Typic Hapludult Research Articles

Aspects of Gametophyte Development of Dicksonia sellowiana Hook (Dicksoniaceae): an Endangered Tree Fern Indigenous to South and Central America

Abstract With the purpose of providing a basis for programs of sustainable management in the conservation of this endangered species, this paper presents morphological aspects on the gametophyte development of Dicksonia sellowiana (Dicksoniaceae) by light microscopy and scanning electron microscopy. Dicksonia sellowiana spores were germinated in Morh's nutrient solution modified by Dyer (1979) under a 16-hour photoperiod at 23 ± 2°C. To determine the best substrate for gametophyte and sporophyte development, 30 days after spore sowing filamentous gametophytes were transferred to different substrates: soil rich in organic matter; coxim (coconut fiber); sterilized typic hapludult soil (distroferric red nitosoil); and sterilized typic hapludult soil (distroferric red nitosoil) with the addition of organic compost. The best system for D. sellowiana growth was the red soil with the addition of compost. Fifteen days after spore sowing in mineral solution, gametophytes were filamentous. Some had attained laminar...

Enzymatic antioxidant responses to biostimulants in maize and soybean subjected to drought

Water stress is one of the most important environmental factors inducing physiological changes in plants, such as decrease in the water potential of the cells, the stomatal closure; and the development of oxidative processes mediated by reactive oxygen species (ROS). Antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) are efficient scavengers of ROS. The aim of this research was to examine how the application of biostimulant based on humic substances and aminoacids may affect activity levels of SOD, CAT, and APX of maize and soybean plants under well-watered or drought stress conditions. Pots (4.5 L) were filled with a Typic Hapludult soil where the biostimulants doses were applied. It was taken leaf samples in order to analyze SOD, CAT, and APX activities in plants. SOD and APX activity levels were increased by application of biostimulant 1 in maize subjected to stress. Catalase activity was not enhanced in plants by using the biostimulants. The composition of the biostimulants was not able to enhance stress tolerance in maize and soybean plants subjected to water stress.

Influence of Poultry Litter Application Methods on the Longevity of Nutrient and E. coli in Runoff from Tall Fescue Pasture

Significant quantities of the broiler chicken (Gallus gallus domesticus) litter produced in the USA are being applied to pasture lands. The traditional surface- broadcast application of animal manure onto permanent pasture, however, may lead to high concentration of nutrients and pathogenic microorganisms near the soil surface that could be transported off site by runoff water. Subsurface banding of poultry litter has the potential to reduce nutrient and pathogen losses through runoff. However, this has not been thoroughly investigated. In this study, we used rainfall simulations to examine the effect of broiler litter application methods on the longevity of nutrient and Escherichia coli losses in runoff by successive runoff events. Runoff plots were constructed on Hartsells fine sandy loam (Typic Hapludults) soil with permanent Kentucky 31 tall fescue (Festuca arundinacea) pasture in Crossville, AL. Treatments included two methods of litter application (surface broadcast and subsurface banding), commercial fertilizer, and control (no litter or fertilizer applied). To evaluate the longevity of nutrient losses, simulated rainfall (110 mm h−1) was applied to each plot on days 1, 7, and 14 following litter and fertilizer applications. Total P (TP), inorganic N, and E. coli concentrations were all significantly greater in runoff from broadcast litter application than the subsurface litter banding treatments. The TP losses from broadcast litter applications averaged 6.5 times those from subsurface litter applications. About 81% of the runoff TP concentration was in the form of dissolved reactive phosphorus for both litter application methods. The average losses of NO3–N and total suspended solids from subsurface litter banding plots were 358 g ha−1 and 68 kg ha−1 compared to 462 and 60 kg ha−1 for the broadcast method, respectively. This study shows that subsurface banding of broiler litter into perennial grassland can substantially reduce nutrient and pathogen losses in runoff compared to the traditional surface-broadcast practice.

Broiler Litter Application Method and Runoff Timing Effects on Nutrient and Escherichia coli Losses from Tall Fescue Pasture

The inability to incorporate manure into permanent pasture leads to the concentration of nutrients near the soil surface with the potential to be transported off site by runoff water. In this study, we used rainfall simulations to examine the effect of broiler chicken (Gallus gallus domesticus) litter application method and the runoff timing on nutrient and E. coli losses from tall fescue (Festuca arundinacea Schreb.) pasture on a Hartsells sandy loam soil (fine-loamy, siliceous, subactive, thermic Typic Hapludults)) in Crossville, AL. Treatments included two methods of litter application (surface broadcast and subsurface banding), commercial fertilizer, and control. Litter was applied at a rate of 8.97 Mg ha(-1). Treatments were assigned to 48 plots with four blocks (12 plots each) arranged in a randomized complete block design to include three replications in each block. Simulated rainfall was applied to treatments as follows: Day 1, block 1 (runoff 1); Day 8, block 2 (runoff 2); Day 15, block 3 (runoff 3); and Day 22, block 4 (runoff 4). Total phosphorus (TP), inorganic N, and Escherichia coli concentrations in runoff from broadcast litter application were all significantly greater than from subsurface litter banding. The TP losses from broadcast litter applications averaged 6.8 times greater than those from subsurface litter applications. About 81% of the runoff TP was in the form of dissolved reactive phosphorus (DRP) for both litter-application methods. The average losses of NO(3)-N and total suspended solids (TSS) from subsurface banding plots were 160 g ha(-1) and 22 kg ha(-1) compared to 445 g ha(-1) and 69 kg ha(-1) for the broadcast method, respectively. Increasing the time between litter application and the first runoff event helped decrease nutrient and E. coli losses from surface broadcast litter, but those losses generally remained significantly greater than controls and subsurface banded, regardless of runoff timing. This study shows that subsurface litter banding into perennial grassland can substantially reduce nutrient and pathogen losses in runoff compared to the traditional surface-broadcast practice.

Soil Characteristics and Genesis Processes of a Subtropical Low-Elevation Mountain Forest in Central Taiwan

Two representative soil pedons under natural broadleaf stands in the Lienhuachih Experiment Forest in central Taiwan were selected to investigate their soil characteristics and evaluate soil genesis processes. The studied soils were acidic (pH 3.80~4.92) with low organic carbon contents (＜4%) and extremely low base saturation (＜5%), which correspond to forest soils in tropical and subtropical regions. Brunification and laterization were found in forest soils where well crystalline iron and aluminum contents are relatively high (＞50%). There was an illuviation phenomenon of clay and free Fe and Al oxides (Fe(subscript d) and Al(subscript d)) in the studied soils, whereas amorphous Fe and Al oxides (Fe(subscript o) and Al(subscript o)) and organic Fe and Al complexes (Fe(subscript p) and Al(subscript p)) were predominant forms in the surface soils of this forest due to effects of the soil organic matter. Well-developed soils were found at the footslope site owing to higher contents of well crystalline Fe and Al oxides compared to those at the backslope site. Soils at the footslope site with bisequences were classified as Typic Hapludults, and those at the backslope site were classified as Typic Dystrudepts. We concluded that the soils have undergone strong weathering under paleoclimatic conditions. These soils had been disturbed in the past and had gone in new genesis directions due to erosion and colluvial conditions resulting from the unstable topography and frequent tectonic episodes.

Nitrogen and Phosphorus Accumulation in Pasture Soil from Repeated Poultry Litter Application

Poultry litter (PL) is a traditionally inexpensive and effective fertilizer to improve soil quality and agricultural productivity. However, over application to soil has raised concern because excess nutrients in runoff could accelerate the eutrophication of fresh water. In this work, we determined the contents of total phosphorus (P), Mehlich 3 extracted P, total nitrogen (N), ammonium (NH4)‐N, and nitrate (NO3)‐N, in pasture soils receiving annual poultry litter applications of 0, 2.27, 2.27, 3.63, and 1.36 Mg/ha/ yr, respectively, for 0, 5, 10, 15, and 20 years. Samples were collected from three soil depths (0–20, 20–40, and 40–60 cm) of the Hartsells series (fine‐loamy, siliceous, subactive, thermic, Typic Hapludults) on a 3–8% slope in the Sand Mountain region of north Alabama. PL application increased levels of total P, Mehlich‐3 extractable P, and total N significantly. However, the change in NH4‐N and NO3‐N contents by the PL application was not statistically significant. Correlation analysis indicated that the contents of total P, Mehlich 3 extracted P, and total N were more related to cumulative amounts of poultry litter applied than the years of application or annual application rates alone. This observation suggested that N and P from poultry litter accumulated in soil. Predicting the build‐up based on the cumulative amounts of PL application, rather than isolated factors (i.e., application year or rate), would improve the accuracy of evaluating long‐term impacts of poultry litter application on soil nutrient levels.

Initial Response of Soil Nutrient Pools to Prescribed Burning and Thinning in a Managed Forest Ecosystem of Northern Alabama

Forest management practices such as prescribed burning and thinning are commonly used to restore degraded forest communities in the Southern Appalachians. Prescribed treatments influence physical and chemical properties of soils and change the balance of nutrients such as carbon and nitrogen. This study was conducted to investigate the initial impacts of prescribed burning, thinning and a combination of prescribed thinning and burning on total carbon and nitrogen pools, as well as other properties, in soil and forest floor. Effects of these disturbance regimes were tested on Typic Hapludults at the Bankhead National Forest in Northern Alabama. Results show that prescribed burning alone led to significant increases in total C and N contents in soil surface horizons. Burning alone also resulted in changes in exchangeable Na pools and significant increases in pH values throughout the study sites. Combination of prescribed thinning and burning did not result in significant changes in total C and N concentrations. However, significant increases in K and Na concentrations were observed in these sites. Prescribed thinning alone did not appear to impact total C and total N concentrations, soil acidity or exchangeable Ca and Mg concentrations, but caused significant increases in Na and decreases in K concentrations. Results of the study indicated that prescribed burning alone appeared to have a stronger impact on total C and N pools than a combination of prescribed thinning and burning. Use of prescribed thinning alone did not have any effect on total C and N pools in soils and forest floor. While prescribed burning alone and a combination of thinning and burning led to changes in exchangeable K and Na pools, no change was detected in either Ca or Mg concentrations.

Morphology, mineralogy and classification of soils developed on different parent material in Mussoorie forest division, Uttarakhand, India

Based on reconnaissance soil survey of Kempty Range of Mussoorie Forest Division, Uttarakhand, five soil profiles in different blocks were selected for determining their morphological, physicochemical and mineralogical characteristics. The morphological characteristics show considerable variation in the nature and degree of horizon development. Light and heavy mineral fractions constituted 70 and 30 per cent of total fine sand fractions respectively. Various minerals identified in the light sand fractions included quartz, feldspars and mica (muscovite). In all the pedons studied quartz was the dominating mineral. Heavy mineral fractions comprised opaque minerals, biotite the presence of low to moderate amount of weatherable minerals suggesting their podsolic nature. Clay fractions were characterized by micas and illite as the dominant clay mineral associated with appreciable amount of kaolinite and chlorite and the small amount of mixed layer silicate mineral, vermiculite, montimorillonite and quartz. Soils of the study area belonged to Typic Paleudoll (Kempty Block), Typic Argiudoll (Sainj Block), Typic Paleudult (Mailgarh Block), Typic Hapludult (Kheragarh Block) and Typic Argiudoll (Gandiyala Block). All these polypedons are members of fine loamy, mixed, messic family. These soils developed from different parent materials are in equilibrium with geogenic factors. Mollisols occur on limestone, dolomite, quartzite and slate whereas Ultisols occur on phyllite, shale, sandstone, quartzite, etc.

A New Method of Poultry Litter Application to Perennial Pasture: Subsurface Banding

Recently, incorporation of poultry litter by subsurface band application into pasture has been shown to reduce surface runoff transport of nutrients; however, data to evaluate the impact of this potential management strategy on forage production, forage nutrient concentrations, or the accumulation of soil nutrients after multiyear applications is limited. Therefore, two experiments, one in bermudagrass [Cynodon dactylon (L.) Pers.] and one in tall fescue (Festuca arundinacea Schreb.) were initiated in which treatments included (i) a standard commercial fertilizer application, (ii) a surface broadcast litter application, (iii) poultry litter applied in subsurface bands placed 25 cm apart, and (iv) poultry litter applied in subsurface bands placed 38 cm apart. The experiments were conducted for 3 yr on a Hartsells (fine‐loamy, siliceous, subactive, thermic Typic Hapludult) soil at Crossville, AL, and showed that subsurface band applications resulted in forage yields equivalent to those achieved by conventional broadcast litter applications. Subsurface band applications also did not generally impact forage N, P, and K concentrations compared with surface litter applications. Three years of subsurface band applications to a depth of approximately 4 cm did not significantly alter the Mehlich 3 extractable nutrient content of soils collected at a depth of 0 to 15 cm. Data suggest, however, that subsurface band application would allow increases in subsurface movement of nutrients, as was evidenced by increased Cu concentrations at the 15‐ to 30‐cm depth. The data suggest that the environmental benefits of subsurface band application of poultry litter into grass production systems are achieved without detrimental impacts on forage productivity or nutrient concentrations.

‘Coastal’ and ‘Tifton 44’ Bermudagrass Availability on Animal and Pasture Productivity

Hybrid cultivars of bermudagrass [Cynodon dactylon (L.) Pers.] are a major feed source for ruminants across the southeastern United States. This 4‐yr experiment compared animal and pasture performance of ‘Coastal’ and ‘Tifton 44’ bermudagrasses over three canopy heights designated as short (5.6 cm), medium (10.1 cm), and tall (13.1 cm). The relationship of canopy height to ingestive mastication and canopy characteristics was also studied. Soil was a Cecil clay loam (clayey, Kaolinitic thermic Typic Hapludult). Pastures were continuously stocked using variable stocking to maintain the targeted canopy heights. Herbage mass (to soil surface) was similar between Coastal and Tifton 44 (T44) within each canopy height averaging 2.36, 4.08, and 5.25 Mg ha−1. Steer average daily gain (ADG) was greater (P = 0.09) from T44 than Coastal (0.58 vs. 0.51 kg) but no differences were noted in pasture productivity. Increasing herbage mass linearly increased (P < 0.01) ADG (0.40–0.59 kg) but reduced (P < 0.01) stocking rate (16.1–11.2 steers ha−1), which influenced animal days (1810–1079 d ha−1), weight gain (1057–786 kg ha−1), and effective feed units (6392–4452 kg ha−1). Steer ADG increased (P = 0.01) from short to medium canopy height (0.40–0.64 kg) with little change between medium and tall canopy height (0.64–0.59 kg). Tifton 44 pasture is of greater quality than Coastal giving greater ADG but both were productive producing about 1100 kg of gain ha−1 when effectively managed and utilized.

Soil nitrogen conservation with continuous no-till management

Tillage management is an important regulator of organic matter decomposition and N mineralization in agroecosystems. Tillage has resulted in the loss of considerable organic N from surface soils. There is potential to rebuild and conserve substantial amounts of soil N where no-till management is implemented in crop production systems. The objectives of our research were to measure N conservation rate with continuous no-till management of grain cropping systems and evaluate its impact on mineralizable and inorganic soil N. Samples were collected from 63 sites in production fields using a rotation of corn (Zea mays L.)—wheat (Triticum aestivum L.) or barley (Hordeum vulgare L.)—double-crop soybean (Glysine max L.) across three soil series [Bojac (Coarse-loamy, mixed, semiactive, thermic Typic Hapludults), Altavista (Fine-loamy, mixed semiactive, thermic Aquic Hapludults), and Kempsville (Fine-loamy, siliceous, subactive, thermic Typic Hapludults)] with a history of continuous no-till that ranged from 0 to 14 yrs. Thirty-two of the sites had a history of biosolids application. Soil cores were collected at each site from 0–2.5, 2.5–7.5 and 7.5–15 cm and analyzed for total N, Illinois soil N test-N (ISNT-N), and [NH4 + NO3]-N. A history of biosolids application increased the concentration of total soil N by 154 ± 66.8 mg N kg−1 (310 ± 140 kg N ha−1) but did not increase ISNT-N in the surface 0 – 15 cm. Continuous no-till increased the concentration of total soil N by 9.98 mg N kg−1 year−1 (22.2 ± 21.2 kg N ha−1 year−1) and ISNT-N by 1.68 mg N kg−1 year−1 in the surface 0–15 cm. The implementation of continuous no-till management in this cropping system has resulted in conservation of soil N.

Soil carbon sequestration with continuous no-till management of grain cropping systems in the Virginia coastal plain

Carbon sequestration in agroecosystems represents a significant opportunity to offset a portion of anthropogenic CO 2 emissions. Climatic conditions in the Virginia coastal plain and modern production practices make it possible for high annual photosynthetic CO 2 fixation. There is potential to sequester a substantial amount of C, and concomitantly improve soil quality, with the elimination of tillage for crop production in this region. The objectives of our research were to: (1) measure C sequestration rate with continuous no-till management of grain cropping systems of the Virginia middle coastal plain; (2) determine the influence of biosolids application history on C content and its interaction with tillage management; and (3) evaluate the impact of continuous no-till C stratification as an indicator of soil quality. Samples were collected from 63 sites in production fields using a rotation of corn ( Zea mays L.)–wheat ( Triticum aestivum L.) or barley ( Hordeum vulgare L.)/soybean double-crop ( Glysine max L.) across three soil series [Bojac (coarse-loamy, mixed, semiactive, thermic Typic Hapludults), Altavista (fine-loamy, mixed semiactive, thermic Aquic Hapludults), and Kempsville (fine-loamy, siliceous, subactive, thermic Typic Hapludults)] with a history of continuous no-till management ranging from 0 to 14 years. Thirty-two of the sites had a history of biosolids application. Five soil cores were collected at each site from 0–2.5, 2.5–7.5 and 7.5–15 cm and analyzed for bulk density and soil C. Bulk density in the 0–2.5 cm layer decreased and C stratification ratio (0–2.5 cm:7.5–15 cm) increased with increasing duration of continuous no-till due to the accumulation of organic matter at the soil surface. A history of biosolids application resulted in an increase of 4.19 ± 1.93 Mg C ha −1 (0–15 cm). Continuous no-till resulted in the sequestration of 0.308 ± 0.280 Mg C ha −1 yr −1 (0–15 cm). Our results provide quantitative validation of the C sequestration rate and improved soil quality with continuous no-till management in the region using on-farm observations.

Morphology, lacunarity and entropy of intra-aggregate pores: Aggregate size and soil management effects

In a hierarchical model of soil structure, small size aggregates are less porous and contain smaller pores than larger aggregates. Fractal dimensions obtained from aggregate mass-ratio data seem to confirm a hierarchical organization of intra-aggregate pores that may be altered by tillage. The objective of this study was to use image analysis to directly characterize the morphology and spatial arrangement of intra-aggregate pores as a function of aggregate size and soil management. The surfaces of wooded and cultivated sites of a Typic Hapludults, an Aquic Hapludults and an Ultic Hapludalfs were sampled. Hand-picked aggregates from each site were separated in three size groups having masses of 5–6 g ( M 5), 2 g ( M 2) and 0.5 g ( M 0.5) and 6 aggregates per size group were resin-impregnated and imaged. Measurements on the 108 images included pore shape (planar, irregular and rounded), the geometric mean of the Feret (longest) pore diameter (GMFD) for each shape group and pores greater than 300 μm 2, and properties of the spatial arrangement of pores characterized with a normalized entropy and a lacunarity function. Distributions of GMFD by shape were quantified with the Kullback–Leibler Divergence and a chi-square test. Planar pores had greater GMFD values than irregular and rounded pores and their distributions were significantly different ( P < 0.05) across aggregate sizes. Parameters from the normalized entropy and lacunarity functions were significantly ( P < 0.05): 1) different in cultivated than in wooded sites and in the M 0.5 than in the M 5 and M 2 size groups (entropy function only) and 2) correlated to the porosity, pore number and to GMFD (entropy function only) values of each pore shape group. The lacunarity function revealed a fractal or multifractal structure of pores within aggregates, while the normalized entropy function detected significantly lower entropy in aggregates of the M 0.5 size group. The GMFD of planar pores showed well defined trends with fractal parameters obtained from data (reported elsewhere) on aggregate mass-ratio. These results are evidence of differences in the organization and distribution of pores within aggregates of different sizes that may be of a hierarchical (fractal) type.

Relações entre os tipos e indicadores de acidez do solo em lavouras no sistema plantio direto na região do Planalto do Rio Grande do Sul

A recente mudança no sistema de cultivo do solo ocorrida no Brasil, passando do preparo convencional (PC) para o sistema plantio direto (SPD), altera o funcionamento do solo. No solo cultivado no SPD, as relações se estabelecem no tempo e são preservadas aumentando a complexidade do funcionamento do sistema, enquanto no PC estas relações são freqüentemente destruídas. Assim, devido à formação de gradientes de acidez, de matéria orgânica e de nutrientes a partir da superfície do solo é possível que se altere a magnitude das relações entre os tipos e os indicadores de acidez e que a camada de 0-20 cm de profundidade não seja a mais adequada para representar o estado de fertilidade de solo no SPD. Por essa razão, este trabalho foi conduzido com o objetivo de estudar as relações entre os tipos de acidez e os seus principais indicadores em duas camadas de solo em lavouras no SPD consolidado na região do Planalto Riograndense. Foram selecionadas seis lavouras, coletando-se, em cada uma, amostras de solo em 20 locais, nas camadas de 0-10 e 0-20 cm de profundidade, para a determinação dos tipos e dos indicadores de acidez. As relações entre os tipos e os indicadores de acidez do solo não se diferenciaram nas camadas avaliadas. Assim, para a região estudada e para o sistema de cultivo utilizado, qualquer das camadas (0-10 ou 0-20 cm) pode ser utilizada para fins de recomendação de calagem.

Corn stover removal impacts on micro-scale soil physical properties

Crop residues are a potential source for biofuel production. Yet, impacts of removal of corn ( Zea mays L.) stover and other residues as biofuel feedstocks on micro-scale soil properties affecting the behavior of the whole soil are not well understood. Data on both macro- and micro-scale soil properties under different scenarios of stover management are needed to define the threshold levels of stover removal. Previous studies on stover removal impacts on soil properties have primarily focused on macroscale properties and little or not on microscale properties. Thus, this study was designed to assess impacts of annual stover removal for 3 consecutive years at rates of 0, 25, 50, 75, and 100% on soil physical properties at the aggregate level under no-tillage (NT) continuous corn systems in a Rayne silt loam (RSL) (fine-loamy, mixed, active, mesic Typic Hapludult) with 10% slope, Celina silt loam (CSL) (fine, mixed, active, mesic Aquic Hapludalfs) with 2% slope, and Hoytville clay loam (HCL) (fine, illitic, mesic Mollic Epiaqualfs) with < 1% slope in Ohio. Aggregates were sensitive to stover removal particularly in the 0- to 10-cm soil depth. Stover removal reduced aggregate stability, tensile strength (TS), water retention (WR), and subcritical water repellency, while it increased water sorptivity but had no effect on pore-size distribution within an aggregate. The interaction of aggregate stability, strength, and subcritical water repellency with aggregate water potential was highly significantly, indicating that the magnitude of changes in aggregate structural properties due to stover removal depended on the variable antecedent soil water conditions. The aggregate stability and strength decreased while water repellency increased with increasing water potential. Impacts of stover removal on the clayey soils were equal to or higher than those on silt loam soils. Removal at rates ≥ 25% reduced the raindrop kinetic energy (KE) required to break aggregates by 13 times at HCL, while removal at rates ≥ 50% reduced the KE by 2 to 3 times at RSL and CSL for air-dry aggregates. The KE and TS decreased with increasing soil water potentials. The TS was reduced by 10% to 30% at all water potentials at RSL, by 20% to 35% between − 0.1 and − 1.5 MPa, and by 2.2 times at − 166 MPa at CSL, and by 2 to 3 times between − 1.5 and − 166 MPa at HCL under complete stover removal. Removal of stover at rates ≥ 50% reduced subcritical water repellency by 2 to 10 times in all soils. Overall, stover removal altered micro-scale soil properties, and complete stover removal had the most detrimental effects. Based on the data from previous studies on macroscale soil properties and this study, stover removal adversely affects both macro- and micro-scale soil properties.

Goat Urine and Limestone Affect Nitrogen and Cation Distributions in an Acidic Grassland

Prior surface application of limestone may influence soil changes resulting from high rates of urine deposition occurring where goats (Capra aegagrus hircus L.) congregate. A quantity of limestone equivalent to 0 and 6720 kg ha−1 was surface applied to vegetated 45‐cm‐deep columns of a Typic Hapludult soil collected from an abandoned Fescue spp. grassland in southern West Virginia. Eighteen weeks after lime application, one, two, or three applications of urine supplying a total of 36, 98, or 177 g m−2 of N, respectively, were made. One and two applications of urine increased vegetative growth and decreased the amount of water leaching through the column, but the third addition damaged plants. The three‐addition treatment reduced the amount of N taken up by the plants, decreased transpiration, increased leachate volume, and resulted in a 12‐fold increase in the amount of N leached from the columns compared with the one‐application treatment. Leachate Ca, Mg, and K were increased by urine. Soil pH and extractable Ca and Mg were decreased by urine and increased by limestone, and extractable Al was increased by urine and decreased by limestone applications. Net amounts of N recovered as NH3 gas released to the atmosphere, N taken up into aboveground plant material, NH4+ and NO3− extracted from soil, and NH4+ and NO3− in drainage water ranged from 49 to 77% of the amount added. Surface application of limestone alleviated some of the detrimental effects of high rates of urine addition by increasing levels of pH, Ca, and Mg and reducing Al as deep as 28 cm in the profile.

Traffic Stress Effects on Bentgrass Putting Green and Fairway Turf

Creeping bentgrass (Agrostis stolonifera L.) has received more study and use as golf course turf than velvet bentgrass (A. canina L.). The objective of two field trials, managed as putting green and fairway turf, was to evaluate the performance of creeping and velvet bentgrass in mixed swards with annual bluegrass (Poa annua var. reptans Hausskn.) when subjected to traffic stresses. The trials were initiated on a sandy loam (fine‐loamy, mixed, mesic Typic Hapludult). Wear (no‐wear and wear) and compaction (no‐compaction and compaction) were applied in a factorial combination to 15 creeping or velvet bentgrasses. Turf quality, turf density, and bentgrass populations of cultivars were more susceptible to wear stress than compaction. Velvet bentgrass performed and resisted the spread of annual bluegrass better than most creeping bentgrasses. Cultivars that formed denser turf performed well in both trials; ‘Vesper’, ‘7001’, and ‘Penn A‐4’ had the best overall performance. Interactions indicated ‘SR 7200’, ‘Penn G‐2’, and ‘Providence’ were susceptible to compaction. ‘Pennlinks’ and ‘Penncross’ were ineffective at maintaining desirable bentgrass populations particularly in the putting green trial. Management strategies that minimize wear damage may have a greater impact on turf quality and bentgrass populations in mixed stands than practices intended to manage compaction, particularly on well‐drained soil.

Avaliação de atributos físicos e estoques de carbono e nitrogênio em solos com queima e sem queima de canavial

O Brasil é o maior produtor mundial de cana-de-açúcar, de modo que mudanças no seu manejo podem afetar sobremaneira o ambiente. Há quase um século, as pesquisas são baseadas em áreas sob queima da biomassa foliar (palhada) dessa cultura. Mas a supressão da queimada é um novo conceito no manejo da palhada. Portanto, há poucos resultados sobre o manejo desse material. O objetivo do estudo foi comparar teores de C e N e estabilidade de agregados e densidade do solo nos manejos com queima (Cq) e sem queima (Sq) da palhada. Estudou-se um solo argiloso (Latossolo Vermelho = LVdf) e dois solos arenosos (Argissolo Vermelho-Amarelo = PVAd e Neossolo Quartzarênico = RQo) submetidos aos manejos Cq e Sq. Em cada solo foi estabelecida uma área experimental em blocos ao acaso com seis repetições. A quantidade de palhada adicionada em três colheitas foi 40 t ha-1 em matéria seca e, um ano após a terceira colheita, a acumulação foi 4,5 t ha-1 (11 %) no LVdf e 3,6 t ha-1 (9 %) no RQo. Isso representou 1,60 e 1,35 t ha-1 em C e 0,022 e 0,021 t ha-1 em N, respectivamente. Houve aumento no teor de C nos solos Sq, concorrendo em seqüestro de C na camada 0-20 cm de 6,3 e 4,7 t ha-1, respectivamente em LVdf e RQo. Assim, a taxa de seqüestro de C no compartimento cobertura + solo (0-20 cm) foi de 2,63 e 2,02 t ha-1 ano-1 no LVdf e RQo, respectivamente. Também houve aumento no teor de macroagregados em solos Sq comparados a solos Cq: 814 e 693 g kg-1 no LVdf e 516 e 420 g kg-1 no RQo. Ocorreu compactação superficial no PVAd e RQo em decorrência do uso de máquina colhedora em solo Sq. Nos solos estudados, o manejo sem queima da cana-de-açúcar resultou em melhorias nas propriedades dos solos e promoveu seqüestro de C e N na cobertura e nas camadas superficiais dos solos.

Distribution of Copper, Zinc, and Phosphorus in Coastal Plain Soils Receiving Repeated Liquid Biosolids Applications

Continuous N-based application of biosolids contributes to a gradual increase of trace elements and P in soils. The objectives of this study were to assess the accumulation and vertical transport of Cu, Zn, C, N, and P within the profile of two coastal plain soils. Liquid (6-8% total solids) biosolids were applied to an Acredale silt loam (fine silty, mixed, thermic typic Ochraqualfs) and Bojac loamy sand (coarse loamy, mixed, thermic typic Hapludult) annually from 1984 to 1998. The repeated applications supplied 70, 204, and 3823 kg ha(-1) of Cu, Zn, and P, respectively, to the Acredale and 81, 225, and 4265 kg ha(-1) of Cu, Zn, and P, respectively, to the Bojac. The total C and N contents were not different than background levels in the Bojac soil and were slightly higher in the Acredale soil 7 years after cessation of biosolids application. Phosphorus, Cu and Zn are still concentrated in the top 0.25 m of the Acredale soil. Enrichment of P, Cu, and Zn were detected to the deepest soil increment in the coarse-textured Bojac soil. Approximately 20 to 40% of the Cu and Zn applied in the biosolids could not be accounted, which was likely due to a combination of leaching and incomplete extraction. Excessive Mehlich 1-P concentrations and a high degree of P saturation were found in amended soil, raising the potential for P release to runoff or leaching water.

Uso de poliacrilamida como estrategia de control de erosión en un suelo altamente erodado de Puerto Rico.

La alta sedimentación procedente de terrenos dedicados a la agricultura y la construcción es una de las principales fuentes de contaminación de los cuerpos de agua superficiales de Puerto Rico. El uso de polímeros amónicos de poliacrilamida (PAM) ha ganado rápido reconocimiento como una alternativa costo-efectiva para el control de la erosión. En este estudio evaluamos la efectividad de varias formulaciones y dosis de PAM aniónico en un suelo altamente meteorizado del trópico (Corozal Arcilloso—Typic Hapludult) en condiciones de alta pendiente (20%). Se llevó a cabo una serie de experimentos con cajas de escorrentía siguiendo el protocolo del Proyecto Nacional de Simulación de Lluvia. Se evaluaron tres formulaciones de PAM: SOILFLOCâ"¢ 300 E, SOILFIXâ"¢ LDP, y una formulación sintética (PAMAld) de la compañía Aldrich Chemical. Cada formulación se evaluó en las siguientes dosis: 0 (control), 20 kg/ha, 80 kg/ha, y 120 kg/ha de ingrediente activo. Los experimentos de lluvia simulada se realizaron a uno, dos, ocho, 30, y 60 días luego de la aplicación del polímero. Las dosis de PAM de 80 y 120 kg/ha redujeron significativamente la concentración de sedimentos en el agua de escorrentía comparadas con el control y la dosis de 20 kg/ha. En sus dosis más altas todas las formulaciones de PAM redujeron la concentración de sedimentos en el agua de escorrentía en más de 75% comparado con la del control en todos los eventos de lluvia realizados. La efectividad de PAM a la dosis de 20 kg/ha se perdió luego del segundo evento de lluvia. Durante el tercer evento de lluvia la reducción en la concentración de sedimentos (comparado con la del control) fue menos de 50% en el caso de la formulación PAM-Ald y menos de 20% en el caso de SoilFloc para la dosis de 20 kg/ha. El tiempo requerido para la generación de escorrentía dependió grandemente del contenido de humedad del suelo. Durante los dos últimos eventos de lluvia (30 y 60 días luego de la aplicación de PAM), el tiempo requerido para la generación de escorrentía se afectó significativamente por las dosis de PAM. En el tratamiento control y en el de la dosis más baja de PAM la escorrentía ocurrió más rápido que en aquéllos con las dosis más altas de PAM. Estos resultados pudieran atribuirse a los efectos de sellado de superficie y aumentos en la formación de surcos o zanjillas en la superficie del control y en la de la dosis más baja (20 kg/ha) de PAM. Sesenta días luego de la aplicación del polímero, los estimados de producción de sedimentos cumulativos para un evento de 30 minutos de escorrentía fueron de 2.3 Mg/ha para el tratamiento control vs. 0.18, 0.07, y 0.08 Mg/ha para las dosis de 120 kg/ha de SoilFloc, SoilFix y PAM-Ald, respectivamente.