bluuebunny/crossref_metadata_2025 huggingface dataset:
Dry Matter, Nitrogen, Phosphorus, and Potassium Accumulation by Four Cotton Varieties
Authors: Mullins G.L. , Burmester C.H.
Published: July 2010

Since the mid‐1940s, varieties and cultural practices have changed for cotton (Gossypium hirsutum L.) grown in the southeastern USA. We believed a more current investigation of dry matter production rates and nutrient uptake patterns was needed for representative cotton cultivars. Field studies were conducted to determine if dry matter production and distribution, and nutrient uptake and distribution are affected by the cultivar of cotton grown under nonirrigated conditions. Four cotton cultivars were compared: Deltapine 90, Stoneville 825, Coker 315, and Paymaster 145. The experiment was conducted on a nonirrigated Decatur silt loam (clayey, thermic, kaolinitic Rhodic Paleudults) and a Norfolk silt loam (fine loamy, thermic siliceous Typic Paleudults). Soil fertility was uniform within a given site. Intact cotton plants were harvested at 14‐d intervals throughout the growing season starting at 15 d after emergence, and separated into leaves, stems, burs, seed, and lint. Total dry matter production averaged 7923 kg ha−1 in 1986 and 7695 kg ha−1 in 1987 on the Decatur soil, and 6726 kg ha−1 on the Norfolk soil in 1986. The four cultivars produced and partitioned dry matter similarly within a location. Differences between locations (soils) were not related to a difference in cumulative heat units. Total N, P and K uptake averaged 128, 17.3 and 106 kg ha−1, respectively. Cotton plants from the study removed an average of 19.9 kg N, 2.5 kg P and 15.3 kg K for every 100 kg lint. Nutrient concentrations and nutrient uptake by a plant part, and total nutrient uptake were not affected by the cotton variety.
Sugarbeet Response to Nitrogen as Affected by Seasonal Irrigation
Authors: Winter S. R.
Published: July 2010

Sugarbeet (Beta vulgaris L.) responses to irrigation (I) and N have been documented but I by N interactions are less well understood. The objective was to determine if N response is dependent on the amount of seasonal irrigation. Sugarbeet root yield, fresh weight sucrose concentration, and impurities were measured in experiments involving four N rates within three irrigation levels during 1982, 1984, 1986, and 1987 on a slowly permeable Pullman clay loam (fine, mixed, thermic Torrertic Paleustoll). Irrigation by N interactions were not significant in 1982 and 1984 when residual NO3–N was an important N source. Significant I by N interactions for all yield and quality factors were measured in 1986 and 1987, when residual NO3–N was low (87 and 99 kg ha−1, 0‐ to 2.4‐m depth) and NO3–N concentration was greater above than below 0.6 m. Sucrose yield increased an average of 0.54, 1.76, and 2.65 Mg ha−1 in 1986 and 1987 in response to N for irrigation levels averaging 0, 234, and 435 mm, respectively. Sucrose loss to molasses at the N rate needed for maximum sucrose yield averaged 15.2, 14.1, and 13.3 g sucrose kg−1 roots for 0, 234, and 435 mm irrigation levels, respectively. Sucrose loss to molasses averaged 20.1, 16.0, and 14.1 g kg−1 at the highest applied N rate for 0, 234, and 435 mm irrigation levels, respectively, and indicated a potential for serious impurity problems with excess residual or applied N and reduced irrigation.
Impacts of Cropping Intensity on Carbon and Nitrogen Mineralization under No‐Till Dryland Agroecosystems
Authors: Wood C. W. , Westfall D. G. , Peterson G. A. , Burke I. C.
Published: July 2010

Imposing no‐till and lower fallow frequency on soils previously managed under tilled and frequent fallow systems may alter soil organic C and N concentrations and activity (potential mineralization). This study was conducted to determine the effect of cropping intensity (number of crops/unit time) on surface soil (0‐5 cm) C and N activity after 3.5 yr of no‐till management. The effect was examined across three soil catenas in the West Central Great Plains that were previously managed under tilled and alternate crop‐fallow systems for >50 yr. Production systems included the less intensive wheat (Triticum aestivum L.)‐fallow (WF), and the more intensive wheat‐corn (Zea mays L.)‐millet (Panicum miliaceum L.)‐fallow (WCMF). After 3.5 yr of no‐till, potential C and N mineralization, C turnover, and relative N mineralization were 61,39,36, and 43% greater under WCMF than WF, respectively. Footslope soils had greater potential C and N mineralization than summit or backslope soils, but lower C turnover and relative N mineralization, which was probably due to long‐term accumulation of recalcitrant C and N compounds. Differences in potential soil C and N activity between cropping systems were due to greater surface organic C concentrations under WCMF (mean = 10.88 g kg−1) than WF (mean = 9.60 g kg−1), which were related to cumulative plant residue additions over the 3.5‐yr‐study period (mean = 9.01 and 7.04 Mg ha−1 for WCMF and WF, respectively). It appears that potentially active surface soil organic C and N are very sensitive to change in cultural practices, and are increased by greater cropping intensity under notill management.
Quantitative Method for Analysis of Grain Yield in Rice
Authors: Takami Shinichi , Kobata Tohru , Van Bavel C. H. M.
Published: July 2010

Cereal crop yields can be substantially reduced when drought occurs during grain filling. A mathematical expression is proposed to describe the effects of drought during the grain‐filling stage of rice (Oryza sativa L.). The expression predicts the grain yield as a function of the total dry matter production during the grain filling with two parameters: potential yield, and amount of mobilizable reserves at anthesis, both to be determined experimentally. The proposed relation states that grain yield equals the potential yield when the total assimilate supply (the amount of mobilizable reserves at anthesis, plus the total dry matter produced during grain filling) is equal to, or greater than the potential yield. Below this level of assimilate supply, grain yield decreases in proportion to the total dry matter produced during grain filling. Drought is assumed to reduce the grain yield through dry matter production alone, without any effects on the potential yield and the amount of mobilizable reserves. The model was tested in an experiment in which the yield response of two different cultivars to six levels of water availability was measured. The theoretical generalization fits the experimental results. The model is useful in predicting the yield response of rice when the crop encounters drought stress during grain filling, provided the two parameters cited above can be measured or estimated at anthesis. It also could serve as a submodel for yield prediction in a mechanistic crop production model.
Evaporation Measurements beneath Corn, Cotton, and Sunflower Canopies
Authors: Villalobos F. J. , Fereres E.
Published: July 2010

Experiments were conducted at Cordoba (southern Spain) between 1986 and 1988 to obtain independent estimates of evaporation from the soil (E) and crop transpiration (T) in irrigated corn (Zea mays L.), cotton (Gossypium hirsutum L.), and sunflower (Helianthus annuus L.). Microlysimeters that allowed root exploration were used to estimate E by differential weighing. Cotton and sunflower evapotranspiration (ET) were measured with a weighing lysimeter (3 by 2 by 1.5 m), while corn ET was estimated using a water balance technique. Root density and soil water content inside the open microlysinteters were similar to those measured in the surrounding soil. Estimated E, when the soil surface was wet, varied from 80% of reference ET (ET0) at 0.8 leaf area index (LAI) to 15% when LAI increased to four. A single relationship between E/ET0 and LAI fit the data for the three crops. The estimated E values for periods spanning 30 to 40 d, when LAI increased from 0.7 to 5, was 20 to 27% of measured ET, for an irrigation frequency of 7 to 8 d. The T values, calculated as the difference between ET and E, varied for a given LAI depending on the E level. When the soil surface was dry and E was low, the ratio, T/ET0, in cotton was 1.1 for a LAI of three. If the surface soil was wetted by rain or irrigation, the calculated T/ET0 ratio dropped to 0.58 the 1st d after wetting. The results highlight the interdependence of the E and T processes in the consumptive use of water by row crops.
Ultraviolet and Photosynthetically Active Bands: Plane Surface Irradiance at Corn Canopy Base
Authors: Grant Richard H.
Published: July 2010

The potential increase in ultraviolet (UV) irradiance and potential decrease in productivity of agricultural crops due to stratospheric ozone loss requires knowledge of the characteristics of UV irradiance above and within crops. Little is currently known about the distribution of UV radiation within crops. The objectives of this study were to describe the UV radiation environment with respect to the photosynthetically active radiation (PAR) environment at the base of a corn canopy and relate the differences in measured irradiances to differences in canopy characteristics and differences in the proportion of direct and diffuse radiation in the two wavelength bands. Measurements of the near UV (wavelength band approximately 305‐350 nm) and PAR irradiance on plane surfaces (such as leaves) oriented in a wide range of view zeniths and azimuths were made at the base of a corn canopy in September 1989 at West Lafayette, IN (solar zenith angle 54.6 ± 5°). Comparisons between the transmitted energy in near UV (NUV) and PAR wavelengths through the corn canopy were made using normalized paired irradiance measurements for a plane surface in 737 different view zenith and azimuth orientations. The NUV irradiance decreased more rapidly than the PAR irradiance as either the incidence angle (between the sun and the plane surface normal) or the view zenith angle increased. Results suggest that the corn canopy transmittance of PAR and NUV are similar but the canopy reflectance of PAR is greater than that of NUV.
Nitrogen Use by Tall Fescue and Switchgrass on Acidic Soils of Varying Water Holding Capacity
Authors: Staley T. E. , Stout W. L. , Jung G. A.
Published: July 2010

Increased use of bunchgrasses on acidic soils of the humid Northeastern USA requires more detailed knowledge on the fate of fertilizer N for economic and environmental reasons. A 3‐yr field investigation using 15N‐depleted fertilizer was undertaken to determine the effect of soil water holding capacity (WHC) on the use of soil and fertilizer N by cool‐season (tall fescue, Festuca arundinacea Schreb.) and warm‐season (switchgrass, Panicum virgatum L.) forages. Three sites of varying soil depth provided WHC of 5, 15, and 25 cm. Fertilizer N was applied at 0, 90, and 180 kg ha−1 (split application for tall fescue). Three‐year production averages for Cut 1 switchgrass (mid‐July) were two‐ to three‐fold greater than for tall fescue (mid‐June) on all sites receiving N, and four‐fold greater on the two shallower sites without N. Cut 2 (late‐October) production was nearly equal for both species, with tall fescue averaging 50%, and switchgrass 10%, of Cut 1. Nitrogen concentration of both species generally increased with N rate but not with WHC. Total N uptake (TNU) increased with N rate for both cuts of tall fescue, but only for Cut 1 for switchgrass, on all sites. Percentage of TNU derived from fertilizer N ranged from 23 to 47% for tall fescue and 14 to 39% for switchgrass. Tall fescue and switchgrass recovered from 23 to 31% and 25 to 33%, respectively, of the fertilizer N applied to the two deeper sites. Only on the shallow Klinesville site at the 90 kg N level was there a significant difference in fertilizer‐ N recovery, where switchgrass recovered 31% compared to tall fescue at 19%. Although these results demonstrate relatively low recoveries by both species, the more efficient use of fertilizer N by switchgrass, both in terms of production and recovery, recommend its increased usage at low N rates in the Appalachian Region.
Estimating Turf Biomass, Tiller Density, and Species Composition by Coring
Authors: Lush W. M. , Franz P. R.
Published: July 2010

The methodology for estimating tiller density, turf biomass, and species composition by core sampling was examined in order to establish an objective, quantitative protocol for measuring turf responses to management and for comparing genotypes. Cores were collected from a fine‐textured creeping bentgrass (Agrostis stolonifera L.) turf and an intermediate‐textured turf composed of Kentucky bluegrass (Poa pratensis L.), ryegrass (Lolium perenne L.) and annual bluegrass (P. annua L.). Estimates based on different sampling tools, one rectangular and three round, and different methods of storing cores between collection in the field and processing in the laboratory were examined. It is concluded that the numbers of cores needed to estimate, at a specified level of accuracy, the biomass and tiller density of a turf (or of the most frequently occurring species in a turf) are low enough (e.g. eight to 43 cores of 4.8‐cm diam.) for coring to be a practical way of quantifying the standing vegetation of turfs. Coring is not a good method for estimating infrequently occurring species because of the large numbers of cores required, in this case around 3000. Estimates of tiller density or biomass were biased in cores with a long perimeter relative to their cross‐sectional area by soil entrapment (especially if free water accumulated during storage), and in cores that became desiccated during storage.
Corn‐Weed Interactions with Long‐Term Conservation Tillage Management
Authors: Coffman C. Benjamin , Frank J. Ray
Published: July 2010

The use of monoculture production systems such as continuous corn (Zea mays L.) in conservation‐tillage systems has created a requirement for information concerning crop and weed responses to annual herbicide inputs. The objective of this 5‐yr investigation (1981–1985) was to evaluate weed problems and delineate weed and crop interactions in continuous conservation‐tillage corn as affected by annual herbicide applications. Preemergence treatments contained selected combinations of triazines or a triazine plus alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl)acetamide]. Preemergence or preplant incorporated herbicide mixtures were applied at common usage rates and compared for their effects on weed cover, weed species stability, and grain production. All plots were essentially weed‐free the first year. Weed cover in most treatments increased significantly by the second year with fall panicum (Panicum dichotomiflorum Michx.) dominating the flora in Years 2 and 3, and smooth pigweed (Amaranthus hybridus L.) dominating in Years 4 and 5. Smooth pigweed reached densities of 85% in several treatments. Fall panicum was the dominant weed in pre‐plant incorporated treatments that contained atrazine [6‐chloro‐N‐ethyl‐N'‐(l‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine] plus a carbamothioate herbicide. Grain yields were negatively correlated with fall panicum densities in the second year in all herbicide treatments. Smooth pigweed densities were negatively correlated with grain yields in the fifth year in all preemergence treatments. Smooth pigweed densities were lower in triazine plus alachlor treatments than in double triazine treatments for the last 2 yr of the study.
Cotton Response to Water and Salinity under Sprinkler and Drip Irrigation
Authors: Meiri A. , Frenkel H. , Mantell A.
Published: July 2010

Knowledge of crop response to water is essential for proper irrigation management. The wide‐spread introduction of drip irrigation, together with the increasing use of brackish water for cotton (Gossypium hirsutum L.) has made it necessary to examine how these variables effect its production function. A field study was conducted to determine the interaction of water salinity (3.7–7.8 dS m−1), irrigation method (sprinkler and drip), water amount (230–780 mm), irrigation interval (1–14 d), and plant density (intra‐row spacing of 8 or 12.5 cm) on ‘Acala SJ‐2’' cotton grown on a sandy‐loam loess soil (Calcic Haploxeralf). With sprinkler irrigation, the two‐piecewise curves that describe the yield response to water application differ in slopes, intercepts, and break points for the different salinites and irrigation intervals. The crop used more stored soil water at low salinity, low irrigation amount, and long irrigation interval. When we evaluated crop response to the sum of applied water and amount of stored water used, we found that the intercepts were nearly eliminated and the four slopes were combined, while the break points remained lower for the higher water salinity. The break points determine the water amounts above which other factors become limiting. The response function for drip irrigation had no break point, but had the same slope and intercept as the sprinkler treatments. The common production functions for seed cotton and total dry matter yield were Y kg ha−1 = −26.5 kg ha−1 + 9.21 kg ha−1 mm−1 × Wmm and Y kg ha−1 = −338 kg ha−1 + 21.2 kg ha−1 mm−1 × Wmm, respectively, where Y = yield, and W = sum of seasonal water application plus depletion of stored soil water. Water salinity, irrigation method and frequency, and intrarow spacing did not affect the linear response of seed cotton or dry matter yields to water when factors other than water availability were not limiting.
Temperature Effects on Pima Cotton Growth and Development
Authors: Reddy K.R. , Hodges H.F. , McKinion J.M. , Wall G.W.
Published: July 2010

An understanding of genetic and environmental factors affecting plant growth and development is needed for accurate yield predictions by crop models. At present there is little information about how Pima cotton, Gossypium barbadense L., a species known for its excellent lint quality, will respond to various temperatures. The objective of this experiment was to determine the growth and developmental rates of Pima cotton plants grown at different temperatures. Pima cotton was grown in 20/12, 25/17, 30/22, 35/27, and 40/32°C day/night temperature cycles in sunlit controlled‐environment chambers soon after emergence to 64 d under optimum water and nutrient conditions. Plant heights and mainstem nodes were determined at weekly intervals. Mainstem elongation rates were very sensitive to temperature after about 3 wk following emergence. Prior to that time, the differences were small but measurable. Mainstem node addition rate increased as temperature increased to 40/32°C. The temperature optimum for fruiting branch growth, and square and boll production and retention was 30/22°C. Above 30/22°C, there was an imbalance between vegetative and reproductive growth. Plants became less reproductive at 35/27°C and lost their reproductive ability at 40/32°C. Heat tolerance, as depicted by heat units required to produce first square, is much superior to that reported for Pima, cv. S‐2, but slightly less than Upland cotton, cv. DES 119.
Simulation of Normal Annual and Diurnal Temperature Oscillations in Non‐Mountainous Mainland United States
Authors: Fernández C.J.
Published: July 2010

Simulation of air temperature data may add flexibility to many computer programs for modeling crop growth. An empirical model was developed to simulate both average annual air temperatures and average diurnal oscillations of air temperature, at any location within the USA east of the Rocky Mountains and with elevation below 1500 m above sea level. The target region was divided into four zones according to average annual rainfall and proximity to the Atlantic Ocean. Annual oscillations of the daily mean, maximum, and minimum temperatures for a given location were simulated with single sine‐wave equations. The average and amplitude parameters of these equations are calculated from estimates of the monthly maximum and minimum temperature normals of January and July. These four temperature normals were estimated using regression equations on latitude. Different sets of equations were used for each location zone. Diurnal oscillations of temperature on a given day at the given location were simulated by joining two sine waves to give a single smooth asymmetrical wave. The average and amplitude parameters of these diurnal oscillations were obtained from the annual curves previously simulated. The accuracy of the model in simulating annual oscillations of daily maximum and minimum temperatures was tested. Simulated and observed average monthly temperatures recorded at 27 weather stations correlated with r = 0.993 (significant at Ρ = 0.01). Plots of residuals against months showed that the model underestimated the monthly temperatures around the vernal equinox (average residuals ranged from −1.76 to −2.66°C). The accuracy of the model in simulating diurnal oscillation was also tested. Simulated and observed temperatures at 3‐h intervals for 18 cloudless days and 18 overcast days correlated with r = 0.992 (significant at P = 0.01). Plots of residuals against time showed that the model underestimated the temperature during the warming phase in clear‐sky days (average residuals were about −3°C.
Microcomputer‐Based Experiment Management System: II. Data Analysis
Authors: Loussaert Dale
Published: July 2010

Microcomputer‐based statistical analysis can provide a convenient, inexpensive means of data analysis. Computer software has been developed to complement a general experiment management system. The software will perform analysis of variance, with or without covariant analysis, of data arranged in various experimental designs. Regression analysis, best fit regression and multiple regression analysis can also be conducted with this software. Data can be input as a continuation of complementary experiment management software or entered through a text file. The treatment means can be grouped in any combination of treatments or treatment interactions desired and comparisons may be made using Least Significant Difference comparisons, a Student's t‐probability matrix, or specific treatment means may be pooled to make specific comparisons. This system provides a convenient means of doing lower level statistical comparisons using an IBM/compatible computer.
Early Maturing Soybean Nodulation and Performance with Selected Bradyrhizobium japonicum Strains
Authors: Wiersma J. V. , Orf J. H.
Published: July 2010

Seed inoculation with Bradyrhizobium japonicum (Kirchner) Jordan is a common production practice for most soybean [Glycine max (L.) Merr.] growers in northwest Minnesota; however, plants seldom are well‐nodulated. Our objectives were to (i) identify strains of B. japonicum that enhance nodulation and agronomic performance of Maturity Group 00 soybean cultivars grown on soils having a range of NO3−−N concentrations; and (ii) assess cultivar‐by‐strain specificity. Six cultivars and five B. japonicum strains were evaluated in six field trials during 1988 to 1990. Nonfertilized (1988–1990) and N fertilized (1990), uninoculated controls were included. Soil NO3−−N concentrations (0–60 cm) at planting ranged from 52 to 175 kg N ha−1. Residual soil NO3−−N values were low and substantially less than initial values in only three environments. Nonetheless, significant increases in response to inoculation were observed for grain yield, seed weight, and grain N concentration in 17 of 18 comparisons. In 1990 trials, fertilizer N (168 kg ha−1) increased seed weight and grain N concentration significantly more than inoculation. Nodule number (r = −0.89; significant at P = 0.05) and dry weight (r = −0.97; significant at P = 0.01) were inversely correlated with soil NO3−−N (0–60 cm) at planting. Estimated (difference method) N2 fixation (r = ‐0.93; significant at P = 0.05) and relative increases in grain yield (r = −0.93; significant at P = 0.05), seed weight (r = ‐0.97; significant at P = 0.01) and grain N concentration (r = −0.95; significant at P = 0.05) were inversely correlated with soil NO3−−N (0–60 cm) at harvest. Although similar responses were observed among all cultivars, B. japonicum strains 61A152 and 61A212 generally outperformed other strains. Cultivar‐by‐strain specificity could not be detected. Soybean producers in northwest Minnesota should realize significant increases (10% or greater) in grain yield in response to inoculation of rhizobia‐free soils, provided initial soil NO3−−N concentrations (0–60 cm) are less than 110 kg N ha−1 and N mineralization during the growing season is minimal.
Nitrogen, Phosphorus, and Potassium Fertilization for Histosol‐Grown St. Augustinegrass Sod
Authors: Cisar J. L. , Snyder G. H. , Swanson G. S.
Published: July 2010

Histosol‐grown sod is a major agricultural commodity in Florida. Sod fertility requirements need to be identified in order to maximize sod productivity, avoid fertilizer waste, and minimize undesirable impacts on water quality. An experiment was conducted for two consecutive years to determine the effect of N, P, and K fertilization on St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] sod production on a well‐decomposed Histosol (muck). Treatment comparisons were based on turf growth, turf visual quality ratings, cut sod piece quality, tear resistance of cut sod pieces, and measures of cut sod transplantability on sand soil. Nitrogen fertilization improved visual quality and clipping yield of the sod, and of sod pieces re‐established on a sand soil, but did not affect sod tear resistance or quality of sod pieces as judged by experienced sod growers. When the initial water‐extractable P soil‐test was low (3.7 mg P L−1), all measured parameters (except tear resistance) were increased by P fertilization. Potassium fertilization did not affect any measured parameters of sod production, even when the initial acetic acid‐extractable K soil‐test index was 54 mg K L−1, which is low for most crops. Overall, results indicate that N, P, and K fertilizer rates used for sod production on Histosols can be reduced substantially from previous recommendations.
Potassium in Two Humid Tropical Ultisols under a Corn and Soybean Cropping System: II. Dynamics
Authors: Cox F. R. , Uribe E.
Published: July 2010

Understanding the dynamics of soil K is important for the formulation of a sound fertilizer management strategy. Two experiments were conducted to determine the behavior of K in the soil after fertilization. Five rates of K (0 to 120 kg ha−1) were applied to two Typic Paleudults, a loam and a sandy loam, in the Peruvian Amazon Basin. A three‐crop rotation of corn (Zeu mays L.), corn, and soybean [Glycine max (L.) Merr.] was planted at each site. Three additional crops of corn were grown at the loam site. Potassium rates were applied only to the first crop of each three‐crop cycle. The corn stover was returned, while the soybean stover was removed. Soil samples were taken at germination, flowering, and harvest of each crop at 20‐cm depth intervals to 60 cm in the loam and 80 em in the sandy loam. Soil K was extracted with NaHCO3, NH4OAc, and concentrated H2SO4. Topsoil exchangeable K increased markedly with K addition, either as fertilizer or as stover, but rapidly decreased during cropping. Changes in the exchangeable pool were characterized with an exponential model. Increases in exchangeable K below 20 cm were of minor significance for the loam. For the sandy loam, however, subsoil exchangeable K was significantly increased to 60 cm. Evidences of K fixation and release were detected in the loam where the topsoil non‐exchangeable pool peaked after K additions and decreased during cropping. There was no evidence of fixation in the sandy loam. These differences suggest that higher K rates can be applied to the finer textured soils and there is less risk of loss of K from the rooting zone.
Yield Enhancement in Cotton by Frequent Irrigations during Fruiting
Authors: Radin J.W. , Reaves L.L. , Mauney J.R. , French O.F.
Published: July 2010

Daily drip irrigation often increases yield and water‐use efficiency of cotton (Gossypium hirsutum L.) compared to conventional irrigations applied at long intervals. A 2 yr experiment was designed to test whether these benefits could be achieved without using an expensive drip system. Cotton was irrigated every 10 d in the first year and every 14 d in the second year (control treatment). A supplemental irrigation was applied during either one or two long irrigation cycles coinciding with peak fruiting. The total amount of water applied was minimally changed from the control because other irrigations were reduced to compensate for the supplementation. Another treatment was drip‐irrigated daily throughout most of the season. One supplement increased seedcotton yield 15% over the control, and two supplements increased it 25%, compared to a 40% yield increase with drip irrigation. These three treatments increased crop water‐use efficiency (yield per unit applied water plus rainfall) by 12, 22 and 50%, respectively. Yield increases were associated with a lengthened period of profuse flowering and a delay in the onset of cutout. Both drip irrigation and mid‐cycle supplements increased midday leaf water potential and apparent hydraulic conductance of the plants for an extended period during fruiting, indicating enhanced water uptake and transport capacity compared to plants on long cycles. The results show that a drip system is not necessary for substantial improvements of yield and water‐use efficiency. Doubling the number of irrigations for a short period during peak fruiting achieved much of the benefits of drip irrigation.
Grain Sorghum and Pearl Millet Response to Date and Rate of Planting
Authors: M'Khaitir Y. O. , Vanderlip R. L.
Published: July 2010

Pearl millet [Pennisetum glaucum (L.) R. Br.] often is grown in the same areas as sorghum [Sorghum bicolor (L.) Moench]. The crops are similar in use and adaptation, but differ in ways that might affect management requirements. For example, the high tillering capability of millet might result in different responses to plant population and planting date. A study to compare pearl millet and sorghum yield response to rate and date of planting was conducted for 2 yr at St. John, on a Naron fine sandy loam (fine‐loamy, mixed, thermic Udic Argiustoll), and Manhattan, KS, on a Reading silt loam (fine, mixed, mesic Typic Arguidoll). In 1988, a millet hybrid (81‐1056 ✕ 86‐9001), a millet variety (Senegal bulk), and a sorghum hybrid (DeKalb 39Y) were planted at 15 000, 45 000, and 135 000 plants/ha on three dates. In 1989, another millet hybrid (81‐1086 ✕ 87‐8025) was added. The experiment was a modified split‐plot design with dates of planting as main plots stripped across replicates and combinations of population and variety as subplots. Planting date had no consistent effect on either crop. Plant population had no effect on millet yield. Some yield components, particularly heads per plant, increased and compensated for low populations. Sorghum yield increased with increasing population, but plant population had no consistent effect on sorghum yield components. Sorghum yielded significantly more than millet at high populations, but not at low and medium populations. These results indicate that precise plant population is much less critical for pearl millet than for sorghum in determining final yield.
Quality and Growth Response of Centipedegrass to Extended Drought
Authors: Hook J. E. , Hanna W. W. , Maw B. W.
Published: July 2010

Many of today's landscapes require turfgrasses that can survive extended drought periods without supplemental water. Centipedegrass [Eremochloa ophiuroides (Munro.) Hack.] has long been used as a low‐maintenance lawn grass for the Southeast. A controlled drought study was used to determine the quality, growth, and recovery of centipedegrass held in stress for periods of 7 to 30 d. Common centipedegrass, established under an automated rainfall shelter, was subjected to three drought (drydown) regimes ‐ NOSTRESS, watered twice per week; MODERATE, 2 to 3 wk between watering; and SEVERE, 4 to 6 wk between watering. Soil water was monitored daily to 0.7 m depth with resistance type sensors. Clipping biomass, relative leaf water content, and visual rating were monitored weekly. Available water dropped below 30% in the 0.7 m profile in 7 to 14 d after complete rewetting, and drought stress, indicated by wilting, became evident. The period of drought stress extended for 10 to 30d during which weekly clipping biomass decreased by 50 to 70% below that of NOSTRESS turf. Visual ratings declined along with biomass decrease, falling below acceptable quality rating when drought stress lasted longer than 7 to 10 d. Relative leaf water content declined from about 80% for NOSTRESS to as low as 40% at the end of the SEVERE drought periods. Recovery of leaf water content following watering was not complete, due either to an adaptive response to drydown or to incomplete recovery of the grass. When as much as 3 wk elapsed between watering, irrigation of centipedegrass resulted in recovery of clipping biomass and visual ratings nearly to that of the NOSTRESS treatment. When drought extended for 6 wk, turf quality was low, but centipedegrass survived and recovered to levels suitable for lawns.
Nitrogen Assimilation Traits and Dinitrogen Fixation in Soybean and Common Bean
Authors: George T. , Singleton P.W.
Published: July 2010

Nitrogen derived from symbiotic and mineral sources by a legume is determined by the interactions between mineral N supply, plant N demand, and N assimilation traits. These interactions need to be understood to maximize legume N2, fixation and yield, and to identify plant traits supporting high N2‐fixation. These interactions were examined in inoculated soybean [Glycine max Merr. (L.)] and common bean (Phaseolus vulgaris L.) by varying N supply (9, 120, and 900 kg N ha−1) at two field sites. Nitrogen fixation was measured by 15N dilution method. Plants were sampled at full bloom (R2), 21 to 25 d from R2, and physiological maturity (R7). Total N of both legumes at R7 was 25% greater with 900 than 9 kg N ha−1. With 900 kg N ha−1, soybean N accumulation at R7 (271 kg N ha−1) was 42% more than common bean but was 22% less at R2 (78 kg N ha−1). Applied N had the largest impact on N accumulation rates before R2 and from the second sampling to R7, both periods of minimal N2 fixation. Rate of N accumulation by common bean (0.19 g N m−2 d−1) was more uniform over the growth cycle than by soybean (0.26 g N m−2 d−1) which peaked (0.58 g N m−2 d−1) between R2 and the second sampling. This peak also coincided with maximum N2 fixation rate. Our 15N uptake and extractable soil N data indicate that common bean derived more N from the mineral source than soybean because of more efficient uptake. Greenhouse data indicated greater root weight and uptake of mineral N per unit root weight for common bean than soybean. Maximizing both N2 fixation and yield might entail timing the mineral N supply during early vegetative and late reproductive phases. The limited N2 fixation capacity of common bean might be due to N assimilation traits favoring mineral N uptake.
Time Domain Reflectometry in Closed Container Studies
Authors: Richardson M. D. , Meisner C. A. , Hoveland C. S. , Karnok K. J.
Published: July 2010

Time domain reflectometry (TDR) has been widely utilized to estimate soil water content in field plots, but applications to controlled environment experiments have not been adequately described. The TDR procedure was used in three closed‐container, greenhouse studies to monitor soil moisture levels and dictate watering schedules. In all experiments, TDR was an efficient method for monitoring soil water. Also, estimation of soil water content by TDR was highly correlated to gravimetric analysis of soil cores, with r2 values of 0.84, 0.96, and 0.98 for the three studies. Different soil types, with variable physical properties and bulk densities, had no apparent effect on estimations of soil water content. It was concluded that TDR could be useful in greenhouse studies to accurately determine soil water content.
Nonionic Surfactant and Supplemental Irrigation of Soybean on Crusting Soils
Authors: McCauley G. N.
Published: July 2010

Agricultural land use in much of the Texas Coastal Prairie consists of 1 yr of rice (Oryza sativa L.) followed by 2 to 4 yr of native pasture. Replacing some of the native pasture with a cultivated rotational crop could benefit the area's agricultural base by reducing fixed costs and aiding pest management. Soybean [Glycine max (L.) Merr.] fits the crop rotation system well but yields are highly variable and marginally economical. Research was initiated in 1985 near Eagle Lake, TX, to evaluate the potential of a nonionic surfactant and supplemental irrigation to increase and stabilize soybean yields on the Nada soil (fine loamy, silicous, hyperthermic Typic Albaqualf). In addition the effect of the surfactant and irrigation on P and K fertilizer efficiency was evaluated. The nonionic surfactant (Amway ASPA 80; Amway Corp., Ada, MI) was injected through a lateral‐move irrigation system at 0.00, 0.36, 0.71, and 1.42 L ha−1 during a 7 mm irrigation. Adjuvant rate, repeated adjuvant applications within 1 yr and over 3 yr, and P and K at the recommended and half the recommended rates were evaluated. Supplemental irrigation was applied so irrigation plus rainfall equalled 19 mm wk−1. No measurable yield differences between P and K rates were detected. The adjuvant at 0.36 L ha−1 increased soybean yields 37% above the check. Adjuvant at the 0.71 and 1.42 L ha−1 rate decreased yield from the 0.36 L ha−1 rate. No phytotoxicity was observed. Multiple adjuvant applications during 1 yr, and repeated applications to the same area over years, had no additional beneficial yield effect.
Nitrogen Fertilizer and Cultivar Effects on Yield and Nitrogen‐Use Efficiency of Grain Amaranth
Authors: Elbehri A. , Putnam D.H. , Schmitt M.
Published: July 2010

Knowledge of fertility requirements or nitrogen‐use efficiency of amaranth (Amaranthus spp.) cultivars is limited. The objectives of this research were to determine the response of grain amaranth to applied N, P, and K, and to determine the effect of cultivar and fertilizer N on nitrogen‐use efficiency. Two field experiments were conducted. In the first, five rates of N, P, and K were applied in a central composite design with the cultivar Plainsman grown in five environments. In a second experiment, six amaranth cultivars, Amont, K266, K283, Plainsman, K432 and D136, were grown in three environments with five N rates (0, 45, 90, 135, and 180 kg N ha−1). There was no response to P and K applications when initial soil tests were above 68 kg P ha−1, and 172 kg K ha−1, respectively, but grain amaranth responded linearly to applied P at one location with initial soil P tests of 11 kg ha−1. Grain yield ranged from 794 to 1980 kg ha−1 and responded to N in most environments. Forage yield ranged from 6.1 to 16.6 Mg ha−1 and was increased at higher N rates. At all locations, lodging increased with application of N. Fertilizer N increased pre‐flowering N accumulation but not post‐flowering N accumulation. Nitrogen‐use efficiency (NUE) ratio of grain yield to total soil N supply ranged from 3.48 to 7.91 kg kg−1 across cultivars and environments. Nitrogen‐use efficiency decreased with increased soil N mainly because of decreasing N‐uptake efficiency (ratio of total plant N to total soil N). Grain amaranth is relatively inefficient in N‐use primarily because of its low harvest index (HI = 9–15%) and N harvest index (NHI = 12–26%). This suggests that selection for higher HI and NHI could be effective in improving grain yield and nitrogenuse efficiency of grain amaranth.
Evaluation of the Nitrogen Submodel of CERES‐Maize Following Legume Green Manure Incorporation
Authors: Bowen W. T. , Jones J. W. , Carsky R. J. , Quintana J. O.
Published: July 2010

Crop simulation models that accurately predict the availability of N from decomposing plant residues would provide a powerful tool for evaluating legume green manures as potential N sources for nonlegume crops. Using measured data from a series of field experiments conducted on an Oxisol in central Brazil, we conducted this study to test the N submodel of CERES‐Maize for its ability to simulate N mineralization, nitrate leaching, and N uptake by maize (Zea Mays L.) following the incorporation of 10 different legume green manures. Legume or weed residue N at the time of incorporation varied from 25 to 300 kg ha−1 with C/N ratios varying from 13 to 37. Comparison of predicted and measured accumulation of inorganic N in uncropped soil showed that the model usually provided a realistic simulation of legume N release, although N release was overpredicted for some legumes. For all legumes, both simulated and measured data showed that about 60% of the organic N applied was recovered as inorganic N within 120 to 150 d after incorporation. To realistically simulate N availability when rainfall was excessive, we modified the model to account for delayed leaching due to nitrate retention in the subsoil. Nitrogen uptake by maize was generally overpredicted at high levels of available N. The N submodel was shown to realistically simulate legume N release, but further work is needed to determine the importance of subsoil nitrate retention in other soils and how best such retention might be described in the model.
Mid‐Infrared Microspectroscopy to Assess Lignin in Plant Tissues Related to Digestibility
Authors: Akin D. E. , Himmelsbach D. S. , Carl R. T. , Hanna W. W. , Barton F. E.
Published: July 2010

Techniques are needed to rapidly assess the location of phenotics within cell types. The objective of this work was to investigate by midinfrared microspectroscopy a series of intact cell types, which have a range of digestibilities, from normal (N) and brown midrib (bmr) pearl millet [Pennisetum glaucum (L) R. Br.]. Rind and parenchyma tissues were evaluated using a Nicolet System 740 spectrometer equipped with a Nicolet 0.25 mm MCT‐A detector1 interfaced to a microscope. Spectra of rind were similar for normal and bmr mutants and closely resembled lignin spectra. Spectra of pith tissue were similar among plant types and to that for carbohydrates, but differed from rind spectra. Preliminary results indicated that spectra were different for tissues of different digestibilities and showed promise for the use of microspectroscopy in evaluating forage quality of cell types.
Fractal Analysis for Morphological Description of Corn Roots under Nitrogen Stress
Authors: Eghball Bahman , Settimi John R. , Maranville Jerry W. , Parkhurst Anne M.
Published: July 2010

A means of quantification of plant root branching, specifically under stress, is of importance for evaluating the contribution of plant roots to water and nutrient uptake and subsequently plant growth. An experiment was conducted to describe the morphology of corn (Zea mays L.) root systems using fractal analysis and also to determine if a root’s fractal dimension (D) is altered by N stress. Corn genotypes (B73 ✕ LH105 and N74 ✕ Mo17) were planted in peg boxes, 1.2 m long, 1.2 m deep, and 0.05 m wide filled with 20:80 soil to sand mixture and were grown with N rates of 0, 10, 20 and 30 mg kg−1. Thirtynine days after planting, the mixture was gently washed from the roots and the roots were divided into nine sections (squares of side 304.8 mm) and slide photographs were taken from each section. The slides were projected on grids made up of 122, 242, and 482 squares of sides (r) 25.4, 12.7, and 6.35 mm, respectively. Regression of log of number of squares intersected by roots vs. long of r levels was used to determine the slope (—D). Fractal dimension was significantly smaller for zero N compared to applied N with no detectable difference among applied N levels. Fractal dimension was highest for the section directly below the crown (D = 1.73) indicating high root branching and was lowest for the sections in deeper soil (D = 1.19, average of 3 sections in the 0.6 to 0.9‐m depth) indicating less branching. The intercept of the regression line (log K), which indicates root abundance, was lowest for zero N. Amount of roots in the section directly below the crown was 45% of total roots. Nitrogen stress changed the morphology of corn root system and caused less root branching. Fractal analysis was a useful method for describing the morphology of corn root systems, both quantitatively and qualitatively.
Crop Performance Trials under Irrigated and Dryland Conditions
Authors: Bowman Daryl , Raymer Paul , Dombeck Don
Published: July 2010

Corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] performance trials are sometimes conducted under both irrigated and dryland conditions in the southeastern USA. It is not known whether irrigated trials are better trials statistically or if irrigation causes relative rank changes in hybrid or cultivar performance. To answer these questions, corn data were examined from four different environments and three maturity groups, and soybean data were examined from five different environments and three maturity groups between 1987 and 1990. Water management × hybrid/cultivar interactions were evident in 8 of 12 corn data sets and 7 of 16 soybean data sets. Combining data across years eliminated the water management × hybrid/cultivar interactions in all soybean data sets and five of nine corn data sets. Irrigated corn trials produced year × hybrid interactions in seven of nine data sets while dryland trials produced year × hybrid interactions in four of nine data sets. Irrigated trials were only slightly better than dryland trials in accounting for variation; i.e., larger r2 values but produced smaller error variances in four of 12 data sets of corn. Irrigated trials separated entries better in nearly half of the soybean data sets. The data suggested that irrigated trials were not statistically better trials than dryland trials in all situations. Water management × hybrid/ cultivar interactions suggest that data for irrigated and dryland trials should be reported separately, and the year × hybrid/cultivar interactions indicated that multi‐year data should be examined during hybrid/ cultivar selection. Error variances, F probability values, and r2 values should be examined to determine level of precision when comparing trials of equal composition.
Radiation‐Use Efficiency among Grain Sorghum Cultivars and Plant Densities
Authors: Rosenthal W. D. , Gerik T. J. , Wade L. J.
Published: July 2010

Radiation‐use efficiency (RUE, g MJ−1) has often been used in many crop model equations to estimate total biomass and yield based on cumulative absorbed photosynthetically active radiation. Management practice effects on radiation‐use efficiency have not been well documented for grain sorghum [Sorghum bicolor (L.) Moench]. A field study was conducted near Temple, TX to determine plant density and cultivar effects on RUE in grain sorghum. Early ‘Cargill 4462’ and late maturing ‘Cargill 6670’ cultivars were planted on a Houston Black clay (fine, montmorillonitic, thermic Udic Paleustert) on 16 Mar. and 1 Aug. 1989 at 5, 12, 19, and 26 plants per square meter. Incoming, reflected, and transmitted photosynthetically active radiation were measured weekly from 6 wk after emergence until full anthesis. Dry matter and leaf area index were determined from 0.5‐m2 areas immediately after the radiation measurements. The calculated extinction coefficient, 0.51, for PAR transmittance was significantly lower than in the crop growth model, SORKAM, documentation. This new value of extinction coefficient reduces total dry matter in and increases RUE in SORKAM. The average RUE for all treatments was 3.5 g MJ−1 as compared with 3.2 g MJ−1 in SORKAM. The new values will be incorporated into SORKAM. No significant radiation use efficiency differences were detected among density and maturity class treatments.