bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal Establishment of Bermudagrass Using Plastic and Straw Mulches
Authors: Sowers R. S. , Welterlen M. S.
Published: July 2010

Bermudagrass [Cynodon dactylon (L.) Pers.] is normally established vegetatively during the early summer in the transition zone, to allow sufficient establishment time before the onset of freezing conditions in the fall. Clear polyethylene covers and straw mulches muse changes in the turfgrass microenvironment that may influence the rate of sprig establishment. The objective of this study was to evaluate the effects of barley (Hordeum vulgure L.) straw and clear polyethylene plastic mulch (0.04‐mm thickness) on the establishment of ‘Midiron’, ‘Tufcote’, and ‘Vamont’ bermudagrass from sprigs. Separate tests were conducted in the fall of 1983 and 1984 and the summer of 1984 and 1985. Summer spriggings were made in May, June, and July, months generally recommended for planting in the transition zone. Late‐season spriggings were made in August, September, and October. Plantings were made on a Sassafrass sandy loam (fine‐loamy, siliceous, mesic Typic Hapludult). Summer bermudngrass establishment was reduced under straw and polyethylene covers. Injury under plastic occurred to plantings made in May and June, which were exposed to mean soil temperatures above 41°C during the 8‐wk cover period. In contrast, plastic mulch stimulated early fall bermudagrass growth and delayed dormancy. August and September plantings remaining under plastic throughout the winter exhibited high winter survival in comparison to unmulched or straw mulched turf, and were nearly 100% established by 1 July of the following year. Spriggings under plastic planted after 20 September exhibited poor establishment by 1 July the following year. These studies showed that plastic covers can be used to extend the establishment season of bermudagrass into the fall; however, plastic covers are detrimental to summer bermudagrass establishment.
Soil Carbon Dioxide Distribution and Flux within the Open‐top Chamber
Authors: Nakayama F. S. , Kimball B. A.
Published: July 2010

Open‐top chamber use for exposing plants to various levels of CO2 and pollutant gases is increasing in field studies. In making a C balance of cotton [Gossypium hirsutum (L.) ‘Deltapine‐61’] for such a system, soil CO2 fluxes were observed to be significantly greater outside than inside the chamber. To find the cause, CO2 concentration was measured in the soil profile from 5‐ to 60‐cm depths of an Avondale clay loam [fine‐loamy, mixed (calcareous), hyperthermic Typic Torrifluvent]. The soil CO2 contents at the various depths sampled outside the chamber were higher than those inside the chamber. The differences in concentration were observable within 2 wk after the blower used to pass ambient of CO2‐enriched air through the chamber was turned on. The largest differences were present approximately 16 wk after the system had been in operation. Approximately 30 d was required for the soil CO2 levels inside and outside the chamber to become similar after the blower was turned off. Soil water content was not a factor causing this difference because it was nearly equal at both sites. Pressure differentials inside the growth chamber resulting from the blower operation could lead to a decrease in soil CO2 concentration and fluxes measured using the closed chamber technique.
Nitrogen Application to Cotton on Clay Soil: Timing and Soil Testing
Authors: Constable G. A. , Rochester I. J.
Published: July 2010

With the aim of improving utilization of N fertilizer and the flexibility of N application strategies in cotton (Gossypium hirsutum L.), five field experiments examined the response of cotton to N fertilizer, either applied before sowing or as applications before or after sowing, or both. The soils were Pellusterts with a high pH. Anhydrous ammonia was used as the N fertilizer throughout. Soil nitrate N, N uptake, and lint yield were measured in all experiments. There was a linear increase in N uptake with increased application of N fertilizer, with an average of 30% of applied N being taken up by the crop 120 d from sowing. Compared to a single presowing application, N recovery was increased by split application on two occasions, but on a further two occasions it was decreased. Split application increased lint yield on one occasion only—when compaction, waterlogging, and a long growing season allowed better utilization of sidedressed N. On all other occasions the two methods of N application produced similar yields. Therefore, sidedressing can be considered a viable practice on these soils and in this climate. Maximum yield was obtained when crop uptake was about 108 kg N/ha at 120 d from sowing, and was only partially affected by yield level. Soil nitrate N, sampled to a depth of 30 cm 4 wk before sowing, was closely correlated (r=0.86) with subsequent plant N uptake in nil fertilizer treatments. Therefore, N fertilizer requirement can be accurately determined by applying moderate levels of N before sowing, then subsequently testing for soil N on nil fertilizer strips to determine if any sidedressing is necessary. It was concluded that recovery of N fertilizer was generally poor, and improvement of this parameter has the potential to increase fertilizer use efficiency and productivity of cotton in this environment.
Comparing Sealed Chamber Digestion with Other Digestion Methods Used for Plant Tissue Analysis
Authors: Anderson D. L. , Henderson L. J.
Published: July 2010

A sealed chamber digestion (SCD) method was developed as a rapid and simple means of tissue digestion for micro‐samples. The objective of this study was to test SCD against other digestion methods used for plant‐tissue analyses. Sealed chamber digestion, dry ash combustion, nitric/perchloric acid wet ash digestion, and sulfuric acid/hydrogen peroxide wet ash digestion methods were evaluated for efficacy of organic matter destruction for elemental analysis of plant tissues. Eight tissue standards were collected from the National Bureau of Standards, the University of Georgia, and the Everglades Research and Education Center, University of Florida. The objective of this study was to compare the previously reported SCD method with other digestion methods used for plant tissue analyses. With the exception of analysis for Al and Fe, comparison of methods of analyses indicated that SCD did not differ greatly from other digestion methods. Digestion method efficacy, as determined by nutrient analysis, appeared to reflect the plant material digestibility and digestion method. The advantages and disadvantages of the methods studied are discussed.
Crop‐Specific Thermal Kinetic Windows in Relation to Wheat and Cotton Biomass Production
Authors: Burke J. J. , Mahan J. R. , Hatfield J. L.
Published: July 2010

Plant phenology and yield predictions require precise knowledge of crop‐weather relationships. The objective of this research is to identify an inherent biochemical trait that may provide a useful index to link the physical parameters of the environment with the plant biochemistry. We define the term thermal kinetic window as the range of plant temperatures at which the apparent Michaelis constant, Km, is at or below 200% of the minimum observed value. For example, the thermal kinetic window of wheat (Triticum aestivum L.) glyoxylate reductase for NADH is between 17.5 and 23°C, and the thermal kinetic window for cotton (Gossypium hirustum L.) is between 23.5 and 32°C. A linear relationship between the time that foliage temperatures were within their thremal kinetic window and plant biomass production was obtained for both wheat and cotton. Wheat and cotton were within their thermal kinetic windows less than 30% of the season, suggesting that approximately 70% of the growing season is available for increasing crop production either through changes in management practices or genetics. Measurements of foliage temperatures coupled with enzyme kinetics provide a unique description of the biological‐physical interactions.
Daily and Seasonal Evapotranspiration and Yield of Irrigated Alfalfa in Southern Idaho
Authors: Wright James L.
Published: July 2010

Daily water‐use data are needed for the development of modern irrigation scheduling techniques, the optimum allocation of water and energy resources, and improved irrigation management practices. This field study was conducted to measure evapotranspiration (ET) of well‐irrigated alfalfa (Medicago sativa L.) in the arid region of southern Idaho. The relationship of ET to forage yield was also investigated. The soil was Portneuf silt loam (coarse‐silty, mixed, mesic Durixerollic Calciorthids) common to much of the region. Daily and seasonal ET data were calculated for seven growing seasons from measurements obtained with mechanical weighing lysimeters equipped with electronic load cells. Daily alfalfa ET was highly variable. It occasionally exceeded 10 mm d−1 and averaged 8 mm d−1 during peak ET periods. From April through October, measured ET averaged 1022 mm for three harvests per season for 5 yr when soil water was nonlimiting. Corresponding average forage yield was 17.6 Mg ha−1 (120 g kg−1 water content) giving an overall water requirement of 58.1 mm (depth equivalent) to produce 1 Mg ha−1 of forage (581 m3 Mg−1) for a water‐use efficiency of 17.2 kg ha−1 mm−1. Harvest period and seasonal ET appear linearly related to pan evaporation and forage yield. The actual ET of well‐irrigated, high‐yielding alfalfa may be as much as 50% greater than previous estimates indicated for southern Idaho.
Band Spacing Effects of Dual‐Placed Nitrogen and Phosphorus Fertilizers on Corn
Authors: Eghball B. , Sander D. H.
Published: July 2010

Band spacing of P fertilizer potentially affects many factors which influence fertilizer P efficiency. Band spacing affects soil‐P fertilizer contact, probability of root‐P fertilizer contact, the time that roots contact the P fertilizer, the distribution of P fertilizer in the band, and energy requirement during application. Four field experiments were conducted to evaluate the effect of band spacing of dual‐placed N and P fertilizers on corn (Zea mays L.) grain yield and P uptake. Four band spacings of 30, 45, 60 and 75 cm were applied with three P application rates in 1983 and 1984, and five rates in 1986. Two application depths of 7.5 and 15 cm were applied in 1983 and 1984. The N rates were 200 kg N ha−1 in 1983 and 1986, and 75 and 150 kg N ha−1 in 1984. Applied P was less effective and N more effective in terms of grain yield as band spacing increased indicating a different optimum band spacing for P than for N. This caused the net effect of band spacing of dual‐applied N and P fertilizers to be nearly neutral. Seven‐leaf stage and ear‐leaf P were not affected by applied P at the high N application rate, but at the low N rate P concentrations increased as P rate increased indicating the importance of adequate N for P uptake early in the growing season. The wide band spacing of 75 cm performed poorly in grain yield response to applied N at the high N rate compared to the low N rate probably because of loss of N during application. Band spacing of N and P fertilizers did not cause significant variation in corn growth. Plants growing directly over the dual‐placed band did not yield more or less than other plants regardless of band spacing.
Ethephon Alteration of Corn Plant Morphology
Authors: Norberg O. S. , Mason S. C. , Lowry S. R.
Published: July 2010

Reduction in lodging, and plant and ear height resulting from ethephon application to corn (Zea mays L.) has been reported, but no attempt has been made to determine the influence of ethephon on internode properties and lodging. The objective of this study was to determine the influence of time and rate of ethephon application on plant and ear height, and length, diameter, and weight length−1 of internodes of corn plants. Ethephon was applied at rates of 0.0, 0.14,0.28, and 0.56 kg ha−1 at tassel elongation (TE), 6 d after tassel elongation (TE+6), and at ear elongation (EE) to Pioneer hybrid P3183 grown on Sharpsburg silty clay loam soil (fine, montmorillonitic, mesic Typic Argiudoll). Plant and ear height were reduced more by ethephon application at EE than at TE or TE+6. Increasing ethephon application from 0.0 to 0.56 kg ha−1 at EE resulted in plant and ear height reductions from 237 to 174 cm and 132 to 93 cm, respectively. Ethephon application resulted in reduced length of internodes, whereas diameter and weight length−1 increased. When applied at TE, ethephon resulted in a maximum of 48 mm reduction in internode length, 2.5 mm increase in internode diameter, and 0.017 g mm−1 increase in weight length−1; whereas application at EE resulted in a maximum of 99 mm reduction in internode length, 2.1 mm increase in internode diameter, and 0.019 g mm−1 increase in weight length−1. Stalk lodging was positively correlated to the length of Internodes 11 through 15. Application of ethephon resulted in large changes in the stalk morphology of corn plants, many of which contribute to reduced stalk lodging. Harvestable grain yield either declined or remained constant with ethephon application. These data suggest that ethephon may prove to be a useful research tool, especially for studying stalk lodging and plant architecture.
Lowland Rice Response to Urea Following Three Cowpea Cropping Systems
Authors: John P. S. , Pandey R. K. , Buresh R. J. , Prasad R.
Published: July 2010

The integrated use of legume green manure or legume residue with inorganic N fertilizer could offer rice (Oryza sativa L.) farmers an opportunity to reduce their expensive inorganic fertilizer inputs. A 2‐yr field experiment was conducted on an Andaqueptic Haplaquoll in the Philippines to determine the effect of cowpea [Vigna unguiculata (L.) Walp.] cropping systems on response of a subsequent rice crop to applied urea and effectiveness of several urea management practices for rice. The pre‐rice cropping systems including fallow, cowpea incorporated at the flowering stage as a green manure, and cowpea grown to maturity with either grain and pods removed or all aboveground vegetation removed prior to soil puddling for rice. The mean aboveground N content was 66 kg N ha−1 for green manure and 54 kg N ha−1 for mature cowpea without grain and pods. Rice yield responses following fallow and cowpea cropping with removal of all aboveground cowpea vegetation were similar, but mean rice grain yields were 0.9 and 0.7 Mg ha−1 higher following incorporation of green manure and residue, respectively. The green manure substituted for 34 and 54 kg urea‐N ha−1 in 1986 and 1987, respectively. Residue substituted for 44 and 50 kg urea‐N ha−1 in 1986 and 1987, respectively. Early application of urea (two‐thirds basal and one‐third at 5 d before panicle initiation) was superior to delayed application (one‐half at 14 d after transplanting and one‐half at 10 d after panicle initiation), even when supplemental N as green manure or residue was incorporated 15 d before transplanting. Cowpea grown for green manure or for grain, with incorporation of residues remaining after harvest, made similar positive contributions to rice yield, but growing cowpea to maturity offered the advantage of attaining approximately 1.0 Mg ha−1 cowpea grain production.
High‐Intensity Rainfall Rate Determination from Tipping‐Bucket Rain Gauge Data
Authors: Sadler E. J. , Busscher W. J.
Published: July 2010

High rainfall rates have a major impact on agriculture through runoff, erosion, and surface crusting and on other industries through sedimentation, failure of dams, and attenuation of radio waves. Traditional techniques used to measure and record rainfall have produced event totals or hourly rates. These are unsuitable for studying short‐term impacts in brief storms (e.g., 27 mm in 30 min). The objective of this work was to develop an analytical procedure to provide millimeter per minute resolution in rainfall rate from short‐term, tipping‐bucket, rain gauge data. Counts of tips in 1‐min intervals were assembled into an array of accumulated rainfall over time during an event. A cubic spline was fitted to the accumulated rainfall curve and then differentiated to yield the rate curve. Four synthetic rainfall patterns were used to test the technique by matching original and reconstructed curves. Regression of reconstructed rates on input rates resulted in 9 ranging from 0.989 to 0.996. When applied to field data from 8 events (total: 209.5 mm) in July 1984 and 6 events (total: 139 mm) in July 1985, the technique described rainfall rate as a smooth, continuous function of time. This characteristic improves the suitability of the data for input to models of infiltration and runoff that adapt time steps to overcome numerical instability under rapidly changing conditions.
Plant Population Density and Row Spacing Effects on Soybean at Post‐Optimal Planting Dates
Authors: Boquet D. J.
Published: July 2010

Information on cultural practices for determinate soybean, Glycine max (L.) Merr., at post‐optimal planting dates is needed in the southern USA where planting is often delayed by weather or doublecropping. The objective of this study was to examine the effects of plant population density (PPD) on determinate soybean at two postoptimal planting dates in relation to interrow spacing, plant architecture, and yield components. A 3‐yr. soybean field study on Sharkey clay (very fine montmorillonitic, thermic, nonacid, vertic Haplaquept) was planted at post‐optimal dates of 20 June and 3 July. ‘Davis’ (MG VI) and ‘Braxton’ (MG VII) soybean were planted in 0.5 and 1.0 m row spacing (RS) at PPD at 6.4,13, 26, 38, 51 plants m−2 under irrigated and nonirrigated conditions. Yields were higher at the 0.5 m RS than at the 1.0 m RS, and were higher at the June date than at the July date. Highest yields at the June date (2.99 and 1.97 Mg ha−1) were with PPD of 38 and 13 plants m−2 at the 0.5 and 1.0 m RS, respectively. Yields were highest at the July date (2.45 and 1.53 Mg ha−1) with PPD of 51 and 26 plants m−2 at the 0.5 and 1.0 m RS, respectively. Increase in PPD up to 38 plants m−2 increased main stem length and decreased all other plant components. Decrease in main stem yield was proportionately smaller than the increase in PPD resulting in a net yield gain from higher PPD. Decrease in branch stem yield was proportionately greater than the increase in PPD resulting in a net yield loss from PPD increase. For determinate soybean planted at a 0.5 m RS an increase in PPD above that needed at optimal dates was necessary to obtain highest yields at post‐optimal planting dates. Soybean planted at the 1.0 m RS had much lower yield and was much less responsive to increase in PPD.
Water Deficit Development in Old and New Soybean Cultivars
Authors: Frederick J. R. , Wooley J. T. , Hesketh J. D. , Peters D. B.
Published: July 2010

Crop productivity depends to some degree on a cultivar's capacity to maintain a high plant water status over a range of soil water conditions. We conducted this 2‐yr study to examine whether newer soybean [Glycine max (L.) Merr.] cultivars have more favorable leaf turgor potentials than older cultivars during the pod elongation and seed enlargement stages of crop development, and to determine whether the older and newer cultivars differ in leaf water potential components and stomatal resistances when grown under drought stress. Two older (‘Manchu’ and ‘Dunfield’) and two more recent (‘Clark 63’ and ‘Williams 82’) cultivars were field grown under irrigated (I) and nonirrigated (NI) conditions at Urbana, IL. Although large differences in soil water potential were found between the water treatments, afternoon leaf water potentials of the cultivars were decreased only an average of 0.14 MPa and afternoon leaf turgor potentials were not reduced as a result of the NI treatment. In both the NI and I plots, Manchu and Dunfield generally had lower and similar leaf turgor potentials, respectively, as did the modern cultivars during the day. Under NI conditions, greater stomatal closure occurred for the older cultivars than for the newer cultivars, indicating that the older cultivars are more efficient in conserving water under drought stress.
Production and Nutritive Value of Florigraze Rhizoma Peanut in a Semiarid Climate
Authors: Ocumpaugh W. R.
Published: July 2010

‘Florigraze’ rhizoma peanut (Arachis glabrata Benth.) is a warmseason perennial forage legume that has received considerable research emphasis in Florida. However, little is known about its value outside of Florida. A field experiment was conducted on an established stand of Florigraze at Beeville, TX on a Parrita sandy clay loam (Clayey, mixed, hyperthermic, shallow Petrocalcia Paleustolls). Dry matter (DM) production, crude protein (CP) and in vitro digestible dry matter (IVDDM) of leaf blades and stem components were determined by sampling biweekly from June through January for each of two years. Treatments were total‐seasonal accumulated growth compared to regrowth of peanut defoliated in mid‐July or late‐August. A randomized complete block (RCB) design with three replicates was used, and 900‐cm2 areas were hand clipped to ground level for yield determinations. Typical for semiarid climate, rainfall was erratic and its distribution varied between years. Total‐seasonal DM accumulation of 8 to 10 Mg ha−1 was recorded each season. Rainfall influenced DM production patterns, percent leaf, stem IVDDM, and leaf and stem crude protein (CP). Rainfall and defoliation treatment had no effect on leaf IVDDM. Leaf IVDDM declined slowly during each year (−0.4 to −0.9 g kg−1 d−1) but exceeded 700 g kg−1 during the entire growing season. Florigraze loses leaves in response to drought stress. Autumn leaf production was unaffected by defoliation treatments. Leaf blade CP concentration was 1.7 to 1.9 times greater than that of stems. Because of leaf loss during late summer, spring and early summer production should be harvested in June or July. Forage production and nutritive value were sufficiently high, even under limited rainfall conditions, to warrant further investigation.
Harvest Management Effects on Alfalfa Yield and Root Carbohydrates in Three Georgia Environments
Authors: Brown L. G. , Hoveland C. S. , Karnok K. J.
Published: July 2010

Alfalfa (Medicago sativa L.) hay harvest management may need to be modified in the southeastern USA due to the mild winters and hotter summers compared with northern production areas. The objectives of this study were to evaluate the effect of three harvest treatments (10, 50, and 10% bloom until midsummer when one harvest was delayed until 50% bloom‐referred to as “summer rest” management) on herbage yield and seasonal trends of total nonstructural carbohydrates (TNC) in the roots of irrigated semidormant ‘Apollo’ and nondormant ‘Fla‐77’ alfalfa. The experiments were conducted for 2 yr in the Georgia Mountains on Bradson clay loam (Typic Hapludult, clayey, oxidic, mesic), Piedmont on Cecil sandy clay loam (Typic Hapludult, clayey, thermic, kaolinitic), and Coastal Plain on Greenville sandy clay loam (Rhodic Paleudult, clayey, thermic, kaolinitic). Alfalfa at all three locations gave satisfactory yield (12.7 Mg ha−1) when harvested at 10% bloom throughout the growing season including late fall. There was no advantage to either cultivar from harvesting at 50% bloom or allowing a summer rest period. Location effects were minimal. Root TNC concentrations were lowest in midsummer, greatest in late autumn, and decreased during winter. Root TNCs ranged from 200 to 560 g kg−1 for Fla‐77 and 150 to 580 g kg−1 for Apollo. There was no effect of cultivar or harvest management on root TNC concentrations. These results indicate that root TNCs are not a primary limiting factor for alfalfa hay production in the southeastern USA and that harvest can continue throughout the year with no adverse effect on forage yield.
Plant Density and Nitrogen Fertilizer Effects on Pearl Millet Production in Niger
Authors: Bationo A. , Christianson C. B. , Baethgen W. E.
Published: July 2010

Pearl millet (Pennisetum glaucum [L.] R. Br) is an important crop in many developing countries in West Africa and provides 80 to 90% of the food requirement for Niger. Farmers plant at a wide range of densities which may affect crop response to fertilizer. Studies were conducted for 3 yrs in a sandy soil in southern Niger to assess the effects of N fertilization (0–60 kg N ha−1) and plant density (5000–40 000 pockets ha−1, three plants per pocket) on millet yield and yield components. The effects of N and density on yield were influenced by midseason rainfall. With low midseason rainfall, highdensity planting reduced yield slightly and N had no effect. With average or above rainfall, N application and high plant density increased millet grain yield four‐ to fivefold. Nitrogen increased stover production 33% in a dry year and 100% in the wetter year. Plant density significantly affected stover yield only in 1983, a year with high early season rainfall. Increasing plant density tended to increase stover production in all years. Grain weight in 1983 decreased 14% when plant density exceeded 20 000 pockets ha−1. Nitrogen fertilizer doubled the number of heads per pocket at low plant densities when rainfall was normal or above. A plant density of 15 000 to 20 000 pockets ha−1 and N application of 30 kg N ha−1 in two splits achieved good yields in average and wet years, with only a small yield reduction in the drought year.
Root Distribution and Shoot Development in No‐Till Full‐Season and Double‐Crop Soybean
Authors: Coale F. J. , Grove J. H.
Published: July 2010

Dry matter accumulation by soybean [Glycine max (L.) Merr.] has been studied extensively, but few data are available on the relationship between shoot development and root distribution of no‐till full‐season and double‐crop soybean. Row spacing and K availability effects on shoot growth are also well understood, but have not been thoroughly integrated with measures of root growth. The objectives of this research were to characterize soybean root length density and distribution as well as shoot dry matter accumulation under no‐tillage soil management for: (i) full‐season and double‐crop planting dates, (ii) high and low soil K fertility levels, and (iii) narrow and conventional row spacings. Potassium fertility did not alter total shoot weight at R1, R5, or R7, but did alter shoot dry matter partitioning at R7. Later planting dates reduced shoot growth at R1, R5, and R7. Seed yield was increased by greater K availability, earlier planting and a narrower row width. Dry soil conditions during vegetative growth reduced root length density (RLD). As water became more available during reproduction, RLD increased. With adequate soil moisture, full‐season soybean RLD was greater than double‐crop soybean RLD. Surface soil RLD was greater when soil K fertility was low. Leaf abscission was delayed by K stress. In crop development periods when root growth was most active, the root length/shoot dry weight ratio was greater in double‐crop than in full‐season soybean. Double‐crop soybean produced relatively more root length in support of shoot growth than did full‐season soybean. Root growth was more affected by soil K availability and less affected by plant spacial arrangement and density than was shoot growth.
Utilizing Legume Cropping Systems to Reduce Nitrogen Fertilizer Requirements for Conservation‐tilled Corn
Authors: Oyer L. J. , Touchton J. T.
Published: July 2010

The need to reduce production costs has promoted a renewed interest in using legumes as a source of N for non‐leguminous summer crops. Development of legume cropping systems which will permit reseeding of winter cover‐crop legumes is a promising approach to reducing legume establishment costs. Field studies were conducted in Alabama for 4 yr on Wynnville sandy loam and Dothan fine‐sandy loam soils (fine‐loamy, siliceous, thermic, Glossic Fragiudults and Plinthic Paleudults, respectively) to determine the effects of both cash crop and winter cover‐crop legumes in cropping systems on N fertilizer requirements of corn (Zea mays L.) grown in a conservation‐tillage system. On the Wynnville soil, soybean (Glycine max L. Merr.) was more effective in providing early season N, and clover (Trifolium incarnatum L.) in providing late‐season N. The system with both soybean and clover resulted in an even more effective contribution of N to corn grain yield, and a higher yield level than that of continuous corn regardless of N fertilizer rate. On the Dothan soil, the benefits of cropping systems were not as pronounced, and the responses were eliminated by N fertilization, suggesting increased yields were due to N and not to a rotation effect. On both soils, in years of adequate and inadequate rainfall, the reseeding crimson clover system, in combination with a soybean‐corn rotation, consistently produced the highest yields of the systems studied, and provided a 68 to 159 kg N ha−1 fertilizer equivalent for corn.
Rotational Cropping Sequence Affects Yield of Corn and Soybean
Authors: Crookston R. K. , Kurle J. E. , Copeland P. J. , Ford J. H. , Lueschen W. E.
Published: July 2010

There are numerous reports of the beneficial effects of rotating corn (Zea mays L.) and soybean [Glycine max (L.) Merr.]. However, few studies have been specifically designed to document the important corn‐soybean rotation effect. The objective of this study was to determine the impact of various corn and soybean cropping patterns on the yield of both crops. The 9‐year field study conducted at two locations was managed for maximum production. Cropping sequences consisted of: continuous monoculture with the same cultivar; continuous monoculture with cultivars alternated; annual rotation of the two crops; and 1, 2, 3, 4, and 5 yr of monoculture following 5 yr of the other crop. Annually rotated corn yielded 10% better, and first‐year corn yielded 15% better than corn under monoculture. Annually rotated soybean yielded 8% better, and first year soybean yielded 17% better than soybean under monoculture. With monoculture of either crop, alternating two different cultivars annually resulted in the same yield as continuous cropping of just one cultivar. There were differences in the response of the two crops to increasing years of monoculture: the lowest corn yield was from second year corn; the lowest soybean yield was from extended monoculture. Total corn dry weight was affected by cropping sequence but soybean dry weight was not. Our data suggest that, from a yield standpoint, a superior cropping sequence for Minnesota would include at least three, and possibly more crops.
Hydraulic Conductivity of Cotton Roots as Influenced by Plant Age and Rooting Medium
Authors: Brar G. S. , McMichael B. L. , Taylor H. M.
Published: July 2010

Models of water extraction by plant root systems often contain the basic assumption that hydraulic conductivity of the root system is a constant value. An experiment was conducted to determine if plant age or rooting medium environmental conditions affected hydraulic conductivity of cotton (Gossypium hirsutum L.) roots. Hydraulic conductivity was measured by the pressure outflow method at 12, 24, 36, and 48 d after planting (DAP) on roots grown in both hydroponics and sand. Hydraulic conductivity decreased 45% in nutrient‐solution‐grown and 57% in sand‐grown roots from 12 DAP to the mean of 24, 36, and 48 DAP. Hydraulic conductivity of sand‐grown roots was 4 to 10 times lower than that for roots grown hydroponically, whether conductivity was compared at equal DAP or at equal root length.
Development and Growth of Tropical Maize at Two Elevations in Hawaii
Authors: Manrique Luis A. , Hodges Tom
Published: July 2010

Development and growth response of maize (Zea mays L.) to an increase in temperature and daylength has been studied in temperate regions, but little is known of the effects of daylength on leaf number, leaf area development, and grain yield in tropical environments. A temperature‐by‐daylength experiment was conducted in the field on the Island of Maui, Hawaii (USA) at 282 and 640 m elevations during summer 1988 to examine the effects of daylength and temperature on leaf number, leaf area index (LAI), and grain yield of Pioneer hybrid X304C. Under high nutrient fertility and adequate water supply, plants were grown at natural daylength (12–13.5 h, control), control + 0.5‐h, 14‐, 17‐, and 20‐h daylengths. These daylengths were artificially produced by extending the natural daylength with 500‐W lamps. For a 97‐d period, mean maximum air temperatures were 26.8 and 27.8 °C while minimum air temperatures for the same period were 20.1 and 16.4 °C at the 282 and 640 m elevations, respectively. Longer days reduced mature leaf appearance rate and delayed tassel initiation and tasseling. Leaf tip appearance rate was unaffected by daylength but leaves took more thermal time for full expansion. Leaf area index in the 17‐ and 20‐ h daylengths was 7.0 at 77 d after planting, which was 1.8 times the LAI in the control and 14‐h daylengths. Physiological maturity in the 17‐h daylength was delayed by 33.5 and 38.5 d at 282 and 640 m, respectively. Maturity in the 20‐h daylength was delayed by 41.0 and 48.5 d at 282 and 640 m, respectively. Grain yields and harvest indices at both elevations decreased significantly with increasing daylength. Overall, warm temperatures at 282 m enhanced the adverse effects of daylength on grain yield.
Leaf Reflectance and Transmittance in Soybean and Corn
Authors: Walter‐Shea E. A. , Norman J. M. , Blad B. L. , Robinson B. F.
Published: July 2010

Leaves have a major influence on canopy reflectance when they constitute the main spatial component in a vegetative canopy. Near normal‐incidence, directional‐hemispherical reflectance and transmittance of in situ individual leaves of soybean (Glycine max., Merr.) and corn (Zea mays, L.) were characterized as a function of wavelengths and growth. Spectral properties were measured in seven wavebands with an integrating sphere and prototype radiometer unit. Individual leaves periodically were monitored from emergence and unfolding through 47 d in soybean and 77 d in corn. Visible reflectance and transmittance decreased in soybean as leaves expanded, but increased after full leaf expansion. An opposite pattern was observed with soybean near‐infrared radiation (NIR) reflectance. Spectral properties varied little in mid‐ and upper‐canopy corn leaves with the exception of the green spectral region. Near constant values were attributed to the fact that corn leaves are fully expanded by the time they have fully emerged. Reflectance and transmittance properties of adaxial and abaxial surfaces differed by as much as an absolute 5% in soybeans while there were essentially no differences in corn. Differences in surface reflectance and transmittance in soybean were attributed to the dorsiventral morphology of soybean leaves. Reflectance and transmittance from adaxial and abaxial leaf surfaces may have to be considered in modeling soybean canopies while one surface should suffice to describe light interaction with corn canopy leaves.
Fertility and Weed Stress Effects on Performance of Maize/Soybean Intercrop
Authors: Weil Ray R. , McFadden Mary Ellen
Published: July 2010

Intercropped corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] may produce more total yield per hectare than either grown separately, ie., land equivalent ratio (LER) =1. Low N fertility, limited moisture, and weed competition have each been reported to result in high land equivalent ratios. Thus it was hypothesized that intercropping advantages were greater under stress conditions. The objectives were to study the effects of soil fertility stress (F1 = low N‐P‐K,F2 = high N‐P‐K), weed competition stress (W1 = unweeded, W2 weeded), and four cropping systems (M2S, M1S, M2, S; where M2 = high density maize, M1 = low density maize, and S = soybean at normal density) on the performance of maize and soybean, and on the growth of weeds. ‘Cargill 921’ maize and ‘Union’ soybean were planted simultaneously in 1985 and 1986 in alternate rows spaced at 0.5 m on a typic Hapludult in Maryland. Land equivalent ratios and maize equivalent yields were calculated. Dry matter production was determined early in the season, and grain yield plus weed dry matter were determined at final harvest. LER values (mean of 1985 and 1986) ranged from 0.89 (W2F1,M2S) to 1.18 (W2F1M1S). The LER data showed that at high fertility levels, weed stress increased the relative advantage of intercropping. In addition, when plots were weeded, LER increased from 0.96 to 1.13 under fertility stress. Maize equivalent yields were calculated from the relative prices of maize and soybeans. The highest maize equivalent yields in all cropping systems in both years occurred under optimal conditions (W2F2).
Nitrogen and Dry Matter Accumulation, Remobilization, and Losses for Mediterranean Wheat during Grain Filling
Authors: Papakosta Despo K. , Gagianas A.A.
Published: July 2010

Dry matter and N accumulated by winter wheat (Triticum spp.) plants until anthesis are of importance under a Mediterranean climate because yield greatly depends on translocation of pre‐anthesis assimilates to grain. This field study was conducted to assess the effect of N fertilizer and cultivar on the amount of pre‐anthesis dry matter and N accumulated and remobilized, and the possible N losses. Two bread (T. aestivum L.) and two durum (T. durum Desf.) wheat cultivars were grown in a silty clay (Typic Xerorthent) in 1986 and 1987. Nitrogen at a rate of 150 kg ha−1 was applied before planting or 100 kg N ha−1 was applied before planting and then 50 kg N ha−1 at early boot stage. Cultivar dry matter translocation efficiencies ranged from 2.3 to 36.4%, N‐translocation efficiencies from 60.9 to 80.7%, and the contribution of pre‐anthesis assimilates to grain from 6 to 73%. Split N application reduced the contribution of pre‐anthesis assimilates to grain. High amounts of N (>200 kg ha−1), which had accumulated by anthesis led to net N losses at maturity, even with high yields (>6 Mg ha−1). No N losses were observed when N content at anthesis was lower than about 150 kg ha−1. However, at values ranging between these upper and lower limits, N loss was yield dependent (only yields >8 Mg ha−1 prevented N losses). Split N application tended to reduce N losses. Results indicated that the greater the amount of dry matter and N accumulated before anthesis, the higher the translocation rates of dry matter to grain and the greater the risk of net N losses at maturity.
Effect of Maize Maturity on Radiation‐Use Efficiency
Authors: Major D. J. , Beasley B. W. , Hamilton R.I.
Published: July 2010

Maize (Zea mays L.) production has expanded into short‐season regions but it is not known whether the radiation‐use efficiency (RUE, g MJ−1)1 of new early hybrids differs from those grown in traditional maize‐growing regions. In this study, spectral reflectance measurements were used to derive estimates of photosynthetically active radiation (PAR) absorbed to compare the RUE of 10 maize hybrids that varied in adaptation from Iowa 110‐d relative maturity to the earliest 60‐d relative maturity hybrids commercially available. Reflectance measurements were made radiometrically in the visible and near‐infrared regions of the electromagnetic spectrum at approximately weekly intervals in 1985, 1986, and 1988. The 10 maize hybrids were grown at three densities at Lethbridge, Alberta, on an irrigated silty clay loam soil (Typic Haploboroll). The Scattering by Arbitrarily Inclined Leaves (SAIL) model of canopy reflectance was inverted to produce daily estimates of the fraction of absorbed PAR, p. Multiplying p by daily PAR irradiance gave daily estimates of absorbed PAR (APAR, MJ m−2), which were summed for the season. Radiation use efficiency was obtained by dividing whole‐plant yield at harvest by seasonal (emergence to harvest) APAR. Averaged over years, hybrids, and densities, RUE was 2.3 g MJ−1. Radiation‐use efficiency increased with population density across hybrids regardless of maturity. Seasonal RUE was lower than reported in the literature but there is evidence that chilling injury due to low night temperatures at the high elevation and semi‐arid location of the study reduced photosynthesis. The results suggest that spectral reflectance can be used effectively by breeders to identify hybrids that are more efficient users of PAR and that maize hybrids resistant to chilling injury may be needed at high latitudes.
Control of Nutrient Mixing and Uptake by Irrigation Frequency and Relative Humidity
Authors: Kargbo D. , Skopp J. , Knudsen D.
Published: July 2010

The distribution of nutrients and water between mobile and immobile pores should influence nutrient uptake. The distribution can be regulated through control of the water‐filled pore space. This research was conducted to determine the effect of varying soil‐water content and water uptake upon nutrient uptake. Corn (Zea mays L.) was grown in a growth chamber for 2 wk at 35 or 55% relative humidity (RH). Three soils [Boelus LS, 5% slope (sandy over loamy, mixed, mesic Udic Haplustoll); Boelus LS, 2% slope; and Plano Soil (fine‐silty, mixed, thermic Typic Haplustolf)] were watered to field capacity (θmax). Plants on each soil were allowed to extract water to one of three minimal levels (θmin1, θmin2, θmin3) before rewatering. After harvest, P and K content and other root and leaf parameters were determined. The values of θmin were chosen so that, for each soil, the three values ensured no low‐water stress. Effective diffusion coefficients were determined for the three Increased Omin for a soil required for frequent watering, which led to greater mixing of solutes between pores. At 55% RH, no water treatment significantly affected P and K flux, despite significant differences in diffusion coefficients. At 35% RH, however, phosphate flux to roots increased as θmin increased. The significant increase of phosphate flux with more frequent watering at low RH suggests that plant uptake is affected by soil physical processes other than simple diffusion and convection to individual roots. More frequent watering results in greater mixing of solute between pores containing mobile and immobile water and, consequently, greater uptake.
Mechanisms for Overyielding in a Sunflower/Mustard Intercrop
Authors: Putnam D.H. , Allan D.L.
Published: July 2010

Two intercrop patterns and sole crops of mustard (Brassica hirta Moench) and sunflower (Helianthus annuus L.) were planted in 1988 and 1989 on a Waukegan silt loam soil (fine‐silty over sandy or sandyskeletal, mixed, mesic Typic Hapludoll) at Rosemount, MN, to examine mechanisms for overyielding [Land Equivalent Ratio (LER) > 1.0] in this intercrop system. We hypothesized that reduced competition between species for N and water were the mechanisms for previously observed yield benefits in both crops. Secondary objectives were to examine the importance of intercrop structure and N fertilizers on resource use and yield advantage. A strip intercrop pattern where 2.28‐m strips of sunflower (76‐cm rows) alternated with 2.28‐ m strips of mustard (15‐cm rows) was compared with a more intimate row intercrop pattern of 76‐cm sunflower rows interplanted with four 15‐cm rows of mustard. Nitrogen was applied at planting at 0 or 112 kg N ha−1 to whole plots, with planting patterns allocated to subplots in a split‐plot design. Soil water content, nitrate N, and total N were measured at different locations and depths in the intercrop and sole crop patterns during the growing season. Mustard rows adjacent to sunflower in the strip intercrop yielded an average of 61% more than sole crop rows. Sunflower rows adjacent to mustard in the strip intercrop yielded an average of 40% more than sole crop rows. Yields of both sunflower and mustard were lower in the row intercrop compared with respective sole crops. Land equivalent ratios ranged from 0.96 to 1.43 in the strip intercrop and were generally below 1.0 in the row intercrop. Application of N did not consistently affect LER. Soil depletion patterns indicated that border rows of mustard obtained both soil water and N from the strips planted to sunflower at a time when demand for these resources by sunflower was low. Sunflower border rows obtained water and N from mustard strips later in the season. These data implicate complementary use of water and N as important mechanisms for the positive land equivalent ratio observed in this strip intercrop.
Potassium in Two Humid Tropical Ultisols under a Corn and Soybean Cropping System: I. Management
Authors: Cox F.R. , Uribe E.
Published: July 2010

Sub‐optimum soil K levels often limit corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] production in humid tropical Ultisols. The objectives of this study were to determine soil and plant critical levels of K and optimum rates of K fertilization for corn and soybean grown in the Amazon Basin of Peru. Two field experiments were conducted on Typic Paleudults, a loam and a sandy loam. Five K rates, ranging from 0 to 120 kg ha−1, were broadcast and incorporated prior to planting the first crop of a corn, corn, soybean rotation at both sites. At the loam site, K treatments were reapplied at the end of this rotation and three more corn crops grown. The corn stover was returned while the soybean stover was removed. Critical exchangeable K levels for corn were 110 kg ha−1 on the loam and 90 kg ha−1 on the sandy loam, while for soybean it was 75 kg ha−1 for both soils. The critical levels of K in plant tissue at flowering were 13 g kg−1 in corn and 12 g kg−1 in soybean. Soybean seemed to lower exchangeable K to where K was released from non‐exchangeable sources. An annual cropping system of corn and soybean with an intervening cover crop during the rainy season is proposed for the region. Potassium fertilization is recommended only prior to growing corn at 90 kg ha−1 on a loam and 60 kg ha−1 on a sandy loam.
Simulating Winter Wheat Production in Three Tillage Systems Using the Nitrogen Tillage Residue Management Model
Authors: Davidoff B. , Wilhelm W. W. , Skopp J.
Published: July 2010

Crop production system analysis is necessary to identify tillage and residue management practices that affect crop production. The objective of this study was to evaluate the potential of using the Nitrogen Tillage Residue Management (NTRM) model to evaluate the influence of tillage practices on winter wheat (Triticum aestivum L.) yield. Modifications of the NTRM model were required to simulate winter wheat production. The model was calibrated using site‐specific information obtained from a tillage‐nitrogen rate experiment conducted at the High Plains Agricultural Laboratory near Sidney, NE, on an Alliance silt loam (fine silty, mixed, mesic Aridic Argiustoll). Model output was compared to measured yields of winter wheat grown on three tillage treatments [moldboard plow, subsurface tillage (1.5 in‐wide “V” blade), and no tillage] during three seasons. Simulations within the year of calibration agreed within ± 28% of measured yields for the moldboard plow and subsurface tillage treatments. Deviations were observed between predicted and measured yields when using data outside the year of calibration. Crop coefficients, determined in the calibration process, affected the yield predictions of NTRM. Grain yield predictions by NTRM were very sensitive to initial and stabilized soil bulk density values within the range of 1.2 to 1.3 Mg m−3 (1% change in input value caused a five‐fold change in predicted yield). Usefulness of the model could be enhanced through greater documentation on calibration procedures and explanation of calibration coefficients. Results obtained here should alert users to the need for care in application of results obtained from complex, highly interlinked models, such as NTRM.