bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen Dynamics of Grain Legume–Weedy Fallow–Flooded Rice Sequences in the Tropics
Authors: George Thomas , Ladha Jagdish K. , Garrity Dennis P. , Torres Rolando O.
Published: July 2010

Dry‐season (DS) grain legume‐weedy fallow‐wet‐season (WS) flooded rice is a common cropping sequence in the rainfed lowlands of tropical Asia. To better manage N in this cropping system, we need to understand N dynamics and balances as influenced by the aerobic‐anaerobic soil aeration sequence, legume cropping, biological N2 fixation (BNF), and recycling of legume residues. To understand N dynamics under a range of N derived from BNF (15N‐estimated), harvested in pods and left in residues, we conducted a 2‐yr experiment on a Philippine Alfisol using cowpea [Vigna unguiculata (L.) Walp.], mungbean [V. radiata (L.) Wilcz.], nodulating and nonnodulating soybean [Glycine max (L.) Merr.], and weeds. The main portion of soil mineral N (0 to 60 cm) was NO3 in the dry season and NH4 in the wet season. The sum of soil NO3 and soil N uptake at legume harvest exceeded the decrease in soil NO3 from legume seeding to harvest by 81 kg ha−1, indicating the continued production and legume uptake of soil NO3. The large differences in total N of legumes (46 to 238 kg N ha−1), however, were associated with differences in N derived from BNF (0 to 176 kg N ha−1). When pod N was excluded, legume N balance was, in most cases, negative. The average soil N depletion was 40 kg ha−1 from nonnodulating soybean, compared with 8 kg ha−1 from N2‐fixing legumes. In terms of WS rice grain and N yields, legume cropping did not differ from weedy fallowing, despite greater (by up to 46 kg N ha−1) quantities of legume residue N in some instances. Large amounts of legume residues, however, were associated with reduced legume grain yields, thus decreasing the harvestable grain N output. Fertilizer N, compared with residue N, had a greater effect on WS rice grain and N yields. The use of legumes in lowland rice‐based cropping systems must maximize harvestable N while effectively using soil, BNF, and applied N sources.
Fractal Description of Temporal Yield Variability of 10 Crops in the United States
Authors: Eghball Bahman , Power James F.
Published: July 2010

Fractal analysis has been used to characterize both temporal and spatial variability in plant and soil parameters. A plant parameter of prime concern is crop yield. Consequently, the temporal variability of 10 crops commonly grown in the USA was described using fractal analysis. Average yields of nine grain crops along with fiber yield of cotton (Gossypium hirsutum L.) from 1930 to 1990 in the USA were used for semivariogram and fractal analyses. Semivariance was calculated for each crop for different year intervals (h). The slope of the regression line of log semivariance vs. log h for each crop was used to calculate fractal dimension [D = (4 — slope)/2], which is an indication of the pattern of yield variability. A small D‐value (near 1) indicates the dominance of long‐term variation, while a large D‐value (near 2) indicates dominance of short‐term variation and nondominance or lack of long‐term variation or trend. From 1930 to 1990, yield of all crops increased, ranging from about twofold in soybean [Glycine max (L.) Merr.], oat (Avena sativa L.), and barley (Hordeum vulgare L.) to about sixfold in maize (Zea mays L.). Crop improvement through plant breeding and the use of fertilizers and pesticides are presumably the main reasons for increased yield. Large yield differences were observed after 1960 for most of the crops studied, suggesting that risk resulting from year‐to‐year yield differences increased with improved yields. Fractal dimensions ranged from 1.20 to 1.47 for the crops studied, identifying long‐term trend as well as short‐term variation in yield of these crops. Rice (Oryza sativa L.) had the smallest D‐value, indicating that this crop had the least short‐term variation, while oat and soybean had the largest D, indicating greatest short‐term variation. Temporal variability in average crop yield in the USA was much smaller than typical spatial variability values reported by others for soil parameters. It appears that fractal analysis is useful in quantifying temporal variability in yield of various crops and can be applied to agronomic research to characterize temporal variations.
Surface Runoff, Uniformity of Water Distribution, and Yield of Peanut Irrigated with a Moving Sprinkler System
Authors: Ben‐Hur M. , Plaut Z. , Levy G. J. , Agassi M. , Shaiberg I.
Published: July 2010

Influence of water application uniformity of irrigation systems on crop yield has been well documented, but effects of runoff on water distribution in a field and on yield have been less studied. The objective was to determine the effect of runoff on water distribution and peanut (Arachis hypogaea L.) yield in a field irrigated with a lateral moving sprinkler irrigation system (MSIS). The experimental field with silt loam soil (300 by 120 m; 3% slope) was located in the Negev, Israel. The treatments were: (i) microbasins along furrows, where runoff was trapped by the microbasins and penetrated into the soil later, and (ii) the control, where runoff was allowed to move downhill. In each treatment, pod and canopy yields and soil water content were measured at different sites along the slope. Surface runoff from 3−m2 plots in the control treatment was low at the beginning of the growing season and increased to an average of 37.5% in later irrigations. The microbasins increased the uniformity of soil water content along the slope. In control plots, soil water content was higher downhill than uphill because of runoff. Pod and canopy yields in the microbasin treatment were fairly uniform along the slope (CV of 1.3 and 2.8%, respectively). In contrast, pod and canopy yields increased in the downhill direction in control plots (CV of 8.6 and 15.5%, respectively). Preventing runoff improved the distribution uniformity of available water in the field, and increased average pod yield by 880 kg ha−1.
Allelopathic Influence of Nine Forage Grass Extracts on Germination and Seedling Growth of Alfalfa
Authors: Chung Ill‐Min , Miller Darrell A.
Published: July 2010

Poor establishment of alfalfa (Medicago sativa L.) often results when the alfalfa is sown with cool‐season perennial grasses. This study was conducted to screen the inhibitory characteristics of grasses that are often grown in combination with alfalfa in grass swards. Laboratory and greenhouse studies were conducted to determine the allelopathic potential of nine grasses to alfalfa germination and seedling growth. Alfalfa seeds were germinated in aqueous extracts of nine grasses, using distilled water as a control. Measurements were taken to determine the effect of the extracts on germination, seedling length, and weight. Alfalfa germination ranged from 64% for tall fescue (Festuca arundinacea Schreb.) extracts to 91% for the control. Total alfalfa seedling length was reduced by 39% for grain sorghum [Sorghum bicolor (L.) Moench] extracts. Dry weights of alfalfa cotyledons, hypocotyls, and radicles were reduced significantly by several grass extracts. Smooth bromegrass (Bromus inermis Leyss.), orchardgrass (Dactylis glomerata L.), and grain sorghum extracts were more inhibitory than other grass extracts. Alfalfa seedling emergence and survival percentage was affected by various grass root residues. Timothy (Phleum pratense L.) extracts caused the lowest survival percentage of 59% compared to the control of 88%. Redtop [Agrostis gigantea Roth; syn. Agrostis alba L. sensu auct. (American)] and reed canarygrass (Phalaris arundinacea L.) extracts had no effect on alfalfa seedling emergence and survival. Leached and nonleached residues significantly inhibited alfalfa height, leaf area, and dry weights of leaves and stems. The extent of reduction was greater in nonleached than in leached residues. These results suggest that grass residues may affect alfalfa growth and development because of inhibitory effects of allelochemicals present in grass residues.
Yield and Nitrogen Use Efficiency of Irrigated Corn in the Northern Great Plains
Authors: Wienhold Brian J. , Trooien Todd P. , Reichman George A.
Published: July 2010

Nitrogen and water are the two most common limitations to crop production in the semiarid northern Great Plains. Little is known about N use efficiency by irrigated corn (Zea mays L.) in this region. A study was conducted to determine how irrigation and N fertility levels affect growth and N use efficiency by corn. Corn was grown under three irrigation levels: precipitation plus irrigation equal to one, two, and three times the calculated evapotranspiration (ET) rate. Fertilizer use efficiency was determined using 15N‐enriched fertilizer applied at rates equivalent to 100 and 200 kg N ha−1. Grain and dry matter yields, N content, and utilization of fertilizer N all exhibited yearly variations, probably the result of annual weather patterns, especially temperature. For years when temperatures during the growing season were below the 30‐yr average and affected corn growth, there were no differences in yields and N content between the two fertility levels. For years when temperatures during the growing season were warm enough for favorable growth, corn responded to increasing N fertility with 60% greater yields, 75% greater N content, and 60% greater percentage N derived from fertilizer with the higher N fertility treatment. Averaged across rates, grain utilized 35% and stover an additional 15% of the applied fertilizer, while 30% remained in the upper 0.6 m of the soil profile at the end of the growing season. Twenty percent of the applied fertilizer could not be accounted for, lost to leaching or denitrification. Supplemental irrigation and N fertilization are viable management practices available to producers in the semiarid northern Great Plains.
A Classification System for Factors Affecting Crop Response to Nitrogen Fertilization
Authors: Lory John A. , Russelle Michael P. , Randall Gyles W.
Published: July 2010

Crop response to N fertilizer (Nf) is influenced by factors such as Nf management, soil type, crop sequence, and supply of residual and mineralized N, but there is no framework to define the best strategy to account for a given factor in an Nf recommendation. This paper describes a three‐component classification system for evaluating the effect of any factor on yield response to Nf. This system provides (i) a vocabulary to describe clearly the effect of a factor on Nf recommendations, and (ii) insight on how to adjust Nf recommendations for the effect. Factors that affect yield response to Nf but not to N supply (Ns) were classified as shift effects (i.e., movement of a response curve in the x and/or y direction, with no change in coefficients of curvature). Factors that interact with Nf and Ns response were classified as interaction effects. Nitrogen supply was defined as the sum of aboveground plant N content of the control (0 N applied) plot, postharvest fall NO‐3 in the surface 1.5 m of the control plot, and Nf applied. Two 2‐yr experiments were conducted at Rosemount and Waseca, MN, to compare Nf response of continuous corn (Zea mays L.) with that of first‐ and then second‐year corn following alfalfa (Medicago sativa L.). We used the classification system to evaluate effects of crop sequence, year, and location on corn yield response to Nf. Year and crop sequence effects at Rosemount were primarily shift effects, implying that quantifying the effect on Ns would be sufficient to account for these effects on Nf recommendations. In contrast, the interaction model predominated at Waseca. Consequently, at this location simple adjustments of Ns were not sufficient to account for the complexity of crop sequence effects on Nf recommendations. This classification system facilitates the organization, evaluation, and communication of the many factors that influence crop yield.
Morphological Development of Switchgrass in Diverse Environments
Authors: Sanderson Matt A. , Wolf Dale D.
Published: July 2010

Switchgrass (Panicum virgatum L.) has been proposed as a model species for biomass fuel production. To better manage switchgrass as a biofuel crop, knowledge of its morphological development in several environments would be useful. This study was conducted to determine how morphological development of switchgrass varies in different field environments and to relate development to soil moisture status and other meteorological indicators. An established stand of ‘Alamo’ switchgrass at Stephenville, TX (32°13' N, 98°12' W; 399 m elevation), was sampled weekly or biweekly from April to September in 1991 and 1992. Field plots of Alamo and ‘Cave‐in‐Rock’ were established at Stephenville in 1992 and sampled 17 times during 1993. Established field plots of Alamo and Cave‐in‐Rock at Blacksburg, VA (37°11' N, 80°25' W; 610 m elevation) were sampled at 11 dates in 1992 and 9 dates in 1993 from May to September. Maturity stage at each harvest was determined according to a maturity scale developed at Stephenville. Morphological development and apical meristem elevation of both cultivars were closely related to cumulative degree days (DD, base 10°C) at each location. The developmental patterns were similar among years and were not affected by differences in soil moisture or rainfall distribution at Stephenville. Cave‐in‐Rock and Alamo matured about 4 wk earlier at Stephenville than at Blacksburg. The duration of the vegetative period was about 300 DD shorter at Blacksburg than at Stephenville for both Alamo and Cave‐in‐Rock. The close association of morphological development with DD in different environments could simplify morphological development models; however, the models would need to be location specific, because the timing and duration of phenological events differed as switchgrass cultivars were moved southward or northward.
Natural Herbicide Potential of Alfalfa Residue on Selected Weed Species
Authors: Chung Ill‐Ming , Miller Darrell A.
Published: July 2010

Alfalfa (Medicago sativa L.) contains water‐soluble substances that are toxic to itself (autotoxicity) and to other species (allelopathy). Experiments were conducted to determine the potential of using alfalfa residue as a natural herbicide for inhibition of weed seed germination, seedling growth, and development. Various weed species were germinated in aqueous extracts from dried alfalfa using cold (5°C), warm (24°C), and hot (80°C) treatments. Results indicated that inhibition of weed seed germination was dependent on the aqueous extraction method, residue application rate (w/v or w/w), and weed species. The greatest inhibition of germination was 44%, when 60% (w/v) warm aqueous extract was applied to lambsquarters (Chenopodium album L.). Seedling growth was also inhibited by residue application at various rates. Root length was more inhibited than increase in shoot length. In terms of total seedling length, giant foxtail (Setaria faberii Herrm.) was the most resistant species and lambsquarters was the most susceptible among the weed species studied to alfalfa aqueous extracts. Weed seed germination percentage decreased as incubation time increased from 8, 16, 24, and 48 h. An alfalfa aqueous extract incubated for 48 h caused the greatest inhibition of velvetleaf (Abutilon theophrasti Medic.) seed germination (25%). When alfalfa residue was incorporated with silica sand, the growth and development of lambsquarters, pigweed (Amaranthus retroflexus L.), velvetleaf, and crabgrass [Digitaria sanguinalis (L.) Scop.], as measured by plant height, leaf area, and total, shoot, leaf, and root dry weight, were significantly inhibited as the rate increased from 0.0 to 2.0 g kg−1. Dried alfalfa residue significantly stimulated plant height, leaf area, and total dry weight including shoot, leaf, and root of giant foxtail and cheatgrass (Bromus secalinus L.). Results suggest that alfalfa residue has a contrasting effect on weed growth and development due to water‐soluble allelochemicals present in the residue.
Estimation of Soybean Yields at County and State Levels Using GLYCIM: A Case Study for Iowa
Authors: Haskett Jonathan D. , Pachepsky Yakov A. , Acock Basil
Published: July 2010

Global climate change could have a significant impact on important food crops such as soybean [Glycine max (L.) Merr.]. To assess the impact of these environmental changes, estimates of crop yields are needed, with special reference to regional responses in key production areas. The objective of this study was to examine the performance of the GLYCIM soybean crop model in modeling regional soybean yields in Iowa at the state and county level, over a 20‐yr period. The GLYCIM model has been extended to run for multiple years and combined with aggregations of soil and weather data to provide simulation over large areas. Soils data were aggregated to the soil association level in 18 sample counties so as to provide two‐county data sets in each Crop Reporting District (CRD). Weather files for each CRD spanning the period 1972 to 1991 were used to provide current climate information. Simulation runs were made for each year and county. Statewide yields were estimated as an average of county yields. Statistical measures of simulation success indicated that, using aggregated characteristics, the model was best able to simulate the 20‐yr mean yield at the state and county level, as well as long‐term yield variability. Poorer results of modeling yields in particular years were obtained. This validation establishes the model's ability to simulate long‐term yield averages under current conditions, and lays the groundwork for future simulations using altered climate scenarios.
A Weather‐Soil Variable for Estimating Soil Moisture Stress and Corn Yield Probabilities
Authors: Dale Robert F. , Daniels James A.
Published: July 2010

Agricultural technology has increased crop yield potentials, but on rain‐fed crops yields are still severely reduced with the normal climatic frequency of drought. Objectives were (1) to determine an interaction regression of county average corn (Zea mays L.) yield on a soil moisture stress variable and technology trend and (2) to estimate the probability of soil moisture stress and resulting average corn yield in Tippecanoe County, Indiana. The soil moisture stress variable (Sc) was the sum of modeled daily ratios of actual to potential evapotranspiration [Σ(ET/PET)] over critical corn growth and development periods. The interaction regression model of corn yield on Sc andyield on Sc andyield on Sc andyield on Sc and technology trend (T = year) for Tippecanoe County was associated with 70% of the variance in the 1961 to 1992 average county corn yields when Sc was a 90‐d period (S90) from 39 d before corn silking to 50 d after. With no moisture stress (S90 = 90), the technology trend over the last 32 yr was 0.17 t ha−1 yr−1 (2.7 bu acre−1 yr−1). With 1992 technology, each deficit unit of S90 reduced the yield 0.19 t ha−1 (3.1 bu acre−1). The distributions of S90 and predicted corn yield were highly negatively skewed. The probability of having an S90 less than 85 (at least some moisture stress), and a county corn yield less than 9.5 t ha−1 (152 bu acre−1) is 69%, but the probability of severe stress (S90 < 75) and corn yield less than 7.5 ± 0.8 t ha−1 (139 ± 13 bu acre−1) is 22%. For the same weather regime, the probability of moisture stress and resulting corn yields differs greatly for individual soils. For a poorly drained soil (Typic Argiaquoll) the probability of having an S90 less than 85 is 41%, but for a well‐drained soil (Typic Argiudoll) the probability is 90%.
Radiation‐Use Efficiency in Summer Rape
Authors: Morrison Malcolm J. , Stewart Doug W.
Published: July 2010

The radiation‐use efficiency (RUE) is a parameter that represents a crop canopy's ability to convert intercepted solar energy to dry matter. The RUE is used in simulation models and can vary with crop type and environment. The objective was to examine the effects of varying row width and seeding rate on the amount of intercepted photosynthetically active radiation (IPAR) and the RUE in summer rape (Brassica napus L.). ‘Westar’ summer rape was seeded at rates of 1.5, 3.0, 6.0, and 12.0 kg ha−1 in rows spaced 15 or 30 cm apart. Plant sampling was done at key growth stages, and the leaf and pod areas and total plant dry weights were determined. After flowering, plants intercepted more PAR when grown in 15‐cm‐wide rows than 30‐cm‐wide rows. For both row widths, as seeding rate increased from 1.5 to 12.0 kg ha−1, IPAR increased. The RUE was greater for plants grown in 15‐cm‐wide rows than for those grown in 30‐cm rows; however, RUE decreased with increasing seeding rate. The mean RUE value was 2.83 g MJ−1 PAR. When the pod area was added to the leaf area, the IPAR increased and the RUE decreased.
Managing Alfalfa and Berseem Clover for Forage and Plowdown Nitrogen in Barley Rotations
Authors: Westcott M. P. , Welty L. E. , Knox M. L. , Prestbye L. S.
Published: July 2010

Annual legume plowdown systems, which utilize fall regrowth for N contributions to rotational crops, have not been adapted to irrigated, intermountain areas of the Northern Rockies. Our objective was to evaluate plowdown systems using ‘Nitro’ alfalfa (Medicago sativa L.) and ‘Bigbee’ berseem clover (Trifolium alexandrinum L.). These two legumes were grown under five harvest management systems (zero to three forage harvests prior to fall plowdown of regrowth, or a standard three harvest system with no herbage plowdown) at two sites in western MT differing in soil characteristics. They were assayed for forage and plowdown production and for N benefits to ‘Clark’ barley (Hordeum vulgare L.; syn. H. distichon L.) for two subsequent years. Maximum herbage plowdown N was 125 to over 200 kg N ha−1 for berseem clover and 87 kg N ha−1 for alfalfa. A two‐harvest system resulted in 3.6 to 6.6 Mg ha−1 forage and 45 to 78 kg N ha−1 in herbage plowdown. Effects of plowdown were measured directly in increased soil N availability and correlated increases in N uptake in subsequent barley; benefits were expressed in increased grain yields and/or grain N concentrations and were apparent for two successive years at the site of lower native fertility. Alfalfa N benefits were superior to berseem clover, though disproportionate to herbage plowdown N quantities, possibly due to greater root and crown N in alfalfa. Where the management goal is primarily forage production with moderate benefit of plowdown N, berseem clover works well in a two‐harvest system; Nitro alfalfa is preferred where greater benefits of plowdown N are desired.
Cotton Rooting Patterns in Relation to Soil Temperatures and the Thermal Kinetic Window
Authors: Burke John J. , Upchurch Dan R.
Published: July 2010

Throughout the USA, cotton (Gossypium hirsutum L.) is irrigated to avoid the deleterious effects of drought stress on growth and development. Irrigation, while optimizing water status, results in a concomitant cooling of soil temperatures. Previous field studies have focused on soil water status effects on root growth independent of the soil temperature changes following irrigation. This study was designed to evaluate the soil temperature characteristics of irrigated and nonirrigated field plots of cotton to determine the time that temperatures are spatially and temporally within the range for optimal cotton root metabolism. Soil temperatures in the nonirrigated treatment were within cotton's thermal kinetic window (23.5 to 32°C) for 72% more time than in the irrigated treatment. Predicted rooting fronts fell between the 24 and 26°C isotherms in the irrigated treatment and the 26 and 28°C isotherms in the nonirrigated treatment. Greater root length density of cotton in the nonirrigated treatment, determined from soil cores, was associated with increased time at optimal temperatures. Near the soil surface, root length density decreased in the nonirrigated treatment because of reduced soil water status, not because of reduced time within the optimal temperature range. Soil temperatures cooled below the optimal range upon canopy closure in the irrigated treatment. The cooling trend was observed to a lesser extent in the nonirrigated treatments, which never realized full canopy closure. This study showed that greater cotton root development occurred across time and with depth in soils exhibiting temperatures within cotton's thermal kinetic window.
Early Planting of Early‐Maturing Soybean: Effects on Seed Germination and Phomopsis Infection
Authors: TeKrony Dennis M. , Grabau Larry J. , DeLacy M. , Kane M.
Published: July 2010

The use of early‐maturing soybean [Glycine max (L.) Merr.] cultivars has been suggested as a means of avoiding drought stress and extending harvest maturity in the southeastern USA. This experiment determined the effect of cultivar maturity on seed germination and Phomopsis longicolla T.W. Hobbs seed infection following early planting. Six cultivars ranging from Maturity Group (MG) 00 to IV were planted in late April, mid‐May, and early and late June in 1992 and 1993 at Lexington, KY. The May planting was sprayed at weekly intervals between growth stages R5 and R7 with the foliar fungicide benomyl [methyl 1‐(butylcarbamoyl)‐2‐benzimidazolecarbamate] to control seed infection. A single, recommended application of benomyl was also made at growth stage R6 for all planting dates in 1993. Seed was harvested at harvest maturity (HM, defined as the time when seed first dried to <140 g kg−1 moisture) and 3 wk after that date. Higher levels (>30%) of P. longicolla seed infection frequently occurred for the April and May plantings, which often resulted in lower (<85%) seed germination for earlier maturing cultivars. As harvest maturity was delayed due to later planting dates of early‐maturing cultivars (MG 00‐II or the use of full‐season cultivars (MG III, IV), seed quality improved. Weekly benomyl applications to the mid‐May planting reduced seed infection to low levels and increased seed germination to >90% at HM in both years for all cultivars. Thus, high‐quality soybean seed can be produced on early maturing cultivars grown outside the range of adaptation, if seed infection by P. longicolla is controlled. Cultural methods are discussed for reducing seed infection and improving seed quality of early‐maturing cultivars.
Nitrogen Fertilization and Burning Effects on Rumen Protein Degradation and Nutritive Value of Native Grasses
Authors: Cuomo Greg J. , Anderson Bruce E.
Published: July 2010

Nitrogen fertilization and burning can affect crude protein (CP) concentration of warm‐season grasses. While total CP concentration in these forages may limit animal performance, the amount of protein degraded in the rumen may be equally important. A 2‐yr study was undertaken to determine the effect of N fertilization and burning on protein degradation and quality components of three warm‐season grasses. Monocultures of switchgrass (Panicum virgatum L.), big bluestem (Andropogon gerardii Vitman), and indiangrass [Sorghastrum nutans (L.) Nash] were either burned in mid‐April or left unburned. One half of each burn treatment was either fertilized with 66 kg ha−1 of N or not fertilized. Plots were harvested in mid‐June and again in mid‐July of 1990 and 1991. Crude protein, rumen degradable protein (RDP), in situ organic matter disappearance, neutral‐detergent fiber (NDF), acid‐detergent fiber (ADF), and acid‐detergent lignin (ADL) were determined. Nitrogen fertilization increased (P < 0.01) CP concentration 18%. Sixty‐five percent of the additional CP associated with N fertilization was RDP. The percentage of CP that was RDP was greater in switchgrass and indiangrass than big bluestem in both years. Even though burning increased early‐season CP concentration 7%, it did not affect the RDP percentage. Increased CP levels, particularly RDP, indicate that rumen undegradable protein (RUP) would be a more appropriate supplement with N fertilized switchgrass and indiangrass, while supplementation with RDP would be more appropriate with big bluestem and forages from burned sites.
Rhizoma Peanut and Alfalfa Productivity and Nutrient Composition in Central Georgia
Authors: Terrill Thomas H. , Gelaye Seyoum , Mahotiere Sauveur , Amoah Eugene A. , Miller Schauston , Gates Roger N. , Windham William R.
Published: July 2010

Limits of environmental adaptation of ‘Florigraze’ rhizoma peanut (Arachis glabrata Benth.), a high‐quality perennial warm‐season legume, have not been well defined. A field experiment compared yield and nutritive value of rhizoma peanut and alfalfa (Medicago sativa L.) in central Georgia on a Norfolk soil (fine‐loamy, siliceous, thermic Typic Kandiudults). Crude protein (CP), neutral‐detergent fiber (NDF), aciddetergent fiber (ADF), lignin, Ca, Mg, and P of total herbage, and dry matter (DM) yield and in vitro organic matter disappearance (IVOMD) of total herbage, leaf, and stem tissues were determined for three growing seasons. Annual DM yield of peanut and alfalfa averaged 7.6 and 11.8 Mg ha−1, respectively. In the first 2 yr, alfalfa outyielded rhizoma peanut, but there was no difference in yield in the third year. Leaf DM yield was higher for peanut than for alfalfa in the third year. Rhizoma peanut DM production occurred predominately during late summer and early autumn vs. spring for alfalfa. Rhizoma peanut total herbage DM was lower in CP and higher in Ca and Mg than that of alfalfa, but IVOMD was similar. Leaf IVOMD was higher for alfalfa than for rhizoma peanut, but IVOMD of peanut stems was equal to or higher than alfalfa stems. Rhizoma peanut has potential for central Georgia and other areas of the southern USA with a similar climate.
Soil‐Water and Root Dynamics under Hedgerow Intercropping in Semiarid Kenya
Authors: Govindarajan Muthiah , Rao Meka R. , Mathuva Moses N. , Nair P. K. Ramachandran
Published: July 2010

Competition for growth resources between woody and crop species is said to be the main reason for failure of hedgerow intercropping (alleycropping) in semiarid tropics, but the mechanisms of competition are not clearly understood. In this study, conducted in the semiarid highlands of Kenya, soil‐water changes and root dynamics were monitored during two rainy seasons from a long‐term, replicated, alleycropping experiment. The treatments were (i) maize (Zea mays L.) grown alone, without fertilizer; (ii) maize, without fertilizer, intercropped between hedgerows of leucaena [Leucaena leucocephala (Lam.) de Wit], with hedgerow prunings returned to the alleys; and (iii) maize grown alone, with fertilizer at 40 kg N and 18 kg P ha−1. Available water in 1.25 m of soil depth under alleycropping was lower than with maize alone. Depletion of soil water by hedgerows continued after maize harvest and carried water deficits in alleycropping from one season to the next. Leucaena provided 1.45 Mg ha−1 leaf biomass, which contained 41.6 kg N and 2.5 kg P ha−1; moreover, it added 0.51 Mg ha−1 season−1 of root biomass to the soil, equivalent to 7 kg N and 0.2 kg P ha−1. Therefore, N contributed through the alleycropping system was equivalent to the recommended fertilizer level; the system, however, did not meet the P requirements of the crop. Maize did not respond to fertilizer in both seasons, and the alleycropped maize yielded lower than the unfertilized maize. Our study indicates that under water‐limiting conditions, alleycropping is detrimental to crop yields because competition of trees with crops for water outweighs the likely soil‐fertility benefits.
Nitrate Dynamics Following Brush Control in a Post Oak‐Blackjack Oak Forest
Authors: Gay David L. , Allen Earl R. , Engle David M. , Stritzke Jimmy F.
Published: July 2010

Converting marginal hardwood forests to grass may increase economic output from livestock production. Nitrogen dynamics during conversion need to be evaluated to determine if conversion releases excessive quantities of NO3‐N, with potential adverse effects on the environment. This study was conducted to determine the amount of NO3‐N present during conversion of a mature post oak‐blackjack oak (Quercus stellata Wangenh.‐Q. marilandica Muenchh.) forest and to identify optimum time periods for grass uptake of available mineralized N after herbicide treatment. Four treatments were evaluated: (i) no brush kill with no grass overseeding, (ii) brush kill with no grass overseeding, (iii) brush kill with cool‐season grass overseeding, and (iv) brush kill with warm‐season grass overseeding. The cool‐ ‘K‐31’ tall fescue (Festuca arundinacea Schreb.); ‘Plains’ Old World bluestem [Bothriochloa ischaemum var. ischaemum (L.) Keng] was the warm‐season(C4) grass. Soil profile NO3‐N to a depth of 60 cm and NO3‐N concentrations in soil leachate at 60 cm were measured in 15‐ by 25‐m plots during a 22‐mo period (June 1993 to March 1995). Soil NO3‐N increased from ì5 kg ha−1 initially to >50 kg ha−1 when brush was killed with tebuthiuron [N‐[5‐(1,1‐dimethylethyl)‐1,3,4‐thiadiazoi‐2‐yl]‐N,,N′‐dimethylurea] application. Soil and leachate NO3‐N in tall fescue overseeded plots returned to near pretreatment levels by the end of the first rapid growth phase of tall fescue in June 1994. Soil NO3‐N in Old World bluestem overseeded and unseeded brush kill plots remained elevated throughout the experiment, and leachate NO3‐N concentrations rose from 0 to more than 70 mg L−1 The risk of NO3‐N leaching after brush control is reduced by overseeding with tall fescue.
Comparisons between an Upland and a Pima Cotton Cultivar: II. Nutrient Uptake and Partitioning
Authors: Unruh Bryan L. , Silvertooth Jeffrey C.
Published: July 2010

Uptake and partitioning of N, P, and K by Upland cotton (Gossypium hirsutum L.) have been studied, but no such work has included American Pima cotton (G. barbadense L.). Our objective was to describe the N, P, and K uptake and partitioning into various plant parts for two representative Upland and Pima cotton cultivars. Upland ‘Deltapine 90’ (DPL 90) and Pima ‘S‐6’ were grown at two south‐central Arizona locations for 3 yr. Beginning 14 to 20 d after emergence, the aboveground portions of cotton plants were harvested and separated into stems, leaves (including petioles), burs (carpel walls), lint, and seeds. The bur fraction also included squares, flowers, immature bolls, and burs from mature bolls. Total N, P, and K analyses were conducted on each fraction (except lint). Nutrient concentration, uptake, and partitioning by cotton was modeled on a heat unit accumulation basis (HUAP). Up to about 1500 HUAP, leaves were major N sinks, leaves and the bur fraction were major P sinks, and leaves and stems were major K sinks for both cultivars. After 1500 HUAP, the bur fraction and seeds were major N and P sinks and the bur fraction was the major K sink. For DPL 90, the total N, P, and K uptake was 201, 31, and 254 kg ha−1 and for Pima S‐6, it was 201, 32, and 226 kg ha−1, respectively. Nutrient requirements for producing 100 kg lint ha−1 were 15‐2.3‐19 kg ha−1 N‐P‐K for Upland cotton and 21‐3.3‐23 kg ha−1 for Pima cotton.
Instantaneous Measurement of Radiation and Water Use Efficiencies of a Maize Crop
Authors: Rochette Philippe , Desjardins Raymond L. , Pattey Elizabeth , Lessard Robert
Published: July 2010

Field‐scale measurement of CO2 flux between vegetation and the atmosphere is a direct way to quantify short‐term performance of an agricultural crop through the growing season. This study measured CO2 and H2O exchange in a maize (Zea mays L.) field during a growing season, in order to (i) estimate crop net photosynthesis (Pn) and canopy nighttime respiration and (ii) calculate crop radiation and water use efficiencies. Maize net photosynthesis was calculated for 850 h (day) and canopy respiration for 175 h (night) from measurements of CO2 fluxes above the crop and estimates of CO2 fluxes at the soil surface. Under high radiation, Pn reached 2 mg m−2 s−1 at 30 d after emergence, remained between 2 and 2.5 mg m−2 s−1 for the next 30 d, and then slowly decreased until first frost. Two negative exponential equations were proposed to describe the relationship between Pn and intercepted photosynthetically active radiation (IPAR) during the growing season: one from planting to maximum leaf area index (LAImax) and one from LAImax to the first fall frost. These results confirmed that, in absence of water stress and with adequate fertilization, simple models based on IPAR could account for about 90% of the variation in Pn. The higher efficiency of diffuse than of direct beam radiation was documented. Instantaneous radiation use efficiency (IRUE) was shown to decrease by 66% from cloudy to clear sky conditions, so it is desirable to incorporate IRUE for estimation of short‐term (hourly) Pn. Canopy respiration rates at night ranged from 0.1 to 0.2 mg m−2 s−1 for LAI between 1 and 3, or about 10% of daily photosynthesis. The relationship between Pn and water vapor flux (Fq,a) was nonlinear, with slope decreasing with increasing Fq,a. Water use efficiency at LAImax was 17 mg g−1 for Fq.a = 0.05 g m−2 s−1 and about 10 mg g−1 for Fq,a = 0.20 g m−2 s−1. Direct evaporation of water from the soil surface (at low LAI) or from wet plant parts resulted in considerable noise in the Pn ‐ Fq,a relationship. The normalization of Fq,a by the vapor pressure deficit (VPD) linearized the relationship. The slope of the Pn ‐ Fq,a/VPD curve was larger for cloudy than for clear sky conditions, probably as a result of the larger RUE under diffuse radiation.
Determining Cotton Water Use in a Semiarid Climate with the GOSSYM Cotton Simulation Model
Authors: Staggenborg Scott A. , Lascano Robert J. , Krieg Daniel R.
Published: July 2010

Simulation models are useful tools that provide information about potential changes to production systems before committing time and resources. GOSSYM, a physiologically based cotton (Gossypium hirsutum L.) simulation model, was developed as an experimental tool but has been modified and adapted as a crop management tool. For GOSSYM to be used successfully in crop management, especially as an irrigation scheduling predictor, its ability to accurately calculate and partition total water use between transpiration (T) and soil water evaporation (E) must be evaluated. A field study with cotton was conducted at Lubbock, TX, in 1994 in an Olton soil (fine, mixed, thermic Aridic Paleustoll) to compare GOSSYM's calculations of E, T, and evapotranspiration (ET = E + T) with values measured by neutron attenuation, microlysimetry, and stem flow gauges. During a 12‐d period when E and T were measured separately, GOSSYM underestimated cumulative E by 18%, while cumulative T was in close agreement with measured values. Underestimation of E was due to overestimation of leaf area index (LAI), thus reducing simulated incident irradiance at the soil surface. A comparison of calculated and measured values of daily T over 60 d showed that calculated daily T's were 40% greater than measured values during the initial 10 d, 50% less during the last 10 d, and in close agreement in between. Differences between calculated and measured daily T‐values were attributed to GOSSYM underestimating potential ET and overestimating LAI. However, ET over 102 d was calculated within 10% at the end of the measuring period. These data suggest that GOSSYM can be used to assess water use in cotton, and as a tool for scheduling irrigations in a semiarid region, provided that current algorithms used to calculate potential ET are modified to include air humidity.
Fertilizer Nitrogen Recovery in a No‐Till Wheat–Sorghum–Fallow–Wheat Sequence
Authors: Porter Lynn K. , Follett Ronald F. , Halvorson Aedell D.
Published: July 2010

No‐till cropping in the semiarid Central Great Plains increases water storage during fallowing, which allows farmers to use an intensive cropping sequence of winter wheat (Triticum aestivum L.)‐sorghum [Sorghum bicolor (L.) Moench]‐fallow‐winter wheat. The purpose of this 15N field study was to provide as complete accounting as possible of fertilizer N dynamics (changes in the NO3−N pool, fertilizer N uptake by plants, fertilizer N carryover effects, and mineralization and uptake of labeled N from wheat residues) for this intensive cropping sequence. Main‐plot treatments were 0, 56, and 112 kg N ha−1. Eight microplots were established within all main plots. For the main plots that received 56 and 112 kg N ha−1, two microplots received no K15NO3, and one of these microplots had its nonlabeled wheat residues exchanged with labeled residues. Six microplots were treated with K15NO3, one‐third received K15NO3 the first year, one‐third the second year, and one‐third both years. There was no detectable NO3 leaching. Mineralization, fertilizer application, and plant uptake had dramatic effects on the soil NO3−N pool. Both N rates increased the total N concentration and N uptake of aboveground biomass of the first wheat crop and the sorghum crop over the unamended treatment, whereas only the highest fertilizer N rate increased the total N uptake of the unfertilized second wheat crop. Plant N uptake transferred the majority of fertilizer NO3 to aboveground biomass, and crop residue deposition, immobilization, and mineralization maintained the fertilizer N in the top 60 cm of soil. At the end of the 4‐yr cropping sequence, 90 and 87% of the applied fertilizer N was accounted for at the 56 and 112 kg N ha−1 rates, respectively. Of this N, generally 24 to 28% remained in the soil. The 10 to 13% of the applied fertilizer N that was unaccounted for was probably lost by denitrification or NH3 volatilization.
Decomposition and Nutrient Release Dynamics of Two Tropical Legume Cover Crops
Authors: Luna‐Orea Pedro , Wagger Michael G. , Gumpertz Marcia L.
Published: July 2010

Shifting agriculture is a main contributor to deforestation in the humid tropics. Substitution of managed fallows using cover crops is a possible alternative to natural fallow that may contribute to more sustainable farming systems via more efficient nutrient cycling. Our objective was to determine the rate of decomposition and nutrient (N, P, K, Ca, Mg) release patterns resulting from two managed fallow periods (12 or 18 mo) for Desmodium adscendens (Sw.) DC. (syn. D. ovalifolium Guillemin & Perrottet) and Pueraria phaseoloides (Roxb.) Benth. (tropical kudzu) grown on Typic and Aquic Dystropept soils at two locations in the Bolivian Amazon. Dry matter disappearance and nutrient release rates from decomposing cover crop residues were monitored using 1‐mm mesh nylon bags. The longer managed fallow (18 mo) reduced the decomposition rate of both cover crops. After 30 wk, residues remaining from 12‐mo managed fallows averaged 24% for desmodium and 16% for pueraria, whereas residues from 18‐mo managed fallows averaged 53% for desmodium and 32% for pueraria. Similar to dry matter disappearance, cover crops grown for 12 mo released nutrients faster than those grown for 18 mo. Nutrient release patterns between sites were similar. By 30 wk, nutrient percentages remaining in desmodium vs. pueraria grown for 12 mo at Site 1 were 46 vs. 17% N, 17 vs. 9% P, 4 vs. 2% K, 36 vs. 20% Ca, and 30 vs. 21% Mg. Similar proportional differences in release patterns were observed for all nutrients except Ca for 18‐mo managed fallows. These results indicate a greater potential for asynchrony between crop nutrient demand and cover crop residue nutrient release for 12‐ vs. 18‐mo managed fallows, and more so for pueraria than desmodium.
Accumulation and Redistribution of Mineral Elements in Common Vetch during Pod Filling
Authors: Caballero Rafael , Arauzo M. , Hernaiz P. J.
Published: July 2010

Common vetch (Vicia sativa L.) is an annual legume used for hay and grain. Field studies were conducted during two growing seasons (1991–1992 and 1992–1993) in a Mediterranean continental area of central Spain with the objectives of determining optimum harvest maturities for mineral composition and redistribution patterns of nutrient elements during seed‐filling. Maturity stages were defined as progressively higher DM concentration in the seed (full bloom and 200‐250, 250–300, 350–450, 450–550, 600–700, 700–800, and >800 g kg−1 seed DM). Concentrations of most mineral nutrients showed a decreasing trend with advancing maturity. Maximum accumulation of N, P, Cu, and Zn was reached at the end of the period of rapid seed growth (450–550 g kg−1 seed DM). These elements showed the greatest mobilization from vegetative structures, but did not supply the total needs for seed development during the phase of rapid seed growth. Potassium, Ca, and Mn showed the lowest level of remobilization to the seed, with maximum accumulation at the beginning of seed formation (200–250 g kg−1 seed DM). In this case, remobilization oversupplied the seed needs. When harvested for hay at the 450–550 g kg−1 seed DM, common vetch can return 30% of accumulated K, Ca, and Mn to the soil in unharvested biomass. If harvested for grain at maturity (>800 g kg−1 seed DM), only 30 to 40% of accumulated N, P, Cu, and Zn remained in the crop residue; however, 75 to 95% of accumulated K, Ca, Mg, Fe, and Mn remained. Both individual mineral nutrients accumulation‐redistribution patterns and diverse uses of the aerial biomass must be considered in assessing common vetch mineral nutrient needs.
Canola Root Rot and Yield Response to Liming and Tillage
Authors: Arshad M. A. , Gill K. S. , Turkington T. K. , Woods D. L.
Published: July 2010

No‐till is replacing conventional tillage in many areas, but information regarding tillage effects on crop, soil, and weed response to liming of acid soils is needed for canola (Brassica campestris L.) production. A Hythe clay loam (fine, montmorillonitic, frigid Mollic Cryoboralf) with initial pH in CaCl2 ≈ 5 was limed (7.5 Mg ha−1) in May 1991. Liming increased soil pH to 6.6 in the fall of 1991. During 1993 to 1995, the pH of limed soil at the 0‐ to 10‐cm depth ranged from 6.2 to 6.3 when conventionally tilled and from 5.6 to 6.2 under no‐till. A slight increase at the 10‐ to 20‐cm depth and no change below 20 cm occurred in soil pH due to liming. Liming increased NO3‐N in the 0‐ to 20‐cm depth significantly, but no change was detected in exchangeable Al, NH4‐N and extractable P. Weed populations were not affected by liming in 1993 and 1994, but were suppressed markedly in 1995. Liming reduced brown girdling root rot (BGRR) (caused by Rhizoctonia solani Kühn) and increased grain yield of canola. Three‐year mean BGRR ratings (a scale of 0 to 5 scale, from disease‐free to disease‐impaired) under no lime and lime, respectively, were 2.96 and 2.59 in tilled and 2.76 and 2.63 in no‐till soil. The increase in canola grain yield by liming was 0.39 (37%) Mg ha−1 yr−1 in tilled and 0.22 (17%) Mg ha−1 yr−1 in no‐till soil. Liming increased dry matter by 1.77 Mg ha−1 yr−1 (31%). No‐till plots had higher soil water and canola yields but slightly lower soil pH (0‐ to 20‐cm depth), and lesser BGRR, compared with the tilled system. Increased soil NO3‐N and pH, fewer weeds, and reduced BGRR‐all responded to liming and contributed to increased canola yields under both tilled and no‐till systems.