bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen Remobilization during Grain Filling in Wheat: Genotypic and Environmental Effects
Authors: Barbottin Aude , Lecomte Christophe , Bouchard Christine , Jeuffroy Marie-Hélène
Published: May 2005

In wheat (Triticum aestivum L.), nitrogen remobilization from the vegetative organs of the crop to the grains has been shown to depend on environmental factors and genotype. We performed, for a set of 10 winter wheat genotypes, field experiments at six sites over a 2‐yr period. By measuring nitrogen uptake at flowering (NUF from 32–284 kg ha−1), the amount of remobilized nitrogen (REMN from 24–228 kg ha−1) and nitrogen remobilization efficiency (NRE from 0.44–0.92) we were able to determine the effect of genotype and environment on the relationship between REMN and NUF. Environment and genotype had significant effects on nitrogen remobilization and nitrogen remobilization efficiency, which mainly depended on treatment (nitrogen and fungicide) and site. For environments without limiting factor during the grain‐filling period, we found that REMN was not dependent on the genotype and could be estimated by a single two‐parameter linear relationship (REMN = 4.13 + NUF × 0.76, r2 = 0.97). We analyzed the effect of drought stress before and after flowering, high temperature during these periods, nitrogen availability and disease pressure on REMN by comparing observed and estimated REMN. The effect of the environment on the relationship between nitrogen uptake at flowering and nitrogen remobilization depended on nitrogen uptake during grain‐filling period and disease pressure and was also affected by genotype. Disease‐resistant genotypes seemed to be able to keep remobilization efficiency stable in conditions of strong disease pressure, whereas nitrogen remobilization efficiency decreased strongly in susceptible genotypes under the same conditions.
Gas Exchange and Leaf Ultrastructure of Tinnevelly Senna, Cassia angustifolia, under Drought and Nitrogen Stress
Authors: Ratnayaka H. H. , Kincaid D.
Published: May 2005

Choice of crops is limited in dry agro‐ecosystems. Senna, Cassia angustifolia Vahl, a tropical medicinal plant, has potential as a dryland crop. This study was conducted to investigate gas exchange and leaf surface ultrastructural responses of senna to drought and foliar‐applied nitrogen under greenhouse conditions. Drought was imposed cyclically as four, 1‐wk spells by withholding water. Additional nitrogen was provided as a foliar treatment of 1% (w/v) urea at the end of each of first three drought cycles. Drought‐stressed plants had the same net photosynthesis (Pnet) as well‐watered plants until the leaf water potential dropped below approximately −0.8 MPa. Leaf water potential of approximately −2 MPa completely suppressed Pnet. Foliar nitrogen treatment increased Pnet > 30% in both water‐stressed and well‐watered plants. Intrinsic water use efficiency was unaffected by cyclic drought. Leaf area per plant increased 156% because of foliar nitrogen treatment in well‐watered plants but remained unchanged in drought‐stressed plants. Stomatal count per leaflet decreased 25% or more because of drought regardless of foliar nitrogen treatment on either abaxial or adaxial leaf surface. Foliar nitrogen treatment decreased adaxial but increased abaxial stomatal count regardless of drought treatment. Trichome count was more than eight times greater on the abaxial than the adaxial leaf surface under any treatment combination. Adaxial trichome number increased under drought, but decreased under nitrogen treatment. Abaxial trichome count increased because of drought only in plants deprived of nitrogen treatment. Maintenance of high carbon gain and water use efficiency, drought deciduousness, and plasticity in stomatal and trichome counts under both drought and nitrogen stress appeared to confer stress tolerance in senna.
Genetic Diversity ofCynodon transvaalensisBurtt‐Davy and Its Relatedness to HexaploidC. dactylon(L.) Pers. as Indicated by AFLP Markers
Authors: Wu Y. Q. , Taliaferro C. M. , Bai G. H. , Anderson M. P.
Published: May 2005

Cynodon transvaalensisBurtt‐Davy (African bermudagrass) is valued as turf and for use in interspecific hybridization withC. dactylon(L.) Pers. var.dactylonto produce turf cultivars. Little information is available regarding the magnitude of genetic variation within the taxon. Accordingly, this study was undertaken to evaluate the genetic diversity among 14C. transvaalensisaccessions and to examine the phylogenetic relatedness ofC. transvaalensis, two hexaploid (2n= 6x= 54)C. dactylonvar.dactylonaccessions, twoC. transvaalensisby hexaploidC. dactylonvar.dactyloninterspecific tetraploid (2n= 4x= 36) F1hybrids, and one putative tetraploidC. dactylonvar.dactylonbyC. transvaalensistriploid (2n= 3x= 27) F1hybrid. Fluorescence‐labeled amplified fragment length polymorphism (AFLP) DNA profiling was used to study the genetic relationships among these accessions. A total of 381 polymorphic AFLP markers were amplified from 13 primer combinations. The 14C. transvaalensisaccessions and the putative triploid F1hybrid clustered into one group and had genetic dissimilarity coefficients ranging from 0.01 to 0.51. The 14C. transvaalensisaccessions had genetic dissimilarity coefficients ranging from 0.01 to 0.34. TheC. dactylonvar.dactylonaccessions and the two tetraploid F1hybrids clustered in the second group, with genetic dissimilarity coefficients ranging from 0.17 to 0.33. The tetraploid F1hybrids were more closely related toC. dactylonvar.dactylonthan toC. transvaalensis, while the opposite was true for the putative triploid F1hybrid. The results indicate the presence of genetic diversity inC. transvaalensisthat could be exploited in intra‐ and interspecific breeding improvement.
Impact of Reduced Lignin on Plant Fitness
Authors: Pedersen J. F. , Vogel K. P. , Funnell D. L.
Published: May 2005

Lignin content of crop plants has been reduced by traditional plant breeding, natural and induced mutations, and insertion of transgenes. The effects of these genes and associated lower lignin content have been examined in terms of agricultural fitness or with regard to economically harvestable yields of useful plant products, or, in the case of some perennial species, survivability over multiple years. In general, crop yields are depressed by significant reductions in lignin content. Other negative effects observed in plants with lowered lignin contents include lodging and reduction of long‐term survival of some perennial species. However, the interactions of genes involved in lignin metabolism with genetic background and the environment in which the low‐lignin crop is cultivated are substantial. Examples are provided that demonstrate that lignin can be reduced in specific lines or populations without damaging fitness. It is concluded that it will be essential to incorporate lignin reducing genes into numerous genetic backgrounds and combinations, and evaluate the resulting lines in diverse environments, to discover optimal combinations and to obtain a true measure of value and fitness in agricultural systems.
Root Segregation of C3 and C4 Species Using Carbon Isotope Composition
Authors: Eleki Krisztina , Cruse Richard M. , Albrecht Kenneth A.
Published: May 2005

Partitioning roots for studying cropping systems containing more than one species is important since root growth interaction could influence system performance. The study objective was to test a method for segregating plant species roots from soil samples taken in a mixed stand of corn (Zea mays L.), a C4, and kura clover (Trifolium ambiguum M. Bieb.), a C3 plant. Soil cores containing both corn and kura clover roots were obtained at three distances from the corn row and at two depths in a Rozetta silt loam soil (moderately well drained, fine‐silty, mixed, superactive, mesic Typic Hapludalf). Root composition of these C4 and C3 species was based on 13C/12C ratios expressed as δ13C. A significant linear relationship (r2 = 0.99) was found between the δ13C and the percentage of corn roots in samples containing known ratios of corn and kura clover roots. This relationship was used to determine corn and kura clover root percentages in field samples. Ratios of 13C/12C effectively segregated corn and kura clover root materials obtained from soil samples and seem to be a powerful tool for partitioning roots of C3 and C4 plants in similar studies.
How Do Lignin Composition, Structure, and Cross‐Linking Affect Degradability? A Review of Cell Wall Model Studies
Authors: Grabber John H.
Published: May 2005

Because of the complexity of plant cell wall biosynthesis, the mechanisms by which lignin restrict fiber degradation are poorly understood. Many aspects of grass cell wall lignification and degradation are successfully modeled by dehydrogenation polymer‐cell wall (DHP‐CW) complexes formed with primary walls of corn Zea mays L. This system was used to assess how variations in lignin composition, structure, and cross‐linking influence the hydrolysis of cell walls by fungal enzymes. Altering the normal guaiacyl, syringyl, and p‐hydroxyphenyl makeup of lignin did not influence cell wall degradability; each unit of lignin depressed cell wall degradability by two units. Plants with perturbed lignin biosynthesis often incorporate unusual precursors into lignin and one of these, coniferaldehyde, increased lignin hydrophobicity and further depressed degradability by up to 30%. In other studies, lignin formed by gradual “bulk” or rapid “end‐wise” polymerization of monolignols had markedly different structures but similar effects on degradability. Reductions in cell wall cross‐linking, via oxidative coupling of feruloylated xylans to lignin or nucleophilic addition of cell wall sugars to lignin quinone‐methide intermediates, increased the initial hydrolysis of cell walls by up to 46% and the extent of hydrolysis by up to 28%. Overall, these studies suggest that reductions in lignin concentration, hydrophobicity, and cross‐linking will improve the enzymatic hydrolysis and utilization of structural polysaccharides for nutritional and industrial purposes. In ongoing work, we are developing a DHP‐CW system for dicots and are investigating how cross‐linking and various acylated and unusual monolignols influence the formation of lignin and the degradation of cell walls by rumen microflora.
Correlation of Genotype Performance for Agronomic and Physiological Traits in Space‐Planted versus Densely Seeded Conditions
Authors: Hansen K. A. , Martin J. M. , Lanning S. P. , Talbert L. E.
Published: May 2005

Wheat breeding programs often have a generation of intense selection among space‐planted individuals. An ultimate goal is always high yield potential of genotypes when transferred to densely seeded conditions. The goal of this experiment was to identify traits that may be selected in spaced‐plants that are correlated with high yield potential under densely seeded conditions. We tested 20 spring wheat (Triticum aestivum L.) genotypes under three planting densities over a 2‐yr period under both irrigated and nonirrigated conditions. Several traits were correlated with yield potential within seeding densities, including flag leaf width, grain fill period, and days needed to reach Haun growth stage 5. Additionally, genotype performance in spaced‐planted versus densely seeded conditions was highly correlated for many of the measured traits. In particular, genotype performance for grain yield was significantly correlated between the planting densities (r = 0.83). Additionally, flag leaf width and development at Haun growth stage 5 were highly correlated between planting densities on the basis of mean performance over all four environments. These traits were also highly correlated when comparing individual space‐planted environments to the mean genotype performance in the densely seeded environments. Genotype performance for grain fill period was highly correlated between planting densities on the basis of means of all four environments (r = 0.87). These correlations were lower, though generally significant, when each of the four space‐planted environments was considered independently. In general, data from this study suggest that selection among space‐planted genotypes for wide flag leaf, rapid growth to Haun stage 5, and long grain fill period may result in increased yield potential in densely seeded conditions.
Reporting Forage Allowance in Grazing Experiments
Authors: Sollenberger Lynn E. , Moore John E. , Allen Vivien G. , Pedreira Carlos G. S.
Published: May 2005

Stocking rate has a major effect on animal performance, but comparable stocking rates may result in a wide range in performance across environments because of differences in forage mass or sward canopy characteristics. Forage allowance is a function of both forage mass and stocking rate and can be a powerful tool for explaining differences in animal performance. Some methods used to express forage allowance in the literature do not allow useful comparisons across grazing methods or among management strategies within a method. In addition, many include a unit of time which violates the definition of forage allowance as a point‐in‐time measure. A meaningful method of reporting forage allowance is needed that applies across a wide range of pasture management treatments. This paper suggests a method that does not include a unit of time, has application across continuous and rotational stocking methods, and within the rotational stocking method applies to any size or number of pasture subunits.
Genetic Improvement Rates of Short‐Season Soybean Increase with Plant Population
Authors: Cober Elroy R. , Morrison Malcolm J. , Ma Baoluo , Butler Gail
Published: May 2005

Studies with a series of historic soybean [Glycine max (L.) Merr.] cultivars have found genetic improvement rates for seed yield of about 0.5% per year since soybean was first cultivated in Canada. Work with maize (Zea mays L.) has shown seed yield differences between old and new hybrids are more pronounced under higher seeding rates. The objective of our research was to determine the effect of plant populations on the rate of genetic improvement of short‐season soybeans. Soybean cultivars released from1934 to 1996 were grown in 40‐cm‐wide rows at several seeding rates (Exp. 1, 42 cultivars grown at 25, 50, 75 seeds m−2 in 1998 and 1999; and Exp. 2, seven cultivars grown at 25, 50, 100, 150, 200 seeds m−2 in 1999 and 2000) in two fields for 2 yr at Ottawa, ON. Genetic improvement rates were based on cultivar year of release and were compared across plant populations. In Exp. 1, seed yields did not reach a plateau. In Exp. 2, a seed yield plateau was reached and genetic improvement rates generally increased with plant population. Maximum rates of genetic improvement occurred at plant populations three to four times greater than current commercial practice (40 plants m−2). A plateau for seed yield was reached at lower plant populations compared to plateaus for genetic improvement rates which were reached at higher plant populations (>80 plants m−2). Higher plant populations also resulted in earlier maturity, increased plant height, and increased lodging. Seed protein increased and seed oil decreased with higher plant populations. New soybean cultivars appear more tolerant to plant population stress than older cultivars.
Effect of Temperature on the Expression of Necrosis in Soybean Infected with Soybean mosaic virus
Authors: Zheng C. , Chen P. , Gergerich R.
Published: May 2005

Soybean mosaic virus (SMV) causes mosaic symptoms in susceptible soybean [Glycine max (L.) Merr.] cultivars and stem‐tip necrosis (STN) in some soybean cultivars carrying resistance genes. The objective of this study was to examine the effect of different temperature regimes on the expression of SMV‐induced STN. Three soybean isolines, ‘Essex’ (rsv, mosaic to SMV strains G1 and G7), V94‐3971 (Rsv1, resistant to G1 and necrotic to G7), and V262 (Rsv1‐n, necrotic to G1 and mosaic to G7), were inoculated with G1 and G7 and maintained in growth chambers with a 12‐h photoperiod and constant temperatures of 10, 15, 20, 25, 30, 32, 33, and 35°C. The STN in V262 induced by G1 and in V94‐3971 by G7 developed at 10, 15, 20, 25, and 30°C, on 44, 41, 14, 8, 8 days after inoculation (DAI), respectively. No STN reaction was induced by either strain at 35°C. Further study demonstrated that STN was induced 7 DAI at 32°C in V262 by G1 and in V94‐3971 by G7, but mosaic symptoms developed in both genotypes at 33°C. However, STN was induced in V262 7 DAI by G1 and in V94‐3971 14 DAI by G7 at an alternate temperature of 33°C day/20°C night. Stem‐tip necrosis was also observed in V262 8 DAI by G1, but not in V94‐3971 by G7 at an alternate temperature 35°C day/20°C night. Essex exhibited mosaic symptoms when infected with G1 and G7 at all temperatures tested, and virus was detected by enzyme‐linked immunosorbent assay (ELISA). Stem‐tip necrosis is a SMV strain‐specific, thermosensitive response associated with SMV resistance genes.
A Threshold Model for Multiyear Genebank Data Based on Different Rating Scales
Authors: Hartung K. , Piepho H. P.
Published: May 2005

Genebanks routinely assess plant characteristics of accessions on an ordinal rating scale. A common problem with long‐term data is that the rating scale is changed from time to time. This paper proposes a method for joint analysis of data from different rating scales, assuming a threshold model with a common latent scale for the different rating systems. The method may be used to derive mean scores on any one of the rating scales based on a long‐term series of evaluation trials, as is illustrated using evaluation data on barley (Hordeum spp.). While the proposed method was motivated by data problems encountered in genebanks, it may be of equal interest in other areas of application, such as plant breeding, where rating scales change across time.
A Method of Controlling Corn Rootworm Feeding Using a Bacillus thuringiensis Protein Expressed in Transgenic Maize
Authors: Vaughn Ty , Cavato Tracey , Brar Gurdip , Coombe Timothy , DeGooyer Todd , Ford Stephanie , Groth Mark , Howe Arlene , Johnson Scott , Kolacz Kathryn , Pilcher Clinton , Purcell John , Romano Charles , English Leigh , Pershing Jay
Published: May 2005

The corn rootworm (CRW; Diabrotica spp.) is one of the most serious pests of corn in the USA. Chemical insecticides and crop rotation have been the only two options available to growers for managing CRW. Unfortunately, both of these tactics can be ineffective as a result of either resistance or behavioral modifications. In this paper, we describe transgenic maize (Zea mays L.) hybrids that control CRW. These hybrids were created with a Cry3Bb1 Bacillus thuringiensis (Bt) variant that is approximately eight times more lethal to corn rootworm larvae than the wild‐type protein. A DNA vector containing the modified cry3Bb1 gene was placed under control of a root‐enhanced promoter (4‐AS1) and was introduced into embryonic maize cells by microprojectile bombardment. Described here is the molecular genetic characterization, protein expression levels, and field performance of the recently commercialized MON863 hybrids.
Diallel Analysis in Cassava Adapted to the Midaltitude Valleys Environment
Authors: Jaramillo G. , Morante N. , Pérez J. C. , Calle F. , Ceballos H. , Arias B. , Bellotti A. C.
Published: May 2005

Cassava (Manihot esculenta Crantz) is an important commodity for industrial processes in tropical countries as one of the few alternatives to compete with imported maize (Zea mays L.). To maintain this competitiveness, cassava breeding needs to be as efficient as possible. This study provides one of the first attempts to produce quantitative genetic data to aid breeding efficiency, through the analysis of a diallel set among nine parental clones adapted to the midaltitude valleys environment. Thirty clones represented each F1 cross (with three exceptions). Evaluations were conducted in two contrasting environments with three replications in each location. The specific combining ability (SCA) effects were relatively more important than general combining ability (GCA) effects for root yield. In the case of harvest index, dry matter content (DMC) and plant type architecture GCA effects were about twice as large as those from SCA effects. Reaction to mites (Mononychellus tanajoa Bondar) and white flies (Aleurotrachelus socialis Bondar) (based on single‐location data) showed the strongest influence of GCA effects on the expression of a given trait. Yield data demonstrates the excellent potential of this crop for the tropical production of starch and source of energy in animal feed that could compete with the international markets.
Detecting Genetic Changes over Two Generations of Seed Increase in an Awned Slender Wheatgrass Population Using AFLP Markers
Authors: Ferdinandez Yasas S. N. , Coulman Bruce E. , Fu Yong-Bi
Published: May 2005

Diverse native grass populations are being developed for revegetation and land reclamation purposes, but little is known about the maintenance of the genetic diversity of these developed populations during the process of seed increase. The objectives of this study were to assess the genetic shift over two generations of seed increase in a multisite composite population (AC Pintail) of the self‐pollinating awned slender wheatgrass [Elymus trachycaulus subsp. subsecundus (Link) Gould] and to compare its genetic variation with the released cultivar AEC Hillcrest. AC Pintail was formed by bulking seed of 200 plants collected from 60 sites across the prairie of western Canada. The amplified fragment length polymorphism (AFLP) technique was applied to assay 50 plants from each of four populations (AC Pintail G0, G1, and G2 and AEC Hillcrest breeder seed). For each sample, seven AFLP primer pairs were applied and 194 polymorphic bands were scored. AC Pintail revealed more polymorphic bands (74%) than AEC Hillcrest (47%), and most of the scored bands for AEC Hillcrest had occurrence frequencies approaching 1 or 0. The largest within‐population AFLP variation observed resided within AC Pintail G0 (30.3), followed by G1 (29.7), G2 (27.9), and AEC Hillcrest (10.4). Significant differences were found among these seed sources and >95% of the total AFLP variation resided within the three AC Pintail populations. Fifty‐three bands displayed significant changes from G0 to G1 and 76 from G0 to G2 of AC Pintail. These results indicate that AC Pintail harbored more genetic variation than AEC Hillcrest but could lose up to 8% of the original diversity in the first two generations of seed increase.
Embryogenic Callus Induction and Regeneration in a Pentaploid Hybrid Bermudagrass cv. Tifton 85
Authors: Jain Mukesh , Chengalrayan Kudithipudi , Gallo-Meagher Maria , Mislevy Paul
Published: May 2005

Hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt Davy] cv. Tifton 85 is a major forage grass in the southeastern USA that suffers severe yield losses because of insect damage. A facile, cultivar‐specific regeneration protocol is required to pursue genetic improvement of Tifton 85 for incorporating insect resistance into this valuable forage crop. An efficient regeneration system that uses somatic embryogenesis from immature inflorescences of Tifton 85 has been established. Young, immature inflorescence explants proved to be an excellent source for obtaining embryogenic callus, as opposed to apical meristems and nodal segments. Embryogenic callus with demonstrable morphogenetic competence was obtained on MS basal medium containing 30 g L−1 sucrose, 4 mg L−1 ; 2,4‐dichlorophenoxyacetic acid (2,4‐D), 0.01 mg L−1 6‐benzylaminopurine (BAP) and 200 mg L−1 casein hydrolysate. The regenerants were rooted on hormone free MS basal medium supplemented with 30 g L−1 sucrose, successfully established in soil under greenhouse conditions, and did not show any phenotypic differences compared with wild‐type Tifton 85 plants.
Seed Dormancy Imposed by Covering Tissues Interrelates to Shattering and Seed Morphological Characteristics in Weedy Rice
Authors: Gu Xing-You , Kianian Shahryar F. , Foley Michael E.
Published: May 2005

Seed dormancy, a major adaptive trait in plants, facilitates the survival of weeds and provides for resistance to preharvest sprouting (PHS) in cereal crops. Seventeen weedy strains and 24 cultivars of rice (Oryza sativa L.) were evaluated for germinability to screen for donors of dormancy genes. Extremely dormant genotypes were identified from the weedy strains. These genotypes displayed hull‐ and pericarp/testa‐imposed dormancy. Three dormant weedy strains, LD, TKN12‐2, and SS18‐2, were crossed and backcrossed with the nondormant breeding line EM93‐1 to determine the relationship between dormancy and the shattering, awn, hull color, and pericarp/testa color characteristics. All these characteristics interrelated to the covering‐imposed dormancy; the weedy forms of the characteristics significantly reduced germination in the BC1F1 populations. Moreover, multiple linear regression analyses revealed significant effects of interaction between the characteristics on dormancy in the populations. The interrelation and interaction reflect the importance of combined effects of dormancy and other weedy characteristics in the adaptation of weedy populations to agroecosystems, and suggest that domestication and breeding activities have eliminated dormancy alleles at loci near the genes for shattering and the morphological characteristics from improved cultivars.
Best Linear Unbiased Prediction of Cultivar Effects for Subdivided Target Regions
Authors: Piepho H. P. , Möhring J.
Published: May 2005

Breeding for local adaptation may be economically viable providing there is sufficient genotype × subregion interaction. If the targeted subregion is part of a larger region covered by a testing network, information from neighboring subregions can be exploited to gain more precise estimates for the targeted subregion. For balanced data, the simplest approach is to use genotypic mean estimates for the whole target region, and this has often been shown to yield better predictions than simple means per subregion. A disadvantage of this approach is that it gives equal weight to all neighboring subregions and the targeted subregion, thus ignoring potential heterogeneity in information content. The objective of the present paper is to propose a method that allows a weighted combination of data from several subregions and to compare that method to other estimators. The proposed method is based on best linear unbiased prediction, which employs a weighted mean of subregion means. It follows from the theory of mixed models that the resulting estimator is optimal under the assumed model, minimizing prediction errors and maximizing the expected gain from selection. Using published variance component estimates, we found the resulting predictions to be superior to other approaches. We also show that the estimator is beneficial when selecting for global adaptation.
Trends over Time among Cotton Cultivars Released by the Oklahoma Agricultural Experiment Station
Authors: Bayles Melanie B. , Verhalen Laval M. , Johnson William M. , Barnes Bradley R.
Published: May 2005

Twelve cotton (Gossypium hirsutum L.) cultivars, released by the Oklahoma Agricultural Experiment Station (OAES) between 1918 and 1982 inclusive, were evaluated in multiple environments to estimate selection progress over time for lint yield, six fiber properties, eight agronomic characters, and three diseases. Lint yield increased 1.2 to 3.0 kg ha−1 yr−1 on dryland and 3.7 to 5.6 kg under irrigation. Five of six experiments indicated that a selection plateau had not yet been reached for lint yield. Increases in fiber length of 0.04 to 0.06 mm yr−1 and of 0.02 mm yr−1 were observed for 2.5 and 50% span lengths, respectively. Uniformity index and micronaire displayed significant differences among cultivars, but no significant trends over time. T0 fiber strength increased by 0.5 kN m kg−1 yr−1 Initially, T1 fiber strength declined; but since the mid‐1940s, its trend was upward by 0.6 kN m kg−1 yr−1 in a generally linear fashion. Picked and pulled lint percentages increased rapidly at first but reached a plateau in the mid‐1940s. Boll size increased over time, and bur size increased slightly. Weight of lint per boll increased through 1955, but has since remained essentially constant. Relatively large improvements were made in lint index through 1964; but since then, the trait has remained stable. Seed index increased by 0.02 g (100 seed)−1 yr−1 on dryland and by 0.03 g under irrigation. Lock tenacity increased by 1.7 g force yr−1 Positive trends over time were also noted for resistance to bacterial blight [caused by Xanthomonas campestris pv. malvacearum (Smith) Dye] and to the Fusarium wilt [caused by Fusarium oxysporum Schlect. f. sp. vasinfectum (Atk.) Snyd. & Hans.]–root‐knot nematode [Meloidogyne incognita (Kofoid & White) Chitwood] complex but not for tolerance to Verticillium wilt (caused by Verticillium dahliae Kleb.). The above findings were compared with those in numerous other breeding programs. This information provides a historical perspective on genetic gain for a number of traits among the cotton cultivars released by the OAES.
Mechanical Resilience of Degraded Soil Amended with Organic Matter
Authors: Zhang Bin , Horn Rainer , Hallett Paul D.
Published: May 2005

Organic matter may help prevent the degradation of the soil pore structure by mechanical stresses, and consequently the impact of compaction and surface erosion. To obtain a mechanistic understanding of some of the processes involved, we amended an Ultisol with peat particles, at amendment rates of 0, 10, and 50 g kg−1, and subjected the peat‐soil mixtures to different wet/dry cycles (1, 4, or 10). Mechanical stresses were imposed to the soil as direct shear, surface shear, and virgin compression tests. The objective was to determine the effect of increasing organic matter on the resistance and resilience of the soil pore structure to mechanical stresses, after wet/dry cycles. Peat amendment increased soil porosity, mainly in the fine pores (<6 μm), whereas an increased number of wet/dry cycles affected the coarse pore fraction (>50 μm). Soil shear strength decreased with a greater peat‐amendment rate. For soil amended with 50 g kg−1 of peat, increasing the number of wet/dry cycles increased the compressibility index from 1.14 to 1.43 and the friction angle under shear by 6°. Although peat may decrease the resistance to compression, the initial soil pore structure and the resilience to this mechanical stress was greatly improved. Wetting and drying cycles improved the impact of peat on the mechanical resistance of the soil, but reduced resilience slightly. The results suggest that to amend with organic matter will improve recovery from vehicle traffic damage and improve water retention during dry periods, providing better conditions for plants and microbes.
Does Soil Surface Roughness Increase or Decrease Water and Particle Transfers?
Authors: Darboux Frédéric , Huang Chi-hua
Published: May 2005

Most of prior research showed increasing soil roughness delayed runoff and reduced total runoff and sediment yields but failed to differentiate roughness effects on water runoff and on sediment production. This study was conducted to assess separately the effects of soil surface depressions on runoff initiation and water and particle fluxes. A 5‐m long soil box, filled with a silt loam, was split into 0.6‐m wide paired smooth vs. rough plots with manually formed depressions, and subjected to a sequence of 24 mm h−1 simulated rainstorms at 5% slope. Eight experiments were conducted under different upstream inflows and subsurface regimes (drainage or seepage). Collected data include time to runoff initiation and fluxes of water and particles after an apparent steady state was reached. Depressions delayed the runoff initiation by storing water into puddles and enhancing infiltration. Once runoff reached an apparent steady state, surfaces with initial depressions produced 10% greater water flux than the initially smooth surfaces, regardless, the subsurface moisture regime. Roughness had no significant effect on steady‐state particle flux and concentration. Our results indicate that the only assured soil and water conservation benefit from surface depressions is due to the delay in runoff initiation at the beginning of the rain event before the entire surface is contributing to runoff.
Recovery of Residual Fertilizer‐N and Cotton Residue‐N by Acala and Pima Cotton
Authors: Fritschi Felix B. , Roberts Bruce A. , Rains D. William , Travis Robert L. , Hutmacher Robert B.
Published: May 2005

Little is known about the availability of residual fertilizer‐N and cotton (Gossypiumspp.) residue‐N to subsequent crops. This study determined the effects of two soil types and N fertilization rates on the recovery of residual15N‐fertilizer and15N from labeled cotton residue in the soil and plants of subsequent cotton crops. Microplots in the San Joaquin Valley, California, on a Panoche clay loam [fine‐loamy, mixed (calcareous), thermic Typic Terriorthents] and a Wasco sandy loam (coarse‐loamy, mixed, nonacid, thermic Typic Torriorthents) were used to trace the fate of15N from labeled aboveground cotton residue separately from the15N in roots and soil. Total15N‐fertilizer recovery in the second year after application averaged 5.8% for Acala (G. hirsutumL.) and 2.9% for Pima (G. barbadenseL.) cotton. In the third year after application, total15N‐fertilizer recovered by Acala averaged 2.0% on the clay loam soil and 3.3% on the sandy loam. Most of this recovered15N‐fertilizer was cycled through soil pools and roots and only small amounts originated from labeled aboveground residue. Virtually all of the15N applied in the form of labeled aboveground residue and recovered in the soil was found in the top 0.3 m. The15N‐fertilizer which cycled through belowground pools was found mainly in the top 0.6 m of the soil. Recovery of residual15N‐fertilizer appears to contribute little to total cotton N uptake in the second and third crop after application.
AUTOMATION OF A FALLING HEAD PERMEAMETER FOR RAPID DETERMINATION OF HYDRAULIC CONDUCTIVITY OF MULTIPLE SAMPLES
Authors: Johnson D. O. , Arriaga F. J. , Lowery Birl
Published: May 2005

Measuring hydraulic conductivity of saturated soil (Ks) is one way to quantify soil hydraulic properties. However, this technique is very time consuming for both in situ and laboratory measurements, and often one is limited to measuring only one sample at a given time. Automation of hydraulic measurements has been suggested, but this has not been done for laboratory Ks measurements. Thus, we propose to use pressure transducers to measure Ks in multiple soil cores with a falling head permeameter. To accomplish this, an automated falling head permeameter was developed by attaching pressure transducers to falling head permeameters to measure Ks of soil cores in the laboratory and a datalogger was used to record the readings. To test this method, 64 soil core samples were taken from two locations, 30 from a sandy soil, 23 from a silt loam soil, and 11 from a silty clay loam soil. The automated unit allows for six samples to be processed with minimal human oversight compared with only one sample being read manually (conventional method), requiring frequent observations during a period often >30 min. When values obtained using the automated method were compared with values obtained for the same cores using the manual technique, there was no statistical difference at the 95% level.
Validation of the Arya and Paris Water Retention Model for Brazilian Soils
Authors: Vaz Carlos Manoel Pedro , de Freitas Iossi Murilo , de Mendonça Naime João , Macedo Álvaro , Reichert José M. , Reinert Dalvan José , Cooper Miguel
Published: May 2005

The Arya and Paris (AP) model predicts soil water retention curves from soil particle‐size distribution (PSD) data based on the similarity between these two functions. The AP model estimates pore radius (ri) from the radius (Ri) of spherical particles by scaling pore length with a parameter α. This paper evaluates the performance of the AP model with representative Brazilian soil types using three constant α values: α = 1.38, 0.938 (literature values), and 0.977, (obtained in the present work); and a α‐variable approach, where α is determined as a function of soil water content (θ). The study was performed with 104 soil samples collected in three sites. The soil PSD curves were obtained with an automatic soil particle analyzer based on the attenuation of γ‐ray by dispersed soil particles falling in a liquid medium and the soil water retention were measured with tension table and Richard chamber methods. The best mathematical representation of the α = f(θ) relationship was obtained with a first‐order exponential decay equation [α = 0.947 + 0.427exp(−θ/0.129)] that provided values of α in the range from 1.37 (θ = 0 m3 m−3) to 0.96 (θ = 0.6 m3 m−3). The root mean square deviation values of estimated and measured θ were 0.062 m3 m−3 for α = f(θ), 0.073 m3 m−3 for α = 0.977, 0.080 m3 m−3 for α = 0.938, and 0.136 m3 m−3 for α = 1.38. Therefore, for these set of soils the α‐variable approach and the constant ones using 0.977 and 0.938 presented the best estimation for the soil water retention relationships.
Measuring the Unsaturated Hydraulic Conductivity of Growing Media with a Tension Disc
Authors: Caron Jean , Elrick David
Published: May 2005

In greenhouse and nursery production, there is an increasing interest in water conservation and environmental quality. The use of closed and semi‐closed subirrigation systems to grow plants potted in organic growing media is an important step in this direction. However, the design of efficient subirrigation systems requires a detailed characterization of the unsaturated hydraulic conductivity of the organic substrates on rewetting. In many cases, organic substrates have extremely high‐saturated hydraulic conductivities and also exhibit a dual porosity. Given the lack of a suitable technique for measuring the unsaturated hydraulic conductivity of these substrates near saturation, as well as at saturation in pots (the equivalent of “field conditions” in nursery and greenhouse production), a new in situ procedure has been developed. It is based on an analytical solution to steady state upward flow and assumes a single (SEA) or piecewise exponential (PEA) relationship between the unsaturated hydraulic conductivity and the soil water potential. The proposed method was tested for a sand and an organic growing medium. The results indicate that the unsaturated hydraulic conductivity curve may be obtained from water flux measurements using a specifically designed tension disc placed on top of the substrate, and that the estimates on rewetting are much more accurate, particularly at water contents close to saturation, than those obtained using the instantaneous profile method. Moreover, the proposed procedure is easy to carry out, requires only an inexpensive tension disc and is based on a sound physical representation of the rewetting process. Results indicated that the PEA is appropriate for most substrates and that the SEA can be considered as a special case of the PEA if only one exponential “piece” is required for the entire range (e.g., the sand).
Soil Changes During Secondary Succession in a Tropical Montane Cloud Forest Area
Authors: Bautista-Cruz Angélica , del Castillo Rafael F.
Published: May 2005

The development of second‐growth forest after abandonment of agricultural fields in tropical montane cloud forest (TMCF) areas is common in southern Mexico, but little is known about how such changes affect soil properties. We evaluated the changes in soil properties at the 0‐ to 20‐ and 20‐ to 40‐cm depths during this conversion in three chronosequences, each composed of a cornfield, and adjacent forests of ≈15, ≈45, ≈75, and ≥ 100 yr after abandonment at El Rincón, Oaxaca, Mexico. All studied soils were acidic, rich in organic C and total nitrogen (TN), and had low levels of plant‐available P, exchangeable Ca, Mg, Na, and K, and high levels of exchangeable Al. Most of the soil properties analyzed changed significantly with the age after abandonment, but in most cases the patterns of response varied with the chronosequence, usually ≈15 to 45 yr after abandonment. In all chronosequences, soil pH and N/P ratio decreased, and the thickness of the O horizon increased, during the first 100 yr of forest development. The highest rates of soil C sequestration and the highest drop in exchangeable K, Mg, and Ca concentrations took place the first 15 yr of forest development. Most of soil changes can be associated with nutrient retention by vegetation and litter, the concentration of exchangeable Al in soil, and the role of soil pH in mineralization rates, ion solubility, and rock weathering. The different patterns of response found among chronosequences illustrate the importance of having replicates before making general statements about changes in soil properties after disturbance.
A National Soil Profile Database for Brazil Available to International Scientists
Authors: Cooper Miguel , Mendes Lúcia Maria Silveira , Silva Wellinton Luiz Costa , Sparovek Gerd
Published: May 2005

A comprehensive digital soil profile database of Brazil was compiled and is being made available through the Internet. Most of the soil data were obtained from the Radambrasil project and other regional surveys. The database contains information from 5086 profiles distributed over the whole Brazilian territory corresponding to data from 10034 horizons, each with 31 variables. The variables were chosen to represent different areas of soil science, embracing soil morphological, chemical, mineralogical, and physical attributes. The distribution uniformity of the data was low with sampling densities varying from one profile per 10000 km2 to one profile per 1370 km2 The access to the database is free and its design allows its use not only by soil scientists but also by those working with agricultural, environmental, and land use issues.
Long‐Term Fertilizer and Water Availability Effects on Cereal Yield and Soil Chemical Properties in Northwest China
Authors: Fan Tinglu , Stewart B. A. , Payne William A. , Yong Wang , Luo Junjie , Gao Yufeng
Published: May 2005

Wheat (Triticum aestivum L.) and corn (Zea mays L.) rotation is important for the region's food security in Northwest China. Grain yield and water‐use efficiency (WUE: grain yield/estimated evapotranspiration [ET]) trends, and changes in soil properties during a 24‐yr rainfed fertilization experiment in Pingliang, Gansu, China, were recorded. Mean wheat yields for the 16 yr ranged from 1.29 Mg ha−1 for the unfertilized plots (CK) to 4.71 Mg ha−1 for the plots that received manure (M) annually with inorganic N and P fertilizers (MNP). Corn yields for the 6 yr averaged 2.29 and 5.61 Mg ha−1 in the same treatments. Yields and WUEs declined with years except for the CK and MNP treatments for wheat. Wheat yields for the N and M treatments declined about 80 kg ha−1 yr−1, compared with about 60 kg ha−1 yr−1 for the NP treatment and the N plus straw treatment receiving P every second year (SNP). Likewise, the corn yields and WUEs declined significantly for all treatments. Grain yield‐ET relationships were linear with slopes ranging from 0.51 to 1.27 kg ha−1 m−3 for wheat and 1.15 to 2.03 kg ha−1m−3 for corn. Soil organic C (SOC), total N (TN), and total P (TP) gradually increased with time except the CK, in which TN and TP remained unchanged but SOC and available P (AP) decreased. Soil AP decreased in the N treatment. Soil available K declined rapidly without straw or manure additions. The greatest SOC increases of about 160 mg kg−1 yr−1 occurred in SNP and MNP treated soils, suggesting that long‐term additions of organic materials could increase water‐holding capacity that, in return, improves water availability to plants and arrests grain yield declines, and sustains productivity.
Sulfur Management for Corn Growth with Conservation Tillage
Authors: Rehm George W.
Published: May 2005

Reduction in soil disturbance associated with conservation tillage planting systems suggests that it is important to evaluate management practices for use of S for corn (Zea mays L.) grown in these planting situations. Evaluation of source, placement, and rate of S applied has not been the focus of past research. In this study, two S fertilizers [21‐0‐0‐24 (ammonium sulfate), 12‐0‐0‐26 (ammonium thiosulfate)] were applied at rates to supply 0, 6.7, 13.4, and 20.1 kg S ha−1 either in contact with the seed at planting or in a band near the seed at planting. Soil texture varied from loamy fine sand to silty clay loam at the experimental sites. Corn emergence was reduced when 12‐0‐0‐26 was placed in contact with the seed at sites with a loamy fine sand and sandy loam texture and soil was dry at time of planting. Stand reduction was most severe when 12‐0‐0‐26 fluid material was used at rates to supply 13.4 and 20.1 kg S ha−1 Placement maintaining soil between seed and fertilizer had no negative effect on emergence. When placed in a band near the seed, both S sources had an equal effect on yield. Reduction in emergence due to 12‐0‐0‐26 in contact with the seed had a negative effect on grain yield. Application of fertilizer S increased yield at all sites except where the texture was a silty clay loam. Optimum rate of fertilizer S was either 6.7 or 13.4 kg S ha−1 and varied with site. The response to fertilizer S on the silt loam soil suggests that inadequate S is released from soil organic matter via mineralization in conservation tillage planting systems.
Soil Change, Soil Survey, and Natural Resources Decision Making
Authors: Tugel A. J. , Herrick J. E. , Brown J. R. , Mausbach M. J. , Puckett W. , Hipple K.
Published: May 2005

Land managers and policymakers need information about soil change caused by anthropogenic and non‐anthropogenic factors to predict the effects of management on soil function, compare alternatives, and make decisions. Current knowledge of how soils change is not well synthesized and existing soil surveys include only limited information on the dynamic nature of soils. Providing information about causes and attributes of soil change and the effects of soil change on soil function over the human time scale (centuries, decades, or less) should be a primary objective of 21st century soil survey. Soil change is temporal variation in soil across various time scales at a specific location. Attributes of change include state variables (dynamic soil properties), reversibility, drivers, trends, rates, and pathways and functional interpretations include resistance, resilience, and early warning indicators. Iterative elements of the blueprint for action described in this article are: (i) identify user needs; (ii) conduct interdisciplinary research and long‐term studies; (iii) develop an organizing framework that relates data, processes, and soil function; (iv) select and prioritize soil change data and information requirements; (v) develop procedures for data collection and interpretation; and (vi) design an integrated soil–ecosystem–management information system. Selection of dynamic soil properties, soil change attributes, and functional interpretations to be included in future soil surveys should be based on analyses comparing the benefits of meeting user needs to the costs of data acquisition and delivery. Implementation of the blueprint requires increased collaboration among National Cooperative Soil Survey partners and other research disciplines.