bluuebunny/crossref_metadata_2025 huggingface dataset:
Soybean Yield Response to Benomyl Fungicide Application under Maximum Yield Conditions
Authors: Cooper R. L.
Published: July 2010

In 1980, after three consecutive years with soybean [Glycine max. (L.) Merr.] yields in excess of 5000 kg ha−1 in surface‐irrigated, maximum yield, research plots, yields dropped to 3000 kg ha−1 due to severe development of Septoria brown spot (Septoria glycines Hemmi), which caused premature senescence and defoliation of the leaves. The purpose of this research was to determine the effect of benomyl [methyl‐l‐(butylcarbamoyl)‐2‐benzimidazole carbamate] control of natural infection of foliar diseases, primarily Septoria brown spot, on the yield of irrigated, high‐yield soybean. Benomyl was applied at a rate of 2.2 kg ha−1 at 2‐wk intervals beginning in mid July (late flowering stage, R2‐R3) with the last application in early September (late pod fill stage, R6). Two determinate semidwarf cultivars, Hobbit and Sprite, and two indeterminate cultivars, Pella and Williams 82, were grown in two row spacings, (75 and 17 cm) and compared with and without benomyl treatment for 3 yr. Averaged across the 3 yr, the determinate cultivar, Hobbit, and the indeterminate cultivar, Pella, were the most yield responsive to benomyl treatment (15.4 and 7.7% in 75‐cm rows and 13.8 and 15.5% in 17‐cm rows, respectively). The determinate cultivar, Sprite, and the indeterminate cultivar, Williams 82, failed to show a significant yield increase from benomyl treatment. These results indicate that yield reductions due to Septoria brown spot vary by genotype, but are not associated specifically with plant type (determine vs. indeterminate). Yield increases from benomyl treatment tended to be greater in 17‐cm row width than in 75‐cm row width. This research indicates that control of foliar diseases, such as Septoria brown spot, can significantly increase the yield potential of high yielding soybean under conditions of frequent wetting of the foliage, either by frequent rainfall or irrigation, and should be an important component of a maximum‐yield research or production system.
Mineral Concentrations in Whole Crop and Pressed Forage of Three Legumes
Authors: Collins Michael
Published: July 2010

Mechanical dewatering of fresh herbage produces a pressed forage (PF) suitable for ensiling without field drying. A 2‐yr field experiment was conducted to compare concentrations of minerals in initial whole crop (WC) and pressed forage of alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), and birdsfoot trefoil (Lotus corniculatus L.) harvested at four first‐harvest maturity stages. Plots of each species were grown on Plano silt loam soil (fine‐silty, mixed, mesic Typic Argiudolls) and were harvested beginning 1 wk after early bud and continuing at 1 wk intervals for 4 wk. Pressed forages of all species were lower in P, K, Ca, and Mg than their respective WC. Potassium decreased the most and, averaged over all species, was 26.5% lower in the PF. Pressed forages averaged 21% lower in Mg than the WC, but remained above the critical concentration of 2.0 g kg−1 at all maturity stages. Pressed forage from the most mature alfalfa and red clover had P concentrations insufficient for some classes of livestock. Pressing and shoot maturation reduced S concentrations of all species, but pressing affected S more in alfalfa than in the other species. Alfalfa, red clover, and birdsfoot trefoil N/S ratios differed widely and averaged 11.8, 14.7, and 17.7, respectively. Pressed forages from the last two harvest dates had higher N/S ratios that WC from the same harvests. Pressing significantly reduces P, K, Ca, and Mg concentrations in alfalfa, red clover, and birdsfoot trefoil and, with the exception of red clover, reduces S concentration. Pressing effects on mineral concentrations vary across minerals and legume species.
Automated Quantification of Roots Using a Simple Image Analyzer
Authors: Harris Grant A. , Campbell Gaylon S.
Published: July 2010

Manual methods for estimating root lengths in washed samples are time consuming, tedious, and subjective. The objective of this research was to evaluate the use of an inexpensive commercial image analysis system for measuring the length of roots in samples washed from soil. The analyzer consists of a high‐resolution television camera and a comparator, which measures the intersections of the TV scan lines and roots in the view area. Mathematical corrections are derived for overlapping roots in the sample and for limitations in system resolution. Errors due to nonrandom orientation of roots were minimized by scanning in two directions. Methods for contrast and light control are discussed. On a 1000 cm simulated root sample, the uncorrected length measurement was < 50% of the actual length. Correcting for overlaps increased the measured length to around 70% of actual length. Overlap and resolution correction resulted in errors less than 5%. Coefficients of variation (CV) for repeated measurements on a single, undisturbed wheat (Triticum aestivum L.) root sample were around 0.5%, while errors resulting from nonrandom dispersion of samples in the tray were 2‐3%. The image analysis system therefore appears to capable of providing reliable root measurements.
Row Spacing and Plant Population Effects on Yield Components of Soybean
Authors: Ethredge W. J. , Ashley D. A. , Woodruff J. M.
Published: July 2010

Information is needed to characterize soybean [Glycine max (L.) Merr.] plant responses where cultural practices and environmental conditions are maintained at a level conducive to high yield. Field studies were conducted in 1985 and 1986 to determine the effect of row spacing and plant population on seed yield and yield components of soybean. Two determinate Maturity Group V cultivars, Essex and Deltapine 105, were grown at three row spacings of 25, 51, and 76 cm and three plant populations of 260 200, 390 400, and 520 400 plants ha−1. Seed yield was significantly higher in narrow rows (25 and 51 cm) than in the wide rows (76 cm) with the 25‐cm row spacing averaging 10% higher than the 76‐cm row spacing (3740 vs. 3361 kg ha−1). There was a row spacing × cultivar interaction due mainly to a greater reduction in seed yield of Essex than Deltapine 105 as row width increased. Weight of aerial plant parts during the mid seed‐fill growth period (R5) increased with decreasing row spacings. Plant number in plots with 76‐cm row spacing decreased approximately 23% between planting and harvest whereas, the plant number in 51‐ and 25‐cm row spacings decreased only 7 and 3% respectively during the growing season. Seed yield per plant was most uniform at the 25‐cm row spacing and became more variable as row width increased
Warm‐Season Grass Diversity in Yield, Plant Morphology, and Nitrogen Concentration and Removal in Northeastern USA
Authors: Jung G. A. , Shaffer J. A. , Stout W. L. , Panciera M. T.
Published: July 2010

Six genera of warm‐season grasses were grown in Pennsylvania for 9 yr on a fine‐loamy, mixed mesic, Aquic Fragiudult, to determine their potential as forage grasses on droughty sites. Effects of applied N on yield, plant morphology, and N composition of forages were studied during Years 4 through 7, when N was applied to half of each plot area. Big bluestem, Andropogon gerardii Vitman, and switchgrass, Panicum virgatum L., showed much cultivar variation in stand development, whereas asiatic bluestem, Bothriochloa spp., and indiangrass, Sorghastrum nutans (L.) Nash, developed productive stands in one season. Mean yield of ‘NJ 50’ switchgrass was higher than that of all other grasses, yield of ‘Niagara’ big bluestem was higher than that of other big bluestems, and yield of ‘Ky 591’ indiangrass was higher than that of other indiangrasses. The percentage of grasses showing a yield response to applied N increased each year, from 32% in 1981 to 67% in 1984. Mean yield response to N varied greatly among cultivars, P < 0.001. Nitrogen concentration in forage varied among bluestems and indiangrasses, but not among switchgrasses. Mean N removed in first‐harvest forage ranged from 16 kg ha−1 yr−1 for untreated ‘Plains’ asiatic bluestem to 97 kg ha−1 yr−1 for N‐treated NJ 50 switchgrass. Flowerstem density and height were affected differently by N, depending upon plant species and cultivar. The sheath‐stem component of dry matter yield was 60 g kg−1 higher when N was applied than when no N was applied. In the ninth year, approximately one‐half of the cultivars had stand ratings exceeding 80% ground cover.
Narrow‐Row Seed‐Yield Enhancement in Determinate Soybean
Authors: Board J. E. , Harville B. G. , Saxton A. M.
Published: July 2010

Although many studies have been conducted to determine the effect of narrow vs. wide rows on determinate soybean [Glycine max (L) Merr.] yield, little information is available explaining why these yield responses occur. This research was conducted to determine the roles of reproductive partitioning, light interception duration (LID), and total dry matter duration (TDMD) between emergence to R5 (E‐R5) and R5 to R8 on narrow‐row seed‐yield enhancement. Field studies were conducted using normal and late planting dates, two commercial soybean cultivars, and 100‐ (wide) and 50‐cm (narrow) row spacings during 1987 and 1988 at Baton Rouge, LA on a Mhoon silty clay (fine‐silty, mixed, nonacid, thermic Typic Fluvaquent) soil, Significant narrow‐row seed‐yield enhancement occurred from both planting dates, but the increases were much larger at the late date. In the normal planting, seed yield was strongly correlated with LID (R5‐R7) (r2 = 0.77, P = 0.001) and TDMD(R5‐R8) (r2 = 0.86, P = 0.001), but not LID(E‐R5) or TDMD(E‐R5). In the normal planting, significant narrow‐row seed‐yield enhancement occurred only in cases in which narrow rows achieved 95% light interception before pod filling, but wide rows did not. In contrast, seed yield in the late planting was highly correlated to LID(E to R5) (r2 = 0.85, P = 0.001) and TDMD(E‐R5) (r2 = 0.81, P = 0.001), as well as LID(R5‐R7) (r2 = 0.98, P = 0.001) and TDMD(R5‐R8) (r2 = 0.94, P = 0.001). Although narrow‐row yield enhancement in the late planting was greatest when LID and TDMD were stimulated both before and after R5, significant yield increases in narrow versus wide rows occurred even in cases in which LID R5 to R7 differences were too small to affect TDMD(R5‐R8). In conclusion, narrow‐row seed‐yield enhancement of late plantings was influenced by increased LID and TDMD throughout the season, whereas only LID and TDMD enhancement during pod filling of normal plantings affected narrow‐row seed‐yield increases.
Within‐Row Spacing Influences on Diverse Sorghum Genotypes: I. Morphology
Authors: Caravetta G. J. , Cherney J. H. , Johnson K. D.
Published: July 2010

Plant morphology influences forage quality. Plant population has been shown to influence sorghum [Sorghum bicolor (L.) Moench.] morphology, but morphology also is affected by the genetic diversity in sorghum. Our objective was to determine changes in morphology of four diverse sorghum genotypes as influenced by within‐row spacing. Four sorghum genotypes (IS‐0469, IS‐0865, IS‐954063, and IS‐2952) designated G1, G2, G3, and G4, were sown at five within‐row spacings of 5, 10, 15, 30, and 60 cm at two field locations in 1986 and 1987. Differences among genotypes and within‐row spacings were significant (P > 0.05) for most morphological characteristics. Number of shoots per plaint increased as within‐row spacing increased by 4.8 shoots plant−1 for G1, compared to an increase of only 1.6 shoots plant−1 for the genotype with the lowest tillering potential (G3). Shoot diameter also increased 53.2% and 128.9% for main shoot and tillers, respectively, averaged over genotypes as within‐row spacing increased. As within‐row spacing increased from 5 to 60 cm, height declined from 2.0 to 1.7 m, across genotypes. As within‐row spacing imcreased from 5 to 60 cm, leaf/steam ratio increased linearly from 0.9 to 1.2 across genotypes. Morphological characteristics responded in varying degrees to changes in within row spacing, and were Significantly influenced by genotype. Increased within‐row spacing: resulted in increased light penetration and reduced within‐row competition. Consequently, sorghum morphology was altered through changes in within‐row spacing and these changes were influenced by genetic diversity among sorghum genotypes. Breeders selecting for forage quality in diverse sorghum genotypes need to be aware of plant population effects on morphology.
Mineral Concentrations in Alfalfa and Sainfoin as Influenced by Soil Moisture Level
Authors: Kidambi S. P. , Matches A. G. , Bolger T. P.
Published: July 2010

Information on the influence of soil moisture on mineral concentrations and their associative relationships, is limited in alfalfa (Medicago sativa L.) and is lacking in sainfoin (Onobrychis viciifolia Scop.). The objectives of our study were to determine the influence of soil moisture level on (i) the concentrations of Ca, Mg, K, P, Cu, Zn, and Ca/P ratio, and (ii) the magnitude and relationship of correlation coefficients among mineral concentrations and the Ca/P ratio in alfalfa and sainfoin. Both ‘Renumex’ sainfoin and ‘Cimarron’ alfalfa were seeded in rows on an Acuff loam (fine‐loamy, mixed thermic Aridic Paleustalf) soil, under a line‐source irrigation system. Alfalfa and sainfoin were harvested six and four times during 1986, and six and five times during 1987, respectively. There was an increase in the concentrations of Ca, Mg, and Zn in both species, and P in alfalfa with decreasing soil moisture supply. Sainfoin had approximately 0.3 g kg−1 higher Mg and P concentrations than alfalfa, but lower concentrations of Ca and K (1.9 and 8.5 g kg−1 lower, respectively). Both species had a similar Ca/P ratio (approx. 3.3:1). Alfalfa had 2.35 mg kg−1 higher Cu and 1.95 mg kg−1 lower Zn concentrations than sainfoin. There was little influence of soil moisture level on the direction or magnitude of the correlation coefficients among the minerals in both species. Our results indicated that soil moisture level affected the mineral concentrations but not the relationships among minerals in the forage of alfalfa and sainfoin.
Root Temperature and Calcium Level Effects on Winter Wheat Forage: I. Shoot and Root Growth
Authors: Miyasaka S. C. , Grunes D. L.
Published: July 2010

Wheat pasture poisoning is a metabolic disorder of ruminants, that occurs particularly in the spring, during a sudden spurt in plant growth, under conditions of optimum temperature, ample soil moisture and adequate mineral supply. To determine the effects of an increase in root temperature and four Ca levels on the shoot and root growth of winter wheat (Triticum aestivum L. ‘Centurk’), seedlings were grown under three root temperature regimes (constant 8 °C, constant 16 °C, and increasing from 8‐16 °C), in nutrient solutions with four Ca levels (0.2,0.6,2.0, and 5.0 mM). No significant differences due to Ca levels were found for growth rates of the shoots and roots (dry weight basis), nor for root extension rates. Growth rates of the shoots and roots (dry weight basis), and root extension rates were significantly slower for plants grown at 8 °C compared to those grown at 16 °C. Lateral root growth, in particular, was depressed in plants grown at a cold root temperature. The mean root diameter was significantly greater at 8 °C than at 16 °C, apparently due to the greater proportion of main root axes with larger root diameters at a cold root temperature. Plants transferred to 16 °C had growth rates of the shoots and roots that were intermediate, relative to those grown at constant low or constant high root temperatures. A lag period of 1 wk was observed before shoot and root dry weights of plants transferred to 16 °C increased, compared to those maintained at 8 °C. Thus, root temperatures play a major role in modifying shoot and root growth parameters.
Vegetative Establishment of Dwarf Elephantgrass: Effect of Defoliation prior to Planting Stems
Authors: Sollenberger L. E. , Jones C. S. , Albrecht K. A. , Ruitenberg G. H.
Published: July 2010

Cattle (Bos spp.) gains on ‘Mott’ dwarf elephantgrass (Pennisetum purpureum Schum.) have averaged 1 kg d−1 during 3 yr of summer grazing in Florida, but vegetative establishment of this cultivar has been problematic. The objective of this research was to determine the effect of defoliation prior to harvesting stems for vegetative planting on number of shoots produced, percentage of planted stems producing shoots, and shoot and root dry matter (DM) accumulation during 6 wk postplant. Responses were quantified for mid‐ and late summer planting dates in 2 yr on a Smyrna sand (sandy, siliceous, hyperthermic Aeric Haplaquods). Previously undefoliated plants were (i) grazed to remove 70 to 90% of leaf blade (grazed), (ii) grazed to remove the apical meristem and leaf blade of individual stems (meristem), (iii) not grazed, but leaf blades were stripped manually from stems (stripped), (iv) not grazed, but all herbage above the collar of the most recently expanded leaf was clipped manually (topped), or (v) not defoliated (undefoliated). More shoots emerged per row from undefoliated stems than from all other treatments except topped. Defoliation had no effect on percentage of planted stems that produced at least one shoot. Shoot DM was greater for undefoliated than for all but stripped stems, and root DM was greatest for undefoliated stems. Stems from the meristem treatment initiated shoot but not root growth during the first 2 wk postplant, and shoot and root DM production was low through 6 wk. Undefoliated stems produced little shoot DM by 2 wk, but root growth started soon after planting. Root and shoot growth responses were consistent with theories regarding apical dominance and auxin effects on early plant development from stem cuttings. Results suggest that successful establishment of Mott elephantgrass is most likely if undefoliated stems are planted.
Overcoming the Inflexibility of Most‐Probable‐Number Procedures
Authors: Woomer Paul , Bennett James , Yost Russell
Published: July 2010

The design of most‐probable‐number (MPN) experiments is restricted by the availability and completeness of tables for certain dilution ratio and replicate number combinations. The results presented in this paper are from a computer program, the Most Probable Number Enumeration System (MPNES), which generates solutions and confidence limits (P = 0.05) for population estimates of MPN data. Tables generated by MPNES agreed with existing tables yet MPNES was able to generate other tables and discrete solutions for design combinations that have not been published. The program was also used to generate population estimates from fractional base dilution ratios. The MPNES increases the accuracy of MPN estimates by decreasing the base dilution ratio, by increasing the number of replicates per dilution or by correcting for constantly inaccurate diluent volumes. The MPNES program also adjusts for inoculation volume and initial dilution ratios. In this way, MPN experiments can be designed to better measure the organism of interest rather than have the design dictated by published tables.
Responses of a Perennial Grass‐Legume Mixture to Applied Nitrogen and Differing Soil Textures
Authors: Kanyama‐Phiri G. Y. , Raguse C. A. , Taggard K. L.
Published: July 2010

Sustained productivity in multiple‐species, perennial grass‐legume pastures depends in part on achieving and maintaining an appropriate species (SP) balance. Nitrogen levels for the grass component and consistent opportunity for rooting and nodulation of new legume stolons are important. Using an outdoor pot experiment, this study investigated perennial regrowth responses of orchardgrass (Dactylis glomerata L.), perennial ryegrass (Lolium perenne L.), ladino clover (Trifolium repens L.) and strawberry clover (T.fragiferum L.) to differing soil textures (ST) obtained by addition of sand and peatmoss, together with N in split applications of 60 kg ha−1 to provide rates of 60,120, and 180 kg ha−1. Of particular interest were maintenance of a favorable (e.g., 1:1) grass‐legume balance and identification of the effects of alteration in ST on legume root and nodule development (RND). The four SP were established as split plots of transplanted propagules on whole plots of N and ST treatments in a completely random design. At 30‐d intervals dry matter (DM) was sampled for each species. Legume stolons were observed for leaf appearance rate (LAR) and were subsampled once during the 120‐d experiment to determine RND. Differences in soil texture had no significant influence (P > 0.05) on DM yields or on legume LAR or RND, but significant (P < 0.001) effects on DM were observed for N and SP and for N × SP interactions. Increasing N significantly (P < 0.05) reduced LAR and RND. Percent N recovery was highest (72%) at 60 kg ha−1 N but legume dominance was avoided only at 180 kg ha−1 N, (N recovery = 12%). Successive split applications of N are useful in managing grass‐legume balance and DM yield in closely‐grazed perennial pastures, but at N levels effective in achieving these objectives a low recovery of applied N is likely.
Greenhouse Evaluation of Simulated Injected Liquid Beef Manure
Authors: Sawyer J. E. , Hoeft R. G.
Published: July 2010

In response to observed crop production problems (uneven growth, stunting, and chlorosis) encountered when liquid manure was knife injected into soil, a greenhouse study was initiated to detemine corn (Zea mays L.) response to simulated knife (vertical) and sweep (horizontal) placement of liquid beef manure (equivalent field application rate of 37 400 L ha−1). Derinda silt loam soil (fine, mixed mesic Typic Hapludalf), 0‐ to 20‐cm depth, was collected from a field site where crop growth problems associated with knife‐injected manure had been documented by previous field research. This soil, with and without simulated manure injections, was placed into pots and incubated at 8.9, 15.6 and 22.2 °C for 3 wks. Corn was then planted and grown for 26 d in the greenhouse. At all preplant incubation temperatures, vertical placement of the manure severely reduced plant growth throughout the duration of the study. With horizontal placement, growth was reduced early after planting, but recovered as time progressed, especially at the 22.2 °C preplant incubation temperature. Reductions in plant growth were related to toxic conditions within the manure zone. Analysis of the manure zone indicated toxicity from NH3, inferred from the high pH and high concentrations of NH+4, lowered redox potential, followed by accumulation of NO−2‐ to toxic levels. Horizontal placement resulted in reduction or elimination of these toxicities, except NO−2, which had accumulated at the end of the incubation period. Because vertical placement created a more concentrated zone of manure at the point of injection than did horizontal placement, method of injection appears to dflerentially affect potential toxic conditions and resultant plant growth.
Use of Spectral Vegetation Indices to Infer Leaf Area, Evapotranspiration and Yield: II. Results
Authors: Wiegand C. L. , Richardson A. J.
Published: July 2010

Better methods of interpreting spectral observations of crop canopies in terms of agronomic characteristics such as green leaf area index (L) and aboveground dry phytomass (DM), and for estimating economic yield (Y) are needed. The equations proposed were applied to single year experiments with Triticum aestivum L. and Triticum durum Desf., Gossypium hirsutum L., and Zea mays L. in order to illustrate and further test them. As predicted, fractional photosynthetically active radiation absorption (FPAR) could be estimated from vegetation indices (VI) such as perpendicular vegetation index (PVI) and the normalized difference (ND) about as well as from L. Generally, L/VI and FPAR/L‐verbalized as L as a function of VI, and FPAR as a function of L–were exponential relations whereas FPAR/VI were linear or nearly linear functions. The DM, Y, and the harvest index (Y/DM) were linearly related to PVI averaged for several dates during late vegetative development for wheat and corn, indicating that relative yields for both crops had been set by that development stage. The functional relations L/VI, FPAR/L, FPAR/VI, Y/VI, DM/VI, ∑APAR/∑VI, DM/∑APAR, Y/∑VI and (Y/DM)/VI where APAR is daily absorbed PAR (MJ m−2 d−1) presented document that direct spectral observations and the equations incorporating them do provide additional analytical tools for interpreting crop development, growth, and yield.
Influence of Planting Date, Seeding Rate, and Phosphorus Rate on Wheat Yield
Authors: Blue E. N. , Mason S. C. , Sander D. H.
Published: July 2010

To improve management of winter wheat (Triticum aestivum L.), more information is needed on how grain yield is influenced by planting date, seeding rate, and applied P. A 3‐yr study was conducted to measure the effects of these variables on grain yield and yield components of wheat grown in low‐P soils. All soils were Crete silty clay loams (fine Montmorillonitic mesic Pachic Argiustoll) and had Bray & Kurtz no. 1 soil tests of less than 10 mg kg−1. A randomized complete block designed experiment with a split plot treatment arrangement using three planting dates (each in 1985, 1986, and 1988) as whole plots, and factorial combinations of three seeding rates and three P rates as split plots. Grain yield, spikes meter−2, kernels spike−1, and kernel weight data were collected. Relative grain yield was greatest when 400 growing degree days (GDD, 4.4 °C base temperature) accumulated between the planting date and 31 December. Increasing the seeding rate from 34 to 101 kg ha−1 resulted in yield increases of 0.39, 0.48, and 0.21 Mg ha−1 in 1986, 1987, and 1988, respectively. Increasing the P rate from 0 to 34 kg P ha−1 resulted in 0.67, 0.53, and 0.79 Mg ha−1 yield increase in 1986, 1987, and 1988, respectively. Planting date by P rate and seeding rate by P rate interactions in 1988 indicated that P reduced the negative influence of late planting and low seeding rate on grain yield. Path coefficient analysis indicated that under conditions resulting in low tiller numbers, kernel weight contributed most in yield determination, while under high tillering conditions the number of spikes meter−2 was the most important yield component. This study showed that wheat grain yields were optimized with planting dates that allowed 400 GDD accumulation before 31 December with a 101 kg ha−1 seeding rate when available soil P is sufficient.
Effect of Fertilization Method and Tillage on Nitrogen‐15 Recovery by Corn
Authors: Timmons D. R. , Cruse R. M.
Published: July 2010

Fertilizer N utilization by corn (Zea mays L.) is influenced by different fertilizer management and tillage systems. A study was conducted in central Iowa during two consecutive years to evaluate the uptake and recovery of labeled N for continuous corn grown in two tillage systems with two fertilization methods. Tillage systems were fall moldboard‐plow and ridge‐till. Labeled N (5% 15N) as 28% urea‐ammonium nitrate solution (UAN) was either surface‐applied in the fall before any primary tillage or banded (knifed‐in) between rows at 224 kg N ha−1 just before planting. Depending on tillage and fertilization method, corn grain yields ranged from 1.3 to 7.3 Mg ha−1 which were below normal due to adverse weather conditions during the two growing seasons. The percent of plant N derived from labeled N (Nf) in the sixth leaf (50% silk) and in mature grain, stover, and whole plants was significantly lower for fall surfaceapplied 15N than for spring banded 15N. For mature whole plants, Nr ranged from 9 to 59% and averaged 53% for spring banded and 17% for fall surface‐applied 15N. Labeled N recovery by mature corn grain was affected by fertilization method and growing season and ranged from 1 to 25% during the 2‐yr period. Labeled N recovery by mature whole plants ranged from 2 to 41% and averaged four times greater for spring banded than for fall surface‐applied 15N. About 1 yr after application, an average of 20% of the 15N remained in the soil profile; and 95% of the residual 15N was found in the organic N pool. Compared with spring banded N, fall surface‐applied N was extremely inefficient for both tillage systems.
Zero Flux Plane Recession under Monocropped and Intercropped Cowpea and Sorghum
Authors: Villegas A. N. , Morris R. A.
Published: July 2010

Movement of water remaining in the soil profile at harvest of rice (Oryza sativa L.) from puddled fields in the tropics has not been well documented. This water is used by crops during the dry season. To use it more effectively, however, its behavior during the postrice period must be better understood. Monocrops and intercrops of species differing in rooting habit [cowpea (Vigna unguiculata (L.) Walp.) and sorghum (Sorghum bicolor (L.) Moench)] were compared for effects on zero flux planes in an Andaqueptic Haplaquoll during three postrice seasons in the Philippines. Fallow treatments were included for comparison. Zero flux plane recession was regarded as an indicator of internal drainage. Zero hydraulic head gradients calculated from matric potentials defined the zero flux plane. In all years, the zero flux plane receded most rapidly under monocropped cowpea (to 0.9 m in 36—38 d after planting). The zero flux plane under the intercrop reached 0.9 m 7 d later. Recession under sorghum was less consistent, requiring 43 to 70 d to reach 0.9 m. Under fallow, it receded to about 0.45 m (to the Bt horizon) within 15 to 25 d and remained stationary except when a 30 mm rain 40 d after planting infiltrated and temporarily raised it to 0.3 m. Ten days later, the zero flux plane under fallow again was stationary at 0.45 m. In contrast, under cowpea the 30 mm rain infiltrated the soil under cowpea but was redistributed above the zero flux plane. Monocropped cowpea and the cowpea‐sorghum intercrop were equally effective at arresting drainage of residual water.
Improved Sap Flow Gauge for Woody and Herbaceous Plants
Authors: Steinberg S. L. , Van Bavel C. H. M. , McFarland M. J.
Published: July 2010

The internal wiring of an existing stem or trunk flow gauge was redesigned to obtain greater accuracy of the gauge itself, eliminate errors due to signal loss in connecting cables, and reduce the number of channels and of the computing required of the datalogger. Tests of the gauge conducted on bald cypress (Taxodium distichum) and Ficus retusa (L.) Nitida trees, in a greenhouse and in an urban backyard, and under well‐watered and dry conditions gave daily sap mass flow rates that were within 5% of those obtained by direct weighing.
Residual Soil Nitrogen as Affected by Continuous, Two‐Year, and Four‐Year Crop Rotation Systems
Authors: Varvel G. E. , Peterson Todd Andrews
Published: July 2010

Crop rotation systems may reduce inorganic N fertilizer needs because of increased N mineralization, but if that N is mineralized either too early or too late with respect to crop needs, it can also be susceptible to leaching. These concerns prompted an investigation of a long‐term field study at Mead, NE on a Sharpsburg silty clay loam (fine, montmorillinitic, mesic, Typic Argiudoll) to determine effects of crop rotation and N fertilizer application on residual inorganic N levels to a depth of 150 cm after 4 yr. The study included continuous corn (Zea mays L.), continuous soybean [Glycine max (L.) Merr.], continuous grain sorghum [Sorghum bicolor (L.) Moench.], corn/soybean and grain sorghum/soybean 2‐yr rotations, and corn/oat [Avena sativa (L.)] + clover [80% yellow sweetclover [Melilotus officinalis (L.) Lam.] + 20% red clover [trifolium pratense]}/grain sorghum/soybean and corn/soybean/grain sorghum/oat + clover 4‐yr rotations with three rates of N fertilizer application. High N application resulted in greater residual NO3–N concentrations for the continuous corn and grain sorghum systems than in any of the other cropping systems to a depth of 150 cm. Residual NO3–N concentrations were low (<4 mg kg−1 at depths below 30 cm) at all N application rates in continuous soybean and 2‐ and 4‐yr cropping systems. Nitrogen removal by grain accounted for 50% of the applied N in continuous corn and grain sorghum systems at the low N application rate, but only 20 to 30% of the applied N at the high rate. Likewise, only 20 to 30% of the applied N was accounted for by N removal in the rotation systems at either N aplplication rate. Indirect results from our study suggest immobilization by crop residues and soil organic matter, not leaching, is probably most responsible for apparent N losses in these cropping systems. Although the mechanisms were not specifically identified, our results do show that crop rotations can reduce inorganic N fertilizer needs and at the same time reduce the amount of N available for leaching, both of which are important to farmers in the western Corn Belt.
Matric and Osmotic Potential Effects on Seedling Emergence at Different Temperatures
Authors: Livingston N. J. , de Jong E.
Published: July 2010

Crop seeds and seedlings are exposed to drought, salinity and/or low soil temperatures in some areas. Therefore, the combined effects of these stresses on germination and emergence is of considerable interest. A growth room study was conducted to determine the effects of matric and osmotic potential at different temperatures on the rate and total number of seedling emergence for wheat (Triticum aestivum L. cv. Neepawa) and two rapeseed species, Polish type (Brassica campestris var. Tobin) and Argentinean type (B. napus var. Westar). Twenty‐four treatments [3 species ✕ 2 matric potentials (−0.02 and −0.2 MPa) ✕ 4 osmotic potentials (−0.03, −0.3, −0.6 and −1.2 MPa)], each replicated four times, were arranged in a completely randomized design in two insulated tanks through which water from a temperature regulated water bath was calculated. Temperature at seed depth (15 mm) was maintained at 3, 6, 12, and 15 °C in four separate experiments. In each treatment ten seeds were planted in a 300‐mL container packed with a sandy loam soil (Entic Haploborall) to give a density of 1.25 g cm−3. For all species time to 50% emergence (T50) increased with decreasing temperature. Polish rape (the smallest seed) emerged fastest at all temperatures and soil water potentials followed by Argentinean rape and then wheat (the largest seed). Differences between species generally became less pronounced with increasing temperature at all soil water potentials. for soils with the lowest matric potentials the relationship between t50, and total potential (ΨT) was linear and almost all the variability in t50, could be explained by changes in osmotic potential. Effects of ΨT on emergence were most pronounced at intermediate temperatures. Except for wheat at 3 °C, the rate of emergence at the lowest osmotic potential was significantly slower in wet soils than in dry soils so that there was significant deviation from the linear relationship between t50, and #x03A8;T, established for the dry soils. These results suggest that to avoid salt accumulation around seeds in saline soils it may be advantageous to delay seeding until the soil matric potential is low enough that water uptake by seeds is through vapor flow.
Water, Harvest Interval, and Applied Nitrogen Effects on Forage Yield of Bermudagrass and Bahiagrass
Authors: Overman A. R. , Neff C. R. , Wilkinson S. R. , Martin F. G.
Published: July 2010

A logistic equation was used to relate forage yield to applied N for bermudagrass [Cynodon dactylon (L.) Pers.] and bahiagrass [Paspalum notatum Flugge]. It was shown that the equation could be factored into a triple product–one term each for water availability, harvest interval and applied N. The equation provides high correlation (R ≥ 0.98) between yield and applied N for all levels of water availability and harvest interval. Appropriate statistical procedures for nonlinear regression were utilized in the analysis. These results are useful for estimating effects of management factors on forage production.
Growth, Yield, and Yield Components of Lupin Cultivars
Authors: Lopez‐Bellido Luis , Fuentes Mariano
Published: July 2010

The cultivation of Lupin, Lupinus spp., as a protein source for animal feed and as a way of improving soil fertility is of interest for crop rotation under rainfed Mediterranean climatic conditions and poor acid soils. The adaptation of a cultivar from each one of the four cultivated species of lupin: L. albus (L.), L. luteus (L.), L. angustifolius (L.), and L. mutabilis (Sweet) has been studied. A comparative analysis of their growth (dry matter, growth rates, leaf area index (LAI) and leaf area duration (LAD), yield, yield components and harvest index (HI), protein, and fat content was carried out in the Guadalquivir Valley in southern Spain on a river terrace with Haploxeralf soil and a loamy clay texture. Variations in climatic conditions markedly influenced the duration of the different growth stages, accumulation of dry matter, leaf area and yield of the different cultivars. Lupinus albus was the species best adapted to the conditions of the survey, distributing its dry matter better and showing better growth indexes and higher grain yield. Lupinus mutabilis proved to be inadvisable for autumn sowings under the ecological conditions of the area. It was sensitive to the cold during its vegetative stage and performed poorly. The values found for the L. luteus and the angustifolius cultivars were less than those registered in other areas where it is a traditional crop. Better growth and grain yield was obtained with them when emergence was in early rather than late autumn.
Planting Date and Nitrogen Rate Effects on Spring Malting Barley
Authors: Lauer Joseph G. , Partridge Jay R.
Published: July 2010

Planting date (D) and N fertilizer have been shown to significantly increase spring malting barley (Hordeum vulgare L.) grain yield and protein when grown under dryland production systems where water is limiting. This study was conducted to determine D and N rate effects on grain yield, grain protein, kernel plumpness and yield components of spring malting barley grown under a production system that minimized crop water stress. Between 1984 and 1988, ‘Klages’ barley was planted at 2‐wk intervals between 15 April and 19 May (expressed as days from 1 January) at Powell, WY on a Garland clay loam (fine, mixed, mesic, Typic Haplargid). Ammonium nitrate was applied at rates of 0, 67, 134, and 202 kg N ha−1. Early planting increased kernel weight 14% and kernel density 16% compared to late planting; spike density was not affected. Increasing N from 0 to 202 kg N ha−1 increased spike density 39% and kernel density 63%; kernel weight was not affected. Grain yield decreased from 4.7 to 4.0 Mg ha−1 with later planting date and increased from 3.4 to 4.9 Mg ha−1 as N rate increased from 0 to 202 kg N ha−1 [Grain yield (Mg ha−1) = 6.92 − 0.027(D) + 0.007(N); R2 = 0.89**, significant at P = 0.011. Grain protein was unaffected by D and increased from 102 to 121 g kg−1 as N rate increased from 0 to 202 kg N ha−1 [Grain protein (g kg−1) = 127 − 0.194(0) + 0.095(N); R2 = 0.96**]. Kernel plumpness decreased from 97 to 95% with delayed D and was unaffected by N rate [Kernel plumpness (%) = 106 − 0.076(D) − 0.005(N); R2 = 0.80**]. Spring barley grain yield and kernel plumpness response to D and N rate for furrow irrigated cropping was similar to responses for dryland cropping. However, contrary to dryland results, grain protein was not affected by D when grown with minimum water stress.
Spectral Reflectance Measurements of Alfalfa under Sheep Grazing
Authors: Mitchell A. R. , Pinter P. J. , Guerrero J. N. , Hernandez C. B. , Marble V. L.
Published: July 2010

Lamb grazing experiments conducted on alfalfa (Medicago sativa L.) fields require numerous measurements of phytomass in order to identify optimum conditions for lamb weight gain. Our objective was to test the ability of spectral reflectance measurements with a portable hand‐held radiometer to predict alfalfa phytomass. We used vegetative indices consisting of linear combinations of the near infrared (NIR) and red wavelength intervals, such as the NIR/Red ratio and normalized difference (ND). Reflectance measurements were taken during two grazing trials where alfalfa phytomass ranged from 200 g m−2 initially to negligible phytomass after 15 d of intensive grazing. A portion of the alfalfa was desiccated due to frost damage during the second trial. The ND and NIR/Red were well correlated with alfalfa phytomass (r = 0.87−0.97). Measurements taken at solar zenith angles (57 and 69°) were found to produce similar ND/phytomass regression coefficients. The desiccated alfalfa increased red reflectance, which consequently lowered the ND and NIR/Red values. The ND was preferable to NIR/Red because it was more sensitive to low phytomass levels that are characteristic of grazing studies. An ND of 0.55 identified a threshold phytomass level, below which continued grazing caused a decrease in lamb weight gain. Handheld radiometric measurements are a quick, accurate, nondestructive means of estimating alfalfa phytomass in pasture grazing experiments.
Tracing the vertical Distribution of Simulated Shattered Seeds as Related to Tillage
Authors: Staricka J. A. , Burford P. M. , Allmaras R. R. , Nelson W. W.
Published: July 2010

Weed control in conservation tillage requires a knowledge of weed seed ecology, but germination and loss of viability make it difficult to trace seed movement during tillage. Ceramic spheres were evaluated as tracers to determine the effects of chisel and moldboard tillage on the vertical distribution of shattered seeds. Tracers and seeds of foxtail millet (Setaria italica [L.] Beauv.) were applied to the soil surface [Ves loam (a fine‐loamy, mixed, mesic Udic Haplustoll)] before fall primary tillage with a chisel or moldboard plow. Soybean (Glycine max [L.] Merr.) and oat (Avena sativa L.) were grown in a strip‐plot design. Soil cores (18 mm diam.; 60 cm deep) were taken midsummer, sectioned into 2‐cm increments, and composited (12‐15 cores per sample) by depth. Soil bulk density, seed counts, and tracer counts were recorded for each sample. Seeds and tracers were found to depths of 12 cm in the chisel plots and 32 cm in the moldboard plots. In the chisel plots, 51 and 48% of the seeds and tracers, respectively, were found within 4 cm of the surface compared to 11 and 4% for the moldboard plots. Germination of applied seeds was greater in the chisel plots whereas germination of indigenous seeds (previously buried by tillage) was greater in the moldboard plots. An abrupt increase in the soil bulk density occurred at the penetration depth of the primary tillage operation and coincided with the maximum burial depth of seeds and tracers. These observations verify the differences in working depth and associated seed placement by the two implements. Ceramic spheres can trace the vertical distribution of shattered seeds related to tillage.
Using Upper‐Bound Slope Through Origin to Estimate Genetic Harvest Index
Authors: Prihar S. S. , Stewart B. A.
Published: July 2010

Harvest index (HI), the ratio of grain to abovegronnd dry matter, is reported to be a species‐related parameter and is recommended for screening cultivars. But the fact that it is affected by environmental stress limits its use for intercrop or intercultivar comparisons. Fair comparisons should be based on estimated genetic HI for a given environment, but a procedure to determine the same is lacking. We propose that the slope of an upper‐bound in the grain yield vs. dry matter plot passing through the origin approximates the genetic HI because the highest grain yields against given dry matter represent the least‐stressed and/or stress‐adapted plants and passage of the line through the origin is necessary to satisfy the definition of HI. This HI also provides a useful reference for interpreting agronomic data with respect to stress effects associated with management practices. The HIs of sorghum [Sorghum bicolor (L.) Moench], corn (Zea mays L.), and wheat (Triticum aestivum L.) were estimated by the upper‐bounds of grain yield (corrected to dry weight) vs. dry matter yield taken from existing reports in the literature. Harvest index of sorghum and irrigated corn ranged between narrow limits of 0.48 to 0.53 and 0.58 to 0.60, respectively. Harvest index of irrigated wheat ranged from 0.38 to 0.47. Stress effects on HI are illustrated in plots of published and unpublished (dry) grain yields vs. dry matter yields and reasons for the same are discussed.
Long‐Term Ecological Research in Temperate and Boreal Forest Ecosystems
Authors: Powers Robert F. , Van Cleve Keith
Published: July 2010

Forest ecosystems are distinguished by their complexity and diversity, their progressive nature of development, and the constant risk of random catastrophes. These systems develop relatively slowly, and research conducted on them requires years or decades to yield meaningful findings with broad extension. Prolonged development, coupled with uncertainty about disruption, work against long‐term commitment to fund and maintain study sites. Alternative research strategies (chronosequence and retrospective studies) produce rapid results, but are marred by limited application and uncertainty about past events. With notable exceptions, most long‐term studies have centered on relatively undisturbed natural ecosystems. While such studies are useful, they lack the flexibility needed to gauge the long‐term impacts of manipulation. New programs, such as the National Science Foundation's network of Long‐Term Ecological Research sites, and the USDA Forest Service's Long‐Term Soil Productivity studies, encompass and support a wider range of objectives and variables than was possible in earlier studies.
Potential for Using Long‐Term Field Research Data to Develop and Validate Crop Simulators
Authors: Acock Basil , Acock Mary C.
Published: July 2010

At the time when many long‐term field experiments were initiated, the principal method of analyzing crop yield data was to use multiple regression analysis. This technique is based on the assumption that the interacting effects of environmental factors on plants can be described with empirical additive or multiplicative models. We now know that such models do not adequately describe the interactions between factors. In the early days of agricultural experimentation, when gross nutrient deficiencies in soils were being corrected, the exact form of the model did not matter much. Now, with soil nutrient levels near optimum, additional (plant and weather) factors have to be considered in our analysis and our models must deal with the interaction between all factors realistically. The most realistic way of considering how a large number of factors affect plants is to use a limiting factor model. This enables us to develop mechanistic crop models (simulators) that simulate many of the processes going on in the plant, soil, and atmosphere. However, the validation of crop simulators requires more types of data than does the development of empirical models. Many of the data used to develop crop simulators come from studies in controlled‐environment plant growth chambers, where environmental factors can be manipulated independently. However, it is widely recognized that plants grown in chambers differ from those in the field, and model parameters often have to be adjusted to fit field data. Thus, field data are essential to the final stages of model development and validation. Long‐term field research is especially useful because: (i) it provides data in which some environmental factors are constant over time, and observed effects can be attributed to uncontrolled factors, and (ii) it provides data in which the unknown effects of previous treatments have been minimized. Despite these advantages, long‐term field data have rarely, if ever, been used in the development and validation of crop simulators. Modelers would benefit from working more closely with scientists running long‐term field experiments, showing then what additional types of data are needed and how existing crop simulators can be used to interpret results.