bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Foliar and Preplant Applied Nitrogen Fertilizer for Sugar Beet
Authors: Lamb J. A. , Moraghan J. T.
Published: July 2010

Leaf canopies of sugar beet (Beta vulgaris L.) grown in the Red River Valley of Minnesota and North Dakota sometimes display midseason (July) symptoms of N deficiency. The influence of in‐season foliar N applications on sugar beet grown under non‐irrigated conditions on a Wheatville loam (coarse silty over clayey, frigid Aeric Calciaquoll) with low and medium levels of soil N fertility was studied for 3 yr. A combination of eight soil and foliar treatments were investigated. The soil treatments were (i) soil NO−3 −N in the 0– to 60– cm depth of soil in the previous autumn (45 kg ha−1 in the 1986 and 1987 experiments, and 78 kg ha−1 in the 1988 experiment), and (ii) the above soil NO−3 −N levels plus sufficient fall‐applied urea‐N to give the equivalent of 157 kg N ha−1. In‐season foliar‐N treatments, using an urea‐NH4NO3 solution (28‐0‐0), were applied in 22 kg N−1 increments on 1 July, 15 July, and 1 August to give total foliar‐N treatments of 0, 22, 44, and 66 kg N ha−1 at both levels of soil‐N fertility. Overall, the use of foliar N application did not effect root yield and extractable sugar per hectare in 2 of the 3 yr. In one year, 1986, it did increase root yield by 5.2 Mg ha−1 and extractable sugar by 0.9 Mg ha‐t under N deficient conditions with no differences occurring under adequate N nutritional levels. There was a significant increase in both root yield and extractable sugar per hectare in 1986 and 1987 as a result of fall applied fertilizer N but not in 1988. If soil moisture conditions are favorable for plant growth such as in 1986, the use of a mid season foliar N application may be beneficial in N deficient situations.
Management and Environment Effects on Dry Matter Yields of Three Brassica Species
Authors: Wiedenhoeft M. Hagemann
Published: July 2010

Brassica crops have potential use as a forage during summer, fall, and early winter months. The influence of planting date and harvest date on the initial and regrowth herbage yields for three Brassica species: rape (B. napus L., ‘Winfred’ in 1987 and ‘Emerald’ in 1988 and 1989), turnip (B. rapa L., ‘Purple Top’), and a turnip hybrid (B. rapa × B. pekinensis L., ‘Tyfon’) were investigated. The species were planted in late May to early June, late June to early July, and late July to early August in 1987, 1988, and 1989. Herbage yields before grazing were taken 64, 76, or 85 d after planting. The remaining herbage was allowed to regrow for 60, 70, or 80 d and then harvested. Averaged over planting dates, harvest dates, and species, initial and regrowth herbage dry matter yields were 3.4 and 1.2 Mg haha−1, respectively. The turnip hybrid produced the greatest amount of total herbage yield, 4.5 Mg haha−1, followed by the rape species, 4.1 Mg haha−1. The total herbage yield, 2.7 Mg ha−1, for the turnip species was low because there was little regrowth. The herbage yields for 1987 and 1988 were not significantly different; 1989 yields were much lower, probably due to the wet climate conditions and high weed population. The earliest planting date produced the greatest herbage yields, followed by the mid‐summer planting date. Because of cold temperatures and short days no regrowth herbage was produced from the late summer plantings. Forage Brassica crops could provide adequate herbage yields during the late summer months and well into early winter months, thereby reducing the need for purchased feed.
Water Use, Intercepted Radiation, and Soil Temperature of Skip‐Row and Equidistant‐Row Barley
Authors: Sharratt B. S.
Published: July 2010

Cropping systems are sought in the subarctic that improve the plant growing environment for sustained and diversified production of crops. This study assessed whether microclimate and water use of barley (Hordeum vulgare L.) could be altered in the subarctic by crop row configuration and fertilizer placement. Treatments established at Fairbanks, AK, included equidistant‐row planting (0.18‐m equidistant rows) with N banded between alternate rows or broadcast, and skiprow planting (skipping every third row of equidistant rows) with N banded between the closely spaced rows or broadcast. Crop water use, net and reflected radiation, interception of photon flux density (PFD), and soil temperatures were monitored during 1987 through 1989. Banding N resulted in a higher water‐use efficiency (WUE) than did broadcasting N in 1989 but not 1988. Seasonal water use was equal among treatments, although higher leaf area index (LAI) for equidistant‐ row barley suggested less evaporation and greater transpiration than for skip‐row barley. Equidistant‐row barley intercepted 5% more PFD at heading, resulting in part from higher canopy reflectance. Skip‐row barley, however, intercepted more PFD per unit leaf area. Midday net radiation was 3% higher and midday soil temperatures at 0.01 m in the interrow were as much as 5 °C higher for skip‐row barley. In this subarctic environment, barley grown in equidistant rows appeared to utilize water more effectively in transpirational processes and to intercept more PFD for improving production efficiency compared to skip‐row planting.
An Inexpensive Thermocouple Multiplexing Device
Authors: Kvien C. K. , Hook J. E. , Thomson S. J. , Smith M. C.
Published: July 2010

The expense of monitoring large numbers of thermocouples has constrained many research and development projects. We developed an inexpensive multiplexing device which allows 640 or more thermocouples to be accessed from a microcomputer. The multiplexing unit is connected to a microcomputer expansion box equipped with a 16‐channel digital input/output (I/O) board and a preamp connected to an analog‐to‐digital (A/D) converter with cold junction compensation. A BASIC program controls the sequencing of each of the 640 channels and storage of information on the microcomputer's disk system. Temperatures measured through the system were accurate to ± 1 °C when channel switching intervals of 1 s or more were used. Temperature at the thermocouple junctions within the multiplexing unit does not significantly affect the observations. We found the device suitable for monitoring temperatures by thermocouples, and the programming gave us complete flexibility over timing and selection of thermocouples read. The multiplexing capability reduced the amount of expensive thermocouple wire needed for sensing at remote sites.
White Clover Response to Grazing Method
Authors: Brink G. E. , Pederson G. A.
Published: July 2010

Grazing management is a major factor influencing white clover (Trifolium repens L.) growth. Our objective was to determine the response of white clover cultivars differing in leaf size to grazing method (continuous vs. rotational stocking) using cattle (Bos spp.). In each of 2 yr, a predominantly tall fescue (Festuca arundinacea Schreb.) sod on a Savannah fine sandy loam (fine‐loamy siliceous, thermic Typic Fragiudult) was oversown in September with ‘Grasslands Huia’ (medium‐small leaf), ‘Louisiana S‐1’ (medium‐large leaf), and ‘Regal’ (large leaf) white clover. From March to August of the following year, plots of each cultivar were stocked continuously (3‐ to 5‐cm stubble) on rotationally (grazed to 5‐cm stubble every 35 to 38 d). Clover growth was measured prior to rotational grazing and stolon survival was determined in November. When precipitation during the grazing season was 59% above normal, grazing method had no influence on mean single leaf area, stolon dry weight, and stolon growing point density of white clover. In contrast, continuous stocking reduced these responses when precipitation was 32% below normal the following year. Cultivar ranking for mean single leaf area was generally the same as that for leaf size category: Grasslands Huia < Louisiana S‐1 < Regal. Although stolon length and growing point density were frequently greatest for Grasslands Huia, stolon survival of Grasslands Huia was no greater than that of the larger‐leafed cultivars. Despite varying effects of grazing method on growth and morphology, stolon survival of white clover was always greater under rotational stocking.
Relationships among Maximum Hypocotyl Length, Seed Weight, and Emergence in Sericea Lespedeza
Authors: Qui J. , Mosjidis J. A.
Published: July 2010

Poor seedling emergence is a major limitation in establishing sericea lespedeza [Lespedeza cuneata (Dumont de Courset) G. Don]. A series of controlled‐environment and field experiments were conducted to determine relationships among maximum hypocotyl length (MHL), seed weight, and percentage and rate of emergence in sericea lespedeza and to define criteria for selecting sericea lespedeza with good field emergence. The best time to distinguish MHL among sericea lespedeza genotypes was 9 d after emergence at alternating temperature of 26/22 °C (13/11 h). Seed weight and MHL were positively correlated, and both were positively correlated with field emergence. Selection for heavier‐seeded genotypes, which should tend to increase MHL, is easy. However, direct selection for greater MHL is required if the advantages of MHL especially when planting deep, are to be fully exploited.
Soil‐Applied Atrazine Alters Blue Grama Physiology and Indirectly Influences Soil Nitrogen
Authors: Knight W. G. , Morgan J. A. , Guenzi W. D. , Shoop M. C.
Published: July 2010

Atrazine [2‐chloro‐4‐(ethylamino)‐6‐(isopropylamino)‐s‐triazine] applied at sublethal concentrations to rangelands, has resulted in herbage production and/or enhanced plant N concentration of desirable warm‐season grasses beyond that expected from weed control alone. This investigation was conducted to determine whether this is a metabolically regulated plant response, the result of enhanced soil N availability via microbially mediated processes, or both. Aerobic and anaerobic laboratory incubation studies with an atrazine‐amended, rangeland soil indicated no direct effect of atrazine on soil‐mediated N transformations. Applications of atrazine to the same soil type in column‐lysimeters containing blue grama [Bouteloua gracilis (H.B.K.) Lag. ex Steud.] plants resulted in temporarily elevated soil NO3 concentrations and reduced NH4 concentrations in proportion to the different rates of atrazine applied (0, 0.5, 1.0, and 2.0 mg column−1). Applications of atrazine to soil containing blue grama plants initially inhibited photosynthesis and plant growth, and resulted in temporarily elevated soil NO5 concentrations and reduced NH4 concentrations. A strong inverse relationship was observed across the four atrazine treatments between soil available N and shoot N content, strongly suggesting that the dominant plant‐mediated effect of atrazine on soil N pools was elicited through atrazine's initial inhibitory effect on plant growth. A strong negative correlation between leaf photosynthesis rate and tissue NO3 levels across all four atrazine rates suggests that in addition to its negative effects on blue grama photosynthesis and growth, atrazine also impairs blue grama's ability to reduce NO3, enhancing the accumulation of plant tissue NO5 levels. We conclude that temporary changes in soil NO3 and NH4 concentrations from atrazine resulted indirectly from changes in plant growth and metabolism, and not from alterations in soil microbiological processes.
Accumulation and Redistribution of Dry Matter and Nitrogen by Spring Barley
Authors: Bulman Patrick , Smith Donald L.
Published: July 2010

The grain protein content of barley (Hordeum vulgare L.) is derived from the retranslocation of vegetative N, as well as from the continued uptake and assimilation of N during grain filling. Field trials were conducted at the E.A. Lods Agronomy Research Centre of McGill University on a a Bearbrook soil (fine, mixed, nonacid, frigid Humaquept) to study the effects of fertilizer N on grain and total plant N accumulation, vegetative N retranslocation, and post‐heading N uptake, and also to evaluate the importance of pre‐ and post‐anthesis N uptake in determining grain protein concentration (GPC). ‘Cadette’ and ‘Leger’, which are adapted feed types, and ‘Argyle’, an unadapted malting type, were grown with N rates of 0, 50, 100, 150 and 200 kg N ha−1 broadcast at seeding as NH4NO3. Two other treatments consisted of applying 100 kg N ha−1 at seeding and 50 kg N ha−1 as NH4NO3 (broadcast) or urea (foliar solution) 6 to 10 d after awn emergence. Retranslocation of vegetative N to the grain generally decreased with increased N application in 1988 and 1989, but not in 1990, when it increased. The proportion of vegetative N retranslocated to the grain decreased with increasing rates of fertilizer N in all years. Post‐heading N uptake and assimilation increased with fertilizer N, and appeared to be the major contributor of N to the grain. Cultivar differences in GPC were not related to differences in total N uptake, grain N, N harvest index, and apparent post‐heading N uptake or N retranslocation.
Estimating Spatial Variation in Analysis of Data from Yield Trials: A Comparison of Methods
Authors: Brownie Cavell , Bowman Daryl T. , Burton Joe W.
Published: July 2010

In large yield trials, variation in soil fertility (or, more generally, yield potential) can result in substantial heterogeneity within blocks and, thus, poor precision in treatment estimates. Precision may be improved using statistical analyses in which this spatial variation is accounted for in estimation of treatment or entry means. Three such types of spatial analysis are trend analysis, the Papadakis method, and analyses based on correlated errors models (which account for spatial variation through correlations between yields of neighboring plots). We reviewed the theory and empirical performance of these spatial analyses and compared them with the classical analyses. The classical analyses can be justified solely on the basis of randomization; spatial analyses depend on the model specified for the variation in yield potential. Performance depends on the polynomial used to describe yield potential in trend analysis, on the neighboring plots used to estimate fertility in the Papadakis analysis, and on the correlation structure in the correlated errors models. Empirical comparisons were based on data from 11 corn (Zea mays L.) yield trials and 1 soybean (Glycine max L.) trial, each showing evidence of heterogeneity within blocks. In comparison with the classical randomized blocks analysis, precision tended to be best for the trend and the trend plus correlated errors analyses, with the Papadakis method intermediate. Ranking of entries differed across analyses, because each analysis adjusts for spatial variation in a different way. Using a spatial analysis technique can improve precision, but selecting the most appropriate analysis for a given data set can be hard.
In‐Row Subsoiling and Potassium Placement Effects on Root Growth and Potassium Content of Cotton
Authors: Mullins Gregory L. , Reeves Donald W. , Burmester Charles H. , Bryant Hamilton H.
Published: July 2010

One method of correcting K deficiencies in cotton (Gossypium hirsutum L.) is by in‐row deep placement of K fertilizer. At present, the mechanisms involved in cotton yield response to deep placement of K have not been elucidated. A field study was conducted in 1990 and 1991 to evaluate root development and dry matter yield of cotton as affected by in‐row subsoiling and placement of K fertilizer. The experiment was located in central Alabama on a Norfolk fine sandy loam (fine‐loamy, siliceous, thermic Typic Kandiudult). Five treatments were compared: (i) check, without in‐row subsoiling; (ii) check, with in‐row subsoiling; (iii) 84 kg K ha−1 surface‐applied, without in‐row subsoiling; (iv) 84 kg K ha−1 surface‐applied, with in‐row subsoiling; and (v) 84 kg K ha−1 deep‐placed, in‐row. Penetrometer readings taken in 1991 demonstrated that the soil has a well‐developed traffic pan at a depth of approximately 15 to 38 cm. In‐row subsoiling disrupted the pan up to 25 cm away from the in‐row position. Root density measurements taken in‐row showed that root growth at depths > 20 cm was improved by in‐row subsoiling and K fertilization. Cotton root growth at depths > 20 cm was generally better for the treatment receiving the deep applied K. However, broadcast K in combination with in‐row subsoiling resulted in the highest productivity and K accumulation per plant. Results of this study suggest that, for cotton production in Alabama, deep placement of K is not superior to broadcast applications of K.
Legumes as Nitrate Catch Crops during the Dry‐to‐Wet Transition in Lowland Rice Cropping Systems
Authors: George Thomas , Ladha J. K. , Garrity Dennis P. , Buresh Roland J.
Published: July 2010

In tropical rice (Oryza sativa L.) lowlands, NO3‒ assimilation by plants during the transition from the dry to the wet season can preclude NO3‒ loss upon soil flooding and permit recycling of this N. In a 2‐yr field study in an Alfisol in the Philippines, we examined the role of legume crops and weeds during the dry‐to‐wet (DTW) transition in conserving and/or recycling soil NO3‒ that accumulated under varied dry‐season fallow management. During the May‐to‐July DTW transition, Sesbania rostrata (Bremek. & Oberm.), mungbean [Vigna radiata (L.) Wilczek], weedy, and weed‐free treatments were subplots in the February‐to‐May dry‐season mainplots of weedy, weed‐free, and frequently tilled fallows. Legume biological N2 fixation (BNF) was measured by 15N dilution. Depending on dry‐season management, the maximum extracted N (top 60‐cm layer) in the DTW transition ranged from 38 to 164 kg ha−1; this N was 62 to 96% NO3‒. Soil N uptake by weeds ranged from 31 to 46 kg N ha−1, that by mungbean from 29 to 80, and by S. rostrata from 46 to 125. The minimum estimates of DTW transition NO3‒ loss varied from none when plants were present to 107 kg N ha−1 in weed‐free fallows. Legume BNF partially offset NO3‒ loss, although increased soil NO3‒ decreased BNF‐N. Nitrogen fixed ranged from 37 to 63 kg N ha−1 by mungbean and 68 to 154 by S. rostrata. Harvest of mungbean caused negative BNF‐N contribution to the succeeding rice crop in a few cases. In lowland rice‐based cropping systems, weeds are effective in conserving soil N during the DTW transition, but legumes are more suitable nitrate catch crops because they allow the harvest of an economic product or the recycling of more N to a subsequent flooded rice crop.
Second‐Derivative Spectra for Estimating Crop Residue Cover
Authors: Su Haiping , Ransom Michel D. , Kanemasu Edward T. , Demetriades‐Shah Tanvir H.
Published: July 2010

Estimating crop residue is important for soil conservation and tillage management, and such estimates are used in determining conservation compliance with the U.S. Food Security Act of 1985. This study was conducted to (i) examine the relationship between derivative spectra of reflectance and oat (Avena sativa L.) residue covers and (ii) determine if the relation can be used to estimate oat residue cover from ground‐based reflectance measurements, using broad‐band (MMR) and high‐spectral‐resolution (SE590) instruments. A simple spectral model was proposed to interpret the interaction of solar radiation and crop residue with different soil backgrounds. A spectral derivative technique was applied to the field‐measured reflectance data to minimize the soil background noise and extract information about crop residue. SE590 wavelength at 402 nm and MMR Band 1 (450–520 nm) were the most sensitive. The second‐derivative value, defined as the derivative spectral index, strongly correlated (r2 ≥ 0.85) with oat residue cover using SE590 and MMR data. Four empirical regression equations were developed from the relationship between the derivative spectral index and the oat residue cover from four different data sets. Our results suggest that derivative spectral indices can be useful for estimating fresh oat residue in a disked field. The broad‐band data also can be used to calculate the derivative spectral index for detecting oat residue.
Rainfall‐Induced Leaching and Leaf Losses from Drying Alfalfa Forage
Authors: Smith D. Mark , Brown D. Murray
Published: July 2010

Efforts to construct models of forage yield and quality loss during the field drying of hay are hindered by a lack of quantitative information concerning several modes of loss. This study attempted to quantify leaching and rainfall‐induced leaf shatter from drying alfalfa (Medicago sativa L. ‘Magnum’) forage. A rainfall simulator was used to treat samples from four forage cuttings in 1989 and 1990 at four levels of tissue moisture between 760 and 150 g kg−1 (wet basis). Rainfall amounts of 0 (control), 5, 10, 15, and 20 mm were used at intensity levels of 20 and 40 mm h−1. Leaves lost due to rainfall were collected, samples of forage tissue were analyzed for quality and yield changes and samples of leachate water were collected from beneath hay samples for analysis. Results showed that leaf shatter is not directly induced by rainfall. Analysis of forage tissue showed that leaching of soluble dry matter caused dry weight losses and increases (P ≤ 0.05) in the proportion of fiber in tissue. Leachate analysis provided a more precise measure of leaching losses. Analysis of leachates for total dissolved and suspended dry matter demonstrated that leaching increases with rainfall amount and as tissue moisture levels decline. At 700 g kg−1 (wet basis) moisture, leaching losses reached only 0.3% of initial sample dry matter, while at 170 g kg−1 moisture they were as great as 1.7%. Leaching was also greater (P ≤ 0.05) under rainfall at 20 mm h−1 than 40 mm h−1. A regression equation generated from the leachate data can be used to model leaching losses within prescribed limits.
Effect of Crop Density on Weed Interference in Maize
Authors: Tollenaar M. , Dibo A. A. , Aguilera A. , Weise S. F. , Swanton C. J.
Published: July 2010

Development of an integrated weed management system requires detailed information on crop‐weed interactions, including the impact of the relative competitive ability of the crop during various phases of development on weed growth. The objective of this study was to quantify effects of maize (Zea mays L.) plant density on weed interference in maize throughout the growing season. Experiments were carried out during 1990, 1991, and 1992 at the Elora Research Station, Elora, ON, on a London loam (Aquic Hapludalf) soil that had been tile drained. Maize was grown at three plant densities (4, 7, and 10 plants m−2) under three weed pressures. Weed pressures were established by varying the weedfree period after maize planting: all season (weed free), planting to 5‐ to 7‐leaf stage of maize (medium weed pressure), and planting to 3‐ to 4‐leaf stage of maize (high weed pressure). Maize and weed biomass and composition were evaluated at 3 wk presilking, silking, 3 wk postsilking, and at physiological maturity. Maize leaf area index, leaf chlorophyll content, and photosynthetic photon flux density transmittance with and without weeds were also measured. Increasing maize plant density from 4 to 10 plants m−2 reduced weed biomass by up to 50%. The impact of high weed‐pressure treatments on maize dry matter accumulation remained in a narrow range of 18 to 21% throughout the growing season. The grain yield reductions attributable to high weed pressure were 26, 17, and 13% for the maize plant densities of 4, 7, and 10 plants m−2, respectively. Results of this study show that the competitiveness of maize with weeds can be enhanced by increasing plant density.
Predicting Pineapple Harvest Date in Different Environments, Using a Computer Simulation Model
Authors: Malézieux Eric , Zhang Jingbo , Sinclair Eric R. , Bartholomew Duane P.
Published: July 2010

Prediction of pineapple [Ananas comosus (L.) Merr.] fruit harvest date is essential to the scheduling of labor and fresh fruit marketing efforts. A previously developed heat‐unit model for pineapple in the Smooth Cayenne group could not satisfactorily predict fruit harvest date in the range of environments in which it is grown in Hawaii. Our objective was to develop a model based on daily maximum and minimum air temperature for the prediction of pineapple fruit harvest date in the wide range of environments where the crop is grown. For modeling, two phases of fruit development are distinguished: the time from induction of fruit development with a growth regulator (forcing, DAYFOR) to opening of the first flower (DAYFF), and from DAYFF to harvest (DAYH50, the date when 50% of the fruits are one‐third yellow). From DAYFOR to DAYFF, predictions are based on the accumulation of heatunits, based primarily on air temperature. After DAYFF, heat‐units are accumulated from estimated fruit temperature. The decrease in development rate at above‐optimum temperatures during the day is also simulated. The model was calibrated and tested using data sets from several important producing countries with different environments (southeastern Queensland, Australia, 26° S lat; Côte d'Ivoire, 5° N lat; Hawaii, 20° N lat; and Thailand, 13.5° N lat). The model predicted harvest date with a mean error of 11, 3, 12, and 5 d in Australia, Côte d'Ivoire, Hawaii, and Thailand, respectively. We believe this margin of error would be acceptable to most pineapple growers. Improvements in the model are likely to come when the relationship between fruit temperature and environmental factors is better understood.
Selection Pressures for Diclofop‐Methyl Resistance and Germination Time of Italian Ryegrass
Authors: Ghersa C. M. , Martínez‐Ghersa M. A. , Brewer T. G. , Roush M. L.
Published: July 2010

To formulate strategies for controlling herbicide resistance in Italian ryegrass (Lolium multiflorum Lam.), the selective pressures acting on wild Italian ryegrass populations to encourage evolution of resistance must be identified. Field and greenhouse experiments were conducted in 1990 to 1992 to compare the seedling emergence patterns of diclofopmethyl‐resistant and susceptible Italian ryegrass. Timing of seedling emergence in full sunlight differed for the two biotypes. In general, the herbicide‐susceptible biotype emerged earlier than the resistant biotype. Greatest emergence for the susceptible biotype was in August and September, the period prior to typical winter cereal crop sowing. Soil shading enhanced resistant seedling emergence during August and September, suggesting that soil temperature plays an important role in regulating seed germination of this biotype. Before current‐year seed shed, the seed bank in the experimental plots was found to contain three times as many viable resistant seeds as susceptible seeds. In a corroborating experiment, we found that Italian ryegrass seeds with a greater degree of dormancy were more likely to be herbicide resistant than those with a lesser degree of dormancy. Our results support the hypothesis that the timing of field tillages and herbicide use is a selective force for increasing seed dormancy and thus for changing seedling emergence patterns as herbicide‐resistant Italian ryegrass weed populations evolve. The linkage between changes in seed dormancy and herbicide resistance traits has ecological and agronomical implications.
Frequency of Nitrogen Fertilizer Carryover in the Humid Midwest
Authors: Vanotti Matias B. , Bundy Larry G.
Published: July 2010

Soil tests for residual NO‐3 can improve prediction of crop N fertilizer requirements in the humid Midwest, but their adoption as a standard procedure in fertilizer N recommendation programs depends on the frequency of significant profile NO‐3‐N carryover. Data from a 25‐yr crop sequence experiment (1967 to 1991) on a Rozetta silt loam soil (finesilty, mixed, mesic Typic Hapludalf) at Lancaster, WI, were used to estimate the frequency and extent of N fertilizer carryover. Sequences studied included unfertilized oat (Avena sativa L.) grown after corn (Zea mays L.) that received a range of N rates. Oat yields were influenced by the residual effects of the previous year's N application in 21 of the 25 yr, with yield responses varying from 500 to 1500 kg ha−1. Soil profile measurements (0 to 90 cm) taken before seeding oat in spring 1987 through 1991 showed substantial NO‐3‐N carryover that was usually found below the 30‐cm depth. Significant increases in profile NO‐3‐N content occurred at low N rates (56 to 112 kg N ha−1) in years with limited rainfall during the preceding corn growing season, but only at higher N rates under optimum corn growing conditions. Total N uptake by oat was also significantly affected by corn N treatments, and it was well correlated with profile NO‐3‐N. A nutrient efficiency index that characterized the yield response of oat to profile NO‐3‐N was used to estimate carryover NO‐3‐N from 1967 to 1986 oat yield data. Expected N fertilizer carryover values (P = 80%) ranged from 32 to 106 for a 168 kg N ha−1 rate, and from 63 to 151 kg NO‐3‐N for a 224 kg N ha−1 rate. The wide variation of expected amounts of N carryover reflects typical year‐to‐year changes in conditions affecting N recovery by corn and retention by soil. Results of this study indicate that significant residual profile NO‐3‐N occurs in most years on well‐drained silt loam soils in Wisconsin, and that year‐specific tests for profile NO‐3‐N are needed to adjust N recommendations for varying amounts of NO‐3‐N carryover.
Iron and Manganese Accumulation by the brz Pea Mutant Grown in Soils
Authors: Cary Earle E. , Norvell Wendell A. , Grunes David L. , Welch Ross M. , Reid W. Shaw
Published: July 2010

Leaf composition of the bronze (brz) mutant pea [Pisum sativum L. cv. Sparkle E107 (brz brz)] and its parent genotype (cv. Sparkle) have been compared when grown in nutrient culture, but not when grown in soil where pH has been adjusted to reduce readily available Fe and Mn. Both genotypes were grown in a growth chamber in five soils that differed in pH and DTPA‐extractable Fe and Mn. The brz genotype accumulated very high, and often toxic, concentrations of Fe and Mn when grown in acidic soils, while Sparkle did not. Liming reduced leaf‐Fe and leaf‐Mn concentrations in the brz mutant, but Fe toxicity symptoms were still evident in older leaves. In the acidic soils, leaves of the brz plants also accumulated significantly more Zn, Cu, Ca, Mg, K, Na, Al, and P than did leaves of Sparkle plants. Roots of the brz genotype depressed soil pH by several tenths of a pH unit more than did roots of Sparkle. In contrast to results obtained in the acidic and near‐neutral soils, the brz mutant and its parent grew similarly in a calcareous soil (pH 8.2), which contained low concentrations of DTPA‐extractable Fe and Mn. In conclusion, the brz mutant pea consistently accumulates high levels of Fe and Mn when these metal ions are present in readily available forms. Liming an acid soil to near‐neutral pH did not prohibit the brz mutant from accumulating potentially toxic concentrations of Fe, but growing the mutant in a calcareous soil did.
Estimation of Yield and Nitrogen Removal by Corn
Authors: Overman Allen R. , Wilson Denise M. , Kamprath Eugene J.
Published: July 2010

A wide variety of mathematical models have been used to relate crop production to management factors such as applied N and water availability. These include power functions and exponential functions. The objective of this analysis was to use an extended logistic model to relate dry matter yields and plant N removal to applied N for corn (Zea mays L.) for three soils in North Carolina. In this model, response of both dry matter yield and plant N removal to applied N were described by logistic equations. Plant N concentration was then related to applied N by the ratio of these logistic equations. Model parameters were estimated by nonlinear regression. Analysis of variance showed that the N response coefficient c was common for dry matter yield and plant N removal for each soil. Overall correlation coefficients of yield and plant N removal with applied N were very high for all three soils (R> 0.99). It was shown that ≈50% of the total dry matter and 80% of total plant N were contained in the grain at all applied N levels. Maximum potential grain yield of 25.9 Mg ha−1 agreed closely with an estimate in the literature of 26.5 Mg ha−1 (500 bushels acre−1). Dependence of plant N concentration on plant N removal was shown to follow a linear relationship. The present model provides a rational basis for coupling of dry matter yield and plant N removal in response to applied N. It can be used in design and management decisions related to agricultural production and environmental quality.
Cover Crop Production for Several Planting and Harvest Dates in Eastern Nebraska
Authors: Power James F. , Koerner Paul T.
Published: July 2010

Species used for cover crops vary greatly in their growth response to water availability, soil temperature, length of growing period, day length, and related environmental factors. Few reports compare growth of different species at different times during the growing season. This 4‐yr field experiment at Lincoln, NE, compared growth of some 20 species as affected by planting date and length of the growth period. All species were planted as early as possible each spring, with a second seeding in early summer (25 June–17 July). Additional seedings were made at other times in most years. All plots were periodically sampled for dry matter production until maturity or frost. At most samplings, growth of soybean [Glycine max L. (Merr.)] was equal to or greater than (sometimes double) that of the next species. In most situations, hairy vetch (Vicia villosa Roth) also performed well. Field pea (Pisum sativum L.) or Austrian winter pea [P. sativum L. subsp. sativum var. arvense (L.) Poir.] and fava‐bean (Vicia faba L.) grew very rapidly for the first 60 to 90 d after planting. Lespedeza [Kummerowia stipulacea (Maxim.) Makino] grew relatively well when seeded in early summer, as did tinga pea (Lathyrus tingitanus L.) and cowpea [Vigna unguiculata (L.) Walp. subsp. unguiculata]. Rye (Secale cereale L.) was usually intermediate, and small‐seeded legumes generally exhibited relatively slow growth the first 60 d. Results suggest that certain large‐seeded, cool‐season legumes would produce best for early spring seeding before row crops or summer fallow, whereas some warm‐season species would be better suited for summer seeding after small grain harvest. Soybean and hairy vetch were well suited for almost all situations in this environment.
Automating a Commercial Swather for Harvesting Forage Plots
Authors: Pearson Calvin H. , Robinson Lot
Published: July 2010

Forage plot harvesters having sicklebars are representative of technology currently used by commercial forage producers. Commercially built forage plot harvesters that are highly automated have been developed in recent years, but because of their small size they are not wellsuited for operating in fields with rough terrain, particularly fields with furrows. Furthermore, automated forage plot harvesters that use sicklebars are highly expensive, costing $30 000 and more. An automated forage plot harvester was developed at Colorado State University using a field‐scale commercial swather. A weigh bin was designed and fabricated that attaches underneath the swather directly behind the hay conditioner. This article describes, in detail, how to construct the forage plot harvester. The plot harvester can be modified quickly for use in harvesting both research plots and commercial fields. It has an electronic weighing system and a belt conveyor in the bottom of the weigh bin for discharging weighed samples. The plot harvester has performed well in furrow‐irrigated fields. Alfalfa samples weighing up to 68 kg have been harvested, and the average time required to harvest small plots was 50 s. The cost of materials for the weigh bin, including the electronic weighing system, was $2550.
Total Nonstructural Carbohydrate Accumulation in Roots of Annual Lespedeza
Authors: Davis David K. , McGraw Robert L. , Beuselinck Paul R. , Roberts Craig A.
Published: July 2010

Total nonstructural carbohydrates (TNC) stored in roots are thought to be an important energy source for growth following herbage removal in many forage legumes. This study was conducted to determine if root TNC levels fluctuate during harvest and regrowth cycles of annual lespedeza (Kummerowia spp.). Annual lespedeza management treatments consisted of harvesting at a 6‐ or 12‐cm stubble height at the end of July and a nonharvested control. Seeding‐year ‘Nitro’ alfalfa (Medicago sativa L.) and ‘Norcen’ birdsfoot trefoil (Lotus corniculatus L.) were included for comparison. Alfalfa was harvested four times at early bloom and birdsfoot trefoil three times at early bloom. Alfalfa exhibited a cyclic pattern of TNC utilization and storage in response to herbage removal and regrowth, respectively. Seedling alfalfa accumulated >150 g kg−1 TNC in the roots by 10 June, and >450 g kg−1 by first harvest. Seedling birdsfoot trefoil maintained <70 g kg−1 TNC in the roots through mid‐September and did not exhibit as much TNC cycling as did alfalfa. Annual lespedeza averaged ≈ 20 g kg−1 TNC in the roots prior to harvest and maintained <40 g kg−1 throughout the growing season. Harvesting annual lespedeza at 6 cm decreased root TNC levels for ≈ 5 wk compared with harvesting at 12 cm and the nonharvested controls; however, the total amount of reduction was small. Root TNC levels decreased by 6.1 g kg−1 with cutting at 6 cm. As annual lespedeza maintains relatively small amounts of root TNC, leaving residual leaf area at harvest may be important for regrowth.
A Computer Program to Analyze Multiple‐Season Crop Model Outputs
Authors: Thornton Philip K. , Hoogenboom Gerrit , Wilkens Paul W. , Bowen Walter T.
Published: July 2010

Management‐oriented simulation models of the growth, development, and yield of annual crops are useful tools for screening management options on the computer. Until recently, a limitation of these models has been the inability to simulate more than one cropping season at a time. The capability to simulate long‐term field experiments with such models now exists, in which the simulated soil water, N, organic C, and crop residue outputs from one model run become the input conditions for the next. Simulations of crop rotations can produce large quantities of data, especially if the simulation experiment involves replications across different years. Computer software was written to perform simple analyses of such simulation experiments. The major purpose of the software is to allow the user to investigate the stability and profitability of crop sequences. The program calculates summary statistics for model output variables; these are presented to the user in tabular and graphical forms. Net monetary returns or gross margins can also be calculated, and price and cost variability can be taken into account in the analysis. The program allows rapid, preliminary analysis of a particular crop sequence from replicated simulation experiments and can help the user to assess whether the sequence warrants further evaluation. The program can also be used to summarize the results from historical long‐term field trials. The analyses performed constitute a first step in investigating the sustainability of a particular cropping sequence for a specified length of time.
Carbon Dioxide Effects on Crop Energy Balance: Testing ecosys with a Free‐Air CO2 Enrichment (FACE) Experiment
Authors: Grant Robert F. , Kimball Bruce A. , Pinter Paul J. , Wall Gerard W. , Garcia Richard L. , La Morte Robert L. , Hunsaker Douglas J.
Published: July 2010

Elevated CO2 concentrations (Ce) have been observed to decrease short‐term plant water use under controlled conditions by increasing stomatal resistance. The extent to which this decrease occurs over a growing season in the field is uncertain, however, because stomatal resistance is only one of many mechanisms that control water use. In this study, we tested the ecosystem simulation model ecosys, which reproduces an hourly energy balance through soil‐vegetation systems under defined atmospheric boundary conditions, using energy exchange data measured as part of the Free‐Air CO2 Enrichment (FACE) experiment at Ce = 550 vs. 370 µmol mol−1. The model reproduced reductions in measured upward latent heat fluxes that varied from −10 to +40 W m−2, depending on atmospheric conditions. In the model, the primary effect of elevated Ce on latent heat fluxes was through canopy stomatal conductance. This effect was largely offset by secondary effects through canopy temperature that enabled the model to reproduce measured changes in sensible heat fluxes. The total effect simulated by ecosys of Ce = 550 vs. 370 µmol mol−1 on evapotranspiration during the entire FACE experiment was a reduction of 7%. This reduction compares with one of 11% estimated from accumulated daily measurements of latent heat flux. In the model, the different effects of Ce on plant water use depend on atmosphere and soil boundary conditions, and are highly dynamic. Consequently the simulated Ce‐water use relationship is likely to be sitespecific. The use of models such as ecosys allows site‐specific boundary conditions to be considered in the study of Ce effects on plant growth and water use.
Reduced Preplant‐Incorporated Imazaquin Rates for Broadleaf Weed Control in Soybean
Authors: Jones Darrin Scott , Lin Htain , Kane Mark V. , Grabau Larry J.
Published: July 2010

Public pressure and economic distress have together provided a strong incentive for reduced chemical use in U.S. agriculture. This field study was designed to determine if preplant‐incorporated imazaquin {2‐[4,5‐dihydro‐4‐methyl‐4‐(1‐methylethyl)‐5‐oxo‐1H‐imidazol‐2‐yl]‐3‐quinoline‐carboxylic acid} rates could be reduced from the labeled rates when applied with alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl) acetamide] without incurring yield penalties due to broadleaf weed infestations. Imazaquin was applied at 0, 47, 93, and 141 g ha−1 in earlyplanted soybean [Glycine max (L.) Merr.] studies in Fayette County in 1989, 1990, and 1991 and in Simpson County (1989), Hardin County (1990), and Hopkins County (1991), Kentucky. Preplant‐incorporated alachlor was followed by postemergence fluazifop‐P‐butyl {butyl(R)‐2‐[4[[5‐(triliuoromethyl)‐2‐pyridinyl]oxy]phenoxy]propanoate} (as needed) to minimize grass competition. Perennial broadleaf weeds were controlled with hand‐wicked glyphosate [isopropylamine salt of N‐(phosphonomethyl) glycine]. Acceptable broadleaf control was obtained at sub‐label imazaquin rates, except for Fayette 1991, where ivyleaf morning‐glory [Ipomoea hederacea (L.) Jacq.] and velvetleaf (Abutilon theophrasti Medic.) were planted. Two studies (Simpson 1989 and Hopkins 1991) showed minimal broadleaf weed pressure at any imazaquin rate; this may have been a result of the early planting dates used. The common lambsquarters (Chenopodium album L.) and Pennsylvania smartweed (Polygonum pennsylvanicum L.), which dominated in Fayette 1989 and 1990, were successfully controlled with 47 g ha−1 imazaquin. While alachlor provides some control for these two species, their competition with soybean was severe without the addition of imazaquin. Producers who can accumulate detailed knowledge of the broadleaf weed species present in their soybean fields could potentially use such information to select herbicides likely to control their broadleaves at sub‐label rates.
Effect of Alfalfa Plant and Soil Extracts on Germination and Growth of Alfalfa
Authors: Chung Ill‐Min , Miller Darrell A.
Published: July 2010

Alfalfa (Medicago sativa L.) plants contain water‐soluble substances that inhibit the germination and seedling growth of alfalfa. Determining where allelochemicals may be found in alfalfa in the greatest concentration would aid in trying to isolate the compound or compounds responsible for autotoxicity. This study investigated the allelopathic effects of various alfalfa plant parts, and the soil in which alfalfa had been grown, on alfalfa germination and seedling growth. Aqueous extracts of alfalfa leaf, stem, flower, seed, and root plant parts were made to determine their effects on germination and dry weights of hypocotyl, radicle and total length of 5‐d‐old alfalfa seedlings over a range of extract concentrations. Soil samples (Flanagan series: fine, montmorillonitic, mesic Aquic Argiudolls) from around alfalfa plants at the vegetative and reproductive stages were compared with sterilized and nonsterilized soil formerly seeded with alfalfa, hairy vetch (Vicia villosa Roth), and winter rye (Secale cereale L.) Increasing the aqueous extracts concentrations of separated alfalfa plant parts significantly inhibited alfalfa germination, seedling length and weight. Radicle length was more sensitive to extract source than seed germination or hypocotyl length. Based on 5‐d‐old alfalfa radicle length growth, and averaged across all extract concentrations, the degree of toxicity of different alfalfa plant parts and soil from around alfalfa can be classified in order of decreasing inhibition as follows: leaf, seed, complete plant mixture, soil, root, flower, and stem. Leaf extracts (12 g kg−1) caused a 48% decrease in water uptake by alfalfa seed. Soil in which alfalfa had previously grown was the most inhibitory to alfalfa growth after 25 d of growth compared with soil where winter rye or hairy vetch had previously grown. Inhibitory effects were greater for soil collected around alfalfa grown at the reproductive than the vegetative growth stage. These data indicate that alfalfa autotoxicity may result from a release of one or more water‐soluble compounds from alfalfa leaf tissue.
PC‐SAS Program for Estimating Hühn's Nonparametric Stability Statistics
Authors: Lu Hsui Ying
Published: July 2010

A program written in the SAS language for personal computers to estimate Hühn's two nonparametric stability statistics is presented. Nonparametric methods proposed by Hühn in the 1970s are based on the ranks of genotypes in each environment and use the idea of homeostasis as a measure of stability. A stable genotype shows similar rankings across environments. Nonparametric stability statistics provide a viable alternative to existing parametric measures based on absolute data. They require no statistical assumptions about the distribution of the phenotypic values and are easy to use. Addition or deletion of one or a few observations is not as likely to cause great variation in the estimates as would be the case for parametric stability measures. For many applications (e.g., selection in breeding and testing programs), the rank orders of genotypes are the most essential information. The program deals with a two‐way table with K genotypes and N environments. The output contains two main features: (i) corrected values and their ranks of genotypes within each environment, and (ii) two nonparametric stability estimates and their test of significance. From the output, one may examine the rankings of genotypes in each environment and look for stability differences among genotypes. This program should make practical the more frequent use of nonparametric stability statistics to investigate genotype ✕ environment interactions in agricultural research.