bluuebunny/crossref_metadata_2025 huggingface dataset:
Legume Cover Crop Options for Grain Rotations in Wisconsin
Authors: Stute James K. , Posner Joshua L.
Published: July 2010

Use of forage legumes as cover crops in the year prior to corn (Zea mays L.) is one way to reduce the amount of N fertilizer used in corn production. This study evaluated several forage legumes for dry matter (DM) production during the seeding year when established in grain rotations. Field studies were conducted near Arlington and Marshfield, WI, in 1989 and 1990. Treatments consisted of nine forage legumes: medium and mammoth red clover (Trifolium pratense L.), dormant and nondormant alfalfa (Medicago sativa L.), alsike clover (T. hybridum L.), ladino clover (T. repens L.), hairy vetch (Vicia villosa Roth), and two cultivars of yellow sweetclover [Melilotus officinalis (L.) Lam.]. Five establishment treatments tested were: seeded in the spring, companion‐seeded with oat (Avena sativa L.), interseeded into corn at last cultivation, and seeded following harvest of either canning pea (Pisum sativum L.), or oat for grain. In general, legume DM yields were highest in establishment periods which offered the longest growing season with the least amount of competition from the primary crop. Hairy vetch, the only annual legume used in the study, produced the highest yields in each of the five establishment periods, as high as 9.76 Mg ha−1 when spring seeded. The climbiing nature of this legume, however, makes it an unwise choice for companion seeding with small grains, a situation where the true clover species are best adapted. Dry soil conditions following pea or oat harvest often limited legume germination, seedling growth, and ultimately DM yield. Interseeding of legume cover crops into corn at last cultivation resulted in low seeding‐year DM yields. From the results of this study, we conclude that several legume‐establishment period combinations could be used successfully to produce N‐containing biomass.
Soil Fumigation within Monoculture and Rotations: Response of Corn and Mycorrhizae
Authors: Jawson Michael D. , Franzluebbers Alan J. , Galusha Deborah K. , Aiken Robert M.
Published: July 2010

The causative factors for corn (Zea mays L.) response to methyl bromide (CH3Br) fumigation, in the absence of known specific pathogens, are unknown. This study was conducted to determine if deleterious nonspecific rhizosphere microorganisms are the causative agents. Soil fumigation was postulated to increase yield of continuous corn but to have less effect on the yield of corn grown in rotation, because more deleterious rhizosphere microorganisms were suspected in monoculture than in rotation. The effects of fumigation and crop rotation on corn grain yield, plant height and P content, available soil N and P, mycorrhizal infection, and soil microbial biomass were investigated at two sites near Mead, NE, on a Sharpsburg silty clay loam soil (fine, montmorillonitic, mesic Typic Argiudoll). Methyl bromide treatments were applied prior to planting for 4 yr at one site and 2 yr at the other site. The sites differed in fertilization, pest management, and crop sequences, but both contained continuous corn. Fumigation resulted in an increase in grain yield under monoculture only once in six site years. Unexpectedly, however, fumigation resulted in a decrease in grain yield under rotation in 7 of 12 observations. Plants in fumigated soil were P‐deficient early in the growing season despite similar soil test P concentrations in control and fumigated plots. Fumigation reduced mycorrhizal infection and soil microbial biomass. Mycorrhizal infection of corn shortly after germination appears to be important to initial corn growth in this soil. Fumigating soil revealed a considerable biological influence on corn growth and yield by reducing both deleterious and beneficial microorganisms.
Soil Drainage Influence on Biomass and Nitrogen Accumulation by Ryegrass
Authors: Stout William L. , Schnabel Ronald R.
Published: July 2010

Grasslands are the basis for a stable agriculture in the Northeast USA. However, knowledge of interactive effects of soil drainage and N fertilization on grassland production in this region remains scant. Our objective was to quantify the effect of soil drainage on grassland biomass production and N accumulation. The study was conducted for 2 yr on a floodplain site in central Pennsylvania on two soils selected for extreme drainage conditions. Perennial ryegrass (Lolium perenne L. cv. Bastion) was treated with a split application (50% in mid‐April, 50% in mid‐July) of 0, 84, 168 and 252 kg N ha−1 of 15N depleted NH4NO3. Biweekly biomass samples were taken starting midMay of each year and continuing until the grass headed and all herbage was removed from the plots. Plots were re‐fertilized and monthly biomass sampling commenced at the end of August and continued until the end of October 31. Fertilizer nitrogen recovery was greatest in the first harvest after fertilization, irrespective of soil type or season. Peak fertilizer N recovery for spring growth was 50% on the well‐drained soil and 32% on the poorly drained soil. In the summerfall growth period, peak fertilizer N recovery was 26% on the well‐drained and 18% on the poorly drained soil. Biomass on the poorly drained soil was 26% less in the spring and 8% less in the summerfall periods compared with that of the well‐drained soil. Overall, poor soil drainage conditions resulted in a 39% reduction in fertilizer N recovery and a 21% reduction in yield of perennial ryegrass.
Soil Sampling Procedures for Monitoring Potassium Distribution in Grazed Pastures
Authors: Mathews Bruce W. , Sollenberger Lynn E. , Nkedi‐Kizza Peter , Gaston Lewis A. , Hornsby H. David
Published: July 2010

Nutrient redistribution in grazed pastures occurs primarily via deposition of excreta by animals. Because this redistribution is generally not uniform, a composite sample of randomly collected soil cores may not reflect the nutrient status of much of the pasture. To address this limitation, zonal soil sampling, with zones determined by distance from shade, water, and supplemental feeders (lounging areas), has been proposed as an alternative sampling strategy. This experiment was conducted to evaluate the potential of zonal soil sampling for monitoring extractable K distribution in grazed pastures. Utility of the zonal approach was evaluated by comparing it with a more rigorous, but less practical transect sampling procedure. Rotationally and continuously stocked bermudagrass [Cynodon dactylon (L.) Pers. ‘Callie’] pastures were used in the study. Ranges of extractable K within a pasture were as great as 13‐fold (14‐181 mg kg−1) after 2 yr of grazing. Extractable K concentration was greatest in the one‐third of the pastures closest to lounging areas regardless of grazing method. Data from zonal soil sampling described this distribution of soil K. Kriged contour maps constructed using data from transect soil sampling supported the conclusions made using zonal sampling. We conclude that zonal soil sampling is a useful and practical tool for describing K redistribution in pastures and for improving the utility of soil test results and fertilizer recommendations for grazed swards.
Maturity and Lint Yield of Nitrogen‐ and Phosphorus‐Deficient Pima Cotton
Authors: Tewolde H. , Fernandez C. J. , Foss D. C.
Published: July 2010

The Pima cotton (Gossypium barbadense L.) plant is inherently late maturing and unsuitable for production in areas where highly probable late‐season rainfall coincides with boll opening. A field study was conducted between 1990 and 1992 to determine if the maturity of Pima cotton can be enhanced with applied N and P without reducing lint yield. Five preplant‐applied N rates up to 180 kg ha−1 in 1990 and up to 269 kg ha−1 in 1991 and 1992 were tested. Four P rates from 0 to 45 kg ha−1 in a factorial combination with N were tested in 1991 and 1992. Nitrogen did not affect yield, days to first flower, or estimated percent open bolls in 1990. Nitrogen deficiency significantly enhanced maturity in 1991 and 1992. In 1991, >70% of the total bolls opened by 153 days after planting (DAP) where no N was applied, compared with 178 DAP where 202 or 269 kg N ha−1 was applied. In 1992, 68% of the bolls in the 0 kg N ha−1 treatment opened by 142 DAP, compared with <55% for all other treatments. The 0 kg N ha−1 treatment also significantly increased the ratio of reproductive to total plant dry weight earlier during the boll development period; however, the maturity‐enhancing effect of N deficiency occurred at the expense of lint yield. Relative to the 67 kg N ha−1 treatment, zero N reduced lint yield by 277 kg ha−1 (26%) in 1991 and 214 kg ha−1 (18%) in 1992. Phosphorus deficiency reduced lint yield in 1991, but did not affect percent open bolls or reproductive efficiency in 1991 and 1992. Earliness of Pima cotton may, therefore, be managed more effectively by minimizing applied N rates than by manipulating P fertilization.
Profile Water Distribution and Grain Yield as Affected by Cropping System and Tillage
Authors: Norwood Charles
Published: July 2010

Yields of dryland crops are limited by precipitation in the Great Plains. Winter wheat (Triticum aestivum L.) grown in the wheat‐fallow (WF) system (one crop in 2 yr) occupies the greatest area. The use of grain sorghum [Sorghum bicolor (L.) Moench] in the wheat‐sorghum‐fallow (WSF) system (two crops in 3 yr) is becoming popular. Other cropping systems include sorghum‐fallow (SF) and continuous sorghum (SS). Research was conducted in the central Great Plains at Garden City, KS, from 1987 through 1992 to quantify soil water storage and use and grain yield in the WF, WSF, SS, and SF systems in order to develop more efficient dryland grain production systems. No tillage (NT) and conventional tillage (CT) were compared in the WF and WSF systems. Available soil water at planting and harvest was measured in 0.3‐m increments to a depth of 1.5 m, and grain yield and water use efficiencies were determined. Water moved deeper in the profile under NT. Compared with CT, twice as much water was stored due to NT in the WSF sorghum profile as in the WF and WSF wheat profiles. An average of 62% of the additional water was found below 0.9 m. As much water was stored in the 11‐mo fallow period prior to WSFNT sorghum as was stored in the 15‐ and 19‐mo fallow periods of WF and SF. No tillage resulted in yield increases 17% of the time in WF, 34% of the time for wheat in WSF, and 60% of the time for sorghum in WSF. For sorghum, the yield of SF was similar to that of WSFNT, whereas SS had the lowest grain yield per planted hectare. Efficient storage of precipitation in WSF prior to NT sorghum and increased sorghum yield make the WSFNT system superior to other systems in this study.
Differential Competitive Ability of Winter Wheat Cultivars against Downy Brome
Authors: Blackshaw Robert E.
Published: July 2010

Downy brome (Bromus tectorum L.) causes large yield reductions in winter wheat (Triticum aestivum L.) in the western USA and Canada. Current control practices using fallow and preseeding tillage often are ineffective. A study was conducted over 3 yr at Lethbridge, AB, to determine if winter wheat cultivars varying in height and growth habit differ in their competitive ability with downy brome. A factorial set of treatments included downy brome at 0, 10, 50, and 200 plants m−2 grown with winter wheat cultivars Norstar, Redwin, Archer, and Norwin. Downy brome reduced the biomass and seed yield of all cultivars in all years, but the magnitude of the yield reductions differed among cultivars. Downy brome caused 14 to 30% greater yield reductions in the semidwarf cultivars, Archer and Norwin, than in the tall cultivars, Norstar and Redwin. This differential response among cultivars is partly attributable to competition for light. Norstar and Redwin shaded downy brome for much of the growing season, but Archer and Norwin often were shaded by downy brome. Planting a more competitive cultivar of winter wheat results in higher crop yields and less downy brome seed for weed establishment in subsequent crops. Use of competitive winter wheat cultivars should be a component of integrated weed management systems for downy brome.
Growth Dynamics of the Cotton Plant during Water‐Deficit Stress
Authors: Ball Rosalind A. , Oosterhuis Derrick M. , Mauromoustakos Andy
Published: July 2010

Information on the differential growth response of roots and shoots to water‐deficit stress will better describe root growth within the soil for purposes of modeling plant growth and assessment of drought resistant traits. Our aim was to investigate leaf expansion and changes in root elongation for field and growth‐chamber cotton (Gossypium hirsutum L.) during drought. Plants were grown in rhizotron containers and subjected to 6 d of water‐deficit stress followed by 6 d of recovery and compared with a well‐watered control. The stress period commenced when the plants were 55 to 65 d old. Leaf expansion was more sensitive to stress than root elongation, with curtailed growth after 2 d of withholding water compared with 6 d with roots. Stress reduced root elongation and root volume. About 85% of visible roots showed elongation growth under conditions of adequate water, which was reduced by stress to 50%. Small (0.30 mm mean diam.) roots were more abundant and gave the greatest cumulative length, but grew less on a mean length basis than medium roots (0.62 mm mean diam.). The rate of root growth increased during recovery, consisting of regrowth from stalled roots and followed later by initiation of new roots. Medium roots contributed the most to root volume initiated during recovery. Most growth for both root sizes occurred in the lower zone of the soil, where water was more available. Root size and position of roots within the soil profile are important factors to consider when studying root growth response to water‐deficit stress.
Feed Value of Forage Maize Hybrids Varying in Tolerance to Plant Density
Authors: Pinter L. , Alfoldi Z. , Burucs Z. , Paldi E.
Published: July 2010

The yield response of forage maize (Zea mays L.) genotypes to plant density is not as clear as for grain hybrids, where density tolerant and sensitive types have been identified. A study including field trials, laboratory analyses, and in situ digestibility tests with one density‐tolerant and one sensitive hybrid was conducted with plant densities of 4 to 16 plants m−2. The investigations concentrated on stover. There are differences in sensitivity to planting density in forage maize yield. Differences between sensitive and tolerant genotypes in plant density range for maximum yield were 0.43 and 1.18 plants m−2 for grain and forage, respectively. The decreased sensitivity for grain compared with forage was 50.7 and 100.0% for the sensitive and the tolerant hybrid, respectively. It was not possible to separate the tolerant and sensitive hybrids in terms of total digestible nutrients (TDN), a measure of overall feed value. For plant densities lower than those required for maximum dry matter yield, there was a significant difference between the tolerant and the sensitive hybrid in TDN.
Evaluation of LEACHM: I. Simulation of Drainage, Bromide Leaching, and Corn Bromide Uptake
Authors: Jemison John M. , Jabro Jalal D. , Fox Richard H.
Published: July 2010

Use of mathematical models to predict solute transport in soils, for research purposes, is increasing, but simpler management‐oriented models are needed that require less field‐specific data. Evaluation is needed to know which type of model is appropriate. The input‐intensive research and simpler management options of the pesticide and tracer version of LEACHM (LEACHMP) were evaluated to predict drainage in zerotension pan lysimeters, bromide (Br−) leaching, and corn (Zea mays L.) Br− uptake from a 3‐yr leaching experiment. Eighteen pan lysimeters (0465 m2) were installed 1.2 m below the soil surface to collect gravitational water samples. In May 1988, a one‐time application of KBr was broadcast to all plots at 100 kg Br− ha−1. Corn Br− uptake was evaluated by taking whole‐plant samples at 2‐wk intervals in 1988 and 1989. The research model adequately predicted drainage. Significant differences between predicted and observed drainage were not found, and the correlations were significant (0.73 to 0.83). The management model, however, significantly underestimated cumulative drainage. The research model overestimated Br− leaching, because the convectiondispersion equation used in LEACHMP cannot model dual‐pore water flow and solute diffusion found in this soil. The model generally underpredicted corn Br− uptake, which probably contributed to the overpredicted Br− leaching. The research version of LEACHMP adequately modeled drainage, but a more sophisticated approach to solute transport and corn Br− uptake is needed to adequately model Br− movement in this soil‐plant‐water system. Management model results were generally less accurate than the research model.
An Approach for Estimating a Decay Series for Organic Nitrogen in Animal Manure
Authors: Klausner Stuart D. , Kanneganti V. Rao , Bouldin David R.
Published: July 2010

Animal manures are an important source of N for crop production. Efficient use of manure is necessary to increase N recycling, eliminate excessive purchase of fertilizer N, and reduce N loss to the environment. An estimate of the annual rate of organic N mineralization in manure is a necessary prerequisite to efficient manure N management. A mineralization or decay series for the organic N in dairy manure was estimated for corn (Zea mays L.) production from several field experiments over a 5‐ to 8‐yr period. Four rates of sidedressed fertilizer N (0, 56, 112, and 224 kg N ha−1) were superimposed over several springapplied manure treatments ranging from 0 to 168 Mg ha−1 yr−1. Ammonia volatilization from manure was encouraged, to allow for an assessment of the fertilizer N equivalence of the more stable organic N fraction. Based on silage dry matter yield and N uptake, a decay series of 0.16, 0.10, 0.03, 0.03 and 0.02, and 0.21, 0.09, 0.03, 0.03 and 0.02, respectively, described the fertilizer N equivalence of organic N. The first number in the decay series estimates the fraction of organic N that is available for crop use during the year of application, and the second to fifth numbers are estimates of available N from residual N in Years 2 through 5. An independent set of field data was used to evaluate the accuracy of the decay series. The predicted decay series, based on dry matter yield (R2 = 0.16) was more variable than the corresponding decay series based on N uptake (R2 = 0.72). The non‐N effects of manure were insignificant, and therefore yield and N uptake were directly related to the N contribution.
Fate of Legume and Fertilizer Nitrogen‐15 in a Long‐Term Cropping Systems Experiment
Authors: Harris Glendon H. , Hesterman Oran B. , Paul Eldor A. , Peters Steven E. , Janke Rhonda R.
Published: July 2010

Relying more on biological N2 fixation has been suggested as a way to meet one of the major challenges of agricultural sustainability. A 15N study was conducted to compare the fate of applied legume and fertilizer N in a long‐term cropping systems experiment. Nitrogen‐15–1abeled red clover (Trifolium pratense L.) and (NH4)2SO4 were applied to microplots within the low‐input and conventional cropping systems of the Farming Systems Trial at the Rodale Institute Research Center in Pennsylvania. The 15N was applied to soil and traced into corn (Zea mays L.) in 1987 and 1988. Residual 15N was also traced into second‐year spring barley (Hordeum vulgare L.). Legume and fertilizer 15N remaining in soil was measured and loss of N was calculated by difference. More fertilizer than legume N was recovered by crops (40 vs. 17% of input), more legume than fertilizer N was retained in soil (47 vs. 17% of input), and similar amounts of N from both sources were lost from the cropping systems (39% of input) over the 2‐yr period. More fertilizer than legume N was lost during the year of application (38 vs. 18% of input), but more legume than fertilizer N was lost the year after application (17 vs. 4% of input). Residual fertilizer and legume 15N was distributed similarly among soil fractions. Soil microbial biomass was larger in the legume‐based system. A larger, but not necessarily more active, soil microbial biomass was probably responsible for the greater soil N supplying capacity in the legume‐based compared with fertilizer‐based system.
Root Distribution of Corn: The Effect of Nitrogen Fertilization
Authors: Durieux Robert P. , Kamprath Eugene J. , Jackson William A. , Moll Robert H.
Published: July 2010

Root growth and development can affect N uptake. In turn, N additions may affect corn (Zea mays L.) root growth. Prolific (multiple ear) hybrids may need a more active root system to satisfy ear demand. To determine the extent of the effect of N fertilization on root growth in the field, three corn hybrids (Pioneer 3320, and prolific hybrids I202×Mol7 and I117×B73) were grown under fertilizer application rates of 56, 140, and 224 kg N ha−1 to determine (i) whether application of N fertilizer stimulated root growth of corn in the zone of application in the field 20 d before silking, at silking, and at physiological maturity and (ii) whether prolific hybrids have enhanced root development before silking compared with nonprolific hybrids. All three hybrids were grown at a uniformly low plant‐population density. Root length density to a depth of 60 cm, averaged over hybrids, was 1302, 2238, and 1184 m plant−1 in 1987, and 2195, 2833, and 3317 m plant−1 in 1988 for the three sampling dates. There were few genotypic differences in root length density. Root weight averaged over hybrids was 20.4, 40.5, and 21.5 g plant−1 in 1987, and 44.6, 61.7, and 58.9 g plant−1 in 1988 for the three sampling times, respectively. Root weight at harvest declined as N application increased, but increased in response to N at two earlier sampling times. The second year of the study, when rainfall was more plentiful than in the first year, root growth continued after silking for all hybrids. This coincided with higher yields. The data suggest that N stimulated root length in the area of application, without affecting total root length.
Optimizing Yield and Grain Protein in Soft White Winter Wheat with Split Nitrogen Applications
Authors: Sowers Karen E. , Miller Baird C. , Pan William L.
Published: July 2010

Grain protein of soft white winter wheat (Triticum aestivum L.) produced in eastern Washington has increased above market‐desired levels over the past decade, when subnormal precipitation and overfertilization contributed to excessive residual soil N levels. A field study was conducted over four site‐years to (i) examine N effects on the yield‐protein relationship of soft white winter wheat under high soil N conditions, (ii) determine if split N applications can maintain yield and reduce grain protein, and (iii) evaluate midseason grain analysis as a predictor of final grain protein. Nitrogen rates ranged from 0 to 140 kg N ha−1; timing treatments were fall preplant N and spring topdressed or point‐injected N. High yields (>5900 kg ha−1) were produced without fertilizer N, and yield responses to N ranged from 0 to 22%. Fall N < 56 kg N ha−1 increased yield in only one site‐year; yields were reduced due to excess N fertilization in another site‐year in conjunction with shallow N depletion and poor water extraction from deeper soil layers. In two of four site‐years, yield increased with a 50% fall‐50% spring point‐injected N compared with 100% fall application at 84 kg total N ha−1. Protein >100 g kg−1 was produced in site‐years where most soil N was depleted below the 90‐cm depth; shallow N depletion was associated with lower protein. Grain N concentration at maturity was highly correlated with grain N concentration at the late milk and soft dough stages. Preharvest predictions of final grain protein may be useful in segregating grain at harvest for marketing purposes. Under high residual soil N levels, reduced N rates and split N applications between fall and spring can maintain high yields and reduce grain protein.
Feeding Activity, Growth, and Survival of Soybean Looper on Low‐Nitrogen Nonnodulating Soybean
Authors: Wier Alan T. , Boethel David J.
Published: July 2010

Feeding and larval development of several lepidopteran species are influenced by reduced foliage N of host plants. Nonnodulating soybean [Glycine max (L.) Merr.] isolines have exhibited foliar symptoms typical of N deficiency in field plots in absence of supplemental N. Under these chlorotic conditions, reducedefoliation and larval development of soybean looper [Lepidoptera:Noctuidae, Pseudoplusia includens (Walker)] have been observed. This study was conducted to evaluate the influence of foliage N level of nodulating and nonnodulating soybean isolines on feeding and development of the soybean looper. Two feeding studies involving the soybean looper and foliage of nodulating and nonnodulating isolines of #x2018;Clark’ soybean were conducted using foliage collected from plants in full bloom (R2) and in the beginning seed stage (R5). The foliage N level of the nonnodulating isoline was not significantly lower than that of the nodulating isoline when collected at R2 and, consequently, only slight effects on feeding and development were attributable to consumption of nonnodulating isoline foliage. However, chlorosis and a 43% reduction in the foliage N level of the nonnodulating isoline occurred by R5, resulting in limited compensatory feeding, extended larval development, and reduced survival when soybean loopers consumed this isoline. Foliage N concentrations of ≈40 mg g−1 leaf dry weight were sufficient for soybean looper development from the neonate to the adult stage, while concentrations of 23 mg g−1 leaf dry weight were inhibitory.
Sowing Date Effects on Grain Yield Components for Different Maize Genotypes
Authors: Otegui María E. , Nicolini María G. , Ruiz Ricardo A. , Dodds Pablo A.
Published: July 2010

Shoot dry weight of maize (Zea mays L.) depends on the amount of photosynthetically active radiation intercepted by the crop (IPAR). The present work was conducted to analyze the variation in shoot dry weight production and its partitioning to reproductive sinks when seasonal changes of temperature and solar radiation occur during the growing cycle of the crop. Four commercial hybrids were grown at 8 plants m−2 on four sowing dates (20 Aug., 20 Sept., 20 Oct., and 20 Nov.) at Rojas (34° 08' S, 60° 59' W), Argentina, on a silty clay loam soil (Typic Argiudoll) during 1990‐1991 and 1991‐1992, with no water or nutrient restrictions. Shoot dry weight at physiological maturity was associated with the amount of IPAR, with radiation use efficiency before silking (4.14 g MJ−1) higher than after silking (2.45 g MJ−1). Grain yield was correlated with shoot dry weight at physiological maturity, resulting in a stable (0.46 ± 0.02) harvest index. Shoot dry weight at silking showed a significant relationship with final grain number (r2 = 0.52, n = 32) as well as with grain yield (r2 = 0.55, n = 32). Ear dry weight at silking was associated with grain yield particularly for prolific hybrids (r2 = 0.64, n = 16). Provided postsilking conditions do not limit assimilate supply to the grains, shoot dry weight at silking could be considered a good grain yield predictor. In temperate regions, maize potential productivity seems to be more limited by the amount of solar radiation available around silking (determinant of grain set) than during grain filling (determinant of grain weight). Early and intermediate sowings tend to best utilize solar radiation for grain production.
Regression and AMMI Analyses of Genotype × Environment Interactions: An Empirical Comparison
Authors: Yau Sui K.
Published: July 2010

Joint regression analysis (JRA) is a popular method for analyzing genotype × environment (G × E) interactions, but multivariate techniques such as AMMI (additive main effects and multiplicative interaction) analysis have been recently advocated. The objective of this study was to investigate and compare empirically the effectiveness of the two techniques under differing environmental diversity and numbers of environments, and when log‐transformed data were used for JRA. I analyzed grain yield data from three seasons of a regional bread wheat (Triticum aestivum L.) yield trial, grown at 30 to 40 sites. Sites were split into irrigated‐high rainfall and rainfed‐low rainfall groups. Three equal‐size samples differing in environmental diversity and three similar diversity samples differing in numbers of sites were also formed. Both raw and log10‐transformed data were used for JRA. The fitting mode of the MATMODEL program (version 2.0) was used on raw data for AMMI analysis. Percentages of interaction sum of squares (SS) accounted for by heterogeneity of regression in JRA were generally low (mean = 11%) and unaffected by diversity of the samples, but inversely related to number of sites in the similar‐diversity samples. In contrast, percentages of interaction SS accounted for by first principal components in AMMI analyses were generally high (mean = 37%) and unaffected by diversity or number of sites in the samples. These percentages were always higher for AMMI than for JRA, regardless of whether log‐transformed data were used for JRA. The use of AMMI is recommended for detailed studies of G × E effects, especially for large regional or international trials.
Establishing a Rejection Procedure for Crop Performance Data
Authors: Bowman Daryl T. , Rawlings John O.
Published: July 2010

Crop performance trials are conducted to provide unbiased relative performance data for breeders, growers, and extension personnel. This report presents a method for establishing a criterion level of precision for rejection of questionable data. For a given crop, historical data (a minimum of 30 data points) are used to calculate average error variance and to determine any relationship between productivity level and error variance by regressing log(variance) on log(mean) for the variable of primary interest, usually yield. A nonsignificant relationship dictates using the pooled error variance over all trials as the reference or expected variance; a significant relationship dictates using the fitted variance predicted from the regression at the observed mean yield of each trial. An upper bound on error variance (a multiple k of the expected error variance) is calculated. Any trial with an observed error variance above the upper bound would be discarded as having unusually low precision. Historical data from five crop species tested in North Carolina were examined as working examples. Of eight data sets, four showed no relationship between variance and productivity level on a log‐log scale. Compared with corn and soybean, more small‐grain (barley, oat, and wheat) trials were above the criterion level when k = 2. Thus, k‐values may need to be adjusted among crop species. Most trials with unacceptably low precision showed a record of some sort of problem, although it could not be confirmed that the noted problem caused the high variability. Researchers using the proposed procedure are cautioned to examine their data closely to ensure an appropriate k‐value and to note test sites of low precision or methods causing low precision.
Surface Runoff Assessment from Creeping Bentgrass and Perennial Ryegrass Turf
Authors: Linde Douglas T. , Watschke Thomas L. , Jarrett Albert R. , Borger Jeffrey A.
Published: July 2010

The potential for offsite movement of nutrients and pesticides in surface runoff from golf courses has generated a need to better understand the movement of water from intensely maintained turfgrass. This study assessed the influence that creeping bentgrass [Agrostis stolonifera L. var. palustris (Huds.) Farw.; syn. Agrostis palustris Huds.] and perennial ryegrass (Lolium perenne L.) had on the surface movement of water when maintained similarly to golf fairways. On eight dates, 123.5‐m2 sloped plots of bentgrass and ryegrass were irrigated at 152 mm h−1 to force runoff for the generation of hydragraphs. As the grasses matured, runoff from ryegrass occurred earlier and at greater volumes than from bentgrass. Four additional experiments were conducted to provide some explanation of these runoff differences. In one experiment, average infiltration rates for the bentgrass (64 mm h−1) and ryegrass (35 mm h−1) plots were not significantly different, because of high sampling variation. In an experiment that used 0.25‐m2 sloped trays of turf, bentgrass retarded the flow of surface runoff through its vegetation significantly longer than ryegrass. It was also found that bentgrass (1410 tillers dm−2) intercepted 113% more water than ryegrass (260 tillers dm−2), and that bentgrass thatch slowed runoff initiation because of its high water‐holding capacity and increased hydraulic resistance. The high‐density, thatch‐forming bentgrass provided a more tortuous pathway for water movement, which increased resistance and in turn increased residence time and allowed for greater infiltration. For golf courses that have potential runoff concerns, the selection of creeping bentgrass rather than perennial ryegrass could reduce surface runoff from golf fairways.
Soybean Seed Number and Crop Growth Rate during Flowering
Authors: Jiang Hongfei , Egli Dennis B.
Published: July 2010

Seeds per unit area is an important yield component in soybean [Glycine max (L.) Merrill]; however, the mechanisms regulating seed number are not well understood. Field and greenhouse experiments were conducted to investigate the relationship between photosynthesis during flowering and podset and seeds per square meter. Shade cloth (30 and 63% reduction in insolation) was used to reduce photosynthesis from emergence to Growth Stage R1 in the field ['Pennyrile' (indeterminate) and 'Ripley' (determinate)] or for varying periods during flowering and podset in the greenhouse ('McCall') and field (Pennyrile). Shade during vegetative growth reduced mass per square meter (21‐52%) at Growth Stage R1, but had no effect on crop growth rate (CGR) during flowering and podset (R1 to R5) or seeds per square meter if light interception after R1 was not reduced. Shade during flowering and podset reduced seeds per square meter in relation to the length of the shade treatment. In the field, shade from R1 to R4 and R4 to R6 had similar effects on seeds per square meter; these were less (31%) than the unshaded control for both treatments. These results suggest that maximum photosynthesis throughout flowering and podset may be required to maximize seeds per square meter. There were linear relationships between average CGR during R1 to R5 and seeds per square meter across experiments and treatments in both field and greenhouse. These relationships support previous results suggesting that seeds per square meter is determined primarily by canopy photosynthesis during flowering and podset.
Corn Responses to Chloride in Maximum Yield Research
Authors: Heckman Joseph R.
Published: July 2010

Chloride nutrition of corn (Zea mays L.) was investigated to determine if Cl limits production in high‐yield environments. Experiments were conducted to evaluate the effects of Cl fertilization on a Freehold sandy loam (fine‐loamy, mixed, mesic Typic Hapludults) near Adelphia, NJ, using irrigation and intensive crop production practices. Corn was grown at 107 600 plant ha−1 with equidistant spacing. All plots received 454 kg K ha−1 using KOH, K2SO4, or KCl to establish five treatments: 0, 50, 100, 200, and 400 kg Cl ha−1. Positive responses of corn to added Cl were observed each year. In 1990, the Cl treatments averaged 1.1 Mg ha−1 more grain than the check yield of 11.3 Mg ha−1 (P = 0.08). In 1991, the check yield was 19.0 Mg ha−1 and the response to Cl was linear up to the 400 kg ha−1 rate, which yielded 20.5 Mg ha−1. In 1992, the Cl treatments averaged 0.5 Mg ha−1 more grain than the check yield of 14.5 Mg ha−1 (P = 0.07). Grain yields were positively correlated with increases in ear‐leaf Cl concentration. Increases in grain yield were associated with increased ear size. Chloride did not increase stover yield. A linear decrease in incidence of stalk rot with Cl rate was observed in 1992. Results suggest that, when produced in high‐yield environments, corn may respond to enhanced levels of Cl nutrition.
Paper Mill Boiler Ash and Lime By‐Products as Soil Liming Materials
Authors: Muse John K. , Mitchell Charles C.
Published: July 2010

The pulp and paper industry in the southeastern USA produces ≈ 6500 t of boiler ash and lime by‐products (waste lime, grit, and dregs) daily. A survey of 88 pulp and paper mills indicated that most of these by‐products are placed in landfills, with only 10% being land‐applied. Seventeen boiler ash samples and 14 lime by‐products from 12 Alabama pulp and paper mills were analyzed and evaluated for their potential as soil liming materials. Most boiler ash resulted from the burning of wood or wood in combination with other materials and averaged 37% calcium carbonate equivalent (CCE), while 14 lime by‐products averaged 99% CCE. In an 84‐d incubation study, boiler ash and lime by‐products applied to an acid (pH = 5.2) Marvyn loamy sand (fine‐loamy, siliceous, thermic, Typic Kanhapludults) at equivalent rates based on CCE resulted in mean pH values significantly higher than values achieved with agricultural lime. All materials increased Mehlich‐1 extractable P, K, and Mg. In a field study conducted on an acid (pH = 5.1) Vaiden clay (very‐fine, montmorillonitic, thermic Vertic Hapludalfs), dallisgrass‐fescue (Paspalum dilatatum Poir.‐Festuca arundinacea Schreb.) herbage yield increased 62% the second year and 49% the third year after surface application of boiler ash, lime by‐products, and agricultural lime.
Axial Resistance to Water Flow of Intact Cotton Taproots
Authors: Yamauchi Akira , Taylor Howard M. , Upchurch Dan R. , McMichael Bobbie L.
Published: July 2010

A knowledge of root hydraulic resistance is required for the application of water flow models of the plant‐soil system. An attempt was made to estimate axial resistance of intact cotton (Gossypium hirsutum L. cv. Tamcot CAMD‐E 107‐5A) taproots to water flow by direct and simultaneous measurement of water flow rate and of the gradient in xylem water potential. Fiscus's root psychrometer was modified and used for the measurement of xylem water potential. The measurements were made in rigidly controlled, constant temperature environments, and under conditions in which no water was available for the portion of the taproot where xylem water potential gradient was measured, but water was available distal to that portion. The water uptake rate was simultaneously measured while water was supplied at a constant head. Axial resistance to water flow along a cotton taproot of 70‐ to 120‐d‐old plants was on the order of 1 mg−1 water m−1 root s MPa, which is near the lower limit of published values for cotton and other species. Axial resistance was also calculated from the measured xylem vessel diameters based on the Poiseuille‐Hagen equation. Measured axial resistance values were ≈ 20 times those calculated using the Poiseuille‐Hagen equation. It required as long as 34 d for the water potential inside the psychrometer chamber to equilibrate with that of the root xylem. Drying the root substantially increased the radial resistance and thereby increased the time required for equilibration. Modifications to the described experimental apparatus and procedure will be required.
Biomass and Nitrogen Accumulation in Switchgrass: Effects of Soil and Environment
Authors: Stout William L. , Jung Gerald A.
Published: July 2010

Grasslands are the basis of animal agriculture in the northeastern USA. Adapted warm‐season grasses make a valuable contribution to grassland production in this region, but knowledge of the interactive effects between soils and environment on their production is limited. Our objective was to examine and evaluate the interactive effects of soils and environment on biomass and N accumulation by switchgrass (Panicum virgatum L. cv. Cave‐n‐Rock), an adapted warm‐season grass. The study was conducted for 3 yr on four sites in central Pennsylvania selected to provide differences in soil water holding capacity and temperature regime. Switchgrass was treated with 0 and 84 kg N ha−1 as NH4NO3. Biweekly biomass samples were taken starting 15 June and continued until the grass reached heading stage, approximately 31 July. Biomass accumulation rates for this 31‐d period ranged from 157 to 211 kg ha−1 d−1. Soil N, N fertilization, and temperature controlled biomass accumulation rates. Total N uptake rates ranged from 1.49 to 2.63 kg ha−1 d−1 and were controlled by soil N levels and N fertilization. Fertilizer N recovery averaged about 40%, and was lowest where native soil N exceeded 2.0 g kg−1.
Nitrogen Dynamics in Irrigated Corn: Soil‐Plant Nitrogen and Atmospheric Ammonia Transport
Authors: Harper Lowry A. , Sharpe Ronald R.
Published: July 2010

Ammonia transport in cropping systems can affect atmospheric pollution, soil‐plant N relationships, and crop N‐use efficiency. The purpose of this study was to evaluate the N dynamics of a corn (Zea mays L., Pioneer hybrid 3379) cropping system and determine the effect of NH3 transport and crop NH3 compensation point on N relations in the crop. Soil and plant N measurements were made during the growing season along with plant‐atmosphere NH3 transport using flux‐gradient micrometeorological techniques. The crop generally emitted NH3 throughout the season when the atmospheric NH3 concentrations were near background levels. During periods of high atmospheric NH3 concentrations, the crop absorbed significant amounts of NH3 from the atmosphere. Net seasonal NH3 transport was determined to be a small loss, based on the number of measurement periods throughout the growing season; however, N isotope studies in a nearby field estimated significant NH3 losses. Nitrogen isotope studies cannot account for the substitution of 14NH3 absorbed from the atmosphere for volatilized 15NH3. These results indicate that care must be taken when using N isotopes to evaluate N losses from cropping systems when plants are actively growing. Nitrous oxide flux was measured late in the cropping season, but showed small denitrification losses during the measurement period. The crop NH3 compensation point varied during the time of day and with respect to soil‐plant‐atmosphere influence. Net NH3 transport accounted for little of the N lost from this cropping system.
Forage Potential of Spring and Winter Cereal Mixtures in a Short‐Season Growing Area
Authors: Jedel Patricia E. , Salmon Donald F.
Published: July 2010

Cereal crops are often used in short‐season growing areas as annual forages for silage, greenfeed, or pasture. Field tests were conducted at Lacombe, AB, Canada, from 1989 to 1991 to determine the forage yield and quality of spring cereal monocrops of ‘Wapiti’ spring triticale ( ✕Triticosecale Rimpani Witt.) or ‘Johnston’ spring barley (Hordeum vulgare L.) and of binary mixtures of the spring cereals with ‘OAC Wintri’ winter triticale or ‘Musketeer’ winter rye (Secale cereale L.) grown at 1 × (260 seed m−2) and 1.5 × normal seeding rate. Dry matter (DM) yield and quality were determined for two simulated forage regimes: (i) a soft‐dough cut for silage, followed by fall clipping, and (ii) annual pasture with up to five clippings during the growing season. Yields of the spring cereal monocrops were 3.34 to 15.94 t ha−1 when harvested for silage, with fall clipping yields of 0.00 to 1.00 t ha−1. Yields for the mixtures were 2.88 to 14.64 t ha−1, with fall clipping yields of 0.05 to 2.39 t ha−1. For the annual pasture regime, initial clipping yields of spring cereal monocrops were 0.29 to 1.96 t ha−1; yields of the mixtures were 0.18 to 1.93 t ha−1. Monocrop yields declined over the growing season, while yields from the mixtures increased to midsummer and then declined (but less rapidly than for the monocrops). Under the annual pasture regime, quality of all treatments for the early clippings was similar, but by late summer and fall the mixtures had higher protein and lower acid‐detergent fiber concentrations than the spring cereal monocrops. The 1.5 × seeding rate resulted in higher DM yield when harvested for silage and for the initial clip when harvested for annual pasture. Spring‐winter cereal mixtures may extend productivity and high quality of annual pastures in short‐season growing areas.
Post Stratification Clarifies Treatment Effects on Pearl Millet Growth in the Sahel
Authors: Buerkert Andreas , Stern Roger D. , Marschner Horst
Published: July 2010

Spatial variation in the growth of pearl millet [Pennisetum glaucum (L.) R. Br.] over short distances is a problem in field experiments in the Sahel, but the causes are still poorly understood. Data from a 3‐yr experiment with millet were used to compare four data types for their usefulness for reducing variation not related to treatment: (i) soil chemical data, (ii) residuals of the first year's yield data, (iii) a traditional fertility classification system, and (iv) plant vigor scores. The completely randomized experiment consisted of four factors combined to 48 treatments, replicated twice. There were three levels of millet crop residues (CR), two levels of broadcast P, and four genotypes; the fourth factor had two levels and varied over years. Whereas chemical analyses of the topsoil did not explain overall variation, residuals of plant scores used as covariates led to a reduction in residual variation of 32% for straw and 51% for grain yield in 1991. Most satisfactory, however, was the use of residuals of plant scores to classify plots into two strata of relatively low and high inherent soil productivity (a retrospective procedure called post stratification). In low‐productivity plots, a CR application of 2000 kg ha−1 (compared with 500 kg ha−1) increased millet straw yield by an average of 42% and grain yield by 48% for the first 2 yr. In contrast, under high productivity, yields were barely influenced by treatments. The application of P, however, was equally effective in both productivity strata. The results show that vigor scores can be useful to clarify treatment effects on millet growth. The different responses of crop residues and P in the two productivity strata also indicate that nonchemical parameters such as soil mechanical resistance may contribute to soil microvariability in the Sahel.