bluuebunny/crossref_metadata_2025 huggingface dataset:
Tomato Plant Response to Soil Salinity1
Authors: Papadopoulos I. , Rendig V. V.
Published: July 2010

Tomato (Lycopersicon esculentum var. VF 145) plants were grown in a greenhouse to determine the effects of salinity on growth and yield. The plants were grown in soil (Typic Xerofluvents, coarse‐loamy, mixed, nonacid, thermic) using regular or four‐compartment containers allowing splitting of the root systems. Nutrient solutions made saline with NaCI and CaCl2 to electrical conductivities (EC) of 1, 2, 3, 4, and 5 dS/m (dS/M = mmho/cm, referenced at 25°C) were applied twice a day in the undivided root systems. In the split‐root series, each of the four compartments was irrigated with solutions of different EC, while the regular containers were irrigated with a nutrient solution satinized to a level equivalent to the mean value of the solutions used for irrigating the four‐compartment units. The nutrient solutions were recycled through the containers, so that responses of plants subjected to increasing salinity up to 35 dS/m could be evaluated. With increasing salinity fruit fresh weights decreased markedly, with lesser decreases in shoot weights in both systems. Plants with their root systems divided and growing in containers with differentially salinized soil were less severely affected. Yield and growth correlated better with the initial electrical conductivity (ECin) of the nutrient solutions applied than with the EC values of the solutions extracted from the soil. Roots were less sensitive to root‐zone salinity than were tops. In the split‐root system, any reduction in the root growth in the compartments with high salinity levels was compensated for by more growth of those portions of the root system in the less saline environment. During the latter part of the growing period, levels of soil solution salinity were generally greater in the soils in which plants were grown in the undivided root systems than in soils in the split‐root systems.
A Method for Inducing Controlled Moisture Stress on Seedlings1
Authors: Sikurajapathy M. , Cappy J. J. , Gross H. D.
Published: July 2010

Selectively permeable sleeves filled with soil were held in tanks containing various polyethylene gylcol (PEG) 10 000 solutions in order to evaluate seedling tolerance to soil moisture stress. The soil columns, made of 7.6 cm diam dialysis tubing (molecular weight (MW) cut off 8000), were fitted to plexiglas bases and placed in tanks containing PEG 10 000 solutions calibrated to provide the desired soil water potentials (−0.01, −0.1, −0.5, and −1.5 MPa). The columns contained 2.5 kg soil. The membrane maintained its integrity over a 30‐day period. Soil water moved in response to gradients created by the osmoticum; the small pore size of the permeable sleeves prohibited the PEG from entering the soil. Water loss measured for soil columns immersed in PEG solution maintaining −0.01 MPa potential revealed no movement in either direction. At −0.5 MPa, water moved gradually out of the soil column. At the lower potentials (−0.01 and −0.1 MPa), rapid movement of water out of the soil occurred within 20 h, leading to a loss of 60% of the water in the columns. Water content at various column depths after 12 and 30 days immersion at the different potentials were very uniform. No detectable amounts of PEG were found in roots, shoots, or leaves of mungbean [Vigna radiata (L.) Wilczek] or rice (Oryza sativa L.). The technique makes possible precise control of water‐stress intensity (water potential), water‐stress duration, and recovery from water stress.
Plant‐Parasitic Nematode Populations in Bermudagrass as Influenced by Cultural Practices1
Authors: White R. H. , Dickens Ray
Published: July 2010

Plant parasitic nematodes can be a limiting factor in the production of high quality bermudagrass (Cynodonspp.) putting greens. A 3‐year study was initiated in May 1978 on Dothan sandy loam (fineloamy, siliceous, thermic Plinthic Paleudult) to determine the effects of N sources, core aerification, vertical mowing, and topdressing on plant parasitic nematode populations. Nematode populations were determined in the fall of 1978 and 1980 and in the spring of 1979, 1980, and 1981 by a modified flotation sieving technique. Stubby root (Trichodorusspp.), ring (Criconemoidesspp.), stunt (Tylenchorhynhusspp.), and spiral (Helicotylenchusspp.) were the principal nematodes present. Differences in overall populations of nematodes due to N treatment occurred only in the Spring 1980 sampling. Lower populations occurred where activated sewage sludge was the source of N than where NH4NO3was applied. Topdressing, vertical mowing, or core aerification treatments had no consistent effects on nematode populations. Interactions occurred between bermudagrass cultivars and nematode species. ‘Dothan’ selection supported higher populations of stunt and stubby root nematodes than did ‘Tifdwarf’ or ‘Tifgreen’. In contrast, Tifdwarf and Tifgreen supported more spiral nematodes than Dothan. Tifdwarf suported the greatest overall plant parasitic nematode population.
Sunflower for Strip, Row, and Relay Intercropping1
Authors: Robinson Robert G.
Published: July 2010

Yield is greater for some intercropping systems than from sole cropping. The culture and morphology of sunflower (Helianthus annuusL.) indicated that it had potential for intercropping. Consequently, sunflower was evaluated as a component of strip, row, and relay intercropping systems that would be practical for mechanized farming. Trials were conducted on Typic Hapludoll soils. Strip intercropping sunflower with corn (Zea maysL.) or soybean [Glycine max(L.) Merr.] compared with sole cropping showed that the percentage gain in sunflower yield was offset by about the same percentage reduction in corn or soybean yield. Increased yields of sunflower and mustard (Brassica hirtaMoench) from intercropping over sole cropping were confined to the border rows of the sunflower strips and the two border rows of the mustard strips. Yields from intercropped sunflower and soybean in alternate rows 38 cm apart were less than from sole cropped soybean, but 450 kg ha−1higher than from sole cropped sunflower. Fieldbean (Phaseolus vulgarisL.) as a row intercrop with sunflower increased in yield as sunflower population decreased, but its highest intercrop yield was 59% that of sole cropped fleldbean. Relay intercropping involved broadcast sowing of winter rye (Secale cerealeL.) in sunflower and fleldbean. Rye stands in sunflower were unsatisfactory, those in fieldbean ranged from poor to satisfactory, and those established alone on prepared seedbeds were excellent. Sunflower is not a promising species for intercropping. Sunflower‐mustard strip intercropping may be useful in honeybee (Apis melliferaL.) management and in reducing harvest losses of mustard.
Introduction and Survival of an Inoculant Strain of Rhizobium japonicumin Soil1
Authors: Dunigan E. P. , Bollich P. K. , Hutchinson R. L. , Hicks P. M. , Zaunbrecher F. C. , Scott S. G. , Mowers R. P.
Published: July 2010

A 7‐year experiment was begun in 1976 to determine if a nonindigenous inoculant strain of Rhizobium japonicumcould be introduced into, and survive in a soil in Louisiana. The soil was an Olivier silt loam (fine‐silty, mixed, thermic Aquic Fragiudalf) located at Baton Rouge. Inoculation rates were 104or 108R. japonicumstrain 110 cells cm−1of row. The inoculum was applied directly into the furrow as a liquid suspension. The same plots were inoculated for 3 consecutive years. In 1978, a third treatment, 108rhizobia cm−1of row was used as the inoculant and 250 kg NH4NO3‐N ha−1was applied in five equal split applications. None of the plots were inoculated after 1978. ‘Lee’ cultivar was planted in the first 3 years while ‘Dare’, ‘Lee’, ‘Bragg’, and ‘Coker 338’ cultivars were planted in each plot from 1979 through 1982. The cultivars represented Maturity Groups V through VIII. Recovery of the inoculant rhizobia from the soybean (Glycine maxL. Merr.) nodules was quite low during the first 4 years. General recoveries were within the range of 0 to 17% as reported by other researchers for 1 year studies. In 1980 and thereafter, recovery of the inoculant rhizobia increased considerably. Average recoveries over all rates of inoculation ranged from 29 to 33% in 1980 and were up to 54% by 1982. Individual treatment values were as high as 60% from the 108R. japonicumcm−1of row plots in 1982. Results of this study were interpreted to indicate that 3 years of massive soil inoculation with a nonindigenous strain of R. japonicumallowed the permanent establishment of this strain into the soil. Once established, this strain became competitive with the native rhizobia in the soil, and each year formed a higher percentage of the nodules on the soybean roots.
Restricted Rooting Decreases Tillering and Growth of Winter Wheat1
Authors: Peterson Curt M. , Klepper Betty , Pumphrey F. V. , Rickman Ron W.
Published: July 2010

Winter wheat [Trificum aestivum(L.) em Thell. cv. Stephens] seedling growth and development were observed for plants grown in a greenhouse in 1.65 × 10 ‒4m3or 3.40 × 10 ‒3m3of potting soil to determine the effect of restricted root development on plant growth with adequate water and minerals supplied. Plants grown in a smaller volume of soil were significantly reduced in size as measured by number of leaves and culms/plant, main stem height, and final dry weight/plant. These results suggest that confining roots to a small volume of rooting medium will in itself limit coordination of plant growth in an otherwise suitable environment.
Methods of Placement for Increasing the Efficiency of N Fertilizers Applied in the Fall1
Authors: Malhi S. S. , Nyborg M.
Published: July 2010

In portions of the Prairie Provinces of Canada, fall‐applied fertilizer N is often less effective in increasing yields of cereal crops than fertilizer N applied in the spring. Field experiments were conducted in northern and central Alberta on Udic Boroll, Boralfic Boroll, and Boralf soils to find if there was a consistent increase in yield and N uptake of barley (Hordeum vulgare L.) when fall‐applied urea was placed in bands and in nests as compared to the conventional mixing into the soil. There were 14 field experiments with the fallapplications during 3 years, and 13 of the experiments were cropped. The crop was spring‐sown barley. Fall‐applied urea gave higher grain yield, recovery of N in grain and recovery of N in grain + straw when placed in 46 cm spaced bands, and more so in nests, than when urea was incorporated into soil in the conventional manner. Nests were obtained by placing the N fertilizer at a point in each area of 46 ✕ 46 cm and at a depth of approximately 5 cm. The average increases in grain yield from urea incorporated in the fall, from urea banded in the fall, from nest placement of urea applied in the fall, and from urea incorporated in the spring at seeding time were 810, 1220, 1530, and 1680 kg ha−1, respectively. In the same order, the recoveries of fertilizer N in grain plus straw were 26, 40, 53, and 61% although values were similar for banding and nest placement in 5 of the 13 experiments. Nitrification of fall‐applied N was slowed with banding and especially with nests, as compared to incorporation. With less nitrification, there was less over‐winter loss of fall‐applied N, apparently through reducing denitrification. As with urea, fall‐applied aqua NH3 placed in nests produced greater grain yield, N uptake by grain and N uptake by the whole plant as compared to aqua NH3 injected in bands. There were six other cropped experiments where there was only spring application of nesting, banding, and mixing. With spring application, nest placement of urea was inferior to banding or mixing of urea, unless the spacing of nests was reduced from 46 ✕ 46 cm to 23 ✕ 23 cm or the application of nests was made 2 weeks before sowing with subsequent cultivation. Nest placement is an alternative to chemical inhibitors of nitrification with fall‐applied N fertilizers.
Dinitrogen Fixation in Alfalfa‐Orchardgrass Pastures1
Authors: West C. P. , Wedin W. F
Published: July 2010

Information on amounts and proportions of alfalfa N derived from symbiotic N2 fixation is needed to more effectively exploit this source of N in alfalfa‐orchardgrass (Medicago sativa L.‐Dactylis glomerata L.) pastures. Our objectives were to describe the seasonal trends in N2 fixation and to assess the relationships among alfalfa dry matter (DM) yield, percentage alfalfa in the mixture, and N2 fixation. The trial was carried out in south‐central Iowa in 1979 and 1980 on Aquic Argiudoll and Typic Argiaquoll soils, 2 to 13% slope. A 15N‐dilution technique was used to estimate the percentage of alfalfa N derived from N2 fixation during individual harvest intervals. The percentage of alfalfa N derived from N2 fixation varied slightly among harvest dates and averaged 91%. As percentage alfalfa in the mixture and alfalfa DM yield increased, the percentage of alfalfa N derived from fixation tended to decrease. The amount of N2 fixed was highly positively correlated with percentage alfalfa and alfalfa DM yield in both years. The total annual amount of N2 fixed averaged 70 kg ha−1 with a range across microplots of 15 to 130 kg ha−1. In conclusion, alfalfa DM yield was the major determinant of the amount of N2 fixed. The coefficient 0.90 can be used under these conditions to estimate the proportion of harvestable alfalfa N derived from N2 fixation when growing with orchardgrass. The low variability associated with measurements of percentage of alfalfa N derived from fixation illustrated the usefulness of the 15N‐isotope dilution method in this study.
The Fate of Diazinon Applied to Thatched Turf1
Authors: Branham B. E. , Wehner D. J.
Published: July 2010

Diazinon [0,0‐diethyl‐0‐(2‐isopropyl‐6‐methyl‐4‐primidinyl) phosphorothioate] is widely used to control turfgrass insect pests. Poor control of soil‐inhabiting insects has been found where diazinon has been applied to thatched turfgrass stands. The purpose of this study was to evaluate the environmental fate of diazinon applied to turfgrass stands. A microecosystem was used to follow the fate of radiolabeled diazinon surface applied to Kentucky bluegrass (Poa pratensis L.) turfs, with or without a thatch layer, growing on Flanigan silt loam (fine, montmorillonitic, mesic Aquic Argiudoll) irrigated daily or every 4 days. Loss of diazinon by volatilization, leaching, and degradation accompanied by release of 14CO2 or incorporation of label into soil compounds was measured. The most degradation of parent compound occurred on turf containing a thatch layer irrigated daily where only 7% of the applied diazinon remained after 3 weeks. Between 32 and 47% of the parent compound remained in either turf with thatch irrigated every 4 days or turfs without thatch. The majority of the diazinon (96%) remained in the top 10 mm of the turf profile regardless of whether this was thatch or soil. In the presence of thatch, there was an accelerated rate of diazinon degradation as measured by release of 14CO2 from the two position on the pyrmidine ring. Increasing irrigation frequency on the thatched turf did not cause an increase in leaching but did increase diazinon breakdown. The results of the study suggest that where thatch is present, reduced control of insects is due both to a failure of the insecticide to move through the thatch and an increased rate of degradation.
Leaf Area Index and Evapotranspiration of Taro1
Authors: Shih S. F. , Snyder G. H.
Published: July 2010

Standard pan evaporation has been used to estimate evapotranspiration under flooded conditions, but it is difficult to determine crop coefficients, which vary with growth stage and leaf area index. Taro [Colocasia esculanta(L.) Schott], a wetland plant, was used to study the relationships among standard pan evaporation, evapotranspiration, and leaf area index. Lysimeter investigations were conducted for 2 yr (1981–1982) on flooded Pahokee muck (Lithic Medisaprists). Total evapotranspiration was about 1200 mm and ranged from 1.5 to 7.2 mm day−1, with an average of 4 mm day−1. The evapotranspiration/standard pan evaporation ratio was inversely related to leaf area index, whereas in nonflooded crops it is directly related
A Comparative Study of Root Distribution and Water Extraction Efficiency by Wheat Grown Under High‐ and Low‐Frequency Irrigation1
Authors: Proffitt A. P. B. , Berliner P. R. , Oosterhuis D. M.
Published: July 2010

A number of field experiments have separately evaluated plant responses to water stress, root distribution and soil water extraction patterns, consumptive water use, grain yield, and water use efficiency (WUE); few studies have investigated water movement through the soil‐plant‐atmosphere continuum as a whole. A field study was therefore conducted on spring wheat (Triticum aestivumL. cv. SST33), sown on a Rhodic Paleustalf soil in the Republic of South Africa, to relate the response of the plant and its root system to different water application frequencies. Special emphasis was on a soil dryingout period. Treatments consisted of high‐ and low‐frequency irrigation, with one treatment from each being maintained as a wellwatered control (HFc, and LFc, respectively), and one treatment from each being subjected to a period of water stress after anthesis (HFsand LFsrespectively). Soil water content, root length and distribution, and leaf water potential (ΨL) were monitored before and after irrigations and during the soil drying‐out period. Plants in the HFsand LFstreatments developed shallower rooting systems than plants in both the LFcand LFstreatments. Soil water extraction patterns were correlated to rooting distributions. Deeper roots became increasingly efficient at extracting water as the soil became progressively drier from the surface downwards, but the total water uptake was insufficient to enable the plants to transpire at their potential rate. The departure of the evapotranspiration/potential evapotranspiration (ET/PET) ratio from its well‐wateredvalue occurred at 14% (HFs) and 17% (LFs) depletions from field capacity, and this, coupled with the concomitant decrease in ΨL, suggests that plants can maintain a constant ET/PET ratio only when water is freely available in the upper soil layers. Frequent light applications of water resulted in reduced fluctuations in ΨLthus, higher yields and an improved WUE were obtained.
Growth Analysis of Soybean Isolines Differing in Pubescence Density1
Authors: Clawson K. L. , Specht J. E. , Blad B. L.
Published: July 2010

Genetic variation in soybean plant morphology is of interest beause of its possible utility in developing cultivars adapted to unique environments. Growth analysis techniques were used to quantify and compare soybean [Glycine max(L.) Merr.] growth in genotypes differing in pubescence density. The experiment was conducted in 1980 and 1981 at Mead, NE on a Typic Argiudoll soil. Data from frequent samplings of phytomass dry weight (W), leaflet dry weight (LW), leaf area (A) and number of leaflets (N) were collected during two crop seasons from near‐isogenic lines of dense and normal pubescent types of ‘Clark’ and ‘Harosoy’ cultivars. Statistical curve‐fitting tests identified the most plausible mathematical models for describing the change of these four variables over time. Ten growth analysis parameters based on these four model equations were then computed and included crop growth rate (CGR), net assimilation rate (NAR), leaf area ratio (LAR), relative growth rate (RGR), leaf weight ratio (LWR), specific leaf area (SLA), relative leaf growth rate (RLGR), relative leaf area expansion rate (RLAER), leaf area partitioning factor (LAPF), and area per leaflet (APL). Dense pubescence affected the growth parameters differently in the two cultivars. There was no difference in any parameter between dense and normal pubescence lines in Clark. The W, LW, A, N, and CGR were, however, affected by pubescence density in Harosoy. The CGR was about 20% greater at maximum growth in the dense Harosoy isoline. The NAR was unaffected, however, indicating that the higher photosynthetic rate in the Harosoy dense pubescent isoline was due to an increase in leaf area and not an increase in photosynthetic efficiency. The fact that the gene giving rise to dense pubescence had differential effects on growth in the two cultivars suggests that the genetic background into which the gene is introduced influences the effect of the gene on growth.
Distribution of Dry Matter Between Shoots and Roots of Irrigated and Nonirrigated Determinate Soybeans1
Authors: Huck M. G. , Peterson Curt M. , Hoogenboom Gerrit , Busch C. D.
Published: July 2010

The timing and duration of drought stress during a growing season can both limit and alter dry‐matter accumulation within plants. Distribution of dry matter between roots and aboveground parts was determined by growing soybean (Glycine max [L.] Merr., cv. ‘Bragg’ or ‘Braxton’) plants for 4 consecutive years (1980–1983) in a sieved, sandy surface soil material, uniformly packed to a bulk density of 1.52 Mg/m3 in soil compartments at the Auburn rhizotron. Three replicated compartments were irrigated by trickle irrigation (IR) whenever the soil water potential (Ψs) fell below ‐ 15 kPa at a depth of 0.4 m. Three additional compartments were not irrigated (NI). Mainstem leaf area and total cumulative root growth were determined at regular intervals. Water stress significantly reduced total shoot weight (347 g/m2) and seed weight (171.2 g/m2) but increased total root length (52 m/m2). Irrigated plants generally had fewer roots, which were generally shallower and more evenly distributed than those of NI plants. Both individual seed weight and total seed weight per treatment were significantly reduced by water stress (0.009 g/seed and 171.2 g/m2, respectively). Apparent harvest index varied between 0.36 and 0.56. A nearly linear relationship was observed between normalized final seed yield (y = 110.8 ‐ 0.738x, r2 = 0.86) or total dry matter (y = 113.3 ‐ 0.685x, r2 = 0.93) production and the percentage of time between flowering (R1) and harvest maturity (R8). Thus, aboveground dry‐matter production and seed yield are directly dependent upon availability of water during critical reproductive states.
Effects of Temperature on Fiber Concentration, Composition, and In Vitro Digestion Kinetics of Tall Fescue1
Authors: Fales S. L.
Published: July 2010

High temperatures during the growth of forage grasses adversely affect forage quality, but there is little information concerning possible temperature effects on the digestion characteristics of the cell wall. The purpose of this study was to examine the influence of different temperature regimes on the amount, the rate, and the extent of in vitro cell wall digestion in tall fescue (Festuca arundinacea Schreb.). Vegetatively propagated tall fescue plants were grown in a controlled environment over a period of 315 days, during which time the temperature was changed sequentially from 13/10 (T1), to 20/18 (T2), 30/27 (T3), and back to 13/10 (T4)°C, day/night, for a 14‐h photoperiod. Plants were harvested three times at 28‐day intervals at each temperature, after which the temperature was changed. Leaf material from the second and third harvests at each temperature was oven‐dried and ground for analysis. The first harvest at each temperature was discarded in order to reduce the confounding of treatments. Concentrations of neutral detergent fiber (NDF), cellulose, and hemicellulose increased with temperature up to T3 and decreased at T4, while lignin concentration remained about the same. Digestible NDF represented a greater proportion of dry matter in all temperature treatments but showed less variation with treatments than did indigestible NDF. Concentrations of indigestible NDF increased each time temperature was raised and decreased when temperature was lowered. Indigestible NDF concentrations were equivalent to T1 and T4. Rates of digestion of potentially digestible NDF followed first order reaction kinetics, and there were no temperature‐related differences in digestion rate constants. No direct relationship was shown between lignin concentration and digestion. The results indicate that high temperature causes reduced cell wall digestibility by increasing the amount of indigestible cell wall without affecting the rate of digestion of the more labile fraction.
Mineral Analysis of Forages with near Infrared Reflectance Spectroscopy1
Authors: Clark D. H. , Mayland H. F. , Lamb R. C.
Published: July 2010

Mineral concentration data could easily be generated by near infrared reflectance spectroscopy (NIRS) while determining quality parameters in forage samples. However, which minerals can be analyzed and why they can be determined has not been documented adequately. Therefore, NIRS spectra were collected on 200 samples of crested wheatgrass (Agropyron spp.), 203 tall fescue (Festuca arundinacea Schreb.), and 59 alfalfa (Medicago sativa L.) hays. Concentrations of Na, K, Ca, P, Mg, Fe, Mn, Cu, and Zn, as determined by atomic absorption, and calculated values of the Ca/P, K/Mg, and K/(Ca+Mg) ratios were regressed against reflectance values measured in 2‐nm increments between 1100 and 2500 nm for each sample. Approximately one half of the samples in each forage set was used to develop the calibration equations, while the other half was used to validate the equations. The coefficients of variation [CV=(standard error of analysis÷the mean) X100] generally ranged from 10 to 20% for K, Mg, Ca, and P concentrations in each forage type. The Ca/P ratio in alfalfa was determined with a CV of 18%. The CV values of other minerals and mineral ratios generally exceeded 20%. Chlorophyll and some inorganic salts and organic‐acid salts of Ca, Mg, and K were scanned with NIRS for wavelength comparisons with those wavelengths used to determine mineral concentrations in forages. Some of the wavelengths used in the equations for Ca, K, and Mg were related to peaks and changes in slope observed in chlorophyll and organic‐acid salts of Ca, K, and Mg, suggesting that NIRS is indirectly measuring these minerals by their association with organic molecules. Accurate use of NIRS to determine mineral cation composition in forages appears limited to certain major minerals (Ca, P, K, and Mg).
Simulated Acid Rain Effects on Yield Response of Two Corn Cultivars1
Authors: Banwart W. L. , Porter P. M. , Hassett J. J. , Walker W. M.
Published: July 2010

Acid rain is a documented phenomenon over much of the eastern and midwestern United States, including major portions of the Corn Belt. However, few studies report the effect of acid rain on yield of corn (Zea mays L.). Field experiments were conducted in 1983 and 1984 on a Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudoll) soil at Urbana, IL. Two corn cultivars (Pioneer 3377 and B73✕Mol7) were protected from ambient rain by two automated movable rain exclusion shelters and were exposed to one of six simulated rain acidities ranging from pH 5.6 to 3.0. Analysis of the effect of rainfall pH on grain yield showed no significant linear or quadratic trend (α=0.10) for either cultivar in individual years or with both years combined. Comparisons among treatments for both cultivars showed rain simulants with no added acid (pH 5.6) resulted in grain yields that were not significantly different from the average grain yields of the other five pH treatments. For B73✕Mol7, the 2‐yr combined yield for the pH 3.0 treatment was significantly lower (5.7%) than the average yield for the other five treatments. This same contrast was not significant for Pioneer 3377. These results imply that under normal environmental conditions and agronomic practices, rainfall at its present levels of acidity has little if any effect on corn yields.
Soil Chemical Factors Associated with Soybean Chlorosis in Calciaquolls of Western Minnesota1
Authors: Inskeep William P. , Bloom Paul R.
Published: July 2010

Iron chlorosis in soybean [Glycine max (L.) Merr.] is a significant problem in calcareous soils of the upper Midwest. Field studies were established during 1983 in western Minnesota on two sites containing calcareous soils and one site containing gypsic‐calcareous soil (Typic Calciaquolls) to evaluate the soil chemical properties associated with iron chlorosis in soybean. Chlorosis was correlated with increases in soil solution bicarbonate (HCO−3) at the two calcareous sites, but not at the gypsic‐calcareous site. Chlorosis was correlated with increases in total calcite (CaCO3) at all sites. Higher concentrations of soil solution Ca2+ and SO2−4 were found at the gypsic site as a result of greater gypsum (CaSO4. 2H2O) solubility relative to CaCO3 solubility. However, because both CaCO3 and CaSO4. 2H2O were correlated with chlorosis at this site it was difficult to determine which may have been the most important causal factor. Concentrations of mobile soil solution ions such as K+, Na+, Mg2+, and NO−3 were generally greater in chlorotic areas of all sites as a result of accumulation in lower landscape positions associated with chlorosis. Seed yields were correlated with chlorophyll contents measured in the third trifolioliate leaf stage (V4) and during flowering (R1). Chlorosis ratings ranging from 2.5 to 5 resulted in 35 to 40% yield reductions for each unit chlorosis rating (1–5 scale). Increases in plant tissue K, Ca, Mg, Cu, Zn, Mn, and B were associated with increases in chlorosis for all cultivars at all sites. These increases may have been due to a combination of factors including ion balance, concentration of elements in stunted plants, and contamination of chlorotic tissue by soil.
Using Satellite Data to Improve Model Estimates of Crop Yield
Authors: Maas S. J.
Published: July 2010

It has been proposed that remotely sensed information from satellites could complement the performance of crop growth models. A study was conducted to determine how a model could effectively utilize satellite data and if model estimates of crop yield could be significantly improved by satellite data. A simple model was developed for simulating growth and yield of grain sorghum [Sorghum bicolor (L.) Moench] on an individual‐field basis. The model contained three state variables (stage of development, green leaf area index [GLAI], and aboveground dry mass) and utilized daily meteorological observations. When available, GLAI values for target fields could be used to adjust the initial values of the state variables until a “best fit” of the observed data was iteratively achieved by the simulation. GLAI values could be obtained by ground‐based measurements, but satellite observations were demonstrated to be an appropriate source of data for initializing the model. The model was developed and verified using data from 10 fields observed in Central Texas in 1976. The model was tested using a completely independent data set containing yield and satellite observations from 37 fields in South Texas in 1973, 1975, 1976, and 1977. Without using the initializing procedure, the average yield for the 37 fields was underestimated by approximately 30%. Use of satellite‐derived GLAI data to initialize the same simulations resulted in a 2% overestimate of average yield. The results of this study confirm the usefulness of the initializing procedure and satellite data to improve model estimates of crop yield.
Ethephon Influence on Harvestable Yield, Grain Quality, and Lodging of Corn
Authors: Norberg O. S. , Mason S. C. , Lowry S. R.
Published: July 2010

To determine if ethephon ((2‐chloroethylphosphonic acid) would reduce lodging while maintaining or increasing harvestable yield, the influence of timing and rate of ethephon application on harvestable yield, yield components, lodging, and grain quality of corn (Zea mays L.) was studied in 1985 and 1986. Ethephon was applied at rates of 0, 0.14, 0.28, and 0.56 kg ha−1 at tassel elongation (TE), 6 d after tassel elongation (TE+6), and at ear elongation (EE), to Pioneer hybrids P3475, P3377, and P3183 grown in the field near Mead, NE. Application of ethephon reduced lodging of corn plants. Ethephon application of 0.56 kg ha−1 at the EE stage reduced lodging of P3377 and P3183 from 30 to 9%. This rate resulted in production of 52 fewer kernels per ear, and 7 to 17 mg lighter kernel weight, while increasing the number of harvestable ears by 0.2 to 0.6 ears m−2. Increasing the rate of ethephon resulted in a linear decrease in harvestable grain yield, except when applied at the EE stage in 1986, when ethephon application had no influence. In this case, increasing the rate of ethephon resulted in an increased number of harvestable ears per square meter, which compensated for reductions in the number of kernels per ear and kernel weight. Application of 0.56 kg ha−1 ethephon at TE in 1986, TE+6 in both years, and EE in 1985 resulted in approximately 1 Mg ha−1 reduction in harvestable grain yield. Ethephon application had small but significant influence on the protein content, kernel density, and kernel breakage susceptibility of grain produced. Application of ethephon is effective in reducing lodging of corn plants. However, ethephon never increased and usually reduced harvestable grain yields. Based on these results, there is little incentive for producers to consider application of ethephon to corn grown under conditions similar to those in this study.
Spring and Fall Cattle Grazing Effects on Components and Total Grain Yield of Winter Wheat
Authors: Christiansen S. , Svejcar T. , Phillips W. A.
Published: July 2010

Farmers and ranchers growing winter wheat (Triticum aestivum L.) in the Great Plains have the practical problem of obtaining maximum grazing with minimum loss of grain yield. The objective of this study was to examine the impact of grazing on subsequent grain, straw, and chaff production of a semidwarf winter wheat (‘TAM W‐101’). Steers (Bos taurus L.) weighing 250 to 350 kg grazed wheat pasture during 3 yr at the Forage and Livestock Research Laboratory near El Reno, OK. Soils at the study site were fine‐silty, mixed, thermic Pachic Haplustolls of the Dale series. Climatic conditions allowed 212 to 338 animal days (AD) ha−1 of fall grazing in 1983 to 1984; 78 to 141 AD ha−1 spring grazing in 1984 to 1985; and 151 to 516 AD ha−1 fall and/or spring grazing in 1985 to 1986. Straw, total grain yield, seed weight, seeds per spike, and spikes m−2 were determined. Heavy (H) and light (L) fall (F) grazing intensities caused lower (P < 0.05) grain yields compared to controls (C) in 1983 to 1984 (2.94[F‐L] and 2.53 [F‐H] vs. 3.51 [C] Mg ha−1); lower, but nonsignificantly different grain production after spring (S) grazing in 1984 to 1985 (2.73 [S‐L] and 2.44 [S‐H] vs. 2.60 [C] Mg ha−1); and mixed results with fall‐only, spring‐only, and two levels of fall and spring grazing in 1985 and 1986 (2.41 [F‐L], 1.37 [S‐L], 1.80 [F,S‐L], and 1.46 [F,S‐H] vs. 1.90 [C] Mg ha−1). Grazing generally decreased the number of spikes m−2. Straw yields were lowered by grazing in all 3 yr, therefore, harvest index of grain was nearly always higher for grazed wheat. Weather differences affected grain production from year to year more than grazing stresses within a year. Components of yield were influenced in an inconsistent manner by the treatments. However, grazing did not damage TAM W‐101 grain yield, when moderate grazing was used, trampling was avoided, excess autumn forage was removed and/or no severe weather adversities added to grazing stress on the crop.
Corn Residue Effect on the Yield of Corn and Soybean Grown in Rotation
Authors: Crookston R. K. , Kurle J. E.
Published: July 2010

Crop rotation provides a yield benefit that persists at optimal management levels. The exact reason for the rotation effect is unknown. One theory is that a given crop's own residue has an autoinhibitory effect when that crop is maintained under monoculture, and/or that residues of alternate crops have a stimulatory effect on one another under rotation. We conducted field studies at Lamberton, Rosemount, and Waseca, MN to test this theory. Soils at these locations are: Webster clay loam (fine‐loamy, mixed mesic Typic Haplaquolls), Waukegan silt loam (fine‐silty, over sandy, mixed, mesic Typic Hapludolls), and NicoIIet clay loam (fine‐loamy, mixed, mesic Aqnic Hapludolls), respectively. A series of 3‐yr crop sequences were established at each site. In the first year the experimental area was kept fallow. In the second year half of each replicated plot was planted to corn (Zea mays L.) and half to soybean (Glycine max (L.) Merr.) After grain harvest all above‐ground corn residue was removed from half of the corn area and transferred to half of the soybean area. All plots were then moldboard plowed. In the spring of the third year all plots were disked and planted uniformly in corn (1981, 1982) or soybean (1983, 1984). There was a significant effect of previous crop (rotation effect) on the yield of both corn and soybean, but the removal or addition of corn residue had no effect on the yield of either crop. This indicates that the yield response of corn and soybean to rotation is not due to beneficial or negative effects of decomposing above‐ground residue.
Nitrate Concentration in Potato Petioles from Periodic Applications of 15N‐Labeled Ammonium Nitrate Fertilizer
Authors: Roberts S. , Cheng H. H. , Farrow F. O.
Published: July 2010

Concerns for N use efficiency prompted a tracer study of the effectiveness of applying supplemental N fertilizer throughout the growing season. The purpose of the study was to monitor the concentration of 15NO3‐N in petioles of Russet Burbank potato (Solanum tuberosum L.) following periodic treatments of 15N‐labeled NH4NO3 on Quincy loamy sand (mixed, mesic Xeric Torripsamments). The experiments were conducted for 5 yr with main plot N rates of 224, 336, and 560 kg ha−1 as NH4NO3 split into starter and supplemental applications. Split plot treatments consisted of labeling the NH4NO3 with 15N at various times. Results indicate that supplements of 15NH4 15NO3 were taken up by the plants and concentrated in petioles within 1 wk after application at various times throughout the growing season. The 15N from pre‐emergence starter fertilizer applied in May was evident in petiole NO3 at each petiole sampling through the entire season. Uptake of the 15NO3 source reached a higher peak in petioles 1 wk to 10 d ahead of 15NO3 that was nitrified and taken up from applying the same rate of labeled 15NH4 source. The uptake of labeled NH4 in petioles was not determined. These data suggest that monitored petiole NO3 values could underestimate the soil N available from NH4 fertilization. These results with 15N tracer indicate that the process of N uptake is a dynamic one which continues as long as plants are active throughout the growing season.
Simulation of Carbon Assimilation and Partitioning in Maize
Authors: Grant R. F.
Published: July 2010

Crop simulation models offer a means of integrating scientific findings into a coherent description of crop adaptation to a complex environment. The detailed simulation of growth processes involved in carbon accumulation and partitioning is an essential prerequisite for modelling such adaptation. A procedure for simulating these processes in maize (Zea mays L.) was developed as part of a larger maize growth model. Hourly values for the gross photosynthetic rate of a maize canopy are accumulated into a pool from which hourly values of carbohydrate mobilized for both shoot and root growth are removed. Maintenance and growth respiration of both the shoot and root are then subtracted from the respective allocations of mobilized carbohydrate and the remainders accumulated into daily totals of dry matter growth. These daily totals are partitioned to and accumulated in the major plant organs depending upon growth stage. Growth partitioned to the leaves is converted to leaf area growth. Kernel number and maximum kernel mass are determined from growth functions during stages of ear formation and kernel set. Maturity is presumed to occur when maximum kernel mass is reached or when kernel growth is stopped due to inclement weather. Model output for partitioning, biomass, grain yield, kernel number, kernel mass, and leaf area index were compared with observed values at several sites across North America. Although many of the processes upon which the model is based require greater understanding, the model is able to provide estimates of these variables that are usually within 20% of recorded values. Greater accuracy in simulating maize growth will require further elucidation of the way in which environment influences basic growth processes as well as more detailed information regarding site‐specific soil and meteorological characteristics.
Corn Growth Response to Temperature: Rate and Duration of Lead Emergence
Authors: Hesketh J. D. , Warrington I. J.
Published: July 2010

Seasonal predictions of gas and energy exchange in crop canopies require a quantitative description of temperature effects on leaf area development. Such predictions are needed in crop management and forecasting models. Our objectives were to quantify temperature effects on leaf emergence rates, determined as lengths and areas of fully expanded emerged leaf material, and their duration in corn (Zea mays L.). Hybrids were grown in controlled environments under 16 temperature regimes ranging from 16/11 to 38/33 °C (12‐h day/night thermal periods). Plants were dissected every 3 to 10 d, depending on the temperature, to determine the mainstem node number associated with the youngest leaf primordium as well as weight, area, and length per leaf. The node number of the youngest leaf showing a ligule was recorded. Leaf emergence rates, either as lengths or areas per unit time, and the node associated with the youngest visible leaf tip were derived from time plots of emerged leaf lengths and area. Emergence duration was estimated three ways: (i) the time between appropriate leaf developmental events, from time plots, (ii) mature leaf length divided by its extension rate, and (iii) mature leaf area divided by its area emergence rate. Primordia and ligule appearance rates derived from these data were published earlier. The relationships between temperature and tip appearance rates, leaf emergence rates, and the reciprocals of the various estimates of duration were determined; threshold temperatures and degree day requirements for processes derived from such plots are presented. Other information is provided for developing logic for predicting temperature effects on the development of canopy leaf area in corn.
Amyloglucosidase Hydrolysis Can Overestimate Starch Concentration of Plants
Authors: Denison R. F. , Fedders J. M. , Tong C. B. S.
Published: July 2010

Reported β‐glucanase activity by amyloglucosidases used in starch determination might lead to significant overestimates of starch concentration in plant tissue. To test this hypothesis, two amyloglucosidases and a porcine α‐amylase were evaluated using four starch and three β‐glucan preparations. The enzymes were also used to estimate starch concentration of alfalfa (Medicago sativa L.) roots and tall fescue (Festuca arundinacea Schreb.) and orchardgrass (Dactylis glomerata L.) stem bases. Release of reducing sugars by the α‐amylase was consistent with 95 to 98% hydrolysis of starch to maltose, and <3% hydrolysis of β‐glucans. The widely used amyloglucosidase from Rhizopus gave 89 to 93% hydrolysis of starch, but also 35 to 83% hydrolysis of β‐glucans. Hydrolysis with α‐amylase gave calculated starch concentrations for the grasses which were not significantly different from zero, but the Rhizopus enzyme gave starch estimates of 32 and 52 g kg−1 for tall fescue and orchardgrass, respectively. The amyloglucosidase from Aspergillus gave intermediate results. Neither amyloglucosidase should be used to estimate plant starch concentration.
Quantification and Classification of Locational Effects on Cotton Cultivar Testing Programs
Authors: Geng Shu , Hu Bingmin , Bassett Dick M.
Published: July 2010

Multiple locations are commonly used to evaluate cultivar performance in breeding programs, but the relative contribution of location to cultivar selection is rarely discussed. This paper presents a method by which locational effects can be quantified and classified. Lint yield data of upland cotton (Gossypium hirsutum L.) obtained from the U.S. Regional Cotton Variety Tests between the years 1981 and 1986 were used to quantify four characteristics of the locations which were used in testing cultivars. The four characteristics of the locations are: the ability to discriminate differences among cultivars, consistency in discrimination over years, relative potential productivity, and repeatability of the potential productivity. These characteristics which are estimated from the yield data are used to evaluate the effectiveness of the location in testing cultivars. When the estimates of the characteristics are subjected to cluster analysis, a new basis for zoning the cotton belt for the cotton testing program is revealed. The resulting regions include locations which are different from the regions derived from yield data or derived from cultivars by environmental interactions. Results of this study provide an alternative basis for possible future rezoning of the U. S. Cotton Belt for cultivar testing.
Magnesium, Nitrogen Form, and Root Temperature Effects on Grass Tetany Potential of Wheat Forage
Authors: Huang J. W. , Grunes D. L. , Welch R. M.
Published: July 2010

Grass tetany, a Mg deficiency syndrome, is a disorder of ruminants grazing grass or cereal forages under certain environmental conditions. A solution culture experiment was conducted to gain a clearer understanding of the nutritional and environmental factors affecting Mg concentrations in winter wheat (Triticum aestivum L.) forage. Effects of N form (NH4/NO3 in mM—10:0, 5:5, or 0:10), root‐zone temperature (RZT) (10,15, or 20 °C), and Mg supply (0.4 or 4 mM) on growth and mineral composition of winter wheat forage were investigated. Shoot and root yields were highest for the mixed‐N form, and increased linearly with increasing RZT. Increasing the Mg supply significantly increased Mg concentrations, and decreased Ca concentrations, in both shoots and roots. Concentrations of K and Ca, and estimates of total organic acids significantly increased with increasing proportion of NO3. There was no significant effect of N form on shoot Mg concentrations at the high Mg level. However, at the low Mg level, increasing the proportion of NO3 significantly decreased shoot Mg concentrations, producing a forage more likely to cause grass tetany. Ratios of Mg accumulated in shoots to Mg in whole plants were negatively correlated with K concentrations in roots. Correlations with K concentrations in shoots were much lower. Apparently, increasing the K concentration in roots depressed the rate of net Mg translocation from roots to shoots. When Mg in the root zone is low and K is high, increasing the proportion of NO3 may decrease shoot Mg concentration and thus increase the likelihood of hypomagnesemia.