bluuebunny/crossref_metadata_2025 huggingface dataset:
Water Transfer through Cotton Plants Connecting Soil Regions of Differing Water Potential
Authors: Baker J. M. , van Bavel C. H. M.
Published: July 2010

Several studies have shown that water can move through plant root systems from wet to dry soil during periods of low evaporative demand. It has been suggested that such movement could be important in alternate furrow or drip irrigation systems, where water is applied in a discrete or nonuniform manner. This study was undertaken to examine this question, using a physical experiment and computer simulation. A growth chamber experiment was conducted with three rows of cotton (Gossypium hirsutum L.) plants. The outer row plants were grown over vertical barriers such that half of their root systems shared a volume of soil with the center row plants, while the other half was hydraulically isolated in separate soil compartments. The center compartment was allowed to dry, while the outer compartments were watered daily. Soil moisture was measured throughout all compartments twice daily by gamma densitometry. When the potential gradient between center and outer compartments reached 1.0 MPa, the gamma readings showed overnight movement of water from wet to dry soil that could only have taken place through the root systems of the outer row plants. The overnight transfer of water, while significant, was not sufficient to fully supply the daytime transpiration demand of the unirrigated center row plants. It was also less than that predicted by computer simulation, unless the latter reflected the inability of the xylem water potential of cotton plants to equilibrate with soil water potential during periods of low evaporative demand. Regardless, the results suggest that water transfer by root systems should not be excluded in simulations of water movement in the soil‐plant‐atmosphere system.
Nitrogen Fertilization of No‐Till Winter Wheat and Rye. I. Yield and Agronomic Responses
Authors: Fowler D. B. , Brydon J. , Baker R. J.
Published: July 2010

Winter wheat (Triticum aestivum L.) and rye (Secale cereale L.) can be grown successfully in most parts of western Canada if sown directly into standing stubble. However, soil N is usually limiting under this production system. Consequently, 40 field trials were conducted over a range of soil types and environmental conditions to determine yield and other agronomic responses of no‐till winter wheat and rye to N fertilizer applied in the spring. Each trial consisted of three to 12 replications with N rates of 0 to 303 kg ha−1. Nitrogen fertilizer had little effect on days to heading, days to maturity, test weight, and seed weight. Increased N resulted in height increases of up to 25 cm in wheat and 8 cm in rye in some trials, and decreases of up to 9 cm in both wheat and rye in other trials. Winter rye demonstrated a greater N use efficiency and yield potential than winter wheat. The relationships between grain yield (Y) and total available N were best described by modified inverse polynomials, Y = (1 − N/903) uN/(N + u/65.8) for wheat, and Y = (1 − N/800) uN/(N + u/88.5) for rye, where u represents the upper limit of yield when N is not limiting. These curves accounted for 99.3 and 98.7% of the observed variation in grain yield of wheat and rye, respectively. Maximum yields were related to moisture status during the growing season and were achieved at different rates of N fertilization.
Analysis of Trace Elements in Forages by Near Infrared Reflectance Spectroscopy
Authors: Clark D. H. , Cary E. E. , Mayland H. F.
Published: July 2010

Use of near infrared reflectance spectroscopy (NIRS) for elemental analysis has been limited to a few elements including Ca, P, K, and Mg. However, other elements are of interest in the agricultural industry. Therefore, NIRS spectra were collected on forage samples consisting of tall fescue (Festucu arundinacea Schreb.), crested wheatgrass (Agropyron cristatum and A. desertorum), and alfalfa (Medicago sativa L.). Elemental concentrations of Ba, Li, Mo, Ni, Pb, V, AI, S, and Si were determined by ICP (Inductively Coupled Argon Plasma) analysis while selenium (Se) was determined by fluorometry. The elemental analyses were regressed against NIRS apparent absorption from 1100 to 2500 nm at 2‐nm increments. Coefficients of variation [CV = (standard error of performance / the mean from the chemical procedure) ✕ 100] ranged from a high of 211% for Li in crested wheatgrass to 11% for S in alfalfa. Determination of Ba, Li, Mo, Ni, Pb, and V exhibited enough inconsistency in CVs among the three forages to preclude their determination with NIRS. Aluminum and S appear to be present in an organic form that NIRS is able to detect (CV = 22 and 15, 21 and 12, and 28 and 11%, for tall fescue, crested wheatgrass, and alfalfa, respectively). Silica exhibited slightly more variation than S or AI, with alfalfa having the highest CV (49%). Selenium was only determined on a tall fescue population with a CV = 27%. Using the statistical values as parameters indicative of NIRS utility, it appears that A1 and S are the only elements in this group of minerals that can be determined with NIRS for these forage types.
Carbon Dioxide Exchange During Mist Propagation of Jojoba Cuttings
Authors: Feldman William R. , Palzkill David A. , Dobrenz Albert K. , Hogan LeMoyne
Published: July 2010

Carbon dioxide exchange parameters of jojoba (Simmondsia chinensis (Link) Schneider) tip cuttings were studied to determine whether significant photosynthesis occurs prior to rooting, whether fertilization during the rooting process affects carbon dioxide exchange, and whether a non‐destructive method for monitoring progress of root development could be developed. Cuttings were collected from field‐grown plants and placed under intermittent mist in a double‐poly greenhouse. Osmocote (19‐2.6‐l0), a controlled release fertilizer, was incorporated at 0, 1.5, 3.0 and 5.9 kg m−3 into a 1:1 perlite:vermiculite medium at time of inserting cuttings. Photosynthesis and respiration of the cuttings were monitored periodically from the time of insertion until they had rooted and been potted‐up. Gas exchange was monitored at 28°C and at a light level of 700 µmol m−2 s−1. Root respiration was determined using a chamber designed to isolate the base of the cutting together with the medium and any developing roots from the leaves and stem. Significant differences in C02 flux and root growth (dry wt) were found over the 11 wk of the study. Photosynthetic rates during the first wk under mist were moderate (ca. 3 µmol C02 m−2 s−1), declined steadily from the beginning of the study until rooting, and then increased significantly. This suggests that treatments such as shading, which increase plant cutting survival prior to rooting, but which also reduce photosynthesis, could likely be used prior to root formation without negative effects on rooting. Dark respiration declined steadily from the beginning of the study until rooting and increased slightly thereafter. Root respiration paralleled photosynthesis. Photosynthesis at lining out was significantly correlated with root dry weight, root respiration, and leaf succulence. Root dry weight and root respiration were significantly correlated, implying that monitoring of root respiration could be used as a non‐destructive method of monitoring root growth. During the 11 wk of the study, no consistent differences among the fertilizer treatment groups were found in either C02 flux or in root growth (dry wt).
Nitrogen Partitioning in Cowpea as Influenced by Rhizobial Strain and Mineral Nitrogen
Authors: Luyindula N. , Weaver R. W.
Published: July 2010

Partitioning of nitrogen into the pods of legumes is an important yield determinant. The ability of cowpea [Vigna unguiculata (L.) Walp.] ‘Bush Purple Hull’ to partition N from dinitrogen fixation and assimilated nitrate into pods was measured with the aid of 15N. Cowpea was inoculated with four strains of Bradyrhizobium species and grown in a glasshouse to maturity. Two nitrate treatments were included; one provided an initial dose of starter N (40 mg plant−1) and the other provided split applications of N throughout the growth period (total of 240 mg plant−1). With starter N only, the results indicated that the strain of rhizobia did not influence partitioning of biologically fixed dinitrogen or nitrate N into pods. However when inoculated with either of two strains, cowpea partitioned approximately 63% of the total assimilated nitrate from the continuous N treatment into the pods, whereas another strain partitioned approximately 52% into pods. Of the total N from dinitrogen fixation, 53 and 58% was partitioned into the pods for the starter N and continuous N treatments respectively. The strains of rhizobia were similar in the quantity of nodule tissue formed on the roots, but the quantity of N contained in the nodule tissue varied from 40 to 20 mg N plant−1 for the starter N treatment. It appears that strains of rhizobia should be considered when undertaking experiments involving N partitioning.
Early Season Development of Floral Buds in Cotton
Authors: Ungar E. D. , Kletter E. , Genizi A.
Published: July 2010

Improving irrigation and pest control strategies in upland cotton (Gossypium hirsutum L.) requires a better understanding of the factors influencing the formation and retention of fruiting bodies. The objective of this study was to investigate the effect of irrigation regime, boll load, and fruiting position upon floral bud dynamics. Field experiments were conducted during 3 yr on a Gan Shmuel vertisol (clayey, montmorillonitic, calcareous, thermic Typic Chromoxerert). Treatments comprised four irrigation patterns, and one zero‐load (continuous flower removal) treatment. Dates of shedding, attainment of 1 cm size, and flowering were recorded by fruiting position for all buds on sympodia formed during the first 75 to 100 d after emergence. Of a total of 7972 buds observed, 51, 33 and 16% flowered, shed <1 cm size, and shed>l cm size, respectively. Shedding of buds <1 cm size was more sensitive to treatment than shedding of buds >1 cm size. The probability of bud formation at L2 and L3 was strongly affected by sympodium number (Ln represents the nth fruiting position on a sympodium). Flowering declined from 74% at L1 to 16% at L4. The zero‐load treatment achieved the highest flowering percentage (66%) and number of fruiting positions per sympodium. The lowest flowering percentage (42%) resulted from severe, and relatively late, water stress. Strong positive associations between the shedding of contemporary buds at different relative positions on the plant indicate that an important component of shedding is the response to common stress stimuli. Weaker negative associations between the fate of noncontemporary buds can be explained by the negative feedback of boll load on bud retention.
Birdsfoot Trefoil Management. II. Yield, Quality, and Stand Evaluation
Authors: Alison M. W. , Hoveland C. S.
Published: July 2010

Management recommendations for birdsfoot trefoil (Lotus corniculatus L.) are based mainly on research conducted in the northern USA. The relevance of this work to more southern‐adapted birdsfoot trefoil cultivars needs to be examined. These studies were conducted to determine the effect of stubble height and harvest interval on herbage yield and quality of northern‐ and southern‐selected birdsfoot trefoil cultivars when grown in the southern USA. Two field experiments were established on a Cecil sandy loam (clayey, kaolinitic, thermic Typic Hapludult) soil near Athens, GA. ‘Fergus’ and GA 1 birdsfoot trefoil entries were harvested every 21, 28, and 42 d to stubble heights of 5 and 10 cm. The birdsfoot trefoil entries ‘AU Dewey’, ‘Dawn’, Fergus, Ga 1, and ‘Norcen’ were harvested to 3, 5, and 10 cm every 21 d. Entries AU Dewey, GA 1, and Fergus were most productive, but herbage yields of all entries increased with length of time between harvests. Harvesting every 21 d at a 3‐cm stubble height generally reduced yields. After 2 yr, stands of AU Dewey, GA 1, Dawn, and Norcen were reduced 59, 45, 24, and 15%, respectively, while Fergus was unaffected. The AU Dewey and GA 1 entries should be allowed either a higher stubble or regrowth periods longer than 21 d because of erect growth habit. In vitro dry matter digestibility of all entries remained high (> 700 g kg−1) throughout the season and was not affected by harvest treatment. Results of these studies indicate that birdsfoot trefoil cultivars respond differently to harvest management.
Water‐Deficit Effects on Alfalfa at Various Growth Stages
Authors: Halim R. A. , Buxton D. R. , Hattendorf M. J. , Carlson R. E.
Published: July 2010

Studies of water‐deficit effects on forage quality of alfalfa (Medicago sativa L.) have generally considered water stress throughout plant growth. This experiment was conducted to compare, with an unstressed control, the effects of short‐term soil‐water deficits occurring at three growth stages. Plants were grown in 100‐L containers set into the ground and protected with an automatic rain‐out shelter. Control treatments were watered weekly or twice weekly to raise the soil‐water level to field capacity. Watering was excluded during the third or fourth week of regrowth for plants that were stressed at vegetative and bud stages, respectively. For plants stressed at the flower stage, watering was excluded during the sixth or seventh week. Plants were harvested at five weekly intervals beginning 21 d after an initial defoliation. Stress at the bud or flower stages reduced leaf‐to‐stem ratio (LSR) by 25 and 38% of control, respectively. Stress at the vegetative stage did not affect LSR. As a result of lower LSR, in vitro digestible dry matter (IVDDM) in plants stressed at the bud or flower stages was 4% less than that of the control. The IVDDM of herbage in plants stressed at the vegetative stage was not different from the control. Crude protein (CP) concentration in stems increased by up to 8% of the control when plants were stressed at the vegetative or bud stages. Concentration of CP in leaves of stressed plants was 5 to 11% less than that of the control. Herbage CP concentration was up to 12% less than that of the control with stress at the bud or flower stages. Cell wall (CW) concentration in stems and total herbage was generally lower in plants stressed at the vegetative and bud stages. After rewatering, forage quality recovered in plants stressed at the bud stage. Most of the decline in forage quality due to stress at the bud or flower stages was caused by reduction in LSR and deterioration of leaf quality.
Phenological Stage and Herbage Quality Relationships in Temperate Grasses and Legumes
Authors: Sanderson Matt A. , Wedin W. F.
Published: July 2010

Phenological indexes that account for variation in chemicál composition of herbage would be valuable to farmers and researchers. Hence, the objective of this study was to relate neutral detergent fiber (NDF) and in vitro digestible dry‐matter (IVDDM) concentrations in herbage and plant parts of alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), timothy (Phleum pratense L.), and smooth bromegrass (Bromus inermis Leyss.) to phenological development of each species. Four replicate plots of each species were harvested at four 2‐wk intervals during the spring of 2 yr. Alfalfa was separated into leaves (including flowers) and stems; red clover into leaflets (including flowers), petioles, and stems; and bromegrass and timothy into leaf blades and stems (including sheaths). Herbage from two plots of each species was scored for phenological stage according to a species‐specific index and a mean stage number (mean stage by weight, MSW) was calculated. For each plant part, NDF and IVDDM concentrations were regressed on MSW across years. Alfalfa leaves remained constant in NDF (206 g kg−1 dry matter, DM) and IVDDM (783 g kg−1 DM) with increasing MSW; however, MSW accounted for 97% of the variation in NDF and IVDDM concentrations of alfalfa stems and herbage. Herbage concentrations of NDF and IVDDM were more closely related to MSW than were concentrations of NDF and IVDDM in leaflets, stems, or petioles of red clover, and leaf blades and stems of bromegrass and timothy. Only in alfalfa did MSW adequately account for variation in NDF and IVDDM of herbage and plant parts. Phenological models for the other species adequately accounted for variation in some, but not all, plant parts.
Alfalfa Persistence and Yield with Irrigation
Authors: Rice J. S. , Quinsenberry V. L. , Nolan T. A.
Published: July 2010

Three field experiments were conducted to investigate the effects of irrigation on alfalfa (Medicago sativa L.) forage yield, distribution of yield, and stand persistence. Two of the studies were conducted near Clemson, SC on a Cecil sandy loam (clayey, kaolinitic, thermic, Typic Hapludults) with the third conducted at Blackville, SC on a Facevilie loamy sand (clayey, kaolinitic, thermic, Typic Paleudults). All irrigation was initiated when average soil‐water pressure reached ‐20 kPa at the 20‐ and 40‐cm depths as measured by tensiometers. The average forage yield response to irrigation across the studies in the Clemson (Piedmont) experiments was 2.6 Mg ha−1. The response varied from year to year and no irrigation ✕ cultivar interaction was detected. Stands deteriorated more rapidly with irrigation and seasonal distribution of forage production was only slightly improved. The average response to irrigation in the Blackville experiment (Coastal Plains) was also 2.6 Mg ha−1; however, the response in the second year was negative and the study was terminated because irrigated stands were depleted. An interaction with cultivar was detected in the second year as a result of negative irrigation responses for seven cultivars and a positive response for one cultivar. The positive response reflected the fact that only one cultivar had more than a 70% stand in August of the second season. Diseases did not appear to be severe enough to explain the losses. We conclude that irrigation of alfalfa in the Southeast is a marginal practice.
Ethephon and Nitrogen Use in Winter Wheat
Authors: Van Sanford D. A. , Grove J. H. , Grabau L. J. , MacKown C. T.
Published: July 2010

The plant growth regulator ethephon ([2‐chloroethyl] phosphoric acid) has often been used to reduce height and lodging of intensively managed soft red winter (SRW) wheat [Triticum aestivum (L.) em. Thell]. The effect of ethephon on traits that determine grain yield has not been widely studied. This study was conducted to determine whether ethephon alters N use and other yield‐related traits in SRW wheat. Nine SRW cultivars were evaluated for 2 yr near Lexington, KY on a Maury silt loam (fine, mixed, mesic Typic Paleudalf). Lodging was negligible in both years. Total plant N at anthesis was significantly increased in plots treated with ethephon at Feekes growth stage (GS) 6 (12%) or GS 9 (15%). Similarly, dry matter (DM) at anthesis was increased 9 and 11% when ethephon was applied at GS 6 and 9, respectively. However, neither total N nor DM at maturity was significantly altered by ethephon application. Remobilization of vegetative N was increased 13% in ethephontreated plots. Ethephon applied at either GS increased the relative importance of N uptake efficiency vs. N partitioning efficiency in determining cultivar variation in N use efficiency. Application of ethephon did not alter grain yield, harvest index, or N harvest index. Ethephon had little or no influence on rate and duration of kernel growth, and slightly decreased kernel size (4%) when applied at GS 6. We conclude that ethephon has a minimal effect on the yield‐determining traits evaluated in this study. However, the pronounced effect of ethephon on the nature of cultivar differences in N use efficiency warrants further study.
Dry Matter and Nutrient Accumulation and Partitioning by Proso Millet
Authors: Rodriguez J. B. , Westfall D. G. , Peterson G. A.
Published: July 2010

Information on dry matter accumulation and nutrient uptake pattern for proso millet (Panicum miliaceum L.) is very limited. Therefore, a project was initiated to measure dry matter accumulation and N, P, K, Ca, Mg, S, Fe, Mn, Zn, and Cu uptakes in whole plants, stalks, leaves and heads of proso millet during the growing season. The two cultivars, Cope and Dawn, were field grown on an Aridic Argiustoll that had optimum nutrient and water availability. Plant samples were collected at weekly intervals starting 30 d after planting, and continuing throughout the growing season. Nutrient concentrations, dry matter accumulation, and mineral uptakes were very similar for both varieties. Whole plant concentrations of most nutrients decreased from emergence to maturity, except for Ca, Mg, and Mn which increase with time. From anthesis to maturity, dry matter accumulated rapidly at a rate of 0.5 Mg/ha/d, tripling during this period. Heads at maturity accounted for 55% of the total plant dry matter, which is higher than for wheat (Triticum aestivum L.) or grain sorghum (Sorghum bicolor L.). Proso millet accumulated N and P during heading like grain sorghum, which is more efficient than corn (Zea mays L.). Dry matter accumulation and nutrient uptake patterns are illustrated during the life cycle of this plant.
Indirect Estimation of Botanical Composition of Alfalfa‐Smooth Bromegrass Mixtures
Authors: Moore K. J. , Roberts C. A. , Fritz J. O.
Published: July 2010

Botanical composition of grass‐legume mixtures greatly influences the productivity and quality of the sward and is therefore an important variable in many agronomic studies. Four indirect methods of estimating the botanical composition of mixed swards of alfalfa (Medicago sativa L.) and smooth bromegrass (Bromus inermis Leyss.) were evaluated to determine their relative efficacy. The methods were the constituent differential method using either neutral detergent fiber (NDF) concentration or crude protein (CP) concentration as variables, a modified constituent differential method where NDF and CP concentrations were used simultaneously as variables, and near infrared reflectance spectroscopy (NIRS). Mean deviations of predicted alfalfa percentages from known values were lowest for NIRS at all stages of maturity and averaged 1.5 percentage units. Of the constituent differential procedures, NDF was the most reliable variable for predicting alfalfa percentage over all maturities with deviations averaging 2.9 percentage units. Based upon the results of this study, NIRS would be the preferred method for estimating botanical composition of grass‐legume mixtures; however, in cases where NIRS is unavailable or inappropriate, the constituent differential method using NDF as a single variable would be an acceptable alternative.
Spring Wheat Response to Enhanced Ammonium Supply: I. Dry Matter and Nitrogen Content
Authors: Camberato J. J. , Bock B. R.
Published: July 2010

Spring wheat (Triticum aestivum L.) grain dry matter (DM) has been increased in previous greenhouse experiments through the use of a nitrification inhibitor (NI), which provides an enhanced ammonium supply (EAS). The objective of this research was to determine, under greenhouse conditions, the effect of EAS on the accumulation and partitioning of DM and N at several stages of plant development and on the yield components (heads plant−1, kernels head−1, and kernel weight). Enhanced NH4 supply increased plant DM at 18 d after plant emergence, boot stage, 7 d after anthesis, and maturity. Enhanced NH4 supply did not alter the relative partitioning of DM among leaf, stem, and grain at any stage of development. Effects of EAS on plant and grain DM at maturity increased with increasing N rate. At the highest N rates, grain DM was increased 18 and 6% in two experiments. Nitrogen and moisture stress appeared to alter grain DM response to EAS. Increased grain DM was associated with an increased number of heads plant−1. Kernels head−1 were decreased with EAS, but kernel weight was not affected. Consequently, EAS increased heads plant−1 more than grain DM. At growth stages prior to maturity, EAS increased plant N uptake. At maturity, plant N uptake was slightly and inconsistently affected by EAS; however, the proportion of plant N in the grain was increased by EAS. This indicated a greater translocation of N from the stem to the grain with EAS. In general, increased spring wheat grain DM is associated with proportional increases in plant DM throughout plant development, but not necessarily with proportional increases in plant N uptake. Heads plant−1 is the only yield component increased positively by EAS and thus warrants further research.
Legume Cover Crops as a Nitrogen Source for No‐Till Corn and Grain Sorghum
Authors: Blevins R. L. , Herbek J. H. , Frye W. W.
Published: July 2010

Increasing use of conservation tillage has brought about a renewed interest in growing winter legume cover crops. Field experiments were conducted to determine the fertilizer N equivalency of hairy vetch (Vicia villosa Roth), bigflower vetch (Vicia grandiflora W. Koch var. Kitailbeliana), and rye (Secale cereale L.) to no‐tillage corn (Zea mays L.) and grain sorghum [sorghum bicolor (L.) Moench]. A fallow treatment, consisting of stalk residue only, was used as a comparison. Fertilizer N rates for corn were 0, 50, or 100 kg N ha−1 for 1980 to 1983 and 0, 85, or 170 kg N ha−1 for 1984 to 1987. Hairy vetch produced the most cover crop dry matter with the highest percentage of N. During 1980 to 1983, corn grain yields were significantly higher with the vetch treatments than with rye or fallow treatments at the 0 and 50 kg N ha−1 rates with a tendency toward higher yields at the 100 kg N ha−1 rate. During 1984 to 1987, corn yields from the vetch treatments were significantly higher than the other cover treatments at all N levels. Grain sorghum, like corn yields, were greater with the vetch treatments than with the rye or fallow treatments, although the bigflower vetch treatment was not significantly higher than the fallow treatment at the 170 kg N ha−1 rate. The estimated fertilizer‐N equivalency of the hairy vetch‐N in the corn experiment was 75 kg N ha−1 and bigflower vetch was 65 kg N ha−1. Fertilizer N equivalency values in the grain sorghum experiment were estimated to be 125 kg N ha−1 for hairy vetch and 135 kg N ha−1 for bigflower vetch.
Water Relations of Differentially Irrigated Cotton Exposed to Ozone
Authors: Temple Patrick J.
Published: July 2010

This field study was conducted to test the hypothesis that plants chronically exposed to O3 may be more susceptible to drought kcause OM3 typically inhibits root growth and increases shoot‐root ratios in plants. Cotton (Gossypium hirsutum L. cv. Acala SJ‐2) was grown in open‐top chambers on Hanford coarse sandy loam (coarseloamy, mixed, non‐acid, thermic, Typic Xerorthents) in Riverside, CA. Plants were grown under three irrigation regimes: optimum water for lint production (OW), suboptimum or moderate drought stress (SO), and severely drought stressed (SS) and were exposed to seasonal 12 h (0800–2000) O3 concentrations of 0.015, 0.074, 0.094, or 0.111 μL L−1. Leaf xylem pressure potentials (Ψ1) and soil water content (Ψv) were measured weekly from June to October. Mean seasonal Ψ1 increased from −1.89 MPa to −1.72 MPa in low to high O3 treatments, averaged across soil water regimes. Ozone had no effect on seasonal water use of cotton, but water use efficiency was significantly reduced by O3 in OW and SO, but noit in SS treatments. Drought‐stressed plants extracted proportionally greater amounts of water from deeper in the soil profile than OW cotton, and O3 had no apparent effect on this redistribution of roots in the soil. Since O3 had no apparent effect on the ability of droughtstressed cotton to maintain Ψ1 and to increase root growth relative to shoot growth, this suggests that O3 may have little or no effect: on the potential of cotton to adapt to or tolerate drought.
Root Zone Water Balances of Three Low‐Input Millet Fields in Niger, West Africa
Authors: Payne W. A. , Wendt C. W. , Lascano R. J.
Published: July 2010

It is often assumed that pearl millet [Pennisetum americanum (L.) Schum.] production is limited by water supply despite the fact that little published data exist on water balances of low‐input millet fields. The objectives of this study were to: (i) quantify components of the field water balance of three sites, each in a different rainfall zone, and (ii) determine whether water supply was the primary limiting constraint to production at each site. The study was conducted on sandy soils in Niger, West Africa, during the 1985 growing season. Fields were near the villages of Chikal, N'Dounga and Kala Paté, which received 223, 344 and 428 mm of total rainfall, respectively. Soils were classified as Ustic Torripsamment at Chikal, Psammentic Paleustalf at N'Dounga, and Alfic Ustipsamment at Kala Paté Water balances were calculated to the depth of maximum root penetration, which was determined at harvest by digging pits. Measurements were made using a field calibrated neutron probe and nonrecording rain gauges. Results indicate that depth of maximum root penetration was not correlated with rainfall received after planting. Seasonal crop water supply was greatest at N'Dounga, where root development was greatest. Drainage below the zone of maximum root penetration was significant at Kala Paté at 43 d after sowing, when cumulative rainfall was only 143 mm, but negligible at the other sites. Drainage could not be separated from evapotranspiration at Kala Paté 67 d after sowing and thereafter. Total evapotranspiration was 272 mm at N'Dounga and 201 mm at Chikal. Cumulative change in water storage in the zone of maximum root penetration was 0 mm at Chikal, 39 mm at N'Dounga, and 46 mm at Kala Paté. Based on the amount of water held above − 1500 kPa in the zone of maximum root penetration and profile water distribution, we conclude that water was the primary limiting constraint only at Chikal in 1985. Water supply did not appear to be the primary limiting constraint at N'Dounga and Kala Paté. Similar conclusions were obtained using the amount of root zone water held above − 100 kPa. The study suggests that water supply may not be assumed a priori to be the primary production constraint to low input millet fields such as those studied here.
Harvest Management of a Crimson Clover Cover Crop For No‐Tillage Corn Production
Authors: Holderbaum J. F. , Decker A. M. , Meisinger J. J. , Mulford F. R. , Vough L. R.
Published: July 2010

Legume cover crops are valuable N sources for no‐tillage corn (Zea mays L.). However, little research has been done in assessing the management options for legume cover crops. Field studies were conducted on a Coastal Plain Matapeake silt loam soil (fine‐silt, mixed, mesic Typic Hapludult) from 1983 through 1986 to determine the effects of various harvest management schedules on total N contribution of legume cover crops, subsequent corn grain and silage yields, and total forage (combined cover crop and corn herbage) production. A crimson clover (Trifolium incarnatum L.) cover crop was subjected to no harvest; spring silage harvest with clippings removed (spring silage); and simulated pasture harvests with clippings from multiple harvests removed (pasture removed) or returned (pasture returned). A no‐cover control treatment was also included. No‐tillage corn was grown in the cover crop residues and two fertilizer N (FN) rates (0 and 90 kg ha−1) were applied in a split‐block design to each harvest management treatment. Averaged over 3 yr, multiple harvests of the cover crop vs. a spring silage harvest resulted in lower cover crop herbage yields (3.0 vs. 4.7 Mg ha−1) and total N content (114 vs. 146 kg N ha−1) for the multiple harvests. Corn grain and silage yields and corn N uptake were consistently higher following crimson clover cover than for no cover, regardless of harvest management, and were generally higher when the cover was left in place than following removal of the cover. There were FN responses regardless of harvest management treatment. The reduction in corn silage yield when the cover crop was harvested and removed was less than the cover crop herbage dry matter yield, resulting in greater total forage production when the cover crop was harvested as forage. Results suggest that harvest management options of a crimson clover cover crop offer flexibility in either optimizing subsequent corn grain yields or total forage production for no‐tillage cropping systems and provide control over how cover crop N is utilized in the overall cropping system.
Growth Patterns of Perennial Grasses in the Annual Grassland Type of Southwest Oregon
Authors: Borman M. M. , Krueger W. C. , Johnson D. E.
Published: July 2010

Southwest Oregon and northern California foothills are currently dominated by a variety of annual plant species. This study was designed to assess the potential of established perennial grasses to occupy two sites in the foothills ecosystem, Mediterranean/Maritime climatic regime, of southwest Oregon. Soils at Sites 1 and 2 are Darrow silty clay loam (fine, montmorillonitic, mesic Vertic Argixerolls) and Carney clay (fine, montmorillonitic, mesic Typic Chromoxererts), respectively, and annual precipitation at the sites averages 500 mm. Growth patterns of the perennial grasses were contrasted among each other and to the resident annual plants during fall, winter and spring growth periods. Of the perennial grasses, Idaho fescue (Festuca idahoensis Elmer), native to the area, and ‘Berber’ orchardgrass (Dactylis glomerata L.), introduced, most closely emulated the growth patterns of the resident annual grasses. These grasses initiated growth sooner, continued some growth through the winter and matured earlier than the other perennial grasses tested. Once established, Idaho fescue and Berber orchardgrass should be able to effectively compete with the resident annuals for resources and maintain their populations.
Continuous Application of No‐Tillage to Ohio Soils
Authors: Dick* W. A. , McCoy E. L. , Edwards W. M. , Lal R
Published: July 2010

No‐tillage (NT) crop production practices have been continuously maintained at four sites in Ohio for more than 25 yr. The original experiments involving NT were designed to determine how much tillage was required to produce crops with satisfactory yields and how tillage and rotation interact to effect crop yields, especially corn (Zen mays L.). Long‐term effects of NT on crop yields and soil properties are generally not known because few sites exist with histories of ≥20 yr of NT. This paper reports yield trends of corn and soybean [Glycine max (L.) Merr.] and changes in soil properties that occurred when NT was continuously practiced on soils in Ohio. Significantly lower yields for NT, as compared to conventional tillage (CT), were observed for monoculture corn and for soybean in rotation during the first 18 yr on a very poorly drained Mollic Ochraqualf soil. The yield differences observed for corn could be largely eliminated by crop rotation and for soybean by the use of phytophthera resistant/tolerant soybean cultivars. On a well‐drained Typic Fragiudalf soil, crop yields were always higher with NT than with CT. After 18 yr, yield trends indicated the negative impact of NT on the very poorly drained soil was greatly decreased and the yield advantages associated with NT on the well‐drained soil became even more pronounced. The change in yield trends did not appear to be associated with change in weather patterns. The long‐term NT sites also revealed organic matter, nutrients, and soil enzymes accumulated at the soil surface but decreased deeper (>20 cm) in the soil profile. Surface water runoff was found to be greatly decreased from the long‐term NT watershed site (≈9% slope) with only 12 mm of runoff measured between 1979 and 1985.
Botanical Composition of Tropical Grass‐Legume Pastures Estimated with Near‐Infrared Reflectance Spectroscopy
Authors: Pitman W.D. , Piacitelli C.K. , Aiken G.E. , Barton F.E.
Published: July 2010

Quantifying pasture composition requires either laborious or subjective approaches. Evaluations of near‐infrared reflectance spectroscopy (NIRS) to determine botanical composition of mixed pasture swards have shown potential. In this study, characterization of botanical composition of pastures comprised primarily of bahiagrass (Paspalum notatum Flugge), aeschynomene (Aeschynomene americana L.) and phasey bean [Macroptilium lathyriodes (L.) Urb.] by NIRS was evaluated. Three approaches (hand‐composited samples, single‐component samples, and actual pasture samples) were compared for equation development. Theoretical potential of NIRS is illustrated by high coefficients of determination (0.98–0.99) and low standard errors (1.4–2.9%) of equations for the above species from hand‐composited samples. Equations developed from the three approaches were evaluated for estimation of the botanical composition of a separate group of pasture samples. Equations developed from hand‐composited samples from a single source of each component were not acceptable for estimating composition of pasture samples despite the excellent calibration statistics. Single‐component samples approached adequate results only for composite total grass and total legume groups, even though the pasture sample composition appeared to be well represented in the calibration sample set. Equations from pasture samples provided useful estimates of sample means, although some individual samples were poorly estimated. Thus, botanical composition of these pastures may be estimated using equations from actual pasture samples, and estimates of total grass and total legume may be obtained from use of single‐component samples, which provides further labor reductions. A comparison of original software and updated software packages CAL, BEST, REG70, and partial least squares principal component regression showed none to be consistently superior.
Plant Responses to Stocking Rate in a Subtropical Grass‐Legume Pasture
Authors: Aiken G.E. , Pitman W.D. , Chambliss C.G. , Portier K.M.
Published: July 2010

‘Florida’ carpon desmodium [Desmodium heterocarpon (L.) DC] is a persistent legume under grazing but is often difficult to establish. Aeschynomene (Aeschynomene americana L.) and, especially, phasey bean [Macroptilium lathyroides (L.) Urb.] establish more reliably. Overseeding a mixture of these legumes in bahiagrass (Paspalum notatum Flugge) pastures could provide the quality forage and N input of legumes initially from the rapidly establishing species and for extended periods from the persistent carpon desmodium. The objective of this study was to evaluate the potential of such mixtures. Effects of stocking rate and grazing season on botanical composition, herbage availability, and herbage nutritive value were evaluated on a Pomona fine sand (sandy, siliceous, hyperthermic Ultic Haplaquod). Following overseeding of legumes in March 1987, pastures were grazed at three stocking rates in summer 1987 and in spring and summer 1988. Carpon desmodium increased from less than 1% at the start of grazing in 1987 to over 7% of the live herbage in 1988. Combined percentage of aeschynomene plus phasey bean decreased during 1987 from more than 4 to 1.6%. Carpon desmodium percentage was highest (P < 0.10) at the intermediate stocking rate, while percentage of other legumes was not affected by stocking rate. Herbage mass decreased linearly with increases in stocking rate in both summer grazing seasons. Leaf/stem ratio and nutritive value of legume leaf and stem were not affected by stocking rate but decreased with time during each grazing season. The short‐lived legumes, aeschynomene and phasey bean, provided high quality forage during the establishment period of carpon desmodium but contributed negligibly during the second year.
Corn Responses to Post‐tasseling Nitrogen Deprivation and to Various Ammonium/Nitrate Ratios
Authors: Reddy K.S. , Mills H.A. , Jones J.B.
Published: July 2010

Corn (Zea mays L.) takes up more than half of its total N after tasseling. An experiment was conducted to determine how the availability of N and the N form, NH4 or NO3, during the post‐tasseling period affect corn plant growth, ear development, and nutrient composition. In this experiment, corn hybrid ‘Pioneer 3343’ plants were grown hydroponically in pots outdoors with 50:50 NH4:NO3 up to the emergence of tassels and then the plants were either deprived of N or changed to various ratios of NH4:NO3 nutrition and grown to maturity. Nitrogen deprivation reduced both vegetative (stalk and leaf) and reproductive (cob, total kernel, and individual kernel) dry matter accumulation. Continuous supply of 50:50 ratio of NH4:NO3 produced greater vegetative dry matter than changing to either higher or lower ratios of NH4:NO3. The ratio of NH4:NO3 did not affect the ear dry matter production. Nitrogen deprivation decreased both leaf and kernel N concentration. While 50:50 NH4:NO3 ratio increased the leaf N concentration, all NH4 increased the kernel N concentration compared to other ratios. Nitrogen deprivation also reduced the concentrations of Mg, Fe, Mn, Zn, and B in the leaves but had no effect on the kernel nutrient composition. The cation and anion concentrations in the leaves and kernels were not according to the NH4 and NO3 effects (viz., uptake of cations greater and anions lower with NH4 than with NO3 nutrition), which were previously observed before tasseling. This difference may be due to a change in the uptake capacity for these nutrients after tasseling.
Transplantation as a Soybean Field Technique to Modify Root Nodule Occupancy
Authors: Fuhrmann Jeffry J. , Vasilas Bruce L.
Published: July 2010

Field studies of symbiotic interactions between soybean (Glycine max [L.] Merr.) and Bradyrhizobium japonicum (Kirch.) Jordon are often limited by an inability of specific inocula to compete successfully with indigenous bradyrhizobia for root nodule sites. The objective of this note is to describe and evaluate a transplantation technique for modifying soybean root nodule occupancy under field conditions. Pre‐nodulated seedlings were prepared under greenhouse conditions in containers designed for the generation of transplants. The inoculation procedures used ensured that all nodules initiated prior to transplanting contained only selected strains of B. japonicum. The seedlings were transplanted to field microplots when approximately 3 wk old and subsequently allowed to develop normally. The transplanted seedlings exhibited high rates of survival and excellent yield potentials. Control of nodule occupancy on tap roots and adjoining portions of major lateral roots was nearly complete for several weeks after transplanting.
Mainstem Leaf Development and Tiller Formation in Wheat Cultivars
Authors: Krenzer E. G. , Nipp T. L.
Published: July 2010

Mainstem leaf stage and percent tiller formation are measurements utilized to evaluate the development of wheat (Triticum aestivum L.). This study was conducted to determine whether there are differences for these measurements among 11 winter wheat cultivars. Ten hard red winter wheat and one soft white winter wheat cultivars were grown in a controlled environment chamber to determine their rate of mainstem leaf stage and tiller formation percentage for coleoptile (TO), first (Tl), second (T2), and third tillers (T3) when plants are grown in the absence of stress. Growth conditions were 12‐h photophase at 24 °C and 12‐h dark at 15 °C. Light intensity averages 500 μmol m−2s−1 photosynthetic photon flux density. Cultivars ranged from 5.3 to 6.4 in mainstem leaf stage at 700 growing degree‐days (GDD) after seeding and in number of GDD required per leaf. Therefore, before attempting to model wheat development, the response of mainstem leaf appearance to GDD for specific cultivars must be determined. For percent tiller formation, TO was quite variable, and cultivar differences were not significant. Therefore, percent tiller formation of TO may be too variable for detection of treatment differences. Even though a significant percent tiller formation difference occurred among cultivars for Tl, all but one cultivar formed 90 to 100% of Tl, T2, and T3.
Effect of Rill Erosion during Early Vegetative Growth on Winter Wheat Yield
Authors: Rasmussen P.E. , Douglas C.L.
Published: July 2010

The long‐term effect of soil erosion on lowering soil productivity is well documented, but little is known about how rill erosion occurring during the crop growing season affects yield. Rill erosion effects on winter wheat (Triticum aestivum L.) growth and yield were determined in six fields where rill erosion occurred during early vegetative growth. Soils were Walla Walla (coarse silty, mixed mesic Haploxeroll) or Athena (fine silty, mixed mesic Haploxeroll) silt loams at least 2 m deep. Rills were followed across landscape positions on slopes ranging from 1 to 15%. Rills paralleled rows in all six studies, and traversed rows in two of the six. Rill erosion reduced head density, dry matter yield, N uptake, and grain yield at all sites. The rill/non‐rill (R/NR) grain yield ratio (per square meter) varied from 0.84 to 0.94. The R/NR yield ratio was not affected by slope steepness or aspect, but was weakly correlated with yield level (greater loss at higher yields) and landscape position (lower slope positions had larger rills and greater yield loss). The grain R/NR ratio decreased with increasing rill depth but was not affected by rill width. Soil loss measured with a rillmeter was correlated with rill depth. The estimated yield reduction per ha associated with average rill development (11.7 cm deep rills, 26.7 kg m−2 soil loss in rill area, and 10 rill transects ha−1) was between 0.9 and 1.2%. Assuming a 36 Mg ha−1 soil loss (the average for sloping Haploxeroll soils of the Pacific Northwest), the calculated yield reduction from winter wheat fields yielding 5.2 Mg ha−1 is 88 kg grain ha−1 (about $13 ha−1 for wheat valued at $0.147 kg−1). This erosion cost would encompass a significant percentage of the landscape with sloping topography and is additional to any costs associated with long‐term loss of soil productivity.
AGSTATS—A Statistical Analysis Program for Simple Experiments
Authors: Karow Russell S.
Published: July 2010

AGSTATS is a statistical analysis program that allows county agents and growers to analyze completely randomized and randomized complete block experiments with a maximum of 15 treatments, six replications, and no missing plots. The user selects the experimental design to be used and is then asked for the number and label of treatments and replications. A row (treatments) and column (replications) table for data entry is displayed. The program allows changes in table headings, replication and treatment labels, and data. Output is a summary table including means, LSD, and CV values that can be stored on disk, printed, or both. The program will recycle to allow additional data using the same design‐treatment‐replication information or the user can enter information for a new trial. The program runs on IBM‐compatible computers. While intended for an inexperienced data analysis audience, the program is also useful for quick analysis of small lab, greenhouse, or field experiments and as a teaching aid.