.7 kJ g?1 metabolizable energy. Three isonitrogenous and isocaloric diets, each contained a test ingredient (white fish meal, white cowpea meal and ipil‐ipil leaf meal), were used in a growth study based on ADCcp of feed ingredients. An RF without Cr2O3 was a control. The ADC values of experimental diets were also determined. In grouper, the ADCdm of white cowpea meal, defatted soybean meal, wheat flour and shrimp meal (74–76%) were significantly lower than that of squid meal (99%), but comparable with those of the fish meals (84–89%). No significant difference was observed between the ADCdm of ipil‐ipil leaf meal, rice bran and wheat flour (56–73%). The ADCcp of white cowpea meal and defatted soybean meal were similar to those of the fish meals, squid meal and shrimp meal (94–99%). The ADCcp of wheat flour was comparable with that of ipil‐ipil leaf meal (79–83%). Rice bran had the lowest ADCcp value of 43%. Based on specific growth rate (SGR), the growth of fish fed white cowpea meal‐based diets was similar to that of the control fish (3.2–3.3% day?1). Also, no significant difference was observed between the ADCdm (68–72%) and ADCcp (88–91%) of white cowpea meal‐based diet and the control diet. The results suggest that ADC values can be used as indicators to determine the nutritional value of feed ingredients. White cowpea meal can be incorporated as a protein source in practical diet for grouper at 20.5% of the diet with no adverse effect on growth.  相似文献   
5.
Vegetation patches in arid and semiarid areas are important in the regulation of surface hydrological processes. Canopy and ground covers developed in these fertility islands are a natural cushion against the impact energy of rainfall. Also, greater levels of organic matter improve the soil physicochemical properties, promoting infiltration and reducing runoff and soil erosion in comparison with the open spaces between them. During the 2006 rainy season, four USLE-type plots were installed around representative vegetation patches with predominant individual species of Huisache (Acacia sp), Mesquite (Prosopis sp), Prickly Pear or Nopal (Opuntia sp) and Cardon (Opuntia imbricata), to evaluate soil erosion and runoff, in semiarid Central Mexico. A comparative bare surface condition (Control) was also evaluated. Vegetative canopy and ground cover were computed using digital images. Selected soil parameters were determined. Soil erosion was different for the studied vegetation conditions, decreasing as canopy and ground cover increased. There were not significant differences in runoff and soil erosion between the Control and O.imbricata surfaces. Runoff was reduced by 87%, 87% and 98% and soil loss by 97%, 93%, and 99% for Acacia farnesiana, Prosopis laevigata and Opuntia sp, respectively, as compared to the Control. Soil surface physical conditions were different between the low vegetation cover conditions (Control and O.imbricata surfaces) and the greater vegetation cover conditions (A.farnesiana, P.laevigata and Opuntia sp), indicating a positive effect of vegetation patches on the regulation of surface hydrological processes.  相似文献   
6.
Organic amendments improve the quality of degraded cultivated agricultural soils. In this work, we examined the impact of an olive husk compost (OHC) on quality‐related physical, chemical and biochemical properties of intensively managed greenhouse soil. To this end, a completely randomized block experiment involving a single factor and two treatments (viz., annual application of OHC at 30 Mg ha−1 or no application) with three replications was used for 5 years. The effect of the compost was studied at two soil depths (0–10 and 10–25 cm) and two positions relative to crop rows (viz., on rows and between rows). Application of OHC increased soil organic matter (SOM) content, which is consistent with the low degradation rate of the compost in soil and confirms its usefulness as a source of organic C for soil. Increased SOM content resulted in decreased bulk density, and also in increased porosity and available water in the soil. The amendment was also an effective source of nutrients, particularly N, P, K and Ca, the last of which contributed to decrease exchangeable Na levels in the soil surface layer. The compost increased the activity of all enzymes studied except urease. This result can be ascribed to increased microbial activity, the presence of enzymes in the compost and their stabilization by organic matter and clay in the soil. Dehydrogenase and phosphatase were the individual enzyme activities in the soil, which were correlated with the largest number of soil properties favourably affected by OHC. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
7.
Nutrient deficiencies usually constrain the use of some composted materials as peat-substitute growing media even if some fertilizer is applied to the media. In this work, we assessed the suitability of various composted materials as such or mixed with peat for potted plant production, with special emphasis on their effects on nutrient availability to plants. Further, we examined the effect of vivianite [Fe3(PO4)2·8H2O] as a fertilizer and its mixture with humic substances (HS) on these growing media (particularly their effectiveness in preventing Fe deficiency chlorosis in alkaline substrates). A completely randomized experiment design was developed involving the growth of gerber (Gerbera jamesonii H. Bolus) and two factors, namely (i) the growing medium, specifically composted cork residue (C), compost obtained from a mixture of olive husk and cotton gin trash mixed with rice hulls and peat in a 1:1:1 volume proportion (OH), composted grape marc (GM), Sphagnum peat mixed with spent mushroom compost (M), coconut fibre (CF), and Sphagnum peat; and (ii) the Fe source (control without Fe, Fe-EDDHA, vivianite and vivianite + HS in a weight ratio of 10:1).  相似文献   
8.
The main objective of this work was to study the influence of humic substances (HS) on the effectiveness of Fe sulfate and Vivianite in preventing Fe chlorosis in white lupin with a view of performing cost-effective methods to overcome the problem. Two consecutive crops were performed using calcareous sand treated with different Fe sources (FeSO4·7H2O and Vivianite, at three different rates, and Fe-EDDHA) and five HS rates. Vivianite was more effective and persistent than Fe sulfate in increasing Soils and Plant Analysis Development (SPAD) readings and lupin yield expressed as dry matter (DM), probably due to the type of alteration products formed upon Vivianite oxidation. The effect of Fe sulfate and Vivianite in preventing Fe chlorosis was significantly increased by HS, and the best results were obtained with Vivianite and HS applied at 0.32 g Fe kg−1 and 0.06 g kg−1 growing media, respectively. SPAD readings with this treatment accounted for 85% and 70% of those obtained with Fe-EDDHA in the first and second crop, respectively, whereas DM production was greater with the Vivianite + HS treatment than with Fe-EDDHA. These results showed the potential effectiveness of treatments based on the application of Vivianite and HS in overcoming Fe chlorosis. However, HS applied with Fe sources at rates of 0.5 and 1 g kg−1 growing media decreased SPAD readings and plant yield. These positive and negative effects of HS in preventing Fe chlorosis were more evident with Fe sulfate and Vivianite than with chelated Fe, probably due to the effect of HS on the solubility of Fe forms of the growing medium.  相似文献   
9.
This research identifies favorable areas for goat production systems in the state of Veracruz, Mexico. Through the use of the analytic hierarchy process, layers of biophysical and soil information were combined to generate a model of favorability. Model validation was performed by calculating the area under the curve, the true skill statistic, and a qualitative comparison with census records. The results showed the existence of regions with high (4494.3 km2) and moderate (2985.8 km2) favorability, and these areas correspond to 6.25 and 4.15%, respectively, of the state territory and are located in the regions of Sierra de Huayacocotla, Perote, and Orizaba. These regions are characterized as mountainous and having predominantly temperate-wet or cold climates, and having montane mesophilic forests, containing pine, fir, and desert scrub. The reliability of the distribution model was supported by the area under the curve value (0.96), the true skill statistic (0.86), and consistency with census records.  相似文献   
10.
The effect of high dietary protein intake on proteolytic enzyme activity of feeding juvenile Asian sea bass, Lates calcarifer (Bloch) was studied. Ninety fish [mean body weight ± standard error (SE) 304.62 ± 34.84 g] were randomly assigned to two dietary treatments, each with three replicates. In treatment 1, fish were fed by‐catch (Thunnus albacares) and in treatment 2, a formulated diet containing 50% protein. Proteolytic enzyme activity was determined in pyloric caecae and intestine at day 0, 7, 15, and 30. Initial proteolytic enzyme activity in sea bass ranged from 174 to 232 azocasein units (UAC.) per mg of protein. After 7 days there was no significant difference in proteolytic enzyme activity of fish fed the two diets. However, a marked increase was observed in fish fed the formulated diet at day 15. After 30 days, the proteolytic enzyme activity in fish fed the formulated diet was threefold higher than that in fish fed the by‐catch diet. Fish fed the formulated diet had significantly higher total protein intake at day 7 than did fish fed by‐catch. Thereafter, a twofold weekly increase in the total protein intake was observed in both fish fed the by‐catch and formulated diets until day 30. These results suggest that a high dietary protein intake induces increased proteolytic enzyme activity in Asian sea bass.  相似文献   
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