bluuebunny/crossref_metadata_2025 huggingface dataset:
Gaseous N Losses from Winter Wheat1
Authors: Hooker M. L. , Sander D. H. , Peterson G. A. , Daigger L. A.
Published: July 2010

Research monitoring N uptake by various agricultural crops has shown total N accumulations in the plant to increase prior to the growth stages around heading to flowering with a subsequent decrease in total N occurring after flowering. Volatilization of N from the plant may account for much of this loss as well as account for some of the deficits exhibited in N balance studies. Experiments were conducted in a gas‐tight growth chamber to determine what role plants alone may play in the overall loss of N from the soil‐plant system. Winter wheat (Triticum aestivum L.) was established, vernalized, and grown to maturity in the growth chamber. At first internode elongation, the chamber was closed and sealed for the duration of the experiment. Air supplied to the chamber during this period was bubbled through 1 N H2SO4 to remove ambient NH3 and through a reagent specific to NO and NO2 to remove these gases. Air samples were continuously drawn from the chamber and bubbled through 0.2 N H2SO4 to trap evolved NH3. These samples were collected weekly and analyzed using steam distillation. A second portion of the air sample was washed through the NO‐NO2 specific reagent and analyzed colorimetrically. Only trace amounts of NO and NO2 could be found at any time during the experiment leading to the conclusion that volatilization of these gases does not contribute significantly to the loss of N from the plant. Ammonia volatilized from the system at the rate of 0.34 to 0.89 ✕ 10−1 mg NH3‐N/m2/day prior to flowering. After flowering the rate of NH3‐N evolution increased to 1.03 to 1.32 ✕ 10−1 mg/m2/day. This dramatic increase in the rate of NH3‐N evolution at flowering coincides with the plant growth stage that researchers have begun to observe deficits in total N accumulations in the above ground portion of the plants. This data supports the hypothesis forwarded here, that volatilization of NH3 from plant tissue can partially account for the deficits in total N accumulation observed in plant tissue following flowering.
Forage Production Estimates for Irrigated Meadows from Landsat Data1
Authors: Cipra J. E. , Noguerapena N. E. , Bryson M. C. , Lueking M. A.
Published: July 2010

Landsat data have become increasingly useful in agriculture over the past several years. The satellite has been used in mapping soils, determining crop growth and condition, and here to estimate forage production in irrigated native hay meadows in the South Park region of Colorado.

The objective of this study was to estimate forage production in irrigated meadows and surrounding rangeland using Landsat digital data and computer analysis. Biomass of standing, above‐ground, green vegetation was estimated by clipping and visual estimates for two growing seasons. Forage production data were compared to Landsat radiance data and ratio‐transformed data using linear regression and analysis of variance. Based on the existing conditions of this study, the use of Landsat data to estimate production appears feasible. However, production estimates will be most reliable if ground data are collected each year.
In Vivo Quality of Tall Fescue as Influenced by Season, Legumes, Age, and Canopy Strata1
Authors: Rayburn E. B. , Blaser R. E. , Fontenot J. P.
Published: July 2010

Fall‐grown tall fescue (Festuca arundinacea, Schreb.) provides a relatively inexpensive forage for winter grazing. Quality and yield of actively growing tall fescue increases when accumulated from August and harvested through time in the early fall. The effect of regrowth age on fall accumulated tall fescue quality has not been evaluated under similar harvest climates and animal performance on summer grown tall fescue is often low. Therefore a series of experiments were conducted to evaluate the in vivo quality of tall fescue in summer, alone and in combination with a legume, and to evaluate the in vivo quality of tall fescue of different regrowth ages harvested in December.

Summer grown tall fescue, alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.) were fed alone and compared with 50:50 mixes of each legume with tall fescue. Orchardgrass (Dactylis glomerata L.) was also fed alone and with red clover during 1 year. Low in vivo digestible dry matter (DDM) of 35.8% for tall fescue 60 days old in 1975 was associated with droughtimposed dormancy. Nondormant, 40‐day‐old alfalfa regrowth was highly digestible (59.4% DDM). In 1976, the digestibilities of tall fescue and red clover were similar (54.8 and 53.9% DDM) and lower than that of orchardgrass (57.0% DDM). Consistent, nonsignificant trends in increased digestibility occurred with the inclusion of a legume which were sufficiently large to have potential economic consequences on animal production.

In another experiment, tall fescue was accumulated from mid‐June, July, August, and September, with 112 kg N/ha applied in mid‐August, to evaluate the influence of age on in vivo quality when fed to sheep in early December. Quality decreased with increasing age. In 1975, June accumulated forage was significantly lower in quality than forage with shorter accumulation periods. In 1976, quality decreased with increased ages of the accumulated growth, ranging from 51.0 to 60.5% DDM for June and August accumulated forage, respectively. Quality of September accumulated forage was low (52.8% DDM), apparently due to high lignin and insoluble ash contents. Improved quality with shorter accumulation periods was offset by lower dry matter yields (5.2 vs. 2.2 metric tons/ha) and DDM yields were also reduced (1.7 vs. 1.2 metric tons/ha) from June to September, respectively. Accumulating tall fescue from as early as mid July did not decrease digestibility or intake sufficiently to make this practice impractical for winter grazing. Summer utilized tall fescue was lower in quality than that utilized in winter. There were significant correlations between DDM and TNC contents.
Leaf Water Potential, Stomatal Resistance, and Temperature Relations in Field‐Grown Soybeans1
Authors: Jung P. K. , Scott H. D.
Published: July 2010

There is a need for daily and seasonal measurements of the field water status of plants in order to characterize their response to soil water deficits. Measurements were made of leaf water potential (Ψ), stomatal diffusive resistance (R), and leaf temperature (T) of irrigated (I) and nonirrigated (N) ‘Forrest’ soybeans [Glycine max (L.) Merr.] grown on Crowley silt loam (a Typic Albaqualf), in a dry season. Values of Ψ in the N soybeans decreased earlier in the day and increased later in the afternoon than Ψ values of I soybeans. The stomates of N plants were partially closed during the daylight hours and closed earlier in the afternoon than stomates of I plants. Leaf temperatures of the N plants increased earlier in the morning and remained higher later in the afternoon than leaf temperatures of I plants. As the drought intensified, differences in Ψ, R, and T between the N and I soybeans increased. Maximum differences during the day were approximately ∆Ψ = −4 bars, ∆R = 6.0 sec/cm, and ∆T = 5.5 C and were usually found at midday and midafternoon late in the season. Generally, the differences in these parameters between moisture regimes were lower at midmorning. The differences in these plant water and temperature parameters were reflected in lower production of total dry matter and seed.
Measuring Soil Nitrogen Mineralization Under Field Conditions1
Authors: Westermann D. T. , Crothers S. E.
Published: July 2010

The amount and rate of soil N mineralization are important components that can be used to predict preplant N fertilizer application and to evaluate the need for N fertilization during crop growth. This study‘s purpose was to evaluate the buried polyethylene bag technique as a method for characterizing the N mineralized under field conditions during the cropping season. Soil (Xerollic Calciorthids) was placed in polyethylene bag and buried in the 0 to 45 cm root zone of fallowed soils and where corn (Zea mays L.) and potato (Solanum tuberosum L.) were being grown. The NO3‐N content of the soil in the bags was compared with that in the root zone at selected time intervals (10 to 14 days) from April to October.

The soil NO3‐N concentrations in the buried polyethylene bags were similar to those in irrigated fallow soils from April to October after correction for different soil water contents. The N‐mineralization rate between sampling intervals had an average temperature coefficient (Q10) of 2.3 between 10 C and 30 C. The relative N‐mineralization rate was proportional to the soil water content expressed as a percentage of the available waterholding capacity. The N uptake by corn and potato crops predicted from NO3‐N changes in the rooting zone and in the buried polyethylene bags resembled those measured by plant sampling. The buried polyethylene bag technique has potential for monitoring the soil N‐mineralization process during the cropping season and for estimating N uptake by crops. It also provides an alternative method for estimating soil N availability for future crops and its use should maximize N‐fertilizer efficiencies.
Effects of Management Practices on Reflectance of Spring Wheat Canopies1
Authors: Daughtry C. S. T. , Bauer M. E. , Crecelius D. W. , Hixson M. M.
Published: July 2010

Analyses of multispectral measurements from satellites offer the potential to monitor and inventory crop production. The crop canopy is a dynamic entity influenced by many cultural and environmental factors. In order to quantify and understand some of these potential sources of variation in spectral measurements of crops, an experiment was conducted on a Williams loam (fine−loamy, mixed Typic Argiborolls) at the Williston, North Dakota, Agricultural Experiment Station in 1977. The effects of soil moisture, planting date, nitrogen fertilization, and cultivar on reflectance of spring wheat (Triticum aestivum L.) canopies were investigated. Spectral measurements were acquired on eight dates throughout the growing season with a radiometer (Exotech 100 A) in four wavelength bands (0.5 to 0.6, 0.6 to 0.7, 0.7 to 0.8, 0.8 to 1.1 µm) at 3.5 m above the plots. On the days spectral data were taken, measurements of crop maturity stage, leaf area index, biomass, plant height, percent soil cover, and soil moisture were also taken.

In this experiment, planting date and available soil moisture were the primary agronomic factors affecting reflectance of spring wheat canopies from tillering to maturity. Comparisons (R2) of treatments indicated that during seedling and tillering stages, planting date was associated with 36 and 85% of variation in red (0.6 to 0.7 µm) and near infrared (0.8 to 1.1 µm) reflectances, respectively. As the wheat headed and matured, less variation in reflectance was associated with planting date and more with available soil moisture. By mid July soil moisture accounted for 73 and 69% of the variation in reflectance in red and near infrared bands, respectively. Differences in spectral reflectance among treatments were attributed to changes in leaf area index (LAI), biomass, and percent soil cover. Cultivar and N fertilization rate had little association with the variation in reflectance of these canopies. Agronomic practices resulting in differences in LAI, biomass, and percent soil cover potentially can be monitored by remote sensing and this information may be useful in estimating crop production.
Association of Epichloe Typhina Fungus and Steer Performance on Tall Fescue Pasture
Authors: Hoveland C. S. , Haaland R. L. , King C. C. , Anthony W. B. , Clark E. M. , McGuire J. A. , Smith L. A. , Grimes H. W. , Holliman J. L.
Published: July 2010

Anti‐quality components factors associated with poor animal performance on tall fescue (Festuca arundinacea Schreb.) pasture may include mycotoxins produced by the fungus Epichloe typhina (Pers.) Tul. The original objectives of this study were to compare steer performance on pastures of different grass species, but large differences in animal performance occurred among paddocks in different replications of the tall fescue‐dallisgrass (Paspalum dilatatum Poir.) treatment. The experiment was conducted in west central Alabama on replicated 1.2 ha paddocks containing two calcareous soils, Sumter clay (Rendolic Eutrochrept, fine silty, carbonatic, thermic) and Houston clay (Typic Chromudert, very fine montmorillonitic, thermic). The tall fescue‐dalligrass pastures were fertilized with 336 kg N/ha annually and grazed with yearling steers for 225 days annually for 3 years. The three tall fescue‐dallisgrass paddocks contained very little dallisgrass, but animal performance differed greatly on them. Steers averaged 453 kg gain/ha on two paddocks with an average daily gain (ADG) of 0.68 kg, while steers on the other paddock averaged only 360 kg gain/ha with an ADG of 0.45 over the 3‐year period. Dry matter digestibility of the forage averaged 63% for the high performance paddocks and 58% for the low performance paddock. Mineral content of the forage was similar on all paddocks. Tall fescue forage in the low performance paddock was heavily infested with Epichloe typhina fungus while the other two paddocks were lightly infested with the fungus. Results of the study suggest that this fungus may be associated with low performance of steers on tall fescue pasture.
Reproductive Abscission Levels and Patterns for Eleven Determinate Soybean Cultivars1
Authors: Wiebold W. J. , Ashley D. A. , Boerma H. R.
Published: July 2010

Although soybeans (Glycine max L. Merrill) are considered to have relatively high levels of reproductive abscission, most studies have used only one or two cultivars and cultivar differences for abscission have rarely been reported. This study determined the abscission levels for 11 field‐grown, determinate soybean cultivars (Maturity Groups V, VI, VII, VIII) and tested for cultivar differences in abscission. Numbers of flowers and young pods (2 cm long) produced and pods at harvest were determined for 15 plants of each cultivar. New flowers were counted on alternate days; whereas, young pods were counted weekly. Production of each reproductive structure was recorded for each node (including any branches) of each plant. Seed number and weight at harvest were also determined. Cultivars differed in number of flowers, young pods, and pods produced per plant. Number of flowers roduced per plant rangaf from 170 to 332 and average 232. Number of pods at harvest ranged from 41 to 90 and averaged 57 per plant. Cultivars also differed in the percentage of fruit less than 2 cm in length which abscissed and percent total abscission. Percent total abscission rang ed from 67% for ‘McNair 800’ to 82% for ‘Hale 3’ and averaged 75% Small pods (less than 2 cm in length) and flowers accounted for an average of 87% of the total abscission. Flower production of most cultivars was concentrated in the top two‐thirds of the canopy. The to one‐thiid canopy region of most cultivars accounted for a majority of the harvestable pods. Percent total abscission increased with depth into the canopy. Yield (seed weight per plant) was related positively (r= 0.50) to numbers of flowers produced. It is concluded that determinate soybean cultivars differ in percent abscission. That a deficit of available carbohydrate is at least one of the factors involved in soybean reproductive abscission is discussed.
Heat Tolerance of Kentucky Bluegrasses, Perennial Ryegrasses, and Annual Bluegrass1
Authors: Wehner D. J. , Watschke T. L.
Published: July 2010

Use of cool‐season turfgrasses in transitional environments is limited, in part, by their heat tolerance. Development of a rapid heat tolerance screening technique would be of value in determining the potential of turfgrasses for use in warmer areas.

The heat tolerance of 22 Kentucky bluegrass (Poa pratensis L.) cultivars, Poa annua L., and four perennial ryegrass cultivars (Lolium perenne L.) was evaluated by exposing plants for 30 min to temperatures ranging from 41 to 49 C in single degree intervals. Ten‐week‐old plants, which had been grown under a low level of N fertilization and watered infrequently to maximize heat tolerance development, were sealed in plastic bags, placed in a constant temperature water bath for treatment, and then replanted. Recovery was evaluated by visually rating the plants 4 weeks afte treatment or by harvesting and weighing plants 2 weeks after treatment and expressing the weight as a percentage of the weight of a nonstressed control (referred to as recovery weight). Cultivar comparisons were based on the average recovery weight over a given temperature range.

Initial injury occurred at 41 to 43 C with complete kill at 47 to 49 C. Kentucky bluegrass was more heat tolerant than Poa annua L. and perennial ryegrass. Heat tolerance of the latter two species was approximately equal. The Kentucky bluegrass cultivars tested were similar in heat tolerance. Among the ryegrasses, “‘Loretta’ was less heat tolerant than ‘Diplomat’, ‘Pennfine’, and ‘Citation’. Of all the grasses, ‘Sydsport’ Kentucky bluegrass ranked the highest and Loretta perennial ryegrass the lowest in heat tolerance. The correlation between dilute acid extractable carbohydrate reserves and recovery weight for these five cultivars was not significant. There was a significant negative correlation between recovery weight and Fe and A1 concentration.
An Index of Nutrient Efficiency and Its Application to Corn Yield Response to Fertilizer N. I. Derivation, Estimation, and Application1
Authors: Capurro Eduardo , Voss Regis
Published: July 2010

Improving the efficiency of use of applied nutrients in crop production are agronomic, economic, and environmental goals. The purpose of this study was to develop a methodology for studying the efficiency of fertilizer use, to apply it to the yield response of corn (Zea mays L.) to fertilizer N, and to use these results to estimate fertilizer N needs for a range of relative corn yields.

The derived nutrient efficiency was divided into two components: (a) one depending on the level of relative yield expressed as a percentage of maximum yield (hence, it depends on the nutrient rate and can be estimated from soil test or plant analysis values) and (b) a component termed relative efficiency index (Ex), which can be defined generally as the nutrient efficiency at 99% of maximum yield and is independent of the nutrient rate. for the quadratic polynomial, Ex is equal to one‐fifth of the product of the square roots of the quadratic coefficient and of the maximum yield.

Relative efficiency index for N, EN, were obtained from quadratic regressions of corn yield on fertilizer N rates for each of 33 experiments conducted on well, moderately well, and somewhat poorly drained soils in Iowa. EN was closely related to the square root of the quadratic coefficient. Values of EN ranged from 2.5 to 9.3, and maximum grain yields varied from 3,600 to 10,200 kg/ha. Nutrient efficiencies were calculated from given values of EN and relative yield, e.g., this gave efficiencies in kg grain/kg N of 14 for EN of 2 and 42 for EN of 6 at a relative yield of 50%. The required increase in N rate for economic optimum yield was calculated from given values of EN, relative yield, maximum yield, and the N to corn price ratio.

The Ex seems to be a useful index to characterize the response of crop yields to applied nutrients and to derive yield‐applied nutrient relationships.
Nitro Compounds in Indigofera Species1
Authors: Williams M. C.
Published: July 2010

The genus Indigofera consists of approximately 700 species of tropical and subtropical origin. Several of these species are being investigated for possible introduction into the southern United States. Leaves of Indigofera species grown in the field and greenhouse, or sampled from herbarium specimens, were analyzed colorimetrically for aliphatic nitro compounds. Aliphatic nitro compounds were found in 64 of 250 species of Indigofera in concentrations of 2 to 12 mg NO2/g of plant. Four species that assayed 4 to 12 mg NO2/g were moderately toxic to 1‐week‐old chicks when administered as an aqueous extract. Hairy indigo (Indigofera hirsuta L.), a commercial variety already introduced, did not contain nitro compounds and was nontoxic to chicks. Indigofera species proposed for introduction into the United States should be examined for the presence and concentration of nitro compounds.
Establishment of Sod‐seeded Alfalfa at Various Levels of Soil Moisture and Grass Competition1
Authors: Groya F. L. , Sheaffer C. C.
Published: July 2010

Alfalfa (Medicago sativa L.) establishment in competition with grass sods is not always successful, especially under conditions of soil moisture deficiency. Our objective was to evaluate the effect of soil moisture concentration and grass competition on alfalfa establishment and yield when it was interseeded into perennial grass sods.

In a greenhouse experiment, alfalfa was seeded into Kentucky bluegrass (Poa pratensis L.) or smooth bromegrass (Bromus inermis Leyss.) sods which had been sprayed with 0, 0.6, and 2.2 kg/ha glyphosate [N‐(phosphonomethyl)glycine]. Three soil moisture regimes were established by watering to field capacity when soil moisture tensions reached 0.1, 1, and 12 bars. Grass‐shading treatments were also applied.

At two field locations alfalfa was seeded into an unimproved Kentucky bluegrass, smooth bromegrass, and quackgrass (Agropyron repens L.) pasture and into a smooth bromegrass pasture. The soil at both locations was a Waukegan silt loam (Typic Hapludoll). Three levels of grass suppression were obtained by spraying with 0, 0.8, and 3.3 kg glyphosate/ha. Soil moisture regimes consisted of watering to field capacity when soil moisture tension reached 1 and 15 bars.

Under shaded conditions in the greenhouse and with low grass suppression (no glyphosate) in the field, moisture did not significantly affect alfalfa establishment or dry matter yield. However, when shading was eliminated or grass suppression increased, low soil moisture tensions resulted in increased legume yields.

In the greenhouse, alfalfa dry matter yields and root weights were generally greater when it was seeded into Kentucky bluegrass compared to smooth bromegrass. Smooth bromegrass was more tolerant of glyphosate application than Kentucky bluegrass. When seeded into smooth bromegrass, alfalfa yields from low and medium moisture level treatments were not significantly different, but when seeded into Kentucky bluegrass yields from high and medium moisture levels were significantly greater than for the low moisture treatment.

Our results show that both adequate soil moisture and reduced grass competition for light are important for successful alfalfa sod‐seeding.
Effect of Time and Amount of Nitrogen Uptake on Sugarbeet Growth and Yield1
Authors: Carter J. N. , Traveller D. J.
Published: July 2010

Sugarbeet (Beta vulgaris L.) root quality has been steadily decreasing since the early 1950's with increased use of N fertilizer. Since the extent of these decreases may be associated with the time and amount of N uptake, the objective of this study was to evaluate the effects of several rates and times of N fertilizer applications and N uptake by sugarbeets on seasonal growth rates, sucrose percentage and accumulation, dry matter production, and partitioning of the photosynthate.

Sugarbeets were grown under field conditions on a Portneuf silt loam soil (Durixerollic Calciorthids, coarsesilty, mixed, mesic) near Twin Falls, Idaho, in 1977, using four N rates, each applied preplant, mid‐June, mid‐July, and mid‐August. Root yields, sucrose concentration and yield, dry matter production, leaf area index, and plant N uptake were determined from samples taken throughout the season. Adding N fertilizer above that needed for optimum plant growth or delaying N application until midseason caused a greater proportion of the photosynthate to be used for increased top growth at the expense of dry matter and sucrose accumulation in the roots. Sucrose accumulation was maximum from late July until early September; therefore, during this period, addition of N and N uptake by the plant caused the greatest decrease in sucrose accumulation and production at harvest. Increasing N levels decreased sucrose concentrations during the season and at harvest because of 1) increased moisture level of roots, and 2) dry matter produced and accumulated in the roots having a decreased sucrose concentration. The rate of accumulation of stored sucrose was reduced by midseason N application, but stored sucrose was not used for increased growth of beet tops. Excess and late N applications also increased impurities in the beet root, decreasing extractability of stored sucrose, which further decreased refined sucrose production. Early application of N fertilizer at optimum levels should maximize refined sucrose production.
A Dynamic Model for Technical and Economic Analysis of Fertilizer Recommendations1
Authors: Lanzer Edgar A. , Paris Quirino , Williams William A.
Published: July 2010

The rationale of this study was to jointly estimate response functions for N, P, and K for wheat and soybean cropping in southern Brazil and carryover functions for residual fertility. The two sets of functions were then combined in a dynamic model having general applicability for optimizing fertilizer recommendations. The model is composed of (a) a yield‐nutrient response function incorporating Liebig's Law of the Minimum and Mitscherlich's relative yield theory, (b) fertility carryover functions for P and K, and (c) a multiperiod economic programming model which combines crop yield response and carryover functions with crop and fertilizer prices. Important implications are that (a) the Law of the Minimum assume no nutrient substitution, (b) the relative yield theory allows pooling response data from different experiments, and (c) the fertilization problem is treated as a dynamic process that utilizes revised measures of soil fertility as they become available through soil tests. The crop response was specified as a piecewise linear and plateau function while the fertility carryover was postulated as a first order difference equation, incorporating an exponentially declining process of soil fertility. The solution of the overall dynamic model took the form of a multiperiod linear programming problem.

The N, P, and K response functions for wheat (Triticum aestivum L.) and soybean (Glycine max L.) yields were generated from 38 fertilizer field experiments conducted at Rio Grande do sul and Santa Catarina states in southern Brazil between 1968 and 1976. The seven experiments that were repeated for 4 years provided the information for estimating the carryover effects of P and K fertilization.

The results indicate that the optimal target levels of soil fertility are in accordance with those recommended locally. The maintenance applications recommended, however, are substantially different than the optimal quantities determined by the dynamic model presented here. The model calls for a reduction of the current maintenance application for both N and P of 10 kg/ha and an increase for K of 12 kg/ha. This would result in a U.S. dollars saving of $27/ha 1 year.
Effects of Cattle Feces Rapidly Buried by Dung Beetles on Yield and Quality of Coastal Bermudagrass1
Authors: Fincher G. T. , Monson W. G. , Burton G. W.
Published: July 2010

Cattle numbers have steadily increased in the southeastern United States partly in response to increased fertilizer use and higher producing forage varieties that permit higher stocking rates. Heavily stocked pastures result in accumulation of feces on pasture surfaces and contamination of forage. This study was initiated to study the effects of rapid burial of cattle feces by dung beetles on Coastal bermudagrass [Cynodon dactylon (L.) Pers]. Fresh cattle feces containing the equivalent of 224 kg N/ha were applied to duplicate plots of Coastal bermudagrass for determinations of pasture yield: 1) when feces are buried by dung beetles, and 2) when feces remain on the pasture surface. The soil was a Tifton loamy sand (Plinthic Palendults; fine‐loamy, siliceous, thermic family) . Dung beetles confined to one‐half of the plots buried 78% (175 kg N/ha) of the applied feces. Total dry matter yields were 7,791 kg/ha where the feces were buried by beetles and 6,364 kg/ha where not buried as compared to yields of 5,369 and 8,305 kg/ha where 112 and 224 kg N/ha were applied as ammonium nitrate. The yield from plots with the buried feces was not significantly different from that from plots receiving 224 kg/ha of N fertilizer. Similar results were obtained when wheat was oversecded on Coastal bermudagrass plots in which the effect of application of ammonium nitrate fertilizer was compared with that of cattle feces buried by dung beetles in the fall. Burial of feces by a greater than normal dung beetle population on pasture with grazing cattle also produced higher yields of Coastal bermudagrass compared to similar pastures with lower dung beetle populations. The results indicated that Increasing the dung beetle population on pastures by introduction of foreign species of beetles would be very beneficial for forage production in high density grazing systems.
Dry Matter Production and Nitrogen Utilization by Six Potato Cultivars1
Authors: Kleinkopf G. E. , Westermann D. T. , Dwelle R. B.
Published: July 2010

The rate and duration of tuber growth largely determines the final potato (Solanum tuberosum L.) tuber yields. Cultivars that continue leaf development and nutrient uptake while maintaining maximum tuber growth rates may have higher final tuber yields, yet different N requirements. The objective of this study was to obtain information relating plant growth rates to N availability for selected potato cultivars. Total dry matter accumulation and N assimilation patterns of indeterminant cultivars, ‘Russet Burbank’, ‘Lemhi Russet’, ‘Centennial Russet’, and one advanced selection A66107‐51, were compared with that of two determinant cultivars, ‘Pioneer’ and ‘Norgold Russet’, at three N levels. Cultivars were grown in a field experiment on a Portneuf silt‐loam soil (Xerollic Calciorthids).

High available soil N levels at planting delayed the linear potato tuber growth period 7 to 10 days but had minor effects on the time of tuber initiation for the indeterminant varieties. Maximum tuber growth rates (tuber bulking) were 900 to 1,300 kg/ha/day. A66107‐51 was superior in N‐use efficiency to the other cultivars. Between 70 and 100% of the total available N was utilized by this cultivar in producing high yields. This information may be used to select lines and cultvars that will optimize production. A knowledge of plant growth and N uptake rates can improve the fertilizer recommendations for each cultivar.
Nitrogen Fixation Rates of Alfalfa and Red Clover Grown in Mixture with Grasses1
Authors: Craig Lelia de Anda , Wiebold W. J. , McIntosh M. S.
Published: July 2010

Nitrogen contributions of legumes to grass‐legume mixtures are estimated on the basis of legume monocultures and may need to be adjusted to reflect any effect of the companion grass. An experiment at two field locations was conducted to determine whether the N2‐fixation rates of alfalfa (Medicago sativa L.) and red clover (trifolium pratense L.) were significantly affected by mixed culture with orchardgrass (Dactylis glomerata L.) or timothy (Phleum pratense L.). Legumes and grasses were grown in eight mono‐ or mixed cultures. Specific nodule activity (SNA) was estimated by acetylene reduction at first flower of legumes and 4 weeks after initial harvest. Grasses were analyzed for total N (TN). Legume dry weight per plant was reduced by association with grasses in only one determination at one location. Grass TN 4 weeks after initial harvest was in most instances increased significantly by the legume. Specific nodule activities of red clover grown alone and red clover grown with grasses were similar and did not change between determinations. The SNA of alfalfa grown with grass was significantly higher than that of alfalfa grown alone for the second determination at one location. The SNA of alfalfa in mixed culture increased between determinations; however, SNA of alfalfa monocultures did not change. It is concluded that grass plants are not detrimental to legume plants and may stimulate N2‐fixation. Some transfer of N from legumes to grasses may occur when the two species are grown in mixed cultures.
Use of Saline Water for Supplemental Irrigation of Sugarcane1
Authors: Thomas J. R. , Salinas F. G. , Oerther G. F.
Published: July 2010

Supplemental irrigations of sugarcane with saline ground waters may become necessary in the Lower Rio Grande Valley of Texas, since the water requirement of this crop greatly exceeds the irrigation water allotment. Experimental objectives were to determine the feasibility of using saline ground water for supplemental irrigation of sugarcane and to compare the effects of water quality on cane and sugar yields, juice quality, and the mineral composition of leaves and juice. Sugarcane cv. ‘N.Co. 310’ growing on Hidalgo sandy clay loam (Typic Calciustolls) was irrigated with river (EC = 1.4 mmho/cm) and a prepared saline water (EC = 4mmho/cm) under five irrigation treatments. Yields of cane (r = −0.85, significant at the 0.05 level of probability), seasonal mean stalk elongation rate (r = −0.95, significant at the 0.01 level of probability), stalk length at harvest (r = −0.94, significant at the 0.01 level of probability) and electrical conductivity (ECj) of the juice (r = −0.93) were linearly correlated with the weighed mean salinity (ECw) of the irrigation waters in 1974, a relatively dry year. Juice Cl concentrations were linearly correlated (r = 0.94, significant at the 0.01 level of probability) with the CI concentrations of the irrigation waters. Because of the leaching effect of rainfall, the effects of saline water irrigations on soil salinification and plant growth were minimized. Root zone salinity (ECe) levels were less than the threshold salinity level of 5.9 mmho/cm. Consequently, the effects of water quality on yields were small and generally nonsignificant.

The average annual rainfall (67.9 to 43.9 cm) across the Lower Rio Grande Valley is probably sufficient to lower salinity if saline well waters were used for supplemental irrigation on medium texture soils. In 1974, 42.3 cm of rain after the final irrigation decreased the ECsw values at the 46 cm depth to less than 1 mmho/cm. This suggests that waters with salinity concentrations above 4 mmho/cm could probably be used to irrigate sugarcane of medium texture soils in the Lower Rio Grande Valley of Texas.
Alfalfa Management Under Saline Conditions with Zero Leaching1
Authors: Francois L. E.
Published: July 2010

Previous studies have shown that alfalfa (Medicago sativa L.) can tolerate high salinity levels in the lower portion of the root zone without significant yield reduction, provided the upper portion of the root zone is maintained relatively free of salinity. The question of how much salt can be stored in the lower root zone before encroachment into the upper root zone occurs with subsequent yield reduction remains unanswered. Consequently, a study was conducted in greenhouse lysimeters to determine salt storage capacity in the lower part of the root‐zone and the long‐term effects of this management on plant growth. The lysimeter soil was Pachappa fine sandy loam (mixed, thermic, Mollic Haploxeralf).

Alfalfa was grown with and without leaching using an irrigation water having an electrical conductivity of 1.0 dS/m in soil profiles 0.6, 1.2, and 1.8‐m deep for 9, 14, and 20 months, respectively. During these respective time periods yield from the nonleached lysimeters was reduced less than 25% while more than 14.6, 30.2, and 45.6 Mg/ha of salt was stored in the bottom half of the three soil profiles. The deeper the soil the greater the capacity to store salt with minimal yield reduction. Yield was drastically reduced once salt build‐up began in the upper portion of the root zone. Consequently, irrigating to leach accumulated salt out of the upper root zone may be necessary but this can be accomplished during the winter or off season when water is more readily available. Shallower soil profiles may require more frequent leaching.
Production and Competition of Crested Wheatgrass‐Native Grass Mixtures1
Authors: Schuman G. E. , Rauzi F. , Booth D. T.
Published: July 2010

Mining in the Northern Great Plains is resulting in the disturbance of large acreages of rangeland which requires revegetation to stabilize the soil resource and return it to productivity. The competition of ‘Nordan’ crested wheatgrass [Agropyron desertorum (Fisch.) Schult.] with four individual native grass species and with a mixture of the four species was evaluated in the field at Cheyenne, Wyoming. This study was initiated to determine if crested wheatgrass, an easily established introduced species, can be seeded with more difficult to establish native grasses and result in a diverse community. Crested wheatgrass was seeded with slender wheatgrass [A. trachycaulum (Link) Malte], thickspike wheatgrass [A. dasystachyum (Hook.) Scribn.], western wheatgrass (A. smithii Rybd.), and green needlegrass (Stipa viridula Trin.) or with a mixture of these four native species in the fall of 1976 on an Archerson fine, sandy, clay loam (Aridic Arguistol). Crested wheatgrass comprised 25% of the seed mixture in all treatments. In 1977, 69.5, 42.5, 22.5, and 22.6% of the total production was slender, thickspike, and western wheatgrass and green needlegrass, respectively. In 1980, production of slender, thickspike, and western wheatgrass and green needlegrass was 2.6, 15.5, 15.5 and 36% of the seeded species production, respectively. This decrease in percentage of production of the native wheatgrass species was the result of a large increase in crested wheatgrass production.

When crested wheatgrass was seeded with the mixture of all four native species, the 1977, 1978, 1979, and 1980 production of the native species represented 62.4, 31.2, 21.3, and 4.3% of the seeded species production, respectively. The major decline in percentage of production contributed by the native species in 1978 was largely due to the loss of slender wheatgrass. In 1977, slender wheatgrass represented 76.8% of the production of the native species, however, it declined to 18.2% in 1978. By 1980, all of the native species had declined to the point that the mixture was nearly a pure stand of crested wheatgrass.

It appears that green needlegrass when seeded alone with crested wheatgrass is able to successfully compete and make substantial growth. However, inclusion of other native species in the mixture with green needlegrass resulted in a greater competition among the native species, which caused a decline in green needlegrass production. Seeding crested wheatgrass with these native species or with a mixture of these native species is not recommended if you desire a major portion of the production to be native species. Although crested wheatgrass represented 25% of the seed mixture in all treatments, after 4 years it represented at least 64% of the production.
Sodium Hypobromite Oxidation Method for Determination of Total Phosphorus in Plant Materials1
Authors: Dick W. A. , Tabatabai M. A.
Published: July 2010

A simple, sensitive, precise, and rapid method for determination of total P in plant materials is described. The sample is heated with alkaline sodium hypobromite solution to oxidize the P compounds to phosphate, and the phosphate thus obtained is extracted with 1N H2SO4 and determined colorimetrically by a heteropoly blue color method. Comparison of results obtained by the hypobromite oxidation and HNO3‐HCIO4 digestion procedures showed that the average total P values by the two methods for 20 plant samples and animal manures analyzed were 0.385 and 0.384%, respectively. In addition to being safe, digestion of plant samples with sodium hypobromite solution and colorimetric determination of the extracted P by the method of Murphy and Riley permits 100 analyses to be performed by a single operator in a normal working day.
Takadiastase Enzyme Pretreatment for Determining Cell Wall Constituents in Corn and Sorghum Silages1
Authors: Smith D. H. , Marten G. C. , Britton R. A.
Published: July 2010

The conventional Van Soest (VS) method of determining cell wall constituents (CWC) of forages often results in artificially high CWC yields with high‐grain cereal silages due to starch contamination. Our objective was to determine, the feasibility of use of a takadiastase enzyme pretreatment (TEP) to remove starch before neutral detergent extraction in CWC determination. In preliminary studies with a highgrain corn (Zea mays L.) silage, CWC residues from the VS method and from the TEP method contained 16.2 and 1.7% starch, respectively. Subsequent studies were conducted using 13 corn and 13 sorghum [Sorghum bicolor (L.) Moench] silages to compare the reliability of CWC values obtained from VS, TEP, and a procedure suggested by Fonnesbeck and Harris (FH) that utilizes acid and pepsin pretreatments before neutral detergent extraction. The mean CWC values obtained by using TEP were lower for both types of silages than were those from VS and FH methods. Correlation coefficients between in vivo digestible dry matter (sheep) and CWC values for corn and sorghum silages were, respectively, 0.63 (P < 0.05) and −0.44 (P < 0.12) for the VS method, −0.29 (P < 0.33) and −0.81 (P < 0.01) for the FH procedure, and −0.54 (P < 0.06) and −0.80 (P < 0.01) for the TEP modification. Use of a 24‐hour TEP prior to normal extraction in neutral detergent produced more easily filtered CWC residues for high‐grain silages than did the VS procedure, and the TEP residues were closer to being starch‐free. The CWC values from TEP and FH procedures were significantly (P < 0.01) correlated (r = 0.77 and 0.90 for corn and sorghum slages, respectively) while those from the TEP and VS procedures were not significantly correlated.

We conclude that the 24‐hour TEP method is superior to the FH procedure for overcoming the filtering and excess starch problems inherent in the VS procedure for CWC analysis of high‐grain silages. In particular, TEP is simpler than FH and it does not extract cell wall proteins that could be removed by the acid‐pepsin phase of the FH procedure.
Infrared Thermometry for Scheduling Irrigation of Corn1
Authors: Clawson Kirk L. , Blad Blaine L.
Published: July 2010

Irrigation scheduling is an increasingly important practice in the management of valuable water resources in agricultural regions. The study reported here was conducted to evaluate the feasibility of scheduling irrigation in corn (Zea mays L.) using canopy temperature data obtained with a hand‐held infrared thermometer (IRT).

Specific objectives of the study were: 1) to determine whether irrigations can be scheduled from crop canopy temperature data and 2) to evaluate the effectiveness of various canopy temperature irrigation scheduling methods through their effects on some plant responses and the soil water balance.

The study was conducted at the Sandhills Agricultural Laboratory located near Tryon, Neb. The soil at the site is classified as a Typic Ustipsamment (Valentine fine sand). The range in temperature of six readings made with an IRT—defined as the canopy temperature variability (CTV)—in a fully irrigated reference plot (WW) was less than 0.7 C. As the temperature difference between a water‐stressed plot and the WW plot increased so did CTV values until a critical stress level was reached beyond which CTV values stabilized. The onset of water stress can, therefore, be signaled when CTV values exceed 0.7 C.

Observations of CTV were the basis for one type of irrigation scheduling procedure. Irrigation was initiated when the range of six measurments in a plot exceeded 0.7 C. A second procedure consisted of comparing the difference between the average canopy temperature of the well‐watered plot (WW) with that of the plot to be scheduled. Irrigations were initiated when plot temperatures became either 1.0 (1SMW; SWM = Stressed Minus Well‐watered) or 3.0 C (3SMW) warmer than the well‐watered plot.

A total of 283 mm of irrigation water was applied to the WW plot whereas the CTV plot received 127 mm. By the end of the growing season almost all available water had been extracted from the soil in the temperature scheduled plots but the soil profile remained near field capacity in the WW plot. This suggests that during the growing season soil water was most effectively used in the temperature scheduled plots.

Grain yields (Y) were reduced in the order of increasing water stress as follows: YWW > YCTV > Y1SMW > Y3SMW > YDL YDL is the yield from a dryland (DL) plot which received no supplemental irrigation. Yields of grain in the CTV treatment were slightly lower than in the WW plot, but not significantly so. This suggests that plants in the CTV plot received adequate water. Grain yields in the other temperature‐scheduled plots were significantly reduced below those of the WW plot. However, only about 50 to 60 mm of irrigation water were applied to these plots.
Yield and Yield Components of Four Spring Wheat Cultivars Grown Under Three Tillage Systems1
Authors: Ciha A. J.
Published: July 2010

Soil erosion is a serious problem in the wheat (Triticum aestivum L.) producing areas of the Palouse Region of the Pacific Northwest. A field study was conducted under three environmental conditions [a Palouse silt loam (Pachic Ultic Haploxerolls, fine‐silty, mixed, mesic) during 1980 and an Athena silt loam (Pachic Haploxerolls, fine‐silty, mixed, mesic) during 1979 and 1980] to determine the effects of three tillage systems on grain yield and yield components of four soft white spring wheat cultivars, WS‐1, Urquie, Fielder, and Walladay. The tests were conducted using conventional (fall plow and spring disk), conservation (fall chisel and spring disk), and no‐tillage (standing stubble) tillage systems.

Average grain yields with no‐tillage and conservation tillage were significantly greater than yields using conventional tillage. No‐tillage increased test weights while reducing tillage operations significantly reduced the number of spikelets per head, but increased the 100‐seed weight. Tillage practice had no significant influence on heads/m2, seeds per spikelet or seeds per head. Environment significantly influenced all yield components but not grain yield itself.

There were significant differences in yield and yield components among the cultivars examined. Cultivar ✕ tillage interaction for yield (p ≤ 0.06) and test weight (p ≤ 0.03) were significant when examined across all environments. These findings show that no‐tillage spring wheat yields were equal to or greater than that obtained with conventional tillage. Significant cultivar ✕ tillage interactions for yield and test weight emphasize the need to evaluate individual spring wheat cultivars for specific tillage conditions.