bluuebunny/crossref_metadata_2025 huggingface dataset:
Apparatus for Measuring Water Vapor Transport at the Soil Surface
Authors: Saeed Ibrahim A. M. , Tanner C. B. , Sauer Thomas J.
Published: July 2010

To fully characterize the water and energy balances of a field crop it is necessary to separate soil evaporation from total canopy evapotranspiration. An alternative to measuring soil evaporation directly is to measure the vapor exchange at the soil surface in order to assess mass transfer there. The objective of this research was to develop a method for measuring vapor exchange coefficients beneath plant canopies. The system consists of a Mariotte siphon water supply apparatus and a felt‐covered vapor source plate, both of which were tested under laboratory and field conditions. A detailed description of the devices, their construction and operation, and a sample data set are presented. The system is suitable for long‐term field installation and is capable of accurately measuring vapor transfer rates over short time intervals.
Root Volume Effects on Nitrogen Uptake and Partitioning in Peach Trees
Authors: Ran Y. , Habib R. , Bar‐Yosef B. , Erez A.
Published: July 2010

Although soil root volume can be modified under field conditions by adjusting irrigation frequency and emitter geometry, little is known about the effect of root volume on tree growth, uptake, and yield. The objective of this work was to investigate effects of physical restriction of root systems on N absorption by peach trees [Prunus persica (L.) Batsch.] and N partitioning among tree organs, and to compare experimental data with simulated results. Cumulative NO3 uptake by 3‐ and 3.5‐yr‐old trees grown in containers increased linearly with increasing root volumes from 5 to 10, 20, 40, and 80 L tree−1. This effect was simulated better when assuming a constant ratio of N to dry matter weight in the tree than when assuming a Michaelis‐Menten uptake mechanism. Nitrogen partitioning among leaves, branches, fruits, trunk, and roots differed at fruit harvest and at the end of the season. Despite considerable differences in tree organ weights, N concentration in the tree parts was quite similar in the various root volumes and along the growing season. Simulation of N concentration in annual tree parts was less satisfactory than in perennial organs, where initial conditions could be defined accurately. It is suggested that the physical restriction of root growth reduced N uptake, root hormone synthesis rate, and N accumulation in the canopy. The trees have a N‐concentration‐stat mechanism, which maintains a constant N percentage in the tops by adjusting photosynthesis and growth in direct proportion to the N and cytokinin accumulations in the canopy.
Tracing Nitrogen Movement in Corn Production Systems in the North Carolina Piedmont: Analysis of Nitrogen Pool Size
Authors: Crozier Carl R. , King Larry D. , Hoyt Greg D.
Published: July 2010

The fate of N in North Carolina Piedmont corn (Zea mays L.) was traced using N pool size analysis. In 1989 and 1990, selected N pools [corn; weeds; surface residues; and soil NH+4 NO‐3, and potentially mineralizable N (No)] were sequentially sampled in four reduced chemical input systems: (i) crimson clover (Trifolium incarnatum L.) with conventional tillage (clover‐till), (ii) no cover crop with conventional tillage and 70 kg N ha−1 as NH4NO3 (fertilizer‐till), (iii) crimson clover with strip‐tillage (clover‐strip), and (iv) no cover crop with no tillage and 70 kg N ha−1 as NH4NO3 (fertilizer‐no‐till). The largest of the repeatedly measured N pools was soil No, which accounted for <10% of the total Kjeldahl soil N. Soil No was highest in the clover‐till treatment, and had large seasonal fluctuations: 170 to 255 kg N ha−1 in clover‐ till, and 117 to 210 kg N ha−1 in other treatments. Fertilizer treatments had higher inorganic N levels than did clover treatments only immediately after fertilizer application. Although clover shoots contained 97 to 134 kg N ha−1 yr−1, more than the N applied to fertilizer treatments, no significant differences among treatments in plant (corn + weed) aboveground N accumulation (38 to 132 kg N ha−1) were observed. Of these totals, weed N accounted for 5 to 30 kg N ha−1. Surface residue N content was highest in reduced tillage treatments. In reduced chemical input systems such as these, N transfers among soil No, weed, and residue pools may be as large or larger than N transfers among soil inorganic and crop pools.
Shoot and Root Growth Response of Perennial Ryegrass to Fertilizer Placement Depth
Authors: Murphy James A. , Zaurov David E.
Published: July 2010

A better understanding of turfgrass growth responses to the vertical placement of nutrients in the soil is needed if growth responses are to be maximized. This greenhouse work examined the shoot and root growth responses of perennial ryegrass (Lolium perenne L.) to placement of N‐P‐K fertilizer at various depths in a sandy clay loam and in a sandpeat mixture. Fertilization at the 5‐, 10‐, and 15‐cm soil depths produced greater verdure and total root mass than fertilization at 0 cm in both the sandy clay loam and sand‐peat. Root mass increases occurred within the 5‐ to 35‐cm zone of the sandy clay loam and the 10‐ to 35‐cm zone of the sand‐peat with subsurface fertilization. Water use efficiency was increased 11% in the sandy clay loam with 10 and 15 cm deep fertilization and 21% in the sand‐peat with 5 cm deep fertilization compared with surface fertilization. Except for P, nutrient accumulation with subsurface fertilization matched or exceeded that achieved with surface fertilization. Management practices that position nutrients below the soil surface and as deep as 15 cm can improve turfgrass growth responses to fertilizer. Further research needs to relate irrigation, fertilization, cultivation, and soil modification practices to fertilizer placement, and subsequently shoot and root growth responses.
Basic Linz‐Donawitz Slag as a Liming Agent for Pastureland
Authors: Rodríguez Marta , López Félix A. , Pinto Miriam , Balcázar Natalia , Besga Gerardo
Published: July 2010

Linz‐Donawitz (LD) slag, a by‐product of the iron and steelmaking industry (29% Ca, 5% Mg w/w) produced in large quantities in Europe, poses a substantial disposal challenge. A field assay was conducted to study whether LD slag could be used as a dolomitic liming agent for pastures. Six slag rates (0, 1000, 1500, 3000, 5000, and 7500 kg ha−1), with or without NPK fertilizer, were investigated for their effects on soil properties, mineral concentrations of forage, and forage yield at Bizkaia, Spain, on a Derio silty clay soil [fine silty, mixed (acid), mesic Typic Udorthent]. The 3‐yr study was done on a newly established pasture of perennial ryegrass (Lolium perenne L.), cocksfoot (Dactylis glomerata L.), and white clover (Trifolium repens L.). Slag application increased soil pH linearly, especially where fertilizer was not applied. The 7500 kg rate, without NPK fertilization, increased soil pH from 5.3 to 6.5. When 3000 kg ha−1 of slag was applied, the increase in soil pH was accompanied by a decrease of AI saturation percentage in the cation exchange complex, to <10%. At this rate, exchangeable Ca and Mg increased in comparison with the control, by a factor of 1.8 and 2.3, with and without fertilization, respectively. Slag application resulted in higher Ca, Mg, and P, lower K and Mn plant concentrations, and increased herbage yield. LD slag appears to be a useful liming material for correcting soil acidity on pasture soils and for increasing Ca, Mg, and P concentrations in plants.
Imbibition Response of Winter Wheat to Water‐Filled Pore Space
Authors: Studdert Guillermo A. , Wilhelm Wallace W. , Power James F.
Published: July 2010

Reduced temperature and increased bulk density associated with conservation tillage systems cause lower seed germination, seedling emergence, and early growth rates resulting in reduced plant stands. Prediction of the influence of soil condition on seed imbibition through simple soil measurements would help make agronomic decisions such as planting date and/or density. Our objectives were to evaluate the influence of soil water‐filled pore space on winter wheat (Triticum aestivum L.) seed imbibition and to assess the possibility of describing the relationship through simple mathematical models. We measured the rate of water uptake by heat‐killed wheat seeds at three levels of water‐filled pore space (WFPS: 0.35, 0.60, and 0.85) and temperature (T: 278, 283, and 288 K) and two levels of bulk density (ρb: 1.25 and 1.40 Mg m−3) in a Sharpsburg silty clay loam topsoil. The model proposed in 1972 by Blacklow to estimate seed water content (θs) after imbibing water for time t, θs(t) = (m + ot) − (m − θs(0)) e−qt, was fitted to seed water content as a function of time and initial seed water content, θs(0). This equation adequately described the process of water absorption (for 18 treatment combinations, R2 > 0.963). The model parameter o was related (R2 = 0.88) to WFPS and ρb, and q was related (R2 = 0.78) to T and WFPS. The third parameter, m, was significantly but weakly related (P < 0.01, r2 = 0.26) to initial seed weight. We showed that easily measured soil properties and simple mathematical models can be used to predict wheat seed imbibition under a variety of soil conditions.
Evaluation of the SPUR Model for Grasslands of the Northeastern United States
Authors: Stout William L.
Published: July 2010

Computer models that simulate grassland production must be valid for the ecosystem in which they are used. Our objective was to develop a grassland production data base and to use the data base to calibrate and validate a grassland production model for the northeastern United States. The SPUR (Simulation of Production and Utilization of Rangeland) model was evaluated for its ability to simulate aboveground biomass production in two physiographic provinces of northeastern USA. The model was calibrated for orchardgrass and switchgrass using one year of plant, soil, and weather data from four study sites. Calibrations mainly involved adjustment of photosynthetic rate, root‐to‐shoot ratio, temperature for root‐to‐shoot translocation, and rooting depth. Once calibrated, the model was validated by simulating aboveground biomass production for two ensuing years on the four sites. Two years of simulated biomass for the grasses agreed well with the observed biomass on all four study sites with r2 values of 0.48 for orchardgrass and 0.70 for switchgrass. The largest discrepancies between simulated and observed biomass occurred early in the spring at low levels of N fertilization. In its present form, SPUR can be used to develop production indices for cool‐ and warm‐season grasses on different soils.
Performance of Fall‐ and Spring‐Planted Durum Wheat in Western Colorado
Authors: Pearson Calvin H.
Published: July 2010

Several years of fall planting of spring types (non‐vernalization requiring) of durum wheat (Triticum turgidum L., durum group) in smallgrain cultivar performance tests in western Colorado have resulted in high grain yields with no observed plant stand losses. Comparison studies between fall and spring plantings of durum wheat have not been conducted. Field studies were conducted during 1988, 1989, and 1990 at the Colorado State University Fruita Research Center near Grand Junction to determine plant response of durum wheat cultivars to planting dates, and to study grain yield and yield component relationships of durum wheat cultivars when planted in the fall, early spring, and late spring. Fall‐ and early spring‐planted durum wheat generally had higher grain yields, test weights, kernel mass, and were taller than late springplanted wheat. Fall‐planted durum had fewer kernels per spikelet than wheat in spring plantings and a lower seed N concentration than durum in the late spring planting. Kernels per spikelet and kernel mass had the most consistent and highest direct correlations with grain yield. Our findings indicate that the potential exists to increase the productivity and widen the adaptation of durum wheat by identifying favorable temperate locations and using appropriate planting dates. Winter durum (vernalization‐requiring) cultivars developed for the USA would be useful in widening the adaptation and increasing the productivity of this class of wheat.
Recovery of Sesame from Defoliation and Growth Terminal Clipping
Authors: Tewolde Haile , Mulkey J. R. , Fernandez Carlos J.
Published: July 2010

Crop loss assessment charts and loss adjustments related to hail damage are based on studies that determine the degree of plant recovery from defoliation. Such information is lacking in sesame (Sesamum indicum L.). An irrigated study was conducted in 1989 and 1990 to determine the ability of a nonbranching sesame cultivar to recover from defoliation and growth terminal clipping applied to plants at different growth stages. The treatments included 0, 33, 66, and 100% defoliation levels and clipped vs. nonclipped growth terminals applied at vegetative (37 days after planting, DAP), flowering (48 DAP), and capsule filling (71 DAP in 1989 and 65 DAP in 1990) stages. Average seed yield of the nondefoliated nonclipped (control) treatment was 1523 kg ha−1 in 1989 and 1832 kg ha−1 in 1990. The magnitude of recovery from defoliation and growth terminal clipping was highly dependent on when the treatments were imposed. In the nonclipped treatment, the 33% defoliation treatment produced 90 to 102% as much seed as the control regardless of the growth stage. Seed yield of the 66% defoliation in the nonclipped treatment varied from 85 to 103% of the control when defoliation was imposed before heavy fruiting (54 DAP or earlier). When imposed after heavy fruiting, the 66% defoliation reduced yield by 20% in 1989 and 30% in 1990. The most severe defoliation (100%) in the nonclipped treatment yielded 93, 89, and 34% of the control in 1989 and 77, 72, and 16% of the control in 1990 when applied at the vegetative, flowering, and capsule filling stages, respectively. The magnitude of recovery from defoliation in the clipped treatments also decreased with more advanced growth stage; however, this response was more pronounced in the clipped than the nonclipped treatments. The greatest reduction in seed yield occurred when all leaves were defoliated and the growth terminal removed after heavy fruiting.
Dinitrogen Fixation by Seven Legume Crops in Alaska
Authors: Sparrow Stephen D. , Cochran Verlan L. , Sparrow Elena B.
Published: July 2010

Information on amounts of N2 fixed by legumes in subarctic regions is lacking. We determined the N2‐fixation potential of seven legume species under field conditions in subarctic Alaska. Seasonal N2 fixation was estimated for alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), yellow sweetclover (Melilotus officinalis Lam.), fababean (Vicia faba L.), lentil (Lens culinaris Medik.), pea (Pisum sativum L.), and white lupin (Lupinus alba L.) on a neutral (pH 7.2) and an acid (pH 5.4) soil during two field seasons. A lime variable was included at the acid soil location. Dinitrogen fixation was estimated by the 15N isotope dilution method and by the total‐plant N difference method. Three non–N2‐fixing crops and uninoculated analogs at one location were used as reference crops. Agreement among reference crops and between methods of estimating N2 fixation was adequate for most applications, but differences of >50 kg ha−1 were sometimes observed. Maximum N2 fixation estimates by the isotope dilution method were 58 kg ha−1 for alfalfa, 121 for red clover, 109 for sweetclover, 204 for fababean, 72 for lentil, 121 for pea, and 162 for white lupin. Liming usually did not significantly affect N2 fixation. Nitrogenase activity, as measured by the acetylene reduction assay, peaked at or soon after flowering in some legumes; in others, it either plateaued or continued to increase after flowering until the end of the growing season.
Bean Leaf Beetle Injury to Seedling Soybean: Consumption, Effects of Leaf Expansion, and Economic Injury Levels
Authors: Hunt Thomas E. , Higley Leon G. , Witkowski John F.
Published: July 2010

The bean leaf beetle (BLB) [Cerotoma trifurcata (Forster)] is a major pest of seedling soybean [Glycine max (L.) Merr.], but little is known of the effects of seedling leaf expansion on final leaf tissue loss resulting from BLB injury. This field study was conducted to (i) determine a precise daily consumption rate of BLB on seedling soybean; (ii) determine the direct and indirect reduction of leaf area resulting from BLB injury and soybean leaf expansion; and (iii) develop economic injury levels for BLB on seedling soybean. The study was conducted on a Sharpsburg silty clay loam in an ‘Elgin 87’ soybean field near Mead, NE. Experimental designs were completely random. Consumption rate treatments consisted of 2 beetles leaflet−1, in the field and laboratory. Leaf expansion treatments consisted of an uninjured check and three levels of injury. Injury (gross removal of leaf tissue) was imposed at Vegetative Stage V3 on a lateral leaflet of the fourth trifoliate leaf. Mean BLB consumption of soybean was 0.31 cm2 d−1. An injury expansion coefficient matrix was developed to estimate final leaf tissue loss at late V3. Final estimated tissue loss resulting from one BLB feeding for 1 d on an unexpanded leaf was 2.74 cm2. Final estimated tissue loss caused by one BLB feeding from Stage V1 through V3 (14 d) was 13.93 cm2. Seedling soybean yield‐loss relationships were used to calculate economic injury levels (EILs) for VC, V1, and V2 soybean. These EILs were more than twice the value of the current EIL of 1.33 beetles plant−1.
Root and Shoot Growth Responses to Salinity in Maize and Soybean
Authors: Shalhevet Joseph , Huck Morris G. , Schroeder Bryan P.
Published: July 2010

Salinity generally reduces shoot growth of crops more than root growth, based on dry weight rather than length measurements. The objective of this study was to compare changes in root length to changes in shoot height under conditions of salinity, using the minirhizotron technique. The experiment was conducted in soil containers (55 cm long, 15 cm diam.), using greenhouse‐grown soybean [Glycine max (L.) Merr.] and field‐grown maize (Zea mays L.) as test crops. Segmented, nonlinear regression analysis showed changes in root length as viewed through minirhizotron tubes to be more sensitive to salinity than changes in shoot height, while there was no response to salinity treatment for final root dry weight. The regression coefficients of changes in relative shoot and root length vs. the electrical conductivity of the soil saturation extract (ECe) were 5.3 ± 4.0% per dS m−1 for soybean shoots and 6.6 ± 4.3% per dS m−1 for soybean roots. For maize, the values were 6.9 ± 1.6% per dS m−1 for shoots and 9.0 ± 4.9% per dS m−1 for roots. The regression coefficients of relative shoot height vs. relative root length of soybean and maize were 0.61 ± 0.27 and 0.66 ± 0.20, both significantly smaller than one. The discrepancy between the response in root length as measured by the minirhizotron technique and the response as measured in final root dry weights was attributed to the fact that changes in root length, as viewed in the minirhizotron video frames, depend more on new lateral root initiation than on extension of individual existing roots. Root extension is a turgor‐dependent process, as is shoot elongation, while lateral root initiation is not turgor dependent, and thus may be more sensitive to salinity. One might also speculate that the young, thin lateral roots are more sensitive to salt stress than the older, thicker main root system. Additionally, final root weight is insensitive to the addition of lateral roots if salinity treatments are initiated after the main root system is established, as was the case in this experiment.
Selection for Reproductive Stage Drought Avoidance in Rice, Using Infrared Thermometry
Authors: Garrity Dennis P. , O'Toole John C.
Published: July 2010

Water deficits cause major yield reductions on the world's rainfed riceland. The most severe water deficits occur during the reproductive phase. Differences in canopy temperature among crop cultivars are known to be related to drought avoidance characters. In developing a practical field screening system for reproductive phase drought resistance in rice (Oryza sativa L.), we assessed the canopy temperature response of a range of germplasm, and related the results to other plant characters related to drought resistance. Field experiments were conducted on a silty clay loam Typic Hapludoll at the International Rice Research Institute. Planting of the test cultivars was staggered, to synchronize flowering during the water‐deficit period. Canopy temperature measurements were made on 12 dates in Trial 1 and 8 dates in Trial 2. Mean canopy temperatures (Tc) increased from 28 to 37°C during the stress period. Grain yield (r2 = −0.63**) and spikelet fertility (r2 = 0.51**) were related to midday Tc on the day of flowering. Highly significant differences were observed in canopy temperature among entries, with low coefficients of variation (2.0–2.7%). Entries with a history of outstanding vegetative stage drought screening scores consistently remained coolest under stress. Visual drought tolerance scores (r = 0.72**) and leaf rolling scores (r = 0.68**) were correlated with mean canopy temperatures under moderate water stress, but not under severe stress (r = 0.31NS; r = 0.21NS). Infrared thermometry was judged well‐suited to monitor the progression of crop water stress development, and to aid in classifying cultivars for relative drought avoidance. However, caution is necessary to assure proper application of the technique and in data interpretation.
Implications of Nitrogen Management Strategies for Nitrate Leaching Potential: Roles of Nitrogen Source and Fertilizer Recommendation System
Authors: Durieux Robert P. , Stewart E. J. , Zhao J. Q. , Magdoff Frederick R. , Jokela William E. , Brown Hugh J.
Published: July 2010

Using the soil‐based pre‐sidedress nitrate test (PSNT) rather than the yield‐goal‐based cropping and manure history (CMH) to recommend N for corn (Zea mays L.) frequently results in less N applied. Our objectives were (i) to determine if this reduction in N application substantially reduces the potential for N leaching and (ii) to compare dairy manure and commercial fertilizer as N sources, both within PSNT‐based systems. The 4‐yr field study included (i) a control (no manure or N fertilizer), and three N fertilizer rates based on (ii) PSNT, no manure added (PSNT−M); (iii) cropping and manure history (CMH), no manure added; and (iv) dairy manure application with additional sidedress N if recommended by the PSNT (PSNT + M). The PSNT − M treatment received 112 kg N ha−1 in 1990 and 123 kg N ha−1 in subsequent years, while the CMH treatment received 168 kg N ha−1 in all 4 yr. Corn yield, N uptake (defined as net aboveground N accumulation), spring and fall soil NO‐3 levels, and overwinter NO3‐N losses were measured. Silage yields of PSNT + M generally were greatest (average of 16.5 Mg ha−1), followed by PSNT−M and CMH treatments, which were similar (14.8 Mg ha−1). The CMH system resulted in the highest soil NO3‐N levels (to 120 cm) at harvest and greatest overwinter net profile NO3‐N loss (average 66 kg ha−1). The results indicate (i) a reduced residual N after harvest and therefore reduced potential for N leaching when using the PSNT for N recommendations and (ii) similar or higher yields using manure compared with commercial fertilizer.
Planting and Harvest Date Effects on Productivity and Root/Shoot Quotient of Four Brassica Cultivars
Authors: Jung Gerald A. , Shaffer John A.
Published: July 2010

Summer‐planted turnip (Brassica rapa L.) is a highly productive crop, and may allow farmers to extend the grazing season and lower animal production costs. A field study was conducted to determine the influence of planting date and harvest date on morphological development and productivity of leafy plants like turnip in late fall. Turnip and a spinach ✕ mustard hybrid were seeded in rows on Hagerstown silt loam soil (fine, mixed, mesic Typic Hapludalfs), using a factorial treatment structure (6 planting dates ✕ 4 cultivars) in a split‐plot design, with planting date as whole plot, cultivar as subplot, and four replicates. Three to six harvest dates were used, depending on planting date, resulting in an overall incomplete factorial treatment structure. Mean yield of all cultivars with optimal planting date‐harvest date combinations was 11.5 Mg ha−1 without severe foliar disease and 9.7 Mg ha−1 with alternaria leaf spot (caused by Alternaria spp.). The interaction of planting date and harvest date on morphological development depended on resource allocation characteristics of the cultivar for top and root production. Delay of planting from late July to late August decreased top and root production more in 1990 than 1989. An optimum harvest date for maximizing fall top yield occurred each year regardless of planting date. Root yields increased in November and early December, whereas top yields did not. In general, total yields were high for crops planted in late July and harvested in late October or early November. Top/root quotient (top yield divided by root yield) was increased by delaying summer planting, and decreased by delaying fall harvest. Savanna had the highest, and Purple Top had the lowest top/root quotient. Turnip offers very high production potential for late‐fall grazing, with a wide range of top/root yields.
Growth and Nutrient Uptake of Wheat in Clinoptilolite‐Phosphate Rock Substrates
Authors: Allen Earl R. , Ming Douglas W. , Hossner Lloyd R. , Henninger Donald L. , Galindo Charlie
Published: July 2010

Mixtures of zeolite and phosphate rock react to release cations and anions into soil solution through dissolution and ion exchange. These mixtures have the potential to serve as slow‐release sources of nutrients in synthetic soils. The term zeoponics has been used to describe such systems. Research was conducted to monitor dry matter production and nutrient uptake of wheat (Triticum aestivum L.) in a zeoponic system containing phosphate rock and NH4‐ and K‐saturated zeolite. The objective was to evaluate the ability of zeolite and phosphate rock to provide a balanced supply of N, P, K, and Ca for plant growth. Two zeolite samples (San Miguel and Wyoming clinoptilolite) and two phosphate rock samples (North Carolina and Tennessee phosphate rock) were combined factorially to form four zeoponic mixtures. A series of synthetic soils was formed by combining selected rates of each zeoponic mixture with acid‐washed quartz sand. Zeoponic rates (ZR) were 1, 5, 10, 25, 50, 75, and 100% (v/v) of the synthetic soil. Pots were placed in a growth chamber after planting, and plants were harvested every 45 d for a 225‐d period. Foliar spray supplied essential nutrients other than N, P, K, and Ca. High yields of wheat dry matter were produced through several cuttings when at least 25% of the synthetic soil was comprised of the zeoponic mixture and when the zeoponic mixture contained a highreactivity phosphate rock (North Carolina). Tissue analyses suggested that K, and to a lesser extent N, limited wheat growth when ZR ≤ 10%. Calcium limited wheat growth at ZR > 10% when a low‐reactivity phosphate rock (Tennessee) was used, but not when a high‐reactivity phosphate rock (North Carolina) was used. Properly formulated zeoponic mixtures of San Miguel or Wyoming clinoptilolite and North Carolina phosphate rock are capable of supplying sufficient levels of N, P, K, and Ca for intensive growth of wheat.
Influence of Alfalfa Escapes on Estimating Spring Barley Yield
Authors: Krall James M. , Miller Stephen D. , Legg David E.
Published: July 2010

In Wyoming, spring barley (Hordeum vulgare L.) can follow alfalfa (Medicago sativa L.) in irrigated rotations. To avoid serious wind erosion, this conversion should be done using conservation tillage. However, this can be complicated by alfalfa escapes. The relationship between the level of established alfalfa interference and barley is unknown. Establishment of the season‐long impact of alfalfa escapes on barley yield would be important for crop‐loss assessment. Forecasting the impact on production would be valuable as a decision making tool. The objective of this study was to estimate yield losses from season‐long interference of alfalfa escapes and to forecast impact of alfalfa escapes on spring barley yield. Replicated field studies were conducted under sprinkler irrigation at a site near Torrington, WY. Herbicide treatments were used to provide for barley production across a range of levels of alfalfa interference. Barley yield response was regressed on various measures of alfalfa infestation. Consistency of regression over years for barley yield on end‐of‐season alfalfa stand or alfalfa yield allowed for simple interpretation of the expected barley yield reduction, as well as calculation of the expected barley yield given a specific level of alfalfa infestation. Use of a growing season visual assessment of alfalfa control did not result in consistency of regression slopes over years. Calculation of an expected barley yield based on models developed using alfalfa stand and alfalfa yield was accomplished. The predictors are −84.747 and −0.5577 for alfalfa plants 0.5 m−2 and kg ha−1 alfalfa yield, respectively.
Methods for Soil Infestation with Striga hermonthica Seeds
Authors: Berner Dana K. , Ikie Felix O. , Aigbokhan Emmanuel I.
Published: July 2010

Field screening of maize (Zea mays L.) and sorghum [Sorghum bicolor (L.) Moench] can be an efficient means of selecting for resistance to the parasitic plant Striga hermonthica (Del.) Benth. Spatial variability in natural S. hermonthica seed infestations necessitates supplemental infestation for effective field screening. For uniformly heavy levels of infestation, sieved sand has been used as a carrier material for the extremely small S. hermonthica seeds, and a 7‐ to 14‐d waiting period between infestation and planting is often provided to environmentally condition the S. hermonthica seeds for germination and uniform infection. These steps are labor‐intensive, requiring sieving of large amounts of sand and separate infestation and planting times. The objective of this study was to develop alternative soil infestation methods for S. hermonthica seeds that require less labor and produce levels of infection comparable to standard procedures. Nine different methods of soil infestation with S. hermonthica seeds were tested in a screenhouse and in two field locations on maize and sorghum cultivars. To assess effectiveness of the methods, S. hermonthica emergence and host yield were measured. Infestation using sand as a carrier material followed by a 14‐d in situ conditioning period resulted in the greatest amount of infection in the screenhouse. In the field, methods that employed no conditioning period, and thus allowed infestation and planting on the same day, produced levels of infection comparable to methods with 7‐ and 14‐d preplant conditioning periods. The most easily accomplished of these methods used water as the carrier material, producing levels of infection equivalent to methods using sand.
Chain Diking Effects on Runoff and Winter Wheat Production
Authors: Wiedemann Harold T. , Clark Lewis E.
Published: July 2010

The major factor limiting crop production in the Texas Rolling Plains is water, and better methods of conserving soil water in dryland wheat production are needed. Chain diking is a novel method of forming basins on flat‐tilled land to impound and conserve water received from precipitation. The objective of this research was to determine the influence of chain diking on dryland winter wheat (Triticum aestivum L.) yield and on runoff during the growing season. The study site, in northwest Texas, has an annual mean rainfall of 632 mm and a cropping season average of 444 mm. Following September drill‐seeding of wheat, plots were chain diked or not diked. All other cultural practices were the same for all plots. Exit flumes and automatic recording devices were installed to measure runoff from each plot during the growing season. Grain was harvested in June. Diking reduced runoff an average of 40% (P = 0.02), which amounted to 1.0 ha‐cm over three crop years, compared with tillage without diking. The increase in wheat grain yield from diking was not significant over four crop years (P = 0.75). When analyzed by year, diking increased yields 11% (277 kg ha−1; P = 0.02) in 1989, when cropping‐season rainfall was 22% below average. The probability of receiving rainfall below average by more than 20% during the cropping year is 30%, based on 88‐yr records at this test site. Diking following planting apparently will be valuable less than 30% of the time, although other applications for chain diking are possible.
Experimental Design Factors Affecting Error Variation in Orchardgrass
Authors: Casler M. D. , Tageldin M. H.
Published: July 2010

Several experimental design factors over which the researcher has control may affect the precision of field experiments. The objective of this experiment was to identify the effects of changing plot size, incomplete block size, and incomplete block shape on precision of forage yield and quality estimates in orchardgrass (Dactylis glomerata L.). Orchardgrass seed was planted uniformly into 288 plots of various sizes. Forage yield, in vitro dry matter digestibility (IVDMD), and neutral‐detergent fiber (NDF) were determined over a 2‐yr period. Error variances (Vw) were computed for variously sized incomplete blocks (in one or three strips and from 1 to 12 plots strip−1) within each plot size and expressed as log(Vw). Values of log(Vw) for IVDMD and NDF concentration were unaffected by experimental design factors. Values of log(Vw) for forage yield increased with increasing number of plots per strip, but these effects varied among plot sizes and for one‐ vs. three‐strip blocks. Three‐strip blocks had a mean log(Vw) 71% greater than one‐strip blocks, an effect that could be offset only by doubling the number of replicates in a field test. To obtain maximum precision in cases where a large number of replicates impossible or impractical, orchardgrass field experiments should employ incomplete block designs, particularly when limited seed stocks or land requires a plot size near 1.4 m2. Incomplete block designs with this plot size should not contain multiple strips within incomplete blocks.
Environment Affects the Corn and Soybean Rotation Effect
Authors: Porter Paul M. , Lauer Joseph G. , Lueschen William E. , Ford J. Harlan , Hoverstad Tom R. , Oplinger Edward S. , Crookston R. Kent
Published: July 2010

Corn (Zea mays L.) and soybean [Glycine max (L.) Merr.], the backbone of Midwestern crop production, respond to rotation, but how growing conditions affect this is not well documented. Our objectives were to determine the effect of various corn and soybean cropping patterns on yields and to evaluate environmental effects on the rotation effect. The study began in 1981 at Lamberton, MN, on a Webster clay loam (fine‐loamy, mixed, mesic Typic Endoaquoll), in 1982 at Waseca, MN, on a Nicollet clay loam (fine‐loamy, mixed, mesic Aquic Hapludoll), and in 1983 at Arlington, WI, on a Plano silt loam (fine‐silty, mixed, mesic Typic Argiudoll). Cropping sequences were (i) continuous monoculture of each crop; (ii) annual rotation of the two crops; and (iii) 1, 2, 3, 4, and 5 yr of each crop following 5 yr of the other crop. Results are based on 11 yr of data at Lamberton, 8 yr (soybean) or 9 yr (corn) at Waseca, and 9 yr at Arlington. Corn rotated annually with soybean yielded 13% more, and 1st‐yr corn following multiple years of soybean yielded 15% more than continuous corn. Soybean annually rotated with corn yielded 10% more, and 1st‐yr soybean following multiple years of corn yielded 18% more than continuous soybean. The crops differed in response to increasing years of consecutive planting: 2nd‐yr to 5th‐yr corn yields were no different from continuous corn yields; 2nd‐yr soybean yielded 8% more than continuous soybean, 3rd‐yr soybean yielded 3% more, and 4th‐ and 5th‐yr soybean yielded the same as continuous soybean. Relative increase in yields of both crops in annual rotation compared with monoculture was approximately twofold greater in low‐yielding than in high‐yielding environments. In low‐yielding environments, the yield advantage of an annual rotation of corn and soybean compared with monoculture was frequently greater than 25%. The commonly practiced annual rotation of corn and soybean maximized corn yields, but not soybean yields, relative to the other sequences studied.
Modefying a Carter Flail Forage Harvester to Stabilize the Weighing System
Authors: Hall Marvin H. , Todd Richard F. , Hoffman Lynn D. , Everhart James R.
Published: July 2010

The single bending‐beam load‐cell weigh system that is standard equipment on a Carter flail forage harvester allows the forage collection weigh basket to pitch and sway. This movement can allow some forage to be lost when it is blown past the basket. In addition, this movement requires additional time for the basket to stabilize at the end of each plot before a weight can be recorded. A specialized frame with three bending‐beam load cells was designed and constructed to restrict movement of and to support the forage collection weigh basket. Total cost of materials for this modification was about $750. The modifications can be completed with normal shop tools and are readily interfaced with standard equipment on the Carter harvester. The modified support bracket and weigh system performed well, harvesting nearly 10 000 forage plots annually. Compared with the single bending‐beam load cell weigh system, the modified support bracket and weigh system reduced pitch and sway of the forage collection weigh basket, was equally precise, and required an average of 7 s less for the basket to stabilize at the end of each plot.
Estimation of Direct, Residual, and Total Effects of Canopy Treatments Affecting Intake by Grazing Cattle
Authors: Dougherty Charles T. , Cornelius Paul L.
Published: July 2010

Effects of transient treatments imposed on grazing cattle diminish over time but many experimental designs and statistical analyses only estimate integrated responses. We describe a change‐over design that estimates direct, first residual, second residual, and overall effects of three treatments (water, saline solution, or syrup solution) applied to alfalfa (Medicago sativa L.) canopies on the ingestive behavior of Angus cows (Bos taurus L.). Syrup‐treated canopies evoked a direct effect. Animals grazed water‐treated canopies at 32 bites min−1 and ingested herbage dry matter (DM) at 0.55 kg 100 kg−1 body mass h−1, while others grazed syrup‐treated canopies at 48 bites min−1 (P < 0.01) and ingested herbage DM at 0.64 kg 100 kg−1 h−1 (P < 0.01). As residual effects were not significant (P > 0.05), the animal responses to syrup‐treated canopies were considered preingestive responses and were attributed to enhanced sweetness. Salt‐treated alfalfa canopies, conversely, had no direct (immediate) effect (P > 0.05) on herbage intake, but summed first and second residual effects, expressed the day after application of NaCl, revealed that animals grazing untreated and syrup‐treated alfalfa ingested DM at 0.47 kg 100 kg−1 h−1, while those grazing salt‐treated alfalfa ingested herbage DM at 0.55 kg 100 kg−1 h−1 (P < 0.05). The residual effects of salt were considered postingestive responses and were attributed to Na deficiency. Change‐over designs that estimate direct and residual effects of treatments may be used to determine preingestive and postingestive components of intake.
Potato Yield Response and Nitrate Leaching as Influenced by Nitrogen Management
Authors: Errebhi Mohamed , Rosen Carl J. , Gupta Satish C. , Birong David E.
Published: July 2010

Nitrogen management for irrigated potato (Solanum tuberosum L.) is important from both a production and environmental standpoint. Nitrogen deficiency can limit yield, while excessive N can leach to groundwater. The objective of this study was to investigate the effects of early‐season N management on irrigated ‘Russet Burbank’ potato yield, N recovery, and NO3‐N leaching. A 2‐yr experiment was conducted on a Hubbard loamy sand (Udorthentic Haploborolls), using four N treatments and a 0 N control. Total N applied was 270 kg N ha−1; the portion applied at planting was 0, 45, 90, and 135 kg N ha−1, with the remainder applied in equal quantities at emergence and hilling. In 1991, increasing the amount of N applied at planting did not affect total yield, but significantly increased the yield of nonmarketable tubers. In 1992, total yield again was not affected, but the yield of smaller tubers significantly increased and the yield of larger tubers decreased as the proportion of N applied at planting increased. During 1991, when heavy leaching occurred, an average of only 33% of applied N was recovered by the crop. In contrast, during 1992, when fewer leaching events occurred, recovery of N averaged 56%. In both growing seasons, the amount of NO3‐N leached increased linearly as the proportion of N applied at planting increased. The strategy of reducing N application at planting for irrigated Russet Burbank potato can reduce the potential for NO3‐N leaching, increase N uptake, and improve marketable yield.
Previous‐Crop Effects on Sugarcane Responses to Nitrogen Fertilization
Authors: Wiedenfeld Robert P.
Published: July 2010

Nitrogen fertilizer recommendations have been developed for sugarcane (Saccharum officinarum L.) based on numerous fertility trials, with the primary variables affecting those recommendations being soil type and crop age. Cropping history influences subsequent crop responses to N fertilization, but such effects have not been determined for sugarcane. The objective of this research was to evaluate previous‐crop effects on sugarcane growth and response to N fertilization. Eight 2‐yr previous‐crop treatments consisted of N‐fertilized and unfertilized corn (Zea mays L.), sorghum [Sorghum bicolor (L.) Moench], and cotton (Gossypium hirsutum L.); unfertilized soybean [Glycine max (L.) Merr.]; and fallow. These treatments were followed by sugarcane grown for 3 yr at four different levels of N fertilizer application. Previous‐crop treatments containing corn and sorghum contributed more biomass back to the soil than cotton or soybean. None of the crops grown prior to sugarcane responded to N fertilization, resulting in 90% of the N fertilizer applied remaining in the soil. Sugarcane yield and quality in the plant‐cane crop were affected primarily by previous‐crop treatments, in the first ratoon by both previous crop and N fertilizer application, and in the second ratoon primarily by N fertilizer application. Sugarcane responses to N fertilization were generally lowest following those treatments which had the most N returned from plant residue, or the most measured residual N. Inorganic soil N measurements correlated better with sugarcane responses to N in the plant cane crop, while mineralizable soil N levels correlated better with sugarcane responses to N in the first ratoon crop. Soybean resulted in low inorganic and mineralizable soil N, yet sugarcane following soybean failed to respond to N fertilizer application, indicating that N following soybean is less readily released but does later become available.
Cyanogenesis Effect on Insect Damage to Seedling White Clover in a Bermudagrass Sod
Authors: Pederson Gary A. , Brink Geoffrey E.
Published: July 2010

Cyanogenesis in white clover (Trifolium repens L.) has been shown to confer resistance to a number of leaf‐feeding insects and molluscs in laboratory and field studies. Most cultivars grown in the USA, however, are acyanogenic. White clover seedlings may be damaged or killed by insect feeding during establishment into a grass sod. The objective of this study was to determine if white clover stand establishment in a grass sod is influenced by cyanogenesis. Two cyanogenic white clover populations, HCNpi and BLHplus, and two acyanogenic populations, ‘Regal’ and BLHminus, were sod‐seeded into common bermudagrass [Cynodon dactylon (L.) Pers.] at two locations in 1994 and one location in 1995. The 1994 test in Forage Unit A was planted on an Oktibbeha silty clay (very‐fine, smectitic, thermic Chromic Dystrudert). The 1994 and 1995 tests in Forage Unit B were planted on a Savannah fine sandy loam (fine‐loamy, siliceous, semiactive, thermic Typic Fragiudult). The studies were conducted in a randomized complete block design with four replicates at Mississippi State, MS. Cotyledons, unifoliate leaves, and trifoliate leaves were rated for insect damage and leaf area loss due to insect feeding at 2, 4, and 6 wk after seeding. No differences were noted among the populations for seedling survival at 2 wk after seeding. At 4 and 6 wk after seeding, the highly cyanogenic population, HCNpi, had fewer plants with trifoliate leaves damaged and lost less leaf area due to insect feeding than either acyanogenic population. Seedling survival at 6 wk was 88% for HCNpi, compared with 66% for acyanogenic Regal. Cyanogenesis in white clover reduced insect feeding damage and improved seedling survival in bermudagrass sod. The incorporation of limited levels of cyanogenesis into acyanogenic U.S. cultivars could improve seedling establishment without the animal toxicity concerns of highly cyanogenic types.
Is Soil Temperature Better than Air Temperature for Predicting Winter Wheat Phenology?
Authors: McMaster Gregory S. , Wilhelm Wallace W.
Published: July 2010

In predicting wheat (Triticum aestivum L.) phenology, logic suggests that basing thermal unit accumulation on near‐surface soil temperature should give a better representation of shoot apex thermal unit accumulation than air temperature until internode elongation raises the apex above the soil surface. A study was undertaken to determine if predictions of winter wheat phenology are improved when based on measured near‐surface soil temperature rather than air temperature. Air temperature 1.5 m above the soil surface and soil temperature at crown depth (the position of the shoot apex before stem elongation) were collected for 23 site‐years across the U.S. Central Great Plains representing a range of cultivars, soils, management practices, and climates. Seven site‐years from different sites were randomly selected to calculate the mean thermal units from both seeding and 1 January to specific growth stages based on both air and soil temperature. These means were used to predict occurrence of growth stages for the remaining 16 site‐years. In no instance did soil temperature significantly improve prediction of winter wheat phenology. From these results, we conclude that the additional effort and expense of using soil temperature in predicting winter wheat phenology are not justified.