Typic Hapludult Research Articles

Land management effects on nitrogen and carbon cycling in an Ultisol

Soil carbon (C) content in agro‐ecosystems is important in a global context because of the potential for soil to act as a sink for atmospheric CO2. However, soil C storage in agro‐ecosystems can be sensitive to land management practices. The objective of this study was to examine the impact of land management systems on C and nitrogen (N) cycling in an Ultisol in Alabama. Soil samples (0–10, 10–20, and 20–30 cm depths) were collected from a Marvyn sandy loam soil (fine‐loamy, siliceous, thermic Typic Hapludults) under five different farm scale management systems for at least 5 years. The five systems were cotton (Gossypium hirsutum L.) production managed with 1) conventional tillage only, 2) conventional tillage with a grazed winter cover crop (wheat, Triticum aestivum L.), 3) conservation tillage with a winter cover crop grown for cover only with strip tillage; or taken out of cotton production with either 4) long‐term fallow (mowed), or 5) Conservation Reserve Program with loblolly pine (Pinus taeda L.) (CRP‐pine). Total N, total organic C (TOC), total P, and soil C:N ratios were determined. Potential C mineralization, N mineralization, C turnover and C:N mineralization ratios were determined on samples during a 30‐day laboratory incubation study. The fallow system had significantly higher TOC concentration (7.7 g kg‐1 C) while the CRP‐pine system had lower TOC concentration (3.1 g kg‐1 C) compared with the farmed management systems (=4.7 g kg‐1 C). The fallow system had a significantly lower C turnover at all three soil depths compared with the other management systems. At the 0–10 cm depth, the highest C:N mineralization ratio levels were observed in management systems receiving the most tillage. Our results indicate that for Ultisols in the Southeast the use of surface tillage in land management systems is a controlling factor which may limit soil C sequestration.

Growth Responses and Performance of Kentucky Bluegrass under Summer Stress

Cultivars and selections of Kentucky bluegrass (Poa pratensis L.) exhibit varying degrees of summer stress tolerance. Understanding the factors associated with performance under summer stress is important for identifying stress tolerant germplasm. The objective of this field study was to evaluate shoot and root growth responses of 10 Kentucky bluegrass genotypes subjected to high temperature and drought stress conditions in New Jersey. Turf canopy characteristics, shoot and root growth responses, and soil water depletion patterns were evaluated on a Nixon Loam (fine-loamy, mixed mesic Typic Hapludult) and used to characterize Kentucky bluegrass selections having variable summer stress tolerance. Tolerant entries maintained 19% more roots at the 15- to 30-cm depth in 1995 and 65% more roots at the 30- to 45-cm depth than intolerant entries. Gravimetric soil water contents of tolerant plots were significantly lower at the 15- to 30-cm depth than intolerant entries for both years. Tolerant Kentucky bluegrass, able to exploit deep soil moisture under heat and drought conditions, exhibited significantly fewer summer stress symptoms, had significantly lower stomatal resistance (based on subset of cultivars), and maintained canopy temperature 5°C cooler than intolerant entries at the end of stress periods. This indicated that maintenance of transpirational cooling was an important factor associated with better summer stress performance of turf plots under high temperature and drought conditions in New Jersey.

Effectiveness of Switchgrass Filter Strips in Removing Dissolved Atrazine and Metolachlor from Runoff

AbstractThe effectiveness of switchgrass (Panicum virgatum L.) filter strips in removing dissolved atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine) and metolachlor (2‐chloro‐N‐2‐ethyl‐6‐methylphenyl‐N‐2‐methoxy‐1‐methylethyl acetamide) in runoff was investigated using aluminum‐tilted beds set at 1% slope, filled with Emporia sandy loam soil (fine‐loamy, siliceous, thermic Typic Hapludults) and planted to switchgrass. Solution containing herbicides, followed by water alone after 2 and 4 wk were applied on the up slope of beds with and without switchgrass. Water samples from surface flow, lateral, and vertical leachates as well as soil samples were analyzed for the two herbicides using a gas chromatograph. Switchgrass filter strips reduced the mass of dissolved atrazine and metolachlor by 52 and 59% from the applied runon, respectively. The bare soil strips removed 41% of atrazine and 44% of metolachlor. Less than 0.5% of the applied herbicide was released by the two water runons 2 and 4 wk after herbicide‐solution application. The average concentrations of both herbicides in surface runoff were greater than in leachate samples. Herbicides were removed by the soil as runon moved through the soil profile. The concentration of either herbicide on the top surface (0–2.5 cm) was greater than in the soil immediately below (2.5–5 cm). Degradation of both herbicides was faster in beds with switchgrass than without. Greater amounts of both herbicides were retained in the first 67‐cm section of beds with the grass than without. Switchgrass helped to remove the herbicides by slowing runoff velocity and increasing their retention by soil.

Fescue Growth as Affected by Municipal Compost Fertilizer Blends

A growth chamber study with Sassafras soil (Typic Hapludults) was conducted to find combinations or blends of composts and fertilizers which would be equal to the inorganic N fertilizer requirement of tall fescue (Festuca arundinacea). Soil was amended with four rates of compost to provide 0, 16.7, 33, or 50 percent of the total 300 kg N ha−1 applied. The remaining N, 100, 83.3, 67, or 50 percent was provided by NH4NO3. Composts used were a biosolids compost(BC) or a compost made from both biosolids and refuse(MC). Shredded hardwood bark (B) and N fertilizer combinations were tested to determine the effect of the organic matter fraction in compost on fescue. All combinations were compared to 50 percent (N50) to 100 percent (N100) fertilizer (300 kg N ha−1 NH4NO3) application rates and to each other. Yield and N uptake from the N83 and N100 were equal. Fescue yields of blends were lower than N83 or N100. The 33 percent biosolids/refuse compost N:67 percent NH4NO3 (MC67) combination had equal N uptake to N83 or N100. Because compost N is only partially mineralizable during the first year, the equality of compostfertilizer treatments to fertilizer alone suggests that other ingredients than N are benefitting the fescue. Yield and N uptake from blends containing shredded bark were equal to the N fertilizer alone treatments indicating that there was no benefit to fescue from the bark (organic matter) addition in this study. The data suggest that some composts may substitute for a portion of the N requirement of crops.

GROWTH OF TALL FESCUE IN COMPOST/FERTILIZER BLENDS

Composts are considered low-analysis fertilizers because their N and P content is from 1 to 2% and the N mineralization rate is near 10%. If compost is added to agricultural land at the N requirement of grain crops (40 to 100 kg ha−1), application rates approach 40 to 100 mt ha−1. Much lower rates may be advisable to avoid accumulation of constituents such as heavy metals found in some composts. Combining low-amendment rates of composts with sufficient fertilizer to meet crop requirements is an appealing alternative which (i) utilizes composts at lower rates than those needed to supply all of the crop N requirement, (ii) reduces the amount of inorganic fertilizer applied to soils, and (iii) reduces the accumulation of nonnutrient compost constituents in soils. A study was conducted to compare the effects of blends of biosolids compost (C) with urea (U) or NH4NO3(N) fertilizers with fertilizer alone on tall fescue (Festuca arundinacea L.) growth and N uptake. Blends that provided 0, 16.7, 33, or 50% of the 100 mg N kg−1 application rate as compost N and 100, 83.3, 67, or 50% as fertilizer N were added to Sassafras soil (Typic Hapludults). Fescue was grown on the blends in a growth chamber for 109 days. Fescue yields decreased linearly with decreasing fertilizer level for both NH4NO3 and urea and with or without compost. Nitrogen uptake by fescue was different for fertilizer- than for compost-amended pots, depending on the rate of fertilizer added. Paired comparisons based on cumulative 109-day data indicated yields from NC67 (67% NH4NO3-N, 33% compost N) and NC83 equaled the yield of N100. Similarly for blends containing urea, UC67 yield was equal to U100. Nitrogen uptake from NC83 was equal to N100, but N uptake from NC67 was significantly less than from N100. Nitrogen uptake by UC67 was significantly less than U83 which had a greater mean N uptake than N100. The data suggest that compost N can replace one-third of the fertilizer N required by fescue without decreasing yield. Because the mineral N plus the mineralization of organic N that comprises the compost N portion of the blends did not equal that of the corresponding fertilizer alone, constituents other than N contributed to yields from the compost fertilizer blends.

Neotyphodium coenophialum‐endophyte infection affects the ability of tall fescue to use sparingly available phosphorus

Neotyphodium coenophialum, (Morgan‐Jones & Gams) Glenn, Bacon & Hanlin, infected tall fescue (Festuca arundinacea Schreb.) plants perform better than non‐infected isolines on phosphorus (P)‐deficient soils. Our objective was to characterize growth and P uptake dynamics of tall fescue in response to endophyte infection and P source at low P availability in soil. Two tall fescue genotypes (DN2 and DN4) infected with their naturally occurring N. coenophialum strains (E+), and in noninfected (E‐) forms were grown in Lily soil (fine loamy siliceous, mesic Typic Hapludult) in a greenhouse for 20 weeks. Three soil P treatments were imposed: no P supplied (control) and P supplied as commercial fertilizer (PF) or as phosphate rock (PR) at the level of 25 mg P kg‐1 soil. Interaction of tall fescue genotype and endophyte status had a significant influence on mineral element uptake suggesting high specificity of endophyte‐tall fescue associations. Endophyte infection did not affect root dry matter (DM) when no P was supplied but shoot DM was reduced by 20%. More biomass was produced and greater P uptake rate occurred in PR than PF treatment. Root DM was greater in E+ DN4 than E‐DN4 when supplied with either PF or PR. In contrast, endophyte infection did not affect root DM of DN2, regardless of P source. Relative growth rate (RGR) of E+ plants grown with PR was 16% greater than that of E‐plants. Endophyte infection did not improve growth or P uptake in PF treatment. When PR was supplied, P uptake rate was 24% greater in E+ DN2 than E‐ DN2, but endophyte infection did not benefit DN4. Phosphorus‐use efficiency was 6% less in E+ DN2 but 16% greater in E+ DN4 compared to E‐ plants, regardless of P source. Root exudates of E+ DN2, but not E+ DN4 solubilized more P from PR than those of E‐ plants. The correlation between root RGR and P uptake rate was relatively high for E‐ plants (r=0.76), but low for E+ plants (r=0.27) grown with PR. Results suggest that P uptake by E+ tall fescue might rely on mechanisms other than an increase in root biomass (surface area). Endophyte infection modified tall fescue responses to P source. This phenomenon was associated with modes of P acquisition which included enhanced activity of root exudates in releasing P from PR in E+ plants (DN2), and increased root biomass (DN4). The dominant means of P acquisition may be determined by a specific association of endophyte and tall fescue genomes. Endophyte‐tall fescue association plasticity contributes to widespread success of symbiotic in marginal resource conditions.

Liming acid forest soils with flue gas desulfurization by-product: growth of Northern red oak and leachate water quality

Flue gas desulfurization (FGD) by-product is created when a dolomitic lime [CaMg(CO 3) 2] is used to remove SO 2 during the burning of high sulfur coal in electricity generating power plants. This study evaluated growth of Northern red oak ( Quercus rubra L.) in an acid forest soil (Rayne silt loam—a fine loamy, mixed, mesic, Typic Hapludult) and water leachate quality when FGD by-product was applied topically or mixed within the A horizon at rates equivalent to 0.25, 0.50, 1.0, 1.5, 2.0 and 2.5 times the soil’s lime requirement. Soils were leached with deionized water on a monthly basis and the leachate samples were analyzed for pH, conductivity, P, S, B and metals (Al, Ca, Cr, Cu, Fe, Mn, K, Mg, Pb, Ti and Zn). Tree growth significantly increased ( p⩽0.05) when soil was treated with FGD and the greatest growth (75% increase over the untreated control) occurred when FGD was applied at 1.5 times the lime requirement rate. Boron toxicity symptoms were observed in plant tissue when FGD by-product was applied at two times (or higher) the lime requirement rate. Sulfur concentration increased from less than 10 mg l −1 (control soil) to 234 mg l −1 (soil treated with FGD at 2.5 times the lime requirement) in the leachate four months after treatment. Boron also approached toxicity concentrations (≈l mg l −1) in the leachate from soil treated at the highest rate during the initial leachings, but concentrations tended to decline with time. Applying FGD by-product onto acid forest soils has the potential to provide growth benefit to a commercially important tree species (red oak) but care will need to be taken to avoid using FGD materials that may release toxic levels of B.

Rainfall influence on imazethapyr bioactivity in New Jersey soils

Greenhouse studies were conducted with soil columns to determine the influence of rainfall amount, intensity, and time of application on the bioactivity of 0.07 kg ae ha−1imazethapyr in three soils of New Jersey: the Berryland sand (BLS) (sandy, siliceous, mesic Typic Haplaquod), Aura sandy loam (ASL) (mixed, mesic Typic Hapludult), and Quakertown silt loam (QSIL) (mixed, mesic Typic Hapludult). The Brockman-Duke simulated rainfall machine was used for rainfall application and smooth pigweed as an imazethapyr bioactivity indicator. As rainfall amount increased from low to high (75 to 300 mm mo−1equivalent) imazethapyr bioactivity declined significantly in BLS and ASL but was unaffected in QSIL. Rainfall intensity from 6 to 25 mm h−1had no effect on imazethapyr bioactivity in the three soils. A delay in rainfall application up to 14 d after herbicide application significantly reduced the bioactivity of imazethapyr in BLS but had no effect in ASL and QSIL.

Effects of coalbed methane‐produced water on sorghum‐sudangrass growth and soil chemical properties1

Production of methane gas from coal seams generates well water that is slightly to moderately saline. Since land application is a potential method of disposal for this water, a greenhouse study was conducted to evaluate plant response and changes in soil chemical properties resulting from irrigation with coalbed methane‐produced water. The soil was a Montevallo (Typic Dystrochrepts)‐Nauvoo (Typic Hapludults) association located in northern Alabama. Two irrigation methods used in the initial greenhouse test were 1) continuous, irrigation 24 h d‐1 and 2) intermittent, irrigation for 12 h and off for 24 h. In a second greenhouse test, three irrigation methods were used: 1) continuous, irrigation for 24 h d‐1, 2) intermittent, irrigation for 12 h and off for 48 h, and 3) irrigation to maintain field capacity, by daily additions of the respective irrigation water. The flow rate for continuous and intermittent irrigation treatments was 3.75 mm h‐1. In each greenhouse test, 5 levels of salinity were generated by mixing well‐produced water with deionized water to give solutions containing 0, 10, 20, 40, and 100% well‐produced water (specific conductance (second greenhouse test) of 0.2, 1.4, 2.2, 4.4, and 9.3 dS m‐1, respectively). Corresponding sodium adsorption ratios were 0.1, 27, 36, 55, and 81, respectively. Sorghum‐sudangrass [Sorghum bicolor (L.) Monech] was harvested for forage yields and chemical analysis at 14–30 days after initiation of irrigation treatments. Results from these preliminary short term, greenhouse studies show that coalbed methane produced water that is typical for Alabama (total dissolved solids ≤2000 mg L‐1) can be applied to highly weathered soils. The results indicate that plant growth of summer annual grasses will be optimized if an irrigation system is used to apply produced water at a rate to maintain soil moisture at or near field capacity.

Soil‐Climate Effects on Nitrate Leaching from Cattle Excreta

AbstractManagement intensive grazing (MIG) is a grazing system in which animals at a high stocking density are rotated through several paddocks at short time intervals (12–24 h) so that animal performance is maximized. Although MIG has the potential to increase dairy farm profitability in the northeast USA, recent work in this region has shown that a substantial amount of N recycled through urine is leached below the root zone. How soil properties, particularly water‐holding capacity, can affect NO3‐N leaching from beneath urine and feces spots under the climatic conditions of the northeast USA is not known. We conducted a field study to measure NO3‐N leaching loss from spring‐, summer‐, and fall‐applied urine and summer applied feces beneath N‐fertilized orchardgrass (Dactyls glomerata L., cv. Pennlate) using large drainage lysimeters installed in two soils that differed greatly in soil water storage capacity. The study sites were located in central Pennsylvania on a Hagerstown silt loam soil (fine, mixed, mesic Typic Hapludalf) and a Hartleton channery silt loam (loamy‐skeletal, mixed, mesic Typic Hapludult). Compared to the Hagerstown soil, the Hartleton soil provided an 85% decrease in plant N uptake, a 52% increase in leachate volume, but no significant increase in NO3‐N leaching beneath urine spots. However, the lower soil water‐holding capacity of the Hartleton soil caused the NO3‐N leaching losses to be more evenly distributed over the year.

Modified Iron‐Oxide‐Impregnated Paper Strip Test for Soils Treated with Phosphate Fertilizers

AbstractThe Fe‐oxide‐impregnated paper strip (Pi) test with 0.01 M CaCl2 has been proposed as an improved soil test for evaluating available P from soils treated with phosphate rock (PR) and triple superphosphate (TSP). However, conclusive evidence for this suggestion has not been reported. This study was conducted to evaluate the suitability of the Pi test for both PR and TSP. In a greenhouse study, two acid soils — Hartsells silt loam (fine‐loamy, siliceous, thermic Typic Hapludult) and Hiwassee clay loam (fine, kaolinitic, thermic Rhodic Kanhapludult) — were mixed with ground (0.15‐mm, 100‐mesh) North Carolina (NC) PR or commercial‐grade granular TSP at 0 to 300 mg P kg‐1 soil. The soil samples were preincubated for 2 wk before maize (Zea mays L.) was planted and grown for 5 wk. Prior to planting, soil samples were analyzed by three soil tests: Bray I, Pi test with 0.01 M CaCl2, and Pi test with 0.02 M KCl. The results showed that NC‐PR and TSP were equally effective in increasing dry‐matter yield and P uptake by maize in Hartsells soil. North Carolina phsophate rock was approximately 83 and 91% as effective as TSP in increasing drymatter yield and P uptake, respectively, in Hiwassee soil. When P uptake was plotted against soil test values, both the Bray I and Pi test with CaCl2 underestimated available P from NC‐PR for TSP‐treated soil. Available soil P estimated by the Pi test using KCl instead of CaCl2 was more closely related to P uptake with both NC‐PR and TSP. More P was extracted from NC‐PR by the Pi test with KCl than with CaCl2, whereas no effect was observed for TSP.

Investment Returns from Three Sub-surface Microirrigation Tubing Spacings

Sub-surface microirrigation (SMI) tubing costs make up 33 to 60% of total purchase and installation costs of the system, depending on tubing spacing. Purchase and installation costs of SMI systems can be lowered by $290/acre by increasing tubing spacing from 3 to 9 ft. Yields may be reduced due to less uniform placement of water in the crop root zone. The net present values (NPVs) of three SMI tubing spacings were estimated for systems irrigating corn (Zea mays L.) and peanut (Arachis hypogaea L.). The analysis included investment costs for purchasing and installing the irrigation system but did not include water source development costs. Irrigated yield responses and irrigation applications came from field experiments conducted from 1986 to 1995 at Suffolk, VA, on an Uchee loamy sand (loamy, siliceous, thermic Arenic Hapludult) with inclusions of Emporia loamy sand (fine-loamy, siliceous, thermic Typic Hapludult). The 6-ft tubing spacing had the highest NPV of $14/acre. The low NPV indicates it is unlikely to be profitable when water source development costs are included. NPVs of 3-ft and 9-ft spacings were -$28 and -$104/acre, respectively. Six-foot spacing had lower yields and lower investment costs than 3-ft spacing. Increasing the proportion of corn in the rotation lowered the advantage of 6-ft spacing. Higher peanut and corn prices or reduced tubing prices narrowed the difference in NPVs between 3-ft and 6-ft spacings. Six-foot tubing spacing results in highest returns when SMI is used for corn-peanut rotations on sandy soils in Virginia/North Carolina.

Runoff and Sediment Losses from Natural and Man‐Made Erosion Control Materials

Man‐made erosion control materials are increasingly being used at construction sites. The performance of these materials in comparison to natural materials is largely unknown. A rainfall simulation study was designed in which four man‐made materials (wood excelsior, jute fabric, coconut fiber blanket, and coconut strand mat) and two natural materials (straw and turfgrass sod) were evaluated. The erosion control materials were evaluated on a Sassafras loamy sand (fine loamy, mixed mesic Typic Hapludult) having a 8% slope and on a Sassafras sandy clay loam (fine, silty, mixed mesic Typic Hapludult) having a 14 to 21% slope. Disturbed soil surface areas (0.76 m2 each) were covered with each material and subjected to a 96 mm hr−1 simulated rainstorm. Runoff and sediment loss rates were determined every 5 rain for 35 min after recording the time required for runoff initiation. Sod was the only material that extended the time required for runoff initiation. Runoff from all materials was less than bare soil for the first 5 rain of runoff; however, only straw, jute, and sod reduced runoff over the entire storm event. The total amount of runoff, compared with bare soil, was decreased by 61% for sod, 25% for straw, and 16% for jute. Erosion control materials reduced bare soil erosion by 80 to 99%. Of the man‐made rosion control materials, only jute reduced runoff and sediment losses at both locations. Therefore, of the materials tested, only sod, straw, and jute would be expected to effectively reduce both runoff and sediment losses

Cadmium and zinc in acid tropical soils: I. Soil physico‐chemical properties effect on their adsorption

Interactions of heavy metals, such as cadmium (Cd) and zinc (Zn) at the soil particle surfaces play an important role in controlling their leaching losses to the underground water and their availability to plants. Adsorption isotherms for eight soils [Apas (Rhodic Hapludox), Batang (Typic Plinthudult), Jarangan (Xanthic Hapludox), Katai (Typic Hapludult), Koyah (Oxic Dystropept), Lumisir (Typic Plinthudult), Paliu (Typic Hapludult), and Table (Typic Hapludox)] from major cocoa (Theobroma cacao L.), oil palm (Elaeis guineensis Jacq.), and rubber (Hevea brasiliensis Muell Agr.) growing areas in Tawau, Sabah, Malaysia were determined at concentrations of 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100 mg Cd or Zn mL‐1 in a 0.025M calcium chloride (CaCl2‐2H2O) solution. The adsorption of Cd and Zn by the soils can successfully be explained by the Freundlich equation (r = 0.832** ‐ 0.977**) as compared to the Langmuir equation (r = 0.130ns ‐ 0.977**). The ability of the soils to adsorb Cd and Zn differed markedly with the highest obtained in Table soil (18.4 mg Cd kg‐1 soil) for Cd and Koyah soil (29.97 mg Zn kg‐1) for Zn. The important soil parameters in controlling the adsorption of both Cd and Zn in acid tropical soils were cation exchange capacity (CEC) (r = 0.888**), total aluminium (Al) content (r = 0.675**), and extractable‐Al (r = 0.875**).

Cadmium and zinc in acid tropical soils: III. Response of cocoa seedlings in a greenhouse experiment

Many phosphate rock (PR) materials used as direct application of fertilizer containing variable amounts of heavy metals, such as cadmium (Cd) and zinc (Zn). The effect of Cd and Zn addition to unlimed and limed (pH 5.5) soils on the growth of cocoa seedlings (Theobroma cacao L.) U1T1 X NA33 hybrid was conducted in the field at Kunak, Tawau, Sabah. Cadmium [as Cd(SO4)lb8H2O] and Zn [as Zn(SO4)#lb7H2O] were added in solution form at 0, 2.8, 14, and 28 kg Cd ha‐1 year‐1 and 0, 28, 140, and 280 kg Zn ha‐1 year‐1, respectively, to each of three top (0–15cm) soils from Katai (Typic Hapludult), Koyah (Oxic Dystropept), and Table (Typic Hapludox). At harvest, plant growth parameters, plant height and plant dry‐matter yield, were measured. Cadmium and Zn contents were partitioned into plant roots, stems, leaves,‐and in the soils. Plant height and dry‐matter yield of cocoa differed markedly between levels of Cd and Zn added to unlimed and limed soils. A positive plant growth response of the added Cd and Zn was clearly apparent in the Table soil as compared to the Katai and Koyah soils. A significant increase (p<0.05) in all plant growth parameters was obtained at the concentration of 2.8 mg Cd kg‐1 and 28 kg Zn kg‐1added to the limed soils. In contrast, a significant (p<0.05) reduction of the parameter measured was obtained in unlimed soils at a concentration of more than 14 mg Cd kg‐1 and 140 mg Zn kg‐1 of soil. Analysis of the Cd and Zn contents showed that substantial amounts of these elements accumulated in the leaves, stems, and roots of cocoa, while very little were present in the soils. Liming the soils before the addition of Cd and Zn significantly (p<0.05) reduced the amount of metal accumulation in these plant parts.

Cadmium and zinc in acid tropical soils: il influence of humic acid addition on soil properties and their adsorption

Cation exchange capacity (CEC) is one of the most important factor in influencing the adsorption of cadmiun (Cd) and zinc (Zn) in some acid tropical soils from Tawau, Sabah, Malaysia. The effect of humic acid addition on chemical properties of the soils was evaluated in an incubation study. Humic acid was added to the three soils, Katai (Typic Hapludult), Koyah (Oxic Dystropept), and Table (Typic Hapludox) at concentrations of 0, 50, 100, 150, and 350 mg carbon (C) kg‐1 soil and incubated for 30 days. Changes in pH, organic‐C, CEC, and adosrption of Cd and Zn were measured on these soils. With the exception of the Table soil, soil pH increased with increasing levels of humic acid addition; the same trend was also observed for organic‐C and CEC of the soils. The adsorption of Cd and Zn by the soils can fully be explained by the Freundlich equation (r = 0.916** ‐ 0.987**). The soils had a greater ability (almost 2‐fold) to adsorbed Zn compared to Cd. The highest Cd and Zn adsorbed by the soil were 22.32 mg Cd kg‐1 for the Table soil and 42.3 mg Zn kg‐1 for the Koyah soil. Sequential extraction of soil amended with humic acid showed that Cd and Zn can be partitioned into five operational geochemical fraction viz. exchangeable, bound to carbonate, bound to iron (Fe)‐manganese (Mn) oxides, bound to organic matter, and residual forms. A larger portion (50%) of Cd was in exchangeable form and the lowest (9%) in organic‐bound form. Zinc in Fe‐Mn oxides form accounted for about 49% of the total and 5% in organic‐bound form.

Brachytic Stem Trait, Row Spacing, and Plant Population Effects on Soybean Yield

Brachytic stem (sb1sb1sb2sb2) of soybean [Glycine max (L.) Merr.] is characterized by shortened internodes, resulting in shorter, sturdier plants than normal stem types. Although studies have shown yield of brachytics to be less than normal types, this trait may have potential for higher yield in some environments. Little information is available on response of brachytics to planting pattern, particularly for duration of development stages or yield components. A field study was conducted to determine brachytic trait effects on yield, agronomic traits and yield components of four near‐isoline pairs, each consisting of one normal and one brachytic near‐isoline tested at plant populations of 51 and 26 plants m−2 and row spacings of 76 and 28 cm in four environments. Soil types were a Cahaba fine sandy loam (fine‐loamy, siliceous, thermic Typic Hapludults) and a Norfolk fine sandy loam (fine‐loamy, siliceous, thermic Typic Kandiudults). Normal types yielded more and responded to narrow rows; brachytics did not. Row spacing and plant population did not affect most other traits. Brachytics flowered later and had shorter reproductive period than normal types. Brachytic soybean produced more branch and mainstem nodes and greater seed mass and harvest index than normal types, but this was not enough to effect yield advantages over normal soybean. We concluded that plant growth and yield performance of the brachytic trait is influenced more by genetic background than other factors; however, under suitable conditions, brachytic soybean's production of larger seeds and more nodes indicates its potential for higher yields.

Harvest Management Effects on Dry Matter Yield, Forage Quality, and Economic Return of Four Cool-Season Grasses

Perennial cool-season grasses are widely grown in Pennsylvania and the northeast USA for forage. Harvest management practices that maximize annual economic return of these grasses have not been adequately identified. The objectives of this research were to determine tbe effect of harvest number on dry matter (DM) yield, forage quality, and economic return of orchardgrass (Dactylis glomerata L.), reed canarygrass (Phalaris arundinacea L), smooth bromegrass (Bromus inermis Leyss.), and timothy (Phleum pratense L.). Established stands of these grasses on a Murrill silt loam (fine-loamy, mixed, mesic Typic Hapludult) were harvested at intervals of 70, 45, and 35 d (two, three, or four harvests per year, respectively) during four consecutive years. In all years and for all grass species, forage quality (crude protein [CP] and digestible dry matter [DDM]) was greatest when the forage was harvested at a 35-d interval. However, in years when rainfall was below normal, the 35-d harvest interval resulted in the lowest DM yields. There was no difference in net economic return for any species when rainfall was below normal. In years when rainfall was at or above normal, the 35 and 45-d harvest interval produced greater net economic return than the 70-d interval for all grasses except timothy, which did not differ in economic return among harvest schedules. The highest quality forage and greatest net economic return were obtained in years with normal or greater rainfall when orchardgrass, reed canarygrass, and smooth bromegrass were harvested at intervals of 35 to 45 d. Harvest intervals for the same species in dry years and timothy in either dry or wet years should be based on the nutrient needs of the consuming animal. Forage for high producing animals (e.g., lactating dairy cows), which require relatively high forage digestibility to achieve adequate intake levels, must be harvested more frequently (35 to 45 d) than forage for animals with lower intake requirements (e.g., nonlactating cows).

Phosphorus Nutrition Affects Wheat Response to Water Deficit

AbstractPlant leaf area affects both plant growth and yield. Although the effects of phosphorus and water availability on leaf area development have been studied as isolated factors, little work has been done on their possible interactions. A pot experiment was conducted to investigate the effects of both P and water availability on early leaf appearance and expansion in soft red winter wheat (Triticum aestivum L.), and to determine whether the effect of water deficit changes at each level of P nutrition and whether the soil water content affects plant P uptake. The soil was a Lonewood loam (fine‐loamy, siliceous, mesic Typic Hapludult), which had an available P level of 8.2 mg P kg−1 (Mehlich III). Additional P was applied at 0, 10 and 20 mg P kg−1 soil. Water treatments consisted of keeping soil‐water content at 80% (well watered) and 53% (stressed) of the 10 kPa soil‐water content. Plant development, leaf appearance and expansion, and stomatal resistance were measured during the experiment. At harvest (38 d after emergence), leaf area, aboveground biomass, and P concentration were measured. Phosphorus and water availability exhibited a significant interaction on tiller and leaf appearance, which were reduced by water stress but only at 0 applied P. As individual factors, P and water influenced different plant features. Lack of applied P decreased the rate of leaf appearance and, therefore, the final number of leaves and leaf area per plant. Water deficit reduced individual leaf area and, at 0 applied P, reduced rate of leaf appearance, number of simultaneously expanding leaves, and final number of leaves. Phosphorus uptake was increased only with added soil P, and not by water stress. The ability of plants to cope with mild water stress was enhanced by adequate P nutrition.

Loessial Soils of Delaware: Taxonomy and Map‐Unit Assessment

AbstractMap units named for the Matapeake series (fine‐silty, mixed, mesic Typic Hapludults) comprise one‐third of the Coastal Plain in the soil survey of northern Delaware. The concept was one of well‐drained soils formed in thin loess over coarse‐textured fluvial sediments. This study uses characterization data from pedons within the loess‐blanketed terrain of northern Delaware to assess the taxonomy and composition of Matapeake map units. All pedons are Alfisols rather than Ultisols, and this status has not been influenced by liming. Fine‐loamy rather than fine‐silty soils typically occur where loess is &lt;80 cm thick. Much soil variability exists on interfluves where thin loess discontinuously blankets the irregular surface of the sandy Pensauken Formation. This results in an inability to map specific consociations, even for large‐scale, detailed surveys. The existing soil survey used specific map units — consociations named for phases of soil series — that do not adequately depict the diversity on mappable landscapes. The Matapeake and associated series used in this area are too narrowly defined in ranges of characteristics, are too general in geographic setting, have loess thickness limits that are not concordant with particle‐size classes, and leave gaps in the lithologic‐hydrologic continuum. They therefore provide little utility for organizing knowledge, understanding relationships, or as objects for research. Soil survey in this area requires more generalized map units, greater emphasis on stratigraphy and geomorphology and their interaction to influence hydrology and lithology, and less emphasis on artificial conceptual groupings at the lowest taxonomic category, the series.