Typic Ustorthents Research Articles

Micronutrient deficiencies in rainfed calcareous soils of Pakistan. IV. Zinc nutrition of sorghum

Zinc (Zn) deficiency in crops is a major micronutrient disorder particularly in alkaline‐calcareous soils like those of the rainfed Potohar plateau in Pakistan. A nutrient indexing of sorghum (cv. Potohar 4–8) by sampling <30 cm tall whole shoots and associated soils from 255 random field locations revealed that the crop was deficient in Zn in 54% fields in Jehlum district and 64% in Chakwal. In a greenhouse experiment using a Zn‐deficient calcareous Typic Ustorthents, maximum increase in grain yield with Zn fertilizer was 177% over control in improved sorghum variety (cv. PARC‐SS‐1) and only 10% in local sorghum (cv. Potohar 4–8). Although biomass production of cv. PARC‐SS‐1 was much greater compared with cv. Potohar 4–8, fertilizer Zn requirement for the two cultivars was not much different, 8.3 mg Zn/kg soil for improved sorghum variety and 7.3 mg Zn/kg for local sorghum variety. Contrary to its higher sensitivity to Zn deficiency, the improved sorghum variety was more efficient in utilizing fertilizer Zn. Despite low Zn availability in the Potohar fields, local sorghum is not expected to respond to fertilizer Zn. However, adequate Zn fertility must be assured for cultivating improved sorghum in these soils. Zinc content in mature grains of sorghum proved a good index of soil Zn fertility status. Internal Zn requirement in foliar plant parts of cv. PARC‐SS‐1 (whole shoots, 33 mg/kg; leaves, 22 mg/kg) was greater than in cv. Potohar 4–8 (whole shoots, 27 mg/kg; leaves, 20 mg/kg). In contrast, critical Zn content in grains of the improved sorghum variety (10 mg/kg) was lower than of local variety (14 mg/kg). Three soil tests were equally effective in determining soil Zn fertility. Critical soil Zn levels for cv. PARC‐SS‐1 were: DTPA, 3.4 mg/kg; AB‐DTPA, 3.7 mg/kg; and Mehlich 3, 8.0 mg/dm3. Similar to internal Zn requirement in foliar plant parts, soil test critical Zn levels were lower for cv. Potohar 4–8, i.e., DTPA, 3.1 mg/kg; AB‐DTPA, 3.5 mg/kg; and Mehlich 3, 7.2 mg/dm3. Because of their better efficiency, ‘universal’ soil tests appear superior to the DTPA test for routine Zn analysis.

WATER RETENTION CHARACTERISTICS OF SOME IMPORTANT SOIL GROUPS OF KAMARAJAR DISTRICT, TAMIL NADU

Water retention characteristics of soils representing soil subgroups Typic Chromusterts, Typic Ustropept, Udic Haplustalf, Typic Haplustalf, Vertic Haplustalf and Typic Ustorthent in Kamarajar district of Tamil Nadu were evaluated and the influence of clay, total porosity. exchangeable sodium percentage, CEC, organic carbon, electrical conductivity and aggregate stability were studied. The results indicated that clay content in the soil is the major contributing factor to variations in water retention characteristics, to the extent of 83 to 91 per cent.

Soil‐landscape relationships in Siwalik Hills of the semiarid tract of Punjab, India

Remotely sensed satellite data of IRS‐lB‐LISS‐1 have been analyzed to delineate five different geomorphic surfaces in the Siwalik hills in a semiarid tract of the Punjab state in northwest India. Soils from unstable geomorphic surfaces (shoulder, toeslope, and rivulet) showed A‐C profiles, while soils developed on relatively stable geomorphic surfaces (backslope and footslope) had a well‐developed cambic horizon and showed A‐Bw‐C profile development. Topography, along with the nature of parent material and time, was found to be responsible for the pedogenic differences in the soils developed on different landscapes. The eroded soils from shoulder and toeslope were classified as Typic Ustorthents, and the coarse‐textured soils from rivulet as Typic Ustipsamments. The moderately developed soils from backslope and footslope were classified as Typic Ustochrepts. This study established a well‐defined relationship between geomorphic surfaces and development of soils. Concatenation of soils on these geomorphic surfaces was the result of surface and subsurface movement of materials.

ZINC AND MOLYBDENUM ON YIELD AND NUTRITION OF SOYBEAN

Soybean Co.l. raised on Perianaickanpalayam (Typic ustivertept) and Irugur (Typic ustorthent) soil scries at Tamil Nadu Agricultural University Farm, Coimbatore during rabi 1990-91 and kharif 1991-92 respectively responded significantly to Zn fertilizetion at 5.0 kg ha. Combined application of Zn, Mo and FYM at 2.5 kg, 0.5 kg and 10 t ha respectively produced the highest seed yield in both the years besides increasing their content and uptake by soybean seed. The highest Fe uptake by seed during rabi 1990-91 was evidenced with the application of 5.0 kg Zn ha".

Formation of soils with plinthite on a toposequence in Maranha˜o State, Brazil

Soils with plinthite and ironstone concretions are extensive in Maranha˜o State, northeastern Brazil. They formed from the Fe-rich Itapecuru sandstone in a tropical subhumid climate with distinct wet and dry seasons. Most plinthic soils in Brazil have properties associated with low-activity clays, but these soils were reported to have properties associated with high-activity clays. The main objectives of this study were to characterize the chemical and mineralogical properties of the soils and to deduce the processes of their formation in relation to hillslope position. six soils were sampled, two each on summit, shoulder, and footslope positions. They were analyzed by standard characterization methods and by X-ray diffraction and infrared spectroscopy. The parent sandstone bedrock contained mainly quartz, feldspars, muscovite, biotite, and resistant minerals in the sand fraction, and smectite, mica and kaolinite in the clay fraction. The main Fe-oxide mineral was hematite. Most soil horizons had lower Fe concentrations than the sandstone parent material. Kaolinite, mica and quartz occurred in the coarse clay fraction of all pedons. Soils on the summit positions (Ustic Dystropept and Typic Ustorthent) lacked redoximorphic features, lacked plinthite, had the highest cation exchange capacity, and showed the weakest development. They were rich in smectite, probably inherited from the parent material, and goethite. soils on shoulder positions (Inceptic Plinthustult and Plinthic Dystropept) had the largest concentration of total Fe, mostly as goethite. Those on footslopes (Typic Plinthaquult and Plinthic Paleaquult) exhibited the most redoximorphic features and had horizons in which the Fe was strongly concentrated in ironstone and plinthite, mostly as lepidocrocite and goethite. The crystallinity of these minerals increased from non-plinthic material to plinthite to ironstone concretions. They formed as the hematite in the sandstone weathered. These soils are less weathered than most plinthic soils of Brazil. Diagnostic criteria for some subgroups of the Plinthustult and Dystropept great groups of soil Taxonomy and some new classes for the Brazilian soil Classification system were proposed.

DIRECT, RESIDUAL AND CUMULATIVE EFFECT OF APPLIED ZINC FOR RICE IN RED SOILS

Field experiments were conducted on red soils (Typic Ustorthent) at the Tamil Nadu Agricultural University Farm of Agricultural Research Station, Bhavanisagar to study direct, residual and cumulative effect of applied Zn to IR 20 rice. The continuous application of ZnSO4 at 25 kg per ha for every season of rice crop significantly increased grain and straw yield and resulted in 17 per cent increase in grain yield over NPK treated control. Application of ZnSO4 at 50 kg for first crop resulted in residual effect of Zn with increase in the grain yield of two subsequent crops. Similar trend was also observed for the level of 75 kg ZnSO4/ha. Residual effect of ZnSO4 application at 100 kg/ha to first crop was observed for five subsequent rice crops.

INVESTIGATION ON SOME PHYSICAL PROPERTIES OF ALFISOL AND ENTISOLS OF KAMARAJAR DISTRICT

Three major soil subgroups namely, Udic Haplustalf, Typic Haplustalf and Typic Ustorthent to represent the Alfisols and Entisols of Kamarajar district of Tamil Nadu were taken up to evaluate the interrelationships of certain physical properties. The results revealed that clay content negatively influenced saturated hydraulic conductivity, bulk density, effective porosity and aggregate stability. It revealed also the active role played by organic matter in controlling the bulk density. Increasing sand fractions in the soils increased noncapillary pores resulting in higher Ks. Bulk density of soils was found to be independent of clay content in decreasing Ks. Total porosity did not show any relationship with Ks, but noncapillary porosity and effective porosity were positively correlated with Ks.

Pedogenesis in relation to physiography in semiarid and arid tracts of Punjab, India

Abstract Morphological, physical, and chemical characteristics of soils developed in different physiographic units in the Punjab state (northwest India) revealed three distinct stages of pedogenic development: A‐C, A‐(Bw)‐C, and A‐Bt‐C profiles. The young and stratified soils from unstable landforms (sandbars, rivulets, floodplains, and foothills) representing newer alluvium are classified as Typic Ustipsamments or Typic Ustifluvents. The severely eroded and shallow soils of foothills are classified as Typic Ustorthents. The soils developed on relatively stable landforms (alluvial terraces, old channel fill, and interdunal areas) show development of cambic or structural B horizon and are classified as Ustochreptic Camborthids, Typic Ustochrepts, and Aquic Ustochrepts, depending on the prevailing climatic and drainage conditions. Contrary to the above, the soils formed on old alluvial terraces show the development of argillic (Bt) horizons. These soils are classified as Typic Haplustalfs. Genesis of these ...

Reflectances from Four Wheat Residue Cover Densities as Influenced by Three Soil Backgrounds

AbstractIt is important to know quantity of crop residue on the soil surface to maintain or to improve soil physical and chemical properties and to assess the soil's susceptibility to erosion. Our objective was to use remote sensing techniques to examine the potential for remotely differentiating among wheat residue quantities and bare soils. We used three soils of the northern Great Plains (Williams loam [fineloamy, mixed Typic Argiboroll], Vanda Clay [fine‐silty, mixed calcareous, frigid Ustic Torriorthents], and Lambert silt loam [finesilty, mixed calcareous, frigid Typic Ustorthents]) that had either dry or wet surfaces and 0, 33, 66, and 100% wheat residue covering the soil surfaces. A portable spectroradiometer, and a hand‐held four‐band radiometer were used to measure spectral response and an infrared thermometer to measure surface temperatures. The infrared thermometer results allowed for differentiation among wet and dry surfaces and among residue quantities when the soil background was wet. Temperature differences between wet and dry surfaces became smaller as residue quantities increased and were near the same at 100% cover. Data obtained from the two radiometers were similar. Based on the type of measurements made in our study and indices calculated, the conclusions are that remotely sensed temperatures may be useful to assess surface soil residue covers when all soil backgrounds are wet. Linear combinations of n spectral bands in n‐dimensional space were calculated to form spectral indices, referred to as n‐space indices. The first n‐space index probably holds the best promise for developing any type of relationship to determine amount of residue cover on an otherwise bare soil surface, albeit, it appears from the data that the usefulness of such a relationship would be limited to soils that are naturally dark colored or that are darkened by the effect of water.

Soil-Physiography relationship in Mahanadi Delta (Part) using Landsat Imagery

Visual Interpretation of Landsat Imagery (TM-FCC) on 1∶250,000 scale covering 2410 sq km in a part of Mahandi Delta, Kataka district, Orissa was carried out for delineating the physiographic units. The major physiographic units identified and delineated were ‘Delta plain’ and ‘Coastal plain’. These units were further subdivided on the basis of image elements. The abstraction level attained was ‘Family’ based on Soil Taxonomy. The soils of the beach were classified as Typic Ustipsamments; old coastal plain as fine, Typic Haplaquept and coarse loamy Aquic Ustifluvent; Tidal flat as fine Typic Haplaquept and fine loamy Aquic Ustifluvent; mud flat as fine Typic Haplaquept; Levee-plain complex as Typic Ustipsamment and fine loamy Typic Ustorthent; old Delta plain as fine Udic Ustochrept and Aeric Haplaquept and recent delta plain as fine loamy and coarse loamy Typic Ustorthent. The soils are mixed in mineralogy and Isohyperthermic in temperature regime.

Diffusion, Adsorption, and Predicted Longevity of Banded Phosphorus Fertilizer in Three Soils

AbstractDiffusion of banded P fertilizer influences the residual P effect, root/P‐fertilizer contact, fertilizer‐P longevity (the time after which the contribution of applied band to plant P uptake is insignificant) and the probability that the P‐affected soil will be collected during soil sampling. An experiment was conducted to determine the extent of P diffusion from banded P application, diffusion coefficients, and the longevity of banded P fertilizer. Six P rates of 15, 22.5, 30, 37.5, 45, and 60 kg P ha−1 tagged with 32P were applied in a band in three soils and allowed to diffuse under field conditions for 94 d. Phosphorus‐fertilizer movement from the injected band centers (30‐cm spacing) after 94 d ranged from 1.8‐cm radius at the 15 kg P ha−1 rate in the Sharpsburg (fine, montmorillonitic, mesic Typic Argiudoll) and Coly (fine‐silty, mixed [calcareous], mesic Typic Ustorthent) soils to 3.9 cm at the 60 kg P ha−1 rate in the Nora (fine‐silty, mixed, mesic Udic Haplustoll) soil. The diffusion distances and apparent diffusion coefficients increased in a linear manner as the P application rate increased. The calculated longevity of banded P fertilizer ranged from 2.6 yr at 15 kg P ha−1 in the Sharpsburg soil to 6.5 yr at 60 kg P ha−1 in the Coly soil. The longevity of banded P fertilizer was shortest for the Sharpsburg soil with the highest P‐adsorption capacity and was longest for the Coly soil with the lowest P‐adsorption capacity. The probability of P‐affected soil being collected during soil sampling ranged from 11.7% at 11.7% at 15 kg P ha−1 in the Sharpsburg soil to 25.9% at 60 kg P ha−1 in the Nora soil. Soil sampling and soil‐test P calibration should be altered to account for the residual nature of applied P bands.

Crop Yield Interpretation for North Dakota: II. Field Questionnaires—A Delphi Approach

A two-stage Delphi survey was used to evaluate soil productivity indexes currently used for Hard Red Spring (HRS) wheat (Triticum aestivum L.) in North Dakota. Experienced field soil scientists estimated the relative productivity of several soils having a wide range of properties. Mean productivity index for most soils changed little between the first and second questionnaires, but coefficient of variation (CV) decreased an average of 20 and 17% for wheat and sunflower, respectively. Soils with the highest yield variability for both wheat and sunflower were Entic Haploborolls and Typic Ustorthents on upper slopes, Natriborolls, and coarse-textured or loamy soils with sand and gravel substrata. Results were compared to current productivity indexes and effects of slope, paralithic beds, and argillic horizons evaluated. The Delphi technique proved useful for accessing a source of information based on years of field observation. Relative yield estimates from field soil scientists were particularly useful in evaluating the yield potential of soils for which research data were not available. Delphi surveys should be viewed as a subjective method of investigating soil-crop yield relationships and used only to supplement quantitative data.

Phosphorus Fertilizer Carriers and Their Placement for Minimum Till Corn Under Sprinkler Irrigation

AbstractSeveral methods of placement and sources of P were evaluated for sprinkler irrigated corn (Zea mays L.) grown under minimum tillage on a Sharpsburg silty clay loam (Typic Argiudoll) and a Coly silt loam (Typic Ustorthent). Nitrogen and P, dual placed in a localized band (anhydrous ammonia applied with liquid P sources), accomplished greater P uptake and higher corn grain yields on a P deficient calcareous soil than P banded to the side of the seed or banded below the seed, although both methods increased early plant growth compared to either broadcast or P dual placed with NH3. Broadcast preplant applications of P were equally as effective as dual placed P in this study. Explanation of yield and P uptake enhancement by dual placement may lie in the synergistic effect of ammoniacal N and P placed together. The superior performance of the broadcast method of P application was apparently due to root activity near the surface of the soil or in the soil residue interface. In contrast, starter band applications gave higher yields than broadcast or dual placed methods of P application on a slightly acid medium P soil. While it is not known why differences were obtained between the performance of methods of P application on these two soils, low subsoil P levels in the calcareous soil compared to the acid soil was believed to be a contributive factor. Enhanced early P uptake with such row applications may increase yields where high subsurface P levels exist. Urea phosphate (UP) provided greater yields, grain P uptake, and total P uptake than ammonium polyphosphate (APP) and diammonium phosphate (DAP) at the calcareous site—especially when band (side), broadcast, and dual placement methods of P application were used. Total P concentration from plant tissue taken at the eight‐leaf stage was greater for UP than APP and DAP on the slightly acid soil, but no yield differences could be attributed to sources at this site.

INFLUENCE OF N-LEVELS ON THE YIELD AND UPTAKE BY CERTAIN CROPS AND THEIR IMPACT ON N-EFFICIENCY AND RECOVERY

Comparative efficiency of different levels of nitrogen application and their impact on yield, uptake, N-use efficiency and N-recovery were studied with rice-Bhavani (Soil- Typic Haplustall), ragi-Co 11, Groundnut-Pol. 2 (Soil Typic Ustorthent), and Cotton- MCU 5 (Soil Typic Chromustert). Nitrogen fertilizer incorporation exhibited a general increase in the yield and uptake of nitrogen by crops, which was more prominent and significant by the addition of 100 kg N/ha for rice, 45 kg N/ha for ragi, 10 kg N/ha for groundnut and 60 kg N/ha for Cotton. Beyond these levels, the yield increases were not apparent, Added fertilizer N and its positive effect in enhancing the N use offi- ciency/recovery and economy were well manifested at the lower N-levels. The lower efficiency and recovery of fertilizer N at higher N-application rates could be due to higher N-losses associated with larger dressings.

Yield and Quality of a Warm‐Season Grass Mixture Treated with N, P, and Atrazine1

AbstractWarm‐season grasses can be important in pasture systems in the eastern Great Plains. Currently, production from the majority of pastures which contain these grasses is quite low and improvement is needed. In previous research with warm‐season prairie grasses, the effect of fertilization as well as the influence of atrazine [2‐chloro‐4‐(ethylamino)‐6‐(isopropylamino)‐s‐triazine] has been investigatd in separate studies. Only limited research has been conducted to evaluate the combined effects. This study evaluated the rate and frequency of fertilizer N and P with and without use of atrazine on yield and protein content of warm‐season prairie grasses. Three management systems (annual fertilizer with no atrazine, annual fertilizer with atrazine, biennial fertilizer with atrazine) were randomized and replicated in the experimental area. The soil was a Crofton silt loam [fine‐silty, mixed (calcareous) mesic Typic Ustorthent]. Applications of N (0, 34, 67, 101, and 134 kg ha−1) and P (0, 6, 12, 18, and 24 kg ha−1) were applied to the systems involving annual fertilization. These rates were doubled when applied on alternate years (1974, 1976, 1978). Atrazine (1.12 kg ha−1) was applied in early April in 1974, 1976, and 1978. All fertilizer treatments were applied in late May. The response to P was linear in all situations. The response to N was linear where atrazine was not used and curvilinear where atrazine was applied. Atrazine effectively controlled weeds and encroachment of cool‐season species. Compared to the system where no herbicide was used, atrazine applied every 2 years resulted in higher forage production in 4 out of 6 years. Crude protein concentration of the forage increased by about 35 g kg−1with the use of fertilizer N. Neither applied P nor atrazine affected crude protein concentration.

Warm‐season Grass Establishment with Atrazine1

AbstractWeed competition is a limiting factor in warm‐season grass establishment often delaying the first forage harvest 2 or 3 years. Weed control with herbicides could reduce this competition resulting in more rapid grass establishment. Field experiments were conducted to evaluate the effect of atrazine [2‐chloro‐4‐(ethylamino)‐6‐(isopropylamino)‐s‐triazine] on weed control, warm‐season grass establishment, and forage yield during the seeding and following year.Several warm‐season grass species were spring seeded at locations having distinctly different soils. The soils involved were a Butler silty clay loam (Abruptic Argiaquoll) containing 3.8% organic matter and a pH of 5.2, a Crofton silty clay loam (Typic Ustorthent) containing 2.1% organic matter with a pH of 7.2 and a Nora silty clay loam (Udic Haplustoll) containing 2.8% organic matter and pH 5.8. Atrazine at various rates was applied preemergence shortly after grass seeding and at one site it was atso applied the preceding fall. Weed control, grass establishment, and forage yield were measured the year of seeding and the following year.Uncontrolled weeds during the year of seeding reduced stands and 1st year forage yields of big bluestem (Andropogon gerardi Vitman), indiangrass [Sorghastrum nutans (L.) Nash], sand lovegrass [Eragrostis trichodes (Nutt.) Wood], sideoats grama [Bouteloua curtipendula (Michx.) Torr.], and switchgrass (Panicum virgatum L.). Big bluestem and switchgrass tolerated preemergence atrazine applications of 3.4 kg/ha on the Butler soil. Big bluestem was less tolerant of atrazine than switchgrass on the Crofton soil. Some atrazine tolerance was present in indiangrass but not in sand lovegrass and sideoats grama. Seeding year forage yields of big bluestem and switchgrass were significantly increased by atrazine. Weed control during the seeding year sometimes resulted in higher forage yields the following year. Big bluestem and switchgrass can he readily established and produce substantial forage yields the year of seeding by using atrazine for weed control. This would make these grasses more attractive to farmers and ranchers.

Soilscapes, geomorphic processes and soil taxonomic new subgroups identified in the Ghaggar river basin of Haryana and Punjab

Soilscapes of the Ghaggar river basin falling in Haryana and Punjab were interpreted and studied by using the Landsat imagery and aerial photographs. Five major landform units identified and demarcated in the area were : channel courses, levees, flood-plains undulating, basinal floodplains and relict basins. On the basis of sedimentation, nature of the river pattern and soil characteristics, the whole basin was divided into three reaches — upper, middle and lower. Taxonomically the soils were placed under Typic Ustipsamments, Typic Ustorthents and lypic Ustifluvents on channel courses; Aquic Ustifluvents, Typic Ustifluvents and Typic Ustochrepts on levees; Fluventic Ustochrepts, Udic Ustochrepts and lypic Camborthids on floodplains undulating; Typic Ustorthents and Udic Ustochrepts on basinal floodplains; Typic Natrustalfs and Natric Camborthids on relict basins. Two new subgroups were proposed, i.e., Natric within the order of Entisol and Inceptisol, and Aquic-udic within the order of Inceptisol. Two dominant geomorphic processes were observed, i.e., fluvial and aeolian.

Land resource inventory of Naurar subcatchment

Soil and Land Use Survey of Naurar subcatchment in Almora district of Uttar Pradesh was conducted to assist the authorities of the G. B. Pant University of Agriculture and Technology in their “Area Development Project”. Execution of appropriate soil conservation measures and adoption of improved agricultural practices both aimed at the betterment of the socioeconomic conditions of the population of this backward hilly tract are the major objectives of the project. The University Specialists belonging to various disciplines propose to tackle the problem on an integrated basis. A large scale soil and land use map was prepared through the adoption of a systematic Aerial Photo interpretaion procedure. For this purpose 36 large scale Panchromatic vertical aerial photographs in the scale of 1: 15,000 covering a greater part of the subcatchment and three medium scale aerial photographs in the approximate scale of 1: 40,000 were used both for systematic aerial photo-interpretation and compilation of the data during the field work. The survey provides information about the different taxonomie soil classes in the area. It is observed that about 78.7% of the area is covered under Typic Ustorthents. The erosion hazards have also been mapped and revealed 27.3% of the area under moderate to severe erosion and 26.7% under severe to very severe erosion. Broad suggestions for proper utilisation of land resources have also been made.

Soil Crusting and Emergence of Wheat Seedlings1

AbstractSoil crusting is usually referred to be the cause of impaired wheat (Triticum aestivum L.) stands in the Negev region of Israel. The soils in this region vary from mixed hyperthermic, typic Ustipsamment soils to fine loamy, mixed hyperthermic typic Ustorthent soils.The major objective of the work carried out was to estimate and analyze the soil crusting phenomena under field conditions and as a secondary objective to study and analyze wheat seedlings behavior under field and laboratory conditions.Resistance to penetration of natural soil crusts, measured by penetration from underneath the crust, and its dependence on water content and seed bed preparation methods (disking vs. plowing) were determined. These measurements were collected in a field survey carried out during early winter following the first rain that initiated both wheat germination and a sequence of soil slacking and subsequently, as the soil dried out, crusting. It was found that natural crust resistance to penetration was greater for those formed on disked plots than on plowed plots.In laboratory trials, using a sandy silt loam (typic ustipsamment) soil, crusts were formed by simulated rainfall (intensity of 10 mm/hour, rainfall applications of 5, 10, and 30 mm in one or two simulated rainstorms). These crusts were found to be less penetrable than the natural ones for the same soil under natural field conditions at the same water contents.Wheat seedling penetration of soil crusts was evaluated under laboratory conditions, whereas projected penetrability of crusts under field conditions was based on an assumed water potential and subsequent coleoptile thrust in the region of the seedlings. These projected values suggested that crusting in the field may not be the cause for a bad stand, except under extremely adverse conditions. These projections illustrate the urgency of including dynamic considerations of seedling performance in the future studies of small grains germination and emergence under and through crusting soils.

Pedogenic Distribution of Zinc in Mollisols and Associated Entisols in Nebraska

AbstractThe distribution of total Zn in a Udie Haplustoll (Moody) and a Typic Argiustoll (Holdrege) formed in Peoria loess in Nebraska is related to the accumulation of illuvial clay in these soils. In Typic Ustorthents (Crofton and Coly) formed in Peoria loess, a comparable distribution of noncarbonate clay and total Zn does not occur. Larger amounts of Zn in noncarbonate clay from the upper sola of the four profiles than in noncarbonate clay from their C horizons suggest that Zn is released from soil minerals and cycled by vegetation during biopedogenic weathering, then becomes associated with noncarbonate clay in the A horizons following decomposition of plant residues. In Moody and Holdrege, however, maximum amounts of Zn in the total soil occur in the B horizons of clay maxima, suggesting that Zn moves in association with clay from the A to the B horizons during the genesis of these soils.