bluuebunny/crossref_metadata_2025 huggingface dataset:
Cutting Interval and Irrigation Timing in Alfalfa: Yellow Foxtail Invasion and Economic Analysis
Authors: Norris Robert F. , Ayres Debra
Published: July 2010

Yellow foxtail (Setaria glauca (L.) Beauv.) is the most serious summer annual weed in alfalfa (Medicago sativa L.) in the Central Valley of California. The experiment evaluated the importance of cutting interval and timing of irrigation on invasion of the weed into established alfalfa. The crop was cut on a 25‐, 31‐ or 37‐d interval. Irrigation was applied on the same day as cutting or after a delay of 7 or 14 d. A factorial treatment combination was used in a randomized complete block fielld design. The experiment was continued for 3 yr. Alfalfa yield increased with increased length of cutting interval but was not affected by irrigation regime. Yellow foxtail invasion was minimal at the 37‐d cutting interval, was intermediate at the 31‐d interval, and reached 20 to 30% of late‐season harvests at the 25‐d cutting interval. Delaying irrigation following cutting reduced yellow foxtail invasion 2 yr out of three; this effect was largest for hay cut on the 31‐d interval. Cash‐flow economic analyses showed that cutting at a 25‐d interval resulted in the lowest net return due to low overall yield and substantial yellow foxtail invasion late in the season. Hay cut at the 31‐d cutting interval would provide the highest net return. Reduced alfalfa quality compromised the return for the 37‐d cutting interval. Yellow foxtail can be controlled in alfalfa by manipulation of cutting interval.
Border Effects on Nitrogen‐15 Fertilized Winter Wheat Microplots Grown in the Great Plains
Authors: Follett R. F. , Porter L. K. , Halvorson A. D.
Published: July 2010

Field experiments requiring 15N enriched fertilizer are costly, thus microplot techniques are generally used. Placing physical barriers around microplots to contain the 15N may introduce artifacts that affect N recovery by crops, limit types and numbers of measurements, and cause other restrictions. The purpose of this experiment was to determine minimum microplot size (without the use of barriers) for accurately measuring enriched 15N uptake into a winter wheat crop, while using normal field cultural practices. Winter wheat (Triticum aestivum L.) was seeded into KNO3 fertilized (56 and 112 kg N ha−1) plots (4.57 m by 3.05 m) on a Platner silt loam soil (fine montmorillonitic mesic Aridic Paleustol). Within each larger plot, four microplots (2.29 m by 1.83 m) were fertilized with 10 atom % 15N enriched KNO3 at the same rate as for main plots. Nitrogen‐rate treatments were replicated four times in a randomized block design. Above ground plant material was harvested (0.3 m of row) from six adjacent rows at flowering (Feeke's scale = 10.5). Three rows were harvested from inside (15N enriched KNO3 added) and three from outside (15N enriched KNO3 not added) of the microplots. Plant uptake of total N into plant tops was not significantly different across any of the six harvested rows. Dry matter yields and total‐N uptake were significantly larger for the 112 than for the 56 kg N ha−1 fertilizer rate, as were the 15N uptake and atom 15N % values in plant material within the microplots. In rows adjacent to microplot borders, concentrations of 15N in plant material changed rapidly; but there were no differences beyond 0.46 m inside or outside the microplots. These results indicate that minimum microplot size for studies with fall‐applied 15N on winter wheat grown in the Great Plains is 1.5 by 1.5 m.
Calcium Stimulation of Ammonium Absorption in Onion
Authors: Fenn L B. , Taylor R. M. , Binzel M. L. , Burks C. M.
Published: July 2010

The inefficiency of N use in soils has been studied widely, producing varied suggestions for increased effectiveness. The object of this research was to examine the use of Ca2+ as a means to increase NH+4 absorption, using onion (Allium cepa L.) as a test crop. Ammonium absorption in the presence of variable Ca2+ concentrations was measured in short‐term greenhouse studies as well as longterm greenhouse studies and field‐production trials. The greenhouse 15NH+4 absorption study was conducted in 4‐L pots containing 3.5 kg of calcareous Gila sandy loam (coarse‐loamy, mixed, calcareous, thermic Typic Torrifluvents). The long‐term growth study was conducted in calcareous quartz sand. Irrigation solutions consisted of half‐strength nutrient solutions (5 mol m−3 in NH+4) with Ca2+:NH+4 molar proportions of 0, 0.25, 0.50, 1.00, and 2.00. The 15NH+4 absorption study was conducted during a 30‐h period on 60‐d onion. The long‐term growth experiment received the same nutrient solutions until mature onion bulbs were produced (about 5 cm in diameter). A 2‐yr field production trial used single rows on 1‐m wide beds. The soil was a calcareous Saneli silty clay loam [clayey over sandy or sandy‐skeletal, montmorillonitic (calcareous), thermic Vertic Torrifluvent]. In 15NH+4 studies, NH+4 absorption increased with added Ca by as much as 189% in onion bulbs and by 67% in onion tops relative to absorption with no Ca added. These maximum increases were in association with solution Ca2+:NH+4 molar proportions (MP) of 0.5 in onion bulbs and 1.0 in onion tops. Total plant dry weights with Ca added increased as much as 100% in bulbs and 25% in tops in 30‐h 15NH+4 absorption tests over the 0 Ca2+ controls. In greenhouse growth tests, vegetative matter increased as much as 40% with increasing Ca2+ concentrations at constant NH+4 levels compared to the 0 Ca2+ control. This translated to increased total N absorption. In 2 yr of field testing with a MP of 0.25, mature bulbs from both years increased 64% over yields with urea alone. Thus the addition of Ca2+ with urea produced significantly improved plant N‐use efficiencies (greater plant yield at the same level of N application). These results were suggested from both the short‐term greenhouse 15NH+4 absorption experiment and from the long‐term greenhouse growth trial.
SOYHERB‐A Computer Program for Soybean Herbicide Decision Making
Authors: Renner K. A. , Black J. R.
Published: July 2010

There has been a rapid increase in the number of herbicides and herbicide mixtures registered for use in soybean [Glycine max (L.) Merr.] production. SOYHERB is a computer program developed to assist Cooperative Extension Service personnel, agribusiness, farmers, and teachers in determining herbicide options for soybean production. Tillage practices, atrazine (6‐chloro‐N‐ethyl‐N'‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine) or simazine (6‐chloro‐N,N'diethyl‐1,3,5‐triazine‐2,4‐diamine) use in a previous corn crop, soil type and percentage of organic matter, soil pH, projected crop rotation plans, method of herbicide application, and weed species and weed pressure are entered by the user. SOYHERB generates herbicide programs and their cost per acre that provide excellent control of all weed species at the weed pressures indicated. Fair (80–90%) weed control options may also be generated. Additional screens describe control of perennial weeds, a summary of herbicide premixes, and a table listing the maximum height of broadleaf weeds controlled by postemergence herbicides. Data can be saved for future reference. A computer capable of running MS‐DOS or PC‐DOS version 2.1 or greater with a minimum of 512K bytes of RAM is required.
Computing Transpiration of Sunlit and Shaded Cotton Foliage under Variable Water Stress
Authors: Petersen K.L. , Fuchs M. , Moreshet S. , Cohen Y. , Sinoquet H.
Published: July 2010

The accurate calculation of transpiration from plant canopies is critical in order to judiciously manage limited water resources in many agricultural areas. The objective of this study was to compute transpiration from the sunlit and shaded fractions of a cotton (Gossypium hirsutum, cv, Acala SJ2) canopy using the Penman‐Monteith energy balance equation. These computations were validated by a heat pulse system measuring stem sap flow, and by measuring the crop surface energy balance by the Bowen ratio method during two field seasons in 1988 and 1989. Adjusting the relationship between absorbed radiation and leaf conductance for decreasing leaf water potential sensitized the Penman‐Monteith energy balance computation to variable water stress conditions. Results showed that the computed transpiration of the shaded canopy comprised 0.21, 0.28, and 0.33 of the total during severe water stress in normal atmospheric demand, non‐stress in normal atmospheric demand, and non‐stress in very high atmospheric demand, respectively. The average daily computed transpiration for the two seasons was within 5% of that measured by the heat pulse system and the Bowen ratio. The hourly computation exhibited the expected sensitivity to fluctuations in atmospheric demand and to the change of available soil moisture. The linear regression of computed transpiration for measured water uptake by the heat pulse system yielded an R2 value of 0.96. Quadratic regression analyses during non‐stress and stress for computed hourly transpiration vs. evapotranspiration yielded R2 values of 0.97 and 0.92, respectively. These analyses show that midday evapotranspiration is systematically higher than computed transpiration, which would presumably be due to evaporation from the soil.
Fertilizer Management Effect on Recovery of Labeled Nitrogen by Continuous No‐Till
Authors: Timmons D. R. , Baker J. L.
Published: July 2010

Improved fertilizer N management with respect to placement and timing is especially important in high‐residue systems designed to improve N‐use efficiency and to speed adoption of erosion controlling tillage practices. By means of point‐injection technology, fertilizer solutions now can be applied and soil‐incorporated with minimal disturbance of surface residue or existing plants. This study was conducted in large non‐weighing lysimeters (with reconstituted soil horizons) to determine the recovery of 15N – labeled urea‐ammonium nitrate (UAN) solution by continuous no‐till corn (Zea mays L.) during the initial year of application and two subsequent years for four N management systems. The UAN solution was point‐injected in split applications at rates of 125 or 200 kg N ha−1, or knifed‐in or surface‐banded right after plant emergence at 200 kg N ha−1. For the initial year of 15N application, the percent recovery of labeled N (NR) in grain was 48, 39, 33, and 30% for point‐injected (low rate/split), point‐injected (high rate/split), knifed‐in, and surface‐banded, respectively. The percentage of total grain N derived from labeled N (Nf) ranged from 57 to 67% and was in the order of point‐injected (high rate/split) > knifedin > point‐injected (low rate/split) > surface‐banded. Residual labeled N recovery in grain ranged from 2.3 to 4.6% for the second season and from 0.9 to 1.0% for the third season with no significant differences among application treatments for either season. After five seasons the NR values for labeled N determined in the soil N pool still ranged from 20 to 26%. UAN solution applied in split applications with the point injector was used more efficiently by corn than when knifed‐in or surface‐banded in a single application, indicating the point‐injection/split application system is an option for improved N management in no‐till corn.
Crabgrass Control In Coastal Bermudagrass
Authors: Smith A. E. , Martin L. D.
Published: July 2010

Many hectares of ‘Coastal’ bennudagrass [Cynodon dactylon (L.) Pers.] stands are lost during the second growing season after planting because of competition from large crabgrass [Digitaria sanquinalis (L.) Scop]. Experiments were conducted in southern Georgia on a Cecil (thermic, Typic Hapludults) sandy clay loam and central Georgia on a Greenville (clayey, thermic, Rhodic Kandiudults) sandy loam soil to evaluate chemical treatments for managing large crabgrass in Coastal bermudagrass. Herbicide treatments were applied to Coastal bermudagrass stands during the second growing season after planting to evaluate crabgrass control and to fully established stands to determine treatment damage to the Coastal bermudagrass. Norflurazon {4‐chloro‐5 ‐ (methylamino)‐2‐[3 ‐ (trifluoromethyl)phenyl] ‐3(2H)‐pyridazinone} applied during March at rates of 1.12 and 2.24 kg ai ha−1 resulted in >80% control of large crabgrass up to 90 and 50 d after treatment, respectively. Treatments with norflurazon at rates as high as 2.24 kg ha−1 did not damage the Coastal bemudagrass stand or decrease yield compared to the untreated control. These data indicate that norflurazon would be an excellent candidate herbicide for use in the control of large crabgrass in Coastal bermudagrass pastures and hayfields.
Yield and Quality of Soybean Forage as Affected by Cultivar and Management Practices
Authors: Hintz Rodney W. , Albrecht K. A. , Oplinger E. S.
Published: July 2010

Soybean [Glycine max (L.) Merr.] has potential for use as an alternative forage crop, however, little is known about the effects of cultural practices on forage yield and quality. A study was conducted to evaluate the effects of cultivar, row spacing, plant density, and harvest maturity on the yield and quality of soybean forage. The study was conducted at the Univ. of Wisconsin Arlington Agricultural Research Station, Arlington, WI on a Plano silt‐loam soil (fine‐silty, mixed, mesic, Typic Argiudoll) in 1987 and 1989. The cultivars Corsoy 79, Pella, and Williams 82 were grown at 20‐ and 76‐cm row spacings at planting rates of 280 000 and 890 000 seeds ha−1 and were harvested at the R1, R3, R5, and R7 stages of development. Harvest maturity had the greatest effect on soybean forage yield and quality of the management practices evaluated. The yield of soybean forage increased from 2.4 Mg ha−1 when harvested at R1 to 7.4 Mg ha−1 when harvested at R7, but quality declined between stages R1 and R5 then increased from R5 to R7 as pods developed and seeds filled. Late maturing cultivars (Maturity Group III vs. Maturity Group II) produced greater forage yields but lower quality forage when harvested at the same stage of development. The 20‐cm row spacing produced 1.2 Mg ha−1 more forage than the 76‐cm row spacing, but crude protein concentration was 8 g kg−1 less. The results of this experiment indicate that soybean can produce forage similar in quality to alfalfa and that management practices typically used for grain production are suitable for forage production.
Soil Moisture Extraction by Vegetation in a Mediterranean/Maritime Climatic Regime
Authors: Borman M. M. , Johnson D. E. , Krueger W. C.
Published: July 2010

Timing and extent of soil moisture extraction are critical when evaluating perennial grasses for their adaptability to the climate and soils. We hypothesized that in the southwest Oregon foothills perennial grasses able to extract moisture early in the growing season should be more competitive with resident annual plants than those that utilize soil moisture later. Our objective was to assess the potential for competition of selected native and introduced perennial grasses with annual plants. The experiment consisted of growing perennial grasses with and without competition from the resident annual community and evaluating soil moisture throughout the growing season with a neutron probe. ‘Berber’ and ‘Palestine’ orchardgrasses (Dactylis glomerata L.) extracted moisture earlier than later growing ‘Oahe’ intermediate and ‘Alkar’ tall wheatgrasses (Agropyron intermedium [Host.] Beauv. and A. elongatum [Host.] Beauv., respectively). Soil moisture contents in plots of Idaho fescue (Festuca idahoensis Elmer), a native and the earliest growing and maturing perennial grass in the study, were not consistently lower than soil moisture contents in plots of later growing perennial grasses. End‐of‐season soil moisture contents were similar (P < 0.10) in perennial grass plots and plots dominated by yellow starthistle (Centaurea solstitialis L.). Resident annual grasses left approximately 50% more soil moisture than perennial grasses or annual forbs. In years with an early summer drought, earlier growing perennial grasses should be able to satisfy their growth requirements.
Analysis of Phytomass Yield in Wheat
Authors: Sharma R. C.
Published: July 2010

Grain yield (GRY) increases in wheat (Triticum aestivum L.) have been achieved through increases in harvest index (HI). Further improvements in HI appear difficult so further increases in GRY may have to come through increases in phytomass yield (PMY). Increases in PMY also should increase yield of nongrain plant parts (NGRY) which is important both for wheat pasture and for feeding straw to cattle in developing countries. A study was undertaken to examine variation for PMY in 20 genetically diverse wheat genotypes and to analyze GRY and NGRY constituents of PMY. Replicated field tests were conducted at Rampur, Nepal in 1989 and 1990 under two production systems. There were significant effects of year and production system on PMY, GRY, NGRY, and HI. Significant genotypic variations existed for PMY, GRY, NGRY, and HI. All genotypes produced higher PMY, GRY, and NGRY under high fertility production system than under low fertility production system. Genotype‐by‐production system interactions were significant for PMY, GRY, and NGRY and genotype‐by‐year interactions were significant for PMY, NGRY, and HI. High PMY usually resulted in high GRY and high NGRY which is desirable in developing countries where both GRY and NGRY determine the economic success of a cultivar. The presence of high positive correlations between PMY and GRY (r = 0.84, P < 0.01), PMY and NGRY (r = 0.94, P < 0.01), and an intermediate positive correlation between GRY and NGRY (r = 0.60, P < 0.01) suggested that these traits might be selected simultaneously for improvements.
Phenmedipham + Desmedipham Effects on Sugarbeet
Authors: Prodoehl K. A. , Campbell L. G. , Dexter A. G.
Published: July 2010

Phenmedipham + desmedipham [3‐methoxycarbonylaminophenyl‐3‐methylcarbanilate plus ethyl m‐hydroxycarbanilate carbanilate (ester)], is a herbicide which controls a number of broadleaf weeds in sugarbeet (Beta vulgaris L.) by inhibiting Photosystem II. This hericide also decreases the photosynthetic activity of sugarbeet. Field tests at Fargo, ND, in 1988, 1989, and 1990 determined the effect of phenmedipham + desmedipham on photosynthesis 1, 3, and 10 d after treatment (DAT); root yield; and sucrose concentration of six commercial sugarbeet cultivars. Photosynthesis was reduced 50 and 30% 1 DAT with high and low rates of phenmedipham + desmedipham, respectively, but recovered substantially 10 DAT to 75 and 85% of the untreated plots. Small reductions in root yield associated with phenmedipham + desmedipham rates were not significant. Sucrose concentration at harvest was not influenced by phenmedipham + desmedipham. No cultivar or group of cultivars was identified as having a unique response to phenmedipham + desmedipham.
Nodulation, Nitrogen Fixation, and Early Growth of Arrowleaf Clover in Response to Root Temperature and Starter Nitrogen
Authors: Schomberg H. H. , Weaver R. W.
Published: July 2010

Nitrogen availability is important for rapid establishment of small seeded legumes and is influenced by soil N status and rapid development of N2 fixation activity. Seedlings of arrowleaf clover (Trifolium vesiculosum L. Savi) are exposed to soil temperatures (10–35°C) during the fall which can reduce seedling vigor by influencing N nutrition. Root temperature (18, 25, or 32 °C) effects on N nutrition of arrowleaf clover receiving starter N was evaluated in two controlled experiments. Temperature influenced the N status of inoculated plants through an effect on N2 fixation but not on starter N uptake. Growth and N2 fixation were best at 25 °C where effectiveness of two strains of Rhizobium leguminosarum bv. trifolii was similar, but, at 32 °C, strain RP115‐2 was less effective than strain 162✕68. Addition of mineral N (0.5 and 1.0 mg N plant−1) improved growth and stimulated N2 fixation at 25 °C more than at 18 or 32 °C. Time required for nodulation was also influenced by N and temperature but was not different between the two strains of Rhizobium. Nodules were first visible 6.4 to 8 d following inoculation at 25°C, but required 8.0 to 11.3 d at 18 or 32°C with the longer period occurring for plants receiving 1.0 mg N plant−1. Growth of control plants receiving adequate mineral N showed little influence of the root temperature regimes. Root temperatures influenced early growth of arrowleaf clover through an effect on N2 fixation and root temperatures of 32 °C or greater were particularly detrimental because of combined effects of delayed nodulation and reduced N2 fixation activity.
Core Cultivation of a Putting Green with Hollow and Solid Tines
Authors: Murphy J. A. , Rieke P. E. , Erickson A. E.
Published: July 2010

Most turfgrass soil cultivation research has emphasized water infiltration and thatch responses, but has provided limited information regarding detailed soil and rooting responses to different cultivation methods. This study evaluated cultivation effects on soil physical properties and turf growth of a ‘Penneagle’ creeping bentgrass (Agrostis palustris Huds.) putting green. Cultivation, utilizing vertically operating hollow (HTC) or solid (STC) tines, was applied over a 3‐yr period on a loamy sand soil (modified fine‐loamy, mixed, mesic, Typic Hapludalfs). Cultivation treatments were applied on noncompacted and compacted plots, and at soil moisture potential ranges of −40 to −60 kPa (moist) or −2 to −4 kPa (wet). Saturated water conductivity and air porosity was 49 and 21% greater, respectively, with HTC than STC. After three seasons, wet soil cultivation reduced saturated hydraulic conductivity 31% compared to moist soil cultivation. Cultivation reduced penetration resistance 45% at the 5‐cm depth compared to noncultivated plots in compacted soil, but the benefit was transient particularly on STC plots. Hollow tine cultivation under wet soil conditions yielded the best turf quality. Surface root weight density was lowered 20% with cultivation on compacted soil by the end of the study. Hollow tine cultivation lowered the organic matter fraction of the thatch/mat layer 0.24 kg kg−1, but increased total organic matter content 150 g m−2 compared to solid tine cultivation. Solid tine cultivation provided short term benefits, required repeated application to be effective in management of soil compaction, and exhibited the potential for development of a cultivation pan.
Timing Nitrogen Applications for Corn in a Winter Legume Conservation‐Tillage System
Authors: Reeves D. W. , Wood C. W. , Touchton J. T.
Published: July 2010

Fertilizer N efficiency of corn (Zea mays L.) in conservation‐tillage systems with winter legumes such as crimson clover (Trifolium incarnatum L.) can possibly be improved by better synchronization of legume‐N release, fertilizer‐N application time, and crop demand for N. The objective of this 3‐yr (1986‐1988) field experiment was to determine the effect of N application time on dry matter accumulation, N uptake, and grain yield of corn grown in a winter legume conservation‐tillage system. Corn was planted with unit planters into crimson clover residue following in‐row subsoiling. The clover was killed at midbloom every year. Treatments were a factorial arrangement of fertilizer N rates and application time. Nitrogen as NH4NO3 was broadcast at rates of 34, 67, and 134 kg ha−1. Zero‐N checks were also included in both clover and rye (Secale cereal L.) plots. Application times were at planting, or 3, 6, or 9 wk later. In addition, split applications (1/3 at planting and the remainder 6 wk later) of the 67 and 134 kg N ha−1 rates were included. In 2 of 3 yr, dry matter accumulation was not affected by N application time. In 1987, however, dry matter production was greater when N was applied at planting compared to split applications or applications later than 3 wk after planting. Application time affected N uptake patterns during the growing season, but generally did not affect total N uptake at the end of the season. With the exception of the first year, split N applications resulted in equivalent or reduced N uptake compared to application of all N at planting. Based on linear regression models, maximum yield was obtained with 134, 116, and 93 kg N ha−1 in 1987, 1988, and 1989, respectively. After the first year, applying N later than 6 wk after planting reduced grain yield and split applications of N were not effective in increasing grain yield. These results suggest that the fertilizer N requirement of corn grown in winter legume conservationtillage systems on Coastal Plain soils decreases with successive years in the system and that the optimum management practice for conservation of N, energy, time, and labor would be to apply all fertilizer N at planting.
Mineral Concentrations in Forage Sorghum Grown under Two Harvest Management Systems
Authors: Kidambi S. P. , Matches A. G. , Karnezos T. P. , Keeling J. W.
Published: July 2010

Little information is available on the mineral concentrations of forage sorghum [Sorghum bicolor (L.) Moench] leaves and stems. Our objective was to determine whether commercially available forage sorghum could be expected to supply the minimum mineral requirements for beef cattle when harvested as simulated grazing of pastures (SP) or as hay. In 1987 and 1988, 10 forage sorghum entries were grown near Lubbock, TX, in replicated plantings on a fine, mixed thermic Aridic Paleustolls with supplemental furrow irrigation. There were three SP harvests in 1987 and four in 1988. The hay treatments were harvested twice in 1987 and three times in 1988. Entries and managements were different (P ≤ 0.05) in mineral concentrations, as was the management ✕ entry interaction for Mg, K, Na, Cu, and the K/(Ca + Mg) ratio. Generally, for both management systems, leaves had numerically higher concentrations of Ca, Mg, P, and Mn than stems, while the reverse was true for K, Na, and the K/(Ca + Mg) ratio. Copper and Zn concentrations were not consistent for either harvest schedule or leaves and stems. Minerals found most likely to be limiting for beef cattle (Bos taurus) were P and Zn, but P would generally be adequate if cattle had daily access to leafy growth. Calcium tended to be low and the K/(Ca + Mg) ratio high in stems of the hay harvests. The levels of the other minerals appeared to meet the minimum requirements for beef cattle for most of the growing season. Overall, the 10 entries of forage sorghum appeared similar in meeting mineral requirements of beef cattle.
Nitrogen Credits in Soybean‐Corn Crop Sequences on Three Soils
Authors: Bundy L. G. , Andraski T. W. , Wolkowski R. P.
Published: July 2010

Economic and environmental incentives to accurately predict corn (Zea mays L.) N requirements emphasize the need to assign appropriate N credits for soybean (Glycine max L.) in soybean‐corn crop sequences. This study was conducted to determine corn response to N and N credits for soybean in crop sequences. The effects of corn‐corn (CC), soybean‐corn (SbC), and soybean‐corn‐corn (SbCC) crop sequences and applied N (0 to 225 kg N ha−1) on corn grain yield, N uptake, and soil NO3 and NH4 concentrations were determined for 4 yr at three sites differing in climatic and soil characteristics. Four‐year mean yields in SbC were 1.4 and 2.2 Mg ha−1 higher than in CC at two sites with nonirrigated silt loam soils, but yield effects due to crop sequence were small on an irrigated sandy soil. Corn response to applied N varied markedly among the three sites and between years at the sites on silt loams soils. Mean corn N uptake in SbC was higher (51 kg N ha−1) than in CC on silt loam soils but not on the sandy soil. Soybean N credits estimated with a fertilizer replacement value (FRV) approach and from the difference in N rates at maximum yield in SbC and CC sequences (DNM) differed markedly among locations and years and ranged from − 22 to 210 kg N ha−1. Soybean provided little N to subsequent crops on sandy soils due to probable loss of residue N through leaching prior to use by the following crop. On silt loam soils, crop sequence effects on yield and N uptake indicate soybean N contributions to subsequent crops; however, fixed value N credits or N credits based on N response data combined over years will seldom accurately predict actual soybean N contributions. Site‐specific diagnostic tests are needed to improve crediting of N supplied by soybean in crop sequences.
Rice Ratoon Response to Main Crop Harvest Cutting Height
Authors: Jones David B.
Published: July 2010

Although main crop rice (Oryza sativa L.) cultural practices are known to influence the subsequent ratoon crop, little specific information is available on the effect of many main crop management practices on ratoon crop performance. The objective of this study was to evaluate the effect of main crop harvest cutting height on ratoon crop agronomic performance, yield, and yield components. The ratoons of both a semidwarf and non‐semidwarf southern U.S. long‐grain rice cultivars were evaluated in the field for two growing seasons for response to main crop harvest cutting height. Main crop plants were harvested at a cutting height of 0.1, 0.2, 0.3, 0.4, and 0.5 m above the soil surface. The semidwarf cultivar had 7 and 40% higher grain yields than the taller cultivar in the main and ratoon crops, respectively. Ratoon plant height and days to 50% heading were numerically different for the two cultivars, but the same in proportion to their main crop traits. Reduced cutting heights delayed ratoon maturity by up to 4 d, but had minimal effects on ratoon plant height. No interactions between cutting height, cultivar, and/or year were found for ratoon yield or yield components. Highest ratoon yields were obtained at cutting heights of 0.2 to 0.3 m. Increasing cutting heights had little effect on ratoon panicle number per meter squared, but significantly decreased filled grain number per panicle, which led to decreased ratoon yields at the highest two cutting heights. The results show that proper main crop harvest cutting height can increase ratoon yields, but selecting a cultivar with inherent ratooning ability is also essential to successful rice ratooning.
Higher‐Order Analysis of Nutrient Accumulation Data
Authors: Sadler E. John , Karlen Douglas L.
Published: July 2010

Biomass and nutrient accumulation data have often been obtained to determine rates of nutrient uptake. Traditionally calculated as the difference in accumulation divided by elapsed time, rate values thus obtained are slopes of linear interpolations between points on the accumulation curve. That implies an assumption of constant uptake rate during the observation period. Our objective was to illustrate a higherorder interpolant that is not subject to such assumptions. With it, one obtains smooth curves consistent with the assumption that daily uptake rates are somewhat related. The abrupt changes in rates determined with linear interpolation are consistent with daily rates that are unrelated. Analyses of historical and recent data showed that additional information may be obtained from higher‐order analysis methods. Cubic interpolation methods were applied to the accumulation curve to obtain continuous, smooth nutrient uptake curves. The programs used are described, and two sample data sets of corn (Zea mays L.) growth and N accumulation illustrate the strengths, weaknesses, and inherent assumptions of this analytical technique. In general, this technique can be used if the objective is to analyze intraseasonal variation in growth or uptake rates determined from sparse data.
Tillage Effects on Dryland Wheat and Sorghum Production in the Southern Great Plains
Authors: Unger Paul W.
Published: July 2010

Winter wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] are important, well‐adapted grain crops for the semiarid southern Great Plains. They often are grown in rotation on dryland to reduce the risk of failure associated with annual cropping and to overcome the low precipitation‐use efficiencies associated with crop‐fallow systems. This study on Pullman soil (Torrertic Paieustoli) determined the effects of 12 tillage systems ranging from no‐tillage (herbicides only) to sweep tillage (no herbicides) on water storage and use, crop growth, yields, and yield components for dryland wheat and sorghum grown in rotation. Tillage systems did not affect mean water storage during fallow nor mean water use by either crop. All yield, growth, and yield component factors differed among growing seasons. Wheat grain and straw yields were not affected by tillage. Mean wheat grain yield was 2.92 Mg ha−1. Mean sorghum grain yield was greatest (3.91 Mg ha−1) for the system of reduced tillage after sorghum and no‐tillage after wheat, and least (3.48 Mg ha−1) for the system of reduced tillage after each crop. Sorghum stover yields were not affected by tillage. Number of panicles harvested was greatest (233 000 ha−1) and least (212 000 ha−1) for the same treatments that resulted in the greatest and least grain yields. Sorghum seed weights and test weights were not affected by tillage. This study showed that a wide range of tillage systems is adaptable for a dryland wheat‐grain sorghum cropping system for the semiarid southern Great Plains.
Evaluation of Resistances for Bermudagrass Turf Crop Water Stress Index Models
Authors: Jalali‐Farahani H. R. , Slack D. C. , Kopec D. M. , Matthias A. D. , Brown P. W.
Published: July 2010

Evaluation of the Penman‐Monteith‐based crop water stress index (CWSI), as a potential indicator of turf irrigation timing, requires reliable estimates of potential (minimum) canopy resistance, rcp, and aerodynamic resistance, ra. This paper compares various methods of estimating rcp and ra for evaluation of water stress of bermudagrass turfgrass (Cynodon dactylon cv. Midiron) in the desert Southwest of the USA. First, two empirical CWSI models were developed using field data collected from well‐watered and severely water‐stressed turf plots during the 1986 growing season in Tucson, AZ. Second, the regression constants in the empirical lower limits of CWSI (canopy temperature minus air temperature, Tc − Ta, of nonwater‐stressed turf) and the parameters associated with similar terms (net radiation and vapor pressure deficit) in the Penman‐Monteith equation were equated, thus solving for rcp and ra. This yielded mean rcp and ra values of 79 and 13 s m−1, respectively. Using these estimates, the predicted lower limits of Tc − Ta from the Penman‐Monteith equation were in good agreement with values measured over well‐watered turf. However, the predicted Tc − Ta for severely water‐stressed turf agreed very poorly with the measured values. The use of the log‐law equation yielded independent estimates of ra generally greater than 45 s m−1 and resulted in erroneous estimates of Tc − Ta by the Penman‐Monteith equation. Using a crop‐based method and data from the turf plots, estimates of the resistances were made in which constant rcp and ra values of 62.5 and 20 s m−1, respectively, were found. The crop‐based method was found to be not only simple to use, but also performed satisfactorily in predicting Tc − Ta. A well‐defined curvilinear relationship between estimates of midday canopy resistance (rc) and CWSI was determined for a wide range of turf water stress, implying that these two estimates nearly equally reflect the state of turf water stress. Our findings also suggest threshold midday CWSI and rc values for short bermudagrass turf of 0.16 and 125 s m−1, respectively, to indicate the need for irrigation.
Influence of Residue Removal Method and Herbicides on Perennial Ryegrass Seed Production: II. Crop Tolerance
Authors: Mueller‐Warrant George W. , Young William C. , Mellbye Mark E.
Published: July 2010

Inherent in the ongoing transition from open‐field burning to nonburn systems for grass seed production in the Pacific Northwest is an increased reliance on herbicides for weed control. However, herbicide treatments able to control volunteer crop seedlings, the most abundant weed in certified grass seed fields, may pose severe hazards to the established crop itself. Fourteen herbicide treatment sequences plus an untreated check were examined in five residue removal systems at two sites during two consecutive growing seasons to determine their impact on perennial ryegrass (Lolium perenne L.) seed yield. Seed yield was reduced by weed competition in nonburned, untreated checks, and by herbicide injury in some of the 14 herbicide treatment sequences. When compared across 13 promising herbicide treatments, seed yield did not differ between burned and nonburned plots in the first year, although burning was slightly superior in the second. However, the cumulative yield advantage to burning was only 84 kg ha−1, or 2.6%, over the 2‐yr period. Although differences in yield among four herbicides applied preemergence (PRE) to seedling grasses in mid‐October were relatively small, pendimethalin [N‐(1‐ethylpropyl)‐3,4‐dimethyl‐2,6‐dinitrobenzenamine] and oxyfluorfen [2‐chloro‐1‐(3‐ethoxy‐4‐nitrophenoxy)‐4‐(trifluoromethyl) benzene] were superior to either metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl)acetamide] or trifluralin [2,6‐dinitro‐N,N‐dipropyl‐4‐(trifluoromethyl)benzenamine] in specific instances. When applied following PRE herbicides, early December post‐emergence (POST) applications of 1.8 kg ha−1 diuron [N'‐(3,4‐dichlorophenyl)‐N,N‐dimethylurea] or 0.14 kg ha−1 oxyfluorfen plus 1.3 kg ha−1 diuron generally did not differ in yield. While there was usually little net effect on seed yield of applying POST herbicides following pendimethalin, they did depress yield 129 kg ha−1 the first year in burned plots, while increasing it an average of 79 kg ha−1 the second year in all plots. With properly chosen herbicide treatments, the impact on perennial ryegrass seed yield of changing to nonburned methods of residue removal should be minimal. If such herbicide treatments are not available, however, the elimination of field burning may seriously disrupt perennial ryegrass seed production.
Peanut Acclimation to Simulated Shading by Weeds
Authors: Barbour James C. , Bridges David C. , NeSmith D. Scott
Published: July 2010

Research was conducted to assess the acclimation responses of ‘Florunner’ peanut (Arachis hypogaea L.) to shading and the possible role of this acclimation in determining pod yield loss due to shading by weeds. The PNUTGRO model is being used to develop a model of competition for light between peanut and broadleaf weeds. This research was undertaken to validate the treatment of peanut response to shading in PNUTGRO. Peanut plants were grown in two matched growth chambers. At 2 wk after planting, light in one chamber was reduced to 51% of total daily photosynthetic photon flux density (PPFD) received by the full‐light treatment (900 μmol m−2 s−1). Photosynthetic rates acclimated to shading within 3 d. Apparent photosynthesis (AP) rates of shaded vs. control plants were not different at 350, 500, or 1000 μmol photons m−2 s−1, but at 2000 μmol m−2 s−1 shaded plants had AP rates 76% of those of controls. Specific leaf area (SLA) of shaded plants was not statistically different from the controls. There were no observed differences in chlorophyll content or chlorophyll a:b ratios within 3 d after imposition of shading. Field studies were conducted in 1991 and 1992 with shading imposed by shade cloth attached to computer‐controlled shelters. Shading reduced total daily PPFD by 40%, from about 40 d after planting to harvest. Leaf photosynthesis measurements confirmed laboratory results, indicating that shade‐acclimated peanut plants had greater efficiency at low light levels. Shaded plants accumulated less dry weight and were taller than controls. Shaded plants produced fewer roots, with root length density remaining nearly constant after shade imposition. Over the two years, the shaded plants averaged 72% of the fulllight yield on 60% of the PPFD, even though they produced fewer pods. Shaded peanut plants maintain photosynthetic capacity at low light and change partitioning to optimize utilization of available assimilate. Reproductive changes included production of fewer pegs, but a larger proportion of pegs produced harvestable pods. PNUTGRO performed well in simulating dry matter accumulation, but consistently overestimated SLA. It predicted 30% yield loss in both 1991 and 1992. Observed yield losses were 33 and 26% in the 2 yr, respectively. PNUTGRO performed sufficiently well in simulating shade response by peanut to justify its use in a light competition model.
Dairy Manure Applications to Alfalfa: Crop Response, Soil Nitrate, and Nitrate in Soil Water
Authors: Daliparthy Jayaram , Herbert Stephen J. , Veneman Peter L. M.
Published: July 2010

Many dairy farmers apply manure predominately to land cropped to corn (Zea mays L.), often in excess of crop N requirements, resulting in potential groundwater contamination. Our research objective was to study the impact of dairy manure applications to established alfalfa (Medicago sativa L.) on crop response and on soil and soil water NO‐3‐N concentrations. Field experiments were initiated in 1990 on an Occum fine sandy loam variant soil (coarse‐loamy, mixed, mesic Fluventic Dystrochrepts) at South Deerfield and on an Agawam fine sandy loam soil (coarse‐loamy over sandy or sandy‐skeletal, mixed, mesic Typic Dystrochrepts) at Sunderland in western Massachusetts. Treatments consisted of zero N, low manure N (112 kg N ha−1 yr−1), high manure (336 kg N ha−1 yr−1), low N fertilizer (112 kg N ha−1 yr−1 from NH4 NO3), and high N fertilizer (336 kg N−1 yr−1 from NH4NO3). Liquid dairy manure or NH4NO3 was spread on the surface immediately after the first cutting in June 1990 and again in June 1991. Porous ceramic cup suction samplers were placed at the 30‐, 60‐, 90‐, and 120‐cm depths. Soil water was monitored throughout the year except in winter, when the topsoil was frozen. Movement of NO‐3‐N was observed to be more rapid in the sandier Agawam soil than the Occum soil. Nitrate‐N concentrations in water collected under alfalfa during summer and fall were significantly higher than in the spring. High concentrations of NO‐3‐N coupled with increased soil saturation during the fall make this period critical for monitoring NO‐3‐N movement. High manure application to alfalfa resulted in high soil water NO‐3‐N levels in the fall of 1991 on the Occum soil at the South Deerfield site. Application of N fertilizer at the high rate resulted in significantly increased NO‐3‐N concentrations. Low manure application to alfalfa did not increase NO‐3‐N concentrations in soil water compared with alfalfa receiving no N fertilization. Application of manure to alfalfa at the low rate had no significant effect on dry matter (DM) yields, N accumulation in herbage, and soil NO‐3‐N at the 0‐ to 25‐cm, 25‐ to 50‐cm, and 50‐ to 100‐cm depths. Dry matter yields were significantly lower at the South Deerfield site in 1991–1992 than in 1990–1991 for the high manure application. At the Sunderland site, no significant difference in yield was observed. Dairy manure can be applied to established alfalfa at the low rate of 112 kg N ha−1 without any adverse impact on herbage production or nitrates in soil water.
Light Reflectance Compared with Other Nitrogen Stress Measurements in Corn Leaves
Authors: Blackmer Tracy M. , Schepers James S. , Varvel Gary E.
Published: July 2010

New tools that can rapidly quantify the N status of corn could be valuable in N fertilizer management practices. This study was conducted to compare light reflectance from corn leaves with other parameters used to detect N deficiencies. Light reflectance (400–700 nm) as measured from corn leaves in the laboratory with a Hunter tristimulus colorimeter was compared with Minolta SPAD 502 chlorophyll meter readings (light transmittance at 650 and 940 nm), leaf N concentrations, and specific leaf N (N content per unit area). Measurements were made on individual ear leaves collected from an irrigated corn N response trial with four hybrids and five N treatments. Light reflectance near 550 nm was the best wavelength to separate N treatment differences. Reflectance at 550 nm provided a stronger relationship with both leaf N concentration and chlorophyll meter readings than between chlorophyll meter readings and leaf N concentration. The measurement of light reflectance near 550 nm has promise as a technique to detect N deficiencies in corn leaves.
Tillage, Nitrogen Timing, and Planting Date Effects on Western Corn Rootworm Injury to Corn
Authors: Roth Gregory W. , Calvin Dennis D. , Lueloff Susan M.
Published: July 2010

The western corn rootworm (WCR) (Diabrotica virgifera virgifera Le‐Conte) has become a serious pest of continuous corn (Zea mays L.) in the northeastern USA. Several recommended crop production practices in this area, such as early planting, sidedressing N applications, and no‐till, often contribute to slow early‐season growth, which could affect the potential for damage from the WCR. The objective of this study was to determine if these practices affected root damage ratings or yield reductions associated with the WCR. Field experiments were conducted in 1991, 1992, and 1993 on well‐drained Hagerstown silt loam soils (fine, mixed, mesic Typic Hapludalfs). Treatments in each study were factorial combinations of two tillage treatments( nonea nd chisel‐disk), three timings of N fertilizer application (at planting, sidedressed, or split), two planting dates (early and late May), and two insecticide treatments (none and 1.12 kg ha−1 chlorpyrifos). Each treatment was replicated four times. Lodging, root damage ratings, root dry matter estimates, and grain and silage yields were measured for each treatment. Root damage ratings were not affected by the planting date, N timing, or the tillage system. Insecticide had a large and consistent effect on reducing root damage from the WCR. Root size estimates indicates that late planting reduced root size but did not affect root damage. These results indicate that reduced tillage, N sidedressing, and early planting can be included in an integrated pest management program with no risk of increasing the potential for root damage from the western corn rootworm.
Regional Maize Grain Yield Response to Applied Phosphorus in Central America
Authors: Raun William R. , Barreto Hector J.
Published: July 2010

Maize (Zea mays L.) in Central America is commonly grown under continuous cultivation and on marginal lands where restricted use of conservation practices and fertilizers limit productivity. Maize grain yield response to P source, rate, and method of application was evaluated at 33 locations in Central America. Soil orders included Andisols, Inceptisols, and Ultisols. Treatments included rock phosphate (RP) applied broadcast preplant without incorporation at rates of 13 and 26 kg P ha−1, triple superphosphate (TSP) band‐applied at planting at rates of 13 and 26 kg P ha−1, TSP broadcast preplant at 26 kg P ha−1, and a check where no P was applied. All treatments received 100 kg of N ha−1 as urea applied in split applications and 30 kg S ha−1 as CaSO4·2H2O. Averaged over locations, maize grain yield increased 0.38 and 0.74 Mg ha−1 when 13 and 26 kg P ha−1 was band‐applied as TSP and increased 0.21 and 0.16 Mg ha−1 when RP was broadcast at the same rates. All P treatments had a probability (PR) >0.61 of outperforming the unfertilized check. Triple superphosphate band‐applied at 26 kg P ha−1 offered the greatest probability (0.69) of an economic response to P fertilizer across environments. Stability analyses and analyses of yield differences suggest that response to applied P was independent of environment for the sites evaluated. The consistent response to applied P across a wide range of environments demonstrates that P is a limiting element for maize production on marginal lands in Central America and that the probability for economic response to applied P is high.