bluuebunny/crossref_metadata_2025 huggingface dataset:
Measuring Plant and Soil Water Potentials with Thermocouple Psychrometers: Some Concerns
Authors: Brown R.W. , Oosterhuis D.M.
Published: July 2010

Thermocouple psychrometers are commonly used to measure soil and plant water status. Users often assume that these instruments can be used routinely with little regard for understanding how they operate, or for the precautions required for accurate measurements of water potential. Poor procedures and inadequate attention to both practical and theoretical requirements can jeopardize the successful performance of these highly sensitive instruments. For example, in addition to understanding the theory of operation of thermocouple psychrometers, calibration and proper cleaning of these instruments are among the most important steps in successfully using them. Important sampling precautions include consistency of technique, prevention of evaporative loss during collection and sealing, and careful sample selection. Major concerns during measurements of water potential include achieving complete vapor pressure equilibrium, interpreting data, and detecting and preventing temperature gradients. Although many precautions for in situ measurements are similar to those for measuring soil and plant samples, each use has specific requirements. Thermocouple psychrometers are useful for accurate and reliable measurements of water potential if proper techniques and precautions are used.
Portable and Desktop Computer Integrated Field Book and Data Collection System for Agronomists
Authors: Berke T.G. , Baenziger P.S.
Published: July 2010

An integrated, computerized system has been developed to facilitate data collection and storage. It utilizes hardware, commercial software, and menu‐driven software and has two parts. The first part utilizes a portable microcomputer to collect data in the field or lab. This microcomputer can be interfaced with an electronic balance to facilitate data entry by weighing. Off‐line data storage is available when remote field situations prevent immediate data transfer. The second part utilizes a desktop microcomputer with a hard disk to generate randomized complete block design treatment arrangements with one to six replications, create and manipulate data storage files, print fieldbooks, and print adhesive labels. Data files from the portable microcomputer can be imported into a spreadsheet for simple statistical analyses (means, variances, ranks, etc.) or transferred as an ASCII file to a more sophisticated statistical analysis program. This system allows control of data collected from an experiment on one integrated computer system. Transcription errors are avoided and data are immediately available for analysis. The software developed for the system is available upon request.
Mycorrhizae: Possible Explanation for Yield Decline with Continuous Corn and Soybean
Authors: Johnson Nancy Collins , Copeland Philip J. , Crookston R. Kent , Pfleger F. L.
Published: July 2010

Earlier studies showed that mycorrhizal fungi selectively proliferate in soils cropped in monoculture to corn (Zea mays L.) or soybean [Glycine max (L.) Merr.]. This study evaluated whether the dominant mycorrhizal fungi, based on spore numbers present in soil, affected growth and nutrient uptake of the following crop. Plots at two locations in Minnesota with a continuous corn or continuous soybean history were planted to both corn and soybean. The relationship between spore numbers of proliferating species of mycorrhizal fungi and crop yield and nutrient concentrations were assessed using simple correlation analysis. Spore populations of mycorrhizal fungi which proliferated in corn were generally negatively correlated with the yield and tissue mineral concentrations of corn, but were positively correlated with the yield and tissue mineral concentrations of soybean. Spore populations of soybean proliferators exhibited the reciprocal relationship, although less clearly. We suggest that, compared to other fungi, proliferating VAM fungal species may be less beneficial (or perhaps detrimental) to the crop in which they proliferate. We propose a mechanism to explain how vesicular‐arbuscular mycorrhizal (VAM) fungi could cause yield depressions associated with monoculture, and outline research needed to test this hypothesis.
Yield Response of Canola to Nitrogen, Phosphorus, Precipitation, and Temperature
Authors: Nuttall W.F. , Moulin A.P. , Townley‐Smith L.J.
Published: July 2010

Canola (Brassica nupus L.) is a major crop in western Canada, and been used extensively as an alternative crop to wheat (Triticum aestivum L.). Yet, little information is available on the response of this crop to N and P fertilizers in relation to soil tests for these elements under varying environmental conditions. Accordingly, this study was conducted for a 16‐yr period to determine the yield response of canola to N and P fertilizers in relation to soil tests for these elements in northeastern Saskatchewan on black Melfort silty clay (Typic Cryoboroll) previously cropped to spring wheat. Nitrogen fertilizer was applied at 45 and 134 kg N ha−1 in factorial combination with 0, 10, 20, 30, and 40 kg P ha−1. Extra treatments consisted of 10N–20P kg ha−1 and a control with no fertilizer applied. Canola grain and straw response to N and P fertilizer was significant, but the N by P interaction was not significant. The interaction effects of Year by P and Year by N were significant, indicating a wide range of response to applied elements among years because of temperature, precipitation and soil nutrient effects. Grain yield was positively correlated to total precipitation and negatively correlated to mean maximum daily temperature for the months of July and August (R2 = 0.32). The highest grain yield (2.46 t ha−1) was obtained in 1987 with P fertilizer applied at 40 kg P ha−1 (averaged across N rates), 162 mm of rainfall and an average maximum temperature of 21.2 °C. The lowest yield (0.37 t ha−1) was obtained in 1989 with P fertilizer applied at 20 kg P ha−1, 95 mm of rainfall and an average maximum temperature of 25.1 °C. In conclusion, soil tests for N and P accounted for much of the variation in yield response to these elements (r2 = 0.58 and R2 = 0.46, respectively) despite large yield differences among years because of temperature and precipitation.
Conserving Residual Corn Fertilizer Nitrogen with Winter Cover Crops
Authors: Shipley P. R. , Messinger J. J. , Decker A. M.
Published: July 2010

Autumn residual fertilizer nitrogen (FN) can be easily leached into groundwater in humid climates. Winter cover crops were evaluated for their ability to assimilate residual corn FN and thereby reduce N losses. Labelled FN (15N depleted) was applied to corn in Maryland in 1986 and 1987 at rates of 0, 168, and 336 kg FN ha− on a Mattapex silt loam (fine‐loamy, mixed, typic Hapludult). Cover crop treatments following corn harvest were hairy vetch (Vicia villosa Roth), crimson clover (Trifolium incarnatum L.), cereal rye (Secale cereale L.), or annual ryegrass (Lolium multiflorum Lam.), and a weed/fallow control of chickweed (Stellaria media L.). The covers were harvested three times the following spring and dry matter yields (DM), %N, and atom % 15N were determined to assess FN uptake. Fall labelled N in the soil (to 80 cm) averaged 17 and 114 kg FN ha−1 over both years for the 168 and 336 kg FN ha−1 rates, respectively. However, the quantity of total residual mineral N (soil N plus FN) after the 168 kg ha−1 rate was 87 kg N ha−1, which was comparable to the quantity of labelled N at the high fertilizer rate. The average cover crop FN uptake (kg FN ha−1) in mid‐April after the 336 kg N ha−1 treatment was 48 for cereal rye, 29 for annual ryegrass, 9 for hairy vetch, 8 for crimson clover, and 6 kg FN ha−1 for the native weed cover (LSD P = 0.05 of 7 kg FN ha−1). Corresponding percent recoveries of the fall N in the aboveground DM were 45% for cereal rye, 27% for annual ryegrass, 9 for hairy vetch, 8% for crimson clover, and 8% for native weed cover. These results show that grass cover crops conserved the most FN. Cereal rye recovered more FN through mid‐April because of its growth in cool weather, although annual ryegrass was equally effective if grown to mid‐May. Renewed efforts should be made to utilize grass cover crops to conserve N in humid climates.
Corn Grain Yield and Nitrogen Utilization in Relation to Subsoiling and Nitrogen Rate on Paleudults
Authors: Wagger M. G. , Vepraskas M. J. , Vepraskas M. J. , Denton H. P.
Published: July 2010

Subsoiling is used to loosen root‐restricting layers and increase rooting depth and water availability; however, little information is available regarding how to adjust the recommended fertilizer N rate. This study evaluated corn (Zea mays L.) grain yield response to subsoiling and N rate in 12 Typic and Arenic Paleudults from 1985 through 1987. Corn earleaf and grain N concentrations were also measured. Chisel plowing and subsoiling were factorially combined with either 0, 80, 120, 160, and 200 kg N ha−1 or 80, 120, and 160 kg N ha−1. The relative yield increase (RYI) due to subsoiling ranged from –2 to 145% during the 3‐yr period due to variations in soil physical properties and rainfall distribution during the growing seasons. Regression equations for corn yield response to fertilizer N, based on pooled data sets with a RYI < or > 15% each year, were characterized as having the same slope but only different intercepts for each site and/or tillage system. Earleaf and grain N concentrations tended to be lower with subsoiling while grain N uptake was higher at five sites with relatively high RYIs. Apparent recovery of fertilizer N was similar between tillage systems, averaging 36% for subsoiled and 33% for nonsubsoiled treatments. Results from this study indicated that to obtain optimum corn yields the recommended N rate should be the same for chisel plowed and subsoiled tillage systems for soils with root‐restrictive E horizons.
Annual Phytomass Production of a Rye‐Corn Double‐Cropping System in Ontario
Authors: Tollenaar M. , Mihajlovic M. , Vyn T. J.
Published: July 2010

A rye (Secale cereale L.)‐corn (Zea mays L.) double‐cropping system has the potential to maximize annual phytomass production in Ontario. Field experiments were conducted at Elora and Woodstock, ON, from 1981 to 1984 to evaluate the impact of rye harvest and corn planting date combinations during the spring as well as tillage methods on annual above‐ground phytomass production. Winter rye was planted in late September or early October after corn harvest and either chemically killed in early May or harvested as silage before corn planting. The rye/tillage treatments consisted of no‐rye/rototill, rye/rototill, and rye/no‐till. Corn phenology was monitored during the growing season and corn above‐ground dry matter was harvested in late September. Rye phytomass was 2.7 and 4.5 Mg ha−1 at the middle of May in Elora and Woodstock, respectively, and 5.4 Mg ha−1 at the end of May in Elora. Rate of leaf appearance and plant height during early development was reduced, silking date was delayed, and plant moisture at corn harvest was higher for corn following rye in comparison to single‐crop corn. The impact was largest in the no‐till treatments. The combination of rye harvest date/corn planting date and tillage treatment that resulted in the highest phytomass production in the rye‐corn double‐cropping sequence was 6 to 10% higher than that of early planted corn. The reduction in corn dry matter accumulation due to the preceding rye crop and the delay in date of corn planting negated to a large extent the contribution of rye phytomass to the total phytomass production of the rye‐corn double‐cropping sequence.
Growth of Relay Intercropped Soybean
Authors: Wallace S. U. , Whitwell T. , Palmer J. H. , Hood C. E. , Hull S. A.
Published: July 2010

Relay intercropping of wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merr.] allows for earlier soybean planting than in conventional doublecropping systems, but shading and other influences of the wheat crop may be detrimental to intercropped soybean development. The purpose of this study was to determine the effect of relay intercropping on soybean growth and yield. Intercropped soybean, planted 19 (1989) or 14 (1990) days before wheat harvest, was compared with a control treatment (same no‐till planting pattern and date, but no wheat) on a Cecil sandy loam (clayey, kaolinic, thermic Typic Hapludults) soil. Intercropping had a greater influence on soybean growth in 1989, when there was more shading by the wheat canopy and also when the period between soybean planting and wheat harvest was longer, than in 1990. In both years, the greatest effects of intercropping on growth occurred early in the season, when intercropped plants were taller but had smaller stem diameters, less leaf area, and less aboveground dry weight, as compared with control plants. Photosynthetic rates of upper canopy leaves were reduced by intercropping for 2 wk after wheat harvest in 1990. This was associated with an increase in specific leaf area in intercropped plants. Lateseason growth, including that of reproductive parts, was similar for intercropped and control treatments, and there were no detectable effects of intercropping on final yield components or yield in either year. In environments where the period of overlap between the wheat and soybean crops is relatively short, negative effects of relay intercropping on early soybean growth may not result in yield reductions.
Prediction of Sweet Corn Phenology in Subtropical Environments
Authors: Olsen J. K. , McMahon C. R. , Hammer G. L.
Published: July 2010

Limited information on phenology of sweet corn (Zea mays L.) grown in subtropical regions is available to processors wishing to manage harvest scheduling. This study was conducted to investigate developmental characteristics of both standard sugary (su) and mutant endosperm sugary enhancer (se), and shrunken‐2 (sh2) sweet corn in subtropical Australia. Field experiments were conducted at three locations with numerous times of planting so that a broad range of environments were encountered. Models of daily rate of development for the period sowing to kernel maturity (720 g kg−1 moisture) were derived by an iterative optimization procedure. Development rate was related to mean daily temperature and photoperoid. Temperature was the most important factor affecting rate of development. The temperature response was best described by a broken linear function. Various photoperiod functions fitted as multipliers to the temperature response did not improve goodness‐of‐fit. Cultivars were classified into three maturity groups based on analysis of covariance. Developmental characteristics appeared independent of genetic background as the response of the three sh2 cultivars was not significantly different from a tropical su type, and the se cultivar ‘Sweet Champion’ did not differ significantly from the majority of su types. Only su cultivar ‘Terrific’ differed significantly from both of these groups. Base temperatures (range from 5.4–6.4°C) were lower than the value traditionally quoted for sweet corn (10°C). Optimum rates of development occurred at temperatures ranging from 30.8 to 33.8° C. The models accurately predict the duration of sowing to maturity and were shown to be a practical tool for harvest date prediction of both standard and mutant endosperm sweet corn in subtropical environments.
Subsurface Compaction Effects on Tillering and Nitrogen Accumulation in Wheat
Authors: Oussible M. , Allmaras R. R. , Wynch R. D. , Crookston R. K.
Published: July 2010

Compaction in the 0.05‐ to 0.30‐m depth may limit tillering and N accumulation in wheat (Triticum aestivum L.); these effects may be yield reducing. Before imposing compaction treatments in a field study in Minnesota, perforated small‐diameter tubing was buried in a Waukegan silt loam (sandy skeletal, mixed, mesic Typic Hapludoll) at a depth of 0.2 m in all plots. Compacted plots each received four passes with a heavy vibrating roller, while control plots were disk plowed and then disk harrowed. All plots were then surface roto‐tilled and seeded to wheat. At early tillering a K15NO3 solution was applied to the subsurface via the tubing. Plants sampled for 15N/N recovery 24 h after 15N application, at anthesis, and at maturity showed no significantly different 15N or N concentration or accumulation per culm/ individual organ in response to compaction. Because subsurface compaction reduced tillering, N uptake in the grain and straw was reduced by 21 and 30%, respectively. After the 0.10‐m surface layer was removed from all plots in a field study on a clay loam soil (Typic Calcixerolls) in Morocco, the subsurface was compacted by four passes with a 7.5‐ton tractor. Soil was then replaced, leveled, and only the control plots were disk plowed and disk harrowed twice. Both compacted and control plots were roto‐tilled and seeded. Nitrogen concentration and accumulation per culm/individual organ immediately after tillering was reduced less than 5% by the compacted treatment in both 1982 and 1983. Reduced tillering in the compacted treatment reduced average N uptake 11 and 28% in the grain and straw, respectively. In all three tests N concentration in the shoot at the end of tillering was high; yet it was higher in the compacted treatment. Then N concentration and uptake was reduced by compaction on a per culm basis at maturity, and earlier in one of the field studies. Root length density was reduced in the compacted zone in response to greater penetrometer load and higher bulk density. Tiller bud development was suppressed by the compaction treatment as much as 20% even though concentrations of N were high in the shoot. Tiller losses and declines of N concentration in the shoot in the post tillering stages were nearly the same in both treatments. Additional N before tillering therefore cannot overcome the adverse influence of subsoil compaction.
Pearl Millet‐Soybean Rotation and Nitrogen Fertilizer Effects on Millet Productivity
Authors: Mohammed M. S. , Clegg M. D.
Published: July 2010

Pearl Millet [Pennisetum glaucum (L.) R. Br.] plays an important role as a staple food grain in many developing countries, but is relatively new to the Great Plains of the USA. This study was conducted for 2 yr to evaluate the effects of a preceding soybean [Glycine max(L.) Merr.] crop and/or applied N fertilizer on pearl millet yield and N uptake, and to quantify the amount of residual soil NO3‐N resulting from the cropping system. The experiment was conducted on a fine montmorillonitic, mesic, Typic Argiudoll soil at the University of Nebraska Research Center near Mead, NE. The experiment included three treatments consisting of 0, 45, and 90 kg N ha−1 applied to continuous pearl millet, and two treatments consisting of 0 and 45 kg N h−1 applied to pearl millet following soybean. Pearl millet grain yield was 5.69 (1986) and 4.22 (1987) Mg−1 with no applied N, 6.42 (1986) and 5.82 (1987) Mg−1 with 45 kg ha−1 applied N, and 7.13 (1986) and 6.85 (1987) Mg−1 with 90 kg ha−1 applied N. Grain yields increased 0.73 (1986) and 1.48 (1987) Mg −1 when grown after soybean, increase equivalent to that with 45 kg ha−1 of applied N. Percent N in various plant parts and N uptake increased with applied N or when pearl millet followed soybean. Differences in pearl millet plant weight, leaf weight, and LAI did not occur until 62 d after sowing in plots with applied N, but an increase in these parameters due to rotation occurred at 37 d. Residual NO3 in the soil profile was higher in the rotation treatment, than the applied N treatments, but there was a tendency for more residual NO3‐N to occur with increased applied N in the continuous pearl millet. Pearl millet can be successfully used in cropping systems with soybean with no additional N, but addition of N may be necessary with continuous cropping.
Cultivar and Climatic Effects on the Protein Content of Soft White Winter Wheat
Authors: Rao A. C. S. , Smith J. L. , Jandhyala V. K. , Papendick R. I. , Parr J. F.
Published: July 2010

High‐protein wheats (Triticum aestivum L.) are not preferred for Oriental diets. Because the protein content of soft white winter wheat grown extensively in the U.S. Pacific Northwest is often higher than the optimum (100 g kg−1) for export, there has been a decline of wheat exports to Japan and other Pacific Rim countries. The present study was undertaken to examine the trends in protein levels during 1979 to 1988 and to evaluate the influence of wheat cultivars and climatic parameters on protein content of SWW wheat in the Pacific Northwest. The maximum and minimum temperatures, precipitation, and evaporation during each of 9 wk prior to crop harvest were tested for their effect on protein content. Data on protein content used in the analysis were obtained from the annual reports of USDA Western Wheat Quality Laboratory for wheat grown at 10 different locations in Washington, Idaho, and Oregon. Five‐year moving averages indicated a rising trend in the protein content at Lind, WA, and Moro, OR, the two driest locations. Commercially grown cultivars had no significant influence on protein content in the presence of climatic parameters. Climatic parameters were found to have a significant influence on wheat protein content with coefficients of multiple determination ranging from 0.36 to 0.82 for the 10 locations. Maximum temperature during the grain‐filling stage influenced the protein content at 9 out of 10 locations, and, generally, a rise in temperature resulted in higher protein contents. With climatic factors significantly influencing protein levels in SWW wheat, suitable agronomic and fertility management practices are needed to ameliorate the climatic effects.
Leaf and Stem Traits and Herbage Quality of Multifoliolate Alfalfa
Authors: Juan Nestor A. , Sheaffer Craig C. , Barnes Donald K. , Swanson Douglas R. , Halgerson James H.
Published: July 2010

Multifoliolate (MF) alfalfa (Medicago sativa L.) cultivars, with four or more leaflets per leaf instead of three, have been marketed for greater nutritive value and intake potential than standard trifoliolate (TF) alfalfa cultivars. A field study to determine the effect of harvest regimes on MF expression of alfalfa cultivars and germplasm, and to determine the association of MF expression with herbage yield, herbage quality, and leaf and stem traits, was conducted on a Tallula silt loam (coarse‐silty, mixed, mesic Typic Hapludoll). Four MF and two TF alfalfa genotypes were subjected to bud and first‐flower cutting regimes. Multifoliate expression on a leaf number basis (MF leaf number/total leaf number) ranged from 5 to 70%. Relative MF entry ranking was consistent across years and harvest regimes. Expression of the MF trait was not correlated with herbage yield. For all seasonal harvests and harvest regimes, MF expression was correlated with leaf concentration (r = 0.48) and number of leaflets per leaf (r = 0.84), but was not consistently associated with node number or plant height. Expression was not correlated with total herbage crude protein concentration, and at best explained 25% of the variation in acid detergent and neutral detergent fiber concentration. A TF genotype developed for superior herbage quality had leaf concentration, forage quality, and intake potential similar to MF genotypes with high MF expression levels. Multifoliolate alfalfa genotypes have the potential to produce higher quality herbage than some TF types; however, this can be achieved only with high MF expression levels.
Calibration of Granular Matrix Sensors for Irrigation Management
Authors: Eldredge Eric P. , Shock Clinton C. , Stieber Timothy D.
Published: July 2010

Granular matrix sensors (GMS) represent an alternative technology for measuring soil water to schedule irrigation. When GMS were tested by drying them to measure changes in electrical resistance with decreasing water content, their resistance response to drying in air in an oven was similar (t = −0.87, 134 df) to that for drying in a field soil, with a response curve that suggested GMS could be used to measure soil water potential (Ψ). Granular matrix sensor meter readings were compared with tensiometer, neutron probe, and gravimetric measurements of soil water in the root zone of potato (Solanum tuberosum L. cv. Russet Burbank) grown in silt loam. Measurements with GMS were closely related to soil water potential measurements and to soil water measured gravimetrically or by neutron probe. Meter model 30KTC, as supplied by the manufacturer, when calibrated against tensiometers, had a linear response represented by the equation y = −6.44 − 0.738 x, where y = Ψ J kg−1), and x = 30KTC meter reading (dimensionless units) of GMS, with r2 = 0.89. Granular matrix sensors were used to monitor transitory soil water stress treatments in an experiment to determine potato response to water stress.
Legume Cover Crop Contributions to No‐Tillage Corn Production
Authors: Decker A. Morris , Clark Andrew J. , Meisinger John J. , Mulford F. Ronald , McIntosh Marla S.
Published: July 2010

Winter cover crops can supply N to the next crop, reduce erosion and N leaching, and conserve or deplete soil moisture. To identify optimum corn fertilizer nitrogen (FN) rates following cover crops, we evaluated hairy vetch (VT: Vicia villosa Roth), Austrian winter pea [PE: Pisum sativum L. subsp. sativum var. arvense (L.) Poir.], crimson clover (CR: Trifolium incarnatum L.), and wheat (WH: Triticum aestivum L.) winter cover crops in the U.S. Coastal Plain and Piedmont for no‐tillage corn (Zea mays L.) at four FN rates (topdressed NH4NO3) over 4 yr. Parameters evaluated included cover crop yield and N content, corn N uptake, and corn grain yield. On the Coastal Plain, VT, PE, CR, and WH topgrowth averaged 205, 180, 170, and 40 kg N ha−1, respectively, and ≈40% less for the Piedmont. With no FN, grain yields were generally greater after legumes than after no cover crop, and lowest after WH, with the best yields after legumes with 90 to 135 kg FN ha−1. Synergistic responses occurred when FN was applied after legumes. Non‐N‐limited grain yield increases averaged 2 Mg ha−1 (Coastal Plain) and 0.5 Mg ha−1 (Piedmont), and were not directly related to cover crop N. With no cover crop, FN needed for maximum yield averaged 80 kg ha−1 (Piedmont) and 135 kg ha−1 (Coastal Plain). After WH, FN needs increased 15 to 30 kg ha−1, but decreased 10 to 75 kg ha−1 after legumes. Hairy vetch provided the most consistent increases, with average grain yield of 10.6 Mg ha−1 (Coastal Plain) and 8.2 Mg ha−1 (Piedmont), and an economic optimum FN rate of 127 (Coastal Plain) and 66 kg ha−1 (Piedmont).
Radiation Balance of a Soil‐Straw Surface Modified by Straw Color
Authors: Sharratt Brenton S. , Campbell Gaylon S.
Published: July 2010

Straw color may alter the net radiative flux at the soil‐straw surface and, consequently, the availability of energy for soil, biological, and atmospheric processes. This study ascertained the radiation balance of a soil‐straw surface as modified by the color of the straw on the surface. Barley (Hordeum vulgare L.) stubble and loose straw on 36‐m2 plots near Fairbanks, AK, was painted black, white, or remained unpainted (natural) in a randomized block experimental design. Reflected global radiation was measured in the spring of 1988–1990 and net radiation was monitored in the spring of 1990. Midday reflected global radiation and soil‐straw surface temperatures were measured on clear days in 1989. The albedo of the black straw treatment was 0.05, of the natural straw treatment was 0.2, and of the white straw treatment was 0.3. The black straw treatment resulted in higher midday surface temperatures and consequently higher emission of longwave radiation compared with other straw color treatments. A soilstraw‐atmosphere system model provided good estimates of the measured net radiative flux in 1990 (R2 = 0.91). The model predicted that a soil‐black straw surface would absorb 10% more radiation than a soil‐natural straw surface and 15% more radiation than a soil‐white straw surface averaged over the three years. The results suggest that straw color management can be an option for altering the surface radiation balance in regions with extreme climates.
Forage Quality and Harvest Index of Corn Hybrids under Different Growing Conditions
Authors: Cox W. J. , Cherney J. H. , Pardee W. D. , Cherney D. J. R.
Published: July 2010

Recent studies suggest that grain content may not necessarily predict corn (Zea mays L.) forage quality. Field studies were conducted at two New York locations in 1991 and 1992 to evaluate forage quality differences among commercial corn hybrids across different growing conditions and the relationship between the harvest index (HI) value and forage quality. Twelve hybrids, which ranged in relative maturity from 95 to 116 d, were evaluated in two experiments according to maturity differences. Each hybrid was hand‐harvested at the 1/2‐milk‐line stage or 350 g kg−1 dry matter (DM) concentration to determine DM yield, HI, whole‐plant N, neutral‐detergent fiber (NDF), acid‐detergent fiber (ADF), lignin, and in vitro true digestibility (IVTD). Although the relationship among hybrids for NDF was consistent across three of four site‐year comparisons, year × hybrid and location × hybrid interactions existed in one experiment because some hybrids received a killing frost at one location before attaining the 1/2‐milk‐line stage. In contrast, hybrid interactions for IVTD did not exist, which suggests a consistent relationship among hybrids for digestibility, even if hybrids received a killing frost between the dent and 1/2‐milk‐line stage. The HI correlated closely with NDF (−084 and ‐0.82) and IVTD (0.79 and 0.63) in both experiments. Likewise, lignin correlated closely with NDF (0.84 and 0.88) and IVTD (−0.76 and −0.79). The data suggest that livestock producers can continue to choose hybrids with high grain content if relatively low fiber and high digestibility are of prime interest.
WeatherMan: A Utility for Managing and Generating Daily Weather Data
Authors: Pickering N. B. , Hansen J. W. , Jones J. W. , Wells C. M. , Chan V. K. , Godwin D. C.
Published: July 2010

Daily weather data commonly used in simulation models of agricultural or ecological systems are sometimes incomplete, frequently contain errors, and are often in an inconvenient format. The WeatherMan is a user‐oriented software package designed to assist in preparing daily weather data for use with simulation models. The software can import or export daily weather files with any column format (including the Decision Support System for Agrotechnology Transfer ver. 2.1 and ver. 3.0 files) and convert the data to desirable units. Data are checked and flagged for possible errors on import. Several techniques are available for filling in missing values and erroneous data on export. WeatherMan also contains two methods (WGEN and SIMMETEO) for stochastically generating sequences of daily weather data. Both methods can be parameterized from the daily data and the second method uses monthly means from any secondary data source. Summary statistics of raw and generated data can be graphed or presented in tables.
Arbuscular Mycorrhizal Fungus Spore Populations Respond to Conversions between Low‐Input and Conventional Management Practices in a Corn‐Soybean Rotation
Authors: Kurle J. E. , Pfleger F. L.
Published: July 2010

Arbuscular mycorrhizal fungi (AMF), ubiquitous symbiotic fungi colonizing plant roots, can contribute to plant growth by improving nutrient uptake and stress tolerance. The influence of management practices and crop species on AMF spore populations and percent root colonization was examined during conversion from conventional to low‐input and low‐input to conventional management systems in 2‐yr crop rotations planted to alternating corn (Zea mays L.)‐soybean [Glycine max (L.) Merr.] sequences established in two adjacent areas with different management histories. During the previous 25 yr, the low‐input area had received no fertilizer or herbicide inputs, while the conventionally managed area had received recommended fertilizer and herbicide inputs. No input (NI), organic input (OI), minimum input (MI), and conventional input (CI) management systems were established within each crop sequence. Weeds were the dominant vegetation in both years in the low‐input area. Average AMF spore population in this area was 292 spores g−1 soil. In the conventionally managed area, only crop plants were present during the first year, while small weed populations had developed by the end of the second year in NI and OI. Average AMF spore population in the conventionally managed area was 175 spores g−1 soil. Average AMF colonization percentage in the low‐input area was 27.5%, while in the conventionally managed area it was 24.5%. AMF colonization percentages were not correlated with AMF spore populations and did not appear to be influenced by the management systems established within each area. Management systems appeared to influence AMF spore populations by their effect on weed populations.
Surface Residue and In‐Row Treatment Effects on Long‐Term No‐Tillage Continuous Corn
Authors: Swan James B. , Higgs Roger L. , Bailey Theodore B. , Wollenhaupt Nyle C. , Paulson William H. , Peterson Arthur E.
Published: July 2010

Many farmers in the northern Corn Belt are reluctant to adopt notillage practices with continuous corn (Zea mays L.) because they fear that phenological development, stand establishment, and grain yield will be reduced compared with moldboard or chisel plowing. Mechanical removal of in‐row residue at planting may reduce or eliminate these problems. The objectives of this research were to determine the effects of surface crop residue and planter attachments on in‐row cover, seed placement, plant density, grain yield, and grain moisture content of notillage corn, and to determine if these effects changed with time. Three postharvest residue levels, residue removed, normal, and double, were compared from 1984 through 1990 on Rozetta and Palsgrove silt loam soils in southwestern Wisconsin. Average grain yields over the 7‐yr period ranged from 3.7 to 10.8 Mg ha−1. Seasonal effects, presumably due to weather conditions, accounted for >90% of the variability in grain yield. For the period 1984 to 1990, yield differences due to crop residue levels and in‐row residue removal techniques could not be declared statistically significant at the 5% level, given the limited size of the study. However, average yields with normal residue were 0.44 Mg ha−1 greater than where residues were removed. Because such a difference can be agronomically important, additional research seems warranted. In‐row residue affected planting depth and stand density emphasizing that uniform seeding depth is particularly important for successful no‐till corn production.
Source‐to‐Sink Manipulation Effects on Cotton Lint Yield and Yield Components
Authors: Pettigrew William T.
Published: July 2010

Cotton (Gossypium hirsutum L.) yields can vary considerably among years and locations, even under levels of water and nutrients considered adequate. Since photosynthesis is one of the principal components in determining reproductive yield, the objectives of this study were to determine how manipulations of the ratio of photosynthetic source to reproductive sink affect cotton lint yield and yield components (boll mass, seed mass, seed per boll, lint percentage, and bolls per square meter). Field studies were conducted in 1991 and 1992 on a Bosket fine sandy loam with six source‐to‐sink ratio manipulations (partial fruit pruned, partial leaf pruned, reflectors, open canopy, shaded plots, and an untreated control) imposed on three cotton genotypes: ‘DES 119’, ‘DPL 5690’, and ‘Prema’. White blooms were tagged twice in both years, and fruit were subsequently harvested after bolls had opened. These bolls were ginned and boll mass, lint percentage, and seed mass were determined. Overall lint yield and yield components were determined for the reflector, open canopy, shaded plot, and control treatments. The partial fruit pruned treatment had a 16% greater boll mass and a 10% greater seed mass than the control. Percentage lint was not affected by any of the treatments. In 1992, bolls at the first sympodial position (fruit at all other positions were pruned from the sympodial branches) had a 25% greater boll mass and 8% greater seed mass than bolls at the second sympodial position (fruit at all other positions were pruned from the sympodial branches) and control treatment bolls from the first tagging. Position 1 and Position 2 bolls did not differ in boll or seed mass during the second tagging period (both greater than the control) or in percent fruit abortion during either tagging period (both lower than the control). Lint yields from the open canopy and reflector treatments were 17% and 6% greater than the control, respectively, and the shaded plot yielded 20% less than the control. Boll number was the component of yield that accounted for these differences. Cotton canopies bred for increased light penetration to lower leaves or for better utilization of the intercepted light may lead to lint yield increases.
Straw Quality of 10 Wheat Cultivars under Conventional and No‐Till Systems
Authors: Rao Srinivas C. , Dao Thanh H.
Published: July 2010

Straw of small‐grain cereal is an important source of feed for maintenance of ruminant livestock. Information on the nutritional quality of wheat (Triticum aestivum L.) straw under conservation tillage system is limited. Grain and straw (leaves and stem) samples were obtained from a previous tillage by cultivar field study conducted on a Bethany silt loam (fine, mixed, thermic Pachic Paleustoll) from 1984 to 1987 near El Reno, OK, to determine the straw quality of 10 hard red winter wheat cultivars grown under conventional (moldboard plow) and no‐till systems. Straw was analyzed for neutral‐detergent fiber (NDF), aciddetergent fiber (ADF), lignin (LIG), crude protein (CP), and in vitro dry matter digestibility (IVDMD). Fiber (ADF and NDF) and LIG concentrations of straw from the early‐maturity cultivars were higher (P ≤ 0.05) than medium and late maturity cultivars. Crude protein (5 to 12 g kg−1) and IVDMD(25 to 39 g kg−1) concentrations were lower in early‐maturing than in medium‐ and late‐maturing cultivars among years. Neutral‐detergent fiber and ADF concentrations of all cultivars were not affected by tillage system; however, LIG of early‐maturing cultivars (Chisholm and Vona) grown under a no‐till system was 9 to 24 g kg−1 lower in 1985 and 1986 than in conventionally tilled plots. In vitro dry matter digestibility of all cultivars was not consistently affected by tillage system: no significant difference in 1984, while straw IVDMD from no‐till plots of all cultivars averaged 9 g kg−1 lower in 1985 and 13 g kg−1 lower in 1986, compared with conventionally tilled plots. Straw quality of the 10 wheat cultivars varied among maturity groups, but the effect of tillage system on straw quality was minimal.
Soil and Plant Water Evaporation from Strip‐Tilled Cotton: Measurement and Simulation
Authors: Lascano Robert J. , Baumhardt R. Louis , Hicks Stanley K. , Heilman James L.
Published: July 2010

It is estimated that 20% of cotton producers in the Texas High Plains use the strip tillage practice of planting cotton (Gossypium hirsutum L.) in residues of chemically terminated winter wheat (Triticum aestivum L.). The effect of the residue on water use partitioning between soil (Es) and crop (Ec) evaporation has not been reported. This study tested the hypothesis that the cumulative evapotranspiration (Et), of crop ina strip tillage system and in conventional tillage are similar, and that the residue modifies the components of total Et by reducing Es and increasing Ec. Winter wheat was planted in the fall of 1990 and was chemically terminated in the spring of 1991 in an Olton soil (fine, mixed, thermic Aridic Paleustoll) at Lubbock, TX. The plot was divided into a wheat‐stubble and a conventional treatment. Residue on half of the plot was left as stubble and residue on the other half was shredded and incorporated. Both plots were planted with cotton on 20 May 1991. Measurements included soil water and temperature profiles, soil evaporation, weather, and crop phenology and lint yield. Input values obtained from these data were used in the energy and water balance model (ENWATBAL) to calculate the daily and seasonal water lost to Es and Ec for 100 d. Calculated daily Es varied <1 SD from measured values. Measured mean total Et were similar, i.e., 305 ± 20 mm for conventional and 304 ± 41 mm for cotton in the wheat stubble. Simulated Et was within 10% of the measured value. The ratio of total Ec to Et was 0.50 in the conventional and 0.69 in the wheat stubble cotton. The more efficient use of Et in the wheat stubble increased lint yield by 35%. The Ec water use efficiency was not modified by the wheat stubble and was 3.8 g lint kg−1 of transpired water. The modified version of ENWATBAL was adequate to calculate the daily and seasonal water use of a cotton crop in a terminated wheat stubble, and the results support our hypothesis. The Et water use efficiency was increased by the wheat residue without additional input of water.
Effect of Nitrogen Supply on Maize Yield: I. Modeling Physiological Responses
Authors: Sinclair Thomas R. , Muchow Russell C.
Published: July 2010

Much of the increase in maize (Zea mays L.) yields in recent decades has been closely associated with increased levels of N fertilizer application. Although many studies have documented yield responses to increased N levels in the soil, a mechanistic description of the physiological responses that influence crop growth under various levels of N has not been fully elucidated. The objective of this work was to develop a relatively simple, mechanistic model of maize growth and development to account for the influence of soil and crop N budgets. The soil N budget was simulated for two soil layers that incorporated fertilization, mineralization, denitrification, and leaching. Crop uptake rate of N was simulated by a supply function that depends on cumulative and daily thermal units, soil water content, and soil N availability. Comparison of simulated and experimental crop N uptake through the season showed especially good agreement for 0 to 12 g N m−2 fertilizer treatments. At 24 and 42 g N m−2, the simulated crop N uptake was greater than observed. Nevertheless, comparable seasonal patterns between simulations and observations at all fertility levels were obtained for accumulated total biomass and grain. Final grain yields for all fertility treatments were simulated to be within 8% of the observed. A sensitivity test was performed with the model to investigate the importance of various physiological parameters on biomass accumulation and yield. Yield estimates under low soil N levels tended to be most sensitive to minimum grain N concentration.
Crop and Soil Response to Long‐Term Tillage Practices in the Northern Great Plains
Authors: Aase J. Kristian , Pikul Joseph L.
Published: July 2010

Summer fallow is the most common cultural practice in the northern Great Plains. With proper cultural management, however, annual cropping may be feasible and economical. Our objective was to determine crop and soil response to nontraditional annual cropping practices (till and no‐till) in lieu of conventional fallow‐crop rotation for the production of spring wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) in the in the northern Great Plains. The study, initiated in 1983, was on a Dooley sandy loam (fine‐loamy, mixed Typic Argiboroll) 11 km north of Culbertson, MT. Tillage practices on annually cropped treatments included sweep tillage in autumn and disk tillage in spring; sweep tillage in spring; and no‐tillage. Conventional fallow‐spring wheat rotations were included as the control. With three exceptions, there were no statistical differences among treatments in soil P, soil nitrate N, and pH. Phosphorus and N were nonlimiting in all years; pH decreased about 0.06 units per year in the 0‐ to 8‐cm layer because of N fertilization. Bulk density differences in the 0‐ to 10‐cm layer appeared after 7 yr, with the lowest bulk density for the no‐tillage annual crop treatment. Grain and straw yields with the no‐tillage treatment were both 80% of yields with the fallow‐crop treatment. Total water use efficiency, based on soil water differences between harvest of one crop and harvest of the next, was significantly greater with no‐tillage than with the fallow‐crop treatment. Soil organic C decreased nearly 0.4 g kg−1 per year with the fallow‐crop treatment; there was a negligible decline with the notillage annual crop treatment. No‐tillage annual spring wheat crop production was the most efficient crop and soil management practice from the standpoint of yield, water use efficiency, soil organic C, and bulk density.
Sap Flow in a Dicotyledon (Sunflower) and a Monocotyledon (Sorghum) by the Heat‐Balance Method
Authors: Zhang Jingxian , Kirkham M. B.
Published: July 2010

The heat‐balance method is widely used to monitor sap flow in stems of herbaceous plants. Measurements of sap flow made on monocotyledons, with scattered vascular bundles in their stems, may not be as accurate as measurements on dicotyledons, with annular vascular systems located next to the heater of the gauge. Therefore, we measured the accuracy of sap flow measurements made by the heat‐balance method for sunflower (Helianthus annuus L. ‘Hysun 354’), a dicotyledon with C3 photosynthesis, and sorghum [Sorghum bicolor (L.) Moench, Funk's hybrid G‐522DR], a monocotyledon with C4 photosynthesis. Plants were grown in pots with a commercial potting medium under greenhouse conditions. Measurements were made during a cycle when the plants were well watered, drought stressed, or rewatered. A potted plant was placed on a scale and sap flow (SF) values (units of g h−1) were compared with weight lost during the same period of time (WL, g h−1). Accuracy of the sap flow measurements was determined by calculating error, defined as (SF – WL)/WL. The gauge had good accuracy (error = 8.8%) only with watered sunflower, which had high flow rates (maximum rate = 64.7 g h−1). (This sap flow rate, nevertheless, is less than those for woody plants under field conditions, which are often >100 g h−1.) Sap flow rates in watered sorghum were less than those in watered sunflower (maximum sap flow rate = 18.9 g h−1), and error for watered sorghum was high (72.6%). The gauge had good accuracy when sap flow rates were 20 g h−1 or more. Despite gauge errors, gauge measurements usually paralleled scale measurements and rapidly monitored changes in sap flow rate. The data suggest that sap flow rate is more important than stem anatomy in determining the accuracy of the gauge.