bluuebunny/crossref_metadata_2025 huggingface dataset:
Nutritional Quality of Vegetable Crops as Affected by Phosphorus and Zinc Fertilizers1
Authors: Peck N. H. , Grunes D. L. , Welch R. M. , MacDonald G. E.
Published: July 2010

The nutritional quality as well as the yield of the portions of vegetable plants used for human consumption should be considered in fertilization programs.

The purpose of this study was to Determine the effects of rates of concentrated superphosphate and zinc sources on some nutritionally important factors including the concentration of P, Zn, phytic acid (myoinositol hexaphosphoric acid), and oxalic acid in the edible portions of four vegetables. The plants, pea (Pisum sativum L.), snap bean [Phaseolus vulgaris (L.) var. humilis], cabbage (Brassica oleracea var. capitata), and table beet (Beta vulgaris L.) were grown on a Honeoye fine sandy loam (Glossoboric Rapludalf, fine loamy, mixed mesic) derived from calcareous glacial till. These crops were fertilized with concentrated superphosphate (CSP) at rates of 0, 30, 60, and 120 kg P/ha, and ZnSO4 or ZnCl2 at rates of 0, 5, 20, and 80 kg Zn/ha applied in a band at planting time in a factorially designed experiment. The plants were sampled at processing stage except that pea and snap bean seeds were also sampled at full maturity. Increasing fertilizer CSP rates increased yields and P concentrations in all crops. Fertilizer CSP increased phytic acid concentrations in immature and mature pea seeds and in mature snap bean seeds. Oxalic acid concentrations in table beet plants decreased with increasing rates of CSP fertilizer. Fertilizer CSP without Zn fertilizer decreased Zn concentrations in the plants, but CSP with Zn fertilizer generally increased Zn concentrations. Fertilizer Zn did not affect yields nor cause visible plant toxicities. However, Zn fertilizer increased Zn concentrations in the plants, especially when applied with high rates of CSP fertilizer. Thus, CSP fertilization without Zn fertilization of vegetable crops can reduce their nutritional quality by lowering their Zn concentrations. However, the concomitant use of Zn fertilizer, with high rates of CSP fertilization, can improve the nutritional quality of vegetable crops with respect to Zn.
Response of Maize Inbred Lines to N Fertilizer1
Authors: Balko L. G. , Russell W. A.
Published: July 2010

Maize (Zea mays L.) inbred lines are the parents of single‐cross hybrids, yet few studies have been reported with inbred lines as the experimental material in N fertilizer studies. The genetic materials in this field study were 10 inbred lines. The objectives were to determine: 1) inbred line response to sidedress N fertilizer, 2) rate of N for maximum grain yield, and 3) inbred line response to N‐fertilizer treatments. The N treatments were: check (0 kg/ha), three levels of preplant broadcast (60, 120, and 180 kg/ha), and three levels of preplant‐sidedress (30‐30, 60‐60, and 90‐90 kg/ha). Soil types involved were Typic Haplaquolls and Cumuli Haplaquolls. Data were obtained for 12 plant, ear, and grain traits in four environments. Growth conditions differed greatly among the environments. There was no yield response in one environment, a small response in two environments, and a large response in one environment. Generally, the greatest yield response was for the first N increment (60 kg/ha), and only in the environment with the greatest response did further N increments give important yield increases. The preplant vs. preplant‐sidedress comparison showed no significant yield differences in any environment. In the environment that had the greatest response to N treatments, there were significant differences among the inbred lines; i.e., a significant inbred × N interaction was observed. One line had no response, five lines had significant linear responses, and four lines had significant quadratic responses. Ear length, ears per plant, and kernel weight were the most important yield components, but the relative importance of these components varied among the inbreds. Effects of N treatments generally were of no practical importance for plant and ear height, but pollen shed and silk emergence were significantly earlier in the environment with the greatest yield response.
Influence of Fungicide and Insecticide Applications on Persistence of Ladino Clover1
Authors: James J. R. , Lucas L. T. , Chamblee D. S. , Campbell W. V.
Published: July 2010

Ladino clover (Trifolium repens L.) is the most important perennial forage legume grown in North Carolina; however, stands often begin to decline within 2‐3 years after seeding. An entomological‐pathological complex has been reported as a major cause for decline of ladino clover. The objectives of this study were to determine the influence of benomyl [methyl l‐(butylcarbamoyl)‐2‐benzimidazolecarbamate] and carbofuran (2, 3‐Dihydro‐2, 2‐dimethyl‐7‐benzofuranyl methylcarbamate) applications on disease and/or insects which influence persistence of ladino clover.

The percent ground cover of ladino clover in control, benomyl, carbofuran, and carbofuran plus benomyl treated plots after 3‐1/2 years was 12, 24, 75 and 88%, respectively. Plants treated with carbofuran had less root injury from the clover root curculio (Sitona hispidula Fab.) than fungicide and check plots. Carbofuran and carbofuran plus benomyl applications decreased root and stolon rot and increased yield and persistence of ladino clover. None of the treatments significantly increased tap root longevity. Insect damage and root and stolon rot were highly correlated in plant samples collected throughout the experiment. Results indicate that a pathological‐entomological complex is a major factor involved with lack of persistence of ladino clover.
Moisture‐Sensitive Growth Stages of Dwarf Wheat and Optimal Sequencing of Evapotranspiration Deficits1
Authors: Singh S. D.
Published: July 2010

Careful management of a limited water supply would require that unavoidable water deficits coincide with growth stages which influence grain yield the least. This study was conducted to quantify moisture‐sensitive growth stages of wheat (Triticum aestivum L.) grown in a coarse loamy Typic Camborthid soil. Treatment variables were water, N and seeding rate. Each variable had five coded levels: −1.682, −1, 0, 1, and 1.682. A central composite rotatable design was used. Parameters included initial soil water, irrigation depth, periodic as well as seasonal evapotranspiration (ET), and grain yield (Y). For ordering the relative sensitivities of growth stages, Y and ET data from those plots were considered in which N and seeding rate were at code O, least limiting to yield. The Y and ET from the plot with 1.682 coded level of water were taken to represent maximum yield (Ym) and maximum ET (ETm,), expressed as (100, 100). All data points below Ym and ETm were considered to represent the lower level of Y and ET. Actual evapotranspiration (ETa); deficit intensity, expressed as % of ETm by which ETa fell short in a time period; and its interrelations to yield responses were sequenced for three selected growth stages: vegetative, booting/heading, and flowering to grain formation. The Y response to evapotranspiration deficit (ETd) timings was expressed as the ratio of percent yield reduction to percent seasonal ETd. The reduction in Y refers to the actual yield (Ya) as percent of Ym.

The ETd sequences produced two ranges of percent Y reduction/percent seasonal ETd ratio. Low ratios of 0.2 to 0.7 denoted the “optimal” timing of ETd, since mean yield reduction was small, 17%. Large ratios of 1.0 to 1.2 represented “suboptimal” timing of ETd, which brought about 51 to 78% Y reduction. Within the range of optimal ETd sequence, the Y reduction versus ETd relation was linear. This relationship yielded a dimensionless slope to the order of 1.29, which being constant can be used for prediction of Ya if Ym is known. Without prior ETd in the vegetative stage, wheat yields were sensitive to water deficit during the critical booting/heading period but were relatively insensitive when the plants were conditioned to some 15% moisture stress in the vegetative stage. This led to the conclusion that in relation to wheat grain yields if water is limited, the deficits should be spread nearly evenly over the previous growth stages and the critical stage.
Nitrogen Uptake by Spring Wheat, Soil Distribution, and Recovery of N Fertilizer from Alternate Crop‐fallow and Recrop Field Management Systems1
Authors: Jones A. J. , Skogley E. O. , Meints V. W. , Martin J. M.
Published: July 2010

Knowledge of N fertilizer utilization, movement, and recovery is required to attain maximum efficiency of applied N when shifting from fallow to recrop management. Field experiments involving spring wheat (Triticum aestivum) were established at two locations with different soil and climatic regimes in southwest Montana on fields which had been fallowed (fallow) or cropped (recrop) the previous year to evaluate the uptake, leaching, and recovery of 15NH415NO3 fertilizer. Ammonium nitrate fertilizer was applied to these fields at rates of 30, 60, and 90 kg N/ha under dryland conditions. The fallow and recrop fields had high (greater than 100 kg/ha/120 cm depth) and low (less than 50 kg/ha/120 cm depth) levels of nitrate‐N at seeding, respectively.

The N content of grain was 48% greater on recrop than on fallow with higher N content associated with higher rates of N fertilizer. The N content of straw showed trends similar to that for grain. In addition, increased translocation of N from straw to grain was associated with recropping and increased rates of N fertilizer. The proportion of N in the plant derived from fertilizer averaged twice as great on recrop as on fallow and increased 2‐ to 20‐fold with the addition of 90 kg N/ha. These responses reflected the variation in initial NO3‐N level of each field.

Residual NO3‐N and total 15N levels in the soil at harvest were low and decreased with depth to 120 cm. Soil NO3‐N levels ranged from 5 to 15 kg/ha. Maximum recovery of N fertilizer was at the soil surface with little difference between fallow and recrop. No leaching below 120 cm was indicated. Total recovery of N fertilizer ranged from 45 to 90%. Overall there was 18% more N fertilizer recovered on recrop than on fallow. For each component, grain, straw, and soil, there was 22, 8, and 20% respectively more N fertilizer recovered on recrop than on fallow. Total recovery of N fertilizer varied from 67 to 77% for the rate of N applied. Grain and straw N recovery increased significantly with increasing N rate while soil recovery was highly variable.
Grain Protein Content as an Indicator of N Sufficiency for Winter Wheat1
Authors: Goos R. J. , Westfall D. G. , Ludwick A. E. , Goris J. E.
Published: July 2010

A great majority of the dryland winter wheat (Triticum aestivum L.) producers in the west central Great Plains currently do not use soil tests to determine N fertilizer needs although most producers have grain protein data from their fields. Field experiments with N rate as the variable were conducted throughout eastern Colorado over a 4‐year period with winter wheat grown under summer fallow cropping. The objective was to determine if grain protein content could be used as a post‐harvest indicator of sufficiency of N for maximum grain yield. The soil types were of the Paleustoll, Argiustoll, Paleargid, and Haplargid great groups. The yield and protein response data from the experimental locations were analyzed by an interaction chisquare procedure.

Grain protein content was found to be an effective post‐harvest indicator of N nutrition adequacy for grain production. Both a critical level and a transitional zone of grain protein content were defined using interaction chi‐square analysis. The most critical level was determined to be 11.5% protein and the transition zone between the deficient and N sufficient populations of yield observations was between 11.1 to 12.0%. The amount of yield lost to N deficiency was not related to grain protein content. Workers in other geographic areas should be able to take existing N response data and develop similar guidelines appropriate for those areas.
Corn and Soybean Response to Allelopathic Effects of Weed and Crop Residues1
Authors: Bhowmik P. C. , Doll J. D.
Published: July 2010

Many crop plants and perennial weed species have been known for their allelopathic effects. The question of whether annual weed species can be allelopathic remains unanswered. Consequently, studies were conducted in laboratory, greenhouse, and in the field to determine the allelopathic potential of weed and crop residues (above ground biomass) on corn (Zea mays L.) and soybeans [Glycine max (L.) Merr.]. Water extracts of dried residues of common lambsquarters (Chenopodium album L.), redroot pigweed (Amaranthus retroflexus L.), fall panicum (Panicum dichotomiflorum Michx.), giant foxtail (Setaria faberi Herrm.), green foxtail [Setaria viridis (L.) Beauv.], and yellow foxtail [Setaria glauca (L.) Beauv.] inhibited radicle elongation in corn; whereas, only common lambsquarters extract reduced coleoptile growth. Redroot pigweed, fall panicum, and green foxtail extracts inhibited hypocotyl elongation in soybeans. Residues of common ragweed (Ambrosia artemisifolia L.), velvetleaf (Abutilon theophrasti Medic.), and barnyardgrass [Echinochloa crus‐galli (L.) Beauv.] as well as the above species inhibited corn and soybean growth in the greenhouse. Inhibition of the receiver species (corn and soybeans) was greater with the double‐pot watering method than subsurface and surface watering methods. Corn was inhibited most in silica sand, less in a silica sand and silt loam mixture (Typic Agriudoll fine, silty, mixed mesic), and least in silt loam soil under each method of watering. In the field, residues of barnyardgrass and giant foxtail reduced corn yield. Soybean yield reductions occurred ranging from 14 to 19% with common lambsquarters, redroot pigweed, velvetleaf, soybeans, and sunflower (Helianthus annuus L.) residues. Corn and giant foxtail residues enhanced soybean yield in the field. These results demonstrate the allelopathic potential of the residues and suggest that these residues may affect crop yields due to the inhibitory or stimulatory effects of allelochemicals present in the residues.
Estimation of Nitrogen Fixation by Isotope Dilution in Field and Greenhouse Experiments1
Authors: Broadbent F. E. , Nakashima T. , Chang Grace Y.
Published: July 2010

Isotope dilution methodology offers the advantage of an integrative technique for measuring N2 fixation in the field, but may have limitations in grass‐legume mixtures because of the possibility of transfer of fixed N from legume to grass. A study was conducted in the greenhouse and in the field utilizing two soils, Hanford sandy loam and Yolo silt loam (Typic Xerorthents) in which the organic matter was labeled by previous application of either 15N‐depleted or 15N‐enriched compounds. Contributions of atmospheric N2 to total plant N were calculated from the isotopic composition of plant tissue, using the composition of the non‐legume as a reference value.

Ladino clover (Trifolium repens L.) and Wimmera ryegrass (Lolium rigidum L.) were grown alone and in mixture for purposes of comparison. In the greenhouse estimation of N2 fixation by the isotope and difference methods were in good agreement. There was essentially no transfer of fixed N2 from the clover to the ryegrass in any of the pot experiments. In the field experiment, clover obtained 85 to 100% of its N from the fixation process. In the clover‐ryegrass mixture, % total N and % 15N excess comparisons both indicated substantial transfer of N from clover to ryegrass after the stand had been established after about 6 months. Up to 79% of the N in ryegrass was calculated to be derived from such transfer. It is concluded that the isotope dilution method gives estimates of N2 fixation at least as good as those obtained by yield‐dependent methods such as the difference method, but it is not suitable for grass‐legume mixtures.
Evaluating the Crop Coefficient Using Spectral Reflectance1
Authors: Heclman J. L. , Heilman W. E. , Moore D. G.
Published: July 2010

A field study was conducted in four differentially irrigated plots of alfalfa (Medicago sativa L.) planted in Shiprock sandy loam (coarseloamy, mixed, mesic Typic Haplargid) to assess spectral reflectance for estimating the crop coefficient (Kc), defined here as the ratio of actual to potential evapotranspiration (ET). A bidirectional reflectance factor was measured using a three‐channel (0.63 to 0.69 µm, 0.76 to 0.90 µm, and 1.55 to 1.75 µm) handheld radiometer, and was used to calculate a perpendicular vegetation index (PVI). Actual ET was determined by the water balance method in non‐weighing lysimeters, and potential ET was calculated using Penman's equation.

Significant linear relationships were found between PVI and percent cover (r2 = 0.911), and between Kc and percent cover (r2 = 0.815). In addition, the position of the PVl intersection on the soil background line changed as a result of soil moisture increases following irrigation, even at high percent cover. Thus, once experimental relationships between Kc and crop growth are established, a mean Kc can be determined from spectral estimates of stage of development and the soil background component of PVI can be used to adjust the mean K, for increased evaporation following irrigation because the ratio of actual to potential evapotranspiration will approach 1 when the soil surface is wet.
Nodulation, N2 Fixation, and Seed Yield of Navy Beans as Influenced by Inoculant Rate and Inoculant Carrier1
Authors: Sparrow S. D. , Ham G. E.
Published: July 2010

Peat is the most commonly used carrier of Rhizobium sp. (rhizobia) in inoculants. The lack of suitable local peat in many areas of the world leads to interest in other materials as carriers of rhizobia. The purposes of these studies were 1) to compare potential carriers of Rhizobium phaseoli for their ability, under field conditions, to supply viable rhizobia to promote nodulation, N2 fixation, and increased seed yield of navy beans (Phaseolus vulgaris L.), and 2) to determine the optimum rate of inoculation with Rhizobium phaseoli to promote nodulation, N2 fixation, and increased seed yield of navy beans in two soils in Minnesota, a loamy sand (sandy, mixed, Udorthentic Haploborall) and a silt loam (fine‐silty over sandy, mixed, mesic Typic Hapludoll).

In 1978, five inoculation rates (ranging from 1 to 108 cells/ cm of row) of liquid suspensions of R. phaseoli inoculants were applied at planting. In 1979, R. phaseoli in six inoculant carriers, peat, charcoal, vermiculite, corn (Zea mays L.) cobs, peanut (Arachis hypogaea L.) hulls, and liquid medium, was used to inoculate navy beans at rates of 2.5 ✕ 104 and 5 ✕ 106 cells/cm of row. Nodule numbers and weight, acetylene reduction rates, seed yield, and seed N percentage were determined.

In 1978, in most parameters measured, inoculation rates of 105—106 cells/ cm were required for a statistically significant increase over the lowest inoculation rate. In 1979 there was no effect of inoculation on a soil with a relatively high population of soil R. phaseoli (104 cells/g soil) and relatively high mineral N content (30 ppm). On a soil with an indigenous population of <10 cells/g soil and mineral N content of 8 ppm, peat and charcoal inoculants resulted in the highest seed yield, nodule numbers and weight, and acetylene reduction rates. Peanut hulls and corn cobs gave the poorest responses. These results indicate that peat, charcoal, and vermiculite can be successfully used as carriers of R. phaseoli but peanut hulls and corn cobs are unsatisfactory.
Fertilizer‐N Effects on N2 Fixation by Cowpea and Soybean1
Authors: Eaglesham A. R. J. , Hassouna S. , Seegers R.
Published: July 2010

While it is established that high levels of combined N inhibit the development and function of legume root nodules, the application of low‐level “starter” doses of fertilizer‐N is sometimes recommended to improve nodulation and N2 fixation in the long term. The amounts of combined N which are required to optimize legume symbiosis are poorly defined. Before screening a number of rhizobial isolates for effectiveness with cowpea [Vigna unguiculata (L.) Walp.] we set out to determine what levels of fertilizer‐N are optimal for symbiosis in pot conditions.

We examined the effects of fertilizer‐N applied at or soon after sowing, on nodulation, N, fixation and growth of two cultivars of cowpea and, for comparison one of soybean [Glycine mar (L.) Merr.] in the greenhouse. Two experiments were done to examine (a) the effects of fertilizer N before flowering and (b) the effects of fertilizer‐N throughout the growth cycle and on final yield. The levels of N found to stimulate symbiosis during the pre‐flowering period were an order of magnitude higher than those previously reported. Applications of 36 and 72 mg N/plant increased nodule weights and acetylene reduction activities up to fourfold and sixfold, respectively, but trends varied with legume host and time of harvest. When 30, 90, 180, or 360 mg N/plant were applied as NH4NO3, KNO3, or urea, symbiotic responses again varied and no single N treatment was optimal for all three legumes. Synergistic effects of applied N on total amounts of N fixed were observed with each host with various N treatments. The strongest synergism occurred in soybean with urea at 30 mg N/plant; for every milligram of urea‐N absorbed, an additional 15 mg of N were fixed symbiotically.
Chloride Toxicity of Soybeans Grown on Atlantic Coast Flatwoods Soils1
Authors: Parker Myron B. , Gascho G. J. , Gaines T. P.
Published: July 2010

Leaf scorch, caused by CI toxicity, affected over 20,000 ha of soybeans (Glycine max (L.) Merr.) in 1980 in the poorly‐drained Flatwoods soils of Georgia. This new disorder, compounded by the extended drought of 1980, resulted in Severe yield reductions of ‘Bragg’ soybeans. Field studies involving fertilizer treatments in two experiments and 15 cultivars in one experiment were conducted in 1981 to determine the cause of the problem. Phosphorus, Mg, and Cl treatments were evaluated on two problem areas—a Leefield sand (arenic Plinthaquic Paleudults) and an Alapaha sand (arenic Plinthic Paleaquults). Cultivars also were evaluated on the Alapaba sand. Leaf scorch developed on plants receiving Cl containing fertilizer and on 5 of 15 cultivars. Symptoms observed were the same as those described for Cl toxicity. Leaf and seed Cl levels averaged 0.12% and 75 µg/g, respectively, for plants receiving no KCl fertilizer compared to 0.94% and 166 µg/g for plants receiving KCl. Leaf and seed Cl levels averaged 1.67% and 682 µg/g, respectively, for five susceptible cultivars compared to 0.09% and 111 µg/g for 10 tolerant cultivars. The parent seed of each cultivar contained relatively low levels of Cl, indicating that susceptible cultivars are not high Cl accumulators when grown under low Cl soil conditions. Leaf scorch ratings were positively correlated with leaf and seed Cl and negatively correlated with seed weight and yield. The leaf scorch problem on susceptible cultivars apparently is caused by a Cl buildup in poorly‐drained Flatwoods soils. The major source of Cl appears to be KCl fertilizer.
Mower Blade Sharpness Effects on Turf1
Authors: Steinegger D. H. , Shearman R. C. , Riordan T. P. , Kinbacher E. J.
Published: July 2010

This study was undertaken to determine effects of repeated mowing with a dull or sharp rotary mower blade on Kentucky bluegrass (Poa pratensis L.) turfs of ‘Park’ and ‘Baron‐Glade‐Adelphi’. Mower blade sharpness effects on turfgrass quality, leaf spot (Bipolaris sorokinianum Shoem.), thatch accumulation, water use rate, and mower fuel consumption were studied. Field experiments were conducted on a Sharpsburg, silty‐clay loam (fine, montmorillonitic, mesic Typic Argiudoll) at the Univ. of Nebraska Field Laboratory located near Mead. Turfgrass quality was reduced by dull mower treatment for both Park and the blend. Leafspot incidence increased on Park turfs mowed with the dull mower, but not on the blended turf which was leaf spot resistant. Thatch accumulation was not significantly influenced by mower blade sharpness. Water use rates under field conditions for Park and Baron‐Glade‐Adelphi turfs were 1.3 and 1.2 times greater, respectively, for turfs mowed with the sharp mower blade than the dull. The reduced water use rate associated with dull mower treatments was positively correlated to reduced shoot density (r = 0.88) and verdure (r = 0.93). Gasoline use was 22% greater with dull mower blade treatments than with sharp. This study substantiates the hypothesis that repeated mowing with a dull mower blade reduced turfgrass quality and increased disease susceptibility. However, these results refute the generally accepted premise that dull mower blade injury of turfgrass leaf tissue increases turfgrass water use.
Absorption and Translocation of Foliarly Applied 15N by Soybeans1
Authors: Morris D. R. , Weaver R. W.
Published: July 2010

Nitrogen nutrition of soybeans (Glycine max) is important in determining their yield potential. Labelling of leaves with 15N by foliar fertilization provides an effective method for determining mobilization and partitioning of N from leaves to other plant parts. The purpose of this field research was to develop a method that would be useful in measuring the efficiency of N absorption and translocation by leaves. Labelled urea was foliarly applied at V5‐V6, V7‐V8, and V10‐V12 growth stages while labelled (NH4)2SO4 was applied only at V5‐V6 growth stage. The N solutions were applied to a single trifoliolate leaf on each plant. A micropipette was used to apply droplets directly to leaves held stationary and horizontal by taping them to a stand. Average N uptake, into the plant, 15 h after application was 71% of that applied. No significant differences in translocation between N sources or growth stages was found.
N2‐Fixation in Field Beans Quantified by 15N Isotope Dilution. II. Effect of Cultivars of Beans1
Authors: Rennie R. J. , Kemp G. A.
Published: July 2010

Field beans (Phaseolus vulgaris L.) have been considered inferior in nis (nitrogen fixation supportive trait), i.e., in their ability to support and benefit from their symbiotic association with N2‐fixing Rhizobium phaseoli. This paper reports the use of N balance in phytotron studies and 15N isotope dilution in the field to determine the effect of R. phaseoli strains and mineral N levels on the expression of nis in 26 cultivars of field beans. Evaluation for nis under N‐free conditions in the phytotron forced total dependence on seed and atmospheric N and provided a useful screening technique before field experimentation. Ranking of cultivars for nis was highly dependent on R. phaseoli strain, mineral N levels, growth habit, growth stage, and temperature regime during evaluation. R. phaseoli strains 3644 and 8215 resulted in higher N2 fixation with temperate beans while strain 3605 was unique in high N2 fixation with two tropical cultivars, Cargamantn and Sangretoro. The addition, in the field, of 40 kg fertilizer N ha−1 on a Typic Haploboroll soil caused a 10% reduction in percent N derived from atmosphere (% Ndfa) in most cultivars but had no effect on ‘Redkloud’. In contrast, ‘Limelight’ suffered a 60 % reduction in % Ndfa. This indicated a host‐specific reaction in nis to mineral N and potential for breeding this resistance into other bean lines. Both in the phytotron and the field, climbing bean cultivars had higher % Ndfa and thus superior nis than bush cultivars. Some cultivars were superior when evaluated at anthesis but not at maturity, indicating a difference in the N2‐fixing span of the cultivar. In the field, % Ndfa of beans was approximately 50 %, the other 50 % being derived from fertilizer and or soil N. The actual amounts of Nz fixed varied between 40 kg ha−1 and 125 kg ha−1 depending on the cultivar. Thus, R. phaseoli may he considered as efficient as R. japonicum is with soybeans in supplying atmospheric N2 to the plant.
Dynamic Nature of the Photoperiod Response in Maize1
Authors: Kiniry J. R. , Ritchie J. T. , Musser R. L.
Published: July 2010

A general quantitative description of maize (Zea mays L.) response to photoperiod for use with widely different genotypes and environments is important in order to accurately evaluate stages in maize ontogeny. This paper describes a method for combining photoperiod and maturity information into a relatively simple model to estimate the interval from seedling emergence to tassel initiation and tassel emergence in maize. Twenty contrasting cultivars of maize were grown to tassel emergence in the Duke Univ. Phytotron at 25°C under photoperiods ranging from 10 to 17.5 h. Dates of tassel initiation were determined destructively and tassel emergence nondesrructively. An apparently general linear relationship was found for estimating the thermal time (degree days) between seedling emergence and tassel initiation from the thermal time between seedling emergence and tassel emergence. This implies that the timing of tassel initiation can be estimated with reasonable accuracy when the temperature and date of tassel emergence are known. The time to tassel initiation was not influenced by photoperiod for all cultivars studied. Those that were photoperiod sensitive experienced a delay in rime to tassel initiation only when the photoperiod was greater than a critical threshold value ranging from 10 to 13.5 h. Below the threshold photoperiod, plants appeared to be insensitive to photoperiod. For photoperiods above the threshold value, the delay in thermal time to tassel initiation was described as a linear function of photoperiod above the threshold value. For the cultivars studied, the photoperiod sensitivity ranged from zero for six insensitive early maturity cultivars to 36 degree days per hour increase in photoperiod for one late maturity cultivar.
Effects of Irrigation on Accumulation of Soil and Symbiotically Fixed N by Soybean Grown on a Norfolk Loamy Sand1
Authors: Matheny T. A. , Hunt P. G.
Published: July 2010

In the southeastern Coastal Plain, soybean [Glycine max (L.) Merr.] is normally grown on soils that are often exposed to drought and leaching rains as well as being low in available N. A field study was conducted to evaluate the impact of water management on accumulation of soil and symbiotically fixed N by soybean grown on these type soils. Nodulating and nonnodulating isolines of ‘Lee’ cultivar soybean were grown under irrigated and nonirrigated conditions in 1979 and 1980 on a Norfolk loamy sand (fine‐loamy, mixed, mesic Typic Paleudults). A period of excessive rainfall occurred in 1979, while a major drought occurred in 1980. Irrigated treatments had lower soil‐NO‐3 concentrations in the Ap horizon than nonirrigated treatments during 1979, but there was no effect of irrigation on soil NO‐3 in 1980. Dinitrogen fixation, as estimated by the difference in N accumulation between nodulating and nonnodulating isolines, accounted for 76 to 91% of total plant N in the irrigated plots and 55 to 60% in the nonirrigated plots. Estimates of total plant N fixed exceeded 1100 mg/plant for the irrigated plots in 1979 and 1980. Maximum N accumulation for the nodulating isoline occurred in the nonirrigated plots in 1979 and in the irrigated plots in 1980. However, the nonnodulating isoline had maximum accumulations of both N and dry matter in the nonirrigated treatments in both 1979 and 1980. The number of nodules/plant and the C2H2‐reducing activity were significantly higher in the irrigated plots during the pod growth stages in 1980. Irrigation did not significantly affect seed yield of nodulating Lee soybean in 1979, but did result in a twofold increase in 1980. The effects of irrigation on the Lee nonnodulating isoline resulted in a positive yield response in 1980, but a negative response in 1979. These findings show that a major portion of the N‐requirement for soybean in the southeastern Coastal Plain is met by fixation and that the relative importance of fixed N may vary substantially with rainfall patterns and irrigation.
Sensitivity Analysis of Parameters Used in Simulating K Uptake with a Mechanistic Mathematical Model1
Authors: Silberbush M. , Barber S. A.
Published: July 2010

In recent years, mechanistic mathematical models for predicting nutrient uptake by plants growing in soil have been developed and verified for P and K uptake. However, detailed sensitivity analyses from an agronomic viewpoint have not been published. The objective of this paper is to determine the relative significance of each of the 11 parameters in the Cushman (1979) model for predicting K uptake by ‘Williams 79’ soybeans (Glycine mar L.) from Raub (fine‐silty, mixed, mesic Aquic Argiudoli) silt loam using a sensitivity analysis. Each variable was used at 0.5 to 2.0 times the initial level obtained experimentally while the remaining parameters were held constant. Analyses were also made where interdependent parameters were varied simultaneously by using assumed interdependance between specified variables. Predicted K uptake was influenced more by changes in root length and root radius than by similar changes in any other parameter. Changes in the soil supply parameters; initial concentration in soil solution, soil buffer power, and effective diffusion coefficient influenced K uptake more than changes in the plant kinetic parameters for the soil‐plant system used.
Root and Shoot Development in Winter Wheat1
Authors: Klepper Betty , Belford R. K. , Rickman R. W.
Published: July 2010

abstract

Better characterizations of cereal root systems are needed for water extraction models, for relating root and shoot development, and for describing the root systems of individual tillers. This paper presents a naming system for root axes of wheat (Triticum aestivum L. em. Thell). Each axis is described by the number of the node with which it is associated and by the direction of its growth with respect to the leaf borne at the node. Plants were grown in the field on a Walla Walla silt loam (coarse‐silty, mixed, mesic family of Typic Haploxerolls). Examination of the upper 10 cm of roots indicated that root axes were produced at predictable times with respect to shoot development. The number of roots on any culm (Y) could be calculated from the number of leaves on the culm (X) (Y = 1.95 X –3.06, r2= 0.9). The presence of lateral roots could be predicted if data were plotted to relate root axis development to a phyllochron or degreeday scale.
Yield, Water‐Use Efficiency, and Oil Concentration and Quality of Dryland Sunflower Grown in the Southern High Plains1
Authors: Jones Ordie R.
Published: July 2010

For oilseed sunflower (Helianthus annuusL.) to develop as a competitive crop on the drylands of the Southern High Plains, information is needed concerning the effects of various agronomic practices on sunflower production in this area. The objectives of the research were to determine the effects of seeding date, plant population, and soil water content at time of seeding on dryland sunflower seed yield, water‐use efficiency (WUE), and oil concentration and quality. The study was conducted from 1975 through 1979 on Pullman clay loam (fine, mixed, thermic Torrertic Paleustoll). Seeding date had the greatest effect on seed yield and WUE and reflected the effects of seasonal precipitation patterns. Yield response to increased soil water content at seeding was 0.70 kg seed/m3water. Plant populations in the range of 2.5 to 4.5 plants/m2resulted in similar seed yields and WUE , but high populations (>3.5 plants/m2) tended to increase oil concentration. Seeding date significantly influenced oil concentration and quality with April seedings having a 50 to 80 g/kg greater oil concentration than July seedings. Oleic acid concentration in sunflower oil decreased, and conversely, linoleic acid concentration increased as seeding dates became later. Thus, by manipulating seeding dates, oil of a quality suited to a particular need (margarine, cooking or salad oil) may be produced. Yield potential was enhanced when soil water content at seeding was increased, indicating that sunflower is adapted for use on water conservation systems or after fallow where additional soil water may be available.
Competition and Allelopathy Between Soybeans and Weeds1
Authors: Rose Steven J. , Burnside Orvin C. , Specht James E. , Swisher Beth A.
Published: July 2010

This research was initiated to determine how soybean [Glycine max (L.) Merr.] cultivars differ in competitive ability and also whether allelopathy functions to inhibit surrounding weed growth. Initially 280 soybean cultivars were screened in the field for competitive ability based on emergence, seedling vigor, quickness of canopy closure, and ability to inhibit growth of velvetleaf (Abutilon theophrasti Medic.) and foxtail millet [Setaria italica (L.) Beauv.]. Experiments were conducted at Lincoln, Nebr. on a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudolls) during 1981 and 1982. Soybean cultivars of later maturity tended to compete more effectively with weeds. Competitive cultivars emerged quickly, rapidly formed a canopy, and were able to slow the growth of competing weed species. Twenty soybean cultivars of varying competitive ability were selected and grown in the greenhouse during 1981 and 1982 to determine the importance of allelopathy in competing with weeds. Exudates from roots of soybean cultivars grown in sand reduced the dry weight of 4‐week‐old velvetleaf plants an average of 15%, but foxtail millet was not inhibited. Incorporation of 1% ground soybean dry matter into Sharpsburg silty clay loam inhibited germination and dry weight of greenhouse grown velvetleaf an average of 46% each. Foxtail millet germination and dry weights were reduced an average of 82 and 65%, respectively. Undiluted soybean plant extracts of all cultivars tested slowed the germination and dry weight accumulation of 6‐day‐old velvetleaf and foxtail millet, but dilution of the extracts caused quite variable responses. Osmotic potential of the extract solution appeared to be the main cause of inhibition, however, extracts of some cultivars, diluted to decrease the osmotic potential, still inhibited growth. Allelopathy appears to be one mechanism for competition among soybeans and weeds. Soybean cultivars possessing the ability to chemically inhibit competing weed growth would be a great benefit to the soybean producer.
Drought Response of Grain Legumes Under Irrigation Gradient: I. Yield and Yield Components1
Authors: Pandey R. K. , Herrera W. A. T. , Pendleton J. W.
Published: July 2010

Food legumes are widely grown as a source of protein in semiarid and tropical regions, but production is often limited by the large variation in the amount and distribution of rainfall. Mungbean (Vigna radiata L.), cowpea (Vigna unguiculata L.), soybean (Glycine max L.), and peanut (Arachis hypogeae L.), often planted after rice (Oryza sativa L.), were compared for response to a season‐long moisture stress on medium‐deep Tropudalf soil, using a line‐source sprinkler irrigation system during the January to April 1982 dry season. Drought stress reduced seed yield of all four food legumes, but the reduction due to water stress was greater in mungbean followed by soybean, cowpea, and peanut. Mungbean produced significantly lower yields at all moisture levels than the other legumes. Total water use by peanut was highest, followed by cowpea, soybean, and mungbean. Among yield components, the numbr of pods per square meter was most affected by water stress in all four species, followed by number of seeds per pod, while seed weight was least affected. Harvest index decreased Linearly with increasing levels of drought for all four species.
Drought Response of Grain Legumes Under Irrigation Gradient: III. Plant Growth1
Authors: Pandey R. K. , Herrera W. A. T. , Villegas A. N. , Pendleton J. W.
Published: July 2010

Plant growth in semiarid and tropical regions is often limited by variations in the amount and duration of rainfall. Four food legumes, mungbean (Vigna radiata L.), cowpea (Vigna unguiculata L.), soybean (Glycine max L.), and peanut (Arachis hypogeae L.) were subjected to different moisture gradients in the field on a medium‐deep Tropudalf soil. Water stress effects on the shoot and root growth were analyzed to determine relationships with seed yield and plant growth and to evaluate possible drought avoidance mechanisms. Water stress was created with a line‐source sprinkler irrigation system. Plant growth analyses were computed from samples taken at frequent intervals during the vegetative and reproductive phases. Increasing moisture stress resulted in progressively less leaf area, leaf area duration (LAD), crop growth rate (CGR), and shoot dry matter. Conversely, specific leaf weight increased with increasing levels of water stress. The four seed legumes differed in their ability to maintain leaf area expansion rate, leaf area index, LAD, CGR, and shoot dry matter at high levels of water stress. Cowpea and peanut had higher root densities at 0.4 to 0.8 m soil depths than soybean or mungbean and this appeared to be a major adaptive mechanism for their drought tolerance.
Leaf Water and Turgor Potential Threshold Values for Leaf Growth of Wheat1
Authors: Eastham Judy , Oosterhuis Derrick M. , Walker Sue
Published: July 2010

Environmental factors affecting leaf growth must be understood for accurate predictions of yield by crop modeling. Water is one of the most important of these factors. The effect of water deficits on the relationships between leaf elongation and leaf water and turgor potentials was investigated on wheat (Triticum aestivumL.) grown under field conditions on a Rhodic Paleustalf on the Highfeld Plateau of the Republic of South Africa. Leaf growth rates of water stressed and nonstressed wheat were measured, and corresponding values of leaf water, osmotic and turgor potentials obtained using thermocouple psychrometers. Water stress resulted in a reduced growth rate and a lower total cumulative growth. The growth curve was made up of two phases, an initial phase of both lamina and leaf sheath elongation, and a second phase of leaf sheath elongation alone. The different relationships between growth rate and midday leaf turgor potential in the two phases indicated leaf sheath elongation to be more sensitive to stress than lamina elongation. The water‐stressed treatment had a lower water potential threshold value for elongation of ‒2571 kPa compared with ‒1671 kPa for well‐watered plants. Turgor potential threshold values for elongation in the stressed plants were also lower by 197 kPa for the phase of leaf lamina and sheath elongation, and by 488 kPa for the phase of sheath elongation alone. Stress acclimation apparently occurred by osmotic adjustment to maintain turgor potentials necessary for elongation.
Yield and Composition of Tall Fescue Stockpiled for Different Periods1
Authors: Fribourg Henry A. , Bell Kenneth W.
Published: July 2010

Stockpiling of late summer and early autumn growth can provide forage for grazing during late autumn and early winter when small amounts of forage are produced in the U.S. humid mesothermal regions. Three experiments were conducted on Typic Paleudult, Typic Paleudalf, and Typic Hapludult soils to quantify the amount and composition of tall fescue [Festuca arundinacea (L.) Schreb.] forage stockpiled in summer and/or autumn following frequent clipping prior to stockpiling. These forage yields were compared to the regrowth after stockpiled forage removal and to continuously clipped fescue. Treatments consisted of combinations of date of stockpiling initiation and duration of stockpiling. Stockpiling started in July or August resulted in accumulations of 1.0 to 1.4 Mg ha−1 dry matter (DM) the 1st month, and an additional 1.1 to 1.5 Mg ha−1 the 2nd month. When July stockpiling was extended into September, a further 1.4 Mg ha−1 DM was accumulated. Stockpiling summer growth for grazing in October, November, and December resulted in a small loss of accumulated DM, and large losses occurred when harvest was delayed until January. Crude protein (CP) concentrations for stockpiled forage generally decreased from 80 to 150 g kg−1 of DM at the start of stockpiling to 20 to 90 in winter. Concentrations of aciddetergent fiber (300 to 340 g kg−1 of DM) and neutral‐detergent fiber (620 to 710 g kg−1) did not vary with duration of stockpiling. Concentrations of K were 0.6 to 0.9 mol kg−1 at the start of stockpiling and decreased linearly to 0.15 to 0.30 in winter; P decreased from 0.09 to 0.12 mol kg−1 in summer and early fall to 0.035 to 0.06 in October and later. Stockpiling autumn growth resulted in accumulation of only 1.3 Mg ha−1 DM of relatively high quality forage through December. These data indicate that stockpiling fescue is a viable option in areas receiving 1000 to 1200 mm annual precipitation. Start of forage accumulation may begin as early as the beginning of summer, or may be delayed to late summer or early autumn. Losses of DM and nutrients may be substantial in January or later.
A Generalized Relationship between Photosynthetically Active Radiation and Solar Radiation1
Authors: Meek D. W. , Hatfield J. L. , Howell T. A. , Idso S. B. , Reginato R. J.
Published: July 2010

Photosynthetically active radiation (PAR) is a necessary input in several crop growth models. Previous research from several locations with different instruments has suggested that PAR could be estimated as a constant fraction of shortwave radiation. This study was conducted to determine if a simple relationship was valid for a large geographic area in the western half of the USA. In the semiarid climate near Fresno, CA, the daily photosynthetic photon flux density (PPFD) in units of μmol m−2 was 2.04 ± 0.06 times the solar irradiance (SI). The daily irradiance within the PAR waveband (photosynthetic irradiance (PI), 0.4 to 0.7 μm) was estimated to be 45% of the daily solar irradiance. The diurnal pattern of these relationships was consistent with measurements at Phoenix, AZ and exhibited only a slight diurnal variation. Independent measurements of the solar irradiance between 0.285 and 0.63 μm with “filtered” pyranometers at the Fresno site indicated that irradiance between 0.285 and 0.63 μm was 41% of solar irradiance, a result which was about 7% lower than the estimate from the PAR/SI value converted with a published sun and sky PAR/PI factor. This difference was largely attributed to the differences in measured wavebands. Measurements of solar irradiance less than the waveband of 0.63 μm and total solar irradiance obtained with the same equipment at Brawley, CA; Weslaco, TX; Temple, TX; Manhattan, KS; Lincoln, NE; St. Paul, MN; Fargo, ND; Sidney, MT; Beartooth Pass, WY; Kimberly, ID; Davis, CA were similar to those measured at Fresno, CA. The results indicate that PAR can be estimated from solar irradiance measurements to within 10% (which is probably acceptable for most plant growth models) throughout most of the Western USA.