Nutrient losses through prescribed burning of aboveground litter and understorey in dry dipterocarp forests of different fire history     

Kobsak Wanthongchai  Jürgen Bauhus  Johann G. Goldammer 《CATENA》2008

Anthropogenic burning in dry dipterocarp forests has become a common practice throughout Thailand. It is feared, that too frequent fires may result in a loss of soil fertility and thus ecosystem productivity. The aim of this study was to quantify aboveground nutrient pools in fine fuels and nutrient losses during prescribed fires applied to plots of different fire frequency histories in the Huay Kha Khaeng Wildlife Sanctuary, Thailand. Fire frequency was determined from satellite images and ranged from frequent, infrequent, rare and unburned with fire occurrences of 7, 2, 1 and 0 out of the past 10 years, respectively. Element losses were calculated as the difference between nutrient pools in the fuel before burning and the post-burning residues comprising ash, charcoal, and unburned matter, which were recovered quantitatively using aluminium trays. The percent nutrient loss was highest at sites that had undergone frequent burning in the past and was lowest at infrequently burned sites. When viewed over a ten-year period, nutrient losses from a fire regime with one fire per decade had much lower losses than the more frequent fire occurrences. Frequent fires in these forests promoted a grassy understorey, and there appeared to be a positive feedback of fire frequency on nutrient losses, because the fine fuel consumption through fire was higher in the grassy understorey than in previously less frequently burned understoreys. A comparison between estimates of ecosystem nutrient inputs and fire-related losses of N, P, Ca, and K associated with burning regimes representing 7, 3, and 1 fire per decade showed that the frequent recurrence of fire will lead to a long-term depletion of P, Ca, and K, and probably also N. Owing to the relatively low fine fuel accumulation following fire, which reached a maximum of ca. 12 t ha^− 1 after ca. 10 years, prescribed fires can be carried out at longer intervals such as once per decade in a safe manner to conserve nutrients on site.  相似文献   

Effect of land use on some soil properties related to the risk of loss of soil phosphorus     

F. Troitio  F. Gil‐Sotres  M.C. Leirs  C. Trasar‐Cepeda  S. Seoane 《Land Degradation \u0026amp; Development》2008,19(1):21-35

Although land use clearly modifies soil properties, the intensity of the modifications depends on the management procedures and also on the soil properties themselves. To enable construction of models that describe soil nutrient losses, extensive databases corresponding to soils under different land use must be made available. Analysis of 404 samples of soils (from Galicia, NW Spain), under different types of use revealed that most of the soil properties underwent changes in the following order: forest use (least modified) ‐ grassland ‐ arable (most modified). Decreases in the contents of organic matter, extractable oxides and P‐adsorption capacity followed the same order, as did increases in the contents of available P (total, inorganic and organic), P desorbed with distilled water, and degree of P saturation. In general, in all of the soils, independently of their use, the amount of P desorbed (whether total P, molybdate reactive P or particulate P) was more closely related to the degree of P saturation than to the levels of P extracted with bicarbonate. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Efficiency of wheat straw mulching in reducing soil and water losses from three typical soils of the Loess Plateau,China     

《国际水土保持研究(英文)》2019,7(4):335-345

Mulching the soil surface with a layer of plant residue is considered an effective method of conserving water and soil because it increases water infiltration into the soil, reduces surface runoff and the soil erosion, and reduces flow velocity and the sediment carrying capacity of overland flow. However, application of plant residues increases operational costs and so optimal levels of mulch in order to prevent soil and/or water losses should be used according to the soil type and rainfall and slope conditions. In this study, the effect of wheat straw mulch rate on the total runoff and total soil losses from 60-mm simulated rainstorms was assessed for two intensive rainfalls (90 and 180 mm h⁻¹) on three slope gradients typical conditions on the Loess Plateau of China and elsewhere. For short slopes (1 m), the optimal mulch rate to save water for a silt loam and a loam soil was 0.4 kg m⁻². However, for a clay loam soil the mulch rate of 0.4 kg m⁻² would be optimal only under the 90 mm h⁻¹ rainfall; 0.8 kg m⁻² was required for the 180 mm h⁻¹. In order to save soil, a mulch rate of 0.2 kg m⁻² on the silt loam slopes prevented 60%–80% of the soil losses. For the loam soil, mulch at the rate of 0.4 kg m⁻² was essential in most cases in order to reduce soil losses substantially. For the clay loam, 0.4 kg m⁻² may be optimal under the 90 mm h⁻¹ rain, but 0.8 kg m⁻² may be required for the 180 mm h⁻¹ rainstorm. These optimal values would also need to be considered alongside other factors since the mulch may have value if used elsewhere. Hence doubling the optimal mulch rate for the silt loam soil from 0.2 kg m⁻² or the clay loam soil under 90 mm h⁻¹ rainfall from 0.4 kg m⁻² in order to achieve a further 10% reduction in soil loss needs to be assessed in that context. Therefore, Optimal mulch rate can be an effective approach to virtually reduce costs or to maximize the area that can be treated. Meantime, soil conservationist should be aware that levels of mulch for short slopes might not be suitable for long slopes.  相似文献   

Estimation of protein requirement for maintenance in adult parrots (Amazona spp.) by determining inevitable N losses in excreta     

Westfahl C  Wolf P  Kamphues J 《Journal of animal physiology and animal nutrition》2008,92(3):384-389

Especially in older pet birds, an unnecessary overconsumption of protein--presumably occurring in human custody--should be avoided in view of a potential decrease in the excretory organs' (liver, kidney) efficiency. Inevitable nitrogen (N)-losses enable the estimation of protein requirement for maintenance, because these losses have at least to be replaced to maintain N equilibrium. To determine the inevitable N losses in excreta of adult amazons (Amazona spp.), a frugivor-granivorous avian species from South America, adult amazons (n = 8) were fed a synthetic nearly N-free diet (in dry matter; DM: 37.8% starch, 26.6% sugar, 11.0% fat) for 9 days. Throughout the trial, feed and water intake were recorded, the amounts of excreta were measured and analysed for DM and ash content, N (Dumas analysis) and uric acid (enzymatic-photometric analysis) content. Effects of the N-free diet on body weight (BW) and protein-related blood parameters were quantified and compared with data collected during a previous 4-day period in which a commercial seed mixture was offered to the birds. After feeding an almost N-free diet for 9 days, under the conditions of a DM intake (20.1 g DM/bird/day) as in seeds and digestibility of organic matter comparable with those when fed seeds (82% and 76% respectively), it was possible to quantify the inevitable N losses via excrements to be 87.2 mg/bird/day or 172.5 mg/kg BW(0.75)/day. Assuming a utilization coefficient of 0.57 this leads to an estimated protein need of approximately 1.9 g/kg BW(0.75)/day (this value does not consider further N losses via feathers and desquamated cells; with the prerequisite that there is a balanced amino acid pattern).  相似文献   

Pre-cecal phosphorus digestibility for corn,wheat, soybean meal,and corn gluten meal in growing Japanese quails from 28 to 32 d of age     

《动物营养（英文）》2019,5(2):148-151

The optimization of dietary phosphorus (P) depends on precise details of the P availability in feed ingredients to avoid excess or deficient P in a mixed diet. This study was carried out to measure the apparent ileal digestibility of P for corn, wheat, soybean meal, and corn gluten meal in growing Japanese quails from 28 to 32 d posthatch. A total of 400 quail chicks were randomly distributed across 5 treatments with 4 replicates and 20 birds in each floor pen. The P-free diet (PFD) was formulated based on cornstarch to measure the basal endogenous P losses (EPL). Digestibility coefficients were determined by ileal digesta sampling using TiO₂ as an indigestible marker. The EPL was estimated at 384 mg/kg DMI. The apparent ileal P digestibility (AIPD) for corn, soybean meal, wheat, and corn gluten meal were determined to be 0.38, 0.53, 0.38, and 0.78, respectively. The corresponding values for true ileal P digestibility (TIPD) were 0.48, 0.61, 0.50, and 0.83, respectively. The t-test analysis showed that the difference of AIPD and TIPD values for corn (P = 0.031) and wheat (P = 0.015) were statistically significant, however, no significant differences were observed for corn gluten meal (P = 0.318) and soybean meal (P = 0.104). In conclusion, the correction of AIPD coefficients for EPL in low-P ingredients such as corn and wheat may be much more important than that in high-P feedstuffs such as corn gluten meal and soybean meal in growing quails.  相似文献   

Variation in seed protein digestion of different pea (Pisum sativum L.) genotypes by cecectomized broiler chickens: 1. Endogenous amino acid losses, true digestibility and in vitro hydrolysis of proteins     

I. Gabriel  M. Lessire  H. Juin  J. Burstin  G. Duc  L. Quillien  J.N. Thibault  M. Leconte  J.M. Hallouis  P. Ganier  N. Mzire  B. Sve 《Livestock Science》2008,113(2-3):251-261

The aim of this study was to investigate the cause of variation in the digestibility of pea protein in poultry and to find a tool to select genotypes with high digestibility potential by using an in vitro hydrolysis assay. Eight pea genotypes were selected for their difference in seed protein content and composition. To reduce the variation due to tannins and particle size, seeds from these 8 genotypes were dehulled and micro-ground. They were incorporated as the only protein source in 8 different experimental isoproteinaceous diets with similar metabolisable energy content. The amino acid digestibility was studied in cecectomized chickens. A balance method was used to obtain apparent digestibility, and the isotope dilution technique was used to determine endogenous losses and true digestibility, after feeding a double labelled test meal containing chromic oxide and ¹⁵N-labelled peas. The 8 diets showed differences in apparent amino acid digestibility. The average apparent digestibility for all amino acids varied between 79.5 and 86.3%, with the highest values for arginine (85.2 to 90.8%) and glutamic acid (85.2 to 90.5%), and the lowest values for cystine (63.3 to 69.7%) and tryptophan (69.1 to 80.3%). This variability of apparent amino acid digestibility was due to variations in endogenous losses and true digestibility among the 8 pea genotypes. The average endogenous losses as determined for 9 amino acids ranged from 3.6 to 5.4% of ingested amino acids, with the highest value for threonine (8.0 to 11.0%). The average true digestibility varied between 84.4 and 90.2%, with the highest values for lysine (89.0 to 95.0%), and the lowest for isoleucine (81.0 to 88.7%) and valine (82.4 to 88.7%). In vitro hydrolysis of protein from micro-ground seeds was performed for the 8 pea genotypes using three proteases (pepsin, trypsin and chymotrypsin). The quantity of small peptides (< 3 kDa) that appeared after the combined hydrolysis with pepsin (3 h) followed by trypsin and chymotrypsin (15 min) was significantly correlated with the average true digestibility of the 8 genotypes (R = 0.74; P < 0.05).  相似文献   

Soil phosphorus management and water quality: a UK perspective   总被引：23，自引：0，他引：23  

A. C. Edwards  P. J. A. Withers 《Soil Use and Management》1998,14(S4):124-130

Abstract. An increasing proportion of P reaching surface waters appears to be derived from agricultural land; apportioning the relative contribution to particular farming systems is not straightforward. The majority of farms in the UK operate on the basis of an annual agricultural P surplus, the size of which varies across different farm types. Particularly high values (>20kg ha^-1) are commonly associated with intensive-livestock production and the lower values (<10kg P ha^-1) with arable farms. The geographical divide between the predominance of arable cropping in the east and livestock enterprises in the west of the UK should result in an uneven pattern to the distribution of annual P surplus. The expected cumulative effects of this surplus should be a noticeable increase in total and extractable soil P concentrations, but this is not readily apparent. While evidence from experimental plots suggests a relationship between the concentration of available soil P and that present in drainage waters, extrapolating this information so that it can be useful at the scale of a whole catchment is difficult. The loss of P from agricultural land is controlled by factors which are independent of the size of the annual P surplus. The pattern of P cycling, together with the dominant loss pathways, differ greatly between livestock and arable farming systems. Proportioning the contributions that either increased soil erosion arising from changing agricultural practices or the cumulative effect of a P surplus have had upon P loss is a necessary prerequisite to effective management.  相似文献   

Phosphorus losses from arable land in England   总被引：7，自引：0，他引：7  

J. A. Catt  K. R. Howse  R. Farina  D. Brockie  A. Todd  B. J. Chambers  R. Hodgkinson  G. L. Harris  J. N. Quinton 《Soil Use and Management》1998,14(S4):168-174

Abstract. Concentrations and annual loadings of molyhdate reactive P (MRP) and total (including particulate) P (TP) are reported from field drainage, catchment and erosion experiments in England. Annual losses through field drains and in catchment runoff were 0.037-0.74 kg MRP/ha and 0.37-2.64 kg TP/ha, but those in surface runoff from experimental plots measuring erosion were generally much greater (often > 3 kg MRP/ha and up to 32 kg TP/ha in a wet year). Amounts of TP in drainflow and catchment runoff depended upon factors influencing soil dispersibility, such as particle size distribution and calcium carbonate content. The results to date suggest that P losses in surface runoff and erosion from arable fields to water are best limited by: (a) maximizing crop cover, using minimal cultivation practices and where possible planting crop rows across rather than up and down the slope, (b) avoiding cultivation practices that result in dispersion of soil particles, and (c) avoiding application of P fertilizer to wet soils when rainfall is likely soon after application. Consideration should he given to maintaining field drains below peak efficiency to reduce subsurface P losses.  相似文献   

Phosphorus loss from agricultural catchments: pathways and implications for management     

P. J. Johnes  R. A. Hodgkinson 《Soil Use and Management》1998,14(S4):175-185

Abstract. The contribution non-point P sources make to the total P loading on water bodies in agricultural catchments has not been fully appreciated. Using data derived from plot scale experimental studies, and modelling approaches developed to simulate system behaviour under differing management scenarios, a fuller understanding of the processes controlling P export and transformations along non-point transport pathways can be achieved. One modelling approach which has been successfully applied to large UK catchments (50-350km² in area) is applied here to a small, 1.5 km² experimental catchment. The importance of scaling is discussed in the context of how such approaches can extrapolate the results from plot-scale experimental studies to full catchment scale. However, the scope of such models is limited, since they do not at present directly simulate the processes controlling P transport and transformation dynamics. As such, they can only simulate total P export on an annual basis, and are not capable of prediction over shorter time scales. The need for development of process-based models to help answer these questions, and for more comprehensive UK experimental studies is highlighted as a pre-requisite for the development of suitable and sustainable management strategies to reduce non-point P loading on water bodies in agricultural catchments.  相似文献   

Mitigation options for diffuse phosphorus loss to water   总被引：4，自引：0，他引：4  

P. J. A. Withers  S. C. Jarvis 《Soil Use and Management》1998,14(S4):186-192

Abstract. Agriculture contributes significant loads of P to surface waters. The reductions in these diffuse P inputs necessary to help prevent eutrophication problems and/or assist in the restoration of water quality will require controls over both nutrient inputs and their subsequent transport in land runoff. Specific mitigation options include nutrient budgeting, input management, soil conservation, land use management and the establishment of riparian, and other buffer zones. The variable nature of diffuse P loss suggests that the best approach to control is through integrated management at a range of scales. Critical control concepts at the farm level include targeting source areas adequately, maintaining P input loading rates within recommended limits and avoiding high-risk management actions. Since eutrophication is a natural phenomenon and with potential conflicts with the need to meet production targets and/or minimize loss of other nutrients (N), some assessment of acceptable levels of P loss, of cost effectiveness of options and some prioritization of goals are necessary to find optimal solutions. As the requirements of individual waterbodies differ, these solutions need to be site specific and their successful adoption requires an appreciation by farmers of the importance of minimizing agricultural P loss both as individuals and collectively within a catchment.  相似文献