bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen Distribution, Yield, and Quality of Silage Corn after Foliar Nitrogen Fertilization
Authors: Ippersiel D. , Alli I. , MacKenzie A. F. , Mehuys G. R.
Published: July 2010

Forage corn (Zea mays L.) is an important crop because of its high energy content; however, an improvement in the protein quality of forage corn would be desirable. In some instances foliar N fertilization has resulted in improved yield of corn. The objective of the study was to determine the effects of foliar applied N on yields and on forage protein quality. Foliar urea spray (20 kg urea N ha−1) was applied to DeKalb W‐844 corn at two growth stages: 10% silking and 4 wk after the 10% silking stage. The field experiment was carried out on a Ste‐Rosalie clay (very fine silty, mixed, non‐acid, mesic) and an Ormstown silty clay (fine silty, mixed, non‐acid,mesic), both Typic Humaquepts, in the 1984 and 1985 growing seasons. Applied urea Was not detectable on the leaf surface of the plants by the third day following spraying. A transitory increase in the urea‐N and nonprotein N contents was observed 1 d after the spray. By the third day following the spray, there was no difference in the urea‐N and nonprotein N contents of sprayed and non‐sprayed plants. The effects of the foliar sprays on whole‐plant yield, grain yield, and protein quality of corn silage were not consistent. In general, the second spray resulted in increased protein yields. The results suggest that, although the foliar‐applied urea was absorbed by the corn plants in all cases, its effect on yields and protein quality of the corn silage was variable.
Sprinkler Irrigation Effects on Determinate Soybean Yield and Lodging on a Clay Soil
Authors: Boquet D. J.
Published: July 2010

Drought stress can reduce the yield of soybean [Glycine max (L.) Merr.] grown in the middle and lower Mississippi River Valley. A 3‐yr field study on Sharkey clay (very‐fine, montmorillonitic, nonacid, thermic Vertic Haplaquept) determined the effects of four soil water levels and two row spacings on the growth and yield of cultivars Forrest (MG V), Centennial (MG VI), and Braxton (MG VII). Irrigation was applied in the four treatments when (i) soil water matrix potential (Ψs) at both the 15 and 30 cm depths reached −70 J kg−1 (I1), (ii) Ψs at all depths between 15 and 76 cm reached −70 J kg−1 (I2), (iii) the same as in I1, but only after the R1‐R2 growth stage, and (iv) there was no irrigation (NI). Soybean was planted at interrow spacings (RS) of 0.5 and 1.0 m. Irrigation significantly increased yield of each cultivar at each RS in each year, but there were no yield differences among I1, I2, and I3 regimes at either RS. Average NI yields were 2.86,3.20 and 2.97 Mg ha−1 in 1982, 1983, and 1984, respectively. Yield increase from irrigation was 10,8, and 16% in 1982, 1983, and 1984, respectively. Irrigated yields of Forrest, Centennial, and Braxton were 3.47, 3.17, and 3.40 Mg ha−1, respectively, but water use efficiency was greatest with Forrest. Irrigation prior to R2 increased lodging up to 100%, and up to 50% when irrigated after R2. Severe lodging may have reduced irrigated yields. Relative yield increase from irrigation was limited by adequate rainfall and soil water storage, which resulted in high NI yields. The most efficient water regime was one based on an early maturing cultivar and γs measured at a depth of 76 cm.
Plant Tissue Degradation Measurement Using Image Analysis
Authors: Twidwell E. K. , Johnson K. D. , Bracker C. E. , Patterson J. A. , Cherney J. H.
Published: July 2010

Several microscopic techniques have been used to measure plant tissue degradation by rumen microorganisms. Our objective was to develop a less subjective method for measuring plant tissue degradation using computer‐based image analysis rather than visual appraisal. Three millimeter segments of leaf blades from ‘Cave‐In‐Rock’ switchgrass (Panicum virgatum L.) were placed either directly into a fixative or into buffered rumen fluid for 48 h. Segments were retrieved and prepared for light microscopy by fixation, dehydration, embedding, trimming, and sectioning at a thickness of 2 μ. Tissues in cross section were measured with an optical image analysis system and each tissue type was classified as undigested, partially digested, or completely digested. The relative proportion of tissue types in undigested samples ranged from 1.9 ± 0.20% for phloem tissue to 35.9 ± 1.26% for mesophyll tissue. Standard deviations of measurements from digested samples ranged from 1.1 to 12.2%. Degradation of xylem and phloem was difficult to measure and had the highest standard deviations of 9.8 and 12.2%, respectively. This method requires approximately 15 min per sample, and although it is more time consuming than visual estimation methods, it has the advantage of measuring extent of digestion on an area basis more objectively than other methods currently used.
Differential Response of Two Cotton Cultivars to Fertilizer and Soil Potassium
Authors: Cassman K. G. , Kerby T. A. , Roberts B. A. , Bryant D. C. , Brouder S. M.
Published: July 2010

Cotton (Gossypium hirsutum L.) cultivars have considerable yield differences on vermiculitic soils where late‐season K deficiency occurs in California. A 2‐yr field study was conducted to evaluate cultivar differences in K use efficiency (defined as higher yield with a limited K supply) in relation to K uptake, K partitioning, and critical internal and external K requirements. The experiment had a split plot design with fertilizer‐K addition levels as mainplots, two cultivar subplots, and 10 blocked replications. Without K addition, yield was 29% (1986) and 35% (1987) greater in the K‐use‐efficient cultivar. Cultivar yield differences reflected greater boll retention at later fruiting positions, but was not related to differences in partitioning of K between vegetative and fruiting structures. When K supply was not limited, cultivar yields were similar. Yield of both cultivars was closely associated with leaf K concentration and soil K availability, but response curves indicated a lower leaf and soil K requirement for the K‐use‐efficient cultivar. The K‐use‐efficient cultivar had a higher K uptake rate during fruit development and greater total K accumulation, particularly at low soil K levels. Defining the physiological bases for such large genetic variation in K use efficiency will help to identify why the cotton plant is more sensitive to K limitation than other crops and will aid breeding efforts to develop germplasm more tolerant of a limited soil K supply.
Seasonal Variation in Chemical Composition of Forage Brassicas. I. Mineral Concentrations and Uptake
Authors: Guillard K. , Allinson D. W.
Published: July 2010

Little information is available on the mineral composition of summer‐ and autumn‐grown Brassica forages and the ability of these crops to provide the mineral requirements of grazing ruminants. This paper reports on seasonal variation of mineral composition and uptake in summer‐ and autumn‐grown turnip (B. rapa L.), rape (B. napus L.), swede (B. napus L.), and Tyfon [B. rapa L. ✕ B. pekinensis (Lour.) Rupr.]. Species were no‐till seeded into glyphosate [N‐(phosphonomethyl)grycine]‐suppressed sod in Connecticut on a Paxton fine sandy loam soil (coarse‐loamy, mixed, mesic Typic Dystrochrept) in 1983 and 1984. Concentrations of Ca, Mg, K, Cu, Fe, Mn, and Zn in summer‐grown species were similar to or exceeded concentrations in autumn‐grown species. Species grown during autumn, however, had greater concentrations of N and P. Foliage concentrations of Ca, Mg, N, and Mn were noticeably greater than root concentrations of the same minerals. Total mineral uptake in summer‐grown species was significantly greater for Ca, Mg, K, Cu, Fe, and Mn relative to uptake of these minerals in autumn‐grown species. Although species or seasonal effects, or species ✕ season interaction effects were significant for particular minerals, concentrations of Ca, Mg, P, K, N, and Fe were adequate or well above recommended levels for ruminants. Micromineral supplementation, however, may be needed for ruminants consuming Brassica grown on soils with low micromineral availabilities. Because of high mineral uptake, depletion of soil fertility would be rapid if native fertility is low and limited fertilizer is applied to these crops.
Thermal Time Requirements for Phenological Development of Peanut
Authors: Ketring D. L. , Wheless T. G.
Published: July 2010

Temperature is a major environmental factor that determines the rate of plant development. Relation of thermal time to phenological development of peanut would provide a better understanding of this crop's response to temperature. Thermal time measured in day‐degrees (°Cd) was used to determine peanut (Arachis hypogaea L.) phenological development of a Spanish botanical‐type culitvar, Pronto, and a Virginia botanical‐type breeding line, OK‐FH15. Peanuts were grown under field conditions, on a Teller sandy loam (fineloamy, mixed, thermic, Udic Argiustoll) in 1985, 1986, and 1987. Irrigation plus rainfall ranged from 840 mm in 1985 to 400 mm in 1987. At 12 d after planting (DAP) when >80% emergence had occurred, 136 ± 18 °Cd had accumulated. Pronto produced more mainstem nodes (vegetative stage) than did OK‐FH15. Regression analyses indicated that both vegetative and reproductive development were highly correlated with °Cd for both genotypes. Incipient flowering (R1) began at 313 and 360 °Cd in 1985 and 1986, respectively. At 50% R1 in 1987, 410 and 498 °Cd had accumulated for Pronto and OK‐FH15, respectively. Both vegetative and reproductive stage development were slower with less water. Although attainment of a high reproductive stage value (7 to 9) does not indicate a high yield per se, it does indicate the degree of crop maturity. Seasonal accumulation of °Cd in 1985, 1986, and 1987 was 1456,1672, and 1473, respectively. Crop yields (pods) for the fullirrigation treatment were 312, 325, and 288 g m−2 for Pronto and 358, 405, and 308 g m−2 for OK‐FH15 in 1985, 1986, and 1987, respectively. Knowledge of °Cd accumulated can provide an estimate of harvest date as well as crop development stage.
Hybrid Cotton Pollination in Relation to Accumulated Degree Days
Authors: Phillips Sherman A. , Simpson James L.
Published: July 2010

Hybrid cotton (Gossypium spp.) pollination needs to be supplemented with honey bee (Apis mellifera L.) colonies. However, the relative importance of this supplemental pollination at specified time intervals during cotton bloom has not been determined. Therefore, our study was conducted to determine the quantity and quality of hybrid seed produced as a result of pollination during four consecutive, equal degree‐day (DD) periods. Four hybrid cotton seed production fields were established in Lubbock County, Texas. Accumulated DD (base temperature = 15 °C) were recorded for each field and divided into four equal periods within fields. Native and honey bee visitation was monitored every 2 d by counting the numbers observed per 100 flowers on the A‐line. All cotton bolls were hand harvested and sorted by date of bloom. Following harvesting, ginning, and delinting, seeds were counted and weighed, and percent germination was determined. Although the native and honey bee visitation level was adequate throughout each DD period, linear regression analyses indicate that coefficients of determination (r2) were low for (i) percent boll set and number of bees (native and honey bees), and (ii) number of seeds per boll and mean number of bees (native and honey bees). Pollination during the earlier DD periods resulted in higher percent germination, larger number of seeds per boll, and higher seed weight than seeds resulting from pollination during the latter bloom periods. We conclude that with proper honey bee management and pollination timing, the quality of hybrid seed produced will be improved by using only that from the first half of the bloom period
Weed Population Dynamics and Weed Control in the Peruvian Amazon
Authors: Mt. Pleasant Jane , McCollum R. E. , Coble H. D.
Published: July 2010

In traditional slush‐and‐burn agriculture, forest fallow is a primary agent in weed control. Stable continuous‐cropping systems could be expected to require a comprehensive program of weed management, probably including the use of herbicides. Weed control measures in a sequence of rice (Oryza sativa L.)‐corn (Zea mays L.)‐soybean (Glycine max L.)‐rice‐corn‐soybean were studied for 2 yr in Yurimaguas, Peru, with the following objectives to: (i) identify weed species resistant to the herbicide program in a continuous cropping system, and (ii) develop effective weed management practices for intensively managed cropping systems in the humid tropics. First‐crop weeds were 60% grass, 25% sedges, and 15% broadleaf weeds. The grass was composed of two species: large crabgrass [Digitaria sanguinalis (L.) Scop.] and goosegrass (Eleusine indica (L.) Gaertn]. Sixth‐crop weed population was 80% grass, 13% broadleafs and 7% spreading dayflower (Commelina diffusa Burm. f.); and itchgrass (Rottboelia exaltata L.f.) comprised 85% of the grasses. Metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐l‐methylethyl) acetamide] controlled crabgrass, goosegrass, and most broadleafs in corn and soybean; but it did not control itchgrass. Metolachlor alone resulted in a weed population that was 97% itchgrass in the sixth crop. Sethoxydim {2‐[(1‐ethoxyimino)butyl]‐5‐[2‐(ethylthio)propyl]‐3‐hydroxy‐2‐cyclohexen‐1‐one}‐plus bentazon [3‐(1‐methylethyl)‐(1.H)‐2,1,3‐benzothiadiazin‐4(3H)‐one 2.2‐dioxide] on soybean controlled grasses including itchgrass, but broadleaf weeds and dayflower increased. Propanil [N‐(3,4‐dichlorophenyl) propanamide]‐plus‐oxadiazon {3‐[2,4‐dichloro‐5‐(1‐methylethoxy)phenyl]‐5‐(1,1‐dimethyl)‐1,3,4‐oxadiazol‐2‐(3H)‐one} on rice resulted in a mixed grass population. Rice was more vulnerable to weed pressure than either corn or soybean and appears inappropriate for this high‐input rotation because of the high cost of weed control.
Influence of Sample Dividing Method on Forage Quality as Determined by Nirs
Authors: Hall M. H.
Published: July 2010

Forage samples collected in the field are normally dried, coarsely ground, and subdivided to minimize time and expense required for secondary grinding, facilitate ease of sample handling, and reduce space needed for sample storage. The objective of this research was to determine the efficacy of four sample dividing methods to produce uniform subsamples for near infrared reflectance spectroscopy (NIRS) analysis. Sample dividing methods were: (1) quarter sectioning with a straight edge, (2) use of a gravimetric dividing apparatus, (3) mixing in a blender then dividing by quarter sectioning, and (4) mixing in a blender and dividing with a gravimetric dividing apparatus. Dividing method efficacy was evaluated by comparison of subsample quality. Average coefficients of correlation (r) between subsamples obtained using the divider apparatus were 0.97 and 0.08 for crude protein (CP) and acid detergent fiber (ADF), respectively. These r values were 4 and 6% higher for CP and ADF, respectively, than those obtained using the quarter sectioning method. However, r of the quarter sectioning method averaged for both CP and ADF improved nearly 7% by mixing the sample before dividing. The gravimetric dividing apparatus was superior to the quarter sectioning method in uniformly dividing both mixed and unmixed forage samples.
Temperature and Mepiquat Chloride Effects on Cotton Canopy Architecture
Authors: Reddy V. R. , Baker D. N. , Hodges H. F.
Published: July 2010

Cotton, (Gossypium hirsutum L.) when grown in a fertile, well‐watered, and suitable environment, produces excessive vegetative growth. Such luxuriant growth causes several production problems. A plant growth regulator, mepiquat chloride1 (1,1‐dimethylpiperidinium chloride; BASF Wyandotte Corp., Parsippany, NJ) has been found to reduce vegetative growth, but the crop responses to it appears to be temperature sensitive. An experiment was conducted to determine the crop responses to temperature in naturally lighted, temperature‐ and CO2‐controlled plant growth chambers. The experiment was conducted at five temperatures and measurements were made of several plant parameters. A preliminary experiment showed that mepiquat chloride (MC) caused a dramatic reduction in plant height and number of main‐stem nodes. A more detailed study showed that the impact of MC on main‐stem elongation was temperature dependent, with the greatest effect occurring at 35/25 °C day/night temperatures. The application of MC also caused a reduction in mainstem, vegetative‐branch and fruiting‐branch node formation. Leaf area was reduced on plants treated with MC at each of the temperatures. Specific leaf area (m2 kg−1) was also reduced on leaves from various positions on the plants. It appears that MC affects more than one physiological process. The primary effects were reduction in stem elongation, node formation, and leaf expansion. The reduced stem growth and leaf area development also caused greater leaf densities—probably a secondary or tertiary effect.
In Vivo Cotton Stem and Petiole Nitrate Reductase Activity
Authors: Chu Chang‐chi , Bariola Louis A.
Published: July 2010

Cotton (Gossypium hirsutum L.) plant stems and petioles are not generally considered to be major sites of nitrate reductase activity (NRA). Field studies were conducted to determine the significance of stem NRA and the potential of petiole NRA as an indicator of the N status of cotton. The contribution of various cotton plant parts to the in vivo plant shoot NRA (with endogenous nitrate only) was evaluated at five stages of plant development from the seedling stage to the flower bud stage (reproductive stages). In 1987 and 1988, samples were taken between 1000 and 1200 h under a clear sky from various plant parts of cotton (cultivar Deltapine 61) grown in a calcareous Holtville silty clay in the Imperial Valley, CA. Results showed that the plant stem (or hypocotyl) plus petiole contribution to the total plant shoot NRA increased from 14 to 72% as the plant progressed from vegetative growth to reproductive growth. Results indicated that cotton plants stems were high in NRA relative to leaf blades, except at the seedling stage. Samples taken from 35 cultivars and breeding lines in the same year under the same environmental conditions showed that the petiole NRA was high at the early flower bud stage. The petiole's average contribution of 52% of the total NRA of the top mature leaf indicates that petiole NRA may be useful as an indicator of N metabolism at the early flower bud stage of development.
Root Temperature and Calcium Level Effects on Winter Wheat Forage: II. Nutrient Composition and Tetany Potential
Authors: Miyasaka S. C. , Grunes D. L.
Published: July 2010

Wheat pasture poisoning is a metabolic deficiency of Ca, and sometimes Mg, in ruminants. It occurs particularly in the spring, when K and N concentrations in the shoots, and the equivalent ratio of K/(Ca+Mg) in the forages, increase suddenly. To determine the effects of an increased root temperature and four Ca levels on the forage quality of winter wheat (Triticum aestivum L. ‘Centurk’), seedlings were grown under three root temperature regimes (constant 8 °C, constant 16 °C, and increasing from 8–16 °C), in nutrient solutions with four Ca levels (0.2, 0.6, 2.0, and 5.0 mM). Plants grown at 8 °C root temperature had significantly lower Ca, Mg, K, and N concentrations in the shoots, and a significantly lower equivalent ratio of K/(Ca + Mg), compared to those grown at 16 °C. Plants transferred from 8 to 16 °C had significantly increased Ca, Mg, K, and N concentrations in the shoots over time, as levels changed from those characteristic of low root temperature plants to those characteristic of high root temperature plants. Plants transferred from 8 to 16 °C also had an equivalent ratio of K/(Ca + Mg) that increased 1 wk after the transfer, indicating a greater tetany hazard. The doubling in forage K and N concentrations, and the increase in the equivalent ratio of K/(Ca+Mg) as root temperatures increased from 8 to 16 °C, are similar to those found in field‐grown plants at the time of tetany for grazing beef cattle. Thus, root temperature could be a key environmental factor involved in tetany, modifying the nutritional quality of winter wheat.
Phosphorus Management for Continuous Corn‐Cowpea Production in a Brazilian Amazon Oxisol
Authors: Smyth T. J. , Cravo M. S.
Published: July 2010

Although Oxisols occupy extensive areas in the Amazon, few studies have addressed their fertilizer P requirements for sustained, long‐term crop production. This field study was conducted to evaluate initial and long‐term responses to P rates and placement by corn (Zea mays L.) and cowpea (Vigna Unguiculata L.) when grown in annual rotation during five consecutive years in a Xanthic Hapludox (clayey, kaolinitic, isohyperthermic) near Manaus, Brazil. Effects on yields of sole broadcast P rates of 0, 22, 44, 88 and 176 kg ha−1 in split‐plot combination with subplot banded P rates of 0, 11, 22 and 44 kg ha−1 were evaluated over 11 total crops. Banded P at 11 kg ha−1 was applied to every crop and rates of 22 and 44 kg P ha−1 were only applied to the initial eight and four crops, respectively. Residual effect of broadcast P, as measured by both yields and Mehlich 1 soil P, were greater at high rates. Although cowpea yields were increased up to the highest band rate, no response in corn yields were observed beyond the rate of 22 kg P ha−1. At equal amounts of applied P, banded P provided greater yields than broadcast P during the initial crops. Total corn and/or cowpea yields, after 11 crops, were similar for all broadcast and band combinations at equal amounts of total applied P. The absence of a cumulative yield difference among placement methods indicated that banded placement of 22 and 44 kg P ha−1 to corn and cowpea, respectively, would be the best method of applying P to sustain long‐term crop production under the manual tillage practices used in the region.
Soil Aluminum Effects on the Growth and Aluminum Concentration of Sorghum
Authors: Shuman L. M. , Ramseur E. L. , Duncan R. R.
Published: July 2010

Aluminum toxicity, especially in the subsoil, is a major limiting factor in crop production on acid soils. A greenhouse experiment with sorghum [Sorghum bicolor (L.) Moench)] was conducted on topsoils and subsoils of four widely different acid southeastern soils [Congaree (Typic Udifluvent), Pacolet (Typic Hapludult), Norfolk (Typic Paleudult), Pelham (Arenic Paleaquult)] to determine relationships between plant growth and levels of Al and other major cations in the soil. Plants were grown for 6 wk after which plant height, weight, and root weight were recorded. Plant tissue was analyzed for Al, Mn, Ca, K, and P concentrations. Soils were analyzed for pH, 1 M KCl‐exchangeable Al, Al saturation of the CEC, and 0.01 M CaCl2‐extractable Al. Major soil solution ions were also determined and the activity of Al species was calculated using GEOCHEM. Reductions in plant growth were ascribed to Al toxicity and not to Mn toxicity or Ca deficiency. In general the correlations between plant growth and soil Al levels were significant for topsoils [r = −0.53* to −0.91** (P = 0.05 and 0.01, respectively)] but nonsignificant for subsoils. Topsoil data and subsoil data were markedly different; subsoil Al values were low compared to those for topsoil (exchangeable Al 49 vs. 58 mg kg−1), but the plants grew better in topsoils (51 vs. 29 cm). The best predictors of plant height and plant Al were soil solution Al3+ activity (r = −0.91**, 0.83**) and Al saturation of the exchange complex (r = −0.89**, 0.82**), but CaCl2,‐extractable Al was also correlated well (r = −0.78**, 0.94**).
Turf Growth and Performance Evaluation Based on Turf Biomass and Tiller Density
Authors: Lush W. M.
Published: July 2010

Visual rating systems are often used for evaluating turfs because of the absence of biological criteria associated with growth and performance. The purpose of this paper is to examine whether describing turfs quantitatively in terms of their biomass and tiller density can contribute to our understanding of turf growth, and form the basis of an objective, quantitative system of turf assessment. Measurements of the aboveground biomass, and the corresponding tiller densities of turfs, were gathered mostly from published work. The data indicate that turfs, like many crowded populations of plants, are governed by a rule of population biology called the power, or thinning, rule. As applied to turfs, conformity to the power rule means that biomass is highest at the lowest tiller densities, with the consequence that very hard‐wearing turfs may inevitably be coarse textured. Estimates of the upper limits to biomass at tiller densities commonly found in turfs of different texture, suggest that there is more potential for the improvement of coarse turfs than fine ones. For turf assessment, biomass (alone or divided by tiller density to estimate mean tiller mass), is a useful guide to wear resistance. A measure of the fineness of turf texture is proposed. The use of biomass density (biomass divided by turf height) as a predictor of golf ball roll and lie is discussed. When turfs are at full cover, one of the parameters of the power rule, the biomass intercept log c, which can be derived from single measurements of biomass and tiller density, is proposed as a measure of the ability of turfs to accumulate biomass. Log c has the advantage of being independent of tiller density and of differences in nonlimiting management resources
Kernel Abortion and Distribution of Mineral Elements Along the Maize Ear
Authors: Mozafar A.
Published: July 2010

Kernel abortion, especially prevalent at apical ear positions, results in malformed (nubbin) ears and substantial yield reduction in maize (Zea mays L.). Although deficiencies of N, P, K, Mn, Zn, and B are reported to cause nubbin ears, it is not known whether the concentrations of these or other elements are different in the aborted and normal (fully developed) kernels. In this study, the concentrations of 12 mineral elements in the kernel and cob tissue from apical, middle, and basal positions in normal and nubbin maize ears having aborted kernels at their tips were compared. The concentrations of N, P, K, Mg, Ca, Na, B, Zn, Cu, and Mn in the kernels and P, Na, Ca, Fe, B, Zn, Cu, Mn, and Mo in the cobs were the same in nubbin and normal ears. Kernel concentration of Mo and cob concentrations of N, K, and Mg were significantly higher in nubbin than in normal ears. In the normal ears, concentrations of K and Zn in the kernels and N, P, K, and Zn in the cobs were higher in apical than in basal ear positions. In nubbin ears, concentrations of N and Zn were higher in apical (aborted) than in basal (normal) kernels. In cobs of nubbin ears, however, concentrations of N, P, K, Mg, Ca, Zn, and Mn were higher in apical positions adjacent to aborted kernels as compared with basal positions adjacent to fully developed normal kernels. Since the concentration of no element was lower in the nubbin ear than in the normal ear, an insufficient supply of the tested mineral elements was ruled out as a cause of kernel abortion. From this study, it is not certain whether accumulation of elements in the apical portion of the cob precedes or follows kernel abortion. A malfunction in the transport of mineral elements and carbohydrates from the leaves to the kernels via phloem or a disturbance in the transfer of mineral elements between cob and kernel tissues at their junction may be concomitant with (but not necessarily the cause of) kernel abortion.
No‐Till Proso Millet Production
Authors: Anderson R. L.
Published: July 2010

Proso millet (Panicum miliaceum L.) is well‐adapted for the Central Great Plains and is commonly grown with a mechanical tillage production system in a winter wheat (Triticum aestivum L.)‐milletfallow rotation. The use of tillage results in extensive wind and water erosion, however. Research was conducted on a mesic Aridic Paleustoll soil near Akron, CO, to determine proso millet response to a no‐till production system. Eliminating tillage increased proso millet grain yields from 2290 to 2730 kg/ha in 1985 and from 1200 to 1610 kg/ha in 1986, compared to tilled proso millet production. Water use efficiency (WUE) also increased in the no‐till system. Nitrogen fertilizer at 22 or 44 kg N/ha increased grain yield, N concentration of grain, and WUE of no‐till proso millet regardless of whether growing‐season precipitation was near normal or 33% below the long‐term site average of 212 mm. Atrazine [6‐chloro‐N‐ethyl‐N'‐(1‐methylethyl)‐l,3,5‐triazine‐2,4‐diamine] applied either in the previous fall or 60 d before planting provided effective in‐crop weed control for the no‐till production system. Atrazine applied in the spring required two paraquat (1,1'‐dimethyl‐4,4'‐bipyridinium ion) applications at 0.28 kg ai/ha to control weeds the previous fall. Nitrogen fertilizer did not affect the bioactivity or soil persistence of atrazine.
Nitrogen Fertilizer Recovery by Corn in Monoculture and Rotation Systems
Authors: Varvel G. E. , Peterson Todd Andrews
Published: July 2010

Crop rotations including legumes have increased in importance because of their potential to reduce large inorganic N fertilizer needs for corn [Zea mays L.] and other crops. This study was conducted to determine N fertilizer recovery by corn in monoculture and rotational systems. Corn was grown under rainfed conditions on a Sharpsburg silty clay loam (fine, montmorillinitic, mesic, Typic Argiudoll) in four cropping systems: (i) continuous corn monoculture, (ii) a 2‐yr soybean [Glycine max (L.) Merr.]‐corn rotation, (iii) a 4‐yr rotation of oat [Avena sativa (L.)] + clover [80% Melilotus officinalis (L.) and 20% Trifolium pratense]‐grain sorghum [Sorghum bicolor (L.)]‐soybean‐corn, and (iv) a 4‐yr rotation of soybean‐grain sorghum‐oat + clover‐corn at Mead, NE. Broadcast applications of 15N‐depleted NH4NO3 were made at 90 and 180 kg N ha−1 in 1985 and 1986 to evaluate N fertilizer recovery by corn in each cropping system using isotopic methods. Nitrogen recovery determined by isotopic methods was significantly higher for corn in rotation vs. corn in monoculture, averaging 58.6 vs. 52.3% and 49.8 vs. 43.4% at the 90 and 180 kg N ha−1 rates, respectively. In contrast, fertilizer N recovery estimated by the difference method was much greater in continuous corn vs. N recovery in corn following oat + clover in the 4‐yr rotation. These differences indicated that N fertilizer applied to corn in each cropping system appeared to be entering different sizes and types of organic soil N pools, resulting in apparent differences in N immobilization. Our results demonstrate problems exist in estimating fertilizer N recovery with both methods (isotope or difference) and before accurate N recovery estimates by corn or any other crop can be made in complex soil and crop management systems, procedures must be developed to explicitly follow N fertilizer pathways (immobilization, denitrification, volatilization, leaching, etc.). Until that time, correct interpretations with either method can be obtained within a system if all available information is used regarding both soil and crop factors.
Sustaining Soil Nitrogen for Corn Using Hairy Vetch Cover Crop
Authors: Utomo M. , Frye W. W. , Blevins R. L.
Published: July 2010

Nitrogen fertility management is often complicated by inadequate supply, low efficiency, high losses, and the potential of polluting water resources. This study was conducted in 1984 and 1985 on a Maury soil (fine, mixed, mesic Typic Paleudalfs) in Kentucky to determine the role of a hairy vetch (Vicia villosa Roth) cover crop in sustaining soil N for corn (Zea mays L.) under no‐tillage and conventional tillage. Winter cover treatments of hairy vetch, rye (Secale cereal L.), and corn residue were combined factorially with N rates of 0, 85, and 170 kg ha−1 in the two tillage systems. Total soil C and N in the 0‐ to 7.5‐cm depth, averaged across treatments and sampling dates, were 21.8 and 2.07 g kg−1, respectively, in no‐tillage and 16.6 and 1.70 g kg−1 in conventional tillage. Values were 19.8 and 1.99 g kg−1, respectively, with hairy vetch and 18.8 and 1.80 g kg−1 with rye. Conventional tillage caused rapid mineralization of soil N, as indicated by greater inorganic N approximately 6 wk after plowing. Nitrate apparently leached deeper into the soil under no‐tillage than conventional tillage. Grain yield without N on the vetch treatment was essentially equal to yields with 170 kg N ha−1 on the rye or corn residue treatments—6.75, 6.75, and 6.65 Mg ha−1, respectively. Grain yield with vetch and 170 kg N ha−1 was 7.85 Mg ha−1. Although vetch provided a substantial amount of N, results suggested that to obtain optimum corn yields N fertilization should be reduced little, if any, with a vetch cover crop. Vetch appeared to add grain yield instead of reduce the need for N fertilizer.
Soybean Growth Responses and Intraspecific Competition from Simulated Seedcorn Maggot Injury
Authors: Higley Leon G. , Pedigo Larry P.
Published: July 2010

The consequences of early‐season insect injury on subsequent plant development often are obscure. Further, such injury may produce intraspecific competition between injured and uninjured plants. We examined these issues by studying the impact of simulated seedcorn maggot (SCM) [Delia platura (Meigen) (Diptera: Anthomyiidae)], injury to soybean [Glycine max (L.) Merr.], in field studies from 1983 to 1986 in Iowa. Simulated SCM injury includes plant density (simulating stand reductions) and normal to Y‐plant ratios (simulating various proportions of plumule injury). The Y‐plants are plants that have had the plumule destroyed and subsequently develop two main stems. Our objectives were to describe how simulated SCM injury affected: (i) development of soybean stands, individual normal plants, and individual Y‐plants, and (ii) intraspecific competition between normal and Y‐plants. Higher crop growth rates (CGRs) and leaf area indices (LAIs) were associated with higher plant densities. Generally, plumule‐injured plants were more affected by plant density than uninjured plants. Examinations of competition between uninjured and plumule‐injured plants indicated that uninjured plants were competitively superior to plumule‐injured plants. Competitive interactions were influenced by plant density, Phenological delay associated with plumule injury contributed to height differences between uninjured and injured plants, which led to substantial differences in leaf area, number of nodes, and other developmental parameters between injured and uninjured plants. Consequently, unequal competitive ability between uninjured and injured plants was identified as a major consequence of plumule injury.
Overview of Long‐Term Agronomic Research
Authors: Mitchell C. C. , Westerman R. L. , Brown J. R. , Peck T. R.
Published: July 2010

Renewed interest in low‐input and sustainable crop production has rekindled interest in long‐term agronomic research. Research plots that have been monitored continuously since the late 19th Century exist in several states. Twenty‐five experiments have been identified that have been monitored for over 25 yr; 12 of these are more than 50 yr old. Yield and treatment records provide valuable information on the effects of cropping systems, tillage, manuring, and fertilization practices on yields and on soil physical and chemical properties, Most of these very early tests were non‐replicated studies using large plots and crop rotation systems. Four of America's oldest, continuous agronomic research tests were reviewed in more detail: (i) Illinois' “Morrow Plots” (c. 1876), (ii) Missouri's “Sanborn Field” (c. 1888), (iii) Oklahoma's “Magruder Plots” (c. 1892) and (iv) Alabama's “Old Rotation” (c. 1896). All of these are listed on the National Register of Historical Places. These studies document that long‐term crop production can be sustained and improved in different regions and on different soils of the USA. Long‐term studies have shown that crop rotations and attention to recognized and established soil fertility practices, which may or may not include legumes and manuring, are essential to maintaining high, sustained production.
Noninvasive Measurement of Internal Oxygen Concentration of Field‐Grown Soybean Nodules
Authors: Denison R. F. , Smith D. L. , Legros T. , Layzell D. B.
Published: July 2010

Recent research suggests that decreased N2 fixation with drought, defoliation, or nitrate exposure is due to decreased nodule permeability to O2. Decreased O2 permeability would result in lower O2 concentration in the nodule interior and a decreased rate of bacteroid respiration in support of N2 fixation. To test this hypothesis under field conditions, a noninvasive method (based on spectrophotometry of leghemoglobin) was used to measure O2 concentration within intact, attached nodules of soybean [Glycine max (L.) Merr.]. A detopping (shoot removal) treatment, which interrupted phloem supply to nodules, resulted in lower internal O2 concentration relative to controls, suggesting that nodule respiration was directly limited by O2 rather than carbohydrate. When the gas stream around a nodule was switched from pure N2 to pure O2, internal O2 concentration increased more rapidly in control nodules than in nodules attached to detopped plants. This difference in reoxygenation rate is also consistent with reduced nodule gas permeability after detopping. The method described here, with modifications, should be useful for a variety of field studies.
Simulated Growing‐Season Precipitation and Nitrogen Effects on Winter Wheat Yield
Authors: Engel R. E.
Published: July 2010

Available water (precipitation plus stored soil water) is the principal factor that determines wheat (Triticum aestivum L.) yield patential and response to N in the Northern Great Plains. Field studies were conducted in 1987 and 1988 to determine the interactive effect of water and available N on ‘Redwin’ and ‘Centurk’ winter wheat yield. Seven fertilizer N levels and a line‐source sprinkler system created a wide range of N and simulated growing‐season precipitation (SGSP) regimes on a Yegen sandy loam (fine‐loamy, mixed, Typic Argiboroll). Wheat yield‐N‐SGSP functions revealed that yield and response to water were much greater in 1987 than 1988, when return from N was maximized (maximum economic yield or MEY). At 100, 200, and 300 mm SGSP, predicted MEY in 1987 averaged 2350,4019, and 5434 kg ha−1, respectively. In 1988, MEY was 9, 17, and 24% lower, respectively. High available N reduced yield from the maximum across all SGSP regimes in 1988, but not in 1987. High temperatures during grain fill in 1988 (23.1 °C, 4.7 °C: warmer than 1987), were likely the reason for differing yield‐NSGSP relations. Though Centurk yielded more than Redwin for most SGSP conditions, the N required for MEY or optimum N level. (ONL) was not greatly affected by cultivar. Due to less favorable growing conditions, the ONL was approximately 27% lower in 1988 than 1987. An acceptable fertilizer N strategy might be to raise the ONL level to 100 kg ha at 100 mm growing‐season precipitation, then adjust N upward 1 kg ha−1 for every 3 mm rise in available water.
Chloride Fertilizer Effects on Winter Wheat Inoculated with Fusarium culmorum
Authors: Engel R. E. , Grey W. E.
Published: July 2010

Studies in the Northern Great Plains indicate that Cl fertilizers sometimes increase yield and reduce the severity of root diseases in small grains. Little information exists from this region on the relationship between Cl and common root rot incited by Fusarium culmorum (W.C. Sm.) Sacc., or the effect of Cl on winter wheat (Trificum aestivum L.) yield. The objectives of this study were to address these issues. Field experiments were conducted in south central Montana during 1988 and 1989 on a Fort Collins soil (fine‐loamy, mixed, mesic Ustollic Haplargids) that contained 57 and 39) kg Cl ha−1 (0−120 cm), respectively. The experiment consisted or two cultivars of winter wheat (Redwin and Cree), three seed treatments (heat sterilized F. culmorum, live F. culmorum plus chemical protectant, and live F. culmorum, and four CI fertilizer levels (0, 22.5, 45, and 90 kg Cl ha−1) in complete factorial arrangement. In. spection of lower stems and subcrown internodes at the soft dough stage indicated no effect from Cl on disease severity. Chloride fertilizer significantly increased grain yield in 1988 (P < 0.001), but not in 1989. In 1988 grain yields at 22.5, 45, and 90 kg Cl ha−1 were not different and averaged 3306 kg ha−1, or 227 kg ha−1 more than plants not receiving Cl. Whole plant Cl concentrations at heading and indigenous soil Cl were not reliable predictors of yield response to C1 fertilizer. Seasonal factors may be important in defining the likelihood of a response to Cl fertilizer in addition to soil and plant Cl status.
Cottonseed Preparation for Hydraulic Planter
Authors: Bordovsky J. P. , Lyle W. M. , Onken A. B.
Published: July 2010

The operation of a newly developed mobile irrigator planting system required seed of upland cotton (Gossypium hirsutum L.) to be stored in an aqueous gel slurry for up to 24 h prior to planting. Prolonged anaerobic conditions in the slurry resulted in poor cottonseed germination. Tests were conducted to determine if H2O2 would react with small amounts of starch‐based material in the slurry mixture and produce sufficient O2 to maintain seed germination. A laboratory seed germination test was conducted with three seed treatment factors considered (i) seed soaking or priming vs. nonpriming prior to placement in the slurry; (ii) level of H2O2 in the water used to mix the slurry – 0.0, 0.02 and 0.04 M, and (iii) the level of starch‐based material in the dry gel concentrate – 0.0, 1.0 and 5.0%. Additional tests were conducted to determine if O2 was produced from H2O2 reacting to components of the seed/gel slurry other than the starch material. The level of starch‐based material had no effect on germination, 0.02 and 0.04 M H2O2 solutions significantly improved final cottonseed germination over treatments with no H2O2 and nonprimed seed had significantly higher final germination than the primed seed, Tests indicated the volume of O2 released by H2O2 reacting with cottonseed is far greater than that released by H2O2 reacting with the starch. Therefore, the starch material was not required in the slurry mixtures..
Improved Nitrogen Management in Irrigated Durum Wheat Using Stem Nitrate Analysis: I. Nitrate Uptake Dynamics
Authors: Knowles T.C. , Doerge T.A. , Ottman M.J.
Published: July 2010

Intensive N management for irrigated spring wheat (Triticum aestivum L.) grown in arid and semi‐arid regions requires preplant soil, plus periodic basal stem analyses for nitrate. Additional information on the relationships between grain yield and quality, N rates and stem nitrate‐N (NO3‐N) levels is needed for the wide range of agronomic conditions found in areas where irrigated durum wheat (Triticum turgidum L. var. durum) is grown. Five field experiments were conducted during the 1985 to 1988 crop years in southern Arizona to examine the effects of N rate, mobility of N fertilizer form, level of residual soil N, soil texture, and two contrasting wheat cultivars on basal stem NO3‐N concentrations and grain yield and quality of durum wheat. Stem NO3‐N concentrations were responsive to both fertilizer and soil‐N levels. Nitrogen applications containing mobile NO3‐N or urea‐N resulted in stem NO3‐N concentrations at the Feekes 2 growth stage (GS) that averaged 52% less (2.0 vs. 4.2 g NO3‐N kg−1) than when an equivalent amount of an immobile NH4‐N source was used on Casa Grande sandy loam [coarse, loamy, mixed (calcareous), hyperthermic, Typic Natrargid (reclaimed)] soil. Different N sources had no significant effect on stem NO3 levels for wheat grown on a Trix clay loam [fine loamy, mixed (calcareous), hyperthermic, Typic Torrifluvent] soil. Wheat grown on finer textured clay loam soils showed a two fold increase for NO3‐N accumulation in basal stem tissue due to N applications ranging from 225 to 651 kg N ha−1 over the sampling period from GS 6 through 10.5. No statistical or practical differences were observed in the quantities of NO3‐N contained in the stem tissue of two popular durum wheat cultivars (Aldura and Westbred‐881) when equivalent rates of N were applied. Visual deficiency symptoms were not observed, and subsequent grain yield and quality did not suffer when stem NO3‐N levels decreased to no lower than 1.0 g kg−1 following GS 6. These results provide important information needed to increase the precision and accuracy of the basal stem tissue NO3‐N test for predicting the N status of irrigated durum wheat.
Ionic Concentrations and Water Relations of Alfalfa Seedlings Differing in Salt Tolerance
Authors: McKimmie T. , Dobrenz A.K.
Published: July 2010

There is great variability within alfalfa (Medicago sativa L.) populations in response to salinity stress. This study was conducted to investigate the physiological basis of that variability. Growth performance and physiology were compared in two groups of a population of alfalfa seedlings that differ in vigor when grown under − 0.7 MPa salinity. The experiments were conducted in a greenhouse using a system designed to screen seedlings for salt tolerance. Plant height, internode length, leaf area, number of leaves, dry weight, ion concentration, percent water, and water potential were measured. Shoot parts of the more vigorous group contained lower concentrations of Na and Cl. Roots of the vigorous group contained higher Na concentrations. The vigorous group contained more total ions (Na + Cl + K) per plant but fewer total ions on a dry weight basis. Water potentials of both shoots and roots were greater in the vigorous seedling group; there were no differences in percent water.
Screening Sericea Lespedeza Germplasm for Herbage Quality
Authors: Petersen J. C. , Hill N. S. , Mosjidis J. A. , Windham W. R.
Published: July 2010

Sericea lespedeza [Lespedeza cuneata (Dumont) G. Don] is recognized as being a relatively poor quality forage because of high concentrations of tannins in its leaves. Therefore, an accurate assessment of tannins in the leaves is essential for the selection of low tannin lines. The objectives of our research were to investigate improved methods of tannin analysis for the screening of the lespedeza germplasm, and to determine the relationship between in vitro dry matter digestibility (IVDMD), crude protein (CP), and leaf tannins. Field experiments containing 81 lespedeza entries were established at two locations. Herbage samples were harvested twice during the growing season for 2 yr and the leaves analyzed for IVDMD, CP, and tannin concentration by near infrared reflectance spectroscopy (NIRS). Results of an HCI‐vanillin analysis of aqueous acetone extracts of fresh‐frozen samples (ACE‐FF) and oven‐dried samples (ACE‐OD), and methanolic extracts of oven‐dried samples (METOD) were used to derive the NIRS tannin equations. Standard errors of calibration (SEC) were lowest for the MET‐OD data and highest for the ACE‐FF data. However, coefficients of variation (CV) were inversely proportional to SEC. Coefficients of variation of field experiments were also lowest when samples were analyzed by the NIRS tannin equation derived from ACE‐FF data. Differences in tannin concentration, CP, and IVDMD existed among entries, locations, and seasons. Differences between locations and seasons were due to changes in moisture and temperature. Strong negative correlations were found for the ACE‐FF tannin data and IVDMD (r = −0.90 to −0.92), and ACE‐FF data and CP (r = −0.66 to −0.70) relationships. Our results indicate that the tannin analysis of ACE‐FF is a better reference method for NIRS calibration and subsequent screening of the lespedeza germplasm, and that the relationships between tannins, CP and IVDMD, suggest that a significant improvement in herbage quality may be achieved.