bluuebunny/crossref_metadata_2025 huggingface dataset:
Cottonseed Density: Associated Physical and Chemical Properties of 10 Cultivars1
Authors: Bartee S. N. , Krieg D. R.
Published: July 2010

Recent studies have indicated that cottonseed (Gossypium hirsutum L.) germination and seedling vigor are more closely related to seed density than to any other physical properties such as size or weight. This study was undertaken to determine the physical and chemical differences among seed of different densities within a cultivar and among seed of the same density between cultivars. The primary objective was to relate physical or chemical properties to seed density and to offer an explanation for the reported correlation between seed density, germination, and seedling vigor. Cottonseed of 10 cultivars grown on the Texas High Plains were separated into 4 density groups using a pneumatic separator and increasing air velocities. Separation of seed by density was somewhat independent of cultivar; whereas, seed weight was highly dependent on the cultivar. As seed density increased, the proportion of the total seed weight attributable to the embryo increased from 50% to 65% across all cultivars. The lipid concentration increased significantly from the lowest to the second density group, then remained essentially constant thereafter. All chemical constituents increased significantly when expressed on the basis of seed content. A significant cultivar effect existed within each density group with respect to the quantity of material present.

Seed density was a good indication of seed maturity, as shown by the ratios of embryo weight to total seed weight. Although the concentrations of the various chemical constituents were only slightly affected, the quantity of both organic and inorganic material available to the germinating seedling was increased as seed density increased.
Simple Procedure for Quantitative Analysis of Turfgrass Color1
Authors: Johnson G. V.
Published: July 2010

Assessments of turfgrass responses to environment, management, and culture are most often subjective, visual estimates. A simple procedure, based on methanol extraction of chlorophyll from dried turfgrass clippings, was developed to provide an objective quantitative measure of turf color. Extracted chlorophyll (chlorophyll index, CI) ranged from about 4 to 10 mg/g for ‘Penncross’ creeping bentgrass (Agrostis palustris Huds.) containing from 3 to 5.2% N. The procedure was validated by linear correlation (r3 = 0.77 to 0.90) of CI and % N values. The procedure adapts easily to routine use because it uses common laboratory instruments and is not time‐consuming. The resulting values are not confounded by turf density, cover, or thatch.
Winter Wheat Response to Barrier‐Induced Microclimate1
Authors: Skidmore E. L. , Hagen L. J. , Naylor D. G. , Teare I. D.
Published: July 2010

The purpose of this research was to investigate morphological and physiological response of winter wheat (Triticum aestivum L.) to microclimate induced by a slatfence wind barrier. Six varieties of wheat were grown in 90‐m‐long plots running perpendicular to centrally placed, east‐west barriers. Meteorological conditions and plant response were observed on selected days. Stomatal resistance and leaf water potential were measured with stomatal resistance meter and pressure bomb, respectively. Rate of photosynthesis was evaluated by determining uptake of labeled CO2. When environmental conditions were conducive to plant water stress, the plants in the sheltered area had significantly lower stomatal diffusive resistance, tended to have higher leaf‐water potential, and photosynthesized at an equal or significantly greater rate than those in the open field, even though plants in shelter contained 24%less leaf chlorophyll than those in open field. On days when water stress was low, the difference in plant responses between open field and shelter was generally nonsignificant. The plants in the sheltered area generally grew taller, had larger leaves, and had improved water‐stress relationships compared with those in open field. Yet, the grain yields were not consistently increased for the growing environment at Manhattan, Kansas.
Line Source Carbon Dioxide Release. II. Two‐Dimensional Numerical Diffusion Model1
Authors: Allen L. H.
Published: July 2010

Field experiments of CO2 release from a line source left many gaps in our knowledge of CO2 diffusion and how the released gas was lost from the field. The two dimensional vertical flux and horizontal mass flow numedical model presented here showed graphically where and how this loss was occurring. CO2 tended to be lost vertically in a bent‐over plume. Some of the CO2 which was lost vertically would diffuse again into the crop canopy, but this small amount would not increase the canopy CO2 concentration significantly.
Model for Predicting Plant Yield as Influenced by Water Use1
Authors: Hanks R. J.
Published: July 2010

A model has been devised to predict plant yield, both total dry matter and grain, as a function of water use. The model is simple and inexpensive to run on a computer to determine seasonal yields as influenced by irrigation frequency and amount, rainfall, and soil water storage. A good fit of predicted vs measured dry matter yield of sorghum (Sorghum vulgate L.) in Colorado, corn (Zea mays L.) dry matter and grain yields in Israel, and corn grain yields in Nebraska, with various water application treatments, was found. A basic assumption is that the ratio of actual to potential dry matter yield is directly related to the ratio of actual to potential transpiration. Evaporation from the soil is assumed to decrease with the square root of time after wetting as well as with the stage of growth. The shape of the relative yield‐water use curve was found to be sensitive to the evaporation and transpiration assumptions made, but insensitive to the relation used to describe the influence of soil water status on transpiration.
Woody Core Fiber Length, Cellulose Percentage, and Yield Components of Kenaf1
Authors: Adamson W. C. , Bagby M. O.
Published: July 2010

If kenaf lines differ in woody core fiber length and cellulose content, it may be possible to increase the pulp quality of kenaf through breeding. Forty‐eight cultivars, breeding lines, and accessions of cultivated kenaf (Hibiscus cannabinus L.) were analyzed for differences in woody core fiber length and monethanolamine (MEA) cellulose, yield, and plant size. All commercial cultivars of kenaf in the test had relatively short woody core fibers. In the breeding line with the longest woody core fibers, such fibers averaged 0.19 mm longer than those of the longest‐fibered cultivar, a significant difference. Mean woody core fiber length showed negative correlations with yield, plant height, stalk diameter, and MEA cellulose.

Kenaf lines and cultivars did not vary greatly in MEA cellulose, and the commercial cultivars were near the middle of the range. MEA cellulose showed positive correlations with stalk diameter and plant height.
Effects of Tannin Content and Temperature on Storage of Propionic Acid Treated Grain Sorghum1
Authors: Nelson L. R. , Cummins D. G.
Published: July 2010

Grain sorghum [Sorghum bicolor (L.) Moench] can be stored as high‐moisture grain when treated with propionic acid, but it is not known if grain tannin levels affect the amount of acid needed. We planned the investigation to answer this question and to determine the effects of storage temperature on the amount of propionic acid needed for storage of high‐moisture grain sorghum. Grain from a high‐ and a low‐tannin hybrid was stored with 0, 0.5, 1.0, and 1.5% (wet weight) propionic acid for 9 weeks to determine rates required for safe storage. Results showed that high‐tannin grain does not require as much propionic acid (1.0%) for safe high‐moisture storage as does low‐tannin grain (1.5% propionic acid). Low‐tannin grain was stored at low and high temperatures at the above propionic acid rates. Grain stored at the higher temperature spoiled at a faster rate, and results indicated that a higher rate of acid is needed for safe storage at higher temperatures.
Changes in Nutritive Value of Siratro Forage with Age1
Authors: Siewerdt Lotar , Holt Ethan C.
Published: July 2010

Nutritive value characteristics are not as well documented for tropical legumes as for temperate legumes and grasses. ‘Siratro’ (Phaseolus atropurpureus D.C.), a tropical legume, was grown under field conditions in soil classified as a udertic haplustoll with adequate moisture, to determine its nutritive value as affected by plant age. Plant samples, harvested at the ground level every 2 weeks, beginning at the 4th week after establishment and continuing to 26 weeks of age, were separated into leaf, petiole, and stem fractions and analyzed for crude protein (CP) and in vitro digestible dry matter (IVDDM). The nutritional value of Siratro was relatively high at all times, averaging 68% IVDDM for whole plants over a 26‐week period. During the first 18 weeks of growth, leaves averaged 75% IVDDM, ranging from 74 to 77%; stems averaged 61%, ranging from 59 to 63%; and petioles averaged 70%, ranging from 67 to 73%. Crude protein averaged 15% for whole plants and was highest during the first 8 weeks of growth. After the 16th week, CP content remained stable at about 13%. Leaves had the highest CP content, averaging 21% with values ranging from 15 to 23%. All three plant portions showed a declining pattern, with time, in percent of both CP and IVDDM, but the change was less than that found in perennial tropical grasses.
Intercultivar Competition in Sunflower Test Plots1
Authors: Fick G. N. , Swallers C. M.
Published: July 2010

The use of single‐row test plots would greatly facilitate evaluation of experimental sunflower (Helianthus annuus L.) cultivars, particularly when the number of entries is large and seed or land area is limited. The objectives of our study were to obtain information on intercultivar competition, and to determine whether single‐row plots will provide reliable performance data. Eight sunflower cultivars representing diverse agronomic types were grown at Fargo, N. D., in 1972 and 1973. Seed (achene) yields for individual cultivars ranged from 50% higher to 25% lower in one‐row as compared to three‐row plots. These differences were highly significant and indicated the need for bordered plots in preliminary yield testing. One hundred‐ seed weights were also influenced significantly by intercultivar competition in one‐row plots but to a lesser degree than seed yields. Competition did not significantly affect days to 50 percent flowering, plant height, rust reaction, test weight, and seed oil percent, which suggests that these traits can be estimated accurately in single‐row plots.
Hay Preservation and Quality Improvement by Anhydrous Ammonia Treatment1
Authors: Knapp W. R. , Holt D. A. , Lechtenberg V. L.
Published: July 2010

A study was conducted to determine the effectiveness of anhydrous ammonia (NH3) as a preservative to prevent microbial activity and consequent dry matter and digestibility losses in hay that is intentionally or unintentionally stored at moisture levels above 20%. An effective hay preservative would shorten required drying time, thus reducing mechanical losses and risk of weather damages.

Alfalfa (Medicago sativa L.), tall fescue (Festuca arundinacea L.), and ladino clover (Trifolium repens L.)‐tall fescue hays were baled at moisture contents ranging from 16 to 33%. Immediately after baling, gaseous NH3 was applied at 1.0% of the weight of the hay. Temperatures were recorded for three weeks following treatment. Dry matter and digestibility losses were measured in samples taken at baling and after 2 or 3 months in storage.

All of the untreated hays with initial moisture contents above 32% became moldy, heated to 55 C or above, and suffered significant losses in dry matter, in vitro dry matter disappearance (IVDMD), and in vitro cell wall disappearance (IVCWD) during storage. Ammonium N,acid detergent fiber (ADF), neutral detergent fiber (NDF), and ADF‐N percentages increased significantly. Total N percentage of alfalfa hay increased significantly during storage.

NH3 treatment reduced molding, heating, and dry matter loss in stored hay. Significant increases in total N, ammonium‐N, and IVCWD occurred following NH3 treatment. IVDMDfollowing NH3 treatment. IVDMDfollowing NH3 treatment. IVDMDfollowing NH3 treatment. IVDMD decreased during storage but remained higher than in untreated hay. Animals readily consumed the ammoniated hay.

NH3 has the potential to preserve hay that is too wet to store without a preservative. In addition, ammoniation may improve hay quality by increasing total N content and cell wall digestibility. Ammoniation of highly lignified, low N materials such as corn stalks, corn cobs, or straw might significantly improve nutritional quality of these materials.
Seed Production of Kentucky Bluegrass Associated With Age of Stand1
Authors: Canode C. L. , Law A. G.
Published: July 2010

Perennial cool‐season grasses generally show a characteristic decline in seed yield associated with age of stand. This study was designed to document the effect of age of stand on seed yield and associated plant growth characteristics. Clones of ‘PNW 602’ Kentucky bluegrass (Poa pratensis L.) were planted in spacings of 30, 60, and 90 cm each year for 5 successive years to produce 5 chronological‐age crops which could be harvested in the same growing season.

There was no significant difference in the five‐crop average seed yields for the three plant spacings. The highest seed yields (over 500 kg/ha) were secured in the first and second crops for plants spaced at 30 and 60 cm and in the fourth crop (467 kg/ha) for plants spaced at 90 cm. The fifth‐crop seed yields were 49, 37, and 62% of the production of the high‐yielding crops for the 30, 60, and 90‐cm spacings, respectively. These data contained no evidence that plant spacing would affect the decline in Kentucky bluegrass seed production associated with increased age of stand.

The decline in seed yield of Kentucky bluegrass as the plants aged was associated with declines in forage yield, plant height, number of panicles, root and rhizome production, and etiolated regrowth. Seed weight/panicle showed a tendency to decline with age of stand but had a strong negative association with panicle numbers.

The data indicate that good quality seed can be produced from older Kentucky bluegrass stands. Seed weight did not show a decrease associated with age of stand but tended to have a negative association with seed yield. Germination of seed tended to decrease with age of stand with significant reduction in the fifth crop of the 30 and 60‐cm spacings.
Advection Modification of the Priestley and Taylor Evapotranspiration Formula1
Authors: Jury W. A. , Tanner C. B.
Published: July 2010

The empirical formula of Priestly and Taylor (1972) relating the evapotranspiration from a well‐watered surface to the net radiation and a function of the air temperature is modified to include a saturation deficit term to account for high local advection. The model is tested on two seasons of daily evapotranspiration measurements over irrigated potatoes (Solarium tuberosum L.), resulting in good agreement and a substantial improvement over the unmodified formula. Alfalfa (Medicago saliva L.) measurements are also represented well by the model, but no better than by the Priestley‐Taylor formula calibrated during a period of high advection.
Effect of Cultural Practices on Grain Yield and Yield Components in Irrigated Wheat1
Authors: Day A. D. , Alemu Aschalew , Jackson E. B.
Published: July 2010

Since wheat (Triticum aestivum L.) is now grown on beds in the southwestern U.S., experiments were conducted at Yuma, Ariz., to study effects of planting methods, seeding rates, and row positions on beds on the yield and quality of grain from wheat. Two planting methods (on the flat and on beds), three seeding rates (29, 58, and 87 kg/ha), and four row positions on beds (north, south, east, and west) were observed.

Flat and bed methods of planting resulted in similar wheat grain yields and grain volume weights. The low rate of seeding resulted in more wheat seed per head and fewer heads/unit area than did the higher rates of seeding. The net effect of seeding rates on seed weight and grain yield in both flat and bed plantings was not significant.

Wheat grown on beds with an east‐west orientation produced more heads per unit area, more seed head, and higher grain yields than did wheat planted on beds with a north‐south orientation. The south row position on east‐west beds resulted in more heads/unit area, more seed/head, and higher grain yields than did the north row position. Row position on east‐west beds had no significant effect on seed weight.

When wheat was grown on north‐south beds higher rates of seeding resulted in heavier seeds than did the lower rate; however, heads/unit area, seed/head, and grain yields were not influenced by seeding rates. Although west rows produced more seed/head and heavier seeds than did east rows, row position on north‐south beds had no effect on heads per unit area and grain yields.
Analysis of the Carbon and Nitrogen Limitations to Soybean Yield1
Authors: Sinclair T. R. , de Wit C. T.
Published: July 2010

Soybeans are hypothesized to be “self‐destructive” since they apparently need to translocate large amounts of nitrogen from vegetative tissues during seed‐fill to sustain seed growth. To assess the possible limitations of this characteristic on soybean seed yield, a simple, dynamic simulation model is developed which accounts for the availability of nitrogen and photosynthate within the plant. The simulations show that the duration of seedfill and seed yield is clearly limited by the self‐destructive characteristic. Increased availability of nitrogen within the plant is required for significant increases in soybean yields. Possible alterations of the model required to mimic actual soybean seed growth are presented.
Some Relationships of a Plastic Mulch to Sweet Corn Maturity1
Authors: Andrew R. H. , Schlough D. A. , Tenpas G. H.
Published: July 2010

Plastic mulch or polyethylene film has been used experimentally as a ground cover to hasten development for a number of crops. In this research attention was given to its potential use for sweet corn (Zea mays L.) as related to cultivar and insolation.

Two sweet corn hybrids with a 15‐day range in relative maturity were grown in 2 years under a clear plastic mulch in northern Wisconsin for comparison with traditional culture at that location and in the south central part of the state. Soil temperatures at a 7.6 cm depth were recorded by thermographs with bulb elements and related to official air temperatures. The periods from planting until silking and harvest were measured in terms of days and thermal units.

Silking and harvest dates were advanced on the average by 6 days and up to 9 days with the use of a plastic ground cover. The effect of plastic was relatively greater during cool days, on minimum temperatures, and in the cool year. Its effect was greater earlier in the season and for the smaller hybrid, because of less plant shading.

Fewer thermal units, although more days, were required to achieve comparable maturity at the northern as compared with the southern location in the cool year, but more thermal units as well as days were required at the northern location in the warm year. While maturity advanced more rapidly with increasing temperature, the advance was not directly commensurate with air temperature on a diurnal, seasonal, or locational basis.
Winter Wheat Yield Reduction from Interference by Italian Ryegrass1
Authors: Appleby A. P. , Olson P. D. , Colbert D. R.
Published: July 2010

Italian ryegrass (Lolium multiflorum Lam.) is a serious and widespread weed problem in grain fields of western Oregon and Washington. Field studies were conducted to measure effects of Italian ryegrass interference on winter wheat (Triticum aestivum L.) yields. Wheat cultivars used were ‘Nugaines,’ ‘Druchamp,’ ‘Hyslop,’ and ‘Yamhill.’ Ryegrass densities ranging from 0 to approximately 100 plants/m2 were established by hand distribution on the soil surface, followed by harrowing. Urea fertilizer was applied in the spring at 56, 112, and 168 kg of N/ha.

As ryegrass densities increased, wheat grain yields decreased. In one experiment, wheat grain yield was reduced by 4,100 kg/ha when the ryegrass density was increased from 0.7 to 93 plants/m2. Interference caused greater percentage reductions in wheat yields at 168 kg N/ha than at 56 kg N/ha when ryegrass densities were high. The percentage of yield reduction tended to be higher in short wheat cultivars, Nugaines and Hyslop, than in tall cultivars, Druchamp and Yamhill. When no weed control measures were used, ryegrass infestations in the 1970 crop caused wheat yield reductions in the 1971 crop. This was due to higher ryegrass densities in 1971 in plots where the heaviest ryegrass densities occurred in 1970. When ryegrass was controlled with diuron [3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea] in 1971, no carry‐over effects from previous ryegrass infestations could be measured. Results obtained in these studies illustrate the importance of good ryegrass control in winter wheat management systems.
Responses of Three Peanut Cultivars to Gypsum1
Authors: Walker Milton E. , Keisling Terry C. , Drexler J. Stanley
Published: July 2010

The differential response of peanut (Arachis hypogaea L.) cultivars to soil applications of Ca has been established for many years. Recent research reports, however, have indicated that peanut cultivars respond similarly to Ca application. This may result in part from new peanut cultivars differing in their response to Ca. Experiments were therefore conducted on a low Ca soil to measure responses of three commonly grown peanut cultivars to soil‐applied Ca.

Gypsum was applied at 0 and 1,121 kg/ha in a split‐plot design using ‘Florunner,’ ‘Florigiant,’ and ‘NC‐Fla 14’ peanut cultivars. Other nutrients were applied uniformly. Yield, sound mature kernels (SMK), extra large kernels (ELK), and % N and oil in the seed were measured.

Results from this experiment show that gypsum had no effect on yield or sound mature kernels of Florunner peanuts. Florunner peanuts produced higher yields and grades than Florigiant or NC‐Fla 14, regardless of treatments. Gypsum application to Florigiant and NC‐Fla 14 peanuts increased yields, sound mature kernels, and extra large kernels. In general, gypsum increased the % oil in all cultivars. Florigiant contained less oil than the other cultivars. Nitrogen content of the seed of all cultivars was reduced by gypsum application. These data indicate that on low Ca soils Florunner peanuts can produce higher yields and quality with or without gypsum, while Florigiant and NC‐Fla 14 need gypsum fertilization to increase yield and improve quality.
Evapotranspiration Model Tested for Soybean and Sorghum1
Authors: Kanemasu E. T. , Stone L. R. , Powers W. L.
Published: July 2010

A reliable, simple method of estimating daily evapotranspiration (ET) is required for a number of agricultural and hydrological studies. We present tests of an evapotranspiration model by comparison with lysimetric observations. Daily ET rates estimated by the model for sorghum [Sorghum bicolor (L.) Moench] and soybean [Glycine max (L.) Merr.] were within 2 mm of lysimetric estimates. The model uses daily inputs of temperature, solar radiation, and leaf area index; included in the output are estimates of transpiration and evaporation. Seasonal evaporation contributed about 15 to 20% of the evapotranspiration. Evapotranspiration was about 10% greater from soybean than from sorghum.
Measurement of Crop Temperature by Leaf Thermocouple, Infrared Thermometry and Remotely Sensed Thermal Imagery1
Authors: Blad Blaine L. , Rosenberg Norman J.
Published: July 2010

Crop temperature of alfalfa (Medicago sativa L.) was measured with an infrared thermometer (TIR) and with leaf thermocouples (TTC). TTC of corn (Zea mays L.) was also measured. Thermal imagery of the alfalfa research sites and neighboring fields was also obtained. The study was undertaken to determine daily patterns of crop temperature, to compare crop and air temperature, to determine whether or not alfalfa and corn are consumers or generators of sensible heat in the climate of the central Great Plains, and to determine the utility of using remotely sensed thermal imagery to measure crop temperature.

TTC and TIR were often closer than 0.5 C but the agreement was not consistently better than 1 to 2 C. Measurements indicated that daytime thermal inversions existed over alfalfa fields during several hours on the days studied. Alfalfa was often 5 to 7 C cooler than air at the 200 cm level in mid and late afternoon. The intensity and duration of the daytime inversions observed in this study indicate that significant quantities of advected sensible heat are supplied to the alfalfa for consumption in evapotranspiration (ET). This finding supports ET results reported by earlier studies of the authors.

The temperature of corn, alfalfa, and air were compared late in the growing season. Even though the corn was irrigated its temperature was consistently higher than that of a nearby alfalfa field. It was also warmer than the air except for short periods in the late afternoon. Unlike alfalfa, corn generated sensible heat and therefore, probably used significantly less water than did the alfalfa.

Quantitative interpretation of the thermal imagery was not possible but imagery obtained in late spring indicated that wheat and alfalfa were at approximately the same temperature and both were cooler than pasture. If the net radiation and crop boundary layer resistance terms are similar for these three crops then the imagery suggests that wheat and alfalfa used water at about the same rate and that pasture used less water than either.
Yield and Uptake Response of Corn to Zinc, as Influenced by Phosphorus Fertilization1
Authors: Takkar P. N. , Mann M. S. , Bansal R. L. , Randhawa N. S. , Singh Hardev
Published: July 2010

Zinc deficiency has been reported after P fertilization of corn (Zea mays L.), but reasons for this deficiency are not clear. A field experiment was conducted for 3 years from 1970 to 1973 with a fixed wheat‐corn rotation to determine the effect of P and Zn fertilization on corn yield, uptake, and translocation of Zn, and to evaluate the parameters that would monitor best the P‐Zn interaction in corn. Five rates of P (0, 22, 44, 66, and 88 kg of P/ha), and four rates of Zn (0, 11, 22, and 44 kg of Zn/ha) were applied to P and Zn‐deficient soil (Ustipsamments) using a split‐plot design (with P in the main plots and Zn in the subplots). P was applied to all the six crops and Zn only to the first and second crops.

Optimum response of corn to P was observed at 44 kg of P/ha. The high P supply beyond the optimum P rate produced severe Zn‐deficiency symptoms in treatments without added Zn and a significant decrease in grain and stover yields. This resulted from a significant decrease of Zn and a significant increase of P concentration in the shoots of the plant with a high P supply. An increase in the supply of Zn alleviated its deficiency symptoms, significantly increased Zn concentration and its uptake and resulted in a significant increase in growth and yield. The requirement of Zn increased at high (66 to 88 kg/ha) rates of P fertilization. The main effect of P on Zn utilization by corn was to reduce the rate of Zn entry into the roots and induce zinc deficiency.

The P‐Zn disorder was better related with P/Zn ratio in the soil and in different parts of the corn plant than either with the P or Zn content of the tissues and soil. Values of P/Zn greater than 7.5 in the soil, 245 in grain, 130 in stover, 150 in the leaves (of 25‐day‐old plants) indicated a severe Zn deficiency in corn and a highly significant response to its application. The P/Zn values 4 to 7.5 in the soil, 150 to 245 in the grain, 90 to 130 in the stover, and 100 to 150 in the leaves indicated moderate Zn deficiency or response to its application.
Use and Misuse of Multiple Comparison Procedures1
Authors: Petersen R. G.
Published: July 2010

A number of statistical tests can assist in the interpretation of the results of agronomic experiments. Examination of recent issues of the Agronomy Journal indicates that one of the more popular procedures is to use some form of a multiple comparison test to look at pairwise comparisons among the treatment means. In this paper use of these tests is examined, and alternative procedures are suggested for situations in which multiple comparison tests are inappropriate. These are illustrated with examples extracted from the Agronomy Journal. In general, multiple comparison procedures are appropriate for “data snooping” following experiments with unstructured qualitative treatments. Multiple comparison tests are almost never appropriate for experiments in which 1) the treatments are graded levels of a quantitative variable, 2) for factorial combinations of two or more factors at two or more levels, and 3) for quantitative treatments where previously formulated linear combinations of treatment means are of particular interest.
Relationship Between Corn Yield, Expressed as a Percentage of Maximum, and the N Percentage in the Grain. I. Various N‐rate Experiments1
Authors: Pierre W. H. , Dumenil Lloyd , Jolley Von D. , Webb J. R. , Shrader W. D.
Published: July 2010

The objective of this investigation was to determine if the N content of the grain of corn (Zea mays L.) could be used as a measure of N sufficiency of the crop for maximum yield. This was done by studying the relationship between yield, expressed as a percentage of maximum, and the N percentage in the grain. The relationship was determined from the data of 13 site‐years of six N‐rate experiments in Iowa and from data reported in the literature.

Two methods, a graphical and a regression method, were developed to relate the yield of corn, expressed as a percentage of maximum, and the N percentage in the grain. Good agreement was found between the two methods for obtaining maximum yields and N percentages at various percentages of maximum yield. The average critical N percentages, or percentages at maximum yield, by the graphical and regression methods, were 1.52% and 1.54%, respectively, for the Iowa experiments. The data calculated from the experiments reported in the literature were in general agreement with the Iowa data.

The standard error of the mean of the critical N percentages (graphical method) for the 13 site‐years of Iowa experiments was 0.016% and, for the 24 site‐years of the non‐Iowa experiments, it was 0.022%. Some of the variability may have been caused by differences among the 23 hybrids represented in the experiments. Moisture stress, plant density, and adequacy of other nutrients had little or no demonstrable effect on the relative yield — percent N relationship.

It is concluded that the relative yield — percent N relationship offers a promising and practical basis for estimating N sufficiency and the N requirement for maximum yield, or for an economic optimum yield.
Response of Oats to Water Deficit. I. Physiological Characteristics1
Authors: Sandhu B. S. , Horton M. L.
Published: July 2010

Although an insufficient supply of water is commonly associated with reduced crop yields, the manner in which water deficits affect the functioning of many common field crops is not well established. The purpose of this study was to quantify the effects of a water deficit on some physiological processes of spring oats (Avena sativa L. ‘Jaycee’). The plants were subjected to water deficits under a field environment for 9 to 11 days at the boot stage, at anthesis through early grain formation stage, and at both stages in combination. Relative leaf water content (RLWC) as determined by the relative turgidity method was used as a measure of water deficit. Leaf diffusion resistance (LDR) was monitored using a diffusion porometer. The net photosynthetic rate (NPR) of the oat plants was determined using an infrared gas analyzer. Severe water stress at all stages of development studied caused about an 80% decline in NPR. LDR increased with a decrease in RLWC. Stress during boot stage reduced the photosynthetic sensivity of the plants to subsequent stress at the anthesis through early grain formation stage. On rewatering, LDR and RLWC recovered completely within 1 to 6 days; however, the net photosynthetic rate of plants stressed at the anthesis through grain formation stage showed a more gradual and incomplete recovery than plants stressed at other stages. The plants stressed during boot stage alone, but adequately watered thereafter, exhibited significantly higher NPR than the control plants. The results indicate that leaf diffusion resistance and net photosynthetic rate of oats show acute sensitivity to plant water deficits. Hence, these parameters hold promise as aids in determining permissible water deficit limits and in irrigation scheduling.
Alfalfa Root Nodule Distribution and Inhibition of Nitrogen Fixation by Heat1
Authors: Munns D. N. , Fogle V. W. , Hallock B. G.
Published: July 2010

Greenhouse and field trials were done to test the likelihood that impairment of N fixation contributes to late summer decline in productivity of Medicago sativa L.

In greenhouse solution cultures, acetylene reduction and N fixation by nodules were impaired by daily heating of the culture solutions to 32 C, and eliminated by repeated exposures to 36 C or a single exposure to 40 C. However, in a field trial conducted on a Yolo silt loam (Typic Xerorthent, fine silty mixed non‐acid thermic), alfalfa showed no signs of N deficiency and responded little to application of 500 kg NH4NO3/ha although soil temperatures above 32 C were recorded for 5 to 6 hours each day during a 6‐day hot spell following a late summer cut, with peak soil temperatures above 40 C at 2 cm depth.

Lack of response in the field trial is explained by observations of temperature profiles and nodule distribution. Only the topmost 5 cm of soil heated above 30 C, and this contained less than 10% of the nodules. Most of the nodules were at depth 10 to 30 cm, and remained at nearly optimal temperatures of 22 C to 27 C.

Heat inhibition of nitrogen fixation should not significantly limit growth of alfalfa in the field unless nodule‐formation is constrained to shallow depths.
Defoliation Effects on Corn Hybrids Adapted to the Northern Corn Belt1
Authors: Hicks D. R. , Nelson W. W. , Ford J. H.
Published: July 2010

Hail damage to corn (Zea mays L.) in the northern corn belt is assessed using loss charts based upon research conducted in the central corn belt. We conducted an experiment to determine the effect of leaf blade defoliation at varying stages of development on corn grain yield, test weight, kernel weight, shelling percentage, and ear moisture content at harvest. Plants were completely defoliated (blade only) at the five‐leaf stage (LS). Both 50 and 100% of leaf blades were removed at 13 LS, tasseling, early milk, and full dent growth stages. The 3‐year study included two hybrids, a full‐season [115 relative maturity (RM)] and a short‐season (90 RM) hybrid.

Complete leaf removal of the 90‐RM hybrid at the five LS caused an average 48% grain yield increase compared with no defoliation. The same treatment caused an average 7% yield reduction of the 115‐RM hybrid. At later defoliation dates, grain yield reductions were greater for plants that were 100% defoliated than for plants that were 50% defoliated. The yield responses to defoliation at various stages of development for both 50 and 100% leaf blade removal were similar for the 90‐ and 115‐RM hybrids. Although yield reductions were comparable when the two hybrids were 100% defoliated for all stages of development, 50% defoliation did not cause as great a yield reduction on the 90‐RM hybrid as it did on the 115‐RM hybrid. In general, observed grain yield losses from defoliation after the five LS were similar to those given in loss charts used by crop‐hail insurance adjusters.

Kernel weight, test weight, and shelling percentage were not affected when plants were defoliated, either 90 or 100%, prior to tasseling. Leaf removal after tasseling, especially 100%, lowered kernel weight, test weight, and shelling percentage of both hybrids. We did not record kernel number per ear which must account for the yield increase resulting from five LS defoliation because kernel size and ear number per plot were not affected.

In general, ear moisture content at harvest was slightly increased due to defoliation imposed prior to tasseling and decreased due to defoliation after tasseling which indicates defoliation before tasseling slightly delayed maturity and defoliation after tasseling hastened maturity, as measured by ear moisture content at harvest.
Comparison of Five Methods for Characterizing Soybean Rooting Density and Development1
Authors: Böhm W. , Maduakor H. , Taylor H. M.
Published: July 2010

Many methods are used to study plant root system development and function. Most methods are tedious and time‐consuming. Some require expensive, sophisticated equipment and frequently require highly trained operators. Few studies are published where several methods are compared for their time requirements, equipment needs, soil applicability, and validity of the results. This study determined usefulness of five methods for characterizing soybean (Glycine max (L.) Merr.) rooting depth and density in a loess [fine, silty, mixed (calcareous) mesic family of Typic Udorthents] soil. The methods were: (a) soil water‐depletion, (b) framed‐monolith and pinboard, (c) core‐sampling, (d) mini‐rhizotron, and (e) trench‐profile. Each method was used or attempted on several dates during the 1975 growing season. The soil water‐depletion method was fast, required only simple equipment, and provided satisfactory estimates of rooting depth but did not provide reliable estimates of rooting density. The framed‐monolith method was very time‐consuming, but provided quantitative estimates of rooting density with depth and could have provided rooting density estimates with distance from the row. The core‐sampling method was faster than the framed‐monolith method. Cores could be obtained either with a hand‐turned bucket auger or with a coring machine, but several profiles were required to obtain rooting density distributions with depth and distance from the row. The mini‐rhizotron method was fast, but did not provide accurate results, presumably because the mini‐rhizotrons were installed too late. The trench‐profile method provided semiquantitative estimates of rooting density with depth and distance from the row. The trench‐profile method was rapid and required no time‐consuming separation of live roots from debris of previous years. The hand‐augered core, soil water‐depletion, and the trench‐profile methods could be used through the entire growing season, but the framed‐monolith and the mechanized‐core methods were not satisfactory during a drought period because the soil column collapsed during sampling.
Sterility in Rice Cultivars as Influenced by MSMA Rate and Water Management1
Authors: Wells B. R. , Gilmour J. T.
Published: July 2010

In recent years an expansion of rice (Oryza sativa L.) acreage in Arkansas has resulted in rice being produced on soils with a history of cotton production. Most of these cotton soils have had repeated applications of monosodium methanearsonate (MSMA) as a herbicide. There is some evidence that arsenical residues in the soil can lead to sterility in rice. In an effort to answer this question, we conducted a field experiment on a Crowley silt loam soil (Typic Albaqualf) in 1975 to evaluate the influence of MSMA on plant growth and yield of rice. Treatments included two water management regimes (continuous flood vs. one drain and dry), three levels of MSMA [0, 1.1, and 11.2 kg/ha of arsenic (As)] and 15 rice cultivars and experimental strains differing in susceptibility to straighthead disease (abnormally developed or sterile flowers resulting in reduced grain yields).

Soil samples taken 65 days after arsenic application showed that As remained in the rice root zone. Vegetative growth prior to panicle initiation was not affected by any of the treatments; however, visual observations made near maturity showed that where MSMA had induced sterility, the plants were dark green suggestive of straighthead. Reproductive growth as shown by panicle weights and sterility ratings was affected most by high MSMA rates and continuous flooding. Under continuous flood, panicle weights were reduced and sterility ratings increased as MSMA rate increased. This effect was more pronounced in cultivars most susceptible to straighthead and was minimized by draining the flood and drying the soil. This data suggests that the MSMA residues induced straighthead. A significant and similar relationship was found between panicle weights and sterility ratings at maturity for both water management regimes.
Effect of K on N Utilization by Spring Wheat During Grain Protein Formation1
Authors: Koch K. , Mengel K.
Published: July 2010

Several researchers reported that high nitrogen rates for cereals require also an ample potassium supply in order to produce maximum grain yields. The physiological relationships between N and K in grain production are not yet completely understood. For this reason experiments have been carried out to study the effect of K on the translocation of N in wheat plants and its incorporation into the grains during the grain filling period. Spring wheat (Triticum aestivum L. cv. ‘Kolibri’) was gown in solution culture at two K levels throughout the growing period and at three N levels during the reproductive stage. Nitrogen was labeled 15N with the beginning of anthesis.

Plants at the higher K rate produced more vegetative dry matter, higher grain yields, fewer unproductive tillers and improved translocation of N from the vegetative plant parts into the grain. Between 87.4 and 89.0% of the N absorbed during the reproductive stage was present in the grain of plants which had received the higher K supply. In plants grown with the lower K level the percentage ranged from 78.9 to 81.0%. This improved translocation of nitrogenous compounds from the various plant parts to the grain caused by K resulted mainly in higher contents of prolamin, glutelin, and soluble amino acids in the grain. For the content of albumin and globulin the reverse was true. All four grain protein fractions showed the same degree of N labeling indicating that none of the four protein fractions was preferably supplied by the N absorbed during the reproductive stage. The label of the soluble amino acids in the grain was lower than that of the grain proteins. It is assumed that at the last stage of grain filling a relatively high amount of N from senescing plant parts is exploited for grain filling, thus diluting the N taken up from the nutrient solution.

The higher N levels applied during the reproductive stage had a negative rather than a positive effect on grain yield. The additional N increased mainly the content of soluble amino acids, prolamin, and glutelin in the grain.
Response of Soybeans to Overseeding Followed by Plant Thinning at Various Growth Stages1
Authors: Boerma H. R.
Published: July 2010

Accurate field plot technique is an important factor in soybean [Glycine max (L.) Merr.] experimentation. The practice of overseeding followed by plant thinning has become a common practice for many experiments involving the estimation of physiological parameters, and for some experiments designed to measure seed yield. In most cases the results of these experiments are extended to the general field situation. The purpose of the present study was to determine the growth stage at which thinning of overseeded plots must be accomplished to provide similar results to direct seeding at the desired population rate.

Three soybean cultivars, in maturity groups VI, VII, and VIII, were overseeded at 53 viable seeds/m in rows spaced 0.96 m apart and different plots were thinned to 23 plants/m for 8 consecutive weeks following emergence. The experiment also included a control which was seeded at 26 viable seeds/m and obtained a plant population of 23 plants/m. The results indicated that the week of thinning had a significant effect on seed yield, nodes/ plant, and branches/plant. Seed yield and nodes/plant decreased at thinnings after the V4 growth stage (2 weeks after emergence) and branches/plant at thinnings at the V5 growth stage (3 weeks after emergence). The cultivar × thinning week interaction across years was nonsignificant for all characteristics. There was a significant year × week of thinning interaction for plant height at maturity and lodging. To obtain the same seed yield and general plant characteristics expected from seeding at the desired population rate, overseeded plots should be thinned prior to the V5 growth stage.
Relationship between Fibrous Components and In vitro Dry Matter Digestibility of Autumn‐saved Grasses1
Authors: Archer K. A. , Decker A. M.
Published: July 2010

Chemical techniques for the determination of cell wall constituents and cell contents have been developed which provide relatively quick, convenient methods for predicting the digestibility of forage samples. These purely chemical laboratory methods may not be as reliable as in vivo or in vitro techniques for forage quality evaluations but they do not require the maintenance of digestion stalls or fistulated animals. There is a need for a better understanding of the relationships between chemical determinations and the actual feed value of forage samples. The specific objective of this paper was to investigate the relationship between in vitro dry matter digestibility and chemical analyses of cell walls and cell contents for evaluating the digestibility of autumn‐saved forage grass samples.

Forage samples of ‘KY‐31’ tall fescue (Festuca arundinacea Schreb.) and ‘Potomac’ orchardgrass (Dactylis glomerata L.), collected from two field experiments were used for these quality evaluations. These field experiments were designed to measure the influence of nitrogen fertilization and soil temperature on cell wall constituents and in vitro dry matter digestibility of previously unharvested fall accumulated growth sampled at early, medium and late fall dates. Samples were analyzed for neutral detergent fiber, acid detergent fiber, cellulose, hemicelouse, lignin and silica. In vitro digestable dry (IVDMD) matter was also determined for each forage sample.

Fiber, lignin, and silica contents of autumn‐saved forage samples were all highly correlated with IVDMD, and equations were developed to predict IVDMD from these chemical constituents. The following summative equation is proposed for the calculation of IVDMD: IVDMD = 0.98 (100 − NDF) + NDF (91.1 − 1.43 (LIG + SIL) / ADF)