Soil Nutrient Accumulation Research Articles

Influence of shifting flow paths on nitrogen concentrations during monsoon floods, San Pedro River, Arizona

Hydrologic flow paths control transport, and therefore are a major constraint on the cycling and availability of nutrients within stream ecosystems. This control is particularly evident in semiarid streams, where hydrologic connectivity between stream, riparian, and upland systems increases greatly during storms in the rainy season. We measured chloride concentrations in base flow, precipitation, soil water, and stream water to quantify the hydrologic connectivity and solute flux between soil water, groundwater, and the stream channel during six summer floods in 2001 (a wet year; 25 cm winter rain) and 2002 (a dry year; 5 cm winter rain) in the San Pedro River, southeastern Arizona. This hydrologic information was used to evaluate observed patterns in nitrate, dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) concentrations in floods. The first floods of each year showed increased stream nitrate concentration that was approximately two orders of magnitude higher than base flow concentration. DOC consistently doubled to tripled during storm events, while DON in 2001 showed no response and showed a marked increase in 2002. A chloride mixing model indicated that soil and groundwater contributions to storm water discharge were related to antecedent conditions and to flood magnitude. Soil and groundwater contributions were the highest early in the 2001 monsoon season following the wet winter, much lower early in 2002 following a dry winter, and lowest during the largest floods of the 2002 monsoon season when flows were derived primarily from precipitation and overland flow. Stream water nitrate‐N concentrations during floods were consistently 0.2–0.5 mg/L higher in 2002 than during 2001, suggesting greater over‐winter accumulation of soil nitrate during the drier year. This result is consistent with higher mean nitrate‐N concentrations in soil water of the riparian zone in 2002 (3.1 mg/L) than in 2001 (0.56 mg/L). These data highlight the importance of seasonal and interannual variability of hydrology in semiarid regions, and the role of water availability in driving patterns of soil nutrient accumulation and their transport to the stream.

Freshwater input structures soil properties, vertical accretion, and nutrient accumulation of Georgia and U.S tidal marshes

To identify relationships between freshwater input and marsh soil properties, measurements of bulk density, nutrients (carbon [C], nitrogen [N], phosphorus [P]), accretion, and accumulation were compared in tidal marshes of three estuaries of Georgia that varied in delivery of freshwater. Soil organic C and N (0–30 cm) were two times greater in marshes of the freshwater‐dominated Altamaha River than in the salt marshes of Doboy Sound and Sapelo River. 137Cs accretion and accumulation of organic C and N were three to five times greater in freshwaterdominated marshes than in salt marshes. The patterns observed in Georgia marshes were geographically general; data for tidal freshwater and brackish marsh soils compiled from 61 studies in the conterminous United States showed lower bulk density and higher percent organic C and N than salt marshes, regardless of geographic region. Salinity, a proxy for freshwater input, was inversely correlated with percent soil organic C and N and with vertical accretion in Georgia marshes and in marshes elsewhere in the conterminous United States. There was no relationship between above‐ or belowground emergent plant production and salinity of Georgia marshes but the rate of root decomposition was positively related to salinity, and decomposition rate was negatively related to percent soil organic C and C accumulation. In Georgia tidal marshes and elsewhere, soil organic matter content and accumulation are mediated by freshwater through its effects on decomposition.

Nutritive Value and Nutrient Uptake of Sorghum–Sudangrass under Different Broiler Litter Fertility Programs

Broiler (Gallus gallus) litter fertility regimes and nutrient removal by sorghum–sudangrass [Sorghum bicolor (L.) Moench] are not well defined. The objective of this study was to determine broiler litter fertility regimes for sorghum–sudangrass that would maximize nutrient removal and produce comparable forage nutritive value compared with inorganic fertilizers while reducing potential soil nutrient accumulation. A randomized, complete‐block experiment with four replications and four treatments (litter applied at recommended nitrogen [N] rate [Litter‐N], recommended phosphorus [P] rate plus supplemental inorganic N [Litter‐P+N], recommended P rate [Litter‐P], and inorganic fertilizer [INORG]) was established. Acid detergent fiber (ADF), neutral detergent fiber (NDF), crude protein (CP), P, Cu, Fe, and Zn were determined. Treatments did not affect ADF, NDF, Cu, or Fe in 2001, whereas ADF and NDF were similar for INORG and Litter‐N in 2002. Greatest P concentrations were observed in Litter‐N and Litter‐P plots. Crude protein was greatest for INORG plots, similar for Litter‐P+N and Litter‐N treatments, and lowest for Litter‐P plots. Treatments affected Cu and Zn: Forage from Litter‐N plots contained 44% greater forage Cu than those from Litter‐P plots in 2003. Iron concentration for 2003 was 60% higher than for 2001 in Litter‐N plots, and there were 22% and 30% increases in P uptake in 2003 compared with 2001 for the Litter‐N and Litter‐P+N plots, respectively. Lower rates of broiler litter, applied based on the P requirement and supplemented with inorganic N, can produce similar forage nutritive value to that fertilized with inorganic fertilizer only or broiler litter applied to meet crop N requirements.

Sand barriers of straw checkerboards for habitat restoration in extremely arid desert regions

Many human exploitations and constructions, such as pipeline corridors, power transmission lines and transportation routes, suffer from damage due to sand transport and dune burial in arid desert regions. It is a challenge for ecologists to stabilize mobile dunes and to change them into stable productive ecosystems. The establishment of a straw checkerboard is one of the most effective methods of creating a sand barrier and has been employed since the 1950s in the arid desert regions of the world. In order to better understand its role in the process of ecological restoration, the environmental effects of a straw checkerboard were evaluated through field experimental observation. The results indicate that the straw checkerboard enhanced the capacity of dune systems to entrap dust deposition, leading to the accumulation of soil organic matter and nutrients and to the development of soil formation on the dune surface. The straw checkerboard increased the silt and clay content, thereby changing coarse soil texture to fine. This is one of the vital prerequisites for the invasion and establishment of herbaceous plants in desert ecosystems. When a straw checkerboard was used to stabilize the dunes before establishing sand-binding vegetation, significant differences in plant species richness, herbaceous cover, dust deposition, and soil physicochemical properties were found in this study. All of these findings suggest that the use of the straw checkerboard, as one of the key techniques for restoring desert ecosystems, will be an important component of efforts to further extend ecological engineering projects in arid desert regions.

Winter Cover Crop and Management Effects on Summer and Annual Nutrient Yields

Effluent from a swine (Sus scrofa domesticus) lagoon is often applied repeatedly to nearby fields because of logistical constraints and costs of transportation. To minimize accumulation of soil nutrients and sustain use of spray field, best management practices must maximize the rates of removal of manure nutrients. Research determined summer hay and nutrient yields of bermudagrass [Cynodon dactylon (L.) Pers.] following winter cover crops ‘Kenland’ red clover (Trifolium pratense L.), ‘Bigbee’ berseem clover (T. alexandrinum L.), or ‘Marshall’ annual ryegrass (Lolium multiflorum Lam.) subjected to five harvesting systems. Also, summer and winter forage yields were combined and analyzed to find best annual performance. Nutrient yields of bermudagrass were statistically affected by winter cover crop species and harvest date. Summer production was maximized following berseem clover harvested on a two‐harvest‐day system of 15 May and 1 June. Harvesting the winter cover crop in addition to the bermudagrass increased extraction of N (82%), P (76%), K (90%), Mg (95%), Mn (67%), Ca (158%), Fe (80%), Zn (83%), and Cu (97%). For environmentally sensitive nutrients N, P, Cu, and Zn, annual yields were maximized with a two‐harvest‐day system of 15 April and 1 June of a cover crop, which was not the best harvest system for either the winter or the summer trials in isolation. Tests on summer performance and winter performance in isolation were informative and did indicate the best winter cover crop species, berseem clover, but did not indicate the best management system for annual production.

Ecological risks of outdoor pig fattening in organic farming and strategies for their reduction—Results of a field experiment in the centre of Germany

Outdoor pig fattening in organic farming has become more popular over the past few years, due to benefits in relation to animal welfare and economical reasons. On the other hand, ecological risks like nutrient accumulation in soils and leaching of nitrate (N) into groundwater have been described and discussed in outdoor pig productions systems. The regulations of the national organic farming associations and the EEC directive limit nutrient inputs by stocking rates adapted to maximum nitrogen (N) loads of 112 and 170 kg ha−1, respectively and maximum phosphorus (P) loads of 43 kg ha−1 according to national regulations. N and P inputs and their distribution were calculated and measured under specific management strategies. In a field experiment at the experimental farm of Kassel University in central Germany with loessial and clayey soils. Ratios of concentrate and feed compositions were evaluated in relation to N and P inputs to soil. Moving of huts and troughs and weekly extended area for grazing were examined for their effects on nutrient distribution. Additionally, soil structure was assessed. The results indicate that with nutrient input and their distribution as a main feature of management, the ecological risks of nutrient accumulation and leaching can be kept on a tolerable level. Most relevant measures to reduce nutrient losses in outdoor pig production are: restrictions in the amount of concentrate offered to the pigs, supply with field fodder, avoidance of fodder loss, optimising the crop rotation to ensure that nutrients in the soil are used efficiently. Available field fodder has to be considered to reduce the ratio of concentrate additionally. Fodder loss should be avoided. Nutrients have to be taken out of the soil by following crops, as a result of integrating outdoor pig fattening into crop rotation. The distribution of N and P was homogenized by moving huts and troughs at short intervals and when paddocks were provided at weekly intervals as strip grazing. Due to the impact of pigs, the infiltration rate at soil surface was reduced at highly frequented areas around troughs and in front of huts, which were 1–10% of the paddocks’ size.

Influence of wood ash on soil chemical composition and biochemical parameters of young Scots pine

Short-term effects of different doses (0.25 and 0.5 kg m -2 ) of wood ash fertilization in a field experiment in a 20-year-old Scots pine stand on a nutrient-poor sandy soil (Arenosol) was studied in North Estonia. Soil chemical properties, nutrient accumulation, soluble carbohydrates, starch, hemicellulose, cellulose, and lignin were used as biochemical indicators for the assessment of the state of trees from 2000 until 2005. Changes in the soil upper horizon (30 cm) showed an increase in the pH and in the concentrations of K, Ca, B, Mg, and other elements, except N, after treatment. Statistical relationships were found between the doses of wood ash used in the treatment and the mineral composition of the soil. Changes in soil properties brought about changes in nutrient accumulation into trees and the needle diagnosis showed an essential increase in the K, Mg, Fe, Mn, and Zn concentrations in needles. No statistically significant changes were observed in the concentrations of soluble carbohydrate (tendency to decrease), starch (tendency to increase), and structural carbohydrates, but a somewhat higher accumulation of cellulose and lignin was registered in the needles of Scots pine. The effect of wood ash on carbohydrate metabolism and lignin synthesis seemed to depend on the seasonal development stage of needles and climatic conditions.

Long‐Term Effects of Sustained Beef Feedlot Manure Application on Soil Nutrients, Corn Silage Yield, and Nutrient Uptake

A field study was initiated in 1992 to investigate the long-term impacts of beef feedlot manure application (composted and uncomposted) on nutrient accumulation and movement in soil, corn silage yield, and nutrient uptake. Two application strategies were compared: providing the annual crop nitrogen (N) requirement (N-based rate) or crop phosphorus (P) removal (P-based rate), as well as a comparison to inorganic fertilizer. Additionally, effects of a winter cover crop were evaluated. Irrigated corn (Zea mays L.) was produced annually from 1993 through 2002. Average silage yield and crop nutrient removal were highest with N-based manure treatments, intermediate with P-based manure treatments, and least with inorganic N fertilizer. Use of a winter cover crop resulted in silage yield reductions in four of ten years, most likely due to soil moisture depletion in the spring by the cover crop. However, the cover crop did significantly reduce NO3-N accumulation in the shallow vadose zone, particularly in latter years of the study. The composted manure N-based treatment resulted in significantly greater soil profile NO3-N concentration and higher soil P concentration near the soil surface. The accounting procedure used to calculate N-based treatment application rates resulted in acceptable soil profile NO3-N concentrations over the short term. While repeated annual manure application to supply the total crop N requirement may be acceptable for this soil for several years, sustained application over many years carries the risk of unacceptable soil P concentrations.

Impacts of overgrazing and reclamation on soil resources in rangeland ecosystems in Huailai Basin, Heibei, China

The soil constituents and relations between the variation of soil resources and plant communities in three adjacent sites representing the overgrazing, reclamation and comparatively undusturbed communities respectively were quantified and examined in study are in Huailai Basin, Hebei Province, China. There have been significantly greater constituent of C, N, P in the soils of shrubland site. Corg, Ntotal, Navail and Paval were between 1. 18 and 3. 90 times more concentrated in the soils of shrubland site in comparison with the other two sites. Although the Ptotal concentration was lower in shrubland soils than in overgrazed rangeland soils, the Pavail concentration, however, was significantly greater in the soils of shrubland site comparing to those in the soils of rangeland and millet field sites. Among the three sites, CV exceeding 40% were found for SO4, Cl, and F ion. The CV of organic carbon also exceeded 40% but only in the soils of millet field site. The highest CV were found for F, SO4, ion in the soils of shrubland and overgrazed rangeland sites, while for Cl and SO4 ion in those of millet field site. The results also showed that the introductions of shrubs are of vital importance for the accumulation of soil nutrients and maintenance of soil fertilities, and also for the restoration and reconstruction of deseritified ecosystems.

Phosphorus accumulation in soils and nitrate contamination in underground water under export-oriented asparagus farming in Nong Ngu Lauem village, Nakhon Pathom province, Thailand

Asparagus fields in Nong Ngu Lauem village, Nakhon Pathom province, Thailand, were surveyed for the cultural practices adopted, yield, fertilizer use, nutrient accumulation in soils, and nitrate-nitrogen concentration of the underground water. In this village, asparagus is being cultivated under contract farming with a Japanese agribusiness company and 60% of the product is exported to Japan. Average application rates of nitrogen- and phosphorus-fertilizers were 840 kg N and 286 kg P ha−1 year−1, and less than 5% of the applied elements was recovered in the harvested products. Phosphorus accumulated in the surface 20 cm soil significantly, unlike N determined by the Kjeldahl method. Higher concentration of nitrate-nitrogen was detected down to 1-m depth in the asparagus fields compared with the adjacent sugarcane fields. Underground water samples were taken from 15 wells of the village and their content of nitrate-nitrogen was determined once a month during a period of 18 months. Nitrate-nitrogen was distributed unevenly among the wells, and no periodic peaks in the concentrations were detected. The highest value of 39 g nitrate-nitrogen m−3 was recorded.

Accumulation of nutrients in soils affected by perennial colonies of piscivorous birds with reference to biogeochemical cycles of elements

The accumulation of selected N, K, and P forms in soils within three perennial colonies of black cormorant ( Phalacrocorax carbo sinensis) and grey heron ( Ardea cinerea) located in northern and eastern Poland were investigated. Soil samples were collected beneath the nests from the most representative for each colony plots. Control samples were taken outside the colonies within sites adjacent to the nesting areas but not affected by bird excrement. From each genetic horizon (20 horizons) in soil profiles, a cumulative sample of about 25–30 kg of soil was taken for analysis. Nitrogen by Kjeldahl, ammonium ions (N NH 4 ), nitrates (N NO 3 ), exchangeable potassium (K ex), available potassium (K av), and available phosphorus (P av) were determined. The soils affected by birds demonstrated a very strong enrichment with N, K, and P in comparison to the control sites, especially in the topsoil horizons. The content of N NH 4 in individual soil horizons from the colonies was from 1.7 to 10.1 times higher than the respective control, N NO 3 from 2.9 to 215.7, K ex from 2.0 to 35.1, K av from 1.1 to 48.1, and P av in the range from 2.4 to 53.0 times. The highest increment of chemical elements was noticeable in the soils of territories inhabited by cormorants and the least in forest occupied by herons. Some relationships between soil texture and accumulation of biogenic nutrients were determined. Clay loam soil showed the greatest enrichment with analysed forms of elements with the exception of N NH 4 .

Nutrient Uptake in Plant Parts of Sixteen Forages Fertilized with Poultry Litter

Poultry litter used as fertilizer for forages often results in nutrient accumulation in soils over time. Maximizing nutrient uptake by forages would facilitate nutrient removal from litter‐treated soils when the plants are mechanically harvested. This study compared N, P, K, Cu, and Zn concentrations and distribution in plant parts of annual ryegrass (Lolium multiflorum Lam.) with 15 other cool‐season forages fertilized with poultry litter. Annual ryegrass, three cereals, and 12 legumes were seeded in a pasture at Collins, MS, on a Savannah fine sandy loam (fine‐loamy, siliceous, semiactive, thermic Typic Fragiudult) fertilized with poultry litter. Each species was harvested at full maturity and separated into root, stem, leaf, and flower components, and N, P, K, Cu, and Zn concentration and content of each component was determined. Most legumes had greater P, Cu, and Zn concentrations than annual ryegrass in many plant parts. Content of P, Cu, and Zn was similar between annual ryegrass and legumes due to greater dry matter yield of annual ryegrass compared with legumes. Stems, especially oat (Avena sativa L.) stems, had the lowest N/P ratio of all plant parts, which was more comparable to the N/P ratio of poultry litter. Nitrogen concentration was highly correlated with P, Cu, and Zn concentrations in aboveground plant parts, suggesting that improvements in N fertility would improve P, Cu, and Zn concentration in plants. To maximize P uptake in poultry litter–fertilized forages, management practices and breeding objectives should concentrate on optimizing stem production, while maintaining palatability, because almost 60% of total P in forages is located in stems.

Effects of Grazing on Restoration of Southern Mixed Prairie Soils

AbstractA comparative analysis of soils and vegetation from cultivated areas reseeded to native grasses and native prairies that have not been cultivated was conducted to evaluate restoration of southern mixed prairie of the Great Plains over the past 30 to 50 years. Restored sites were within large tracts of native prairie and part of long‐term grazing intensity treatments (heavy, moderate, and ungrazed), allowing evaluation of the effects of grazing intensity on prairie restoration. Our objective was to evaluate restored and native sites subjected to heavy and moderate grazing regimes to determine if soil nutrients from reseeded cultivated land recovered after 30 years of management similar to the surrounding prairie and to identify the interactive influence of different levels of grazing and history of cultivation on plant functional group composition and soils in mixed prairies. For this mixed prairie, soil nitrogen and soil carbon on previously cultivated sites was 30 to 40% lower than in uncultivated native prairies, indicating that soils from restored sites have not recovered over the past 30 to 50 years. In addition, it appears that grazing alters the extent of recovery of these grassland soils as indicated by the significant interaction between grazing intensity and cultivation history for soil nitrogen and soil carbon. Management of livestock grazing is likely a critical factor in determining the potential restoration of mixed prairies. Heavy grazing on restored prairies reduces the rate of soil nutrient and organic matter accumulation. These effects are largely due to changes in composition (reduced tallgrasses), reduced litter accumulation, and high cover of bare ground in heavily grazed restored prairies. However, it is evident from this study that regardless of grazing intensity, restoration of native prairie soils requires many decades and possibly external inputs to adequately restore organic matter, soil carbon, and soil nitrogen.

Nutrient Uptake in Plant Parts of Sixteen Forages Fertilized with Poultry Litter

Poultry litter used as fertilizer for forages often results in nutrient accumulation in soils over time. Maximizing nutrient uptake by forages would facilitate nutrient removal from litter-treated soils when the plants are mechanically harvested. This study compared N, P, K, Cu, and Zn concentrations and distribution in plant parts of annual ryegrass (Lolium multiflorum Lam.) with 15 other cool-season forages fertilized with poultry litter. Annual ryegrass, three cereals, and 12 legumes were seeded in a pasture at Collins, MS, on a Savannah fine sandy loam (fine-loamy, siliceous, semiactive, thermic Typic Fragiudult) fertilized with poultry litter. Each species was harvested at full maturity and separated into root, stem, leaf, and flower components, and N, P, K, Cu, and Zn concentration and content of each component was determined. Most legumes had greater P, Cu, and Zn concentrations than annual ryegrass in many plant parts. Content of P, Cu, and Zn was similar between annual ryegrass and legumes due to greater dry matter yield of annual ryegrass compared with legumes. Stems, especially oat (Avena sativa L.) stems, had the lowest N/P ratio of all plant parts, which was more comparable to the N/P ratio of poultry litter. Nitrogen concentration was highly correlated with P, Cu, and Zn concentrations in aboveground plant parts, suggesting that improvements in N fertility would improve P, Cu, and Zn concentration in plants. To maximize P uptake in poultry litter–fertilized forages, management practices and breeding objectives should concentrate on optimizing stem production, while maintaining palatability, because almost 60% of total P in forages is located in stems.

Comparison of Nutrient Accumulation in Greenhouse Soils before and after Introduction of Sustainable Agriculture

Comparison of Nutrient Accumulation in Greenhouse Soils before and after Introduction of Sustainable Agriculture

Sediment and nutrient accumulation in floodplain and depressional freshwater wetlands of Georgia, USA

Abstract Soil accretion, sediment deposition, and nutrient (N, P, organic C) accumulation were compared in floodplain and depressional freshwater wetlands of southwestern Georgia, USA to evaluate the role of riverine (2600 km2 catchment) versus depressional (<10 km2 catchment) wetlands as sinks for sediment and nutrients. Soil cores were collected from three floodplain (cypress-gum) and nine depressional (three each from cypress-gum forest, cypress-savannah, and herbaceous marsh) wetlands and analyzed for radionuclides (137Cs, 210Pb), bulk density, N, P, and organic C to quantify recent (30-year) and long-term (100-year) rates of sediment and nutrient accumulation. There was no significant difference in organic C, N, or sediment accumulation between depressional and floodplain wetlands. However, P accumulation was 1.5 to three times higher in the floodplain (0.12–0.75 g/m2/yr) than in the depressional wetlands (0.08–0.25 g/m2/yr). Sediment and nutrient accumulations were highly variable among depressional...

Application of nutritional knowledge for developing econutrition feeding programs on commercial swine farms

Intensive pork production operations are being confronted by increased societal pressure due to the potential impact of swine waste on water, air, and soil quality. This review focuses on practical solutions and future opportunities to use diet manipulation and feeding management technologies to reduce nutrient excretions and gaseous compounds emitted from manure. Nutrient mass balance will become more critical for pork production units to avoid water quality problems and excessive soil nutrient accumulation in soil. Diet manipulation techniques adaptable to commercial pork production include reduction of crude protein level by using synthetic amino acids; reduction of supplemental inorganic P and use of phytase; and use of organic forms of Cu, Zn, Fe, and Mn. Feeding management technologies that will enhance feed efficiency and reduce nutrient excretion include formulating diets to more precisely meet nutrient requirements (sex, genetic potential, phase feeding). Effectiveness of using nonstarch polysaccharides in swine diets to reduce pH and ammonia emissions needs to be evaluated on commercial swine farms. Research is needed to determine the efficacy and impact of genetically modified feed ingredients in commercial diets. Best-cost formulations will include economic value for manure nutrient levels and utilization costs. Diets may be modified to create nutrient-balanced manure for sustainable crop production. In some situations, nutrient management and pig performance can be compatible; however, in some situations optimal whole-system performance may not coincide with maximum productivity, daily weight gain, and feed efficiency. Future econutrition research needs to be conducted with a multidisciplinary approach with consideration of available land, animal health and behavior, quality of animal products, and nutrient balance in the whole-farm system.

A simulation model of organic matter and nutrient accumulation in mangrove wetland soils

The distribution and accumulation of organic matter, nitrogen (N) and phosphorus (P) in mangrove soils at four sites along the Shark River estuary of south Florida were investigated with empirical measures and a process-based model. The mangrove nutrient model (NUMAN) was developed from the SEMIDEC marsh organic matter model and parameterized with data from mangrove wetlands. The soil characteristics in the four mangrove sites varied greatly in both concentrations and profiles of soil carbon, N and P. Organic matter decreased from 82% in the upstream locations to 30% in the marine sites. Comparisons of simulated and observed results demonstrated that landscape gradients of soil characteristics along the estuary can be adequately modeled by accounting for plant production, litter decomposition and export, and allochthonous input of mineral sediments. Model sensitivity analyses suggest that root production has a more significant effect on soil composition than litter fall. Model simulations showed that the greatest change in organic matter, N, and P occurred from the soil surface to 5 cm depth. The rapid decomposition of labile organic matter was responsible for this decrease in organic matter. Simulated N mineralization rates decreased quickly with depth, which corresponded with the decrease of labile organic matter. The increase in organic matter content and decrease in soil bulk density from mangrove sites at downstream locations compared to those at upstream locations was controlled mainly by variation in allochthonous inputs of mineral matter at the mouth of the estuary, along with gradients in mangrove root production. Research on allochthonouns sediment input and in situ root production of mangroves is limited compared to their significance to understanding nutrient biogeochemistry of these wetlands. More accurate simulations of temporal patterns of nutrient characteristics with depth will depend on including the effects of disturbance such as hurricanes on sediment redistribution and biomass production.

Influence of stock camping behaviour on the soil microbiological and biochemical properties of grazed pastoral soils

The size and activity of the soil microbial biomass in grazed pastures was compared on the main grazing area and on stock camp areas where animals congregate. Two sites were on hill country and three on gently sloping border-dyke irrigated land. Due to the transfer of nutrients and organic matter to the camp areas via dung and urine there was an accumulation of soil organic C, organic and inorganic P and S and soluble salts in the camp areas. Soil pH also tended to be higher in camp areas due to transfer of alkalinity by the grazing animals. Water soluble organic C, microbial biomass C and basal respiration were all higher in soils from camp areas but the proportion of organic C present as microbial C and the microbial respiratory quotient were unaffected. Microbial activity as quantified by arginine ammonification rate and fluorescein diacetate (FDA) hydrolysis was higher in camp than non-camp soils but dehydrogenase activity remained unaffected. Activities of protease, histidase, urease, acid phosphatase and aryl-sulphatase were all higher in stock camp soils. The activities of both histidase and aryl-sulphatase were also higher when expressed per unit of microbial biomass C, indicating that the increased activity was the result of increased enzyme production by the microbial community. Prolonged regular applications of dairy shed effluent (diluted dung and urine from cattle) to a field had a similar effect to stock camping in increasing soil organic matter content, nutrient accumulation and soil biological activity. It was concluded that the stock camping activity of grazing animals results in an increase in both the fertility and biological activity in soils from camp areas at the expense of these properties on the main grazing areas.

Recent and Long‐Term Organic Soil Accretion and Nutrient Accumulation in the Everglades

AbstractOrganic soil accretion and nutrient accumulation were measured in the northern, central, and southern Everglades to evaluate the effects of anthropogenic nutrient and hydroperiod alterations on organic C and nutrient storage during the past century. Six soil cores (euic, hyperthermic Typic Medisaprists) were collected from nutrient‐enriched (Water Conservation Area [WCA] 2A) and unenriched locations. Soil depth increments were analyzed for radionuclides (137Cs, 210Pb, 14C), bulk density, and nutrients (C, N, P, S) to estimate recent (30‐yr) and long‐term (100‐yr) organic soil accretion and nutrient accumulation. Since WCA 2A was completely impounded in the early 1960s, organic soil accretion in northern WCA 2A (5.8–6.7 mm yr−1) increased by three to five times compared with before 1960 (1.9 mm yr−1) or with unenriched areas within and outside of WCA 2A (1.4–1.6 mm yr−1). Nutrient accumulation in the enriched area of WCA 2A since 1960 was two (184–223 g C m−2 yr−1, 13.6–16.6 g N m−2 yr−1) to eight (0.40–0.46 g P m−2 yr−1) times higher than before 1960 (110 g C m−2 yr−1, 6.6 g N m−2 yr−1, 0.06 g P m−2 yr−1) or in unenriched areas (65–90 g C m−2 yr−1, 4.7–6.4 g N m−2 yr−1, 0.06 g P m−2 yr−1). Unenriched areas of the Everglades possess some of the lowest rates of P accumulation of peatlands in North America. Successful restoration of the Everglades will have to include the elimination of anthropogenic nutrient loadings to limit the P enrichment zone from expanding into existing unenriched interior areas and areas downstream of WCA 2A.