Litter-amended Soils Research Articles

Phosphorus in runoff from two highly weathered soils of the tropics

Ramirez-Avila, J. R., Sotomayor-Ramirez, D., Martinez-Rodriguez, G. A. and Perez-Alegria, L. R. 2011. Phosphorus in runoff from two highly weathered soils of the tropics. Can. J. Soil Sci. 91: 267-277. Agricultural fields with high soil phosphorus (P) content are important contributors to surface water degradation. Two consecutive simulated rainfall events were conducted on two Ultisols previously amended with inorganic P fertilizer or broiler litter. Soil test P (Bray 1 and Olsen) levels evaluated ranged from 1 to 350 mg kg-1. Surface runoff concentrations of total P (TP) and dissolved P (DP) generated by a 30-min runoff event were quantified. Runoff DP concentrations ranged from 0.08 to 3.98 mg L-1 in fertilizer P-amended soils and from 0.08 to 4.93 mg L-1 in broiler litter-amended soils. A single exponential model adequately described the relationships between soil test P and DP concentrations in runoff. For each soil, the soil test P-DP concentration relationships were positively influenced by soil or...

Phosphorus in runoff from two highly weathered soils of the tropics

Ramírez-Ávila, J. R., Sotomayor-Ramírez, D., Martínez-Rodríguez, G. A. and Pérez-Alegría, L. R. 2011. Phosphorus in runoff from two highly weathered soils of the tropics. Can. J. Soil Sci. 91: 267–277. Agricultural fields with high soil phosphorus (P) content are important contributors to surface water degradation. Two consecutive simulated rainfall events were conducted on two Ultisols previously amended with inorganic P fertilizer or broiler litter. Soil test P (Bray 1 and Olsen) levels evaluated ranged from 1 to 350 mg kg−1. Surface runoff concentrations of total P (TP) and dissolved P (DP) generated by a 30-min runoff event were quantified. Runoff DP concentrations ranged from 0.08 to 3.98 mg L−1in fertilizer P-amended soils and from 0.08 to 4.93 mg L−1in broiler litter-amended soils. A single exponential model adequately described the relationships between soil test P and DP concentrations in runoff. For each soil, the soil test P-DP concentration relationships were positively influenced by soil organic matter and negatively influenced by antecedent soil moisture (P<0.05). For both soils, the soil test P-DP concentration relationships were positively influenced by groundcover percentage and negatively influenced by slope. Environmental soil test P critical levels corresponding to a runoff threshold of 1 mg L−1DP, ranged between 176 and 296 mg kg−1(Olsen) and 143 to 276 mg kg−1(Bray 1) in soils amended with fertilizer-P. In broiler litter-amended soils, threshold values were 88 and 111 mg kg−1using Olsen and Bray 1, respectively. Differences in surface runoff-P concentrations due to amendment sources, antecedent soil moisture content, soil organic matter, groundcover and slope suggest that these factors need to be considered in P management decisions at the farm level.

Free and Conjugated Estrogen Exports in Surface‐Runoff from Poultry Litter–Amended Soil

Land application of animal manures such as poultry litter is a common practice, especially in states with surplus manure. Past studies have shown that animal manure may contain estrogens, which are classified as endocrine-disrupting chemicals and may pose a threat to aquatic and wildlife species. We evaluated the concentrations of estrogens in surface runoff from experimental plots (5 x 12 m each) receiving raw and pelletized poultry litter. We evaluated the free (estrone, E1; 17beta-estradiol, E2beta; estriol, E3) and conjugate forms (glucuronides and sulfates) of estrogens, which differ in their toxicity. Sampling was performed for 10 natural storm events over a 4-mo period (April-July 2008). Estrogen concentrations were screened using enzyme-linked immunosorbent assay (ELISA), followed by quantification using liquid chromatography with tandem mass spectrometry (LC/MS/MS). Concentrations of estrogens from ELISA were much higher than the LC/MS/MS values, indicating crossreactivity with organic compounds. Exports of estrogens were much lower from soils amended with pelletized poultry litter than the raw form of the litter. No-tillage management practice also resulted in a lower export of estrogens with surface runoff compared with reduced tillage. The concentrations and exports of conjugate forms of estrogens were much higher than the free forms for some treatments, indicating that the conjugate forms should be considered for a comprehensive assessment of the threat posed by estrogens.

Evaluación de mejores prácticas de manejo para reducir las pérdidas de nutrientes contaminantes en escorrentía desde suelos enmendados con carnada de pollos parrilleros. I. Adiciones de alum.

El efecto de alum [AI2(S04)3-14H20] en la reducción de las concentraciones de fósforo (P) en las aguas de escorrentía desde los suelos enmendados con residuos de carnadas de pollos parrilleros se evaluó en varios eventos de lluvia simulada. Adiciones de alum a razón de 20% (peso/peso) causaron una reducción significativa en la fracción de P "soluble" (CaCI2-extraíble) presente en la matriz de la carnada de pollos parrilleros. Como resultado, el P soluble añadido al suelo se redujo en un 43% y un 75% para los tratamientos de 6 t/ha y 20 t/ha de residuos de carnada de pollos parrilleros con alum en comparación con sus contrapartes sin alum. Las concentraciones de P total en la escorrentía de los tratamientos 6 t/ha y 20 t/ha de residuos de carnada de pollos parrilleros sin alum resultaron altamente enriquecidas, promediando 2.59 y 6.10 mg/L, respectivamente. En la dosis más alta de residuos de carnada de pollos parrilleros (20 t/ha), el tratamiento de 20% de alum logró una reducción de 52% en la concentración de P total en la escorrentía relativo al tratamiento sin alum. Sin embargo, el efecto más notable de alum fue en la reducción de las pérdidas de P disuelto. Las pérdidas en las concentraciones de P disuelto promedio en el tratamiento de 20 t/ha de residuos de carnada de pollos parrilleros (sin alum) fue de 3.55 mg/L, un valor significativamente mayor que el umbral de 1.0 mg/L que ha sido sugerido como el límite potencial para el control de pérdidas de P por escorrentía de predios agrícolas. En dicha dosis de aplicación los tratamientos de 10% y 20% de alum alcanzaron reducciones de 58% y 70% en las concentraciones de P disuelto en la escorrentía, espectivamente. Las pérdidas en las concentraciones de P disuelto observadas para los tratamientos con 20% de alum cumplieron con el valor umbral de 1.0 mg/L en prácticamente todos los casos, irrespectivamente de la dosis de residuos de carnada de pollos parrilleros evaluada. Las pérdidas de P total en la escorrentía fue correlacionada positivamente tanto con la fracción de P soluble (extraíble con CaCI2) aplicado a los suelos, como con los niveles de P (Olsen) en el suelo durante las diferentes etapas de los eventos de simulación de lluvia. El contenido nutricional (N, P, y K) para muestras de hierba Bermuda reflejó el efecto de las diferentes dosis de residuos de carnada de pollos parrilleros. Se observó un mayor contenido nutricional en los tratamientos de 20 t/ha comparado con los de 6 t/ha. No obstante, los efectos solo fueron estadísticamente significativos para nitrógeno. El alum no parece ejercer un impacto significativo en el contenido nutricional de la yerba Bermuda, aunque se observaron disminuciones leves (no significativas) para N y P en el tratamiento de 20 t/ha de carnada de pollos parrilleros con 20% de alum.

Evaluación de mejores prácticas de manejo para reducir las pérdidas de nutrientes contaminantes en escorrentía desde suelos enmendados con carnada de pollos parrilleros. II. Cobertura de hierbas.

Se evaluó el impacto de la extensión de la cobertura del pasto Bermuda [Cynodon dactylon (L.)] en la pérdida de sedimentos y nutrientes en escorrentía en suelos enmendados con residuos de carnada de pollos parrilleros (con alum). La escorrentía generada de los suelos completamente descubiertos reflejó valores significativamente mayores en los volúmenes de escorrentía y en las concentraciones de sólidos suspendidos, fósforo total (TP) y nitrógeno total Kjeldahl (TKN), que en suelos con ≥80% de cobertura de pasto. Además, el suelo descubierto exhibió un tiempo de inicio de escorrentía menor (lapso de tiempo entre inicio de la lluvia y el comienzo de la escorrentía) que los suelos con pasto. Las concentraciones promedio de P total y TKN en la escorrentía de bandejas experimentales con a80% de cobertura de hierba exhibieron una reducción de 93% y 89.5%, respectivamente, comparado con aquellas en la escorrentía de las bandejas con suelo al descubierto. Por otra parte, la concentración de sólidos suspendidos mostró una reducción de 99% sobre la del suelo al descubierto. Las pérdidas en fósforo disuelto estuvieron bien por debajo del límite de 1 mg/L sugerido como el nivel para el control de contaminación de fósforo de tierras agrícolas, incluyendo suelos enmendados con residuos de carnada de pollos parrilleros. En el caso de estos residuos, el resultado es un reflejo de la efectividad del alum en la reducción de la pérdida de fósforo disuelto en la escorrentía. En general, tanto las concentraciones de P total como TKN siguieron las tendencias establecidas por las pérdidas de sedimentos. Una disminución significativa en la concentración de sedimentos suspendidos fue observada con el tiempo en ambos tipos de coberturas del suelo, con pérdidas significativamente más altas en suelos al descubierto que en suelos con cobertura vegetal. En contraste, el nitrato exhibió una correlación negativa con las concentraciones de sólidos suspendidos. Aplicaciones de residuos de carnada de pollos parrilleros causaron un aumento significativo en las concentraciones de los constituyentes disueltos (i.e., P disuelto y N03-N) en la escorrentía, pero no así de otros constituyentes (i.e., P total y TKN) para los cuales las pérdidas de sedimentos representan un mecanismo significativo de transporte. La aplicación de residuos de carnada de pollos parrilleros redujo significativamente la pérdida en la concentración de sólidos suspendidos para cada categoría de cubierta vegetal, aunque una pérdida mucho mayor fue observada para el suelos al descubierto. La combinación de aplicación de alum y una buena cobertura de hierba (≥80%) reduce los estimados de carga de exporte de sedimentos suspendidos, P total y TKN en la escorrentía por más de un 95% comparado con los de los suelos al descubierto.

Phosphorus Dynamics in Two Poultry-Litter Amended Soils of Mississippi Under Three Management Systems

An experiment arranged in a randomized complete block design with three replications was conducted on a Lexington soil (fine-silty, mixed, active, thermic, Ultic Hapludalfs) and a Loring soil (fine-silty, mixed, active, thermic, Oxyaquic Fragiudalfs) in Mississippi from September 1997 to September 2000 on 18 runoff plots under natural rainfall condition to study the phosphorus (P) dynamics in poultry litter amended soils under three management systems combining tillage and planting date treatments to identify effective management practices in southern U.S.A. The management systems in the study were: 1) tillage in the fall prior to litter application followed by a delayed planting of fall forages (CT-DP); 2) tillage followed by immediate planting of the fall forage with subsequent litter application (CT-IP); and 3) no-till with planting prior to litter application (NT-IP). The results indicated that there was significant increase in soil P after 3 years of poultry litter application for both Lexington and Loring soils ( P< 0.05). Based on P budget analysis, the majority of P from poultry litter application (> 90%), was accumulated in both soils. In Loring soil, soluble P mass in the runoff was significantly higher from NT-IP than from CT-DP and CT-IP over the entire study period ( P< 0.01). For both soils, there were no significant differences in sediment P mass between management systems. For Loring soil, CT-DP and CT-IP were effective management practices to mitigate negative effects due to poultry litter application.

Modifying Broiler Diets with Phytase and Vitamin D Metabolite (25‐OH D3): Impact on Phosphorus in Litter, Amended Soils, and Runoff

Adding phytase and 25- hydroxycholecalciferol (25-OH D(3)) to broiler diets has been shown effective at reducing total P concentrations in broiler litter. This study was conducted to determine the impact of field application of broiler litter from modified diets on P solubility in litter-amended soils and P losses in runoff. Five broiler diets and their resulting litters were evaluated: a high P diet, a low P diet, each of those basal diets with phytase added, and a low P diet with phytase and 25-OH D(3) added. A field study was initiated at two sites with each of the five broiler litters and a commercial P fertilizer (triple superphosphate [TSP]) applied at the same total P rate (150 kg P ha(-1)) and a control where no P was applied. Soil P was monitored over time at two depths (0-5 cm and 0-15 cm) soils were collected in the spring and fall to perform rainfall simulation studies. Broiler litter or TSP application increased soil water-soluble P and Mehlich 3-P concentrations relative to the control, however there were no consistent differences detected between litter treatments. Results from the rainfall simulation experiments indicate that diet modification with phytase or 25-OH D(3) does not increase the potential for P losses in runoff from amended soils relative to traditional diets. Moreover, broiler diet modification to reduce excreted P could be a potentially effective method for reducing watershed scale P surpluses in areas of intensive broiler production, without raising concerns over soluble P losses from litter-amended soils.

Carbon decomposition in broiler litter-amended soils

Organic carbon (OC) is generally low in Alabama (U.S.A.) soils and varies considerably with cropping systems. Information on decomposition rates of the added C is a prerequisite to designing strategies that improve C sequestration in farming systems. Different models including exponential models have been used to describe OC mineralization in soils as well as to describe its potential as CO 2 to be released into the environment. We investigated the decomposition of broiler litter added to ten non-calcareous soils (Appling, Troup, Cecil, Decatur, Sucarnoochee, Linker, Hartsells, Dothan, Maytag, and Colbert soils). A non-linear regression approach for N mineralization was used to estimate the potentially mineralizable OC pools (C o) and the first-order rate constant (k) in the soil samples. Results showed that the non-amended soils have distinct differences in their ability to release their native OC as CO 2 and can be divided into four groups depending on their potentially mineralizable C (C o) and their ability to protect stable organic matter. Sucarnoochee soil represents the first group and contains a moderate amount of OC (11.4 g C kg −1) but had the highest C o (7.30 g C kg −1 soil). The second distinct group of soils has C o varying between 5.50 and 5.00 g C kg −1 soil (Decatur, Hartsells, Dothan, and Maytag). The third group has C o between 5.00 and 4.00 (Appling, Cecil, and Linker). The fourth group has C o less than 4.00 g C kg −1 soil (Troup and Colbert). Half-life of C remaining in non-amended soils varied from 26 days in Maytag soil to 139 days in Cecil soil. The OC in these non-amended soils represents a very stable form of organic C and thus, not easily decomposed by soil microorganisms. In the broiler litter-amended soils, the C o varied from 3.82 g C kg −1 in Appling soil amended with broiler litter 1–7.04 g C kg −1 soil in Maytag amended with broiler litter 2. Decomposition of the added OC proceeded in two phases with less than 31% decomposed in 43 days. Potentially mineralizable organic C (C o) was related to soil organic C ( r = 0.661**) and soil C/N ratio ( r = 0.819*).

Growth of Frankia strains in leaf litter-amended soil and the rhizosphere of a nonactinorhizal plant

The ability of Frankia strains to grow in the rhizosphere of a nonactinorhizal plant, Betula pendula, in surrounding bulk soil and in soil amended with leaf litter was analyzed 6 weeks after inoculation of pure cultures by in situ hybridization. Growth responses were related to taxonomic position as determined by comparative sequence analysis of nifH gene fragments and of an actinomycetes-specific insertion in Domain III of the 23S rRNA gene. Phylogenetic analyses confirmed the basic classification of Frankia strains by host infection groups, and allowed a further differentiation of Frankia clusters within the Alnus host infection group. Except for Casuarina-infective Frankia strains, all other strains of the Alnus and the Elaeagnus host infection groups displayed growth in the rhizosphere of B. pendula, and none of them grew in the surrounding bulk soil that was characterized by a very low organic matter content. Only a small number of strains that all belonged to a distinct phylogenetic cluster within the Alnus host infection group grew in soil amended with ground leaf litter from B. pendula. These results demonstrate that saprotrophic growth of frankiae is a common trait for most members of the genus, and the supporting factors for growth (i.e. carbon utilization capabilities) varied with the host infection group and the phylogenetic affiliation of the strains.

Rewetting and litter addition influence mineralisation and microbial communities in soils from a semi-arid intermittent stream

Nitrogen (N) and carbon (C) mineralisation are triggered by pulses of water availability in arid and semi-arid systems. Intermittent streams and their associated riparian communities are obvious ‘hot spots’ for biogeochemical processes in arid landscapes where water and often C are limiting. Stream landscapes are characterized by highly heterogeneous soils that may respond variably to rewetting. We used a laboratory incubation to quantify how N and C mineralisation in rewetted soils and sediments from an intermittent stream in the semi-arid Pilbara region of north-west Australia varied with saturation level and substrate addition (as ground Eucalyptus litter). Full (100%) saturation was defined as the maximum gravimetric moisture content (%) achieved in free-draining soils and sediments after rewetting, with 50% saturation defined as half this value. We estimated rates and amounts of N mineralised from changes in inorganic N and microbial respiration as CO 2 efflux throughout the incubation. In soils and sediments subject to 50% saturation, >90% of N mineralised accumulated within the first 7 d of incubation, compared to only 48% when soils were fully saturated (100% saturation). Mineralisation rates and microbial respiration were similar in riparian and floodplain soils, and channel sediments. N mineralisation rates in litter-amended soils and sediments (0.73 mg N kg −1 d −1) were only one-third that of unamended samples (3.04 mg N kg −1 d −1), while cumulative microbial respiration was doubled in litter-amended soils, suggesting N was more rapidly immobilized. Landscape position was less important in controlling microbial activity than soil saturation when water-filled pore space (% WFPS) was greater than 40%. Our results suggest that large pulses of water availability resulting in full soil saturation cause a slower release of mineralisation products, compared to small pulse events that stimulate a rapid cycle of C and N mineralisation–immobilization.

Tillage and Forage System Effects on Forage Yields and Nutrient Uptake under Broiler Litter–Amended Soils

Planting and harvesting high‐yielding forage grasses may remove phosphorus (P), copper (Cu), and zinc (Zn) from surface soils with a long history of broiler litter application. A study was conducted in Alabama's Sand Mountain region from 1998 to 2000 to determine tillage and forage systems best suited for removing nutrients from such overloaded soils. Tillage treatments included no‐till, moldboard plowing, chisel plowing, and each combined with paraplowing. Forage treatments included bermudagrass (Cynodon dactylon (L.) Pers.) cv. Russell, tall fescue (Festuca arundinacea Schreb.) cv. Kentucky‐31, and an annual rotation of ryegrass (Lolium multiflorum Lam.) and sorghum sudangrass (Sorghum bicolor L. Moench×Sorghum vulgare sudanense). The annual rotation produced highest yields and P uptake. Moldboard plowing the annual rotation further increased yields. It appears the annual rotation best removes P, Cu, and Zn via plant uptake. Tillage reduced P concentrations in the soil surface in the following order: moldboard>chisel>no‐till.

NITROGEN DYNAMICS IN AN AUSTRALIAN SEMIARID GRASSLAND SOIL

We conducted a four-week laboratory incubation of soil from a Themeda triandra Forsskal grassland to clarify mechanisms of nitrogen (N) cycling processes in relation to carbon (C) and N availability in a hot, semiarid environment. Variation in soil C and N availability was achieved by collecting soil from either under tussocks or the bare soil between tussocks, and by amending soil with Themeda litter. We measured N cycling by monitoring: dissolved organic nitrogen (DON), ammonium (NH4+), and nitrate (NO3-) contents, gross rates of N mineralization and microbial re-mineralization, NH4+ and NO3- immobilization, and autotrophic and heterotrophic nitrification. We monitored C availability by measuring cumulative soil respiration and dissolved organic C (DOC). Litter-amended soil had cumulative respiration that was eightfold greater than non-amended soil (2000 compared with 250 microg C/g soil) and almost twice the DOC content (54 compared with 28 microg C/g soil). However, litter-amended soils had only half as much DON accumulation as non-amended soils (9 compared with 17 microg N/g soil) and lower gross N rates (1-4 compared with 13-26 microg N x [g soil](-1) x d(-1)) and NO3- accumulation (0.5 compared with 22 microg N/g soil). Unamended soil from under tussocks had almost twice the soil respiration as soil from between tussocks (300 compared with 175 microg C/g soil), and greater DOC content (33 compared with 24 microg C/g soil). However, unamended soil from under tussocks had lower gross N rates (3-20 compared with 17-31 microg N x [g soil](-1) d(-1)) and NO3- accumulation (18 compared with 25 microg N/g soil) relative to soil from between tussocks. We conclude that N cycling in this grassland is mediated by both C and N limitations that arise from the patchiness of tussocks and seasonal variability in Themeda litterfall. Heterotrophic nitrification rate explained >50% of total nitrification, but this percentage was not affected by proximity to tussocks or litter amendment. A conceptual model that considers DON as central to N cycling processes provided a useful initial framework to explain results of our study. However, to fully explain N cycling in this semiarid grassland soil, the production of NO3- from organic N sources must be included in this model.

Soil compaction and poultry litter effects on factors affecting nitrogen availability in a claypan soil

Soil compaction may affect N mineralization and the subsequent fate of N in agroecosystems. Laboratory incubation and field experiments were conducted to determine the effects of surface soil compaction on soil N mineralization in a claypan soil amended with poultry litter (i.e., Turkey excrement mixed with pine shavings as bedding). In a laboratory study, soil from the surface horizon of a Mexico silt loam soil was compacted to four bulk density levels (1.2, 1.4, 1.6 and 1.8 Mg m −3) with and without poultry litter and incubated at 25 °C for 42 days. A field trial planted to corn ( Zea mays L.) was also conducted in 2002 on a Mexico silt loam claypan soil in North Central Missouri. Soil was amended with litter (0 and 19 Mg ha −1) and left uncompacted or uniformly compacted. Soil compaction decreased soil inorganic N by a maximum of 1.8 times in the laboratory study; this effect was also observed at all depths of the field trial. Compacted soil with a litter amendment accumulated NH 4 +-N up to 7.2 times higher than the noncompacted, litter-amended soil until Day 28 of the laboratory incubation and in the beginning of the growing season of the field study. Ammonium accumulation may have been due to decreased soil aeration under compacted conditions. Application of litter increased soil N mineralization throughout the growing season. In the laboratory study, soil inorganic N in unamended soil was negatively correlated with soil bulk density and the proportion of soil micropores, but was positively related with soil total porosity and the proportion of soil macropores. These results indicate that soil compaction, litter application and climate are interrelated in their influences on soil N mineralization in agroecosystems.

Broiler Diet Modification and Litter Storage

Modifying broiler diets to mitigate water quality concerns linked to excess phosphorus (P) in regions of intensive broiler production has recently increased. Our goals were to evaluate the effects of dietary modification, using phytase and reduced non-phytate phosphorus (NPP) supplementation, on P speciation in broiler litters, changes in litter P forms during long-term storage, and subsequent impacts of diets on P in runoff from litter-amended soils. Four diets containing two levels of NPP with and without phytase were fed to broilers in a three-flock floor pen study. After removal of the third flock, litters were stored for 440 d at their initial moisture content (MC; 24%) and at a MC of 40%. Litter P fractions and orthophosphate and phytate P concentrations were determined before and after storage. After storage, litters were incorporated with a sandy and silt loam and simulated rainfall was applied. Phytase and reduced dietary NPP significantly reduced litter total P. Reducing dietary NPP decreased water-extractable inorganic phosphorus (IP) and the addition of dietary phytase reduced NaOH- and HCl-extractable organic P in litter, which correlated well with orthophosphate and phytic acid measured by 31P nuclear magnetic resonance (NMR), respectively. Although dry storage caused little change in P speciation, wet storage increased concentrations of water-soluble IP, which increased reactive P in runoff from litter-amended soils. Therefore, diet modification with phytase and reduced NPP could be effective in reducing P additions on a watershed scale. Moreover, efforts to minimize litter MC during storage may reduce the potential for dissolved P losses in runoff.

The effect of mixing ground leaf litters to soil on the development of pitch pine ectomycorrhizal and soil arthropod communities in natural soil microcosm systems

The addition of leaf litter to soil influences both the nutrients and polyphenols of soil. It is likely that contrasting nutrient and polyphenolic composition of different plant litters may affect plant growth, mycorrhizal and soil arthropod communities. We report results from a microcosm experiment of effects of incorporation of three single leaf litter species and a mixture of all three on pitch pine seedling growth, their ectomycorrhizal community and soil arthropod community. The three litter species (pine, oak and huckleberry) represent co-dominant species within the New Jersey pine barrens ecosystem. We show that the leaf litters have different composition of nutrients and polyphenols, with rooting matrix containing pine litter having lower inorganic nitrogen content (1.6 μg g −1) than oak (19.9 μg g −1) and huckleberry (4.4 μg g −1), but oak litter having the highest extractable phosphorus (13.3 cf. 0–0.08 μg g −1) and total phenol content and lowest condensed tannin content. These differences were imparted to rooting matrix of homogenized humic (Oa) layer of pine barrens soil to which milled leaf litter was added and used in the microcosms. Pitch pine seedlings grew significantly better in un-amended rooting matrix (0.33±0.02 g) than any of the litter treatments (0.15±0.02–0.17±0.01 g) and tissue P concentrations tracked phosphate concentrations in the rooting matrix. Total P accumulation into plant tissue was higher in oak than control, attributable to a significantly higher ( P<0.05) accumulation in roots (3.3±0.19 mg g −1) compared to other species (1.1±0.04–2.3±0.08 mg g −1). No relationship was seen between tissue N concentration and soil N, but seedlings growing in huckleberry litter amended soil accumulated less N than control. The effect of leaf litters on the ectomycorrhizal community composition were determined by PCA (first two axes accounted for 81% of the variance) and stepwise multiple regression analysis. These analyses showed that huckleberry leaf litter had a significant impact on mycorrhizal community composition with morphotypes Cg and DB being more abundant in the presence of huckleberry litter (178±13 cf. 68±15–106±15 for Cg and 141±11 cf. 88±23–111±18 for DB) and its influence of elevating nitrate nitrogen, organic nitrogen, total phenols and protein precipitation content of the rooting matrix. Mycorrhizal morphotypes BS and SB were significantly more abundant in the community where these soil factors were low in the absence of leaf litter addition. Total ectomycorrhizal abundance was negatively related to hydrolysable tannin concentration in the rooting matrix ( r 2=0.132, P<0.05). There was no influence of leaf litter type on mite density (dominated by non-burrowing phthiracarids), but collembolan density (dominated by Folsomia spp) showed a greater than threefold reduction in population density in the presence of leaf litter ( F=6.47, P<0.05). Collembolan density was positively correlated with mycorrhizal morphotypes GS and SB ( P<0.05) and negatively related to morphotypes DB ( P<0.05) and soil extractable NH 4–N ( P<0.05), suggesting a possible selection of fungal species in their diet and a relationship between collembola and nitrification.

Phytase Supplementation and Reduced‐Phosphorus Turkey Diets Reduce Phosphorus Loss in Runoff following Litter Application

Concerns about regional surpluses of manure phosphorus (P) leading to increased P losses in runoff have led to interest in diet modification to reduce P concentrations in diets. The objectives of this study were to investigate how dietary P amendment affected P concentrations in litters and P losses in runoff following land application. We grew two flocks of turkeys on the same bed of litter using diets with two levels of non-phytate phosphorus (NPP), with and without phytase. The litters were incorporated into three soils in runoff boxes at a plant-available nitrogen (PAN) rate of 168 kg PAN/ha, with runoff generated on Days 1 and 7 under simulated rainfall and analyzed for dissolved reactive phosphorus (DRP) and total P. Litters were analyzed for water-soluble phosphorus (WSP) and total P, while soils in the runoff boxes were analyzed for WSP and Mehlich-3 phosphorus (M3-P). Formulating diets with lower NPP and phytase both decreased litter total P. Phytase had no significant effect on litter WSP at a 1:200 litter to water extraction ratio, but decreased WSP at a 1:10 extraction ratio. Using a combination of reducing NPP fed and phytase decreased the total P application rate by up to 38% and the P in surplus of crop removal by approximately 48%. Reducing the NPP fed reduced DRP in runoff from litter-amended soils at Day 1, while phytase had no effect on DRP concentrations. Increase in soil M3-P was dependent on total P applied, irrespective of diet. Reducing overfeeding of NPP and utilizing phytase in diets for turkeys should decrease the buildup of P in soils in areas of intensive poultry production, without increasing short-term concerns about dissolved P losses.

Mineral Content of Forages Grown on Poultry Litter-Amended Soils

Large quantities of poultry litter are applied each year to pastures in Arkansas and Oklahoma. Our objective was to monitor mineral concentrations in forages grown on poultry litter-amended soils and compare them with mineral requirements for gestating and early lactating beef cows. A total of 65 forage samples were gathered from four farms in northwest Arkansas and northeast Oklahoma from April 2000 to March 2002. Mean forage mineral concentrations were compared with beef cattle requirements using a two-tailed t test. Two-year average forage Ca, P, K, S, and Fe concentrations from each farm exceeded (P<0.05) gestation and lactation requirements, but forage Zn concentrations from one farm did not differ (P>0.05) from gestation and lactation requirements. On individual sampling dates, concentrations of Ca, P, K, and Zn rarely fell below lactation requirements. Mean forage Mg concentrations from one farm exceeded (P<0.05) lactation requirements, but those from the other three farms exceeded (P<0.05) gestation but not (P>0.05) lactation requirements. Mean tetany ratios from all farms were below (P<0.05) the tetany threshold of 2.2, but forage from two farms surpassed the tetany threshold during Spring 2000, and one sur-passed it during Spring 2001. Average forage Cu concentrations were below (P<0.05) requirements on one farm and did not differ (P>0.05) from the requirements on three farms. Forages from pastures fertilized with broiler litter may meet most but not all mineral requirements of beef cattle, and supplementation of specific minerals, particularly Mg and Cu, may be necessary.

Carbon Mineralization Potential in Soils of Different Habitats in the Semiarid Horqin Sandy Land: A Laboratory Experiment

Soil organic carbon mineralization potential in four different sandy habitats (shifting, semi-fixed, fixed sand dune, and interdunal lowland) and the effects of litter addition from shrubs and annual plants on soil microbial respiration were measured using a laboratory soil incubation experiment. Soil samples were collected from beneath and outside the canopies of shrubs in all habitats. Soils were incubated for 33 days with and without litter addition. It was concluded that the differences in C mineralization of soils among habitats correlated with the vegetation cover, litter accumulation, and soil structure, organic C, and N contents. Very poor organic C and N as well as very weak microbial respiration were found in soils of the shifting sand dune, suggesting that sandy desertification strongly depleted both bulk of soil organic C and soil labile C pool. Caragana microphylla litter amended soils and annual plant litter amended soils had the greatest and the lowest microbial respiration, respectively, which might in part be attributed to the N contents and C/N ratios in litters. Shrubs accumulated more organic material and created fertile islands with larger organic C and nutrients and microbial activity under their canopies, and therefore, significantly contributed to C sequestration.

Microbial activities during the early stage of laboratory decomposition of tropical leaf litters: the effect of interactions between litter quality and exogenous inorganic nitrogen

The comparative decomposition of tropical leaf litters (e.g. Andropogon gayanus, Casuarina equisetifolia, Faidherbia albida) of different qualities was investigated under laboratory conditions during a 60-day incubation period conducted with a typical oxisol. Total CO2-C, soil inorganic N, microbial biomass (fumigation-extraction), β-glucosidase and dehydrogenase activities were determined over the incubation to assess how they responded to the addition of inorganic N (+N). Cumulative CO2-C evolved from the litter-amended soils was higher than that recorded for the unamended control soil. For the unfertilized treatment (0 N), correlation coefficients calculated between initial chemical data and CO2 flux during the first day of incubation were r =0.963 for water soluble-C and 0.869 for soluble carbohydrates (P <0.05). At the end of the incubation, the amounts of CO2-C in the F. albida- and A. gayanus-amended soils were higher than that in the C. equisetifolia-amended treatment. Cumulative net N immobilization increased during the first 30 days of incubation, the amounts being similar for A. gayanus- and C. equisetifolia-amended soil and higher than that recorded in the F. albida-amended treatment. Soil microbial biomass and enzyme activities increased in the litter-amended soils during the first 15 days of incubation and decreased (except for the dehydrogenase activity) thereafter. The addition of inorganic N modified the patterns of CO2-C respiration and net N immobilization. The magnitude of these modifications varied according to the litter quality. The use of an accurate indicator based on several litter components to predict the amplitude of organic material decomposition is discussed.

Environmental fate of roxarsone in poultry litter. Part II. Mobility of arsenic in soils amended with poultry litter.

Poultry litter often contains arsenic as a result of organo-arsenical feed additives. When the poultry litter is applied to agricultural fields, the arsenic is released to the environment and may result in increased arsenic in surface and groundwater and increased uptake by plants. The release of arsenic from poultry litter, litter-amended soils, and soils without litter amendment was examined by extraction with water and strong acids (HCI and HNO3). The extracts were analyzed for As, C, P, Cu, Zn, and Fe. Copper, zinc, and iron are also poultry feed additives. Soils with a known history of litter application and controlled application rate of arsenic-containing poultry litter were obtained from the University of Maryland Agricultural Experiment Station. Soils from fields with long-term application of poultry litter were obtained from a tilled field on the Delmarva Peninsula (MD) and an untilled Oklahoma pasture. Samples from an adjacent forest or nearby pasture that had no history of litter application were used as controls. Depth profiles were sampled for the Oklahoma pasture soils. Analysis of the poultry litter showed that 75% of the arsenic was readily soluble in water. Extraction of soils shows that weakly bound arsenic mobilized by water correlates positively with C, P, Cu, and Zn in amended fields and appears to come primarily from the litter. Strongly bound arsenic correlates positively with Fe in amended fields and suggests sorption or coprecipitation of As and Fe in the soil column.