bluuebunny/crossref_metadata_2025 huggingface dataset:
Fall Management Effects on ‘Grasslands Matua’ Prairie Grass Production and Sward Characteristics
Authors: Jung Gerald A. , Shaffer John A. , Everhart John R.
Published: July 2010

Ruminant animal production costs in the northeastern USA can be lowered by extending the fall grazing season. Two field experiments were initiated with prairie grass [Bromus unioloides (Willd.) H.B.K. cv. Grasslands Matua; syn. B. willdenowii Kunth] to determine effects of fall management (i.e., clipping) on forage production and winter survival. Plantings were made in May 1986 for Exp. 1 and June 1990 for Exp. 2. Experiment 1 addressed date of fall harvest and residual stubble height effects on fall yields and tiller density, winter survival, and spring yields and tiller density. Experiment 2 addressed the interaction of harvest frequency and residual stubble height on the same parameters as for Exp. 1. Fall yields of Matua peaked at 4.0 Mg ha−1 in late October to early November (Exp. 1 and 2). Mean fall yields were reduced 20, 40, and 60% as residual stubble height was increased from 7.5 cm to 12.5, 20.0, or 25.0 cm, respectively (Exp. 1). Spring yields were high from plots clipped to a 7.5‐cm stubble in September and decreased as fall harvest was delayed to November (Exp. 1). Spring yields from plots clipped to a 7.5‐cm stubble in late November were only 20 to 25% of yields from plots clipped in September. Leaving a higher residual stubble in fall compensated considerably for the deleterious effect of harvesting in late fall. Clipping to a 20.0‐, 12.5‐ or 7.5‐cm stubble in fall resulted in linear decreases in spring yields as fall harvest was delayed from September to November, and clipping to 25.0 cm gave a quadratic response, with a peak at mid‐October. Matua plots that were harvested once in late fall or not at all (check) recovered very slowly in spring and had a lower yield potential than plots that had been harvested two, three, or four times in fall. To optimize production of Matua in fall and spring it is recommended that one summer rest period be extended to allow natural reseeding and that two or three fall harvests or grazings be taken to increase stand density and winter survival.
Use of a Chlorophyll Meter at the Early Dent Stage of Corn to Evaluate Nitrogen Sufficiency
Authors: Piekielek William P. , Fox Richard H. , Toth John D. , Macneal Kirsten E.
Published: July 2010

A late‐season chlorophyll meter test for corn (Zea mays L.) could provide growers with a convenient evaluation of that year's N management program, along with information useful for N fertilizer rate decisions in subsequent growing seasons. Chlorophyll meter (SPAD 502) readings were taken late in the growing season on corn ear leaves in replicated plots of 357 N treatments from 93 N‐response experiments conducted in Pennsylvania. At sites not affected by severe late‐season drought or disease, chlorophyll meter readings taken at the 1/4 milk line stage separated N‐deficient from N‐sufficient treatments with 93% accuracy using a critical level of 52.0 SPAD units. If meter readings were normalized at each site by comparison with a site‐specific high‐N reference reading, chlorophyll meter readings of ear leaves made from the late milk to the middent stage of corn could separate N‐deficient from N‐sufficient treatments with 92% accuracy using a relative SPAD reading critical level of 0.93. For treatments with meter readings below the critical level, relative grain yields and the additional N that would have been needed for economic optimum grain yield were correlated with chlorophyll meter test values. For treatments with a meter reading above 52.0 SPAD units, the amount of excess N that may have been applied could not be accurately predicted. For corn tested at the 1/4 milk line stage, we suggest an N‐sufficiency range of 52.0 to 56.0 SPAD units, above which there is a 70% probability of an excess of >50 kg N ha−1 having been applied.
Estimation of Leaf Area Index for Cotton Canopies Using the LI‐COR LAI‐2000 Plant Canopy Analyzer
Authors: Hicks Stanley K. , Lascano Robert J.
Published: July 2010

Measurement of leaf area index (LAI) is useful for understanding cotton (Gossypium hirsutum L.) growth, water use, and canopy light interception. Destructive measurement is time consuming and labor intensive. Our objective was to evaluate sampling procedures using the Li‐Cor (Lincoln, NE) LAI 2000 plant canopy analyzer (PCA) for nondestructive estimation of cotton LAI on the southern High Plains of Texas. We evaluated shading as a way to allow PCA measurements in direct sunlight and the influence of solar direction when using this procedure. We also evaluated a test of canopy homogeneity (information required for setting PCA field of view), determined the number of belowcanopy measurements required, examined the influence of leaf wilting on PCA LAI determinations, and tested an alternative method (masking the sensor's two outer rings) for calculating LAI from PCA measurements. The best agreement between PCA and destructively measured LAI values was obtained when PCA observations were made either during uniformly overcast conditions or around solar noon using the shading method. Heterogeneous canopies with large gaps between rows required both a restricted (45°) azimuthal field of view and averaging the LAI values for two transects, made with the field of view parallel and then perpendicular to the row direction. This method agreed well (r2 = 0.84) with destructively measured LAI in the range of 0.5 to 3.5 and did not deviate from a 1:1 relationship. The PCA underestimated LAI by ≥ 20% when measurements were made on canopies wilted due to water stress. Masking the PCA sensor's outer rings did not improve the relationship between estimated and measured LAI in the range of LAI sampled.
Effect of Nitrogen Supply on Maize Yield: II. Field and Model Analysis
Authors: Muchow Russell C. , Sinclair Thomas R.
Published: July 2010

Experiments investigating the yield response of maize (Zea mays L.) to applications of fertilizer N are generally analyzed empirically. While the nature of the yield response can be characterized, information on the effects of various components influencing the soil and crop N budgets are unresolved. The objective of this study was to examine the results of a series of N fertility experiments with the aid of a mechanistically based crop model. The experiments resulted in grain yields ranging from 99 to 1102 g m−2, and these yields were well simulated by the model (r2 = 0.97). Under high fertility conditions, temperature and solar radiation interception explained the variation in yield among environments. Under low fertility conditions, mineralization of soil organic N was especially important in explaining yield variations among environments. Management practices preceding the experimental crops were hypothesized to have large effects on the N availability in the soil, and consequently influence observed and simulated yields. Sensitivity tests confirmed the importance of defining the initial soil organic N levels in simulating crop growth and yield when there is little or no applied N fertilizer.
Degradation by Ficin of Protein from Alfalfa Hay Conserved as Conventional and Laboratory‐Scale Bales
Authors: Coblentz Wayne K. , Fritz John O. , Bolsen Keith K. , Skinner Daniel Z. , Cochran Robert C.
Published: July 2010

Ficin was utilized in a 2‐h in vitro incubation procedure to characterize the partitioning of N into fractions based on resistance of alfalfa (Medicago sativa L.) proteins to enzymatic degradation. Objectives included evaluation of the following treatment effects on N partitioning: (i) moisture content; (ii) laboratory bale density; (iii) laboratory baling without heating during storage; (iv) spontaneous heating in laboratory bales; and (v) conventional baling. Alfalfa at three moisture levels (268, 229, and 185 g kg−1) was conserved in the following bale types: (i) conventional bales; (ii) laboratory bales made at 1.0, 1.3, 1.7, and 2.0 times the density of conventional bales and incubated in two environments (straw stacks or insulated boxes); or (iii) a prestorage control. Significant (P ≤ 0.05) moisture ✕ bale type interactions were observed for most N fractions, indicating N partitioning among bale types was greatly changed in high‐moisture hay, but remained relatively stable in dry hay. Except for the Pool‐C N fraction, which includes Maillard reaction products, laboratory‐bale density generally had little effect on N partitioning. At the medium and low moisture levels, prestorage controls had more Pool‐A N (greater buffer solubility) than did nonheated laboratory bales. Heating in laboratory bales facilitated additional significant change in N fractions, relative to nonheated laboratory bales. While Maillard reaction products increased in response to laboratory bale density, large increases in the portion of potentially available N most resistant to enzymatic degradation (B2 subfraction), appeared dependent on large heat increments incurred specifically in conventional bales.
Maize Nodal Root Response to Soil Ridging and Three Tillage Systems
Authors: Thomas Andrew L. , Kaspar Thomas C.
Published: July 2010

A greater understanding of maize (Zea mays L.) nodal root response to soil ridging and tillage systems is needed to maximize the benefits of ridge‐till and other conservation tillage systems. Field (1992 and 1993 near Marshalltown, IA) and greenhouse (two studies with two trials each) experiments were conducted to examine the effect of soil ridging, height of ridging, and three tillage systems (no‐till, ridge‐till, and chisel‐plow) on the number and stem node position of maize nodal roots and on internode length. Field plants were ridged during cultivation. In the greenhouse, ridging was simulated by using polyvinyl chloride rings to hold soil around the base of plants. Numbers of nodal roots, numbers of nodes developing functional roots, internode lengths, shoot dry weights, and grain yields (field study) were determined. In one greenhouse experiment, unridged plants developed an average of 38.4 functional nodal roots, while ridged plants developed 50.0, an increase of 30%. In the same greenhouse experiment, ridging significantly increased lengths of Internodes 6 and 7, which were covered with soil during ridging. Average length of Internode 7 increased from 64 mm to 101 mm with ridging. Increasing ridge height increased internode length and number of nodal roots in the controlled greenhouse experiments, but not in the field. In field experiments, ridge‐till caused development of significantly more functional nodal roots as compared with no‐till (1992 and 1993) and chisel‐plow (1992). Plants from no‐tiil developed 53.1 and 46.0 functional nodal roots in 1992 and 1993, respectively, while plants from ridgetill developed 58.7 and 49.1 roots. Shoot dry weight and grain yield were not affected by ridging or tillage treatments in the greenhouse or field.
Crop Sequence Effects on Response of Corn and Soil Inorganic Nitrogen to Fertilizer and Manure Nitrogen
Authors: Lory John A. , Randall Gyles W. , Russelle Michael P.
Published: July 2010

Fertilizer N and manure frequently are applied to corn (Zea mays L.) grown after alfalfa (Medicago sativa L.) at rates similar to those applied to continuous corn, although corn following alfalfa typically requires little additional N to attain maximum dry matter. Consequently, similar amounts of applied N may affect soil NO3 differently in rotational than in continuous corn. There is little information evaluating crop sequence effects on residual soil NO3 derived from fertilizer N and manure. In two 2‐yr experiments at two locations in Minnesota, we evaluated the effect of crop sequence on response of corn grain dry matter, grain N, and stover N, and of soil inorganic N (NO3‐N and NH4‐N) to fertilizer N and dairy manure. Grain dry matter of first‐year corn following alfalfa did not respond to applied N at Rosemount and typically was less responsive than continuous corn at Waseca. Crop sequence effects on soil NO3 response to manure and fertilizer N were similar. Preplant fertilizer N application of 157 kg ha−1 increased residual soil NO3‐N the following spring an average of 45 kg ha−1 more in first‐year corn following alfalfa than in continuous corn, except when excessive precipitation caused apparent high losses of applied N. Grain N content and soil NO3 responded similarly to fertilizer N in both second‐year corn following alfalfa and continuous corn. Efforts to reduce the buildup and potential loss of soil NO3 in the corn portion of alfalfa‐corn rotations should focus on reducing N application to first‐year corn following alfalfa. These N applications have little agronomic value and can dramatically increase residual soil NO3.
Assessing Cultivar Adaptability by Multiple Comparison with the Best
Authors: Piepho Hans‐Peter
Published: July 2010

Regional yield trials are conducted to identify cultivars that are well adapted to specific environments. This note proposes application of a multiple comparison procedure for assessing cultivar adaptability. A cultivar is regarded as adapted if it does not differ from the best by more than some prespecifled amount. The procedure assigns cultivars to one of three groups: (i) adapted; (ii) unadapted; and (iii) unclassified. The classification is based on simultaneous confidence intervals for the difference between all cultivars and the best cultivar. Such classification may be a useful tool for cultivar recommendations.
Fluridone Reveals Root Elongation Differences among Alfalfa Germplasms
Authors: Meyers Lynda L. , Russelle Michael P. , Lamb JoAnn F. S.
Published: July 2010

Alfalfa (Medicago sativa L.) is a deep‐rooted perennial that may be able to remove nitrate from subsoil beneath the rooting zone of annual crops. Alfalfa cultivars with rapid and deep root elongation would be beneficial for reducing future nitrate contamination of ground water supplies. The objectives of this research were to (i) develop a protocol using the herbicide fluridone {1‐methyl‐3‐phenyl‐5‐[3‐(trifluromethyl) penyl]‐4(1H)‐pyridinone} as a marker for indicating alfalfa root penetration in soil, and (ii) determine the variability in rate of geotropic root elongation within and among diverse alfalfa germplasms. Fluridone caused rapid, distinctive bleaching of alfalfa leaves at a rate of 25 mg a.i. kg−1 soil, without being fatal. When transplanted after onset of fluridone symptoms, alfalfa recovered and resumed normal growth and flowering. Alfalfa populations did not differ in sensitivity to fluridone. Decomposition of roots from a fluridone‐treated plant did not cause symptom development in other plants. Individual plants within alfalfa germplasms differed by 56 d in onset of symptoms, indicating a similar difference in root activity at 80 cm depth in soil. Mean geotropic root elongation rate for 12 diverse germplasms ranged from 1.12 to 1.40 cm d−1. Populations selected for unique root morphological traits were significantly faster in geotropic root elongation rate than their nonselected parental populations. Our method permits in situ identification of plants with rapid geotropic root elongation rates within heterogeneous populations and has proven useful in germplasm selection.
Cropping Systems for Perennial Ryegrass Seed Production: I. Minimum Tillage Establishment of Rotation Crops in Stubble Without Burning
Authors: Young William C. , Youngberg Harold W.
Published: July 2010

Viability of alternative crops in a monoculture grass seed cropping system will be enhanced if minimum tillage establishment through grass seed stubble is successful without burning. Our objective was to compare agronomic performances of red clover (Trifolium pratense L.), white clover (T. repens L.), meadowfoam (Limnanthes alba L.), and pea (Pisum sativum L.) when drill‐seeded in the stubble of a third‐year perennial ryegrass (Lolium perenne L.) seed crop, with and without burning stubble. Four field experiments were conducted during a 6‐yr period on a Woodburn silt‐loam (fine‐silty, mixed, mesic Aquultic Argixerolls) soil in western Oregon. Ryegrass stubble was either propane‐burned or was not burned before drill‐seeding the rotational crops. In one experiment, a rotary strip‐till drill was also compared with a no‐till drill for establishing white clover in perennial ryegrass stubble. Burning the stubble enhanced spring growth of red clover; however, forage and seed yields in the first crop year were 47 and 66% higher, respectively, for the nonburned than the burned treatments. There were no differences among treatments for forage and seed yields of red clover in the second crop year. Treatments did not affect dry matter or seed production of white clover and spring pea. Meadowfoam forage and seed yields were 26 and 24% lower, respectively, for the nonburned than the burned treatments. We concluded that burning stubble before seeding may be advantageous for winter annual seed crops that mature during the spring or early summer months. However, burning stubble is not beneficial, or may be disadvantageous, for crops that mature during the late summer in areas such as Oregon with a Mediterranean climate. The no‐till drill was superior to the strip‐till drill for establishing white clover in perennial ryegrass stubble regardless of stubble management method.
Seeding Rate Effects on Rough Rice Yield, Head Rice, and Total Milled Rice
Authors: Gravois Kenneth A. , Helms Ronnie S.
Published: July 2010

Without an adequate and uniform rice (Oryza sativa L.) stand, optimum rough rice yields are difficult to attain. Most seeding rate research has emphasized optimizing rough rice yields, with little consideration given to the effect of seeding rate on head rice (percentage of whole milled kernels) and total milled rice (percentage of whole milled kernels plus milled broken kernels). Thus, our objective was to assess the effect of seeding rate on head rice and total milled rice of two very early‐season rice cultivars (Millie and Adair) and two midseason rice cultivars (Katy and Kaybonnet). The experiment was conducted at the Pine Tree Experiment Station near Colt, AR, during 1992 and 1993. The cultivar (maturity group) × seeding rate interaction was significant for head rice and total milled rice, suggesting that, for head rice and total milled rice, the four cultivars responded differently to seeding rate. There was a linear decrease in head rice as seeding rate decreased for Millie, a quadratic decrease in head rice as seeding rate decreased for Adair, and a linear increase in head rice as seeding rate decreased for both Katy and Kaybonnet. We surmise that increased tillering and decreased kernel weights at the lower seeding rates decreased the head rice for Adair and Millie. Total milled rice decreased linearly with decreasing seeding rate only for Adair. When evaluating thin rice stands for potential performance or replanting, both cultivar and head rice and total milled rice losses should be considered.
A Dual‐Heater Gauge for Measuring Sap Flow with an Improved Heat‐Balance Method
Authors: Peressotti Alessandro , Ham Jay M.
Published: July 2010

abstract

Measurements of sap flow in intact plant stems help quantify biophysical relationships governing water transport in the soil‐crop‐atmosphere continuum. Research was conducted to develop and test a dual‐heater sap flow gauge based on an improved heat‐balance theory. The dualheater gauge contains two resistance heaters that, when operated in variable power mode, allow mathematical manipulation of the heat balances, so no empirical calibration or zero set is necessary (i.e., no gauge factor). Prototype dual‐heater gauges were fabricated and tested on containergrown corn (Zea mays L.) with stem diameters between 25 and 30 mm. Traditional single‐heater heat‐balance gauges were also built and tested to compare the two designs. Gauges were tested simultaneously in a greenhouse over a continuous 5‐d drying cycle when flows ranged from 0 to 140 g h−1 and daily water use ranged from 137 to 1064 g d−1. Both gauge types measured hourly sap flow to within ± 10% relative to gravimetric estimates of transpiration. The dual‐ and single‐heater gauges measured cumulative sap flow over the 5‐d test period to within 4.0 and 9.5%, respectively. The largest errors in daily sap flow, 34%, occurred in the single‐heater gauge when the plants were subjected to water stress. The dual‐heater approach could measure sap flow without predetermined or empirically derived calibration factors or zero sets. Accurate measurements of sap flow were obtained 15 min after the gauge was attached to the plant stem. Additionally, the dual‐heater gauge was easier to build, consumed less power, and caused less stem heating than the single‐heater gauge.
MODWht3: A Development‐Driven Wheat Growth Simulation
Authors: Rickman Ronald W. , Waldman Sue E. , Klepper Betty
Published: July 2010

Crop growth simulations are needed to help organize our knowledge of plant response to the environment for the purpose of assisting growers in management decisions, predicting impacts of land use decisions, and predicting the consequences of probable climatic variation. This paper describes the derivation, combination, and (where necessary) calibration of the models required to produce a simulation of the seasonal development and growth of winter wheat. The simulation provides appearance time and size estimates for each aboveground plant part (leaves, stems, spikes, and kernels), length and mass of roots with depth, time of occurrence of phenological events (germination, emergence, tillering, single ridge, double ridge, jointing, boot, heading, anthesis, soft dough, mature, and harvest ripe), rate and amount of water evaporated and transpired, uptake of N from the soil profile, and estimates of daily net photosynthesis. Strengths of the simulation include that it predicts dates for all crop phenological stages, it estimates sizes for all plant parts on a daily basis for comparisons with almost any observed field data, it is organized according to the natural structure of the system being simulated, and it is designed to be changed. Weaknesses include current lack of ranges for parameter values for different cultivars, a simplistic soil water budget, and limitations in specifying nutrient distribution among plant organs. No weed, pathogen, or insect models are incorporated; however, the program that implements the simulation is specifically designed to be easily modified, so pest models could be added.
Row Spacing Effects on Light Extinction Coefficients of Corn, Sorghum, Soybean, and Sunflower
Authors: Flénet Francis , Kiniry James R. , Board James E. , Westgate Mark E. , Reicosky Donald C.
Published: July 2010

In many crop models, light intercepted by a canopy (IPAR) is calculated from a Beer's Law equation: IPAR = PAR × [1 − exp(−k × LAI)], where k is the extinction coefficient, PAR the photosynthetically active radiation, and LAI the leaf area index. The first objective of this study was to investigate the effect of row spacing on k for corn (Zea mays L.), sorghum [Sorghum bicolor (L.) Moench], soybean [Glycine max (L.) Merr.], and sunflower (Helianthus annuus L.) to provide information for modeling. Data from literature and from an experiment conducted at Temple, TX, were evaluated. The second objective was to investigate effects of time of day and stage of crop development on k for different row spacings. Seeds of all four species were sown in rows 0.35, 0.66, or 1.00 m apart. Measurements of canopy light interception were taken near solar noon on two dates before anthesis. At anthesis, extinction coefficients were determined at 0845, 1015, and 1145 h (solar time). The extinction coefficient showed a linear decrease as row spacing increased. For each crop, the effect of row spacing on k was described by one linear regression for most data. Stage of crop development and stage of development × row spacing interaction did not significantly affect k during the period of measurements. The effect of time of day was significant for all four crops, and the time of day × row spacing interaction was significant for soybean and sunflower. Thus, modeling light interception for different row spacings should account for these effects.
Canopy Management Influences on Cool‐Season Grass Quality and Simulated Livestock Performance
Authors: Turner Kenneth E. , Belesky David P. , Fedders James M. , Rayburn Edward B.
Published: July 2010

Inadequate energy intake across the grazing season can be a major limitation to performance of grazing ruminants. A small‐plot experiment was conducted to determine the effect of repeated defoliation, based on canopy height and on the quantity and quality of tall fescue × perennial ryegrass (Festuca arundinacea Schreb. × Lolium perenne L.) hybrid, orchardgrass (Dactylis glomerata L.), and prairie grass (Bromus catharticus M. Vahl) in the Central Appalachian Region of the USA. Energy determined from herbage quality data was used to predict growing steer performance. Early and repeated defoliation (T50, 20‐cm canopy cut to 10‐cm residue; S50, 10‐cm canopy cut to 5‐cm residue; and T75, 20‐cm canopy cut to 5‐cm residue) of the grasses resulted in greater herbage crude protein (CP) (202, 226, and 189 g kg−1, respectively) and lower neutral detergent fiber (NDF) concentrations (591, 572, and 596 kg−1, respectively) compared with the hay management (hay harvested at early seed head emergence followed by T75 management; 152 g CP kg−1 and 620 g NDF kg−1). Cumulative metabolizable energy yield on a 1000‐ha basis tended to be highest for hay (62 138 MJ ha−1) and T75 (49 678 MJ ha−1), compared with S50 (40 373 MJ ha−1) and T50 (28 457 MJ ha−1) simply because of greater herbage mass. Greatest average daily gain was predicted when 250‐kg steers grazed T50 (0.81 kg d−1) compared with S50 (0.70 kg d−1) and T75 ( 0.71 kg d−1). Total number of grazing days per hectare was lowest for T50 (431 d), compared with S50 (580 d) and T75 (690 d). Total annual gain was greater for T75 (690 kg liveweight ha−1) management than for S50 (580 kg ha−1) or T50 (436 kg ha−1). Using herbage earlier in spring before maturation may compromise total herbage productivity, but should sustain a greater number of grazing days and livestock productivity for a given land area.
Yield Rankings for Soybean Cultivars Grown in Narrow and Wide Rows with Late Planting Dates
Authors: Board James E. , Zhang Wei , Harville Bobby G.
Published: July 2010

Cultivar selection is a major problem for late‐planted soybean [Glycine max (L.) Merr.] in the southeastern USA. Cultivar yield rankings differ between optimal and late planting dates. Thus, recommendations for late plantings are based on statewide cultivar trials at late planting dates. Because such trials are large and expensive, high‐yielding cultivars in late plantings could be more rapidly and efficiently selected through identifying morphological and developmental parameters associated with cultivar yield performance. Furthermore, consistency of yield rankings between narrow‐ and wide‐row culture within a late planting is not known. Our objectives were to (i) determine if row spacing significantly affects cultivar yield rankings at a late planting date and (ii) identify yield components, growth dynamic factors, and phenological characteristics associated with cultivar yield differences at a late planting date. Twelve commercial soybean cultivars were planted in 91‐ and 50‐cm row spacings during 1992 and 1993 on a Commerce silt loam (fine‐silty, mixed, nonacid, thermic Aerie Fluvaquents) near Baton Rouge, LA (30°N lat). No significant cultivar × row spacing interaction for yield occurred. Yield rankings for the 12 cultivars were similar between row spacings (r2 = 0.95, P < 0.0001). Cultivar yield differences were attributed largely to differences in pod number (r2 = 0.35, P < 0.0001), rather than seed per pod (r2 = ‐0.07, P < 0.0001) or seed size (NS). Among all parameters, total dry matter at R5 was most highly correlated with yield (r2 = 0.55 to 0.62, P < 0.0001) across different row spacings or within the same row spacing. In conclusion, total dry matter at R5 and other parameters associated with yield were identified, parameters that can be used to develop regression equations for predicting cultivar yield performance in late plantings.
Design, Construction, and Installation of an Intact Soil Core Lysimeter
Authors: Moyer Jeffrey W. , Saporito Louis S. , Janke Rhonda R.
Published: July 2010

An intact soil core lysimeter with its insertion device and process was developed to facilitate the collection of leachate and soil water samples from a series of field plots in eastern Pennsylvania. This design was developed to minimize disturbance of the soil within and around the lysimeter. The lysimeter was constructed of 76.2‐cm‐diam. steel well casing with a 7.9‐mm wall thickness. The casings were cut to lengths of 1.15 and 0.75 m and were inserted by means of direct downward force to a depth of 1 m. An access hole 38 cm in diameter by 161 cm deep was then augered next to the inserted casing for the installation of a collection device beneath and beside the cylinder. The soil‐filled cylinder was removed and set on a prefabricated base and welded in place. The prefabricated base had drain holes and a fitting for attachment of the collection device. The collection unit was attached and the entire lysimeter was reinserted into the cavity. Leachate caught in the collection device was removed by. pumping through attached surface tubes alongside the cylinder. This design has proved to be efficient and cost‐effective. The insertion method kept soil compaction to a minimum while maintaining a watertight seal between the casing and soil core.
Growth Dynamics during the Vegetative Period Affects Yield of Narrow‐Row, Late‐Planted Soybean
Authors: Board James E. , Harville Bobby G.
Published: July 2010

Narrow‐row culture is recommended for increasing soybean [Glycine max (L.) Merr.] yield at late plantings in the southeastern USA. Increased pod number resulting from greater light interception (LI) and crop growth rate (CGR) during the early reproductive period [first flowering to seed initiation (R1 to R5)] is mainly responsible for narrow‐row yield increases. However, little is known about rowspacing effects on Ll, CGR, and other growth dynamic parameters during the vegetative period [emergence (E) to R1] and how these parameters affect yield. Our objectives were to determine when LI and CGR differences in narrow vs. wide rows appear during E to R1, to determine if these differences contribute to narrow‐row effects on CGR(R1 to R5), and to determine the roles of leaf area index (LAI) and light interception efficiency (LIE = LI/LAI) in causing narrow‐row LI increases during the vegetative period. Seed of ‘Centennial’ soybean (Maturity Group VI) was planted in mid‐July in 1992 and 1993 at Baton Rouge, LA, on a Commerce silt loam soil (fine‐silty, mixed, nonacid, thermic Aeric Fluvaquent). Experimental design was a randomized complete block in a split‐plot arrangement. Main plots were row spacings of 100, 50, and 25 cm. Split plots were eight sampling dates during E to R5. The CGR(R1 to R5) advantage of narrow‐row culture developed from CGR advantage in the vegetative period, caused by greater LI originating from increased LIE during the first 26 d of the vegetative period. Yield was significantly correlated with CGR during most of the vegetative period. In conclusion, source strength (CGR) during the vegetative period was shown to affect yield at late planting dates.
Row Spacing and Nitrogen: Effect on Alfalfa‐Bermudagrass Quality Components
Authors: Stringer William C. , Morton Benjamin C. , Pinkerton Bruce W.
Published: July 2010

Interseeding legumes into grass sods increases herbage quality. Interseeding alfalfa (Medicago sativa L.) into bermudagrass [Cynodon dactylon (L.) Pers.] has given yields comparable to grass fertilized with high rates of N. Our objective was to compare forage quality attributes of N‐fertilized bermudagrass with alfalfa‐bermudagrass mixtures. N rates of 0, 112, 224, and 448 kg ha−1 were applied to bermudagrass monoculture and to alfalfa interseeded into bermudagrass at 20‐, 40‐, and 60‐cm row spacings. Experiments were conducted on a Cecil sandy clay loam (clayey, kaolinitic, thermic Typic Kanhapludult) and a Norfolk sandy loam (fine‐loamy, siliceous, thermic Typic Kandiudult) site. Hand‐harvested herbage samples were separated into botanical components. Crude protein, acid‐detergent fiber and neutral‐detergent fiber were measured using a combination of wet‐lab and near infrared reflectance spectroscopy (NIRS) procedures. Nitrogen increased the crude protein in bermudagrass monoculture by 11 to 61 g kg−1. The crude protein response of bermudagrass in mixtures to N was slight to nonsignificant. Increasing row spacing of alfalfa reduced grass crude protein by 9 to 23 g kg−1 and had no effect on alfalfa crude protein. Fiber fractions decreased slightly in grass with added N, but fiber in alfalfa was not influenced by any treatment. Yield of crude protein increased with N, particularly in bermudagrass monoculture, but interseeding alfalfa without N produced crude protein yields that usually exceeded those of bermudagrass monoculture at the 448 kg ha−1 N rate. Interseeded alfalfa, even at wide row spacings, appears to produce enough biological N to replace 448 kg fertilizer N ha− or more in the production of herbage protein in bermudagrass.
Soil Moisture, Temperature, and Drying Influence on Soybean Emergence
Authors: Helms Theodore C. , Deckard Edward L. , Goos Robert J. , Enz John W.
Published: July 2010

Soybean [Glycine max (L.) Merr.] emergence is influenced by the interaction of initial seed zone soil water content and temperature. Stress due to soil water content that is great enough for seed imbibition but too low for radicle emergence from the testa reduces emergence. Previous research has not determined whether emergence is reduced by soil drying after the seeds have imbibed water. Our objective was to evaluate soybean emergence influenced by initial seed zone soil water content and soil drying at three day/night soil temperature regimes (17/8, 21/12, and 25/16°C) as the number of days of soil water deficit and temperature stress increased. The experiment was conducted under controlled temperature conditions using an incubator. Emergence depended on both initial seed zone soil water content and temperature. As the number of days of soil moisture deficit increased, soil drying reduced emergence at initial soil water contents of 0.07 and 0.09 kg kg−1. If the radicle had emerged from the testa and the soil water content was reduced below the initial soil water content due to drying, emergence was reduced. If seed imbibition occurred, but the initial soil moisture was too dry for the radicle to emerge from the testa, emergence decreased as the number of days of stress increased. The results show that the influence of seedbed drying on percent emergence depended on the initial soil water content and the number of days until adequate soil water content was restored.
Potential Uses and Limitations of Crop Models
Authors: Boote Kenneth J. , Jones James W. , Pickering Nigel B.
Published: July 2010

Crop models have many current and potential uses for answering questions in research, crop management, and policy. Models can assist in synthesis of research understanding about the interactions of genetics, physiology, and the environment, integration across disciplines, and organization of data. They can assist in preseason and in‐season management decisions on cultural practices, fertilization, irrigation, and pesticide use. Crop models can assist policy makers by predicting soil erosion, leaching of agrichemicals, effects of climatic change, and large‐area yield forecasts. Cautions and limitations in model uses are suggested, because appropriate use for a particular purpose depends on whether the model complexity is appropriate to the question being asked and whether the model has been tested in diverse environments. There is a need for both complex and simple models. In some cases, simple models are not appropriate because they are not programmed to address a particular phenomenon. In other cases, complex models are not appropriate because they may require inputs that are not practical to obtain in a field situation. Modelers need to be forthright in model description and promotion. For example, what does a given model respond to? What are the limitations of the model? What factors does the model not address? What are the limitations of inputs to run the models? Examples are given of model use to evaluate genetic improvement in photosynthesis and seed‐filling duration, yield response to planting date and row spacing, and effects of change in seasonal temperature. We believe that use of crop growth models will play an increasingly important role in research understanding, crop management, and policy questions.
Lentil Water Use and Fallow Water Loss in a Semiarid Climate
Authors: Aase J. Kristian , Pikul Joseph L. , Prueger John H. , Hatfield Jerry L.
Published: July 2010

With renewed interest in legumes for green manures or as partial summer fallow replacement crops, it is important to know water requirements of these crops in semiarid agriculture. Our objective was to evaluate seasonal water use by black lentil (Lens culinaris Medikus cv. Indianhead), a potential fallow replacement crop, and to relate water use to parameters useful as soil water management tools. We measured evapotranspiration (ET) from two precision weighing lysimeters located on a Williams loam (fine‐loamy, mixed Typic Argiboroll) near Sidney, MT. The lysimeters were in adjacent 180‐ by 180‐m fields in a typical strip‐crop environment of the semiarid northern Great Plains. Bowen ratio estimates of ET were also obtained. Lentil was seeded no‐till into wheat (Triticum aestivum L.) stubble on one lysimeter field in 1993, and the other was left in chemical fallow. Seeded and fallow fields were rotated in 1994. Water loss by ET from lentil and fallow lysimeters was the same (≈25 mm) for 3 wk following seeding. Plant height was related to growing degree days (GDD) in both years. Cumulative ET was related to GDD for both years until about 800 GDD, corresponding to nearly 300 mm ET. Deciding how much water to sacrifice (with hopes of recovery during the noncrop period) becomes a matter of judgment about probable rainfall. At full bloom (≈2 Mg ha−1 dry matter production), the lentil crop used about 50 to 70 mm more water than fallow. Probably no more than 50 mm of water loss above that from fallow should be sacrificed if a grain crop is to be seeded the following year. From a practical standpoint, because plant height was closely related to both GDD and cumulative ET, it is plausible that a simple measure of lentil height (about 350 mm maximum) can give sufficient accuracy for determining when lentil growth, as a partial summer fallow replacement crop in a semiarid climate, should be terminated.
Nitrogen Release from Grass and Legume Cover Crop Monocultures and Bicultures
Authors: Ranells Noah N. , Wagger Michael G.
Published: July 2010

The use of grass‐legume bicultures grown as winter annual cover crops may provide farmers with additional cover crop management options regarding the availability of cover crop residue N. A 2‐yr field experiment was conducted to determine dry matter (DM) accumulation, chemical composition, and N release from grass and legume cover crops grown in monoculture (rye, crimson clover, and hairy vetch) and biculture (rye‐crimson clover and rye‐hairy vetch). Air‐dried plant material was placed on the soil surface in 1‐mm mesh nylon bags for 1, 2, 3, 4, 6, 8, and 16 wk. Following retrieval, mesh bag contents were analyzed for total N, C, cellulose, hemicellulose, and lignin concentrations. The 2‐yr mean cover crop DM production was in the order of rye‐hairy vetch > hairy vetch > rye‐crimson clover > rye > crimson clover. The greatest cover crop N content (2‐yr mean) occurred with hairy vetch monoculture (154 kg N ha−1), compared with a low of 41 kg N ha−1 for the rye monoculture. When grown in biculture with rye, hairy vetch accumulated more DM and biomass N compared with crimson clover, both as a proportion of the biculture and as DM yield. In general, the order of N release rates (rapid to slow) was hairy vetch > crimson clover = rye‐hairy vetch > rye‐crimson clover = rye. Estimates of N (kg ha−1) released from cover crop residue after 8 wk of field decomposition, averaged over 2 yr, were 24 for rye, 60 for crimson clover, 132 for hairy vetch, 48 for rye‐crimson clover, and 108 for rye‐hairy vetch. Results of this study demonstrate only slight reductions in N release from grass‐legume bicultures compared with legume monocultures.
A Greenhouse Screening Technique for Acid Soil Tolerance in Maize
Authors: Urrea‐Gómez R. , Ceballos Hernán , Pandey Shivaji , Bahía Filho Antonio F.C. , León Luis A.
Published: July 2010

Evaluating maize (Zea mays L.) in the field for tolerance to soil acidity is expensive and provides variable results. To identify alternative screening techniques for maize, the present study adapted a pot bioassay already used for other crops. Two experiments were conducted. One included a set of diallel crosses from eight parents and the other a set of 10 open‐pollinated cultivars. These materials were evaluated under field conditions, in nutrient solution, and in pots containing 2 kg of soil. The best results were obtained after growing plants for 14 d in pots containing soils having intermediate stress (45–65% AI saturation). Fresh root weight, total length (or lateral root length), and visual scoring provided the best separation between tolerant and susceptible genotypes, lacked a significant genotype ✕ soil interaction, and were efficient, simple, and rapid measurements. Significant phenotypic correlations (≈ 0.55) were observed between these variables and yield in the field. While efficiently distinguishing tolerant from susceptible genotypes, the pot bioassay could not clearly detect differences in levels of tolerance. This technique should be useful mainly in the early stages of maize breeding. Results suggest that maize possesses several mechanisms for tolerance to soil acidity.
Responses of Tolerant and Susceptible Maize Varieties to Timing and Rate of Nitrogen under Striga hermonthica Infestation
Authors: Kim Soon‐Kwon , Adetimirin Victor O.
Published: July 2010

Purple witchweed [Striga hermonthica (Del.) Benth.], here called just striga, parasitizes cereal crops in the savanna zone of sub‐Saharan Africa. The objectives of this study were to investigate the expressions of a tolerant and a susceptible cultivar of maize (Zea mays L.) to striga as affected by timing (0, 2, 4, and 6 wk after maize planting) and rates (60 and 120 kg N ha−1) of N application under striga infestation. The experiment was designed as a split‐split plot with four replications. Timing of N application and N rates significantly affected striga emergence, host‐plant damage scores, agronomic traits, and grain yield. Nitrogen rate x application time interaction was highly significant for striga emergence. Time of N application was more important than N rate in suppressing striga emergence and host‐plant damage. Nitrogen application at 2 wk after planting and 120 kg N ha−1 gave the best result in terms of maize performance and reduction of striga emergence. Host‐plant damage symptoms were more useful in differentiating response of host genotypes to striga than striga emergence values. The tolerant cultivar (hybrid 8322‐13) produced 188% higher grain yield than the susceptible cultivar (hybrid 8338‐1) across all treatments. Grain yield of the tolerant cultivar at 60 kg N ha−1 was 88% higher than that of the susceptible cultivar at 120 kg N ha−1. The tolerant cultivar produced an average 157% more ears at 60 kg N ha−1 and 51% more ears at 120 kg N ha−1 than the susceptible cultivar. Among all the factors studied, the most important component for striga management was genetic tolerance, the ability of a host plant to withstand the parasite.
Growth and Yield Response of Field‐Grown Tropical Rice to Increasing Carbon Dioxide and Air Temperature
Authors: Ziska Lewis H. , Namuco Offie , Moya Toti , Quilang Jimmy
Published: July 2010

Although the response of rice (Oryza sativa L.) to increasing atmospheric CO2 concentration and air temperature has been examined at the greenhouse or growth chamber level, no field studies have been conducted under the tropical, irrigated conditions where the bulk of the world's rice is grown. At the International Rice Research Institute, rice (cv. IR 72) was grown from germination until maturity for the 1994 wet and 1995 dry seasons at three different CO2 concentrations (ambient, ambient + 200, and ambient + 300 μL L−1 CO2) and two different air temperatures (ambient and ambient + 4°C) using open‐top field chambers. Averaged for both seasons, increases in CO2 concentration alone (+ 200, +300 μL L~') resulted in a significant increase in total plant biomass (+ 31%, + 40%) and crop yield (+ 15%, + 27%) compared with the ambient control. The increase in crop yield was associated with an increase in the number of panicles per square meter and a greater percentage of filled spikelets. Simultaneous increases in CO2 and air temperature did not alter the biomass at maturity (relative to elevated CO2 alone), but plant development was accelerated at the higher growth temperature regardless of CO2. concentration. Grain yield, however, became insensitive to CO2 concentration at the higher growth temperature. Increasing both CO2 and air temperature also reduced grain quality (e.g., protein content). The combination of CO2 and temperature effects suggests that, in warmer regions (i.e., >34°C) where rice is grown, quantitative and qualitative changes in rice supply are possible if both CO2 and air temperature continue to increase.
Relating Plant Canopy Characteristics to Soil Transport Capacity by Wind
Authors: Armbrust Dean V. , Bilbro James D.
Published: July 2010

Federal legislation mandates that wind erosion soil losses be kept to a “tolerable” limit to maintain eligibility for federal farm programs on highly erodible land. Therefore, much interest has been generated in devising wind erosion models that accurately determine the potential erosion from a given site and also evaluate the effectiveness of any control measure. These models require mathematical relationships between surface properties and the transport capacity of the wind. Such relationships are available for soil surface roughness and plant residues, but not for growing crops. Our objective was to establish these relationships for growing crops. We developed a theoretical approach that accounts for the effect of stem area, leaf area, and canopy cover of growing crops on the soil loss ratio, threshold velocity, and transport capacity. The predictive ability of the theory was tested using published data sets from growing plants tested in a wind tunnel. Measured soil loss ratios were highly correlated to predicted values (r2 = 0.99, P = 0.001). The results showed that plant area index and canopy cover are highly correlated with reduction in the transport capacity of the wind and, therefore, serve as indicators of the soil protection afforded by growing plants. A plant area index of 0.02 and a canopy cover of 4% reduced the transport capacity of a 16 m s−1 wind by 50%. This method for determining the protective ability of a combination of growing plants and standing residue will improve predictive capabilities of wind erosion models for more diverse farm management conditions.