bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in Chemical Composition of Kentucky Bluegrass and Tall Fescue Herbages Following N Fertilization1
Authors: Hojjati S. M. , Templeton W. C. , Taylor T. H.
Published: July 2010

Most research on N fertilization of grasslands has dealt with yield responses, with much less attention to feed quality. These field studies were undertaken to determine the effects of four rates of N and harvest time on levels of crude protein (CP), P, Ca, K, and Mg in spring and early‐summer aftermaths of Kentucky bluegrass (Poa protensis L.) and tall fescue (Festuca arundinacea Schreb.) grown on Typic Paleudults soil.

NH4NO3 was applied to supply 50, 100, 150, and 200 kg N/ha. The fertilizer treatments were replicated in time (9 April, 30 April, and 21 May), as well as space, to introduce different environmental conditions and plant development stages. Herbage samples were collected weekly during three 6‐week periods following fertilization.

CP in both grasses increased with larger applications of N, reaching peak values of 32.8 and 32.5% in bluegrass and tall fescue, respectively, in the first growth period, 2 weeks after fertilization. Minimum values of 11.8 and 9.7% occurred in 6‐week growths of bluegrass and fescue, respectively, with 50 kg N/ha.

Effects of N on P concentrations were inconsistent. Concentrations of Ca and K in both grasses rose with increasing N, as did Mg in the first two growth periods. In the second half of period 3, high N decreased Mg concentrations. The latter effect and the fact that high levels of N reduce Mg availability to animals indicate an increased likelihood of tetany, especially with bluegrass, when large amounts of N are applied in spring.

Elemental concentrations of Ca, P, and K in both grasses appeared adequate to meet ruminant requirements, irrespective of N application. With the possible exception of K, none of the four elements appeared to be limiting for plant growth. Bluegrass herbage, especially in growth period 3, often contained less than 2.0% K.

Ca/P ratios increased with higher applications of N in periods 2 and 3, but not in 1. Effects of N on K/(Ca+Mg) ratios were inconsistent, but values only once reached the critical level of 2.2.
Root Growth and Nutrient Uptake Characteristics of Some Cowpea Varieties1
Authors: Adepetu J. A. , Akapa L. K.
Published: July 2010

Efficient utilization of fertilizer P and K by a crop depends, to a large extent, on the amount of roots that contact the fertilizer nutrient, as well as the capacity of the root to absorb the contacted nutrient. In order to find a Nigerian cowpea that utilizes soil and applied nutrients best, five cowpea cultivars commonly cultivated in Nigeria were grown in fertile and N, P, and K deficient soils in the greenhouse. Specific objectives were to determine differences in root growth (length) and nutrient uptake efficiencies of roots (μg/m) among the five cultivars.

To determine the effect of age on the ability of a cowpea plant to utilize soil nutrients, cowpea cultivar ‘H113–4’ was grown for 30 days in solution culture and changes in root length and nutrient uptake rates (μg/m‐day) as functions of plant age were evaluated. When grown in fertile soil, ‘Ife‐brown’, H113–4, and Westbred cultivars had significantly greater root lengths (17.5, 17.2, and 16.7 m respectively) than ‘1534’ (14.3 m.); while ‘Crimson's’ root length (15.4 m) was intermediate. In the N‐P‐K‐ deficient soil, however, Crimson had the most extensive root system (19 m). Apparently, H113–4 had the greatest total uptake of P, K, and Ca (9.9 mg), K uptake efficiency (360 μg K/m root length), and shoot:root ratio (W/W). Also, the P and Ca uptake efficiencies of this cultivar (160 and 75 μg/m respectively), and the dry matter yield (0.94 g) were among the highest. The total length of roots of Hl13–4 was a linear function of plant age (R2 = 0.94) up to 30 days of age. Phosphorus and K uptake rates in solution culture decreased tremendously from 34 μgP/m‐day and 380 μgK/m‐day, at 5 days old, to 8 μgP/m‐day and 95 μgK/m‐day at 30 days, respectively. Deficiency of K in the solution culture markedly reduced P uptake by the root. It is concluded that H1 13ߝ4 variety has superior potential over other cowpea varieties studied for efficient utilization of applied P and K; and that the nutrient absorption capacity of young cowpea roots decreases rapidly with age.
Effects of Intercropping on Soybean N2‐Fixation and Plant Composition on Associated Sorghum and Soybeans1
Authors: Wahua T. A. T. , Miller D. A.
Published: July 2010

Sorghum (Sorghum bicolor (L.) Moench) and soybean (Glycine max (L.) Merrill) are being intercropped in the tropics so that crops more effectively utilize water; there is better weed control, and soil fertility is improved. A field experiment was conducted to determine the effects of sorghum‐soybean intercropping on soybean N2‐fixation and plant composition of both crops. The soil was a Flanagan series, a fine, montmorillonitic, mesic Aquic‐Argiudoll. Soybeans were intercropped with tall and semi‐ dwarf sorghum cultivars at 16 population densities from 1.38 to 33. plants/m2. Soybean N2‐fixation was estimated by acetylene reduction. Various plant parts were analyzed for present N.

Nitrogen‐fixation by soybeans grown with tall sorghum was reduced 99% due to reduction in number of nodules per plant (77%), weight per nodule (50%), and specific nodule activity, SNA, (96%). Soybean dry matter and seed percent oil were also reduced by 87 and 8%, respectively. Soybean percent seed protein and leaf N were unaffected by intercropping.

Soybeans grown with semi‐dwarf sorghum fixed 2.64 times more N than plants in monoculture but produced 40% less dry matter and 3% less oil in seed. Percent seed protein and leaf and stem N of soybeans were unaffected by intercropping. The increase in N2‐fixation was probably due to increases in number of nodules per plant (62%) and SNA (364%). Possible involvement of allelopathy, NO3‐ absorption, delayed senescence, and inter‐ specific mechanical support was considered.

Protein yield of intercropped tall and semi‐dwarf sorghum was reduced by 15 and 71%, respectively. Only in the dwarf cultivar did intercropping increase percent seed protein by 15%. Sorghum grain oil was unaffected by intercropping.
Influence of Fertilizer and Residue Management on Grass Seed Production1
Authors: Canode C. L. , Law A. G.
Published: July 2010

Postharvest residue burning, a standard practice in grass seed production in the Pacific Northwest, may be restricted because of concerns for air quality. This research compares the effects of burning with those of mechanical residue removal on red fescue (Festuca rubra L.), smooth bromegrass (Bromus inermis Leyss.), and crested wheatgrass [Agropyron desertorum (Fisch. ex Link.) Schult.].

The experiments were conducted on a silt loam soil (Pachi Ultic Haploxerolls) as a split‐plot within each grass species. Main plots were three levels of 18‐10‐10‐7 fertilizer applied to supply N at 90, 112. and 135 kg/ha, with an associated increase in P, K, and S. Main plots were split for open burning and two levels of mechanical residue removal. Two crops of red fescue and four seed crops of smooth bromegrass and crested wheatgrass were evaluated.

Average seed yields (kg/ha) for burning compared with mechanical straw removal were 636 vs. 495 for red rescue, 1,122 vs. 848 for smooth bromegrass, and 872 vs. 790 for crested wheatgrass. Straw and stubble removal, compared with straw removal alone, increased seed yield of red rescue and smooth bromegrass, but decreased seed yield of crested wheatgrass.

Interactions of fertilizer rates and residue management were not significant. Increasing the fertilizer rate did not compensate for the reduction in seed yield associated with mechanical removal of residue. Seed yields of smooth bromegrass and crested wheatgrass were increased by high fertilizer rates as the age of stand increased.

The increase in seed production resulting from burning residue apparently was associated with control of downy bromegrass (Bromus tectorum L.) and increased vigor of autumn regrowth. Diseases and insects were of little consequence and probably had little influence on seed yield in these experiments.
Effects of pH, P, and Al on the Growth and Chemical Composition of Crownvetch1
Authors: Vickers J. C. , Zak J. M.
Published: July 2010

Massachusetts roadsides often consist of acid, infertile soil which is subject to erosion when without adequate cover. Crownvetch (Coronilla varia L.) is a legume which has been introduced for the purpose of rapid, attractive, and inexpensive stabilization of such sites. The response of crownvetch to soil acidity and correction of this condition have not been closely examined. This investigation consisted of combining three pH, two phosphorus and three aluminum rates in soil and water culture studies. The objective was to study the effects of the soil treatments on factors of soil acidity, as well as the chemical composition and growth of crownvetch. By studying the relationships among these factors it was hoped to better characterize the acid tolerance and cultural requirements of this species. In both media, mean dry weights increased as pH was increased from 4.2 to 5.4. Yields did not increase further at pH 6.3. Reduced P availability and excess exchangeable soil Mn, which resulted from the high lime level, appear to be involved in restricted plant growth at a soil pH of 6.3. Root Al content was negatively correlated with top weights; however, neither pH nor Al treatments were related to root length in soil and water culture. A mean exchangeable Al level of 4.5 ppm (at the highest Al rate) in soil and 5.0 ppm A (and above) in water culture appreciably diminished the growth rate of crownvetch. The high Al additions in these studies became more of a problem to plant growth at low pH and P conditions. It was found that the soil P application resulted in a lower incidence of symptoms of leaf black spot and enhanced root penetration. Liming this soil to pH 5.4, and applying 75 ppm P (168 kg/ha) significantly benefited the growth crownvetch. Optimum soil Al and Mn levels combined with enhanced Ca and P availability are thought to be major reasons for these benefits.
Use of a Bleach Test to Screen Single‐head Sorghum Selections for the Presence of a Testa Layer1
Authors: Kofoid K. D. , Maranville J. W. , Ross W. M.
Published: July 2010

The development of random mating populations of sorghum [Sorghum bicolor (L.) Moench] has resulted in an increase in the frequency of material with a testa layer. Since the testa layer has been associated with tannin, genotypes with a testa need to be identified in these populations with ease and certainity. Hence, a procedure using KOH and bleach (6% NaOCI by weight) to determine the presence of a testa layer in sorghum was modified for use on single‐head selections and was evaluated for its usefulness as a screening technique.

Three concentrations of KOH:bleach (1:6, 1:5, and 1:4 w/v) at each of three water bath temperatures (50, 60, and 70 C) for three time periods (10, 15, and 20 min) were. tested to determine the optimum conditions for maximum color development of the kernels. Significant main effects were found for genotypes, time, and temperature. Partitioning of the genotype sum of squares into single degree of freedom comparisons showed significant differences between genotypes with and without a testa. Pericarp pigmentation also was found to significantly affect the rating in both the testa and nontesta material. However, this effect was not judged to be detrimental to the determination of presence or absence of a testa layer. Significant differences were found between waxy and yellow endosperm material, but this was probably due to pericarp pigmentation. Significant 2, 3, and 4‐way interactions indicated that no single combination of treatments was optimum for all entries. However, immersing kernels in a concentration of 1:5 (w/v) KOH:bleach at a water bath temperature of 60 C for 15 min resulted in a maximum rating for genotypes with a testa. Use of this procedure allows for the screening of a large number of selections for the presence of a testa layer with relative ease and reliability.
Fungicides in Kentucky Bluegrass Turf: Effects on Thatch and pH1
Authors: Smiley R. W. , Craven M. M.
Published: July 2010

Management of thatch and pH are important aspects of turfgrass culture. The use of disease‐preventive fungicides is a standard practice on highly‐maintained turfgrasses, and fungicides may be toxic to many thatch‐decomposing microorganisms. However, little information exists concerning the effects of long‐term fungicide programs on thatch accumulation. The influence of 14 fungicides, one nematicide, and of five mixed fungicide programs, applied over a 3‐year period, on thatch decomposition and the resultant pH of underlying soil was investigated on a blended Kentucky bluegrass (Poa pratensis L.) sod. The physical depth of noncompressed thatch was measured after samples were removed from plots with a Noer Soil Profile Sampler. Cores of 2.54 cm diam were used to determine pH characteristics of the soil profile. Thatch depths among fungicide treatments ranged from 2.8 to 22.0 mm, and the pH (saturated paste in 10 mM CaCl2) of the surface 3 cm ranged from 5.6 to 6.5. Thatch depth and pH of the surface 3 cm of thatch plus soil were inversely related (r = −0.797; significant at p = 0.001), although differences in pH among treatments were associated with the mineral soil fraction and not with the thatch. Fungicide‐induced reductions in pH occurred to depths exceeding 20 cm. Acidification of soil was apparently not the result of organic acids leaching from decomposing thatch, but was correlated (r = −0.564; significant at p = 0.01) with the contributions of sulfur (up to 491 g S/are/year) from the fungicides. Oxidation of sulfur from decomposing fungicides reduced the soil pH which, in turn, reduced the activity of microorganisms responsible for degradation of thatch. Thatch accumulation was not considered to be due to inhibitory effects of fungicides toward earthworms.
N Deprivation in Maize During Grain‐Filling. II. Remobilization of 15N and 35S and the Relationship between N and S Accumulation1
Authors: Friedrich J. W. , Schrader L. E.
Published: July 2010

The role of N and S remobilization in ear development of maize (Zea mays L.) has not been adequately assessed. The objective of this greenhouse experiment was to determine the effect of N deprivation during grain‐filling on N and S remobilization and the relationship between N and S accumulation. Maize plants were grown in nutrient solution containing 15N‐nitrate and 35S‐sulfate. After silking, the plants were placed in unlabelled solutions, with or without nitrate‐N. The amount of labelled and unlabelled N and S in several plant fractions was determined at silking and 1, 2, 3, 5, and 7 weeks after silking. The remobilization of labelled N and S was not markedly affected by N deprivation. Unlabelled N (when supplied) and unlabelled S accumulated in all plant fractions, but did not affect the concentration of N or S in the ear. Nitrogen deprivation resulted in only a 19% decrease in ear N content. Labelled N constituted 100% of the total ear N in plants deprived of N as compared to 84% for control plants. Labelled S comprised 73% of the total ear S in N‐derived plants as compared to 56% in plants supplied with N. The ratio of reduced N to reduced S (NR/SR) in the ear was lower in N‐deprived plants. The NR/SR, ratio in the leaves was not affected by N deprivation, and declined during grain‐filling. Apparently, the remobilization of N and S contributes more to ear development than does the absorption of N and S after silking.
Harvest Index of Soybeans as Affected by Planting Date and Maturity Rating1
Authors: Johnson D. R. , Major D. J.
Published: July 2010

Selection for high harvest index has been used by plant breeders to improve the seed yield of several crop plants, but in soybean [Glycine max (L.) Merrill] errors in the estimate of harvest index may occur because of interactions with maturity or seeding date and because harvest index measured at maturity does not include leaf and petiole dry weights. The objective of this study was to examine harvest indices of 10 soybean genotypes representing a wide range of maturity and seeded on several dates and to compare estimates of harvest index calculated from biological yield measurements with and without leaf and petiole dry weights.

Vegetative yield at the time of leaf senescence and seed yield at maturity were measured in 10 cultivars of soybean (two from each of maturity groups I–V) planted in a silt loam soil (fine, montmorillonitic, mesic Udollic Ochraqualfs) at five dates from late April through early July. Biological yield was defined as total above ground plant yield and harvest index was calculated as the ratio of seed yield to biological yield. A positive relationship was detected between biological and seed yield, presumably because of a strong photoperiod response. As biological yield increased, seed yield increased proportionally and harvest index stayed the same. Premature killing by frost decreased the harvest index. Variability for harvest index among cultivars within the same maturity group was indicated, but this was influenced by planting date and maturity group. It was concluded that selection for increased harvest index in soybean would have to be done within cultivars representing a narrow range of maturity and planted at the same time.
Germinability of Tobacco Seed as Affected by Culture of the Mother Plant1
Authors: Thomas Judith F. , Raper C. David
Published: July 2010

Uniformity of plant growth, which is important for efficient mechanization, is influenced by uniformity of seed germination. Since germinability characteristics of tobacco (Nicoticznu tabacum L.) seed produced in a phytotron are affected by the environment during develop ment of the mother plant, a field experiment was conducted to determine if measurable changes in germinability of seed result from alterations in cultural practices during mother‐plant growth. Cultural variables were N‐applied at 50, 72, and 94 kg ha−1 and normal or no leaf harvest. The increases in N applied to the mother plant reduced the time and enhanced the uniformity of seed germination. Leaf harvest had no effect on germinability characteristics. These effects were not significantly correlated with seed size.
Manure and Iron Effects on Sorghum Growth on Iron‐Deficient Soil1
Authors: Thomas J. D. , Mathers A. C.
Published: July 2010

Iron deficiency in sorghum [Sorghum bicolor (L.) Moench] occurs in spots throughout the High Plains on calcareous soils. This greenhouse experiment was conducted to determine the effect of N, P, and K with and without Fe and the effect of manure with and without additional Fe on Fe‐deficiency and dry matter yield of sorghum. Residual effects on a second and third crop also were measured. Pelleted manure and NPK (300‐100‐100 ppm) with Fe treatments were mixed with 3 kg of Arch fine sandy loam (Ustochreptic Calciorthid of the fine‐loamy, mixed thermic family). The treatments were Check, NPK, 0.5, 1.2, and 4% manure with Fe added to supply 0, 5, 10, 20, and 40 ppm Fe to the soil. Soil moisture was increased to 20% by weight periodically to maintain adequate soil moisture. Dry matter yield and observations indicated that manure effectively reduced Fe chlorosis and increased sorghum growth on Fe‐deficient calcareous soil. Either ferrous sulfate alone at rates up to 40 ppm Fe or fertilizer without Fe did not increase yields. Although yields were increased by adding Fe with fertilizer increases from Fe were not as great as those from manure. Manure had a residual effect on yield in the second and third crops. This indicates that manure can be used to correct Fe deficiency of grain sorghum on calcareous soils.
Soybean Top and Root Response to Temporary Water Tables Imposed at Three Different Stages of Growth1
Authors: Stanley C. D. , Kaspar T. C. , Taylor H. M.
Published: July 2010

Knowledge of the response that a crop's root system exhibits with respect to changing soil environments can be useful if that change can be altered by man. Such is the case with crops grown on soil where temporary high fluctuation of the water table can occur. Knowing at what growth stages a crop may be more tolerant or susceptible to injury could be valuable in determining to what depth and at what rates drainage should occur.

A field‐situated rhizotron study was conducted using two water table heights (45 and 90 cm) to determine the effects of temporary high water tables imposed at different growth periods on the development of the tops and roots of soybean [Glycine max (L.) Merr.] plants. Water‐table heights were established for 7 days during preflowering, postflowering (before podset), and post‐podset growth periods. Top and root growth parameters were monitored continuously throughout the growing season.

Results indicated that root tolerance to water‐table level changed as the plant progressed through its growth cycle. Root tolerance is described as the ability of the root system to withstand or adjust to the conditions caused by imposed water tables. During preflowering individual root tolerance was exhibited. Little damage occurred to the roots during imposition or removal of the water table treatments. During postflowering less individual root tolerance, but strong total root system adjustment was evident. Extensive damage to the roots occurred once the water tables were imposed, but the plant's ability to adjust to the situation by initiating new roots in soil areas above the water table levels was quite strong at this particular growth period. No root tolerance of the water‐table conditions was observed for post‐podset growth.
Drought Adaptation of Cowpea. IV. Influence of Drought on Water Use, and Relations with Growth and Seed Yield1
Authors: Turk Kenneth J. , Hall Anthony E.
Published: July 2010

In concurrent studies it was demonstrated that the drought resistance of cowpeas [Vigna unguiculata (L.) Walp.] is associated with extreme drought avoidance resulting from drought‐induced regulation of water loss. The present studies were conducted to quantify drought effects on crop water use, and relations with growth and seed yield.

Two cowpea cultivars were subjected to different drought intensities at the vegetative, flowering, and pod filling stages in the field during 2 years having contrasting weather patterns. Soil moisture was measured weekly throughout the season using the neutron scattering method. Water use (ET) and its ratio with pan evaporation (ET/Epan) were calculated both weekly and for the entire season.

The seasonal patterns of ET/Epan were similar for the 2 years which had contrasting patterns of potential evaporation. Under well‐watered conditions, ET/Epan increased linearly with ground cover and had an average value of 0.94 with complete ground cover. ET was restricted well below the potential level by different levels of drought, and at different growth stages, but showed rapid recovery following a vegetative‐stage drought.

When plant cover was not limiting, ET/Epan was extremely sensitive to percent available water in the rooting zone with a high threshold of 90% in contrast to results from earlier work with other crops. A more general description of the factors influencing ET of cowpeas under varying types and levels of drought was provided by a linear relationship between ET/Epan and fractional, ground cover × available water.

Root growth increased linearly throughout the season to a depth of 135 cm under well‐watered conditions, but was restricted greatly under dry conditions.

A linear relationship was observed between relative seed yield and relative water use from early flowering to harvest. Water‐use efficiency (WUE) generally increased with vegetative‐stage drought and was reduced by flowering‐stage and late‐season droughts. WUE increased slightly with moderate reductions in the level of weekly irrigation and decreased with further reductions in irrigation level.
Seasonal Nitrogen Accumulation and Fixation by Soybeans Grown at Different Densities1
Authors: Nelson A. N. , Weaver R. W.
Published: July 2010

abstract

Intra‐row spacing is expected to affect N accumulation and fixation because of the gross morphological changes that occur for plants grown at different densities. Enhancement of N fixation may lead to increases in soil N for nonleguminous crops and increase efficiency of soybean [Glydne max (L.) Merr.] production. Nodulating and non‐nodulating isolines of Lee cultivar soybeans were grown in a field experiment on Ships clay (very fine, mixed thermic, Udertic Haplustolls) at densities of 48,500, 97,000 and 194,000 plants ha−1 to determine the effect of plant density on seasonal patterns of N fixation and N distribution within plant tops. The distance between rows was 70 cm. The tops of the nodulating isoline plants were separated into leaflets, stems plus petioles, and pods. The rate of acetylene reduction and nodule mass was determined on the roots. Root density determinations were made using mini‐rhizotrons. The rate of dry matter accumulation per hectare and distribution of N within the plants was not greatly affected by planting density. No significant differences in root densities were found between isolines or among plant densities. The highest planting density of the nodulating isoline accumulated more than 300 kgNha−1 but total plant N in the non‐nodulating isoline was approximately 75 kgNha−1. During the first 17 days of the pod filling period, N accumulation in the pod sink was greatest and averaged approximately 7.5 kgNha−1 day−1 without a net loss of N from the leaflets. This indicates that N fixation can meet the N needs of soybeans without mobilization of leaf N.
Chemical Composition of Winter Wheat Forage Grown Where Grass Tetany and Bloat Occur1
Authors: Stewart B. A. , Grunes D. L. , Mathers A. C. , Horn F. P.
Published: July 2010

Winter wheat (Triticum aestivum L.) is widely used in the southern High Plains as a forage for beef cattle. Although grazing wheat is generally financially profitable, death losses often occur. Frothy bloat and grass tetany are often mentioned as causes, but the conditions under which these metabolic disorders occur are not completely understood. The objectives of the present study were: (1) to determine the changes in chemical composition of wheat forage during the normal wheat grazing season; (2) to determine the effect of N fertilizer on the chemical composition of the forage; and (3) to gain insight into the factors predisposing cattle grazed on wheat pasture to tetanic or bloat‐related death. Wheat pastures at Bushland, Texas, and El Reno, Oklahoma, were studied for 3 years by taking forage samples almost weekly during the growing seasons. Samples were analyzed for N, K, Ca, Mg, P, ash alkalinity, aconitate, and total nonstructural carbohydrates. Significant changes in forage composition occurred within very short periods. For example, in 1978 at El Reno, the K concentration increased from 2 to 4.5% in 2 weeks. During the same period, large changes occurred in the N, aconitate, ash alkalinity, and total nonstructural carbohydrate concentrations; but Mg concentrations did not change significantly. Nitrogen fertilization clearly affected chemical composition of the forage and generally increased the indices that are commonly associated with high incidence of frothy bloat and grass tetany. Elimination of fertilizer N is not practical because of the resulting pronounced decrease in forage and grain production. Therefore, other management practices are required to minimize or prevent frothy bloat and grass tetany problems on winter wheat forage.
Remote Sensing of Canopy Temperature at Incomplete Cover1
Authors: Heilman J. L. , Heilman W. E. , Moore D. G.
Published: July 2010

A field study was conducted in a barley (Hordeum vulgare L.) canopy to assess the potential for extracting canopy temperature information from nadir radiometric measurements at incomplete cover. Composite temperatures consisting of emitted and reflected longwave radiation from the barley and the soil background were measured by a nadir‐viewing infrared radiometer. Canopy temperatures were measured by an infrared radiometer at a 30° angle from the horizontal. Soil temperatures were measured with thermocouples.

Composite temperatures were 0.5 to 11.5 C higher than canopy temperatures with the largest difference occurring at low canopy cover. The correlation between composite and canopy temperature for data acquired throughout the growing season was not significant. A model which considered emitted radiation from both the canopy and the soil background, and which included reflected longwave sky irradiance was used to predict crop temperatures from nadir measurements. Predicted temperatures agreed with observed values (r2 = 0.88), and the prediction accuracy was independent of canopy cover. When emissivity corrections were not applied, prediction accuracy varied with percent cover with largest errors occurring at low cover. Prediction accuracy also varied with canopy cover when appropriate emissivities were used but sky irradiance was ignored. Results indicate that canopy temperatures can be estimated from nadir measurements at incomplete cover if percent cover, soil temperature, soil and canopy emissivities, and sky irradiance are known.
Cabbage Plant Responses to Nitrogen Fertilization1
Authors: Peck N. H.
Published: July 2010

Nitrogen fertilization may affect the yield components and quality attributes of vegetables grown for processing. The objective of this study was to determine the effects of N fertilization systems on cabbage (Brassica oleracea L. Capitata group) grown for kraut. The concentrations and contents of nitrate‐N and total N in the plants were used to determine the availability of N and uptake of N from the soil and/or fertilizer N during the growing season.

Urea broadcast at 15 g N/m2 and worked into the soil preplant was compared to ammonium nitrate applied at a rate of 15 g N/m2 split into three 5 g N/m2 applications (banded at planting time plus sidedressed early plus sidedressed midseason) as fertilization systems for cabbage grown under field conditions in 1978 and 1979. The soil was a Lima silt loam (Glossoboric Hapludalf, fine loamy, mixed mesic), a productive soil derived from calcareous glacial till. Plants were spaced 4/m2.

Tops of four plants grown without fertilizer N contained 12 g N/m2 at harvest. Fertilizer N applied at 15 g N/m2 increased the total N in the plant tops to 22 g N/m2. This was an increase in plant N equivalent to two‐thirds of the rate of fertilizer N applied.

Cabbage plants grown without fertilizer N yielded 4 kg fresh weight/m2. Fertilizer N at 15 g N/m2, either as urea or ammonium nitrate, yielded 8 kg of heads/m2. Fertilizer N at 30 g/m2 from urea plus ammonium nitrate yielded 10 kg heads/m2. Plants grown with fertilizer N had a lower percentage of dry weight in the heads, and had higher percentages of burst heads and heads with tipburn than heads of plants grown without fertilizer N. Thus, fertilizer N increased the yield but decreased the quality of cabbage heads grown for kraut.
Effect of Selenium and Cadmium Additions to Soil on Their Concentrations in Lettuce and Wheat1
Authors: Cary Earle E.
Published: July 2010

It has been reported that increasing selenium (Se) Concentration in nutrient solution decreased cadmium (Cd) concentration in plants grown in these solutions. In a greenhouse study, Se and Cd were added to Lima (Glossoboric Hapludalf, pH 7.3) and Mardin (Fragiochrept, pH 4.7) silt loam soils to investigate if a Se × Cd interaction could be used to lower Cd concentrations in plants grown on these soils. In a 3 × 3 factorial design, three replications of the following treatment were prepared 0, 2, and 4 µg Se/g soil added as Na2SeO3 and 0, 2, and 8 µg Cd/g soil added as CdCl2. The treatments were pipetted onto 100 g of soil. The soil was dried to a slightly moist state, aggregates were crushed, and the 100 g portion was blended into 2.9 kg of untreated soil for 15 min using a twinshell blender. All treatments received a blanket application of 58 µg/g soil each of N, P, and K. Additional N, P, and K was added before each new crop was planted. Lettuce (Lactuca sativa); ‘Black Seeded Simpson’, was grown on the lima soil before and after wheat (Triticum sp.), ‘Sheridad’. Only wheat was grown on the Mardin soil. After germination each crop was thinned to 3 plants/pot. In all crops, the concentration of an element added to the soil was correlated (P<l%) with that same element's concentration in the plant. In the first crop of lettuce, increased additions of Cd to soil reduced Se concentration in the plant from 1.3 to 0.8 µg Se/g and from 2.7 to 1.6 µg Se/g for the 2 and 4 µg Se/g soil treatments, respectively. Increasing soil Cd levels did not affect the Se concentration in the second lettuce crop. Selenium treatment did not affect Cd concentrations of lettuce in the first crop, but did reduce Cd concentrations in leaves of the second crop from 24 to 13 µg Cd/g and from 66 to 48 µg Cd/g for the 2 and 8 µg Cd/g soil treatments, respectively. The Se × Cd interaction was significant in both crops. In wheat, Cd reduced the concentration of Se in grain produced on the Lima soil 27% for the low‐Se and 227, for the high‐Se treatments, and in grain produced on the Mardin soil 33% for the low‐Se and 27% for the high‐Se treatments. Cadmium had little effect on the concentration of Se in the leaf and stem of the wheat, and Se had little effect on the Cd concentration in the aerial portion of wheat.
Effects of Seeding Date and Population on Water‐Use Efficiency and Safflower Yield1
Authors: Alessi J. , Power J. F. , Zimmerman D. C.
Published: July 2010

Oilseed crop production has increased greatly in the Northern Plains in recent years. Cultural practices to optimize oilseed production were studied for 4 years (1974–1977) to obtain information on safflower (Curthamus tinctoris L.) seed yield, oil concentration, and wateruse efficiency as affected by seeding date and plant population. Safflower was seeded on previously cropped or fallow land on three dates: early (16 May), midseason (6 June), or late (25 June) on Temvik silt loam (Typic Huploborolls). Soil water depletion by safflower was generally confined to the upper 150‐cm soil depth. Average water use by safflower seeded in mid‐May was greater by 4 and 8 cm than that used by the midseason and late seeding, respectively, and was unaffected by population. Significant positive correlations (r = 0.78) were obtained between oil concentration and degree days for the period after flowering. Correlation coefficients showed that 79% of the total variation in oil concentration was accounted for by variation in water use and temperature. Average water‐use efficiency for mid‐May, early June, and late June seeding was 34, 33, and 15 kg seed/cm water used, respectively. Seed and oil yields were highest for early and lowest for late seeding. In all years, seeding date affected seed yield and oil concentration. Population affected seed and oil yield in 1976. The results showed that safflower grown under dryland conditions in the Northern Plains should be seeded not later than mid‐May. Previous research in North Dakota showed that for best results safflower should be planted between 20 April and 10 May.
Harvested Dry Matter from Single and Double‐Cropping Systems1
Authors: Helsel Zane R. , Wedin W. F.
Published: July 2010

Double‐cropping (DC) has been advocated in the United States for increasing feed and food production and production efficiency. We studied single‐cropping (SC) and DC systems to determine the most productive crops or crop combinations for harvestable dry matter. Ten crops grown from 1974 to 1976 at Ames in central Iowa were: corn for silage, corn for grain, tropical corn (all Zea mays L.), grain sorghum, forage sorghum, sorghum × Sudangrass (all Sorghum bicolor Moench), pearl millet (Pennisetum americanum (L.) K. Schum), sugarbeets (Beta vulgaris L.), soybeans [Glycine max (L.) Men.], and sunflowers (Helianthus annas L.). These crops were planted alone at recommended times in a SC system and as main (second) crops in DC systems following first crops of winter rye (Secale cereale L.) and spring oats (Avena saliva L.) harvested for forage.

Dry matter (DM) yields of oats were greater than for rye. Rye, however, had the advantage of providing soil cover during the winter and being harvested earlier in the spring, thus permitting earlier planting of the main crop.

Average DM yields of main crops were greater in the SC system than in the DC system, where the main crop DM yields declined with the later dates of planting. Seme crops (sorghum Average DM yields of main crops were greater in the SC system than in the DC system, where the main crop DM yields declined with the later dates of planting. Some crops (sorghum × sudangrass hybrid, forage sorghum, pearl millet, sunflowers, soybeans) produced comparable yields in the rye‐DC and SC systems. Grain yields of grain crops and root yields of sugarbeets declined at a greater rate with later plantings than did whole‐crop yields. Corn for grain and corn for silage in the SC system and forage sorghum and sorghum × sudangrass hybrid in both the SC and rye‐DC systems produced the highest whole‐crop yields. Total DM yields were greater for the early‐harvested oat‐DC system in 1974 and the rye‐DC system in 1975 and 1976 than for other systems. We concluded that there is potential for increased harvestable dry matter by DC in the north central United States, particularly if a small grain harvested early for forage is the first crop of the DC system.
Response of Upland Rice to Phosphorus Fertilization on an Oxisol of Central Brazil1
Authors: Fageria N. K. , Filho M. P. Barbosa , Carvalho J. R. P.
Published: July 2010

Soils of the Cerrado region of Brazil are deficient in available P in their native state and require fertilizer P for optimum crop yield. But information on optimum rates of P application is lacking for upland rice production. Therefore, a 2‐year study was conducted to evaluate the response of rice (Oryza sativa L. cv. IAC 47) to different levels of P in a dark red latosol. The P treatments were 0,22,44, and 66 kg P/ha (0, 50, 100, and 150 kg P2O5/ha). Grain yield, dry matter production, tillers, leaf area index (LAI), and nutrient (N, P, K) accumulation in aerial plant parts were determined at different stages of growth.

In the 1st year (1977–1978), grain yield increased significantly up to 66 kg P/ha application; in the 2nd year (1978–1979), significant differences in yield were only obtained by application of 44 kg P/ha. Under the existing soil fertility levels upland rice needed 44 to 66 kg P/ha for its optimum P nutrition. With application of these levels of P, yield between 4,451 and 4,811 kg/ha was obtained. Dry matter production, LAI, and number of tillers per unit area were increased with the use of higher levels of P. The maximum number of tillers/m2 was reached between 60 to 70 days of growth and then started to decline. The uptake of N, P, and K increased with higher levels of P and age of the plant.
Cultivar Differences in N Redistribution in Soybeans1
Authors: Zeiher Carolyn , Egli D. B. , Leggett J. E. , Reicosky D. A.
Published: July 2010

The redistribution of N from vegetative plant parts to the developing seed in soybeans [Glycine max (L.) Merrill] may influence the duration of seed filling and yield. The objective of this study was to investigate the N redistribution characteristics of soybean cultivars of varying maturities and growth habit. Eight cultivars ranging from Maturity Group II to V and including indeterminate, determinate, and semi‐dwarf growth habits were grown in the field in 1977 and 1978 at Lexington, Ky. using conventional cultural practices. The soil type was a Lanton silt loam (Cumulic Haplaquolls) in 1977 and an Eagam silt loam (Cumulic Hapludolls) in 1978. Nitrogen redistribution was estimated by harvesting plants at beginning seed growth (R5) and at maturity. The abscised leaf blades and petioles were also collected and the dry weight and total N was measured in all plant parts. The vegetative dry weight at RS increased in cultivars of later maturity. There were no consistent culvar differences in N concentration at R5. The proportion of seed N that came from redistribution varied from 30 to essentially 100% and there were significant cultivar differences. The cultivar differences were positively correlated with the amount of N in the plant at R5 which was determined primarily by the vegetative dry weight at R5. Late maturing cultivars got more of their seed N from redistribution than early maturing cultivars. Although there were significant cultivar differences in yield and the duration of seed fill, they were not related to the amount of seed N that came from redistribution. Nitrogen redistribution does not appear to be an important factor determining the duration of seed filling or yield in soybeans.
Effects of Plant and Row Spacing on Dryland Soybean Yield and Water‐Use Efficiency1
Authors: Alessi J , Power J. F.
Published: July 2010

Data on effects of plant and row spacing on yield of soybeans [Glycine max (L.) Merr.] have given conflicting results. Most such experiments were conducted under conditions of little or no water stress. The experiments reported here, conducted under more severe stress conditions, broaden the water‐availability spectrum covered. Each spring, 1976 through 1979, soybeans were seeded on Temvik silt loam (fine‐silty, mixed Typic Haploborolls) at Mandan, N.D., in row widths of 15, 45, and 90 cm, and at within‐row spacings of 11, 15, and 23 cm, which resulted in plant populations of 48,000 to 580,000 plants/ha.

Soil water depletion by soybeans was generally confined to the upper 90‐cm soil depth. Average (4‐year) water use was 23.6 cm, and was not significantly affected by plant spacing. In 2 of the 4 years, total water use was greatest and average soybean yields were least Prom the 15‐cm row width. Within‐row spacing affected yields in only 1 of the 4 years.

Water‐use efficiency was least for 15‐cm rows in 3 of the 4 years. These data suggest that planting in 15‐cm rows enhances water use prior to flowering. In extreme drought situations, this enhanced earlyseason water use leaves less water available for pod‐fill, and seed yields may be reduced accordingly. Under less severe water stress, however, plant and row spacing has no affect on soybean yield.
Production and Quality of Four Bermudagrasses as Influenced by Rainfall Patterns1
Authors: Griffin J. L. , Watson V. H.
Published: July 2010

Bermudagrass (Cynodon dactylon L. Pers.) is the major warmseason perennial forage crop used for beef production in the Southeast. Seedhead production is irregular and consequently cannot be used as an index of age or quality. Chronological age is, therefore, important in making management decisions. Since bermudagrass production and quality may vary with season and year, ‘Coastal’, ‘Alicia’, ‘Callie’, and common bermudagrass harvested at 2‐, 4‐, 6‐, and 8‐week intervals were evaluated over 2 years in northeast Mississippi on a Leeper fine sandy loam (fine, montmorillonitic, nonacid, thermic Vertic Haplaquept) soil.

During the 1975 growing season rainfall was generally adequate and total dry matter yields of Coastal, Alicia, and common bermudagrass harvested at the four intervals were similar. Forage yields of Callie, however, averaged 20% higher than the other grasses because of higher production during July and August. In 1976, rainfall was especially low during August (2.0 cm) and total yield of the hybrid bermudagrasses were similar averaging 72% higher than that of common. Lower total season yields of common were reflected in less regrowth during July and August. Averaged over the grasses, total forage yields harvested at 4‐, 6‐, and 8‐ week intervals were 2.6 metric tons/ha lower in 1976 than in 1975 and were related in general to higher early‐season (June to July) forage yields in 1975 and limited regrowth in August and September 1976.

Crude protein (CP) was higher for Callie and common both years of the study. Neutral detergent fiber (NDF) and acid detergent fiber (ADF) varied little among grasses or harvest intervals. The increase in CP (3.4 units) and decrease in NDF (3.8 units) observed in 1976 appeared related to rainfall patterns, variation in regrowth potential among the grasses, and possible changes in the proportion of leafstem fractions. Averaged over years, Callie was higher in CP (11.9 vs. 10.3%) and digestible dry matter (55.3 vs. 53.0%), and lower in lignin (5.2 vs. 5.7%) than the other grasses.

Results suggest that selection of hybrid bermudagrasses over common should be based mainly on their potential to produce significantly more dry matter when moisture is limiting.
Yield and Development of Winter Wheat at Elevated Temperatures1
Authors: Johnson R. C. , Kanemasu E. T.
Published: July 2010

The influence of temperature on wheat (Triticum aestivum L.) yield components is known to differ depending on plant growth stage. Our objective was to determine how increased temperatures at five growth stages influenced development, yield, and yield components of winter wheat. Field experiments were conducted on the semi‐dwarf cultivar Newton grown in Eudora silt loam (coarse‐silty, mixed, mesic Fluventic Hapludolls). Transparent plexiglass chambers occupying 1.1 m2 of crop surface were heated continuously an average of 3.4 and 6.4°C above ambient temperatures during double ridge, terminal spikelet, stem extension, anthesis, and milky ripe developmental stages. Because the rate of development depends primarily on temperature, the treatments were expressed as accumulated thermal units (TU = Σ max °C + min °C/2) above ambient TU during each growth stage; where TU is thermal units, and max °C and min °C are maximum and minimum daily temperatures, respectively. At harvest, plot yields were determined and yield components estimated. Compared with controls, kernel weights were significantly increased by temperature treatments of 48 TU at double ridge in 1978‐1979 (P ≤ 0.05) and 44 TU in 1979‐1980 (P ≤ 0.10). High temperature treatments at terminal spikelet in 1978‐1979 reduced kernels per head (P ≤ 0.5) from 19.1 to 15.4, at least partly by reducing grain‐bearing spikelets per head. An increase in kernel weight was associated with that reduction in kernels per head so final yield was not significantly reduced. An average reduction of 2.4 kernels per head by the 101 TU treatment at anthesis significantly reduced yield in 1979‐1980. At milky ripe, average kernel weights were generally reduced by high temperatures both years. Increasing temperatures at any of the five growth stages advanced plant development relative to control plants. Using data from both years, kernel weights correlated positively with days (r = 0.83) and accumulated TU (r = 0.84) during grain filling. Development appeared to increase exponentially when daily TU was above about 27. Advancing anthesis a few days, when subsequent temperatures are less likely to be high, may benefit kernels per head and/or average kernel weight.