bluuebunny/crossref_metadata_2025 huggingface dataset:
Corn Seedling Root Growth as Influenced by Soil Physical Properties1
Authors: Logsdon S. D. , Reneau R. B. , Parker J. C.
Published: July 2010

Management practices often affect soil physical properties adversely thus reducing root growth. In the field difficulty arises in determining which soil physical property is influencing root growth because the factors are not readily separated. The purpose of this study was to examine the effects of isolated soil physical factors on corn (Zea mays L.) seedling growth under controlled conditions. Corn was grown in A horizon material of Groseclose silt loam (clayey, mixed, mesic Typic Hapludult) at four bulk densities (1.10, 1.22, 1.35, and 1.47 Mg/m3), four lower soil moisture levels (0.24, 0.21, 0.18, and 0.15 m3/m3), four higher soil moisture levels (0.24, 0.27, 0.30, and 0.33 m3/m3), and three temperatures (25, 21, and 17°C) in growth chamber experiments. Optimal conditions as indicated by maximum root elongation for corn in Groseclose silt loam occurred with volumetric moisture contents from 0.24 to 0.27 m3/m3, bulk densities <1.22 Mg/m3, and a temperature of approximately 25°C. High bulk density, oxygen stress, low temperature, and water stress all reduced root elongation to some extent. Low temperature had the most dramatic effect. At 6 days corn root length at 21°C was only about 20% of that at 25°C, whereas root length at 17°C was only about 5% of that at 25°C. As bulk density increased, root length decreased. After 4 days high soil moisture stimulated root growth. Root length was not reduced by low soil moisture except at the lowest level (equivalent to a matric potential of −1090 kPa).
Quality Analysis of Summer‐Annual Forages. II. Effects of Forage Carbohydrate Constituents on Silage Fermentation1
Authors: Fisher D. S. , Burns J. C.
Published: July 2010

Fermentation characteristics of many of the sorghum (Sorghum bicolor L.) types and cultivars within types and the consequent relationship between nonstructural carbohydrates and fermentation products of such forages has not been adequately examined. The objectives of this study were to examine fermentation products and changes in nonstructural carbohydrate fractions with ensiling and relate these to the unfermented forage characteristics of one millet (Pennisetum americanum L.), one corn (Zea mays L.), and eight sorghum cultivars. The buffering capacity of unfermented forage was found to be greater (P<0.01) in sorghum (9.8 mL 0.1 M lactate) than in corn (8.0 mL 0.1 M lactate). Starch was less susceptible to degradation during fermentation than sugar. High levels of starch resulted in fermentation and loss of a smaller proportion of the total nonstructural carbohydrates (TNC). Reductions in TNC ranged from 61 g kg−1 for ‘Tifleaf‐I’ millet to 239 g kg−1 for ‘NK‐367’ forage sorghum at Location 1 and 30 g kg−1 for ‘Savanna‐5’ grain sorghum to 167 g kg−1 for NK‐367 forage sorghum at Location 2. Predictive equations for the proportion of TNC retained after ensiling were developed using unfermented forage characteristics as independent variables. These regression equations accounted for 70 to 91% of the variation. By weight, the most important fermentation products were lactate (42.9–114.1 g kg−1), acetate (9.4–39.4 g kg−1), and ethanol (1.4–50.0 g kg−1). Only small quantities of substrate were fermented to propionate (0.0–1.3 g kg−1), butyrate (0.3–1.6 g kg−1), and acetaldehyde (0.4–1.3 g kg−1). Palatability was positively correlated with acetate (r=0.70*), propionate (r=0.91**), and total sugars in the silage (r=0.84**).
Radiation Balance of Dryland Grain Sorghum as Affected by Planting Geometry1
Authors: Steiner J. L.
Published: July 2010

The effects of planting geometry on the radiation balance of dryland grain sorghum (Sorghum bicolor L. cv. DK 46) were studied in a field experiment at the USDA‐ARS Conservation and Production Research Laboratory at Bushland, TX, in 1984 on a Pullman clay loam (a fine, mixed, thermic Torrertic Paleustoll). The objective was to reduce the radiation load on a crop through manipulation of planting geometry and to determine whether that would affect crop productivity. Net radiation was 5% higher over wide compared to narrow rows (0.76 and 0.38 m, respectively) when averaged over three population levels from 33 to 110 days after sowing. East‐west rows had 14% higher net radiation than north‐south rows, averaged over two row spacings. The differences in net radiation were due to daytime responses, presumably shortwave albedo differences. Leaf photosynthesis and transpiration rates and stomatal resistance were measured twice during the grain‐filling period. These measurements, taken 5 days after a period of moderate rains, showed no differences in the plant response due to row spacing or direction treatments. Slightly higher leaf temperatures in the high‐population plots may have been related to greater depletion of plant available water than in medium and low population plots (72, 66, and 67% depletion, respectively). After 2 weeks of drying, narrow‐row and high‐population treatments showed greater stress as evidenced by lower transpiration and photosynthesis rates and higher stomatal resistance and leaf temperature. Soil water depletion was 20% less in narrow than wide rows during a 2‐week period spanning the leaf transpiration measurement dates. Leaf photosynthesis, transpiration, temperature, and stomatal resistance were not affected by differences in net radiation due to row spacing or row direction.
Nitrogen Fixation and Translocation in Field‐Grown Fababean1
Authors: Zapata F. , Danso F. , Hardarson G. , Fried M.
Published: July 2010

Fababean (Vicia faba L. var. minor) has high N requirements for optimum yields. There are some indications that this legume can satisfy a greater part of this requirement largely through biological N2 fixation. To confirm these observations, more quantitative estimates of N2 fixed in fababean on different soils and over different seasons are necessary. Also, detailed N nutrition and translocation studies could serve as the basis for any required improvement in N2 fixation. This study assessed the contribution of soil, fertilizer, and fixed N2 to the nutrition and growth of fababean at seven growth stages. The soil used is classified as a Typic Eutrocrept. The A‐value approach, involving the application of 20 and 100 kg N/ha of l5N‐labeled ammonium sulphate to fababean and spring wheat (Triticum vulgare) as a reference crop, respectively, was used to assess the relative contributions of N from fixation, soil, and fertilizer to plant growth. At physiological maturity harvest (126 days after planting), fababean had accumulated 209 kg N/ha, 79% of which was derived from fixation, with about 20% coming from soil and 1% from the labeled fertilizer. These results confirm that fababean has the ability for high N2 fixation. Growth and N2 fixation were, however, low during early growth (0–59 days after planting), but increased rapidly after this period. The maximum N2 fixation rate was achieved between the early and mid‐pod‐filling stages, an interval during which N2 fixation accounted for more than 4 kg N/ha/day. The N2 fixation activity dropped to almost zero after the mid‐podfilling stage. After the mid‐pod‐filling stage, the N demand of the developing seeds and pods was higher than could be satisfied through the negligible soil uptake of N and N2 fixation. Thus, N translocated from the shoot was virtually the only source for pod and seed development at these final stages. With such a high level of N2 fixation in fababean, it was estimated that after grain removal, fababean growth led to a net positive residual N level in soil.
Corn Root Growth and Distribution as Influenced by Tillage and Nitrogen Fertilization1
Authors: Anderson E. L.
Published: July 2010

Tillage alters both soil physical and chemical properties, which in turn alter the environment for root growth and may impact on plant growth, nutrient uptake, and yield. The objective was to compare corn (Zea mays L.) root morphology and distribution in plots under minimum tillage (MT) for 7 yr to conventional tillage (CT) at N fertilization treatments of 0 and 180 kg N/ha. The 3‐yr field study was conducted in the Maryland Piedmont area on a Delanco silt loam (Aquic Hapludult). Three soil cores per plot were taken at vegetative, silking, and dough stages of plant development. A 76‐ mm‐diam steel tube was used to sample to a depth of 0.6 m in the plant row, at midrow (0.38 m), and half way between (0.19 m). The roots collected to 0.6 m accounted for an average of 82% of the total root weight present after grain harvest. Tillage did not significantly affect plant growth or grain yield. Conventional tillage significantly increased root dry weight in only 1 yr. Minimum tillage and N fertilization both increased root weight in the 0‐ to 0.07‐m layer in 2 of the 3 yr. Root mass decreased 90% in the 0‐ to 0.07‐m depth when samples were compared from in the row to 0.19 m away. Nitrogen fertilization decreased milligrams per meter of root and root radius in 2 of the 3 yr, allowing root length to increase in response to N without altering the weight of roots. Root growth was observed under drought and N stress conditions when shoot growth and yield were limited. The period of most rapid root development occurred in the 8 weeks following planting.
Estimation of Biological Nitrogen Fixation Associated with 11 Ecotypes of Panicum maximum Grown in Nitrogen‐15‐labeled Soil1
Authors: Miranda Cesar H. Behling , Boddey Robert M.
Published: July 2010

Contributions of plant‐associated biological nitrogen fixation (BNF) may be important to N nutrition of grasses. Eleven ecotypes of Panicum maximum were planted in the field in concrete cylinders containing soil (Typic Hapludult) that had a low but stable 15N enrichment. Brachiaria radicans (cv. IRI 442) was used as the non‐fixing control, and the plant aerial tissue was harvested eight times over a 390‐day period. At the first harvest of the experiment (17 May 1984), the concentration of N in all the grasses was high and, subsequently, declined during the first 270 days of growth, reflecting the decreasing availability of soil N. Until soil N availability had become the main factor limiting plant growth, it was thought unlikely that any significant contribution of BNF would occur, and this was confirmed by the 15N‐enrichment data. At later harvests (February–April 1985), the N concentrations in the plants were lower and all the P. maximum ecotypes accumulated more than the B. radicans. Over this period, the 15N enrichment of all the P. maximum ecotypes was significantly lower than that of the B. radicans, indicating a contribution of plant associated BNF to the P. maximum ecotypes. Contributions of associated BNF to the P. maximum ecotypes were estimated to be between 24 and 38% of total N incorporated, equivalent to between 5 and 10 kg N ha−1 per 30 days. The significant differences observed in ISN enrichment between P. maximum genotypes suggest that further screening and selection of P. maximum ecotypes for high associated BNF is a worthwhile objective.
Agronomic Evaluation of Poultry Manure as a Nitrogen Source for Conventional and No‐Tillage Corn1
Authors: Sims J. Thomas
Published: July 2010

Poultry manure is useful as a source of N for corn (Zea mays L.) production. An approach to predict available N in poultry manure (PM) was evaluated in a 3‐year (1983–1985) field study with conventional (CT) and no‐tillage (NT) corn. Poultry manure and ammonium nitrate (AN) were applied to an Evesboro loamy sand soil (mesic, coated Typic Quartzipsamments) at rates designed to supply 0, 84,168, and 252 kg potentially available N/ha. Potentially available N (PAN) in the PM was defined as PAN = 80% Ni + 60% No, where N1 = NH+4‐N + NO−3‐N and No = total N ‐ Ni. Soil N1 (0–0.6 m), plant N, corn N uptake, and grain yields were measured. Cover crop N concentrations and N uptake, as well as soil N1 prior to planting and post‐harvest were also determined to estimate residual N from PM and AN. Soil N1 levels and N leaching (to 0.4–0.6 m) were generally higher with AN than PM. Plant N concentrations, N uptake, and corn grain yields were seldom significantly different with PM, compared to AN in 1983 and 1985, but were consistently lower with PM in 1984. Conventional tillage significantly increased grain yields, relative to NT, in 1984 (7.6 and 7.2 Mg/ha, respectively) and 1985 (7.7 and 5.5 Mg/ha, respectively). Little residual N was detected in 1984 or 1985 from prior applications of PM. Based on N budget calculations, the potential existed for considerable leaching losses of N. The efficiency of recovery of added N (ef) averaged 0.56 kg/kg for AN and 0.36 kg/kg for PM. Excess N (NEX) remaining in the soil, based on these ef values, was as high as 265 kg N/ha for PM and 166 kg N/ha for AN. Therefore, despite the selection of PM rates that resulted in soil N, plant N, and corn grain and dry matter yields comparable to those obtained with recommended rates of AN, N leaching may still occur when PM is used on coarse‐textured soils
Dry Season Sweet Corn Response to Mulching and Antitranspirants1
Authors: Shekour G. M. , Brathwaite R. A. I. , McDavid C. R.
Published: July 2010

Sweet corn (Zea mays L. var. saccharata Sturt.) production in Trinidad and Tobago is limited to the rainy season, and the country's requirements is met mainly through imports. Extending the production period into the dry season is desirable for increased local production. The objective of this study was to determine the effect of lucuntu grass (Ischaemum timorense Kunth.) mulch and the antitranspirants phenylmercuric acetate (PMA), alachlor [2‐chloro‐2'‐6'‐diethyl‐N‐(methoxymethyl)‐acetanilide], and Vapor Gard (poly‐1‐p‐menthen‐8‐9‐diyl) on the growth and yield of dry‐season cropped sweet corn. The replicated field trial was established on a River Estate loam (Fluventic Eutropept) at Valsayn, Trinidad and Tobago. The mulch (3.5 Mg/ha) was applied at 38 days after planting (DAP), and the antitranspirants (79.9 and 106.5 g/ha and 24.4 L/ha, respectively) at 38 and 52 DAP. The mulch and antitranspirant treatments resulted in mean increases in plant height and leaf area of 21.1 and 4.8, and 34.5 and 5.7%, respectively, and fresh ear and total dry matter mean increases of 75.0 and 20.0, and 89.7 and 42.0%, respectively, as compared to the limited irrigated control. Only the mulched treatment produced growth and yield similar to the irrigated control. Mulching, PMA, and Vapor Gard, in descending order, were found promising in conserving moisture and improving yield.
Bermudagrass Turf Response to Mowing Practices and Fertilizer1
Authors: Johnson B. J. , Carrow R. N. , Burns R. E.
Published: July 2010

The overall quality of ‘Tifway’ bermudagrass [Cynodon transvaalensis Burtt‐Davies × Cynodon dactylon (L.) Pers.] turf is often determined by the type of mower and fertilizer, and whether clippings are removed or returned. The purpose of this field research study was to determine bermudagrass turf response to N at 100 to 300 kg ha−1 and to K at 50 to 300 kg ha−1 as related to mowing treatments. Treatments were arranged in a split block with subunits in strips. The primary strips were mowing treatments, and subunit strips were fertilizer treatments. The soil type was a Cecil sandy loam (clayey, kaolinitic, thermic Typic Hapludult). A rotary mulching mower maintained the highest quality of bermudagrass, and flail mowing the lowest turf quality throughout the 3‐yr study. Turf quality was not consistent each year. Quality was higher when grass clippings were returned than when removed. In most instances, bermudagrass did not respond to N at rates above 200 kg ha−1. Turf quality and shoot density were as good when K was applied at 50 kg ha−1 as at higher rates. Neither fertilizer treatments nor returning grass clippings influenced thatch accumulation. However, turf cut with a rotary mulching mower had a greater thatch accumulation than did turf cut with a flail mower. Dollar spot (Moellerodiscus spp. and Lanzia spp.) disease occurred more frequently at the lowest N treatment.
Relationships between the Areas of Successive Leaves on Grain Sorghum1
Authors: Maas S. J. , Arkin G. F. , Rosenthal W. D.
Published: July 2010

Grain sorghum [Sorghum bicolor (L.) Moench] plants characteristically exhibit an increase in the areas of successively older leaves on the shoot up to a maximum value, followed thereafter by a decrease in leaf areas. Data from 2 yr of field studies were used to develop empirical functions relating average areas of successive leaves. These functions were representative for a number of published data sets and exhibited the following characteristics: (i) an early exponential phase of leaf area increase apparently terminated by the onset of intraplant competition; (ii) a transition between two linear phases of leaf area increase that appears to be invariant among years, cultivars, and treatments; and (iii) a final phase of decreasing leaf areas that is apparently sensitive to interplant competition and reproductive growth. Data from the literature and studies involving water stress, plant population, and N fertilizer application effects indicate that, while reproductive organ growth may affect some aspects of leaf area development, the onset and severity of intraplant and interplant competition may be more important factors determining individual leaf areas.
No‐Tillage Effects on Population Dynamics of Soybean Cyst Nematode1
Authors: Tyler D. D. , Chambers A. Y. , Young L. D.
Published: July 2010

The soybean [Glycine max (L.) Merr.] cyst nematode (Heterodera glycines Ichinohe) can cause significant reductions in soybean yield in Tennessee. ‘Forrest’ soybean was grown for 4 yr on a Lexington silt loam (Typic Paleudalf) in an experiment comparing soybean production, using six primary tillage methods: five conventional tillage methods (between‐row subsoiling, under‐row subsoiling, chisel plowing, moldboard plowing, and disking) and no‐tillage in chemically killed wheat (Triticum aestivum L.). In the fourth season, cyst numbers were lower in no‐tillage compared to conventional tillage. Race 3 and 4 were present in the experimental area. In the fifth season (1983), two cultivars, Forrest (Race 3 resistant) and ‘Bedford’ (Race 3 and Race 4 resistant), were used. Cyst numbers continued to be higher under conventional tillage with both cultivars. Tillage significantly affected soybean cyst nematode which affected the yield of Forrest but not Bedford. In 1983, yields of Bedford were significantly higher than those of Forrest under conventional tillage but not where the treatment had been no‐tillage for 5 yr. In the sixth season, yields were not significantly affected by tillage. Bedford yielded higher than Forrest across all treatments in the sixth year except in the continuous no‐tillage. In contrast to the fifth season, cyst numbers were lower at the end of the season where Bedford was grown. The two short‐term no‐tillage treatments [one in the previous soybean crop residue (2 yr) and one in wheat (1 yr)] were similar to conventional treatments in yield and cyst counts. Cyst numbers in the continuous 6‐yr no‐tillage were lower than the conventional or short‐term no‐tillage treatments.
Uneven Variation in Plant‐to‐Plant Spacing in Pearl Millet1
Authors: Soman P. , Jayachandran R. , Bidinger F. R.
Published: July 2010

Plant‐to‐plant spacing in farmers' fields of pearl millet [Pennisetum americanum (L.) Leeke] is often highly variable. The effect of typical variation in spacing on grain yield was determined in a range of cropping situations. Twenty within‐row plant spacing patterns were designed so that the variance of spacing (Vs) between plants would range from 0 to 2.3 m2, which represented the range measured from farmers' fields in India. These spacing patterns were tested in three trials conducted on an alfisol (Udic Rhodustalf, Patancheru series) in which plant population, fertility, and season varied. In all the trials, seeds were sown in predetermined positions in each row and later thinned to a single plant per position. As Vs increased from 0.01 to 0.05, 0.10, and 0.70 m2, yields declined 21, 29, and 47%, respectively. This reduction in yield did not depend on fertility level, season, or plant population. Most of the yield reduction could be attributed to reduction in panicle number per plant, the major yield determinant in the cultivar studied. The results suggest that the tillering capacity of pearl millet, although it provides the capacity to adjust to a wide range of plant populations per se, does not provide adjustment to major changes in Vs. Emphasis in the design of new seeding technology should therefore be on even distribution of seed, rather than on control of seeding rate.
Nitrogen Cycling in a Wheat Crop: Soil, Plant, and Aerial Nitrogen Transport1
Authors: Harper L. A. , Sharpe> R. R. , Langdale G. W. , Giddens J. E.
Published: July 2010

An understanding of N cycling in the soil‐plant‐atmosphere components of wheat (Triticum aestivum L.) production systems is necessary to maximize yield and quality. The objectives of this study were to examine N cycling and observe the effects of N surplus and deficit on N absorption/desorption in the soil and atmosphere and to evaluate translocation within the plant. Soil, plant, and microclimate measurements were taken concurrently, and soil, plant, and atmospheric ammonia (NH3) transport determined. During the early vegetative phase, plant N concentration reached a maximum; however, during the remaining growth periods, N concentration decreased even though N uptake from the soil continued until plant maturity. More total N was translocated to grain from leaves than stems, and translocation from the leaves began earlier than that from stems. Isotope and total N studies showed that after anthesis about half of the grain N came from remobilization from leaves and stems and the other half directly from the soil. A progressively larger percentage of N came from mineralized organic matter as the season progressed. Nitrogen was lost as volatile NH3 from the plant after fertilizer application and during the senescence period. Prior to anthesis, atmospheric NH3 absorption was observed during a period when soil N was temporarily unavailable. About 21% equivalent of the applied fertilizer was lost as volatilized NH3. During the period of soil unavailability an amount equivalent to about 1% equivalent of the applied fertilizer was gained from atmospheric NH3 by plant absorption.
Water Deficit Effects on Transpiration and Leaf Growth1
Authors: Rosenthal W. D. , Arkin G. F. , Shouse P. J. , Jordan W. R.
Published: July 2010

Reductions of leaf development and transpiration are closely related to soil water deficits. Few studies have analyzed the effects of water deficits on both processes during different growth stages. A study was conducted to analyze and quantify the effects of water deficits during different growth stages on leaf development (number, extension, and senescence) and transpiration rates of sorghum [Sorghum bicolor (L.) Moench] and cotton (Gossypium hirsutum L.). The study was conducted at the Blackland Research Center at Temple, TX, in a glasshouse using covered pots and in the field using covered lysimeters. In the glasshouse, the sorghum and cotton pre‐flowering treatments were irrigated at 60, 35, 15, and 0% of water used in the control pots. In the lysimeters, water deficit treatments of 50, 30, and 0% plant available water (PAW) were imposed on sorghum during the vegetative period (before panicle initiation and between panicle initiation and anthesis) and after anthesis. Leaf length and transpiration rates were measured two to three times per week. Leaf extension was reduced to 0% of well‐watered sorghum and cotton when the PAW decreased from 50 to 0%. Transpiration per unit leaf area decreased from 100 to 0% of well‐watered sorghum and cotton when PAW decreased from 28 to 0% for each stressed period. Sorghum leaf senescence was enhanced and leaf number increased in the 0% PAW treatments compared to the well‐watered and 30% treatments. These relationships of leaf development, transpiration, and PAW compare favorably with other published results. The PAW threshold values when each process is affected would be useful in developing criteria for scheduling irrigation and in improving the accuracy of crop growth models in estimating leaf development and transpiration.
Hand‐Operated Rainout Shelter1
Authors: Bittman S. , Jan E. Z. , Simpson G. M.
Published: July 2010

Rainout shelters are used in drought studies because they provide a means of controlling the input of water. Our objective was to design a hand‐operated rainout shelter that would be inexpensive, sturdy, easy to operate, and large enough to cover a 2.1‐ by 6‐m field plot. The shelter was comprised of a stationary wood frame, a retractable cover of clear polyethylene (0.15 mm), and a tank to collect excluded water. Twelve shelters were built in 1983 and 1984. Each could be covered or uncovered by two people in 1 to 2 min. The shelters withstood winds of 6.9 m s−1, a rainfall rate of 8.8 mm in 15 min, and were effective in creating uniform water deficits for sampling areas of 4.5 m2 as indicated by growth, leaf senescence, leaf rolling, and leaf water potential. The shelters provided an artificial microclimate useful for experiments emphasizing comparisons within, rather than between, moisture regimes. Our shelters are more portable and less costly than automated units but require more labor for operation and maintenance.
Establishment Clipping of Tall Fescue and Companion Annual Ryegrass
Authors: Brede A. D. , Brede J. L.
Published: July 2010

Due to its soil stabilizing ability, annual ryegrass (Lolium multiflorum Lam.) is sometimes used as a companion crop with tall fescue (Festuca arundinacea Schreb.). Problems arise, however, because of the competitive nature of annual ryegrass. The purpose of this study was to develop a clipping treatment that could be used during turf establishment to allow annual ryegrass to effectively stabilize the soil in a mixture with tall fescue but would result in a small amount of annual ryegrass in the mature stand. Three field studies were conducted over a 3‐yr period on Kirkland silt loam (fine, mixed, thermic, Udertic Paleustoll) in central Oklahoma. In the first study, individual seedlings were clipped in a factorial arrangement of cutting heights, weeks from emergence to first clip, and clipping repetitions. Regression indicated that 22 to 50% of the variability in shoot and root growth at 60 d of age could be attributed to initial clipping treatments. In a second study, on the first day of emergence 90% of ryegrass seedlings had emerged versus 50% of the tall fescue seedlings, suggesting the potential for managing species dominance via clipping. A third study evaluated two seeding rates and seven clipping treatments (developed in the earlier experiments) on 4:l fescue/ryegrass mixture. Waiting 6 wk before initially cutting the turf favored annual ryegrass, whereas tall fescue was generally favored by a single, close clipping (0‐7 mm height) shortly after annual ryegrass emergence (0‐3 d after emergence). Initial clipping treatments reduced ryegrass ground coverage at 60 d from 82% to as little as 46%.
Cotton Main‐Stem Leaves in Relation to Vegetative Development and Yield
Authors: Oosterhuis D. M. , Urwiler M. J.
Published: July 2010

Understanding the relative contribution of specific leaves to structural growth and yield development is critical in improving the management of cotton (Gossypium hirsutum L.) crops. Studies were conducted to investigate the role of main‐stem leaves in the growth and development of field‐grown cotton. A range of leaf removal treatments was compared to a control with no leaf removal in two field trials in differing localities. Removal of main‐stem leaves as they appeared had a dramatic effect on plant growth and yield. When main‐stem leaves were removed after they had expanded there was a less severe influence on yield but still a large influence on height. Leaf removal had no significant effect on either plant height or yield if the sympodial branch was allowed to develop before the mainstem leaf was removed. Removal of monopodial branches had no effect on yield or plant height. These results indicate that main‐stem leaves are involved in the structural development of the plant necessary to provide an adequate framework with sufficient leaf area and fruiting points for optimum yields. The earlier the main‐stem leaf removal, the more drastic the resulting effect on plant growth and yield. Once the main‐stem leaves had contributed to structural development, their contribution to plant productivity appeared to diminish rapidly.
Influence of Tillage and Crop Rotation on Yields of Corn, Soybean, and Wheat
Authors: Edwards J. H. , Thurlow D. L. , Eason J. T.
Published: July 2010

Cropping systems for minimum or no tillage have been developed to produce corn (Zea mays L.) yields equal to or higher than yields obtained in conventional tillage systems, but limited research has been conducted with tillage systems involving corn and soybean [Glycine mar (L.) Merr.] rotations. The objective of this study was to compare different cropping sequences of corn, soybean, and wheat (Triticum aestivum L.) in conventional, strip, and no tillage. A field experiment was conducted on a Hartsell fine sandy loam (fine‐loamy, siliceous, thermic Typic Hapludults). In 1981, corn yields with no tillage were 30% lower than those from conventional tillage systems. No corn yield differences were observed in 1982 and 1984 due to tillage or crop rotation; however, in 1983, strip and no tillage in conjunction with soybean in the rotation increased corn grain yields by 12%. Soybean yields in strip and no tillage decreased 16% compared to conventional tillage yields in 1981, but in subsequent years, soybean yields increased with those systems. A significant tillage × rotation interaction in 1981, 1982, and 1983 was caused primarily by a buildup of soybean cyst nematode (Heterodera glycines Ichinohe) (SCN) population with conventional tillage and continuous soybean. Rainfall affected soybean yields more with conventional tillage than with strip or no tillage. The conservation tillage systems (strip or no‐tillage system) in combination with corn‐soybean rotation for both full‐season or double‐cropped soybean gave the most consistent yield increase for the 4 yr.
Seedbed Tillage and Irrigation Effects on Yield of Mono‐ and Doublecrop Soybean and Wheat on a Silt Loam
Authors: Wesley R. A. , Heatherly L. G. , Pringle H. C. , Tupper G. R.
Published: July 2010

Doublecropping soybean [Glycine max (L.) Merr.] and wheat (Triticum aestivum L.) is an accepted cropping system in the Midsouth. Soybean is either planted after wheat with subsoiling or disking and harrowing, or both, to prepare a seedbed, or is seeded directly into the wheat stubble. The objective of this study was to determine the yield response of ‘Forrest’ soybean (Maturity Group V) when planted in a conventional monocrop system and in conventional and no‐till doublecrop systems following wheat. The three cropping systems were evaluated in both an irrigated and nonirrigated environment on a Dundee silt loam (fine‐silty, mixed, thermic Aerie Ochraqualf), making a total of six treatments. The six treatments were arranged in a randomized complete‐block design with four replicates, and remained in the same location for the duration of the 3‐yr study. Soybean was planted at a rate of 44 kg ha−1 in rows 1 m apart, whereas wheat was drill‐seeded at a rate of 101 kg ha−1 in rows 0.18 m apart. Average wheat yields for the four doublecrop treatments were not significantly different within or across years. The 3‐yr average was 3475 kg ha−1. Irrigated monocrop soybean produced the highest average yield of 3165 kg ha−1, whereas nonirrigated monocrop soybean and the irrigated doublecrop soybean with either no seedbed tillage or conventional seedbed tillage averaged 2491,2596, and 2740 kg ha−1, respectively, and were statistically similar. Yields from the nonirrigated doublecrop soybean with no‐till and conventional seedbed tillage were the lowest and averaged 1940 and 1909 kg ha−1, respectively. Soybean yields from all treatments in both the irrigated and nonirrigated environments decreased in a nearly linear fashion from 1984 to 1986. This was largely due to a decline in the number of seed produced, and was apparently caused by higher maximumminimum temperatures during the R1 to R5 growth periods as the experiment progressed in time.
Statistical Analysis of a Yield Trial
Authors: Zobel Richard W. , Wright Madison J. , Gauch Hugh G.
Published: July 2010

Yield trials frequently have both significant main effects and a significant genotype X environment (GE) interaction. Traditional statistical analyses are not always effective with this data structure: the usual analysis of variance (ANOVA), having a merely additive model, identifies the GE interaction as a source but does not analyze it; principal components analysis (PCA), on the other hand is a multiplicative model and hence contains no sources for additive genotype or environment main effects; and linear regression (LR) analysis is able to effectively analyze interaction terms only where the pattern fits a specific regression model. The consequence of fitting inappropriate statistical models to yield trial data is that the interaction may be declared nonsignificant, although a more appropriate analysis would find agronomically important and statistically significant patterns in the interaction. Therefore, agronomists and plant breeders may fail to perceive important interaction effects. This paper compares the above three traditional models with the additive main effects and multiplicative interaction (AMMI) Model, in an analysis of a soybean [Glycine max (L.) Merr.] yield trial. ANOVA fails to detect a significant interaction component, PCA fails to identify and separate the significant genotype and environment main effects, and LR accounts for only a small portion of the interaction sum of squares. On the other hand, AMMI analysis reveals a highly significant interaction component that has clear agronomic meaning. Since ANOVA, PCA, and LR are sub‐cases of the more complete AMMI model, AMMI offers a more appropriate first statistical analysis of yield trials that may have a genotype X environment interaction. AMMI analysis can then be used to diagnose whether or not a specific sub‐case provides a more appropriate analysis. AMMI has no specific experimental design requirements, except for a two‐way data structure.
Ammonia Volatilization from Spring Wheat Plants
Authors: Parton W. J. , Morgan J. A. , Altenhofen J. M. , Harper L. A.
Published: July 2010

Plant shoots may be a significant source of N loss in crops. Ammonia volatilization and CO2 exchange rates from ‘Olaf’ spring wheat (Triticum aestivum L.) plants exposed to low‐ and high‐N treatments were observed from heading through the hard kernel phenological stages. The plants were grown in growth chambers (Nunn clay loam soil [Aridic Argiustoll]) where whole‐plant gas‐exchange measurements were made using a plexiglass cuvette. Plants lost NH3 at fairly constant rates (60–120 ng NH3–N m−2 s−1) during the pre‐senescence time period (before milk ripe stage), but the loss rate increased to 200 to 300 ng NH3 m−2 s−1 during final plant senescence. A reverse pattern was observed in CO2 exchange rates. Rates of CO2 exchange ranged from 0.13 to 0.42 mg CO2 s−1 during heading, but dropped off (gradually in the high‐N treatment, abruptly in the low‐N treatment) as the plants began to senesce. The NH3 loss rates on a leaf‐area basis were similar for the low‐ and high‐N plants despite significantly higher N concentrations in high‐N plants. Twice the leaf area was attained by the high‐N plants, resulting in NH3 volatilization rates per plant roughly twice those observed in the low‐N plants. The results suggest that significant amounts of NH3 can be lost from wheat shoots.
Soybean Phosphorus and Potassium Deficiency Detection as Influenced by Plant Growth Stage
Authors: Hallmark W. B. , DeMooy C. J. , Mooris H. F. , Pesek John , Shao K. P. , Fontenot J. D.
Published: July 2010

Recent data suggests that ignoring the effect of physiological age on nutrient status of soybean (Glycine max L.) can result in biased P, K, and Zn deficiency diagnoses by the diagnosis and recommendation integrated system (DRIS). To overcome this problem, the use of nutrient multiples in place of some nutrient ratios for calculating nutrient function values has been advocated. Also, accurate P, Mn, and Zn deficiency diagnoses have been made using a small R1 (initial‐bloom) DRIS data base. This study was conducted to determine: (i) if small R1 and R5 (initial pod‐fill) DRIS data bases can detect soybean P and K deficiencies from R2 (full‐bloom) plants, and (ii) if the use of nutrient multiples in the R5 data base improves P and K diagnoses. The R1 data base detected P and K deficiencies, but overemphasized P and underemphasized K diagnoses. The R5 data base overemphasized Ca and N and underemphasized P and K diagnoses. Differences in diagnoses were attributed to high ca (data base concentrations are expressed in lower‐case letters) and low p values in the R5 versus the R1 data base. To alleviate incorrect P diagnoses nutrient multiples involving ca were substituted for nutrient ratios of ca in the R5 data base. This improved (P<0.01) P diagnoses; however, diagnoses were not as accurate (P<0.l0) as P diagnoses by the Rl data base. These data indicate that the use of nutrient multiples in DRIS can improve nutrient diagnoses, but that more accurate predictions occur when plants are sampled at the same growth stage as the data base.
Supplemental Radiation Effects on Senescence, Plant Nutrients, and Yield of Field‐Grown Corn
Authors: Ottman M.J. , Welch L. F.
Published: July 2010

The lower leaves in a fully developed corn (Zea mays L.) canopy are heavily shaded at normal stand densities. The low photosynthetic photon flux density (PPFD) received by such leaves may initiate senescence, hinder nutrient uptake by roots, and limit crop productivity. Objectives of this study were to determine the influence of supplemental radiation within the canopy on leaf senescence, plant nutrient accumulation, and yield of corn in a high‐yielding environment. Fluorescent lamps were placed in the lower two‐thirds of a corn canopy in an irrigated field study conducted near Urbana, IL, on a Drummer silty clay loam (fine‐silty, mixed, mesic Typic Haplaquoll). Supplemental PPFD provided by the lamp banks varied from 0 to 42 and 0 to 121 μmol m−2 s−1 on a leaf surface basis in 1982 and 1983, respectively. Supplemental PPFD delayed leaf senescence, increased the carbohydrate status of the plant, and increased aerial N, P, and K accumulation by 90, 90, and 30%, respectively. A 54% increase in dry matter and a 36% increase in N and P concentration accounted for increased N and P accumulation, while increased K was accounted for by a 54% increase in dry matter and a 24% decrease in K concentration. Grain yield increased proportionally to supplemental PPFD, from approximately 10.6 to 16.3 Mg ha−1, while harvest index decreased slightly. Yield was associated with increases in weight per kernel, kernels per ear, and ears per plant of 11,14, and 25%, respectively. Knowledge and enhancement of factors controlling corn yield may lead to future reductions in the unit cost of corn production.
Sources and Timing of Spring Topdress Nitrogen on Winter Wheal in Idaho
Authors: Lutcher L. K. , Mahler R. L.
Published: July 2010

Fall‐applied N is poorly utilized by winter wheat (Triticum aestivum L.) in northern Idaho, because heavy winter precipitation leaches much of the N from the root zone. Nitrogen‐use efficiency can be improved by spring application. This study evaluates two N fertilizer sources, urea‐ammonium nitrate solution (UAN; 32% N) and prilled ammonium nitrate (AN; 34% N), as spring topdress materials and determines the growth stage at which N application would produce maximum yield. Four field studies were established on cropland initially containing less than 50 kg NO3−N ha−1. Winter wheat was seeded at 90 kg ha−1 at each site. Nitrogen was topdressed at 100 kg ha−1 in the spring as either UAN, AN, or a UAN‐bromoxynil/MCPA [3,5‐dibromo‐4‐hydroxybenzonitrile/(4‐chloro‐2‐methylphenoxy) acetic acid] tank mix at eight different growth stages. Parameters evaluated included: (i) leaf burn, (ii) stand vigor, (iii) tillering, (iv) weed control, and (v) yield. Temporary yellowing of plant leaves was noted following UAN applications at air temperatures > 14°C. The degree of yellowing or leaf burn exhibited a significant curvilinear correlation with air temperature (R2=0.89). Nitrogen application date affected stand vigor, tillering, weed control, and yield, with the best ratings occurring with N applications before Zadoks' growth stage 31. When study sites and N sources were pooled, yields were 5.4,4.9, 4.8, 4.6, 4.3, 4.1, 3.6, and 3.1 Mg ha−1 for wheat fertilized at growth stages 22,24,26,28,31,32,37, and 43, respectively. Significant N source X time of application interactions for winter wheat yield were observed at three study sites. At early N application dates (growth stages) yield differences attributable to AN or UAN were not observed; however, when N was applied after growth stage 31, UAN plots produced yields between 1 and 24% (average 6%) greater than AN‐fertilized plots. This was attributable to dry soil conditions that reduced AN movement into the soil plant‐root zone, coupled with foliar absorbtion of UAN by wheat plants.
Estimation of Acremonium Coenophialum Mycelium in Infected Tall Fescue
Authors: Roberts C. A. , Barton F. E. , Moore K. J.
Published: July 2010

Current methods for assessing the infection level in tall fescue (Festuca arundinacea Schreb.) infected with the fungal endophyte, Acremonium coenophialum Morgan‐Jones & Gams, do not quantify mycelial dry matter. The objective of this study was the estimation of mycelium by chemical and spectral determination of chitin, a fungal cell wall polymer. Tall fescue samples with various proportions of infected plants were collected from paddocks established on a Cecil sandy loam (clayey, kaolinitic, thermic Typic Hapludult) soil. Samples were analyzed for chitin, and the chemical data were used to develop a spectral prediction equation using near infrared spectroscopy (NIRS). The calibration and validation coefficients of determination were 0.86 and 0.84, respectively. The validated equation was used in the prediction of chitin in 95 other samples collected from paddocks microscopically evaluated for percent infected plants, and microscopic data were regressed against predicted chitin. Percent infection, as predicted by the microscopic procedure, and chitin concentration were not correlated (P > 0.05). The NIRS calibration set was expanded to include samples collected in Illinois. The improved equation accounted for 91 and 89% of the variability in calibration and validation, respectively. The mean and standard error of calibration were 328 and 50 mg kg−1 dry matter (DM), respectively. The expanded equation was used to quantify chitin from spring and fall pastures in Illinois that contained 100% infected plants. Chitin in spring pastures ranged from 118 to 961 mg kg−1 DM and varied greatly. Fall chitin varied little and the maximum concentration was 596 mg kg−1 DM. We concluded that endophytic chitin in tall fescue could be quantified chemically and spectrally. If potential sources of error are accounted for, these procedures can be used to estimate relative A. coenophialum mycelium.
Compatibility of Five White Clover and Five Tall Fescue Cultivars Grown in Association
Authors: Pederson G. A. , Brink G. E.
Published: July 2010

The need for tall fescue (Festuca arundinacea Schreb.) pasture renovation due to a fungal endophyte (Acremonium coenophialum Morgan‐Jones and Gams) that causes fescue toxicosis in grazing cattle (Bos taurus L.) has given farmers the opportunity to add white clover (Trifolium repens L.) to their improved pastures. This study was conducted to determine the compatibility of five white clover and five tall fescue cultivars grown in association during two seeding years and to determine any interactions between cultivars. ‘Regal’, ‘Tillman’, ‘Louisiana S‐1’, ‘Osceola’, and MS Brown Loam Syn. #6 white clover were grown in all combinations with ‘Kentucky 31’, ‘Kenhy’, ‘Johnstone’, ‘Triumph’, and ‘Missouri 96’ tall fescue in two separate seeding year studies. The studies were grown on a Catalpa silty clay (fine, montmorillonitic, thermic Fluvaquentic Hapludoll) at Mississippi State, MS. Louisiana S‐1 associations produced significantly less total dry matter (DM) and white clover (WC) yield and more tall fescue (TF) yield than those of the other white clover cultivars across tall fescue cultivars. Triumph associations produced significantly less WC yield and more TF yield than those of the other tall fescue cultivars across white clover cultivars. No differences in total DM yield were observed for the tall fescue cultivars. No interactions between tall fescue and white clover cultivars were found in either seeding year. The cultivar relationships were constant over years an over harvests within years, though the botanical composition of the plots varied between harvests and years. Triumph was more competitive with white clover than the other tall fescue cultivars, and Louisiana S‐1 was less competitive with tall fescue than the other white clover cultivars during the seeding year. No advantage was found for any specific combination of white clover and tall fescue cultivars during the seeding year.
Corn Root Growth and Nitrogen Uptake as Affected by Ammonium Placement
Authors: Anghinoni I. , Barber S. A.
Published: July 2010

Stimulation of root growth in the N‐fertilized soil volume of placed N fertilizer has been observed, but no quantitative data are available. The objective of this research was to obtain quantitative data on the influence of the fractional soil volume fertilized with NH+4 on corn (Zea mays L.) root distribution between NH+4‐fertilized and unfertilized soil, and to determine the effect of N placement on N uptake and plant growth. A pot experiment with seven treatments and three replicates was conducted using Raub silt loam (fine silty, mixed, mesic Aquic Argiudolls). The treatments were six volume fractions of 1.00, 0.50, 0.20, 0.10, 0.05, and 0.02 of soil fertilized with NH+4 plus a no‐N treatment. Before use, the soil was leached to remove NO−3 and a nitrification inhibitor was added. The NH+4 rate was 90 mg N kg−1 of soil in the pot. Six‐day‐old corn plants were transplanted into pots with 3 kg of soil and grown for 14 d, and into pots with 15 kg of soil and grown for 40 d. Corn was grown for 14 d with all treatments and for 40 d with the 0.2 placement. Root length density (km m −3) was greater in the NH+4‐fertilized soil. Root distribution between the NH+4‐fertilized and unfertilized soil volumes, the same at 14 d and 40 d, can be described by the equation y = x0.70 (r2=0.99), where y is the fraction of total root length in the NH+4 ‐fertilized soil when NH+4 is mixed with x fraction of the soil. The effect of NH+4 on root distribution was similar to that observed in earlier studies with P. Shoot N concentration was not affected by NH+4 placement; however, plant weight and N uptake were less with the 0.5 and 0.2 placement treatments.