US Soil Taxonomy Research Articles

Residue management and tillage effects on soil-water storage and grain yield of dryland wheat and sorghum for a clay loam in Texas

Dryland wheat ( Triticum aestivum L.) and grain sorghum ( Sorghum bicolor (L.) Moench) are often grown using a wheat–sorghum-fallow (WSF) crop rotation on the semiarid North American Great Plains. Precipitation stored during fallow as soil water is crucial to the success of the WSF rotation. Stubble mulch-tillage (SM) and no-tillage (NT) residue management practices reduce evaporation, but the sparse residue cover produced by dryland crops, particularly sorghum, is insufficient to reduce soil crusting and runoff. Subsoil tillage practices, e.g., paratill (PT) or sweep (ST), fracture infiltration limiting soil layers and, when used with residue management practices, may increase soil-water storage and crop growth. Our objectives were to compare the effects of PT to 0.35 m or ST to 0.10 m treatments on soil cone penetration resistance, soil-water storage, and dryland crop yield with NT and SM residue management. Six contour-farmed level-terraced watersheds with a Pullman clay loam (US soil taxonomy: fine, mixed, superactive, thermic Torrertic Paleustoll; FAO: Kastanozems) at the USDA—Agricultural Research Service, Conservation and Production Research Laboratory, Bushland, TX, USA (35°11′N, 102°5′W) were cropped as pairs using a WSF rotation so that each phase of the sequence appeared each year. In 1988, residue management plots received PT or ST every 3 years during fallow after sorghum resulting in five treatments: (i) NT–PT, (ii) NT–NOPT, (iii) NT–ST, (iv) SM–PT, and (v) SM–NOPT. Cone penetration resistance was the greatest in NT plots and reduced with PT after 12, 23, and 31 months. Mean 1990–1995 soil-water storage during fallow after wheat was greater with NT than with SM, but unaffected by PT or ST. Dryland wheat and sorghum grain yields, total water use, and water use efficiency (WUE) were not consistently increased with NT, however, and unaffected by PT or ST tillage. We conclude, for a dryland WSF rotation, that: (1) NT increased mean soil-water storage during fallow after wheat compared to SM, and (2) ST and PT “subsoil” tillage of a Pullman did not increase water storage or yield. Therefore, NT residue management was more beneficial for dryland crop production than subsoil tillage.

Economic risk, returns and input use under ridge and conventional tillage in the northern Corn Belt, USA

Ridge tillage (RT) has been proposed as an economically viable conservation tillage alternative for row crop production; however the long-term economic viability of RT in the northern Corn Belt of the USA is largely unknown. Economic returns, risk and input use were compared for RT and conventional tillage (CT) in a corn ( Zea mays L.) and soybean ( Glycine max (L.) Merr.) rotation with high, medium and low nitrogen treatments. The analysis was based on 10 years of experimental data from Brookings, SD on a Barnes clay loam (US soil taxonomy: fine-loamy, mixed, superactive, frigid Calcic Hapludoll; FAO classification: Chernozem). Economic returns were significantly higher at the highest nitrogen treatment levels. Highest average net returns to land and management were $ 78 per hectare for RT at the high nitrogen treatment level (RT-H) followed by $ 59 per hectare for CT at the high nitrogen treatment level (CT-H). Risk, measured as the standard deviation of net returns, was the lowest for CT at the medium nitrogen treatment level (CT-M) followed by RT-H and CT-H. However, net returns were substantially lower under CT-M at $ 32 per hectare. Average yields and average operating costs were not significantly different for RT-H and CT-H. Reduced equipment operating costs for CT-H were offset by increased herbicide costs for RT-H. Equipment ownership costs were significantly lower for RT-H than CT-H. There were no significant differences in fertilizer use for RT and CT. Pesticide use was significantly higher for RT-H than CT-H. Fuel use was 18–22% lower and labor use was 24–27% lower for RT-H than CT-H. Despite continued low adoption rates for RT in the northern Corn Belt, our analysis shows that RT is an economically viable alternative to CT.

Residue management and paratillage effects on some soil properties and rain infiltration

Dryland winter wheat ( Triticum aestivum L.) and grain sorghum [ Sorghum bicolor (L.) Moench] are often grown on the semiarid North American Great Plains using the wheat–sorghum–fallow (WSF) crop rotation. When used with WSF, no-tillage (NT) and stubblemulch tillage (SM) residue management reduce evaporation and increase yield, but more runoff occurs with NT compared to SM. Our objectives were to determine the effects of NT and SM residue management with paratill (PT) and sweep (ST) tillage on soil properties and rain infiltration into a Pullman clay loam (US soil taxonomy: fine, mixed, superactive, thermic Torrertic Paleustoll). Six contour-farmed level-terraced watersheds were dryland cropped using a WSF rotation with each phase of the WSF appearing all years as main plots. Residue management by tillage subplots of: (i) NT with PT, (ii) NT with NOPT, (iii) NT with ST, (iv) SM with PT, and (v) SM with NOPT were installed within these main plots after sorghum harvest. Approximately, 9 months later during the wheat phase (before planting), we measured selected soil characteristics and the infiltration rate and amount using a rotating disk rain simulator that applied cistern stored rainwater at 48 mm h −1 on the five tillage—residue management treatments. Cumulative infiltration at 1 h was similar among tillage treatments within residue management practices, i.e., infiltration into SM plots averaged 32.4±3.9 mm compared to 21.9±2.5 mm for NT plots. Regardless of residue management, PT and ST tillage caused no significant ( P<0.05) increase in infiltration compared to NOPT. Measured cone-penetrometer resistance, bulk density, and initial soil-water content decreased with ST and PT for NT residue management but not SM residue management. The data show that SM residue management compacted the soil beneath, the sweep implements; thus, negating any benefits of reduced soil bulk density and penetration resistance with PT. We conclude that reductions in soil density and penetration resistance due to PT were diminished by SM tillage and that infiltration was regulated at the soil surface by a rapidly forming crust, which negated PT effects on SM or NT.

Crop yield and soil condition under ridge and chisel-plow tillage in the northern Corn Belt, USA

Ridge tillage is a special conservation tillage method, but the long-term effect of this tillage system on crop yield and soil quality in a corn ( Zea mays L.) and soybean [ Glycine max (L.) Merr.] rotation is largely unknown in the northern Corn Belt of the USA. Our objectives were to compare crop performance and soil condition at three nitrogen-fertilizer levels under ridge tillage (RT) and conventional tillage (CT). The experiment was started in 1990 at Brookings, SD, on a Barnes clay loam (US soil taxonomy: fine-loamy, mixed Udic Haploboroll; FAO classification: Chernozem). CT included moldboard or chisel plowing, seedbed preparation with tandem disk and field cultivator, and row cultivation. Raised beds under RT were maintained using only row cultivation. Corn grain yield was significantly ( p≤0.10) greater on CT than on RT. Average (11 years and three fertilizer-N rates) corn yield was 6267 kg ha −1 with RT and 6500 kg ha −1 with CT. Soybean grain yield was not significantly ( p≤0.10) different between RT and CT. Average (11 years and three fertilizer-N rates) soybean yield was 1997 kg ha −1 with RT and 2058 kg ha −1 with CT. In 9 of 11 years there was a significant soybean-yield response to N-starter fertilizer. There was no significant accumulation of NO 3-N in the top 3 m of soil at the end of 9 years in either tillage treatment (111 kg NO 3-N ha −1 under RT and 121 kg NO 3-N ha −1 under CT). Soil pH in the top 15 cm was unaffected by tillage (average pH was 6.62). In 1999, soil organic C in the top 0.2 m was significantly greater under CT (56 Mg ha −1) than under RT (52 Mg ha −1). Bulk density in the top 0.2 m was significantly greater under RT (1.52 g cm −3) than under CT (1.44 g cm −3). Tillage did not have a great effect on grain yield or soil properties. RT can protect soil from erosion because crop residues remain relatively undisturbed on the soil surface in contrast to chisel plow. In this respect, we expect RT to be more sustainable over the long term than chisel plow tillage.

The application of the FAO and US soil taxonomy systems to saline soils in relation to halophytic vegetation in SE Spain

Twenty-three pedons from six salt marshes in SE Spain, occurring under a semiarid Mediterranean climate, were classified according to various FAO and USDA Soil Survey Staff (SSS) systems. In each salt marsh, the sampling sites were selected to represent seven different plant communities. For the plant communities studied, less diversity of soil classes was observed at the Unit level using the 1998 version of the FAO soil classification system than the 1994 edition and less at the Great Group level for the 1996, 1998 and 1999 versions of the USDA system than the 1992 version. The FAO 1988 version defines the characteristics of these soils better than the 1994 edition because the former includes the possibilities of classifying at the third level and of using salic and sodic phases. The 1998 version offers greater possibilities for expressing the characteristics of these soils, but two considerations would improve the results: (i) the use of the term Hyposalic instead of Endosalic in the Calcisols group; (ii) the possibility of using the petrocalcic horizon in the Solonchak group. The main shortcomings of the 1996 and 1998 versions of the USDA system for classifying these soils are: (i) the lack of a class to indicate a high concentration of salts in the Mollisol Order independently of the presence of a natric horizon and/or aquic conditions; (ii) failure to indicate the existence of a petrocalcic horizon at the Salids Great Group level. These two problems can be overcome in the 1999 version by the use of the adjectives Halic and Petrocalcic, respectively.

VARIATION IN TREE COMMUNITY COMPOSITION AND STRUCTURE WITH CHANGES IN SOIL PROPERTIES WITHIN A FRAGMENT OF SEMIDECIDUOUS FOREST IN SOUTH-EASTERN BRAZIL

The purpose of the present study was to investigate whether variations in tree community structure and soil properties were interrelated in a fragment of semideciduous forest in Martinho Campos, south-eastern Brazil. The forest was sampled by ten plots, each of which was made up of four contiguous 15×15m quadrats (total 0.9ha). Plots were randomly distributed in the fragment with the help of grid-line coordinates. Soil samples were collected from each quadrat for chemical and textural analyses, and the soil of each quadrat was classified in conformity with the US Soil Taxonomy System. All trees with diameter at the base of the stem ≥5cm were identified and measured (circumference and height). Three soil groups were recognized: Ustifluvent, Ustropept, and Dystropept. A principal component analysis independently discriminated the soil groups in terms of their chemical and textural properties, indicating the consistency of the soil classification. Significant differences among the soil groups were also found for most soil properties. Tree community physiognomy was significantly different in Ustropept soil habitat, where trees showed more pronounced slenderness. A detrended correspondence analysis indicated that tree community structure also responded to the three soil habitats. A canonical correspondence analysis, together with Spearman's rank correlations, demonstrated that species' abundance distributions were significantly correlated with the soil properties. Differences in soil nutrient content (particularly Ca2+ and K+) and in ground water regime are apparently the leading factors determining tree species distributions within the fragment.

Soil formation in coastal continental Antarctica (Wilkes Land)

Recent antarctic soil studies suggest that in terrestrial ecosystems of coastal regions soil formation and chemical weathering occur to a greater extent than predicted by former models. This paper summarizes pedogenic findings from the Casey area on the coast of East Antarctica and presents a proposal of soil formation sequences on a large-scale data base. Soil organic matter accumulation and podzolization are important soil forming processes in regions outside the antarctic cold desert of the Ross Sea section. The results suggest some correlations between the soil development and vegetation patterns. Nutrient supply in soil is affected by the high contents and availability of nitrogen, phosphorus, potassium and magnesium due to an input by seabirds. The US Soil Taxonomy (8th edn.: Gelisol order) and the recently adopted World Reference Base for Soil Resources (WRB: Cryosol soil group) suggest a different understanding of impact of permafrost on soil formation. According to the WRB and the US Soil Taxonomy, organic permafrost-affected soils are not Cryosols, but Gelisols. Lithic Haplorthels as well as Haploturbels and to some extent Aquaturbels and organic Gelisols are suggested to be representative of the Casey area. In addition Podzols occur to a great extent. However, the recent Keys to Soil Taxonomy do not reflect the podzolization process in an adequate way and a classification is not possible. According to a former version these soils would be Lithic or Pergelic Haplocryods, whereas according to the newly adopted WRB system these soils are Spodic Haplic Cryosols.

Minimum threshold value of smectite for vertic properties

From a significant positive correlation between linear extensibility (LE) and the smectite content in the soil control section (SCS) of 8 soils (2 red soils, Alfisols, and 6 black soils, Vertisols, and their intergrades), the present study indicates an excellent compatibility between the marked shrink–swell characteristics and the smectitic mineralogy. The initiation of vertic properties at LE of 6 in shrink–swell soils corresponded to a minimum threshold value of 20% smectite. In order to highlight the inherent relationship between vertic properties and the swelling minerals, the mineralogy class for shrink–swell soils in US Soil Taxonomy should be only smectitic.

Genesis, properties and sensitivity of Antarctic Gelisols

According to the newest version of the US Soil Taxonomy permafrost-affected soils are Gelisols. Antarctic Gelisols in the cold deserts of the Ross Sea sector are formed under extreme conditions of low temperature and aridity. The main soil forming processes are oxidation and salinization, with almost complete absence of organic matter. The oldest soils date from around 13 Ma. The origin of most soil salts is atmospheric, linking these soils to those in other parts of the world through atmospheric processes. The soils have water contents in the active layer of the most arid areas &lt;1%. With decreasing latitude or proximity to the coast in East Antarctica and the Antarctic Peninsula, soil water contents increase and the soils support a range of soil organisms and plant species. At latitudes ≤66°S organic matter accumulation and several other pedogenic processes such as cryoturbation, mineral weathering, brunification, acidification, podzolization and redoximorphism occur. In addition, these soils receive nitrogen and phosphorus from seabirds. In most places summer thaw lasts little more than six weeks; thaw depths range from around 10–100 cm. A critical factor in the soil development is the albedo of the soil surface, since the absorbed energy controls weathering processes. The extreme fragility of the soils in the arid Ross Sea sector is largely due to the absence of structure, cohesion, moisture and organic materials. Recovery from physical human disturbances is in the order of hundreds to thousands of years. In East Antarctica and the Antarctic Peninsula plant and organisms growth is similarly slow and ecosystems are susceptible to human impact. The occurrence of many old soils at high inland elevation indicates that little response to global climatic change would be expected there. For the much younger soils in East Antarctica and the Antarctic Peninsula, when mean annual summer temperatures are higher, responses to global change and change in sea level may be significant.

Wheat response and residual soil properties following subsoiling of a sandy loam in eastern Montana

Shallow tillage pans resulting from the use of the same tillage tools may lead to wheat ( Triticum aestivum L.) yield reductions. We hypothesized that occasional deep tillage to fracture shallow tillage pans would improve water utilization and result in increased wheat yield. Our hypothesis was tested by comparing paired crop and soil responses on plots that were subsoiled using a paratill (PT) or not subsoiled (NOPT). Soil was a Dooley sandy loam (US soil taxonomy: fine-loamy, mixed Typic Argiboroll; FAO taxonomy: Kastanozem) derived in glacial till near Culbertson, Montana, USA. Effects of PT or NOPT were compared in a long-term cropping study that included annual wheat using no tillage (NT), annual wheat using fall and spring tillage (FST) and wheat rotated with fallow (FWCT). Plots that were subsoiled (PT) were paratilled once in autumn 1992 to about 0.3 m deep. Cone index of the top 0.3 m of soil 2.5 years after subsoiling was lower on PT (891 kPa) compared with NOPT (981 kPa). Soil bulk density was 1.34 Mg m −3 on PT and 1.36 Mg m −3 on NOPT plots. Final water infiltration rate averaged 15 mm h −1 on PT and 6 mm h −1 on NOPT plots for nine months after subsoiling. Average water content of the top 1.2 m of soil in the spring of the year was 21 mm greater on PT than on NOPT plots. There were no differences due to treatments in wheat yield; average grain yield was 1820 kg ha −1 on annual wheat plots and 2380 kg ha −1 on wheat/fallow plots. Residual effects of subsoiling on soil properties were detected for 2.5 years after subsoiling, but soil changes attributed to subsoiling had no effect on wheat yield.

CHARACTERIZATION OF ANDISOLS DEVELOPED FROM NONVOLCANIC MATERIAL IN EASTERN NEPAL

Soils developed from mica schist in Eastern Nepal (The Himalayas) were investigated. All soil horizons were characterized by high organic carbon and extractable aluminum contents. Chemical and physical analyses indicated andic soil properties. No short-range order minerals could be detected. It is assumed that aluminum is linked to the organic matter, which leads to insolubilization and stabilization of the organic material against microbial degradation. The formation of Al-humus complexes instead of short-range order minerals is preferred if enough Al and water-soluble organic compounds are present. Al-humus complexes are considered responsible for the formation of Andisols from nonvolcanic parent material. The soil is classified as Dystric Haplustand, medial, mesic (US Soil Taxonomy)

Soil Taxonomy: An Overview

The growth of crops depends on many factors, not least the nature of the soil. It is, therefore, important to be able to describe soils in unequivocal terms, much as living organisms are precisely defined according to the binomial taxonomic system originated by Linnaeus. The very complex and varied nature of soils makes this a difficult problem but since the 1950s it has been vigorously tackled by the US Soil Taxonomy programme. The hierarchical system developed is reviewed here.

Grouping soils with similar properties for areal water budgeting and moisture mapping

Infiltration, field capacity and wilting point are the most important parameters used in water budgeting. Even for a small watershed of uniform weather characteristics, water budgeting must be performed for sub-areas of distinct soil properties. As the number of these sub-areas increases, the number of calculations involved in water budgeting also becomes large. For a large area including many different weather zones, the total number of water budget calculations, proportional to the product of weather zones and the number of sub-areas of uniform soil properties, can reach a magnitude which easily exceeds the capability of the most powerful computer available. Therefore, it is important to group soils with similar water movement and storage properties (the same can also be said about weather) to reduce water budgeting calculations. The magnitide of dispersion of soil properties in each sub-area needs to be estimated. The US Soil Taxonomy, a general soil classification scheme, was found to be useful to this grouping. The soil grouping technique based on the Soil Taxonomy was used in producing soil hydraulic properties maps for the Island of Oahu, Hawaii.

A nutrient requirement mapping system for new crop introduction

A procedure for mapping nutrient requirement for introduction of a new crop to an area has been developed. The procedure makes use of the US Soil Taxonomy for grouping soils into homogeneous fertility areas. Subsoil chemical properties are used for nutrient estimation. The Hawaii Natural Resource Information System was adapted to produce sample phosphorus requirement maps for the island of Oahu.

Morphological and physico-chemical aspects of three soils developed in peat in the Netherlands and their classification.

In an oligotrophic soil formed in Sphagnum peat, an oligotrophic soil formed in Sphagnum-Eriophorum peat and a mesotrophic soil formed in Carex peat, the first and second soils contain a variable but rather large amount of histons, but the histon content of the third soil is low. Fungons are characteristic of the first soil, occur in small amounts in the second soil and are practically absent from the third soil. Decomposition by the soil fauna (as evidenced by faecal pellets) is slight in the first soil and is effected mainly by Oribatid mites, but in the second soil decomposition by Oribatids is considerable, by earthworms moderate, and by Enchytraeids sporadic. In the third soil, which contains some mineral material, the considerable decomposition by the soil fauna is effected by dipterous larvae and earthworms and to a lesser extent by Oribatids. In all the soils the rubbed fibre content and physico-chemical data agree with the change in the nature of the soil material with depth. In the first soil hemic material changes into fibric material, in the second soil the practically sapric soil material in the top 7 cm changes into hemic and fibric material, and in the third soil sapric material occurs down to 51 cm and then changes into hemic material. The classification of the three soils by the US Soil Taxonomy system, the Dutch system and the FAO-UNESCO system is discussed. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Relationships Among Physical and Chemical Properties of Representative Soils of the Tropics from Puerto Rico

AbstractIn an investigation of the extent to which predictive soil property relationships can be relied upon in characterizing soils of the tropics classified at the reconnaissance level, 9 to 15 soil properties, of 370 horizons, from 84 Puerto Rican profiles, were studied by correlation and multiple linear regression. The soils represented six orders of the new US Soil Taxonomy (7th Approximation): Vertisols, Mollisols, Alfisols, Inceptisols, Ultisols, and Oxisols. Multiple regression equations were formed from the data of each order, with 15‐bar moisture content, CEC, organic carbon, extractable iron, and base saturation as dependent variables. The results indicate that, although it is possible to eliminate certain properties from tropical soil data acquisition and still adequately characterize the soil, the specific properties that can be successfully eliminated depend on the soil order.