Typic Hapludoll Research Articles

Effects of tillage and crop rotation on soil microbial residues in a rainfed agroecosystem of northeast China

Agricultural management has significant impacts on soil microorganisms, which in turn influence soil relevant processes including soil organic matter (SOM) turnover. Amino sugars, as a microbial residue biomarker, are highly involved in microbial-mediated SOM cycling. However, the response of microbial-derived amino sugars to changes in soil management practices is poorly characterized in the arable soils (Typic Hapludoll, USDA Soil Taxonomy) in northeast China. The objective of this study was to assess the effects of soil tillage (conventional tillage CT vs. no tillage NT) and crop rotation (continuous corn ( Zea mays L.) monoculture vs. corn–soybean [ Glycine max (L.) Merr.] rotation) on the accumulation of amino sugars in this region. The following hypotheses were tested: (1) in an agroecosystem, tillage and crop rotation influence the accumulation of microbial residues in soils; (2) responses of fungal and bacterial cell wall residues to the practices are different, i.e., fungal-derived cell wall residues more benefited by no-tillage practices than bacterial. Implementation of no-tillage practices for 6 years significantly increased soil total amino sugars with an increase of 59% as compared with conventionally tilled plots ( P < 0.05). This highlights the positive effects of NT that promotes the accumulation of microbial-derived organic matter. The ratios of glucosamine to muramic acid in the NT soils across three soil depths significantly exceeded those in the respective CT soils due to a higher enrichment of glucosamine. This confirms our hypothesis that the microbial community shifted towards fungal dominance under NT and the phenomenon was more pronounced within the 0–5 cm layers. When NT systems were evaluated, the type of crop rotation used had a significant influence on the soil amino sugar content. Significant enrichment of total amino sugars (1042–1317 mg kg −1 soil) occurred in the continuous corn monoculture system as compared with the corn–soybean rotation field (943–1112 mg kg −1 soil) in the soil layers from 0 to −20 cm. Data obtained suggest that NT practices combined with continuous high C inputs can be adopted as an effective strategy to improve the cropland SOM in northeast China. Our results also indicate that it is possible to use amino sugars as an indicator to assess the changes in microbial community within a given ecosystem.

Subtropical Soil Chronosequence on Holocene Marine Terraces in Eastern Taiwan

The Coastal Range in eastern Taiwan is characterized by rapid uplift at a rate of about 5 mm yr−1 because of active arc‐continent collision since the Mio‐Pliocene. The Coastal Range includes three main levels of Holocene marine terraces, labeled the first, second, and third levels descending to the coast. The soils that have developed on the terraces provide a chronosequence for pedogenic studies. Thirteen soil pedons formed from conglomerate associated with tuff were sampled along three transects in the central and southern part of the eastern coast of Taiwan near the localities of Chang‐Bin, Cheng‐Gong, and Du‐Lan. The soils of the oldest terrace (first level) are mainly Typic Hapluderts with one Typic Hapludoll; the soils of the intermediate terrace (second level) are Vertic or Typic Hapludolls; and the soils of the youngest terrace (third level) are Typic Udipsamments. The degree of development of these soils can be determined from horizon index (HI), weighted profile development index (WPDI), weighted mean profile (WMP) clay, WMP silt, WMP sand, and WMP cation exchange capacity with correlation coefficients (r) &gt;0.6 by linear or logarithmic functions. Comparisons of the chronofunctions based on WMP clay data in subtropical and Mediterranean climates suggest that climatic conditions not only control weathering intensity but also influence rates of soil development. The pedogenic evidence in this study supports the correlation of terraces suggested by previous geomorphic and tectonic studies. The anomalous, relatively weaker degree of soil development on the oldest terrace at Du‐Lan supports the conclusion that uplift rates in the Du‐Lan area are greater than at Chang‐Bin and Cheng‐Gong.

Impact of biochar amendments on the quality of a typical Midwestern agricultural soil

Biochar, a co-product of thermochemical conversion of lignocellulosic materials into advanced biofuels, may be used as a soil amendment to enhance the sustainability of biomass harvesting. We investigated the impact of biochar amendments (0, 5, 10, and 20 g-biochar kg − 1 soil) on the quality of a Clarion soil (Mesic Typic Hapludolls), collected (0–15 cm) in Boone County, Iowa. Repacked soil columns were incubated for 500 days at 25 °C and 80% relative humidity. On week 12, 5 g of dried and ground swine manure was incorporated into the upper 3 cm of soil for half of the columns. Once each week, all columns were leached with 200 mL of 0.001 M CaCl 2. Soil bulk density increased with time for all columns and was significantly lower for biochar amended soils relative to the un-amended soils. The biochar amended soils retained more water at gravity drained equilibrium (up to 15%), had greater water retention at − 1 and −5 bars soil water matric potential, (13 and 10% greater, respectively), larger specific surface areas (up to 18%), higher cation exchange capacities (up to 20%), and pH values (up to 1 pH unit) relative to the un-amended controls. No effect of biochar on saturated hydraulic conductivity was detected. The biochar amendments significantly increased total N (up to 7%), organic C (up to 69%), and Mehlich III extractable P, K, Mg and Ca but had no effect on Mehlich III extractable S, Cu, and Zn. The results indicate that biochar amendments have the potential to substantially improve the quality and fertility status of Midwestern agricultural soils.

Integral Study of Atrazine Behaviour in Field Lysimeters in Argentinean Humid Pampas Soils

Atrazine behavior during crop maize (Zea mays L.) production in soils of Argentine humid pampas was investigated. Lysimeters (3.3 x 3.3 x 1.4 m) with a Typic Argiudoll (Pergamino) and others with a Typic Hapludoll (Junin) were monitored for drainage water content and atrazine concentrations in soil and water. Soil profiles were sampled in four depths in three dates, and water drainage pooled in four periods. Most of atrazine loss in drainage occurred within 30 d of atrazine application being 0.13% and 0.03% of the total atrazine applied for Pergamino and Junin, respectively. Under laboratory conditions half-life average in both profiles was 16 d. Atrazine extractable residues (AER) in lysimeters showed differences in quantity and distribution between both profiles. Extractable residues were 25.7 (Pergamino) and 69.4 g ha -1 (Junin). At the 30 th day of application, AER represented 25% of total AER in Junin and 88% in Pergamino in the first 30 cm. Occurrence of preferential flow through the B t horizon (Pergamino) may explain differences detected. High proportion of AER in Junin profile suggests low atrazine affinity and should be followed through time in order to evaluate actual stability of these residues and if they constitute a potential risk for aquifers.

Effect of long‐term combined nitrogen and phosphorus fertilizer application on 13C CPMAS NMR spectra of humin in a Typic Hapludoll of northeast China

SummaryBecause of its insolubility, heterogeneity and structural complexity, humin is the least understood among the three fractions of soil humic substances. This research aimed to evaluate the long‐term effect of combined nitrogen and phosphorus (NP) fertilizer addition on the chemical structure of humin under maize (Zea mays L.) monoculture in a Typic Hapludoll of northeast China. Soil samples were collected 12 and 25 years after the initiation of the fertilizer treatment. Soil humin was isolated using NaOH‐Na4P2O7 extraction to remove humic and fulvic acids, which was followed by HF‐HCl treatment to remove most of the inorganic minerals. Solid‐state 13C cross‐polarization magic angle spinning nuclear magnetic resonance (13C CPMAS NMR) spectroscopy was used to characterize the chemical structure of the humin isolates. Results showed that the organic carbon (C) content of humin increased after NP fertilizer addition, compared with a no‐fertilizer (CK) treatment. 13C CPMAS NMR indicated that O‐alkyl C and aromatic C of humin decreased, while alkyl C and the ratios of alkyl C/O‐alkyl C, aliphatic C/aromatic C and hydrophobic C/hydrophilic C all increased in the NP fertilizer treatment. The long‐term application of NP fertilizer changed the molecular structure of soil humin to be more alkyl and hydrophobic, and was thus beneficial to the sequestration and stability of organic C in soil.

Soybean Residue Effect on Carbon Fractions and Gaseous Nitrogen Losses at Contrasting Moisture Contents

Most published studies related to crop effects on denitrification are not continuous and are based on the growing period. The objective of this work was to evaluate the effect of different amounts of soybean stubble, under different soil moisture contents, on gaseous nitrogen (N) losses by denitrification from an agricultural soil. The following soil moisture treatments were reached by adding distilled water to soil cores of a typic Hapludoll: 50 and 100% of water‐filled porosity space (WFPS). Residue treatments included no application of residues, amendment with 2600 kg ha−1 of soybean residues, and amendment with 5200 kg ha−1 of soybean residues. Cumulative nitrous oxide + dinitrogen (N2O + N2) emissions displayed great variability, ranging between 0 and 581.91 µg N kg−1, which represented 0 to 3.93% of the N residue applied. Under 50% WFPS moisture conditions, statistical differences in cumulative N2O + N2 emissions between residue treatments were not detected (p = 0.21), whereas at saturation conditions, cumulative N2O + N2 emissions decreased with the application of increasing amounts of soybean residues (p = 0.017). Daily and cumulative N2O + N2 emissions significantly increased as soil moisture increased, except at soils amended with 5200 kg ha−1 of soybean residues; this lack of statistical difference was probably due to the immobilization of native mineral N. Under 50% WFPS soil moisture contents, aeration seemed to be the main factor controlling redox conditions, limiting the denitrification process, and preventing differences in N emissions between residue treatments. The application of soybean residues to saturated soils notably decreased N2O + N2 emissions by denitrification through a strong mineral N immobilization into organic and nondenitrifiable forms.

Poultry Manure Supply of Potentially Available Nitrogen with Soil Incubation

Poultry production is an important and growing livestock industry in Iowa and use of poultry manure as a crop N resource is increasing. Aerobic incubation studies were used to examine potentially available nitrogen (PAN) from poultry manure using two contrasting Iowa agricultural soils, a Clarion loam (fine‐loamy, mixed, superactive, mesic Typic Hapludolls) and Canisteo clay loam (fine‐loamy, mixed, superactive, calcareous, mesic Typic Endoaquolls). Two consecutive incubation experiments were conducted, each using the same soils and treatments. Incubation 1 used an approximate rate of 86 mg total N kg−1 incubated for 112 d, and Incubation 2 used an approximate rate of 200 mg total N kg−1 incubated for 84 d. Incubation 2 included more frequent initial sampling. Nitrogen sources included urea, uric acid, and two sources of poultry manure, chicken (Gallus domesticus) and turkey (Melleagris gallopavo) obtained from local production facilities. Soil samples were collected at multiple times during incubation and inorganic NH4+–N and NO3−–N concentrations measured. The accumulation of NO3−–N was used to estimate PAN. The poultry manure sources provided high levels of PAN, 66% of total manure N for chicken and 55% for turkey. These values were lower than those found for urea and uric acid. The majority of the NO3−–N accumulation occurred within 7 d of incubation, with no increase after 14 d. This indicates that considerable NO3−–N used to estimate PAN originated from the combined NH4+–N and uric acid–N components of the poultry manures. However, water soluble nitrogen (WSN) represented approximately 66 and 58% of total N for the chicken and turkey manure, respectively, which are higher than the NH4+–N plus uric acid–N fractions. These WSN levels are close to the estimated PAN values for each manure source. This indicates that poultry manure analysis for WSN could improve the estimation of crop available–N compared to NH4+–N or a fraction of total N.

Early Incidence of Soybean Seedling Pathogens in Iowa

Soybean [Glycine max (L.) Merr.] seed yield is often limited by root‐infecting pathogens. This study was conducted to determine the prevalence of three root‐infecting seedling pathogens in a fumigated vs. a nonfumigated soil, to determine if incidence is greater in cultivars that lack resistance to soybean cyst nematode (Heterodera glycines Ichinohe, SCN), and how incidence of these pathogens relates to yield. From 2004 through 2006, a 2 ha section of a field was fumigated each year with a mixture of 1,3 dichloropropene + chloropicrin on a Webster clay loam at Nevada (fine‐loamy, mixed, superactive, mesic Typic Endoaquolls), and on a Salix silty clay loam at Whiting (fine‐silty, mixed, superactive, mesic Typic Hapludolls), IA. Average incidence in the nonfumigated sites (determined by enzyme linked immunosorbent assay [ELISA] tests) was 86, 47, and 9% for Pythium spp., Rhizoctonia solani, Phytophthora sojae, respectively. Fumigation increased yield by 10%, reduced Pythium spp. incidence 27%, and no reductions in incidence of R. solani and P. sojae were detected. Incidence of Pythium spp. and P. sojae was less for cultivars with resistance to SCN. Negative correlations were found of yield with root health ratings (−0.43), SCN initial populations (−0.37), the presence of Pythium spp. (−0.28), and P. sojae (−0.15). Pythium spp. were more prevalent than R. solani and P. sojae in soybean seedlings in Iowa, and it was more related to yield than the other two pathogens. More research is needed to investigate the possibility of SCN‐susceptible cultivars being exposed to greater Pythium spp. and P. sojae damage which may influence yield.

Plant‐Available Nitrogen from Poultry Manure as Affected by Time of Application

Appropriate poultry manure management is essential to ensure maximum crop N utilization and reduce risk of negative environmental impact. This study was conducted to evaluate the effect of three application times (late fall, winter, and spring preplant) on N availability from two sources of poultry manure [chicken (Gallus domesticus) and turkey (Melleagris gallopavo)] for corn (Zea mays L.) production. Manure was applied based on total N, intending to supply 84 and 168 kg total N ha−1. Urea fertilizer was applied at the same time as the manure at six rates (0, 34, 67, 100, 134, 168 kg N ha−1). Soil classification used for the study was primarily Clarion (fine‐loamy, mixed, superactive, mesic Typic Hapludolls) and Nicollet (fine‐loamy, mixed, superactive, mesic Aquic Hapludolls). Effect of application timing was determined by response in grain yield, grain N uptake (GNU), leaf chlorophyll meter (CM) reading, and soil NO3−–N measured in early June. Soil NO3−–N concentrations were greater for manure and fertilizer N applied in spring compared with fall and winter application, but the same for both poultry manure sources. Grain yield, GNU, and CM reading response to manure N were not different among either poultry manure sources or application timings. Furthermore, estimated manure plant N availability was not different among poultry manure sources or time of application. Overall first year crop‐available N from poultry manure, based on fertilizer N equivalence, using grain yield, GNU, and CM readings was estimated at 43 to 53% of total N. The supply of available N to corn was not affected by poultry manure application timing despite different lengths of time to crop uptake or delayed incorporation with winter application.

Accumulation and Movement of Four Potentially Toxic Elements in Soils Throughout Five Years, During and After Biosolid Application

In this research, we have studied the accumulation of four PTEs (Cadmium, copper, lead and zinc) during and after biosolid application, in two soils with different clay content and their eventual movement with depth. The study was performed in the Province of Buenos Aires, Argentina, on a Typic Argiudoll and on a Typic Hapludoll. Treatments were: control and biosolid application, at doses of 14 Mg ha -1 year -1 (dry matter). There were two types of sampling: (i) Topsoil samp ling, at 0- 0.15 m depth, taken throughout five years and (ii) Depth soil sampling at regular intervals of 0.33 m from top soil to 3 -4 m depth, taken two years after biosolid application. All samples were taken on April. PTEs, extracted hydrochloric, sulfuric and nitric acids (total) or extracted with DiethyleneTriaminePentaacetic acid-DTPA (available), were determined by ICP. Total concentrations of PTEs in topsoils of both soils did not increase significantly due to biosolid application. The exception was the significantly high Pb concentration in the Typic Hapludoll. DTPA extractable metals showed some concentration changes throughout the studied period. Total and available PTEs did not show mobility with the depth of both soils. The exception was total Cd in the Typic Argiudoll, which moved in depth. With only those two exceptions, there is neither PTEs accumulation in topsoils nor PTEs movements in soil depth. The first could be attributed to biosolid composition and dosage used in the region. The lack of movement in depth appears more related to the characteristics of the studied soils.

Root lodging in sunflower. Variations in anchorage strength across genotypes, soil types, crop population densities and crop developmental stages

Root lodging is an important adversity affecting sunflower ( Helianthus annuus L.) production in Argentina under current husbandry practices, and may limit progress towards the achievement of higher yields via increased plant population density. Although there are perceptions that lodging susceptibility varies across developmental stages, crop population densities, genotypes and soil types, these perceptions have not been tested for sunflower using a standardized experimental protocol. This study aimed at: (1) identifying the sources of the variation in root lodging susceptibility in response to variations in crop population density in two genotypes of reputedly different susceptibility; (2) detecting the crop developmental stages most susceptible to root lodging; and (3) examining the relationships between root failure moment, root plate diameter and soil shear strength. We mechanically induced lodging at three developmental stages in plants rooted in pre-wetted plots. The crops were grown at 5.6 plants m −2 over 3 years on either Typic Argiudoll or Typic Hapludoll soils and at 3, 5.6, 10 and 16 plants m −2 on a Typic Argiudoll. The force needed to induce root lodging (root failure moment) and root plate diameter varied across genotypes, plant densities and developmental stages. Root failure moment and root plate diameters were greater ( p < 0.05 for both variables) in the resistant hybrid across the three development stages and almost all crop population densities. For both hybrids, the most susceptible development stage was R2, and root failure moment and root plate diameter diminished ( p < 0.05) as crop population density increased. Although root failure moment did not differ between soil types, root plate diameter was greater ( p < 0.0001) in the coarser soil. The relationship between root failure moment and the product of root plate diameter cubed by soil shear strength (a measure of plant anchorage strength) for both hybrids, both soil types, and all crop population densities could be described by a single linear relationship ( y = 0.2382 x; R 2 = 0.812; p < 0.025).

Effect of Tillage and Nitrogen Rate on Corn Yield and Nitrogen and Phosphorus Uptake in a Corn‐Soybean Rotation

Understanding tillage, N, and P interactions can contribute to improved N and P utilization and crop response. This study examined the interaction effects of tillage and N rate of two N sources on N and P uptake by corn (Zea mays L.). The study was conducted on Kenyon loam (fine loamy, mixed, mesic Typic Hapludolls) soil at the Iowa State University Northeast Research and Demonstration Farm near Nashua, IA. A randomized complete block design with a split‐plot arrangement in three replications was used for the two separate N source experiments. The tillage systems consist of no‐tillage (NT), strip‐tillage (ST), and chisel plow (CP) as main plots. Within each tillage four N rates (0, 85, 170, and 250 kg N ha−1) were assigned as subplots for each N source of manure (total N) and fertilizer (anhydrous ammonia) in a corn‐soybean [Glycine max (L.) Merr.] rotation. Tillage and increase in N rate beyond 85 kg ha−1 had no effect on corn grain yield with both N sources. Tillage × N rate had a significant effect on plant N and P uptake, especially at early growth stages with both N sources. Recovery percentage of applied N across all tillage systems and N rates was 40% and 27% for manure and fertilizer sources, respectively, at the 12th‐leaf growth stage of corn (V12). Plant N and P uptake at V12 growth stage was 44% and 37%, respectively, across tillage systems, N sources, and N rates. The findings indicate that the N rate and seasonal variability have more influence on plant N and P uptake than does the tillage system.

Changes in the atrazine extractable residues in no-tilled Mollisols

The effect of application dose and soil organic matter (SOM) stratification on changes in atrazine (6-chloro- N 2-ethyl- N 4-isopropyl-1,3,5-triazine-2,4-diamine) extractable residues (ER) were investigated. Two soils [Entic Haplustoll (EH) and Typic Hapludoll (TH)] with contrasting SOM content and form and without previous atrazine exposure were selected. Sampling was carried out at two depths: 0–2 and 2–5 cm. Atrazine ER were measured at 0, 3, 7, 14, 28, and 56 days in laboratory incubation. Atrazine concentration recovered 1 h after of its application ( C t0 ) was used as an index of the soil capacity to reduce the atrazine extractable fraction. SOM stratification was studied by means of physical fractionation. In both soils, the higher OC concentration was found in the 200–2000 μm fraction (OC f 200–2000 ). Soils differed in terms of the OC f 50–200 /OC f 200–2000 ratio. This ratio increased with depth in EH soil: 0.23 (0–2 cm) and 2.00 (2–5 cm). In TH soil, the ratio was 0.80 (0–2 cm) and 0.50 (2–5 cm). The t 1/2 values ranged from 9 to 19 days, depending on soil type and atrazine application dose. The upper layer C t0 and k were higher for higher atrazine doses. Implementation of a split application dose of atrazine may be an effective alternative to extend its half-life in soil solution, as well as involving a lower potential risk of soil accumulation or vertical movement in the soil profile towards deep soil layers and groundwater.

Soil genesis along a chronosequence on marine terraces in eastern Taiwan

Soil chronosequences developed on elevated marine terraces are ideal for studying changes in soil-forming processes with time. The coastal range of eastern Taiwan is a product of active arc–continent collision. Vertisols, Mollisols and Entisols are generally found on the different levels of marine terraces herein, but no detailed investigations of soil chronosequence have been conducted by integrating field morphology, physio-chemical characterization, micromorphology and mass-balance interpretations. Five soil pedons were selected on the three marine terraces including Tt-1 and Tt-2 pedons (Typic Hapluderts) on the first higher level with the oldest soil age (9–10 ka), Tt-3 (Vertic Hapludolls) and Tt-4 pedons (Typic Hapludolls) on the second intermediate level (5–6 ka), and Tt-5 pedon (Typic Udipsamments) on the third lower level with the youngest soil age (≤ 3.5 ka). The morphological characteristics showed that strongly developed angular blocky structures, pressure faces and slickensides are more common in higher terrace soils than in lower terrace soils. In this study, depth to C horizon, solum thickness, and thickness of the clay-enriched zone increase with relative terrace age. Although only one to two profiles per terrace were characterized, the following soil analytical characterizations increase with time: the degree of sand grains weathering, pH (H 2O), organic carbon, CEC, contents of Fe d, Fe o and Mn d. Based on X-ray diffraction analysis of the clay-size fraction, soils on all terraces have a mixed mineralogy. Mica, smectite, and kaolinite have slightly increased with increasing terrace age. Furthermore, the dominant processes identified with mass-balance analysis include loss of bases (Ca and Mg), iron, and clay with time. The soil properties, including analytical and mineralogical characterizations, which do not have notable changes with time are primarily due to relatively young soil age (< 10 ka).

Soil predatory mite communities (Acari: Gamasina) in agroecosystems of Central Argentina

The objective of this study was to compare soil predatory mite communities over a gradient of land use intensity in agroecosystems of Central Argentina. The study was conducted at La Colacha basin, Córdoba, Argentina on coarse-loamy, illitic, thermic Typic Hapludoll. Four sites with different management systems (natural grassland, cattle raising, arable and mixed), but with the same Soil Series, similar geomorphological characteristics and the same land use history until 50 years before, were sampled at four sampling dates. Thirty-eight species, 19 genera and nine families were identified. Ninety-two percent of the identified species are new to science. This shows that the taxonomic knowledge of Gamasina is poorly developed in Argentina. In this study, Gamasina community structure was clearly influenced by the management type. This confirms our hypothesis that Gamasina community structure significantly changes as material and energy inputs and mechanical perturbations in the system increased from the natural soil to the conventional agricultural sites. The effects of agricultural practices could be observed in the occurrence of the species, the diversity and the dominance structure of the community, the maturity index, and also in seven similarity measures and the multivariate canonical correspondence analysis (CCA). Species number and diversity measures were highest in the cattle raising plot and very low in the natural and arable site. So, in terms of species number, the arable field did not have an impoverished community in comparison with the natural undisturbed grassland.

Subsurface Lateral Transport in Glacial Till Soils

An understanding of water and solute flow patterns in a landscape is necessary to describe water and nutrient use by crops, as well as potential nutrient contamination of groundwater, tile water, and streams. Subsurface water and solute movement in a landscape can occur laterally as well as vertically in the soil, especially in gently rolling landscapes with shallow water tables. The objective of this study was to identify contributing factors for solute transport in corn (Zea mays L.) - soybean (Glycine max (L.) Merr.) fields on a Clarion soil (fine-loamy, mixed, superactive, mesic Typic Hapludoll) with a 5% slope. Bromide, as a tracer, was applied in a trench 0.18 m deep on 20 May 1993, and to a second site 5 May 1996 in a V-shaped transect. Following 959 mm of precipitation (79% above average for the first site), Br- was transported laterally in the subsurface to 6 m downslope between application and the last sampling date of 27 October 1993. Small amounts were detected near the surface even at 15 m downslope. Over 50% moved vertically beneath the applied transect but only to 0.9 m depth. Most of the laterally transported Br- ended up in the unsaturated zone. For the second site, the bromide only moved 3 m downslope because rainfall was more normal (13% above average) and more Br- was located near the surface. Results from this study on glacial till soils indicate that mobile solutes would be expected to move laterally beyond the application zone.

Tillage Effects on Hydraulic Properties and Macroporosity in Silty and Sandy Soils

In agricultural soils, macroporosity and hydraulic properties are influenced by tillage practices. The objective of this study was to characterize macroporosity and surface soil hydraulic properties in two soils of different texture (Lietzen: sandy loam–Humic Dystrudept; Adenstedt: silt loam; Typic Hapludoll) under conventional (CT) and conservational (RT) tillage systems. Soil hydraulic conductivity was assessed in situ by ponded infiltration with single rings (n = 70) and tension infiltration by means of a “closed‐top” hood infiltrometer (HIF; n = 48). Macroporosity (pore diameters &gt;1 mm) was estimated from differences in infiltration at saturation and at −3 cm H2O soil matric potential. Mean saturated hydraulic conductivity (Ks) for Lietzen was 3.1 × 10−5 m s−1 and for Adenstedt was 4.3 × 10−5 m s−1 These values are by one order of magnitude higher than values estimated from soil texture. This implies that soil structure has a dominant influence on hydraulic conductivity. Mean values of macroporosity were 0.005% for Lietzen and 0.018% for Adenstedt (using the method of Watson and Luxmoore). The respective values were 0.0008 and 0.0013% when the method of Bodhinayake et al. was used. For Adenstedt, RT showed higher macroporosity than CT (not significant at P &lt; 0.05 for n = 12). Such treatment‐induced differences were less developed for Lietzen. The Ks values measured with the ponded ring infiltrometer (RIF) at the sandy Lietzen site were higher than the corresponding values measured with the tension infiltrometer. These differences may be caused by subcritical soil water repellency (i.e., contact angles of the soil‐water‐air interface below 90°), although further factors could also be important (e.g., air entrapment, differences in water saturation, geometry of infiltration devices).

Effects of Sewage-Sludge Application on Soils and Sunflower Yield: Quality and Toxic Element Accumulation

ABSTRACT Sunflower nutrition, sewage-sludge nutrients, and trace-metals supply have been studied in detail, but separately. The objective of the present work was to study the effects of sewage sludge on sunflower yields and the accumulation of nutrients and trace metals in soils and in the crop. Three experiments with sunflower were therefore conducted on farms located in Buenos Aires Province, Argentina. The treatments were control, 7 t dry matter (DM) sewage sludge/ha, and 14 t DM sewage sludge/ha. Soils were Typic Argiudolls and a Typic Hapludoll. At physiological maturity, grains and aerial biomass were harvested. Nitrogen (N), phosphorus (P), and potassium (K) were determined and, after digestion with acids, cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), nickel (Ni), and zinc (Zn) were analyzed with inductively coupled argon plasma emission spectrometry (ICPES). Soil samples were taken and analyzed for nutrients and Cd, Cr, Cu, Ni, Pb, and Zn. Only available P and nitrate-N increased in the soil after the application of sewage sludge. Sunflower yields increased by increasing grains per head. Individual grain weight, oil content, nutrients, and trace-metals concentrations were not affected, nor were the aerial biomass and its composition. Using sewage sludge according to standard regulations does not affect either toxic-metals uptake or sunflower quality.

Tillage and Nitrogen Source and Rate Effects on Corn Response in Corn–Soybean Rotation

Conservation tillage systems present a challenge for integrating an efficient fertilizer program for corn (Zea mays L.) production in the U.S. Midwest and elsewhere. The objective of this study was to evaluate corn response to three tillage systems (no‐tillage, strip‐tillage, and chisel plow) and four N rates (0, 85, 170, and 250 kg N ha−1) of liquid swine manure and commercial fertilizer in a corn–soybean [Glycine max (L.) Merr.] rotation. A 3‐yr study from 2002 to 2004 was conducted on a Kenyon soil (fine‐loamy, mixed, mesic Typic Hapludoll) at the Iowa State University Northeast Research and Demonstration Farm near Nashua, IA. The experimental design was a randomized complete block with split plots. Tillage and N rates were randomly assigned as main plot and subplot treatments, respectively. Corn grain yield and aboveground biomass response to different tillage systems were not significantly different for all N rates of both N sources; however, the biomass yield at different growth stages with different N sources, tillage, and N rates were inconsistent. There were no interaction effects of tillage and N rates on yields, except in a few cases. The 3‐yr average of maximum (MNR) and economic optimal (EONR) N rates (182 and 174 kg N ha−1, respectively) across all tillage systems with liquid manure produced identical maximum (MGY) and economic optimum (EOGY) grain yields of 11.7 Mg ha−1. In contrast, the MNR and EONR (176 and 144 kg N ha−1, respectively) with commercial fertilizer N produced a MGY and an EOGY of 11.2 and 11.1 Mg ha−1, respectively.

Soil springtails (Hexapoda: Collembola), symphylans and pauropods (Arthropoda: Myriapoda) under different management systems in agroecosystems of the subhumid Pampa (Argentina)

The Pampa region is the most important agricultural area in Argentina. Although intensive agricultural activity is leading to important levels of soil degradation, studies on the impact on soil fauna are scarce. Despite the environmental importance of collembolans, symphylans and pauropods in soil, information on the influence of land management on their population densities is poor, particularly in Neotropical agroecosystems. The aim of this study was to investigate the effects of different management systems on the density of collembolans, symphylans and pauropods. Population abundance of these arthropods was examined in a natural site and a cattle raising, a mixed and an agricultural management system on a Typic Hapludoll soil in La Colacha, Córdoba, Argentina. All the sites studied had the same land use history until approximately 50 years before sampling and have the same soil type. Total abundance of the studied groups varied in the different management systems. Our results suggest that conventional agricultural management tends to reduce the density of collembolans and pauropods. Our data do not support our hypothesis that the cattle raising management system constitutes an intermediate situation between the natural site and the high-input management systems. We conclude that the reduction of collembolan and pauropod densities in high-input management systems is largely explained by the mechanical and chemical perturbations produced by conventional agricultural management practices and by particular abiotic soil conditions present in the intensively managed sites that are unfavourable for these organisms. Surprisingly, symphylans were more abundant in the mixed management site. The implications of our findings on soil ecosystem functioning are discussed.