bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractConverting 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

AbstractUptake 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

AbstractField‐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

AbstractSimulation 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

AbstractNo‐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

AbstractShifting 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

AbstractCommon 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

AbstractNo‐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.
Corn, Sunflower, and Soybean Emergence Influenced by Soil Temperature and Soil Water Content
Authors: Helms Theodore C. , Deckard Edward L. , Gregoire Peter A. 
Published: July 2010

AbstractThe influence of soil temperature and initial soil water content on subsequent germination and emergence of corn (Zea mays L.), sunflower (Helianthus annuus L.), and soybean [Glycine max (L.) Merr.] needs to be understood. Previous research has not determined whether emergence of corn and sunflower is reduced by soil water content that is high enough for seed imbibition but too low for radicle emergence from the testa. Our objective was to evaluate corn, sunflower, and soybean emergence influenced by initial seed‐zone soil water content of 0.05, 0.07, and 0.09 kg kg−1 and soil drying at three day/night (17/8, 21/12, 25/16°C) soil temperature regimes as the number of days of soil water deficit and temperature stress increased. A factorial experiment with two replicates was conducted under controlled temperature conditions in an incubator. This experiment was conducted using a Glyndon silty clay loam (coarse‐silty, frigid Aeric Calciaquolls). Corn emergence was >85% at all three initial soil water contents and temperature regimes. Sunflower emergence increased from 59% at the low initial soil water content to 90% at the higher initial soil water content. Soybean emergence was 22% after stress was imposed by a 0.07 kg kg−1 initial soil water content (high enough for seed imbibition but too low for germination). If soil water content is sufficient to imbibe seeds of soybean and sunflower, but too low for germination during the 6 d after planting, producers may need to replant, especially when soil temperature is above 21/12°C.
Developing Guidelines for Replanting Grain Sorghum: I. Validation and Sensitivity Analysis of the SORKAM Sorghum Growth Model
Authors: Heiniger Ronnie W. , Vanderlip Richard L. , Welch Stephen M. 
Published: July 2010

AbstractSorghum [Sorghum bicolor (L.) Moench] producers often have difficulty determining when plant stands are low enough to merit replanting. Our objective was to use SORKAM, a sorghum growth model, to develop guidelines for replanting grain sorghum. A necessary first step is validation of the model over an extensive range of management and environmental factors. Validation was accomplished using 19 field data sets representing 11 yr and six Kansas locations. Several nonparametric tests were used to compare observed and simulated yields, yield components, and phenological dates. In addition, sensitivities of yield and yield components were determined in response to yearly climate, planting date, plant population, and maturity class changes. Model sensitivities were compared with sensitivities calculated from field data. While phenological predictions were adequate, SORKAM could capture only 27 to 79% of grain yield variability at the locations tested. Yield predictions from different plant populations within a planting date were particularly inaccurate. The validation and sensitivity analyses showed that the poor yield predictions were the result of improper computation of tiller number and faulty partitioning of biomass to caryopsis weight. Partitioning errors translocated enough assimilate from culm to grain to make yields essentially constant across populations within a planting date. To use SORKAM to generate replant guidelines, improvements must be made in modeling the relationships among yield components and the source‐sink relationship that determines caryopsis weight.
Early‐Maturing Soybean Cropping System: I. Yield Responses to Planting Date
Authors: Kane Mark V. , Steele Colleen C. , Grabau Larry J. 
Published: July 2010

AbstractAn early‐planted, early‐maturing soybean [Glycine max (L.) Merrill] cropping system has been quite successful across the southeastern USA. This cropping system was intended to use early planting to improve yield by avoiding late season drought stress. However, producers in this region use planting dates ranging from late April through late June. Our objective was to characterize the yield response of early‐maturing cultivars to environmental conditions over a range of planting dates. Field studies were conducted on a well‐drained Maury silt loam (fine, mixed, mesic Typic Paleudalf) in 1990 through 1993 using cultivars from Maturity Group (MG) 00 through IV planted in late April, mid‐May, early June, and late June each year. Modest moisture stress was observed over the years tested; however, temperatures during soybean growth stages depended strongly on planting dates. When averaged across years and cultivars, yields were similar for the first three planting dates. Best overall yields were obtained using the MG IV cultivar for late April and mid‐May planting; however, its advantage over MG II and III cultivars diminished for the early June planting date and disappeared for the late June planting date. Early‐maturing cultivars (MG 00 to I) were less likely to achieve competitive yield levels. Lower yields of early‐maturing cultivars for the late April planting date were associated with low temperatures during vegetative growth and with high temperatures during seedfill. In the absence of pronounced moisture stress, low or high temperatures may become the key environmental factors limiting yield. Early planting, a centerpiece of previous successful early‐maturing soybean cropping systems in the southeastern USA, appears to be less important under more favorable moisture conditions.
Early‐Maturing Soybean Cropping System: II. Growth and Development Responses to Environmental Conditions
Authors: Kane Mark V. , Steele Colleen C. , Grabau Larry J. 
Published: July 2010

AbstractProduction of early‐planted, early‐maturing soybean [Glycine max (L.) Merrill] cultivars has gained popularity in the southeastern USA in recent years, primarily as a drought‐avoidance mechanism. In seasons with adequate rainfall, however, early planting of such cultivars may not be essential for competitive yields. Our objective was to identify key environmental constraints to the growth and development of early‐maturing soybean in the southern region. Soybean cultivars from Maturity Groups (MG) 00 through IV were planted in late April, mid‐May, early June, and late June in 1990 through 1993 in 0.38‐m rows on a well‐drained Maury silt loam soil (fine, mixed, mesic Typic Paleudalf). Canopy closure, plant height, and plant mass per unit area were recorded at both R1 and R5. In addition, crop growth rate from R1 to R5 was calculated. Cool vegetative‐stage temperatures suppressed vegetative growth, particularly of early‐maturing cultivars and for early planting dates. Crop growth rate during pod‐set was not consistently associated with yield. Canopy closure at R1 of early‐maturing cultivars was more responsive to delayed planting than was that of later maturing cultivars. Across years and planting dates, canopy closure at R5 of MG 00 to I cultivars generally fell below 90%, while that of MG II to IV cultivars generally exceeded 90%. Early planting may be a disadvantage for early‐maturing cultivars in seasons with favorable rainfall patterns, particularly if canopy development is inhibited by cool temperatures during vegetative growth. If moisture is not limiting, delayed planting of early‐maturing cultivars may be advantageous.
Agronomic Response of Winter Rapeseed to Rate and Date of Seeding
Authors: Moore Mary K. , Guy Stephen O. 
Published: July 2010

AbstractIn northern Idaho, winter rapeseed (Brassica napus L.) usually is seeded on summer fallow in early to mid‐August at 4.5 to 13.5 kg seed ha−1. A 2‐yr study was conducted at Moscow, ID, to quantify crop performance as influenced by date of seeding and seeding rate. In the 1991–1992 and 1992–1993 growing seasons, high‐erucic‐acid winter rapeseed cultivars, ‘Dwarf Essex’ and ‘Bridger’, were seeded on four dates at 2‐wk intervals from early August to mid‐September at four seeding rates from 0.9 to 2.7 × 106 seeds ha−1. Greatest yield for the four dates ranged from 1974 to 2675 kg ha−1. Optimum spring plant stands for attaining those yields were between 61 and 112 plants m−2, obtained at different seeding rates, depending on the date of seeding. The lowest seeding rates (0.9 and 1.5 × 106 seeds ha−1) produced optimum spring plant stands for the mid‐August and early September seeding. Higher seeding rates in early August and mid‐September were necessary to achieve optimum spring plant stands.