bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Nitrapyrin on N Response of Corn on Sandy Soils1
Authors: Chancy H. F. , Kamprath E. J.
Published: July 2010

Preplant N fertilizer applications on sandy Coastal Plain soils are often less efficient than sidedress N applications due to leaching of NO−3 from the rhizosphere. Preplant‐incorporated broadcast applications of ammoniacal N fertilizers containing the nitrification inhibitor nitrapyrin [2‐chloro‐6(trichloromethyl)pyridine] should increase utilization of the exchange capacity of sandy soils to retain NH+4 and increase preplant N fertilizer efficiency. The effects of N rate, N source, and nitrapyrin on inorganic soil N form, soil N content, and corn (Zea mays L.) growth were investigated in 1977 on a Marlboro sand (Typic Paleudult) and a Varina loamy sand (Plinthic Paleudult) and in 1978 on a Wagram sand (Arenic Paleudult). Nitrogen treatments consisted of a zero‐N check, preplant broadcast applications of 56, 112, 168, and 224 kg N/ha as urea, 112 kg N/ha as NaNO3, and 112 kg N/ha as urea plus 1.12 kg nitrapyrin/ha dissolved in water.

Soil N measurements at 34, 40, and 48 days after N treatment application on the Marlboro, Varina and Wagram soils, respectively, showed that nitrification was suppressed by nitrapyrin. The lack of significant differences in inorganic soil N contents in the 0 to 15 cm depth among 112 kg N/ha supplied as urea with and without nitrapyrin and NaNO3 indicated that little leaching occurred in 1977. Leaching conditions in 1978 resulted in large losses of inorganic N from the rooting zone; however, when nitrapyrin was added with urea, losses of N were significantly reduced. High N rates from urea decreased the pH in all soils except when nitrapyrin was included. In 1977, inclusion of nitrapyrin with urea had little effect on leaf N, grain yields, plant N accumulation or N fertilizer recovery due to small losses of soil inorganic N. However, in 1978 when leaching conditions occurred, nitrapyrin with urea decreased soil N losses, significantly increased leaf N concentration, grain yields, plant N accumulation and N fertilizer recovery.
Reducing Moisture‐Induced Error Associated with Measuring Forage Quality Using Near Infrared Reflectance1
Authors: Fales S. L. , Cummins D. G.
Published: July 2010

Sample moisture may impair accuracy in predicting forage quality based on near infrared‐reflectance (NIR), but the literature contains little specific information on the topic. The purpose of this study was to determine the extent to which moisture interferes with the ability of NIR to predict acid detergent fiber (ADF) in silage‐type sorghums [Sorghum bicolor (L.) Moench.]. Comparisons were made between laboratory and predicted ADF on samples that were oven‐dry or had been stored at 43% (low), 63% (medium), and 100% (high) relative humidities. Results showed no significant differences between laboratory and predicted ADF for samples that were dry or had been stored under conditions of low humidity. However, when samples were stored under medium or high relative humidities, a significant (P ≤ 0.05) over‐estimation of ADF resulted. Increased sample moisture lowered predictability, since the standard error of estimate increased from 1.27 and 1.18 for dry and low moisture samples, to 2.28 and 4.15 for medium, and high moisture samples, respectively. Consistently repeatable ADF values were obtained when calibrations and NIR analyses were conducted on oven‐dry material, which emphasizes that NIR analyses should be conducted only on recently oven‐dried material that has been stored in a desiccator.
Response of Tomatoes to N and Water Applied Via a Trickle Irrigation System. I. Nitrogen1
Authors: Bar‐Yosef B. , Sagiv B.
Published: July 2010

Despite the widespread use of combined trickle irrigation and fertilization (fertigation) in arid zones, little is known about the efficiency of point source fertigation in general, and about drip irrigation management of tomatoes in particular. The objective of the present work was to study the response of tomato plants grown under trickle irrigation in sand dunes to total and daily N application rates, and to concentrations of N in the irrigation water and in the soil solutions at various physiological stages of growth.

The experiments, carried out at three different locations in Israel, included combinations of several daily N and water application rates and two irrigation intervals.

The total yield (Y, in metric tons/ha) was related to total N application rate (X, in kg/ha) by the regression equation Y = 0.0714X + 35.83. The overall N uptake in the high‐yield treatments was about 30% of the N applied. The low efficiency is attributed partly to excessive N application 140 days from seeding, when the daily demand for N (FN) was small. To obtain the optimum FN values at about 70 and 140 days after seeding (5.2 and 2.2 kg N ha−1day−1), NO3‐N concentration in the soil solution should be 200 and 100 ppm, respectively.
Effects of Nitrogen Nutrition on the Growth, Yield, and Reflectance Characteristics of Corn Canopies1
Authors: Walburg G. , Bauer M. E. , Daughtry C. S. T. , Housley T. L.
Published: July 2010

Remote sensing offers the potential to determine rapidly the physiological condition of crops over large areas. To realize this potential, information is needed on the seasonal reflectance patterns of healthy and stressed crop canopies. A field experiment was conducted in which spectral and agronomic measurements were collected from corn (Zea mays L.) canopies grown under four N treatment levels (0, 67, 134, and 202 kg/ha) on a Raub silt loam (Aquic Argiudoll) soil. Data were collected at the Purdue Agronomy Farm, West Lafayette, Ind., on 11 dates during 1978 and 12 dates during 1979. Reflected radiation of 0.4 to 2.4 µm wavelength was measured with an Exotech 20C spectroradiometer and used to compute a reflectance factor. Agronomic data collected coincidently included biomass, leaf area index, plant height, crop development stage, percent soil cover, and surface soil moisture percent. Data were analyzed to determine: 1) the relationship between the spectral and agronomic characteristics of the canopies and 2) the spectral differences and separability of the four treatments.

Nitrogen treatment effects were seen across the entire wavelength interval measured. Red reflectance was increased and near infrared reflectance was decreased from N‐deprived canopies. Spectral differences between treatments were seen throughout each growing season. The near infraredred reflectance ratio (0.76 to 0.90 µm)/(0.63 to 0.69 pm) differed more between treatments than single band reflectance measures. Variations in canopy reflectance due to wetting and drying of soils were reduced by the use of the near infrared/red reflectance ratio.

The spectra of the four N treatments were significantly different (Duncan's multiple range test, P = 0.05) on August dates. Early and late in the season only two spectral classes were resolved. Of the spectral variables examined, the near infraredhed reflectance ratio most effectively separated the treatments. Discrimination results for both years were similar in spite of larger treatment differences in 1979 than in 1978. Differences in spectral response between treatments were attributable to varying soil cover, leaf area index, and leaf pigmentation values, all of which changed with N treatment. The results further confirm the potential of remote sensing for monitoring the growth and development of crops.
Growth and N Fixation of Some Tropical Forage Legumes as Influenced by Solar Radiation Regimes1
Authors: Eriksen F. I. , Whitney A. S.
Published: July 2010

Decreased solar radiation due to cloud cover or shading by plantation crops or associated grass can severely limit the production of tropical forage legumes. We therefore evaluated the response of six legumes (three replicated and three not replicated) to four radiation regimes (100, 70,45, and 27% of unshaded solar radiation, hereafter termed “full sun”) with polypropylene netting in the field.

The three replicated legumes had significant yield reductions at 27% full sun, with intermediate reductions at 70 and 45%. Dry matter (DM) yields at full sun [metric tons (mt) ha,−1yr−1 and proportional yields at 27%] were: Desmodium intortum cv. Greenleaf (20.0, 46%); Centrosema pubescens ‘centro’ (13.7, 44%); and Macroptilium atropurpureum cv. Siratro (12.9, 20%). Greenleaf was relatively tolerantof moderate shading; proportional yields at 70 and 45% of full sun were 93 and 75%, respectively. Centro and Siratro yields declined linearly as shortwave radiation (hereafter termed “radiation”) decreased, but Siratro yields declined significantly more than centro. Marked seasonal differences were noted in the response of the legumes to shade, and this was attributed to differences in the ability of the legumes to utilize solar radiation during periods of cool temperatures. The three non‐replicated legumes were evaluated similarly, except that yields were adjusted for replication effects. Dry matter yields and proportional yields at 27% full sun were: Leucaena Ieucocephala cv. Hawaiian Giant (23.5, 40%); Stylosanthes guianensis cv. Schofield (17.0, 17%); and Desmodium canum ‘kaimi clover’ (12.2, 32%). Hawaiian Giant and Greenleaf yielded similarly at 45 and 27% full sun. Kaimi clover DM yield tended to be slightly higher (13.8) at 70% full sun, but thereafter yields declined linearly with reduced radiation. Schofield stylo was the most sensitive to shading.

Dry matter and N concentrations were not significantly elevated by reduced radiation or cool weather except that N increased during the cool season. Concentrations of N differed among species being highest for centro and Hawaiian Giant (3.4%) and lowest for kaimi clover (2.6%). Total N yields were associated with DM yields. Nitrogen yields (kg N ha−1yr−1) of replicated legumes at full sun and proportional yields at 27% full sun were: Greenleaf (540, 45%), centro (461,44%), and Siratro (362,27%); and for the non‐replicated legumes, Hawaiian Giant (751,38%), Schofield (496, 18%), and kaimi clover [340 (361 at 70% full sun), 38%]. Acetylene reduction rates by nodules in soil cores were highly correlated with radiation regimes (r = 0.92‐0.995; except for centro, r = 0.71.) Correlation of acetylene reduction rates with DM yields ranged from 0.80 to 0.996.

The higher yielding legumes, Greenleaf, centro, and Hawaiian Giant (plus kaimi clover for ≈70 % full sun only) appear well‐suited for areas of low solar radiation because they have relatively constant concentrations of DM and N and fixed significant quantities of N even under dense shade.
Effects of Cultural Practices on Agronomic and Reflectance Characteristics of Soybean Canopies1
Authors: Kollenkark J. C. , Daughtry C. S. T. , Bauer M. E. , Housley T. L.
Published: July 2010

Understanding the relationship between the reflectance measured and the various cultural practices used in today's soybean production is key for further development and use of remote sensing as a tool for crop monitoring. Field experiments were conducted at the Purdue Agronomy Farm in West Lafayette, Ind. in 1978 and 1979 to study the reflectance factor (RF) of soybean (Glycine max L. Merr.) canopies as affected by differences in row width, population, planting date, cultivar, and soil type (Typic Argiaquoll and Typic Hapludulf). Reflectance factor (RF) data were acquired with a Landsat‐band radiometer (Exotech 100), which is a four band radiometer with a 15‐degree field of view that measures radiance in the following wavelength regions: 0.5–0.6, 0.6–0.7, 0.7–0.8, and 0.8–1.1 µm. Agronomic measurements included plant height, leaf area index, development stage, total fresh and dry biomass, and percent soil cover.

Row width, planting date, and cultivar influenced the percent soil cover, leaf area index, biomass, and development stage of the soybean canopies. Changes in these agronomic variables were manifested in the canopy reflectance. Soil color and moisture were important factors influencing RF in single Landsat bands; however, the near infrared/ red reflectance ratio and the greenness transformation were less sensitive than the single bands to changes in soil background. Variations in spectral responses are strongly associated with planting date during early to mid‐season, with the row width during mid‐season to near maturity, and with cultivar at maturity. This information should be useful in applications of remote sensing for identifying crops and estimating crop condition and yields.
Soybean Response to Different Planting Patterns and Dates1,3
Authors: Beatty K. D. , Eldridge I. L. , Simpson A. M.
Published: July 2010

Soybean [Glycine max (L.) Merr.] response to narrow rows (less than 50 cm apart) has been inconsistent in the southern United States. However, a more positive response has been documented in the North Central USA. Lack of suitable herbicides for controlling weeds in narrow row soybeans in the South has slowed acceptance of this practice. Development of more effective herbicides has made narrow row soybean production feasible.

Earlier planting dates can take advantage of favorable soil moisture conditions. Soybean plantings following wheat [Triticitm aestivum (L.) em. Thell.] harvest often do not close the crop canopy between rows before flowering when planted in rows 92 cm or more apart. Experiments were conducted in 1978 and 1979 (Vertic Haplaquept soils) to determine the effects of row spacings, broadcast seeding, planting dates, and soybean cultivars on yield and other plant characters.

Seed yield was affected by row spacing or methods, planting dates, years, and planting dates x years. Cultivars and the cultivar x planting method interaction were not significant for yield but none of the cultivars used in the study had been selected for narrow row conditions. The 18 and 48 cm row widths produced 15% higher seed yields than the conventional 96 cm row spacing. Mean yields across row spacings (including broadcast planting) and cultivars for the 15 July planting date were less than 50% of the April or May plantings. The cultivar x planting date interaction was large for percent seed protein because the late planted Forrest cultivar was significantly lower in percent protein compared to earlier planted Forrest. Pods per plant were significantly associated with yield in 1979 but not in 1978.
Simazine Formulation Treatments on Control of Winter Weeds in Bermudagrass Turf1
Authors: Johnson B. J.
Published: July 2010

Expanding choices of herbicides for consistent control of winter annual weeds are needed in turfgrass throughout the Southeast. Therefore, an experiment was conducted on Cecil sandy loam (Typic Hapludult) to determine effects of formulations, rates, and dates of simazine [2‐chloro‐4, 6‐bis(ethylamino)‐s‐triazine] treatments for the control of winter annual weeds in bermudagrass [Cynodon dactylon (L.) Pers.] turf.

The most consistent control of winter weeds from preemergence treatments applied in September occurred from the 1.8 and 2.2 kg/ha granule rates and 2.2 kg/ha wettable powder treatment. Slurry treatments applied in September did not effectively control parsleypiert (Alchemilla microcarpa Boissier Reuter) or corn speedwell (Veronica arvensis L.). Postemergence February treatments generally controlled parsley‐piert, corn speedwell, hopclover (Trifolium agrarium L.), and annual bluegrass (Poa annua L.) effectively (80% or higher) regardless of rates and formulations. An exception occurred with granular formulation for hop clover as the control from the 0.9 kg/ha rate was not as good as when treated with other formulations at the same rate. February granular treatments did not satisfactorily control spur weed (Soliva spp), whereas, at least 70% of weeds were controlled with 1.8 kg/ha or higher rates of wettable powder and slurry treatments. However, spur weed control was improved significantly from repeated September and February treatments when compared with single treatments at selected rates. None of the simazine treatments delayed early growth of bermudagrass in the spring regardless of formulation, rates, or dates of treatment.
Nitrogen Source Effect on Nitrate and Ammonium Leaching and Runoff Losses from Greens1
Authors: Brown K. W. , Thomas J. C. , Duble R. L.
Published: July 2010

The use of sandy rooting media with rapid infiltration rates in the construction of golf greens provides the potential for N pollution of nearby water supplies. This study was designed to measure the effects of different N sources on NO−3 and NH+4 concentrations in leachate and runoff from golf greens constructed with various rooting media.

Individual golf greens with USGA‐type profiles were constructed in the field with upper 30 cm layers consisting of sand‐peat, sandsoil‐peat and sandy loam soil mixtures. All profiles were equipped with subsurface tile drains over a plastic sheet and were treated sequentially with the following N fertilizers: NH4NO4, ureaformaldehyde, 12‐12‐12, Milorganite, and IBDU. Leachate and runoff were collected and analyzed for NO−3 and NH+4. Nitrate concentrations in leachate from sand, mixed, and soil greens fertilized with quick release materials ranged from 45 to 326, 8 to 314 and 8 to 170 mg liter−1, respectively and remained in this range for a 3‐week period. Runoff concentrations from the greens constructed of sandy loam soil exceeded 30 mg liter−1. No runoff was collected from sand or mixed greens.

Nitrate N losses from various sources were in the order of NH4NO3 > 12‐12‐12 > Milorganite > Isobutylenediurea (IBDU) > Ureaformaldehyde. lsobutylenediurea provided a very uniform release rate. Milorganite had a 25 to 30 day delay before NO−3 appeared in the leachate. Soluble sources, NH4NO3, and 12‐12‐12 exhibited leaching within 5 days after application. It appears that regular moderate applications of slow release N sources would provide minimum NO−3 loss while supplying a continuous N supply.

Ammonium losses ranked from greatest to smallest were NH4NO3 > Ureaformaldehyde > Milorganite > 12‐12‐12 > IBDU. Ammonium losses contributed very little to the total N losses from golf greens. Highest total N loss was 23% of the applied N.
Effects of Nitrogen Fertilization and Recurrent Selection on Performance of Hybrid Populations of Corn1
Authors: Kamprath E. J. , Moll R. H. , Rodriguez N.
Published: July 2010

Improved corn (Zea mays L.) hybrids are generally developed at relatively high N fertility levels. Previous studies have shown that hybrid populations developed by different selection methods vary in their responsiveness to environments. Because N supply is an important factor of the environment which affects yield a field study was conducted to determine the N response of population hybrids improved by intra (full‐sib family) and inter (reciprocal recurrent) selection methods. The responses of the original population hybrid and the two improved population hybrids to N rates of 56, 168, and 280 kg N/ha were studied on an Aquic Paleudult.

The improved populations produced more total dry matter and grain at each N level than did the original hybrid. This was associated with an increase in the ear number per plant as the N rate increased. The N concentration of the improved population hybrids at silking was correlated with ear number per plant. Average N use efficiency (grain per unit of N applied) for the improved population hybrids was greater than for the original hybrid. The higher yield of the reciprocal recurrent selection at 56 and 168 kg N/ha as compared with the full‐sib family selection was associated with a higher average N uptake efficiency.
Fifty Years of Minnesota Corn Production: Sources of Yield Increase1
Authors: Cardwell V. B.
Published: July 2010

Corn (Zea mays L.) yields in Minnesota have increased from the 2,010 kg/ha yield level of the pre‐1930's to the current 6,290 kg/ha average. This increased yield can he attributed to a series of technological, cultural, and management practices adopted by farmers. My objective is to atlempt an analysis of the magnitude of the changes and the relative contributions to grain yield each practice has made over the 50‐year time period. Only simple linear responses were estimated. No attempt has been made to evaluate the nature nor the magnitude of the interactions among the various management practices.

The change from open‐pollinated to hybrid corn combined with the estimated 36.5 kg/ha/year genetic gain has produced 58% of the yield increase. Although each kilogram of applied commercial N has been estimated to increase yields by 18.9 kg of grain per kg for 47% of the gain in yield, the effects of less manure, and reduced N from mineralized organic matter actually produces a net N effect of 19%. Improved weed control by the use of herbicides on 93% of the hectarage has increased yields 23%.

Plant densities have increased by 19,130 plantdha contributing 47.4 kg/ha/1,000 plants for a total of 21% of the gain. Better soil drainage, fall plowing, and herbicides have permitted planting 10 days earlier for an average gain of 36.4 kg/ha/day and a total of 8% of the net increase. Drilling corn rather than hill dropping has contributed 8% and fall plowing has contributed 5% to current yields. Row spacing has decreased from 107 to 90 cm for a gain of 10.2 kg/ha/cm or 4% of the gain.

Rotation changes have had no net effect on N balance with increases in soybean [Glycine max (L.) Merr.] offsetting decreases in forage legume hectarage. However, there has been a negative effect of more hectares of corn following corn resulting in 3% loss from corn rootworm (Diabrotica spp.) and 7% loss due to the interference effect of corn following corn. Corn borer (Ostrinia nubilalis Hubner) became a problem in the 1940's and has reduced yield potential an average of 5%. Soil erosion has reduced yield potentials 8% over the 50 years. Other negative and unaccounted factors reduce the potential yields by 23%.
Nitrogen Mineralization in Soils Previously Amended with Organic Wastes1
Authors: Griffin G. F. , Laine A. F.
Published: July 2010

Long‐term aerobic incubations were conducted on soils previously amended with cow and poultry manure, sewage sludge, and mycelium to determine N mineralization potential (No) and N mineralization rate constant (k). Values for No were higher than those reported by other workers. The k values varied among soils sufficiently so that a single value could not be assumed for any one group of soils. Corn (Zea mays L.) was grown on five of the soils used in the incubation study. Soil moisture and soil temperature data from NoN0 and initial mineral N, estimates of N available to the crop. Yield and N uptake correlated well with the parameter No × k, but No alone proved to be a very poor predictor of yield or N uptake. K values, which can be estimated only from lengthy incubations, are required to obtain accurate estimates of N availability.
Perennial Ryegrass Growth, Water Use, and Soil Aeration Status under Soil Compaction1
Authors: O'Neil K. J. , Carrow R. N.
Published: July 2010

Soil compaction is a serious problem on recreational turfgrass sites because the altered soil physical properties can adversely affect plant growth and irrigation management. Soil compaction was examined in a greenhouse study for its effect on turfgrass growth, water use, and soil aeration using a Chase silt loam soil (fine, montmorillonitic, mesic, Aquic Arquidolls). Perennial ryegrass (Lolium perenne L. ’Derby’) was subjected to three compaction levels: 1) none—no compaction, 2) moderate—360 joules energy, and 3) heavy—720 joules energy. The soil was compacted by dropping a 11.5 kg weight from a height of 65 cm. When tensiometers (installed at a depth of 5 cm) read −0.65 bar, 5 cm of water was applied. Pots were 30.5 cm I.D. by 76.2 cm long PVC pipe with bottom drainage. Soil compaction increased bulk density; reduced aeration porosity, visual quality, and shoot density; altered root distribution; and reduced root density in the 10 to 25 cm soil zone. It had, however, slight effect on verdure and individual shoot weight. Total clip ping weights were reduced by 38 and 53% for the moderate and heavy compaction treatments, respectively. Clipping yield decreased immediately after compaction treatment, while root changes were not apparent until after 12 weeks. During the study, water use was reduced by 21 and 49% for the moderate and heavy compaction treatments, respectively. Water extraction from the 10 to 25 cm soil zone decreased from 69 to 27% of the total water extracted in the heavy compacted pots by the end of the study. With heavy compaction, oxygen diffusion rates (ODR) were below 20 × l0−8 g cm‐2 min‐1 for at least 53 hours after irrigation. The noncompacted soil achieved acceptable ODR within 5 hours. The combined effects of compaction reducing rooting, slowing shoot growth, and increasing moisture retention, caused the compacted soil to remain at a reduced aeration status longer than the noncompacted soil after irrigation.
Foliar Fertilization of Soybeans. I. Effect of Fertilizer Sources, Rates, and Frequency of Application1
Authors: Poole W. D. , Randall G. W. , Ham G. E.
Published: July 2010

Foliar applications of fertilizer NPKS to soybeans [Glycine max (L.) Merr.] during the podfill stages of growth have been shown to increase yields. However, results have been inconsistent and in some cases severe yield depressions have occurred. The purpose of this study was to evaluate NPKS sources, rates of application, and frequency of application along with micronutrients, a fungicide, and a growth regulator on soybean seed yield, seed weight, and seed composition over several soybean genotypes and experimental locations during a 3‐year period. In 16 cultivar‐location‐year trials, soybean seed yields were increased significantly by the foliar fertilizer treatments over the control only once. Generally, yields were decreased when urea‐ammonium nitrate solution (UAN) and ammonium polyphosphate (APP) were substituted for urea and K‐polyphosphate in the basic NPKS formulation (24 + 2.4 + 7.2 + 1.2 kg/ha N + P + K + S). A positive relationship between leaf injury and yield depression by the various materials was noted; especially when the materials were applied during midday rather than in the early morning or late afternoon hours. The inclusion of micronutrients, a fungicide (Benlate), a growth regulator (Regime 8), or commercially available liquid fertilizers did not increase yields significantly. Seed weights were generally decreased with many of the foliar fertilizers and with the growth regulator. Seed N percentage and protein were increased and seed oil percentage decreased with four applications of the base NPKS formulation. These data indicate that further basic research is needed before the practice of foliar fertilization can be recommended.
Root Distribution and Water Use Efficiency of Alfalfa as Influenced by Depth of Irrigation1
Authors: Jodari‐Karimi Farman , Watson Vance , Hodges Harry , Whisler Frank
Published: July 2010

Root distribution of several crop plants is known to be affected by different patterns of soil moisture. In alfalfa (Medicago sativa L.), however, such results have not been consistently obtained under field conditions. Our objective was to determine the effect of different irrigation depths on alfalfa water use efficiency, water extraction patterns, and root distribution under greenhouse conditions where examination of the entire root systems was possible. ‘Cimmaron’ alfalfa was planted in polyvinylchloride (PVC) containers (120 ✕ 30 cm) filled uniformly with a Leeper fine (fine, montmorillonitic, nonacid, thermic Vertic Haplaquept) sandy loam top soil. Irrigation treatments included: watering to saturate the soil one‐third of the whole root depth, watering to saturate the soil two‐thirds of the whole root depth, and no irrigation. Irrigation was applied when available soil moisture content within the root zone reached 35 % (−2.5 bars soil matric potential). The parameters studied included root distribution pattern, total root growth, water extraction pattern, and water use efficiency. The efficiency of water use was higher in deeply irrigated treatments than in shallow irrigated treatments during June and July (a period of high evapotranspirational demand), but it was not different during September to November. Depth of irrigation did not affect total root production, but it did affect root distribution at the irrigation zone. Deeply irrigated plants produced slightly more roots in the lower depths than shallow irrigated plants. Root production of nonirrigated alfalfa was low under the high evaporational demand conditions which occurred during June and July, but was highest among all treatments during the September to November growing period. Root:shoot ratios of 0.28, 0.22, and 0.62 observed in shallow, deep, and non‐irrigated plants grown in the September to November period, respectively, indicate that the rate of root growth was increased in nonirrigated alfalfa as a result of limited water stress and under low evapotranspirational demand.
Resistances to Evapotranspiration from a St. Augustinegrass Turf Canopy1
Authors: Johns D. , Beard J. B. , van Bavel C. H. M.
Published: July 2010

A controlled environment study of evapotranspiration from St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] turf showed that, under adequately watered conditions, evapotranspiration was influenced to a greater extent by environmental factors which were external to the plants rather than by disposition of leaf stomata. Using an Ohm's Law analogue to define a resistance network for the turfgrass canopy, magnitudes of resistances to water loss were measured and compared. Internal resistance was defined as aggregate diffusive resistance of the foliage and was determined from porometer measurements of diffusive resistance of leaves. External resistance was defined as the sum of aerodynamic resistance and resistance to air mass exchange within the canopy and was measured by three different methods. Internal resistance was found to be only one‐fourth to one‐half the external resistance. Under wind speed conditions of 0.6 m/sec, actual evapotranspiration rates of St. Augustinegrass were only slightly lower than potential evapotranspiration rates. It is concluded that chemical or genetic control of stomatal resistance would not result in appreciable savings of irrigation water.
Evaluation of the Need for Copper with Several Soil Extractants1
Authors: Makarim A. K. , Cox F. R.
Published: July 2010

Copper deficiencies have been observed in a number of crops grown on both organic and mineral soils in the Atlantic Coastal Plain. In order to recommend fertilization correctly, soil test calibrations are needed for the extractants used in the region. Soybeans (Glycine max), corn (Zea mays), and wheat (Triticum aestivum) were grown in the greenhouse on 15 soils fertilized with Cu at several rates. Percent maximum yield for the plant growth on each untreated soil was calculated from the dry matter produced. Four soil extractants were used: Double acid (DA); Mehlich‐Bowling (MB); Ammonium bicarbonate‐DTPA (AB); and Mehlich‐3 (M3). Percent maximum yield was expressed as a function of Cu released from the untreated soils by each extractant with a linear plateau model. The extractants performed similarly in explaining plant response, with each accounting for about 70% of the variation. The soil critical levels, determined by the junction of the response and the plateau portions of the surface, for DA, MB, AB, and M3 were similar among crops and averaged 0.26, 0.62, 0.53, and 0.37 mg L−1 Cu, respectively. Wheat and soybeans were also grown in the field on seven soils with two rates of Cu. Grain yields of the two crops were related to MB extractable Cu with the Cate‐Nelson method, which indicated a critical level of 0.70 mg L−1. Critical whole plant and leaf Cu concentrations were also determined. The critical whole plant Cu concentrations for soybeans, corn, and wheat, each grown 5 weeks in the greenhouse, were 3.8, 1.8, and 3.8 mg kg−1, respectively. Deficiency symptoms developed on corn and wheat at slightly lower values, 1.5 and 2.9 mg kg−1, respectively. In the field, the critical leaf concentrations at early flowering were 6 mg kg−1 for soybeans and 4 mg kg−1 for wheat.
Leaf Pubescence Effects on the Mass and Energy Exchange Between Soybean Canopies and the Atmosphere1
Authors: Baldocchi D. D. , Verma S. B. , Rosenberg N. J. , Blad B. L. , Garay A. , Specht J. E.
Published: July 2010

Mass and energy exchanges with the atmosphere were compared in two soybean (Glycine max L. Merr. cv. Harosoy) isolines differing in pubescence density. The study was conducted in a field with a Sharpsburg silty clay loam soil (fine, montmorillonitic, mesic Typic Argiudoll) during the summer of 1980 at Mead, Nehr. Mass and energy exchanges were determined by means of micrometeorological techniques. Evapotranspiration (reported in terms of latent heat flux) was reduced in the densely pubescent isoline. Canopy CO2 exchange was unchanged on a per unit land area basis. Water use efficiency (reported in terms of the CO2‐water flux ratio) was, accordingly, greater in the densely pubescent isoline. The increase in pubescence did not significantly alter the net radiation balance, turbulent mixing, canopy CO2 exchange, or plant water status. Observed differences in the partitioning of net radiation into latent and sensible heat can be explained by greater penetration of solar radiation into the densely pubescent canopy. Leaf pubescence appears to alter the spectral characteristics of the leaf and, thus, to facilitate the penetration of solar radiation into the canopy.
Seed Yield of Kentucky Bluegrass as Affected by Post‐Harvest Residue Removal1
Authors: Ensign R. D. , Hickey V. G. , Bernardo M. D.
Published: July 2010

Field burning of post‐harvest residue has been an established management practice for economical production of Kentucky bluegrass (Poa pratensis L.) seed. Fields not burned soon after harvest usually have poor seed production in the following year. Residue remaining on fields shades, and thereby restricts tiller growth and subsequent seed yield. To explore the hypothesis, polyethylene shade screens which excluded 30 and 67% of sunlight were placed over September field‐burned ‘Baron’ Kentucky bluegrass plants for 75 and 130 days. Other treatments included mechanical vacuum clipping at 2.5, 7.6, and 15.2 cm levels, field burning of residue and no residue removal. The grass was seeded on Thatuna and Naff silt loam series (fine‐silty, mixed, mesic Xeric Argialbolls and fine‐silty, mixed, mesic Ultic Argixerolls, respectively). Tiller numbers from plants where residue was removed to the 2.5, 7.6, and 15.2 cm levels in 1978‐1979 were comparable to tiller numbers from plants shaded at the 30% level. Tiller numbers for plants shaded at 67% were comparable to tiller numbers where residue was removed at 15.2 cm, or where no residue was removed. Leaf and sheath length were generally inversely related to the level of residue removal. Panicle numbers for shading at 67% in 1979‐1980 were comparable to residue removal at 15.2 cm and no removal of residue. Seed yields from artificially shaded plants in 1978‐1979 were 51 to 55% less than yields from plants where residue was not removed. In 1979‐1980, seed yields from shaded plants at the 67% light exclusion for 130 days were 76% of yields from plants of open‐field burn but did not differ from yields from plants where residue was not removed or mechanically clipped to heights of 7.6 or 15.2 cm. It was concluded that reduced Light penetration into the canopy could change plant growth and reduce seed production potential.
Fall Harvest Management of Alfalfa in the Southern Plains1
Authors: Sholar J. R. , Caddel J. L. , Stritzke J. F. , Berberet R. C.
Published: July 2010

Fall regrowth of alfalfa (Medicago sativa L.) frequently is harvested for hay in the southern plains. Possible detrimental effects of harvesting from mid‐September to late November have not been studied. The objective of this research was to determine the effects of fall cutting dates on root total nonstructural carbohydrate (TNC) concentrations, productivity, and stand persistence of semi‐dormant, dryland alfalfa in the southern plains. From 1978 to 1980, five fall cutting date treatments were imposed on a 4‐year‐old stand of ‘Kanza’ and 2‐year‐old stands of ‘Arc’ and ‘Liberty’ alfalfas grown under dryland conditions on a fine, mixed thermic, Pachic Arguistolls (McClain silt loam). Three harvests per season were made at 10 to 25% bloom prior to the fall cutting date treatments which were made at fourth harvest of the season. Root carbohydrate analyses were made on roots dug 7 December of each year. Forage yields were taken during each growing season subsequent to fall cutting date treatments with a residual harvest taken in April 1981. Stand densities were determined at initiation of the study in 1978 and each fall thereafter. Final stand densities were determined in May 1981. Only forage yields were determined for Liberty. Fall cutting date treatments had little effect on root carbohydrate reserves. Roots dug in 1978 had higher TNC percentages than those dug in 1979 or 1980; however, fall cutting date treatments significantly influenced TNC concentrations only in the fall of 1979. Fall cutting date treatments had a greater effect on first harvest in the subsequent spring than on total yields. Total yields for each season and total yields over the duration of the study for each cultivar indicate that harvesting could take place at any fall date with little effect on productivity in subsequent years. Stands of all cultivars declined over the course of study and at the conclusion of the study in May, 1981 there were no differences in stand persistence that could be attributed to fall cutting date treatments.
Yield and Water Use Efficiency of Grain Sorghum in a Limited Irrigation‐Dryland Farming System1
Authors: Stewart B. A. , Musick J. T. , Dusek D. A.
Published: July 2010

A Limited Irrigation‐Dryland (LID) farming system for the conjunctive use of rainfall and limited irrigation of graded furrows was developed and field tested. The unique feature of the LID system is that it actually adjusts, during the crop growing season, the amount of land irrigated since more land can be irrigated during above‐average rainfall years with a limited amount of irrigation water than during below‐average years. The design used a limited water supply to irrigate a larger area than could be conventionally irrigated. A graded furrow field, 600 m long on a 0.3 to 0.4% slope was divided into three water management sections. The upper half of the field was managed as “fully irrigated.” The next one‐fourth was managed as a “tailwater runoff” section that utilized furrow runoff from the fully irrigated section. The lower one‐fourth was managed as a “dryland” section capable of utilizing runoff from either rainfall or irrigation on the wetter sections. The system was field tested for 3 years with grain sorghum (Sorghum bicolor (L.) Moench) on a Pullman clay loam (fine, mixed, thermic family of Torretic Paleustolls). Seasonal rainfall values were 224 mm in 1979, 103 mm in 1980, and 424 mm in 1981 as compared to the average of about 250 mm. The LID system was successful in increasing the utilization efficiency of irrigation water. Irrigation water added to a field can be transpired, evaporated, percolated, lost as runoff, or left stored in the soil after harvest. The LID system tended to reduce all losses other than transpiration. When 125 mm or 185 mm of irrigation water were added with the LID system, the evapotranspiration by grain sorghum was increased by an almost equal amount. This increased grain yield an average of 154 kg/ha for each 10 mm added irrigation, compared to 92 kg/ha for each 10 mm under conventional irrigation practices.
Nitrogen Use Efficiency of Trickle‐irrigated Tomatoes Receiving Continuous Injection of N1
Authors: Stark J. C. , Jarrell W. M. , Letey J. , Valoras N.
Published: July 2010

The practice of applying N fertilizer through trickle irrigation systems is rapidly increasing in popularity. Fertilizer N requirements are usually divided into small increments and then applied at regular intervals during the season. This field study, conducted on an Arlington loam (coarseloamy, mixed, thermic Haplic Durixeralf), was designed to investigate the uptake and partitioning of N by trickle‐irrigated tomatoes (Lycopersicum esculentum Mill.) and the potential for denitrification when N is continuously metered into the irrigation water. Solutions containing 1.8, 3.6, or 5.4 mol N m−3 were applied when the soil matric potential at the 25 cm depth reached either −10 or −30 kPa. The resulting N application totals ranged from 120 to 585 kg N ha−1. Early in the season, large differences in petiole NO3‐N concentrations were observed which appeared to be directly related to the rate of N supply. However, these differences gradually decreased as the season progressed. Total N uptake, which was linearly related to N application, was less than the amount applied at N rates greater than 300 kg ha−1. As the N application rate increased, an increasingly greater proportion of total plant N was partitioned into the vines. Denitrification N losses, as indicated by direct field measurements of N flux during a 4‐day period, were very small in the two lowest N treatments, ranging from 0.3 to 2.0 μg m−2 s−1. These low rates of denitrification were presumably due to competition between roots and denitrifiers. However, in the high N treatments, where N supply exceeded uptake, N fluxes ranged from 2.0 to 17.5 μg m−2 s−1. Aside from its influence on the rate of N supply, irrigation frequency had little effect on denitrification and N uptake. These results indicate that adequate N can be applied to tomatoes using high‐frequency N fertilization without large denitrification N losses.
Germination and Initial Growth of Kentucky Bluegrass in Soluble Salts1
Authors: Horst G. L. , Taylor R. M.
Published: July 2010

Kentucky bluegrass (Poa pratensis L.) has recently been considered for use as turf in high altitude regions of the arid Southwest where saline soils and saline irrigation water are a common problem. A laboratory experiment was conducted using saline hydroponic solutions with seeds of the bluegrass cultivars germinating and growing on floating mats. Solutions made from tap water consisted of 7500, 12 500, and 15 000 ppm NaCl and CaCl2 by weight, on an equal basis. Total germination, days to initial germination, leaf blade length, and blade fresh weight were measured. The objectives of this study were to determine the relative interspecific salt tolerances during germination and seedling growth of 44 bluegrass cultivars. Cultivars had highly significant germination and germination rate responses to salt stress. Seedling growth responses as measured by blade length and blade fresh weight were also significant. We found that a hydroponic growth medium containing 7500 ppm NaCl and CaCl2 salt would be suitable for identifying cultivars that have potential commercial value for saline growing conditions. At this salinity level, cultivars which average less than a 50% reduction in growth parameters relative to top yielding cultivars should be considered. A hydroponic medium with a salt concentration of 12 500 ppm would provide a suitable stress level for screening bluegrass genotypes for improved salt tolerance.

Broad‐sense heritability estimates indicate that blade length, germination percentage, and germination rate would be valuable selection criteria for use in screening Kentucky bluegrass cultivars for salt tolerance. Apomictic reproduction may limit genetic improvement from recurrent selection.
Osmoconditioning of Beet Seeds to Improve Emergence and Yield in Cold Soil1
Authors: Khan Anwar A. , Peck Nathan H. , Taylor Alan G. , Samimy Cyrus
Published: July 2010

Table beet (Beta vulgaris L.) seeds are characteristically slow germinating, and have a large time spread of germination. These characteristics interfere with the early establishment of a uniform, vigorous stand of seedlings in cold wet soil. This study was undertaken to determine if osmoconditioning (OC) of table beet seeds in polyethylene glycol 6000 (PEG) and MgSO4 solutions and/or other measures would improve germination and/or reduce germination time and thereby improve emergence, seedling establishment and yield. Seed balls of ‘Ruby Queen’ and ‘Cardenal’ were osmoconditioned in −1.2 and −1.18 MPa solutions of PEG and MgSO4, respectively. Treatments were performed at 15 °C for 7 days in the light. The benefits of OC were not lost by drying back the seeds. Aeration during OC followed by a 2 min rinse with water was the most effective treatment in improving germination or emergence in laboratory and growth chamber studies. In the 1980 field trial, OC in PEG improved the rate of emergence by 2 to 3 days, the stand by 40% and the root, top, and total yield by 40, 66, and 59%, respectively. In 1982, seedling emergence was biphasic. The first phase lasted 23 days and showed large differences in rate of emergence and stand between osmotically treated and untreated seeds and resembled the 1980 emergence pattern. The second phase commenced after a 30 mm rain with a resurgence of emergence in all treatments. The resurgence rate was highest in untreated seeds and this reduced the treatment differences in stand and yield. The resurgence was attributed to invigoration of the non‐germinated seed by low soil water potential (drought). Several MgSO4‐OC treatments increased the number of roots but decreased root size.
Turfgrass Evapotranspiration. I. Factors Influencing Rate in Urban Environments1
Authors: Feldhake C. M. , Danielson R. E. , Butler J. D.
Published: July 2010

Evapotranspiration (ET) by turfgrass in urban environments is site specific and can vary considerably from what would be predicted from regional climate. A large degree of heterogeniety exists in residential microclimate and lawn management practices. The relative importance of these factors needs evaluation to aid in planning for efficient use of municipal water, half of which is applied to lawns in some western areas. This study, using small lysimeters, evaluated the relative effects of mowing height, N fertility, shading, grass species, and soil composition on ET. Kentucky bluegrass (Poa pratensis L. var. ‘Merion’) mowed 5 cm used 15% more water than grass mowed at 2 cm. Thirteen percent more water was used when 4 kg/1000m2 of N was applied each month during spring and summer compared to only one application for the season, applied in the spring. Evapotranspiration by grass in 1979 was essentially the same whether growing on a clay soil or on a sand‐peat mixture; however, a 6% decrease occurred for the soil system in 1980. Evapotranspiration increased linearly with solar radiation when an advective component of energy, accounting for 35% of ET, was subtracted from all solar treatments. Kentucky bluegrass and tall fescue (Festuca arundinacea Schreb. var. ‘Rebel’) which are cool‐season grasses, used over 20% more water than bermudagrass (Cynodon dactylon L. X Cynodon transvaalensis Davy var. ‘Tifway’) and buffalograss (Buchloe dactyloides Nutt) which are warm‐season grasses.