bluuebunny/crossref_metadata_2025 huggingface dataset:
Persistence of Selected Tropical Pasture Legumes in Peninsular Florida1
Authors: Pitman W. D. , Kretschmer A. E.
Published: July 2010

The potential N contribution of tropical legumes to grass pastures on the infertile soils of Peninsular Florida necessitates increased efforts to develop suitable pasture legumes. Nineteen accessions representing 17 tropical legume species were evaluated for persistence under grazing in bahiagrass swards on a Peninsular Florida Arenic Haplaquod (Spodosol) soil. After three growing seasons in the mixed grass‐legume swards, only Vigna parkeri Bak. and aeschynomene (Aeschynomene americana L.) covered larger areas than were originally planted. Indications of potential adaptation to flatwoods pastures were also obtained with ‘Florida’ carpon desmodium [Desmodium heterocarpon (L.) DC], phasey bean [Macroptilium lathyroides (L.) Urb.], Vigna adenantha (G.F. Meyer) Marechal, Mascherpa, and Stainier and Vigna luteola (Jacq.) Benth. However, the variation in response of these four accessions among field replications indicates that site and management requirements of these legumes need further investigation.
Effect of N Fertilizer on Protein Content of Grain, Straw, and Chaff Tissues in Soft White Winter Wheat1
Authors: Glenn D. M. , Carey A. , Bolton F. E. , Vavra M.
Published: July 2010

Nitrogen management programs of soft white winter wheat (Triticum aestivum L.) in semiarid regions are generally based upon soil tests of available water and residual N levels. The purpose of this work was to develop postharvest criteria for N‐sufficiency and N‐insufficiency based on tissue protein levels as it relates to maximum grain yield in a fallow‐wheat rotation. Yield‐protein relationships in grain, straw, and chaff tissues were examined in field trials from 4 harvest years on a Walla Walla silt loam (coarse‐silty, mixed, mesic, Typic Haploxeroll). Grain protein content was a better postharvest indicator of N sufficiency for maximum grain yield than straw or chaff protein levels. Excessive weed growth confounded this relationship in 1 year. Using a chi‐square interaction procedure, a critical level of 8.8% grain protein was determined necessary for N sufficiency in ‘Stephens’ soft white winter wheat when weed growth was not a management problem. The transition zone between N sufficient and N insufficient responses was between 8.3 and 9.1% grain protein. The amount of relative yield lost to N insufficiency was related to grain protein content. There was a 9.8% yield reduction for each grain protein percentage below 9.1. Critical protein values indicative of N insufficiency could not be determined for straw and chaff tissues. Straw and chaff protein levels greater than 2.6 and 3.5%, respectively, were exclusively associated with N sufficiency.
Seed Density and Seed Size of Pearl Millet as Related to Field Emergence and Several Seed and Seedling Traits1
Authors: Lawan M. , Barnett F. L. , Khaleeq B. , Vanderlip R. L.
Published: July 2010

Pearl millet, Pennisetum americanum(L.) Leeke, is often established under stressful environmental conditions. Thus, establishment capability is crucial to success of the crop. Objectives of this study were (i) to verify previous results associating establishment of the crop with density and size of seed, and (ii) to identify other seed and seedling traits of pearl millet that are related to seed density and size. Seed of four populations was divided by gravity table into three density fractions, each of which was then separated, by dockage sieves, into three size fractions. Seed representing each population‐density size fraction was evaluated in a field study at Manhattan, KS in 1981 and in the laboratory. Seedling emergence increased from 40% with small, low‐density seed, to 62% with large, high‐density seed. Days from seeding to anthesis decreased from 70 with small, low‐density seed, to 62 with large, high‐density seed. In both cases, density and size interacted in such a manner that each factor had most effect at low levels of the other. Seed weight, a germination index that emphasized speed of germination, and seed diameter were positively affected by both seed density and size. In addition, germination, seedling height 24 days after seeding, and proportion of vitreous starch in seed endosperm were positively related to seed density. Seedling respiration rate, on a per‐seed basis, was associated positively with seed density and size. With a fixed weight of seed, however, there was little effect. Results indicated that seed density and seed size were effective criteria of field establishment and of seed quality as determined by a number of laboratory tests. In some cases, however, the nature of the density × size interaction implied that the major effects of both factors were effectively integrated in seed weight.
Suppression of Anthracnose and Phomopsis Seed Rot on Soybean with Potassium Fertilizer and Benomyl1
Authors: Sij J. W. , Turner F. T. , Whitney N. G.
Published: July 2010

Recent studies linking K with less disease in certain crops have stimulated interest in the beneficial aspects K may play in plant disease protection. The objectives of this 3‐yr study were to evaluate the role of K fertilizer on anthracnose [Colletotrichum dematium(Pers. ex Fr.) Grove var. truncatum(Schw.) Arx.] and phomopsis seed rot (Phomopsissp.) development in field‐grown soybean plants [Glycine max(L.) Merr.] and to measure the interaction of foliar‐applied benomyl fungicide with soil‐applied K fertilizer. The soil, a Typic Agriaquoll, contained low (215 to 278 kg/ha) and high (11 to 96 kg/ha) levels of available K and P, respectively. The experiments included six levels of K, three levels of P fertilizer, and two levels of benomyl fungicide on ‘Davis’ soybean harvested at maturity and 4 weeks later. Anthracnose disease ratings decreased significantly as K rates increased to the maximum of 450 kg/ha. Benomyl and K + benomyl reduced anthracnose substantially more (about 60%) than did K alone. The action of K fertilizer on anthracnose control appeared to be additive to that afforded by benomyl when the soil contained low to medium K. Increasing K fertilizer significantly increased soybean yield by about 700 kg/ha when 220 kg/ha of K fertilizer was applied. Application of benomyl provided an additional yield increase of about 300 kg/ha except at the highest K level. Increasing K up to 330 kg/ha reduced delayed harvest yield losses caused by shattering and weathering. Benomyl and K + benomyl treatments minimized delayed harvest losses, which peaked at a K level of about 220 kg/ha. Phosphorus fertilizer failed to increase yield or prevent shattering. Increasing K reduced Phomopsissp. in first‐harvest seed from 35% to about 1% and in second‐harvest seed from about 52 to 28% in plots receiving no K fertilizer and 450 kg/ ha of K, respectively. The addition of benomyl suppressed this pathogen further in first‐harvest seed from 12% infected seed to 1% and in second‐harvest seed from 40 to 18% in plots receiving no K fertilizer and 450 kg/ha of K, respectively. Phosphorus, however, appeared to slightly enhance Phomopsissp. development. The effects of residual fertilizer on anthracnose development and yield were evident the following soybean growing season. Although pathogen pressure and environmental conditions play a major role in disease development in soybean, it should be recognized that soil K level can also be an influencing factor.
Comparison of Methods of Enriching a Soil with Nitrogen‐15 to Estimate Dinitrogen Fixation by Isotope Dilution1
Authors: Rennie R. J.
Published: July 2010

A 2‐yr field comparison of methods of labeling the soil with 15N was undertaken to increase the precision of estimating N2fixation by the 15N isotope dilution procedure. Dinitrogen fixation was estimated using ‘Aurora’ field bean (Phaseolus vulgarisL.) grown on a Chin loam (Typic Haploboroll) soil under irrigation in southern Alberta. Postemergence fluid injection of (15NH4)2SO4into the rooting zone of 1‐week‐old plants (with or without the nitrification inhibitor N‐Serve) resulted in excellent experimental precision and greater planning flexibility. It was superior to preemergence addition of liquid 15N in broadcast or banded form because of the high winds often encountered in the spring. The preemergence addition of low‐level 15N‐labeled legume or cereal organic residues compared favorably with mineral N addition and had the advantage that residues from previous 15N experiments could be utilized cost‐free. Isotope dilution of 15N at levels of natural isotopic abundance resulted in similar estimates of N2fixation with no consistent evidence of isotopic discrimination and appears promising as an inexpensive but qualitative screening procedure for field selection of N2fixation by legume breeders.
Composition of Leaf Protein Concentrate and Deproteinized Juice from Alfalfa, Red Clover, and Birdsfoot Trefoil1
Authors: Collins Michael
Published: July 2010

Losses during field wilting of silage and curing of hay reduce both yield and quality. Direct harvest and mechanical dewatering avoid these losses and produce a protein concentrate. A 2‐year field experiment was conducted to evaluate legume species and harvest date effects on the yield and composition of the protein concentrate and deproteinized juice fractions from spring growth legume herbage. The soil was a Plano silt loam (fine‐silty, mixed, mesic Typic Argiudoll). Alfalfa (Medicago sativa L.) protein concentrate averaged 201 g dry matter (DM) kg−1 total mass, slightly higher than red clover (Trifolium pratense L.) and birdsfoot trefoil (Lotus corniculatus L.). Harvest date effects on DM concentration in both the protein concentrate and the deproteinized juice were significant but showed little relationship to shoot maturation stage. Alfalfa protein concentrate averaged 102 g N kg−1 DM, which was more N than the protein concentrate from red clover and birdsfoot trefoil in 1981 but not in 1980. Harvest date effects were small for alfalfa protein concentrate N concentration but red clover and birdsfoot trefoil had less of that constituent on the last harvest date. Total nonstructural carbohydrate (TNC) was highest in the deproteinized juice from red clover, which had 327 g TNC kg−1 DM, followed by birdsfoot trefoil and alfalfa with the lowest concentrations. Harvest date effects on TNC differed among species, but these differences were not large enough to be of practical importance. Alfalfa and red clover whole crops differed in the concentrations of several amino acids, but they differed less than the whole crop differed from the pressed forage and protein concentrate fractions within each species. Red clover protein concentrate had more threonine and valine than alfalfa protein concentrate but only 85% as much methionine, 52% as much cystine and less isoleucine. Results of this 2‐yr experiment indicate that N and DM concentrations differ in protein concentrates from different perennial legumes. Amino acid concentrations in protein concentrate were generally less affected by species and maturation than the same constituents in the whole crops. Species differences in deproteinized juice TNC concentrations were substantial and should be considered in the development of mechanical dewatering systems.
Effects of Timing of Nitrogen Fertilization and a Fungicide on Soft Red Winter Wheat1
Authors: Roth G. W. , Marshall H. G.
Published: July 2010

Split spring N applications and fungicides are important components of proposed intensive management systems for soft red winter wheat (Triticum aestivum L.). Six experiments at two locations were conducted on Hagerstown silt loam (fine, mixed, mesic Typic Hapludalf) soils to evaluate the responses of wheat to a fungicide and delayed or split N applications. Delayed N treatments consisted of a single application of 100 kg ha−1 at either growth stage (GS) 5 or 8. Seven split N treatments consisted of two or three applications made at GS 3, 5, or 8, totaling 100 kg N ha−1. Split and delayed N responses were compared to those resulting from four rates of N applied at GS 3. Average grain yields for the experiments ranged from 3.2 to 5.9 Mg ha−1. Yields from split and delayed N were greater than the maximum achieved with GS 3 N applications in only one of the six experiments. In this experiment, the greatest yield increase due to split N, 0.7 Mg ha−1, occurred when a fungicide was used. A large amount of precipitation (219 mm) at that location between GS 3 and GS 5, and a high fertilizer N requirement apparently contributed to the response to split N. Yield responses to fungicides (triadimefon [l‐(4‐chlorophenoxy)‐3,3‐dimethyl‐l‐(lH‐l,2,4‐trizol‐1‐yl)‐2‐butanone] or triadimefon + mancozeb [zinc ion and manganese ethylene bisdithiocarbamate)) varied between years and ranged from 0 to 0.9 Mg ha−1. Decisions to use split N and fungicides should be based on factors such as disease severity, rainfall, and anticipated soil N supplying capability.
Effects of Acid Soil Infertility Factors on Growth and Nodulation of Soybean1
Authors: Alva A. K. , Edwards D. G. , Asher C. J. , Suthipradit S.
Published: July 2010

Growth of a legume in acid soils can be limited by the effects of infertility factors on the growth of the host plant per se or on nodulation and nodule function. Effects of varying solution pH (4.5, 5.0, 5.5) and external calcium (Ca) concentration (0.05, 0.5, 2.5 mM) on growth and nodulation of soybean [Glycine max (L.) Merr. cv. Fitzroy] were investigated in a solution culture experiment. Total dry matter production was not influenced by pH; however, shoot growth increased while root growth decreased with increasing solution pH. Increase in Ca concentration significantly increased shoot dry weight at pH 5.0 and 5.5. At pH 4.5, appearance of the first nodule was delayed, and nodule number and nodule dry weight per plant were lower than at higher pH. Nodule number and dry weight per plant were not affected by Ca concentration at pH 4.5 but increased significantly with increasing Ca concentration at pH 5.0. At pH 5.5, nodule number per plant decreased, but nodule dry weight increased as Ca concentration increased from 0.5 to 2.5 mM. Further experiments were conducted at pH 4.5 with 0.5 mM Ca concentration to investigate the effects of monomeric aluminum (Al) activity (∑ aA1 mono) on the growth of soybean supplied with adequate inorganic N and on growth and nodulation of plants inoculated with Bradyrhizobium japonicum. Shoot and root weights declined linearly with increase in ∑ aAl mono, with the critical ∑ aAl mono (90% of yield in Alfree treatment) ranging from 5 to 9 µM. Nodulation was totally inhibited in solutions with ∑ aAl mono ≥ 27.8 µM. The critical ∑ aA1 mono for nodule number and for nodule dry weight per plant were approximately 0.4 µM.
Utilization of DRIS for Diagnosis of Nutrient Deficiencies in Winter Wheat1
Authors: Amundson R. L. , Koehler F. E.
Published: July 2010

The diagnostic recommendation integrated system (DRIS) has been regarded by some to be capable of providing nutrient diagnoses via foliar analyses regardless of the origin or age of the plant. This study had two objectives designed to address this claim. First, to determine if nutrient ratio norms currently available for wheat (Triticum aestivum L.), based on hard red winter wheat from Kansas, South Dakota, and Canada, could be used by the DRIS procedure to accurately diagnose deficiencies for N, P, K, and S in soft white irrigated winter wheat (cv. Daws) grown in central Washington state. Second, since DRIS diagnoses are based on a set of nutrient ratios assumed to be relatively invariate with age, to determine if a sampling date/time dependency existed for six specified nutrient ratios. Using the set of published DRIS norms developed from wheat grown in the Midwest, nutrient diagnoses calculated on irrigated winter wheat grown in central Washington tended to overestimate N deficiencies and underestimate P deficiencies at early heading and tillering, respectively, relative to parallel diagnoses by DRIS based on a corresponding set of norms. This second set of norms was derived from tissue analyses of winter and spring wheat grown on a Haploxeroll, an Argixeroll, two Argialbolls, and a Camborthid in Washington state. A statistical analysis of nutrient ratios from winter wheat grown in eastern Washington indicated that six ratios (N/P, K/N, K/P, N/S, P/S, and K/S) each exhibited significant sampling date/time dependence. Consequently, nutrient diagnoses provided by the DRIS procedure may not yet be independent of the origin and age of plant.
Grain and Forage Sorghum Production with No‐Tillage on Dryland
Authors: Unger Paul W.
Published: July 2010

Grain sorghum [Sorghum bicolor (L.) Moench] is adapted to the Southern and Central Great Plains, but water stress at critical reproductive stages can sharply reduce grain yields of the crop on dryland. In contrast, forage sorghums (S. bicolor sudanense or saccharatum) have no such critical stages and, hence, do not require such timely rainfall to attain good yields. This study compared growth, production, water use, and water‐use efficiency of grain and forage sorghums under no‐tillage conditions on dryland from 1984 to 1986. All cultivars attained similar heights at 30 d after planting, but forage sorghums were taller at later times. Average total dry matter (TDM) production by grain and forage sorghums (8.14 vs. 8.61 Mg ha−1) was not significantly different. Total (grain plus stover) crude protein production was higher for grain than for all forage sorghums except ‘Sugar Dan’. Total digestible energy (DE) and metabolizable energy (ME) production also were higher for grain sorghum. Grain sorghum stover, however, has low nutrient value and usually is not harvested. When only grain of grain sorghum is considered, nutrient production (crude protein, DE, and ME) was lower than that for forage sorghums. Water‐use efficiency for TDM and nutrient production was lower for grain than for forage sorghums because grain sorghum had a longer growing season, which resulted in higher growing season precipitation and total water use than that for forage sorghums. In conclusion, forage sorghums are viable alternative crops to grain sorghum on dryland in the Southern Great Plains where forages can be used by the cattle (BOS spp.) industry.
Evaluation of the Salinity Tolerance of Russian‐Thistle, a Potential Forage Crop
Authors: Fowler J. L. , Hageman J. H. , Suzukida M. , Assadian H.
Published: July 2010

Russian‐thistle (Salsola spp.) has economic potential as a forage for arid‐lands agriculture. It is drought and heat tolerant, uses water efficiently, and may be salt tolerant. Laboratory and greenhouse studies were conducted to determine the salinity tolerance of Russian‐thistle in three developmental stages: (i) germination, (ii) juvenility, and (iii) reproductivity. Treatment solutions were prepared using NaCl and CaCI2 in a 2:1 molar ratio. The effect of salinity (electrical conductivities of 0.1, 10.1, 18.8, 26.7, and 33.8 dS m−1) and temperature (5, 10, 15, 20, 25, and 30°C) on germination was determined under laboratory conditions. Salinity response during juvenility and reproductivity was studied under greenhouse conditions using sand culture irrigated with salinized nutrient solutions with electrical conductivities of approximately 1.3, 10.5, 18.2, 26.7, and 33.2 dS m−1. Germination percentages, fresh and dry biomass yield (total aboveground production), water content, ash content, and mineral composition of the ash were measured. A variable response to salinity was observed among the stages of plant development. Russian‐thistle was less salt tolerant during germination than at later growth stages. Germination generally declined linearly with increasing salinity at all temperatures. However, final germination was significantly reduced only at 30°C. Continuous exposure to salinity from the seedling stage through early flowering increased dry biomass yield by 56 and 24% over the control at treatment solution salinities of 10.5 and 18.2 dS m−1, respectively, 64 d after planting. In contrast, when the initial exposure to salinity occurred during the transition from the vegetative to the flowering stage, yield decreased linearly as salinity increased, with no yield enhancement at any salinity level. The reason for this differential response to salinity in the two growth stages was not determined.
Centipedegrass Decline and Recovery as Affected by Fertilizer and Cultural Treatments
Authors: Johnson B. J. , Carrow R. N. , Burns R. E.
Published: July 2010

Centipedegrass [Eremochloa ophiuroides (Munro) Hack.] turf is often over‐fertilized, resulting in “centipede decline.” The purpose of this research was to determine the influence of fertilizer programs and cultural treatments on centipedegrass recovering from decline and for several years after recovery. Treatments were arranged in a split‐block statistical design with subunits in strips. Primary strips were seven cultural treatments and subunit strips were five fertilizer programs. The soil type was a Cecil sandy loam (clayey, kaolinitic, thermic Typic Hapludult). Centipedegrass with decline (50%) recovered to an acceptable turfgrass quality and density after 2 yr of annual treatments with 100–44–83 N‐P‐K rates (kg ha−1) applied in April. Scalping, topdressing, and vertical mowing did not improve turfgrass recovery during the first 2 yr of the study. Quality was improved by a 200–88–166 N‐P‐K rate (kg ha−1) for the first 3 yr, but thereafter, the grass lost density and was chlorotic. There was no benefit from additional K applied in late August to plots previously treated with a 100–44–83 N‐P‐K rate in April. Topdressing with soil improved spring growth, qualtiy, and shoot density more than did vertical mowing or scalping. Thatch increased by 18% with annual 100–44–83 N‐P‐K treatments, and similar thatch levels occurred with the 200–88–166 N‐P‐K treatment. Topdressing with soil decreased thatch accumulation 48% compared to untreated turf. Vertical mowing twice per year provided 15 to 17% thatch control, and scalping none. Fertilization at the 100–44–88 N‐P‐K rate plus annual topdressing provided the best turfgrass quality, shoot density, and lowest thatch accumulation.
Effect of Zinc Deficiency on Alcohol Dehydrogenase Activity and Nutrient Uptake in Rice
Authors: Moore P. A. , Patrick W. H.
Published: July 2010

Zinc deficiency in rice (Oryza sativa) usually occurs after flooding. A greenhouse experiment was conducted to determine if the metabolic disorders associated with Zn deficiency in flooded rice are due to decreases in alcohol dehydrogenase (ADH) or glutamate dehydrogenase (GDH) activities, or both, in the roots, since Zn is a cofactor in these enzymes. ‘Saturn’ rice, a variety characterized as being susceptible to Zn deficiency, was grown in 20 pots containing 3 kg of Crowley silt loam soil (fine, montmorillonitic, thermic Typic Albaqualf). Half of the pots received 1 mg Zn/kg as ZnEDTA; the other half served as controls. Five days after flooding the control plants showed signs of Zn deficiency. The plants were harvested 17 d after flooding. Aboveground dry matter production by the fertilized plants (x̄=0.91 g) was significantly greater than that of the Zn‐deficient control plants (x̄=0.24 g). Plant tissue analysis revealed that Zn‐deficient plants accumulated divalent cations at the expense of monovalent cations, possibly indicating the increased production of a divalent charge‐specific carrier. Root GDH activities of the control and fertilized plants were not significantly different. However, ADH activities in the roots of plants that had received Zn were more than twice as high as those in control plants. Root ADH activity was also correlated with Zn concentration in the leaves (r=0.78**). It is hypothesized that decreases in the ADH activity of Zn‐deficient flooded rice result in less ATP production, thereby reducing vital metabolic activities of the roots.
Animal Performance on Limpograss‐Aeschynomene and Nitrogen‐Fertilized Limpograss Pastures
Authors: Rusland G. A. , Sollenberger L. E. , Albrecht K. A. , Jones C. S. , Crowder L. V.
Published: July 2010

In vitro digestible organic matter (IVDOM) concentration of ‘Floralta’ limpograss [Hemarthria altissima (Poir.) Stapf et C. E. Hubb.] is high compared to many tropical grasses, but low crude protein (CP) concentration in Floralta may limit animal performance. Aeschynomene (Aeschynomene americana L.) grows well in association with limpograss and may improve animal performance on limpograss‐based pastures. This study compared steer (Bos spp.) average daily gain (ADG), carrying capacity (CC), and gain per hectare from midsummer to early fall on limpograss pastures that were overseeded with aeschynomene (LA) or fertilized with N (LN). Soils were primarily Pomona sands (sandy, siliceous, hyperthermic Ultic Haplaquods). Seasonal ADG (84 d in 1984, and 126 d in 1985 and 1986) was higher for LA than for LN pastures in 1984 (0.69 vs. 0.36 kg), 1985 (0.55 vs. 0.27 kg), and 1986 (0.85 vs. 0.54 kg). Handplucked herbage of aeschynomene had mean CP and IVDOM concentrations of approximately 250 g kg−1 dry matter (DM) and 720 g kg−1 organic matter (OM). Handplucked limpograss CP was marginal for growing steers, averaging 92 and 88 g kg−1 DM in 1985 and 1986, respectively. Mean seasonal CC over the 3 yr of grazing was higher for LN than for LA pastures (2210 vs. 1700 kg liveweight ha−1 d−1). In 1985 and 1986, however, mean seasonal CC did not differ between systems, but from early July to mid‐September LN pastures had higher CC (2240 vs 1540 (1985) and 2450 vs 1930 (1986) kg liveweight ha−1 d−1]. Mean gain per hectare per year was higher for LA than for LN pastures (377 vs. 264 kg) over the 3 yr of grazing. Although LN pastures are easier to manage and have a longer grazing season, these data indicate that gain per animal and gain per hectare can be increased during midsummer through early fall by growing aeschynomene with limpograss.
AGASSISTANT: an Artificial Intelligence System for Discovering Patterns in Agricultural Knowledge and Creating Diagnostic Advisory Systems
Authors: Fermanian T. W. , Michalski R. S. , Katz B. , Kelly J.
Published: July 2010

AGASSISTANT is a non‐specialist artificial intelligence system for automatically determining, refining, and evaluating diagnostic rules and patterns for agricultural decision problems. It has the ability to create general decision rules from examples of expert decisions. It can provide advice using these self‐created rules or rules supplied by a system creator, and can also serve as a tool for developing expert or advisory systems. AGASSISTANT was first applied to build WEEDER, a system for identifying 37 grass weed or turf species commonly found in turfs in the USA. To evaluate WEEDER's potential for exclusive identifications, a program was developed to produce all possible combinations of variable values which lead to an exclusive identification of any grass represented in the system. For most grasses, there were multiple ways (x̄ = 4) of identifying each grass exclusively among all other grasses. Each identification required the selection of a value for an average of five variables. The maximum number of variable value decisions required for an identification was seven and the minimum was four. More than one‐half (59%) of the identifications required a decision on five or less variables. WEEDER was found to be as efficient in the number of decisions required for an identification as the theoretical maximum efficiency (5 leads) for a dichotomous key covering the same species. WEEDER represents an improvement over current methods of plant identification (e.g. identification keys) due to its ability to identify specimens through multiple sets of plant variables, use uncertain knowledge, allow the user to answer questions in any order, and be easily modified to reflect local differences in plant populations. AGASSISTANT provided the total environment for the initial representation and organization of the WEEDER knowledge base and serves as its final delivery medium.
Plant Tissue Tests for Predicting Nitrogen Fertilizer Requirements of Winter Wheat
Authors: Roth G. W. , Fox R. H. , Marshall H. G.
Published: July 2010

Field experiments were conducted to evaluate three plant tissue tests for estimating the need for supplemental nitrogen (N) fertilization of ‘Tyler’ winter wheat (Triticum aestivum L. em Thell) in Pennsylvania. The tests were used between Feekes growth stages (GS) 3 and 6, and measured stem nitrate concentration, whole‐plant Kjeldhal‐N concentration, and crop N uptake. The accuracy of a test for predicting N deficiency was evaluated in four to eight experiments conducted on either Hagerstown (fine, mixed, mesic, Typic Hapludalfs) or Murrill (fine‐loamy, mixed, mesic Typic Hapludults) soils. Spatial variability of the test procedures was evaluated at GS 4 in a 0.25 ha area of a production wheat field. In a third study the temporal variability of each test procedure was monitored during 37 and 25 d periods in 1985 and 1986, respectively. The whole‐plant N concentration accounted for the most variation in relative yields, had the lowest spatial variability, and appeared to be best suited for the current wheat management system in Pennsylvania. The wholeplant N concentrations necessary to produce 90% of the maximum yields or critical levels, were 39.0, 35.0, and 26.5 g N kg−1 for GS 4, 5, and 6, respectively. The stem nitrate tissue test was most sensitive to short‐term changes in the soil N supply. The critical level for the stem nitrate test did not fluctuate more than 10% between growth stages and averaged 2.15 g kg−1 NO3−N. The N uptake test was the weakest predictor of N deficiency, had the largest spatial variability, and was affected by factors that limited crop dry matter production.
Carbohydrate, Nitrogen, and Phosphorus Concentrations of Spring Wheat Leaves and Stems
Authors: Frank A. B. , Bauer A. , Black A. L.
Published: July 2010

Tillers which produce a spike on spring wheat (Triticum aestivum L.) contribute greatly to grain yield. Management practices and environmental factors influence tiller survival, but mechanisms that contribute to survival are not well understood. Leaves and stems from the main plant and all tillers grown in the field under two N and two water levels were separated and analyzed for water soluble carbohydrates (WSC), N, and P concentration. Concentrations of WSC were greater in stems than in leaves for all treatments, with concentrations in stems increasing rapidly as plants developed, while concentration of WSC in leaf tissue changed only slightly during development. Main plant stems had higher WSC than tiller stems and WSC of tiller stems decreased as tiller position increased from the main stem to T3. Leaf and stem N and P concentrations decreased for all treatments as plants developed morphologically. On most sample dates, leaf tissue had higher N concentrations than stems, but stems had higher P concentrations than leaves. Results were not conclusive as to the role of N, P, or WSC in determining tiller number and survival in spring wheat, but the tissue analyses suggest that WSC concentrations in stems are an important factor in determining total tiller number and survival. The plants that are most vigorous during vegetative development have a greater potential to produce tillers that survive and contribute to grain yield.
Mitscherlich‐Bray Equation Used to Correlate Soil Phosphorus and Potato Yields
Authors: Payton F. V. , Rhue R. D. , Hensel D. R.
Published: July 2010

Very little is known about the response of potato (Solanum tuberosum L.) to P in northeast Florida where potato is a major winter crop. The purpose of this study was to correlate tuber yields with Mehlich‐I extractable soil and fertilizer P. Dolomitic lime was applied to an Ellzey sand (sandy, siliceous, hyperthermic Arenic Ochraqualfs) in 1977 at rates of 0.0, 2.2, 4.5, and 9.0 Mg ha−1, and resulted in average soil pH levels of 4.8, 5.4, 6.1, and 6.5 during the 5 yr of the study. In 1978 four rates of P were superimposed on lime treatments to establish a range of residual soil P levels for use in subsequent years of the study. In the following years, plots were fertilized with either no P (residual) or with P at planting. Data from 1981 were used to estimate the various parameters of the MB model, which related tuber yields to a linear function of soil and fertilizer P referred to as total effective P (TEP). Between 1979 and 1982 the percent yield was found to decrease with time by 20 to 70%, depending on the soil pH and Mehlich‐I P level. The decrease in relative yield was more rapid at pH 6.5 than at 5.4. The decrease in yield appeared to be the result of a decrease in availability of residual soil P, which was not accompanied by a decrease in Mehlich‐I extractable P.
Using Time‐Domain Reflectometry to Measure Soil Water in Hawaiian Sugarcane
Authors: Grantz D. A. , Perry M. H. , Meinzer F. C.
Published: July 2010

Time‐domain reflectometry (TDR) has been suggested as a convenient technique for quantifying soil water in agronomic experiments. Sampling protocols and installation techniques remain to be described and the validity of a “universal” calibration equation remains to be tested in Ferich volcanic soils. Thus, TDR was evaluated in this study for measurement of volumetric soil‐water content in an extensive sugarcane field in Hawaii. Matched pairs of probes, 0.359 m and 0.725 m long, were installed vertically at various distances from the drip irrigation line at six locations in a well‐watered field. This sampling protocol resolved the diurnal depletion of soil water due to evapotranspiration and the decline in soil water wilh distance from the drip inrigation line, both occurring largely within the surface 0.36 m of soil. Independent measurements of soil‐water content using gravimetric methods confirmed the accuracy of the TDR determinations and validated a universal calibration for Ferich Hawaiian soils. A rapid technique was developed to install probes, which remained functional throughout the 2‐yr crop cycle. Use of spaced arrays of TDR probes is safer, more convenient, and more suited to automation of data acquisition, reduction, and analysis, than conventional methods of assessing volumetric water content.
Plant and Nitrogen Yield of Barley‐Field Pea Intercrop in Cryoboreal‐Subhumid Central Alberta
Authors: Izaurralde R. C. , Juma N. G. , McGill W. B.
Published: July 2010

Growing legumes with cereals may increase both yield and protein of livestock‐feed crops as well as the quantity of N returned to soil. This study examined: (i) if barley‐field pea intercropping has advantage over sole barley (Hordeum vulgare L.) for grain and N yield and (ii) the interactions between fertilizer N and seeding densities of barley and field pea (Pisum sativum L.). In 1986 and 1987, crop and N yields of barley and barley‐pea were compared on a Malmo silt loam (Typic Cryoboroll) and a Breton loam (Typic Cryoboralf). In 1987, fertilizer N (0 and 80 kg N ha−1) and seeding density (0, 86,172, 258 seeds m−2 of barley; and 0, 25, 50, 75 seeds m−2 of field pea) effects on intercrop yield were determined on the Malmo soil. In 1986, intercropped‐barley yields at both sites were similar to sole crop yields due to low pea competition; but in 1987, they were 35 to 40% lower than sole crop yields. In three of four location‐years, grain‐N yield was higher in the intercrop than in sole barley. Nitrogen returned to soil in barley‐pea residues was at least 22% higher than in barley straw. Of the intercrop components, only barley‐straw yield increased when fertilized with 80 kg N ha−1. Peagrain yields were not affected by barley seeding rates; but barley yields decreased linearly when pea density increased from 0 to 75 seeds m−2. Fertilizer N did not interact with seeding densities of barley and pea. Area × Time Equivalent Ratios indicated an advantage of intercropping over sole cropping in N but not in plant yield. Barley‐pea intercrops, each species seeded at half its sole rate, appear to increase N production in grain and straw over sole cropping under both soil‐climate conditions.
Development of Diagnosis and Recommendation Integrated System Norms for Bahiagrass
Authors: Payne G. G. , Rechcigl J. E. , Stephenson R. J.
Published: July 2010

Bahiagrass (Paspalum notatum Flugge) is grown on more pasture land in Florida than all other pasture‐grasses combined. Despite the large amount of bahiagrass grown annually, there is a surprising lack of information concerning the nutrient requirements of bahiagrass‐pastures. Currently, fertilizer recommendations for all nutrients, especially micronutrients. The Diagnosis and Recommendation Integrated System (DRIS) was developed to make an interpretation from the results of the chemical analysis of a plant tissue sample from which an accurate fertilizer recommendation could be made. The DRIS represents a holistic approach to interpreting tissue analyses. This study was conducted to develop DRIS norms for bahiagrass‐pastures and to evaluate the accuracy of those norms. A database, from which the DRIS norms were determined, was assembled by collecting 857 bahiagrass‐pasture samples from ongoing bahiagrass field fertility trials located in nine counties throughout central Florida and analyzing the samples for N, P, K, Ca, Mg, Fe, Mn, Zn, and Cu. At the time of sampling, forage yields were also determined. When DRIS norms were applied to data from an independent study in which bahiagrass was grown in greenhouse solution culture, known nutrient deficiencies were accurately diagnosed. The nutrients limiting bahiagrass forage yields in a fertility trial conducted under field conditions were also correctly identified by the DRIS interpretation of the tissue analyses. The results obtained during this study indicate that the DRIS can be successfully applied to bahiagrass grown and sampled under a wide range of conditions. Therefore, it appears that the DRIS developed for bahiagrass can provide very useful information from which nutrient deficiencies can be readily and correctly identified and more accurate fertilization programs can be developed for bahiagrass‐pastures.
Yield and Regrowth Characteristics of Alfalfa Grazed by Steers during Spring and Summer
Authors: Wolf D. D. , Allen V. G.
Published: July 2010

Current recommendations for grazing alfalfa (Medicago sativa L.) include grazing for a few hours or days when plants are near a haycut stage. This study investigated the influence of continuous grazing of ‘Arc’ alfalfa by steers (Bos taurus L.) during spring (38 d), summer (26 d), or both on plant growth, potato leafhopper (Empoasca fabae Harris) population, and subsequent hay yields. Three grazing and one nongrazed treatments were imposed during 1986 and 1987 on Groseclose silt loam (clayey, mixed, mesic Typic Hapludults). Treatments included: (i) spring grazing started when alfalfa height was approximately 10 cm, followed by three hay harvests; (ii) hay harvested twice, followed by summer grazing that started when alfalfa height was approximately 15 cm, followed by one hay harvest; (iii) both spring and summer grazing as described above with hay harvested after the second and fourth growth cycles; and (iv) nongrazed with hay harvested four times. No grazing was imposed during 1988 when hay was harvested four times to measure the influence of previous grazing. In 1986 and 1987, hay yields following spring grazing (6.61 Mg ha−1) were not different than those for nongrazed (6.47 Mg ha−1). Fall hay yields following summer grazing (1.39 Mg ha−1) and spring plus summer grazing (1.34 Mg ha−1) treatments were lower than for spring grazing (1.85 Mg ha−1) or nongrazed treatments (1.80 Mg ha−1). Grazing had no influence on root total nonstructural carbohydrates at the end of Year 2. Grazing for 2 yr by any treatment had no effect on yields during Year 3 when alfalfa was harvested four times for hay. Potato leafhopper density increased during regrowth following summer grazing to a level of 11.5 insects per sweep that required insect control, whereas little buildup occurred following hay harvest during the same growth period. Our data show that grazing, begun in spring or summer at a young vegetative stage, can continue for a time equal to a growth cycle in either or both seasons of at least 2 yr with no detrimental effect on alfalfa hay yield in Year 3.
Nitrogen Effects on Yield and Malting Quality of Barley Genotypes under No‐Till
Authors: Clancy J.A. , Tillman B.A. , Pan W.L. , Ullrich S.E.
Published: July 2010

Conservation practices, such as reduced tillage and improved fertilizer use, are desirable from an environmental perspective and may yield economic benefits if production and quality are not impaired. This study was conducted to determine the effects of two N fertilization levels, 45 and 90 kg ha−1 (50 and 100% of normal grower rates), on yield and malting quality of spring barley (Hordeum vulgare L.) under no‐till management. The study was conducted in 1986 and 1987 on a Palouse silt loam (fine‐silty, mixed mesic Pachic Ultic Haploxeroll). Seven Nordic (Europe) genotypes were compared with four U.S. Pacific Northwest (PNW) cultivars. The higher N level increased grain yield across genotypes in both years (17% in 1986, 5% in 1987), reduced the percentage of plump kernels (4%) in 1987, and did not affect test weight, 1000‐kernel weight, or percentage of thin kernels. All Nordic genotypes yielded less than the PNW cultivars except the Danish cultivar Nordal. Higher N increased total malt protein (7%) in both years and soluble malt protein (7%) in 1986. Higher N also significantly increased a‐amylase (25%) and diastatic power (15%) in the malt, while malt extract was unaffected. Significant genotypic differences existed for all agronomic and malting parameters examined. Under no‐till, HJA 78003 was the only Nordic genotype that produced good quality malt, equaling the three PNW malting cutlivars under no‐till. The higher N rate produced slightly better yield and quality than the reduced rate. Therefore, reducing the N rate to half the normal grower rate (90‐45 kg ha−1) would probably not be recommended under these test conditions. Overall, the PNW cultivars tested outperformed the Nordic genotypes both in yield and malting quality. However, Nordal and HJA 78003 could prove useful in PNW barley breeding programs.
Improved Nitrogen Management in Irrigated Durum Wheat Using Stem Nitrate Analysis: II. Interpretation of Nitrate‐Nitrogen Concentrations
Authors: Knowles T.C. , Doerge T.A. , Ottman M.J.
Published: July 2010

Attempts to characterize the N status of irrigated spring wheat (Triticum aestivum L.) using basal stem nitrate‐N (NO3‐N) tissue tests have shown contradictory results due to the narrow range of agronomic conditions existing in most studies. Five field experiments were conducted in southern Arizona to examine the effects of N rate, mobility of N fertilizer form, residual soil N, soil texture, and two contrasting cultivars on basal stem NO3‐N concentrations, yield and quality of irrigated durum wheat (Triticum turgidum L. var. durum). Fertilizer N treatments were broadcast at planting, then at Feekes 5,10, and 10.5 growth stages (GS) to simulate fertilization in conjunction with the first four basin irrigation events. Stem tissue samples were taken from all plots at GS 2, 5, 6, 10, and 10.5 for NO3‐N analysis. A critical level of 2000 mg NO3‐N kg−1 in durum wheat stem tissue at GS 2 through 5 was suggested. Critical wheat stem tissue NO3‐N concentrations of 1000 mg kg−1 at GS 6 through 10 and 500 mg kg−1 at GS 10.5 were also defined. Significant grain yield reductions due to excessive N fertilizer applications resulted when stem tissue NO3‐N concentrations exceeded 6000,5000,4000, 3000, and 2000 mg kg−1 at GS 2, 5, 6, 10, and 10.5, respectively. Optimum durum wheat grain yield and quality occurred when basal stem tissue NO3‐N concentrations ranged from 3000 to 4000, 2500 to 3500,1000 to 1500,500 to 1000, and 200 to 500 mg kg−1 at GS 2,5,6, 10, and 10.5, respectively. These results should prove useful in predicting the N needs of irrigated durum wheat grown under arid and semi‐arid conditions.
Sward Dynamics and Herbage Nutritional Value of Alfalfa‐Ryegrass Mixtures
Authors: Jung G. A. , Shaffer J. A. , Rosenberger J. L.
Published: July 2010

No grass species has proven to be well suited as a companion grass in binary mixtures with alfalfa, Medicago sativa L., over a wide range of environments and management practices. Two trials were conducted with alfalfa and perennial ryegrass, Lolium perenne L., as binary mixtures and monocultures in Pennsylvania, USA (41 °N, 77 ° 30'W) to determine the influence of seeding rate and phenological development and tillering potential of ryegrass on sward dynamics and herbage nutritional value. The experiment was seeded on Hagerstown silt loam (fine, mixed, mesic Typic Hapludalfs) soil in August 1983 and 1984 to determine consistency of sward dynamics of stands seeded in different years. Field plots were harvested in late May and after 35‐d intervals in summer, and 45 d in fall. Near infrared reflectance spectroscopy was used to estimate botanical composition of the mixtures. Nitrogen concentration and in vitro dry matter disappearance determinations were made on freeze‐dried herbage for 2 yr from one of the two trials. Botanical composition of alfalfa‐perennial ryegrass mixtures was influenced more by ryegrass seeding rate than by alfalfa seeding rate. The influence of alfalfa and ryegrass seeding rates on botanical composition was particularly large during stand establishment and the first crop year. Alfalfa became the dominant species within 1 yr in all mixtures in both trials even when conditions heavily favored ryegrass during stand establishment. Annual yield of digestible dry matter was maximized at 9.9 Mg ha−1 when alfalfa and perennial ryegrass were seeded at approximately 15 and 11 kg ha−1, respectively. Weed content of the mixtures was inversely related to seeding rate of ryegrass.
Yield and Nitrogen Fixation of Chickpea Cultivars in Response to Inoculation with Selected Rhizobial Strains
Authors: Beck D. P.
Published: July 2010

With development of new cultivars for winter sowing, production of Kabuli chickpea (Cicer arietinum L.) has expanded into drier areas of the Mediterranean region where low or less effective populations of indigenous rhizobia may limit N2 fixation. This study was conducted to quantify field N2 fixation using 15N for eight chickpea cultivars as affected by native rhizobial populations and three introduced rhizobial strains, and to determine the extent of strain‐cultivar interactions for N2 fixation and yield. Host‐by‐strain interactions for N2 fixation were highly significant in a greenhouse experiment utilizing a N‐free aseptic hydroponic system. Inoculation significantly increased total above ground dry matter (AGDM) and seed yields over uninoculated control in field trials conducted at two locations at Tel Hadya, Syria, on a Vertic Chromoxeralf soil during two seasons (1987–1989). All yield and N2 fixation parameters differed significantly among chickpea cultivars and rhizobial strains in the wetter (1987–1988) season where cultivar‐strain interactions were significant for seed yield, N yield, and N2 fixation; differences in N yield and N2 fixation were not significant in the drier season. Average quantities of N2 fixed were 68 and 27 kg N ha−1 in inoculated treatments for 1987–1988 and 1988–1989 trials, respectively. Inoculation with the best strain treatment in 1987–1988 increased the average proportion of N derived from fixation (%Ndfa) from 52% to 72%; maximum %Ndfa for this trial was 81%. Maximum %Ndfa was 67% in the 1988–1989 trial. Significant strain‐by‐cultivar interactions and the yield response to selected rhizobial strains suggest an important role for field inoculation of chickpea for increased N2 fixation.