bluuebunny/crossref_metadata_2025 huggingface dataset:
Weed Suppression by Seven Clover Species
Authors: Ross Shirley M. , King Jane R. , Izaurralde R.César , O'Donovan John T.
Published: July 2010

Used as cover crops, clover species may differ in their ability to suppress weed growth. Field trials were conducted in Alberta, Canada to measure the growth of brown mustard [Brassica juncea (L.) Czern.], in mowed and nonmowed production, as influenced by alsike (Trifolium hybridum L.), balansa [T. michelianum Savi var. balansae (Boiss.) Azn.], berseem (T alexandrinum L.), crimson (T. incarnatum L.), Persian (T. resupinatum L.), red (T. pratense L.), and white Dutch (T. repens L.) clover and fall rye (Secale cereale L.). In 1997, clovers reduced mustard biomass in nonmowed treatments by 29% on a high‐fertility soil (Typic Cryoboroll) at Edmonton and by 57% on a low‐fertility soil (Typic Cryoboralf) at Breton. At Edmonton, nonmowed mustard biomass was reduced by alsike and berseem clover in 1996 and by alsike, balansa, berseem, and crimson clover in 1997. At Breton, all seven clover species suppressed weed biomass. A negative correlation was noted among clover and mustard biomass at Edmonton but not at Breton. The effects of mowing varied with location, timing, and species. Mowing was beneficial to crop/weed proportion at Edmonton but not at Breton. Mowing at early flowering of mustard produced greater benefit than mowing at late flowering. With early mowing, all clover species suppressed mustard growth at Edmonton. Clovers reduced mustard regrowth (g plant−1) and the number of mustard plants producing regrowth. The characteristics of berseem clover (upright growth, long stems, high biomass, and late flowering) would support its use as a cover crop or forage in north‐central Alberta.
Tillage and Management Alternatives for Returning Conservation Reserve Program Land to Crops
Authors: Shapiro Charles A. , Holshouser David L. , Kranz William L. , Shelton David P. , Witkowski John F. , Jarvi Keith J. , Echtenkamp Gerald W. , Lunz Lisa A. , Frerichs Robert D. , Brentlinger Ray L. , Lubberstedt Mari A. , McVey McCluskey Melinda , Stroup Walter W.
Published: July 2010

Accumulated vegetative residue was a concern when Conservation Reserve Program (CRP) land returned to grain crop production. This study was conducted to determine the effect of residue management, tillage, and crop choice on grain yield in the first year of cropping on CRP land that was predominately smooth brome (Bromis inermis Leyss). Three residue management practices (undisturbed, shred, and remove), three tillage systems [moldboard plow, disk, and no till], and three crops {corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and grain sorghum [Sorghum bicolor (L.) Moench]} were used in a factorial arrangement of a 3‐yr field experiment conducted in Nebraska on fine‐silty, mixed, mesic Udic Haplustoll; fine‐silty, mixed (calcareous), mesic Typic Ustorthent; and fine‐silty, mixed, mesic Cumolic Halustoll soils. Residue management was not significant for corn (P > F = 0.16), sorghum (P > F = 0.113), and soybean (P > F = 0.491) although there were significant residue × tillage interactions. Tillage system was not significant (P > F = 0.125) for soybean yields, but plowing significantly (P > F = 0.0001) increased both corn and sorghum yields. Mean corn yields were 13% less for the no‐till system than for the moldboard plow system. However, no‐till corn yield differences were not significant (P > F = 0.255) when plant population (a possible measure of planter performance) and percent green rating (a measure of weed control) were included as covariates. Our recommendation for the first year of grain crop production on smooth brome CRP land is to shred the residue and plant soybean in a no‐till system.
Performance of Site‐Specific Nutrient Management for Irrigated Rice in Southeast China
Authors: Wang Guanghuo , Dobermann Achim , Witt Christian , Sun Quingzhu , Fu Rongxing
Published: July 2010

Rice (Oryza sativaL.) yield increases in Zhejiang, China have slowed since 1985 despite the increasing use of hybrids and fertilizers. On‐farm experiments at 21 sites were conducted to evaluate a new approach for site‐specific nutrient management (SSNM). Field‐ and season‐specific N–P–K applications were calculated by accounting for the indigenous nutrient supply, yield targets, and nutrient demand as a function of the interactions between N, P, and K. Nitrogen applications were fine‐tuned based on season‐specific rules and field‐specific monitoring of crop N status. The performance of SSNM was tested for four successive rice crops. Compared with the current farmers' fertilizer practice (FFP), average grain yield increased from 5.9 to 6.4 Mg ha−1while plant N, P, and K uptake increased by 8 to 14%. The gross return over fertilizer cost was about 10% greater with SSNM than with FFP. Yields were about 20% greater in late rice (hybrid cultivars) than in early rice (inbred cultivars), but SSNM performed equally better than FFP in both seasons. Improved timing and splitting of fertilizer N increased N recovery efficiency from 0.18 kg kg−1in FFP plots to 0.29 kg kg−1in SSNM plots. The agronomic N use efficiency (grain yield increase per kilogram fertilizer applied) was 80% greater with SSNM than with FFP. As defined in our study, SSNM has potential for improving yields and nutrient efficiency in irrigated rice. Future research needs to develop a practical approach for achieving similar benefits across large areas without field‐specific modeling and with minimum crop monitoring.
Uptake of Selected Nutrients by Temperate Grasses and Legumes
Authors: Brink Geoffrey E. , Pederson Gary A. , Sistani Karamat R. , Fairbrother Timothy E.
Published: July 2010

Temperate forages are used throughout the southeastern USA to provide feed for livestock when tropical and subtropical grasses are dormant and as a hay source. Long‐term utilization of broiler litter as a fertilizer in some areas of the region has elevated soil levels of P and micronutrients. Our objective was to compare P, Cu, and Zn uptake among temperate forage species from a Savannah fine sandy loam soil (fine‐loamy, siliceous, semiactive, thermic Typic Fragiudult) amended with litter under a single‐harvest system. Dry weight of ryegrass (Lolium multiflorum Lam.) herbage was greater than all other species except ball clover (Trifolium nigrescens Viv.) in 1997 and oat (Avena sativa L.) in 1998. Clovers were susceptible to Sclerotinia crown and stem rot (Sclerotinia trifoliorum Erikss.) that reduced plant density, vigor, and dry herbage weight. Although forage P concentration of all species was similar to or greater than ryegrass, only crimson clover (T. incarnatum L.) had P uptake equal to ryegrass during both years (mean of 23.4 kg ha−1). This was attributed to the high correlation between dry herbage weight and P uptake (r = 0.95 and 0.89 in 1997 and 1998, respectively). Legumes typically had greater Cu and Zn concentrations than ryegrass, but only crimson clover and hairy vetch (Vicia villosa Roth) had comparatively greater Cu and Zn uptake during both years. The combination of desirable agronomic traits and nutrient uptake capacity make annual ryegrass a superior temperate forage species for use in southeastern pastures fertilized with broiler litter.
Biomass Production of ‘Alamo’ Switchgrass in Response to Nitrogen, Phosphorus, and Row Spacing
Authors: Muir James P. , Sanderson Matt A. , Ocumpaugh William R. , Jones Ronald M. , Reed Roderick L.
Published: July 2010

Management practices for biomass production of bioenergy grasses may differ from management for forage. Our objective was to determine the yield and stand responses of ‘Alamo’ switchgrass (Panicum virgatum L.) to N and P fertilization as affected by row spacing. A combination of five rates each of N and P were applied to plots during 1992 to 1998 at Stephenville, TX and 1993 to 1995 at Beeville, TX. Three row‐spacing treatments were applied as subplots. Biomass production was determined each year with a single harvest in late summer. Tiller density and tiller mass were measured during 1993 to 1996 at Stephenville. Biomass production was not influenced by the addition of P. Biomass production response to N at Beeville was greater in narrow rows than wide rows during the establishment year only. Biomass production responses to N were quadratic in 5 of 7 yr at Stephenville and linear at Beeville. A maximum yield of 22.5 Mg ha−1 occurred during 1995 at Stephenville at 168 kg N ha−1. Lodging occurred at both locations but only at the 224 kg N ha−1 rate. Tiller density and mass increased as row width increased. Tiller mass also increased with increasing N fertility at Stephenville. This response was more important in determining biomass production than was tiller density. Average biomass production at 168 kg N ha−1 yr−1 was 14.5 and 10.7 Mg ha−1 yr−1 at Stephenville and Beeville, respectively. Biomass production without applied N tended to decline over the years. Our data indicated that switchgrass biomass production is sustainable at Stephenville only with the application of at least 168 kg N ha−1 yr−1, but P application and row spacing are not crucial.
GGEbiplot—A Windows Application for Graphical Analysis of Multienvironment Trial Data and Other Types of Two‐Way Data
Authors: Yan Weikai
Published: July 2010

Plant breeding trials produce quantities of data and finding the useful information within that data has historically been a major challenge of plant breeding. A recently developed graphical data summary, called GGEbiplot, can aid in data exploration. GGEbiplot is a Windows application that performs biplot analysis of two‐way data that assume an entry × tester structure. GGEbiplot analyzes the data and outputs the results as an image, and it also produces an interactive show of the data. It allows interactive visualization of the biplot from various perspectives. A multienvironment trial data set, in which cultivars are entries and environments are testers, was used to demonstrate the functions of GGEbiplot. These include but are not limited to: (i) ranking the cultivars based on their performance in any given environment, (ii) ranking the environments based on the relative performance of any given cultivar, (iii) comparing the performance of any pair of cultivars in different environments, (iv) identifying the best cultivar in each environment, (v) grouping the environments based on the best cultivars, (vi) evaluating the cultivars based on both average yield and stability, (vii) evaluating the environments based on both discriminating ability and representativeness, and (viii) visualizing all of these aspects for a subset of the data by removing some of the cultivars or environments. GGEbiplot has been applied to visual analysis of genotype × environment data, genotype × trait data, genotype × marker data, and diallel cross data.
Seasonal Variation in Linear Increase of Taro Harvest Index Explained by Growing Degree Days
Authors: Lu Hsiu-Ying , Lu Chun-Tang , Chan Lit-Fu , Wei Meng-Li
Published: July 2010

Selecting plants with high harvest index (HI) can increase corm yield in wetland taro [Colocasia esculenta (L.) Schott]. Planting time, however, affects the response of HI during the linear increase phase, with temperature being the most important factor affecting taro growth. The objectives of this research were to quantify the relationship of calendar days after planting (DAP) and growing degree days after planting (GDD) to HI in taro and to compare their ability to explain seasonal variation in the linear increase of HI. Data from six planting months of field‐grown taro across a 3‐yr period were collated to investigate the linear increase in HI. The DAP and GDD (with base temperature of 17°C) were included as independent variables to analyze the three‐phase piecewise linear function with HI. Piecewise linear functions based on either DAP or GDD fitted well. The responses during the linear increase phase of HI were, however, more stable across years for the GDD model. Moreover, the model based on GDD was superior to DAP for explaining the seasonal variation of HI in taro. These results indicate that the GDD model is a useful approach for determining weather–crop growth relations in taro. Information gained in this study should help relate phenological responses to seasonal variation in taro.
Maize and Sorghum Simulations with CERES‐Maize, SORKAM, and ALMANAC under Water‐Limiting Conditions
Authors: Xie Yun , Kiniry James R. , Nedbalek Vernon , Rosenthal Wesley D.
Published: July 2010

While crop models often are tested against long‐term mean grain yields, models for aiding decision making must accurately simulate grain yields in extreme climatic conditions. In this study, we evaluated the ability of a general crop model (ALMANAC) and two crop‐specific models (CERES‐Maize and SORKAM) to simulate maize (Zea mays L.) and sorghum [Sorghum bicolor (L.) Moench] grain yields in a dry growing season at several sites in Texas. The root mean square deviation values were 0.36 Mg ha−1 for sorghum with ALMANAC, 0.71 for sorghum with SORKAM, 0.56 for maize with ALMANAC, and 0.83 for maize with CERES‐Maize. For maize, values for coefficient of determination (r2) between measured and simulated grain yields were 0.95 for ALMANAC and 0.88 for CERES‐Maize. For sorghum, r2 values were 0.86 for ALMANAC and 0.45 for SORKAM. ALMANAC and SORKAM should be useful tools to simulate dryland sorghum in drought, as indicated by their root mean square deviation values of <0.8 Mg ha−1. The mean errors for irrigated maize were 2.0% for CERES and 6.2% for ALMANAC. For dryland maize, mean errors were 6.2% for ALMANAC and −2.2% for CERES. In CERES, simulated leaf area index (LAI) and kernel weight appeared to be overly sensitive to drought stress. Further study on the response of LAI and kernel weight to drought in CERES would be valuable. The soil, weather, and crop parameter data sets developed for this study could be useful guidelines for model applications in similar climatic regions and on similar soils.
Competitiveness of Semidwarf Upland Rice Cultivars against Palisadegrass (Brachiaria brizantha) and Signalgrass (B. decumbens)
Authors: Fischer Albert J. , Ramírez Hector V. , Gibson Kevin D. , Da Silveira Pinheiro Beatriz
Published: July 2010

When savannas in Latin America are brought into cultivation, rice (Oryza sativa L.) can be sown with the perennial grasses palisadegrass [Brachiaria brizantha (Hochst. ex A. Rich) Stapf] and signalgrass (B. decumbens Stapf) to harvest a grain crop while establishing a pasture to suppress weeds and provide grazing in subsequent years. However, these Brachiaria spp. can reduce upland rice yields. Rice cultivars need to be competitive with Brachiaria spp. to maintain yields but must allow Brachiaria spp. sufficient growth for pasture establishment. Field studies were conducted during 1994 and 1995 on a Typic Haplustox oxisol soil in the Eastern Plains of Colombia to evaluate the competitiveness of upland rice cultivars and to identify rice traits for competitiveness. Ten (1994) and 14 (1995) upland rice cultivars were grown with and without signalgrass in 1994 and palisadegrass in 1995. Rice cultivars differed substantially in their competitiveness. Rice yield losses ranged from 18 to 55%, and Brachiaria aboveground biomass ranged from 1.4 to 3.2 Mg ha−1 dry mass. Competition for light was critical; rice photon flux density interception, leaf area index [≥45 d after emergence (DAE)], and number of tillers (≥60 DAE) were correlated with competitiveness. No tradeoff between high yield potential and competitiveness was detected in these upland rice cultivars. Early maturity of rice is a desired characteristic for the rice–Brachiaria spp. association. The development of more‐competitive cultivars appears to be a viable approach for reducing herbicide dependency and improving profitability of Latin American rice–pasture intercropping systems.
Row Width and Plant Density Effects on Corn Grain Production in the Northern Corn Belt
Authors: Widdicombe William D. , Thelen Kurt D.
Published: July 2010

Continued genetic improvement in the ability of hybrid corn (Zea mays L.) to withstand high plant density stress requires agronomists to periodically reassess optimal plant density and row width. Furthermore, the optimal plant density level and row width for corn grain yield may vary with location, primarily latitude, in the Corn Belt. This study was conducted to evaluate corn grain yield, harvest moisture, test weight, and stalk lodging with modern corn hybrids, as affected by row width and plant density in the northern Corn Belt. At six locations in 1998 and 1999, four hybrids differing in relative maturity, ear type, plant height, and leaf orientation were planted at row widths of 76, 56, and 38 cm and five plant density levels ranging from 56000 to 90000 plants ha−1. Plots were arranged randomly in a split‐split plot configuration. Results show that corn grain yield increased 2 and 4% and harvest moisture decreased by a factor of 2.1% when row width was narrowed from 76 cm to 56 cm and 38 cm, respectively. The highest plant density evaluated, 90000 plants ha−1, had the highest grain yield. Grain moisture decreased and grain test weight increases slightly as plant density increased. A hybrid × row width interaction was not observed indicating that hybrids that yield well in conventional 76‐cm row systems will also yield well in narrow row systems.
Effect of Irrigation and Nutrition of Copper and Molybdenum on Egyptian Clover (Trifolium alexandrniumL.)
Authors: El‐Bably A. Z.
Published: July 2010

The present investigation was conducted at Sakha Agricultural Research Station, Kafr El‐Sheikh, Egypt, in two growing seasons of 1998–1999 and 1999–2000 to estimate the productivity of Egyptian clover (Trifolium alexandrniumL.) as influenced by number of irrigations and addition of the micronutrients Cu and Mo. Irrigation treatments were one, two, and three irrigations between cuttings while micronutrient treatments were 0.95 kg ha−1copper sulfate and 0.95 kg ha−1ammonium molybdate at a rate of 950 L ha−1The combined analysis indicated that three irrigation events between cuttings significantly increased total cuttings of fresh and dry yields (FY and DY, respectively) to 104.14 and 19.48 t ha−1, respectively. On the other hand, it decreased water use efficiency (WUE). As for foliar application, results showed that 0.95 kg ha−1ammonium molybdate significantly increased seasonal total of FY, DY, and WUE by 16.48, 18.63, and 17.65%, respectively. Water consumptive use values were 59.62, 48.98, and 37.98 cm, over both seasons, for three, two, and one irrigation time(s) between cuttings, respectively. Under shortage of irrigation water, single irrigation between cuttings could be useful because it produced 91.97 and 16.75 t ha−1FY and DY, respectively; consumed 37.98 cm (170 d)−1; and gave higher WUE of 440.9 kg of dry matter (DM) ha−1cm−1water consumed compared with irrigation three times, which produced 104.14 and 19.48 t ha−1GY and DY, respectively; consumed 59.62 cm (170 d)−1; and gave lower WUE of 326.5 kg of DM ha−1cm−1water consumed, over both seasons.
Nitrogen and Dry Matter Distribution by Culm and Leaf Position at Two Stages of Vegetative Growth in Winter Wheat
Authors: Wilhelm W. W. , McMaster G. S. , Harrell D. M.
Published: July 2010

Knowledge of N and assimilate partitioning in wheat (Triticum aestivum L.) improves management efficacy and crop model development. Our purpose was to describe N and dry matter distribution during vegetative growth of blades, sheaths, and internodes on four culms. Winter wheat grown at the Colorado State University Horticultural Farm was sampled at Haun Stage 5 and jointing. Samples were dried, weighed, and analyzed for N. As the canopy developed and older tissue contributed more of total tissue, N concentration decreased although N mass and dry weight increased. Dry matter and N mass decreased from MC to T1 and T2 to T11, while the reverse order was found for N concentration. Dry weight and N mass decreased as culm order increased (culm age decreased), because phytomers were smaller and fewer existed. Nitrogen concentration had the opposite trend because new tissue contained about 40 g N kg−1 but declined as the tissue aged to 30 g N kg−1. Initial growth of all tissues had concentrations >50 g N kg−1 and at senescence declined to 19 g N kg−1. Phytomer positions on different culms tended to have similar N concentrations while identical phytomers on primary tillers tended to have greater dry weights than those on the MC and secondary tillers. Phytomers tended to increase in N concentration and mass and dry weight acropetally. Results show that viewing the canopy as the interplay of appearance, growth, interaction, and senescence of culms or phytomers can increase understanding of canopy N and dry weight dynamics.
Yield, Quality, and Persistence of Grazing‐ and Hay‐Type Alfalfa under Three Harvest Frequencies
Authors: Kallenbach R.L. , Nelson C.J. , Coutts J.H.
Published: July 2010

Producers in the lower Midwest often plant grazing‐type alfalfa (Medicago sativa L.) cultivars assuming they can withstand frequent hay harvests. However, little research has examined the long‐term effects of frequent hay harvests on grazing‐type compared with hay‐type alfalfa. Our objective was to determine how cultivar‐type and harvest frequency change long‐term alfalfa yields, quality, and stand persistence. ‘Alfagraze’ (grazing‐type), ‘Pioneer 5373’ (modern, multipest resistant hay‐type), and ‘Cody’ (older hay‐type) alfalfa were seeded on 1 Apr. 1994, near Mt. Vernon, MO. Cultivars were main plots, and four, five, or six harvests before 15 September (42, 34, and 28 d between harvests, respectively) were subplots in a randomized complete block in a split‐plot arrangement. Cumulatively, over 5 yr, Pioneer 5373 produced 6% (2.8 Mg ha−1) more forage than Alfagraze and 10% (5.0 Mg ha−1) more than Cody. Alfalfa harvested four times yielded 7% (0.8 Mg ha−1) more per year than when harvested five times, and 28% (3.1 Mg ha−1) more than when harvested six times. Alfagraze and the hay‐types yielded equally when harvested six times. Alfagraze usually had equal or lower detergent fiber, and equal or greater crude protein (CP) concentrations than other cultivars. Harvesting more frequently improved forage quality but had little impact on plant density. We concluded that a grazing‐type, like Alfagraze, does not show a yield or persistence advantage over a modern hay‐type under frequent hay harvest regimes in the lower Midwest. However, the grazing‐type used in this study often had superior forage quality.
Population Dynamics and Distribution of Root Lesion Nematode (Pratylenchus penetrans) over a Three‐Year Potato Crop Rotation
Authors: Morgan Gaylon D. , MacGuidwin Ann E. , Zhu Jun , Binning Larry K.
Published: July 2010

Population dynamics of Pratylenchus penetrans Cobb (root lesion nematode) were investigated in commercial potato (Solanum tuberosum L.) fields in the Central Sands of Wisconsin to test the hypothesis that cultural and management practices influence spatial distribution and temporal stability of nematodes over a 3‐yr crop rotation. From 1998 to 2000, P. penetrans populations were investigated in fumigated and unfumigated commercial potato fields and in the subsequent rotational crops {corn (Zea mays L.) or soybean [Glycine max (L.) Merr.] and fresh market vegetables} and winter cereal cover crops. Pratylenchus penetrans populations were quantified in each field using a 0.5‐ha uniform sampling grid. Traditional and geostatistical methods and interpolation maps were used to estimate the spatial distribution and temporal stability of nematode populations within each field and crop. In fumigated and unfumigated fields, the mean populations increased as the rotation progressed (potato→corn→vegetable). Population densities of P. penetrans increased more during the corn crop than potato crop. According to the Index of Dispersion, P. penetrans were aggregated (clumped) in all unfumigated fields; however, aggregation was only detectable in the fumigated fields 2 or 3 yr following soil fumigation. Geostatistical methods identified aggregation in only one field. In many cases, higher nematode populations occurred near tillage implement entry locations into each field. Nematode densities alone were not highly correlated with potato yields, corn yields, soil moisture, or soil pH but were consistently correlated with Verticillium wilt (Verticillium dahliae Kleb.) symptoms in unfumigated fields. Populations expressed more temporal stability in unfumigated fields than in fumigated fields.
Deltasoy—An Internet‐Based Soybean Database for Official Variety Trials
Authors: Zhang Lingxiao , Qi Wanwen , Su Ling , Whisler Frank
Published: July 2010

Official variety trial (OVT) information in soybean [Glycine max (L.) Merr.]‐producing states is critical to soybean growers in decision‐making processes. Most soybean‐producing states in the USA have their own soybean research web sites with information relating to the soybean variety trials. A web‐based database system has been developed that can help soybean growers and researchers access the most recent OVT information quickly and in response to their specific interests. This new system also summarizes past research results systematically and has the potential to link ongoing research in related areas of soybean production, modeling, and other research efforts. Microsoft Access, along with other computer languages [C++, common gateway interface, Standard Query Language (SQL)], were used in building this database. The database uses Mississippi OVT data, including yield, location, and disease information. This database has the potential to extend its capability by adding more information from variety trials of other states and other crops. Therefore, it should be a helpful tool for soybean producers and researchers in Mississippi as well as other interested parties.
Tillage Effects on Water and Salt Distribution in a Vertisol during Effluent Irrigation and Rainfall
Authors: Ben‐Hur Meni , Assouline Shmuel
Published: July 2010

Most previous investigations of the effects of irrigation with a moving sprinkler irrigation system (MSIS) on surface runoff have studied in loess soils. However, Vertisols have different properties than loess soils and therefore could behave differently during sprinkler irrigation. The objectives were to determine the runoff, soil loss, and water and salt distribution in a Vertisol field under secondary effluent irrigation with an MSIS while subjected to various tillage practices and rainfall conditions. The experimental site was a cotton (Gossypium hirsutum L.) field located in the Yizre'el Valley, Israel. Two tillage treatments were studied: local practice (control) and microbasins. Water content and salt concentration in the soil and seed cotton yield and plant height were measured at various positions along the slope during the irrigation season, and the water and salt content were measured at one position during the rainy season. The average runoff and soil loss (from a 5.5‐m−2 plot) per irrigation event for the entire irrigation season were 12.5 mm and 64.6 g m−2, respectively, in the control and 3.3 mm and 13 g m−2, respectively, in the microbasin treatment. The water, salt, and cotton yield distributions along the slope were quite uniform in the two treatments. The high infiltration of the runoff through cracks limited the effects of the runoff downhill flow on the water and salt distribution along the slope. At the end of the irrigation season, the average electrical conductivity (EC) down to 1.5‐m depth was ≈2.3 dS m−1 in both treatments. After the rainy season, the average EC in the control was 0.6 dS m−1 in the 0‐ to 0.6‐m depth range and 3.4 dS m−1 in the 0.6‐ to 1.5‐m depth range. Conversely, in the microbasins, the salt was leached to below 1.5‐m depth by rainfall. However, further study is needed to determine the salt distribution in the areas between the microbasins.
Near‐Infrared Reflectance Spectroscopy Analysis of Phosphorus in Sugarcane Leaves
Authors: Chen Ming , Glaz Barry , Gilbert Robert A. , Daroub Samira H. , Barton Franklin E. , Wan Yongshan
Published: July 2010

Rapid screening for high leaf P concentration may help sugarcane (interspecific hybrids of Saccharum spp.) growers in the Everglades Agricultural Area reduce P in discharge water, an important component of Everglades restoration. The purpose of this study was to evaluate near‐infrared reflectance spectroscopy (NIRS) as a potential tool to analyze sugarcane leaf P concentration. Local calibrations for samples with similar spectral characteristics were calculated using modified partial least‐squares regression for the following categories: parents, offspring, fertilizer rate, and water table. Additionally, global calibrations were calculated for 11 groupings of these local categories. Analyses for much of the study found that the most accurate local calibration was that of fertilizer rate, with R2 = 0.90 and ratio of standard deviation (s) to standard error of cross validation = 2.17. However, further multiplicative scatter correction of spectral data and the elimination of unneeded wavelength segment points by Martens Uncertainty regression with software that became available later in the study resulted in nearly perfect prediction equations, with r2 = 0.99 and ratio of s to standard error of prediction ≥ 32.0 for the offspring local equation and the parents + fertilizer rate + water table global equation. These results show that researchers not obtaining calibrations at desired levels of accuracy with NIRS should try to eliminate unneeded wavelength segments. Use of NIRS is proposed as a tool to provide rapid, accurate measurements of sugarcane leaf P content for characterizing commercial cultivars and for screening for high‐P cultivars in breeding programs.
Soybean Responses to Potassium Placement and Tillage Alternatives following No‐Till
Authors: Yin Xinhua , Vyn Tony J.
Published: July 2010

More information is needed about optimum potassium (K) fertilizer placement for soybean [Glycine max (L.) Merr.] production in no‐till fields. This study was conducted at two locations in Ontario, Canada, from 1998 to 2000 to examine soybean responses to K placement methods and tillage systems on soils with a 5‐ to 7‐yr no‐till history and medium to high soil‐test K levels. Fertilizer K treatments (15‐cm deep banding in fall, 7.5‐cm shallow banding in spring, surface broadcast in fall, and a zero K control) were compared in three conservation tillage systems (fall zone‐till, fall disk, and no‐till). The K fertilizer rate was 100 kg ha−1 for all but the control treatment. Soybean row widths (76 or 38 cm) varied with tillage systems, and soybean rows were positioned above K fertilizer bands if applicable. Yield responses to K application occurred in the fall zone‐till and no‐till systems on some medium‐ to high‐testing soils. There was no significant leaf K or seed yield advantage to band placement compared to surface broadcasting, and to fall zone‐till or fall disk systems relative to no‐till, for soybean of similar row width. Neither leaf K nor seed yield was negatively affected by degree of soil K stratification. Despite vertical soil K stratification after continuous no‐till, there was no significant leaf K or yield benefit to replacing narrow‐row, no‐till soybean systems (involving surface K fertilizer application) with wide‐row zone‐till or no‐till systems (involving deep banding of K), or with narrow‐row, fall disk systems (involving surface‐applied, but tillage‐incorporated K).
Canopy Height and Nitrogen Supplementation Effects on Performance of Heifers Grazing Limpograss
Authors: Newman Y. C. , Sollenberger L. E. , Kunkle W. E. , Chambliss C. G.
Published: July 2010

Leaf percentage and herbage crude protein (CP) are greater in the upper than lower half of limpograss [Hemarthria altissima (Poir.) Stapf & Hubb.] canopies; thus, canopy height may affect N status and cattle (Bos spp.) weight gain. Average daily gain (ADG) of beef heifers and sward characteristics were measured on continuously stocked limpograss pastures grazed to heights of 20, 40, and 60 cm, with cattle receiving 0 or 0.8 kg d−1 of a 44% CP corn (Zea mays L.)–urea mixture. Cattle grazing 20‐ and 60‐cm pastures increased ADG by 200 g when supplemented (to ≅ 590 g); however, cattle grazing 40‐cm pastures tended to have greater ADG when not supplemented (644 g) vs. when supplemented (536 g). Herbage mass and allowance increased with increasing canopy height, partially explaining greater ADG of unsupplemented cattle grazing 40‐ vs. 20‐cm swards. The 40‐cm canopies also had lower herbage bulk density, allowing greater opportunity for selection of leaf than in 20‐cm canopies. Stocking rate increased linearly (5.9–8.5 head ha−1) as canopy height decreased from 60 to 20 cm, and gain per hectare increased linearly with decreasing canopy height for both unsupplemented (161–352 kg) and supplemented (273–378 kg) treatments. Data suggest stubble height is an important determinant of heifer performance. A 40‐cm canopy height may be near optimum because of greater herbage allowance and opportunity to select leaf than in dense 20‐cm canopies and less trampling and greater leaf proportion and accessibility than in 60‐cm swards.
Water Use Patterns of Grain Amaranth in the Northern Great Plains
Authors: Johnson Burton L. , Henderson Tracey L.
Published: July 2010

An understanding of water use is essential for evaluating the potential of new crops in areas where water is a limiting factor. This study was conducted to determine water use efficiency (WUE), depth of soil water extraction, and other agronomic characters of grain amaranth (Amaranthus spp.) produced in the northern Great Plains. Field experiments were conducted with four grain amaranth cultivars at Prosper, ND, during the 1989 through 1992 growing seasons. Volumetric soil water content was monitored with a neutron probe at eight soil profile depths during each growing season. Significant differences among cultivars were observed for biomass yield, biomass WUE, plant height, and harvest index (HI). The year × cultivar interaction was significant for grain yield, grain WUE, plant height, and HI. Maximum effective depth of soil water extraction was 122 cm in the less water‐stressed years, 1990 and 1992, and 154 cm in the more water‐stressed years, 1989 and 1991. Cultivars did not differ significantly for depth of soil water extraction or total water use (TWU). Maximum effective rooting depth occurred at early to full anthesis in 1989, 1990, and 1991 and at the late anthesis to grain fill stages in 1992. Approximately 70 to 75% of TWU occurred by the end of anthesis. Mean TWU and grain WUE values were 267 mm and 5.9 kg ha−1 mm−1, respectively. Amaranth's apparent ability to respond to water stress by increasing rooting depth makes it a potentially useful crop in North Dakota where soil moisture conditions vary considerably among growing seasons.
Classification of Crop Yield Variability in Irrigated Production Fields
Authors: Dobermann A. , Ping J. L. , Adamchuk V. I. , Simbahan G. C. , Ferguson R. B.
Published: July 2010

Crop yield maps reflect stable yield patterns and annual random yield variation. Procedures for classifying a sequence of yield maps to delineate yield zones were evaluated in two irrigated maize (Zea mays L.) fields. Yield classes were created using empirically defined yield categories or through hierarchical or nonhierarchical cluster analysis techniques. Cluster analysis was conducted using average yield (MY), average yield and its standard deviation (MS), or all individual years (AY) as input variables. All methods were compared based on the average yield variability accounted for (RVc). Methods in which yield was empirically classified into three or four classes accounted for less than 54% of the yield variability observed and failed to delineate high‐yielding areas. Six to seven yield classes established by cluster analysis of MY accounted for 60 to 66% of the yield variability. Differences among cluster analysis methods were small for MY as data source. However, fuzzy‐k‐means clustering had lower RVc than other methods if used with the MS or AY data. The spatial fragmentation of yield class maps increased in the order MY < MS < AY. Univariate cluster analysis of mean relative yield measured for at least 5 yr should be used for yield classification in irrigated fields where six to seven classes appear to provide sufficient resolution of the yield variability observed. More research should be conducted to develop methods that result in spatially coherent yield zones and to understand differences between rainfed and irrigated environments in the importance of mapping yield goals for crop management.
Vernalization Studies with Pacific Northwest Wheat
Authors: Baloch D. M. , Karow R. S. , Marx E. , Kling J. G. , Witt M. D.
Published: July 2010

Lack of rain or excess soil moisture may create problems for fall sowing of winter cereals in the Pacific Northwest. Growers unable to plant in the fall question the potential for late winter sowings, which is determined to a large extent by cultivar vernalization requirement. This study was conducted to gain a better understanding of the vernalization requirement of winter wheat (Triticum aestivum L.) cultivars grown in the region and to determine if a tool could be developed for predicting latest winter sowing dates. A growth chamber–greenhouse procedure was developed to determine the relative vernalization requirement of new wheat cultivars. Twenty cultivars were sown in the field at intervals from early October through late March during the 1991–1993 cropping seasons. Accumulated heat units from sowing were used to determine vernalization days (VD). Heading date and yield were measured. Field results indicated that cultivars could be categorized in three groups—those with low, intermediate, and high vernalization requirements. Growth chamber–greenhouse results verified these groupings. Field data suggest that if 50% relative yield (late‐sown yield is 50% of that for the same cultivar when sown in fall or early winter) is acceptable, then cultivars with a low vernalization requirement can be sown with 60 VD expected after sowing while cultivars with a high vernalization requirement require 70 expected VD. If 70% relative yield is desired, all cultivars tested showed similar performance.
Soybean Nitrogen Contribution to Corn and Sorghum in Western Corn Belt Rotations
Authors: Varvel G. E. , Wilhelm W. W.
Published: July 2010

Increased N availability is often associated with the beneficial effects of rotating grain and legume crops. Our objective was to utilize yield response data from two long‐term studies to determine the amount of N supplied by soybean [Glycine max (L.) Merr.] for subsequent nonlegume crops in 2‐yr rotations. The experiments were located in eastern Nebraska (Mead) (rainfed) and central Nebraska (Shelton) (irrigated). Continuous corn (Zea mays L.) and soybean–corn cropping systems were present in both experiments while continuous sorghum [Sorghum bicolor (L.) Moench] and soybean–sorghum cropping systems were present at Mead only. Three N fertilizer rates were used for the study at Mead and five at Shelton. Nitrogen fertilizer replacement values were estimated using graphical and regression techniques. Results from both techniques indicated that corn in the rainfed experiment at Mead (20 yr) and irrigated experiment at Shelton (10 yr) obtained approximately 65 kg N ha−1 yr−1 from soybean in a 2‐yr rotation with soybean at both locations. Sorghum in the rainfed experiment at Mead (20 yr) obtained approximately 80 kg N ha−1 yr−1 from soybean in a soybean–sorghum rotation. Current fertilizer N applications based on fall or early‐spring soil tests used extensively in this area need to be reduced by these amounts for corn and sorghum grown in 2‐yr rotations with soybean when grown on medium‐ to fine‐textured soils in the western Corn Belt to reduce excess N available for loss and to reduce unnecessary input costs.
Environment and Harvest Time Affects the Combustion Qualities of Miscanthus Genotypes
Authors: Lewandowski I. , Clifton‐Brown J. C. , Andersson B. , Basch G. , Christian D. G. , Jørgensen U. , Jones M. B. , Riche A. B. , Schwarz K. U. , Tayebi K. , Teixeira F.
Published: July 2010

Miscanthus spp. are high‐yielding perennial C4 grasses, native to Asia, that are being investigated in Europe as potential biofuels. Production of economically viable solid biofuel must combine high biomass yields with good combustion qualities. Good biomass combustion quality depends on minimizing moisture, ash, K, chloride, N, and S. To this end, field trials at five sites in Europe from Sweden to Portugal were planted with 15 different genotypes including M. × giganteus, M. sacchariflorus, M. sinensis, and newly bred M. sinensis hybrids. Yield and combustion quality at an autumn and a late winter/early spring harvest were determined in the third year after planting when the stands had reached maturity. As expected, delaying the harvest by three to four months improved the combustion quality of all genotypes by reducing ash (from 40 to 25 g kg−1 dry matter), K (from 9 to 4 g kg−1 dry matter), chloride (from 4 to 1 g kg−1 dry matter), N (from 5 to 4 g kg−1 dry matter), and moisture (from 564 to 291 g kg−1 fresh matter). However, the delayed harvest also decreased mean biomass yields from 17 to 14 t ha−1. There is a strong interaction among yield, quality, and site growing conditions. Results show that in northern regions of Europe, M. sinensis hybrids can be recommended for high yields (yielding up to 25 t ha−1), but M. sinensis (nonhybrid) genotypes have higher combustion qualities. In mid‐ and south Europe, M. × giganteus (yielding up to 38 t ha−1) or specific high‐yielding M. sinensis hybrids (yielding up to 41 t ha−1) are more suitable for biofuel production.
ET_CSDLL
Authors: Donatelli Marcello , Stöckle Claudio O. , Nelson Roger L. , Bellocchi Gianni
Published: July 2010

ET_CSDLL (Evapotranspiration–CropSyst Dynamic Link Library) is a Microsoft (MS) COM (component object model) library containing routines to estimate reference crop evapotranspiration (ET0) following the guidelines of the FAO Irrigation and Drainage Paper no. 56 for implementing the Penman–Monteith (P‐M) equation. In addition, the Priestley–Taylor equation is also included for calculating ET0 for conditions where meteorological data are insufficient to apply the P‐M equation. The dynamic link library (DLL) can be used in MS Excel spreadsheets and in code developed using a visual MS Windows programming language. Examples are shown to illustrate the use of the DLL in MS Excel and MS Visual Basic applications.
Xylem Hydraulics and the Soil–Plant–Atmosphere Continuum: Opportunities and Unresolved Issues
Authors: Sperry John S. , Stiller Volker , Hacke Uwe G.
Published: July 2010

Soil and xylem are similar hydraulically. An unsaturated conductivity curve for soil is called a vulnerability curve for xylem—but the underlying physical basis is the same. Thus, any transport model that treats unsaturated soil conductivity would benefit by also incorporating the analogous xylem vulnerability curves. This is especially the case for crop plants, which as a group have relatively vulnerable xylem. Although the cohesion–tension mechanism for xylem transport has withstood recent challenges, a number of gaps remain in our understanding of xylem hydraulics. These include the extent and mechanism of cavitation reversal and thus hysteresis in the vulnerability curve, the structural basis for differences in air entry pressure (=cavitation pressure) for different xylem types, a quantitative model of xylem conductivity, and a mechanistic understanding of how stomata regulate plant water status. Improving the representation of xylem hydraulics in models of crop water use is necessary to achieve a mechanistic link between soil water availability and canopy water use. An important additional knowledge gap concerns the hydraulics of the living tissues of absorbing roots and transpiring leaves, which are more complex than in xylem and less amenable to mechanistic modeling at present.
Modeling Light Interception and Transpiration of Apple Tree Canopies
Authors: Green Steve , McNaughton Keith , Wünsche J. N. , Clothier Brent
Published: July 2010

Sap flow in the trunk of two different‐sized apple trees [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf. cv. Splendour/MM.106 and Braeburn/M.9] was measured using the compensation heat‐pulse method. Supporting measurements were made of the total photosynthetic photon flux (QP) and the total all‐wave radiation (QN) absorbed by each tree. These data were used to test the output from a three‐dimensional model of light interception that approximated the orchard as an array of nonoverlapping, truncated ellipsoids, with each tree having a uniform density of green leaves that were randomly distributed within the canopy volume. Experimental observations, together with model predictions, were used to demonstrate how transpiration responds to changes in the aerial environment. Model testing was rigorous in the sense that the model was compared against complete and independent data collected on the same time scale. Agreement between measured and modeled values was generally very good; all correlation coefficients were large (r2 > 0.95), and the linear relationship between measurements and simulations of QP, QN, and transpiration has a slope that was within 5% of 1:1. A sensitivity analysis revealed that light interception was influenced most by changes in leaf area and leaf optical properties while transpiration was influenced most by changes in leaf area and leaf conductance. On a leaf‐area basis, results from the Braeburn tree (leaf area = 8.65 m2) were very similar to those from the larger Splendour tree (leaf area = 35.5 m2). A smaller, more compact fruit tree is more efficient at intercepting the sun's energy, yet it may require more irrigation water per hectare to sustain productivity.
Model Evaluation by Comparison of Model‐Based Predictions and Measured Values
Authors: Gauch Hugh G. , Hwang J. T. Gene , Fick Gary W.
Published: July 2010

The appropriateness of a statistical analysis for evaluating a model depends on the model's purpose. A common purpose for models in agricultural research and environmental management is accurate prediction. In this context, correlation and linear regression are frequently used to test or compare models, including tests of intercept a = 0 and slope b = 1, but unfortunately such results are related only obliquely to the specific matter of predictive success. The mean squared deviation (MSD) between model predictions X and measured values Y has been proposed as a directly relevant measure of predictive success, with MSD partitioned into three components to gain further insight into model performance. This paper proposes a different and better partitioning of MSD: squared bias (SB), nonunity slope (NU), and lack of correlation (LC). These MSD components are distinct and additive, they have straightforward geometric and analysis of variance (ANOVA) interpretations, and they relate transparently to regression parameters. Our MSD components are illustrated using several models for wheat (Triticum aestivum L.) yield. The MSD statistic and its components nicely complement correlation and linear regression in evaluating the predictive accuracy of models.