bluuebunny/crossref_metadata_2025 huggingface dataset:
Soybean Yield Response Prediction from Soil Test and Tissue Manganese Levels1
Authors: Gettier S. W. , Martens D. C. , Donohue S. J.
Published: July 2010

Manganese deficiency continues to be a yield limiting factor in soybean [Glycine max (L.) Merr.] production on many Atlantic Coastal Plain soils. Field research was conducted in order to refine the double acid (also known as the Mehlich I) extractable Mn soil test and to determine critical Mn deficiency levels for whole plant, leaf and seed plant parts. Experiments on Mn deficiency in soybeans were conducted at 30 field locations with 13 soil types, spanning 7 years. A total of eight soybean cultivars were used in this field research. A yield prediction equation was developed (r = 0.68**, significant at the 0.01 level) with the inverse relationship of pH and double acid extractable Mn in the Ap horizon. Inclusion of organic matter and the same soil parameters in the B horizon did not improve the equation's predictive ability. Yield prediction equations were developed for whole plant (r = 0.44*, significant at the 0.05 level), leaf (r = 0.94**), and seed (r = 0.73**) Mn concentrations. Based on 90% of maximum yield as the definition of the critical deficiency level, the critical Mn levels for whole plant, leaf, and seed were 45, 17, and 20 mg/kg, respectively. The eight soybean cultivars evaluated in this study had similar responses to low levels of available Mn.
Chloride and Liming Effects on Soil Nitrogen Form and Take‐all of Wheat1
Authors: Christensen N. W. , Brett Marcia
Published: July 2010

Little is known about how chloride (Cl) functions in suppressing take‐all root rot of wheat (Triticum aestivum L.). A field experiment was conducted to determine the effects of liming and CI application on ammonium (NH+4 and nitrate (NO−3‐N) concentrations in soil as they correlate with development of the disease. ‘Hill 81’ soft white winter wheat was grown on a limed (pH 6.6) and unlimed (pH 5.5) Aquultic Argixeroll fertilized with a factorial combination of 30 kg N ha−1 as NH4NO3, (NH4)2SO4, or NH4Cl banded at planting and 140 kg N ha−1 as Ca(NO3)2, (NH4)2SO4, or NH4Cl topdressed in the spring. Soil was sampled to 10 and 20 cm depths and analyzed for NH+4‐N, NO−3‐N, Cl, and pH at weekly intervals for 10 weeks following spring application of N. Take‐all was assessed at 0, 6, and 11 weeks after spring fertilization. Take‐all severity, NH+4‐N and NO−3‐N concentrations, NH+4‐N:NO−3‐N ratios, and grain yield were all influenced by a highly significant interaction between liming and spring‐topdressed Cl. Liming hastened disappearance of NH+4‐N and increased appearance of NO−3‐N in soil. Chloride slowed disappearance of NH+4‐N and appearance of NO−3‐N in unlimed soil but not in limed soil. A “critical” NH+4‐N:NO−3‐N ratio for take‐all suppression of 3:1 was estimated from data in the literature. Takeall severity was negatively correlated (r2=0.84) with the length of time the NH+4‐N:NO−3‐N ratio remained above the estimated critical ratio. Chloride increased grain yield from 3.5 to 4.7 Mg ha−1 on the unlimed soil but had no effect on yield on the limed soil. Results suggest that Cl may reduce take‐all severity and increase grain yield on moderately acid soils in western Oregon by reducing nitrification and maintaining a favorable NH+4‐N:NO−3‐N ratio for disease suppression.
Responses of Soybean Canopy Photosynthesis and Transpiration to Whole‐Day Temperature Changes in Different CO2 Environments1
Authors: Jones Pierce , Allen L. H. , Jones J. W.
Published: July 2010

Response of plants to increased temperatures, as well as increased CO2, is one of the concerns about the global consequences of continued burning of fossil fuel. In this study, soybeans [Glycine max (L.) Merr. cv. Bragg] were grown in controlled‐environment chambers located outdoors and acclimated to two environmental CO2 levels, 330 and 800 µmol mol−1. Canopies were exposed to different day‐long dry bulb temperature treatments that were maintained for a few days. Comparisons of CER‐light response curves and daytime total CO2 exchange from both low and high CO2 treatments indicated that canopy CER was not significantly affected by dry bulb temperature in the range 28°C to 35°C (nighttime temperature was 23°C). Canopy water use increased significantly in both CO2 treatments as dry bulb temperature was increased and the dewpoint temperature was kept at 21°C. Calculated total canopy resistances were constant throughout the temperature treatments in each of the CO2 treatments. This indicated that between dry bulb treatments, changes in canopy water use resulted strictly from temperature‐driven changes in the vapor pressure gradients within the canopy. Characteristic ratios of internal to external canopy CO2 concentrations were calculated and found to be similar among all temperature treatments and in both CO2 treatments. Across all temperature treatments, cumulative daytime transpiration was nearly equal between the two CO2 treatments, however, water‐use efficiency (WUE) decreased in both CO2 treatments as dry bulb temperature increased. Since CER response in both CO2 treatments was unaffected by air temperature across the range of 28 to 35°C, the decrease in WUE with increasing temperature was due solely to increasing transpiration.
Tillage and Low‐Pressure Center‐Pivot Irrigation Effects on Corn Yield1
Authors: Wilhelm W. W. , Mielke L. N. , Gilley J. R.
Published: July 2010

Low‐pressure sprinkler irrigation systems have the potential to save energy, but also may aggravate soil‐ and water‐management problems. The objective of this research was to determine the influence of center‐pivot sprinkler irrigation method in combination with various tillage practices on corn (Zea mays L.) yield and yield components. A center‐pivot irrigation machine was redesigned to apply water by high‐pressure‐impact (HPI), low‐pressure‐impact (LPI), and low‐pressure‐spray (LPS) nozzles. Nozzles were sized and spaced to apply three different amounts of water: 100% (full irrigation), 75 and 50%. Three tillage treatments were used—till‐plant (T), disk (D), and till‐plant with chisel after last cultivation (C)—for each method and amount of water applied. The field study was conducted over a 4‐year period (1978 to 1981) on a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudolls). Yields were influenced by the seasonal distribution and amount of precipitation, irrigation water applied, tillage, and the combined management inputs. The method of water application (HPI, LPI, and LPS nozzles) did not significantly (P > 0.10) influence grain yield. In 1979, the chisel tillage treatment produced significantly less grain than other treatments because severe root pruning limited stored water uptake during an extremely stressful period immediately following the chisel operation. No inherent differences in productivity were associated with low‐pressure center‐pivot‐sprinkler irrigation, or with various conservation‐tillage practices used in combination with reduced‐pressure‐sprinkler irrigation. Therefore, use of these practices can reduce production costs without reducing yield.
Effect of N Fertilization on Earthworm and Microarthropod Populations in Kentucky Bluegrass Turf1
Authors: Potter Daniel A. , Bridges Barry L. , Gordon F. Carter
Published: July 2010

Earthworms and microarthropods are abundant in turfgrass and may be important to thatch decomposition and nutrient recycling. There is little published information concerning the effects of cultural practices on the soil fauna in turf. The purpose of this study was to determine the influence of prolonged N fertilization on populations of earthworms, Collembola, and Acari involved h decomposition processes in Kentucky bluegrass, and to relate these effects to changes in soil pH and thatch accumulation. Six rates of ammonium nitrate fertilizer ranging from 0 to 25 g N m−2 were applied annually for 7 years to replicated plots of ‘Kenblue’ Kentucky bluegrass (Poa pratensis L.) growing on a Maury silt loam soil (fine‐silty, mixed, mesic Typic Paleudalf) near Lexington, KY. Populations of earthworms and soil microarthropods were enumerated in May and October 1983. Increasing the rate of N fertilization resulted in a significant decline in soil and thatch pH and in exchangeable Ca and K, and caused a significant increase in thatch. Regression analyses indicated a highly significant linear decrease in earthworm density and biomass as annual rates of N fertilization increased. Collembola were more abundant at an intermediate fertilizer rate, whereas Acaridae were unaffected by N fertilization. Cryptostigmata, predominantly Scheloribates sp., were the most abundant arthropod decomposers in the turf. Each of the seven oribatid mite species differed in its response to N fertilization. The study indicates that when N fertilizer is applied to Kentucky bluegrass at rates sufficient to cause soil acidification, populations of earthworms and certain other decomposers may be severely reduced. Thatch accumulation was negatively correlated With earthworm density and biomass, although other factors probably also contributed to thatch development.
Water Uptake and Release by Alfalfa Roots1
Authors: Dirksen C. , Raats P. A. C.
Published: July 2010

Water release to dry upper soil by alfalfa roots amply supplied with water in the bottom of the rootzone could not be measured by gamma‐ray attenuation. Variations in the CO2and O2concentrations of the soil water had no measurable effect on water release. After having been nearly inactive with respect to water uptake in dry soil for more than 50 days, the upper roots took up water at a high rate immediately after rewetting. If metabolic influences of the plants are negligible, such polarity between water uptake and release must depend on the location and relative magnitudes of the main resistances in the two types of flow. Comparison of leaf water and soil water total potentials indicated little resistance in the xylem and major resistance in the radial pathway. Water uptake across large radial resistances causes low water potentials inside the xylem. For this water to be released to drier soil elsewhere, water potentials there must be even lower than in the xylem. Associated large soil‐root interface resistances are likely to prevent water release of any significance. Such resistances are suggested as an explanation for the generally observed polarity between water uptake and release.
Comparison of Urea and Urea‐Ammonium Polyphosphate with Ammonium Nitrate in Production of Tall Fescue1
Authors: Murdock L. W. , Frye W. W.
Published: July 2010

The yield response of tall fescue (Festuca arundinacea Schreb, cv. Kentucky 31) to urea (45% N) and urea‐ammonium polyphosphate (34% N; 7.5% P) was compared with that from ammonium nitrate (33% N). The fertilizers were surface‐applied to the fescue at a rate of 78 kg ha−1N several times during the growing season. Ammonium nitrate and urea were applied twice per month from early April through mid‐September of 1973, 1974, 1975, and 1977. Urea‐ammonium polyphosphate was applied monthly during the same period of 1974, 1975, and 1977. Yield response, defined as yield with N fertilizer minus yield without N fertilizer, was significantly lower (P < 0.05) with urea than with ammonium nitrate at all application dates except mid‐April and early May and September. The difference in September was significant at the 10% level. Yield response with urea‐ammonium polyphosphate was not significantly different (P > 0.10) than with urea at the same application dates. The lower yield response to urea compared with ammonium nitrate was thought to result from volatilization loss of NH3. Fitted polynomials of the relationship between yield response to urea relative to ammonium nitrate (RRn) and the number of days following urea application until cumulative rainfall of at least 2.5, 5, 10, and 20 mm gave 2values of 0.55, 0.54, 0.48, and 0.33, respectively; RR, values were usually higher when at least 2.5 mm of rain fell in < 3 days after application, and that amount of rainfall within that time appeared to be adequate to prevent large volatilization loss of NH3. The RRnvalues were usually lower when the first rainfall, regardless of amount, occurred > 3 days after application.
Shade‐Sensitive Interval of Kernel Number of Maize1
Authors: Kiniry J. R. , Ritchie J. T.
Published: July 2010

There have been many investigations into the time interval when maize (Zea maysL.) yield is most susceptible to stress. Knowledge of this interval is important for understanding yield potential, modeling, irrigation scheduling, and the study of the partitioning of assimilate into grain. The objective of this experiment was to determine the growth stage when shading stress affected number of kernels per ear. Three commercial maize hybrids were grown on a Houston black clay (fine montmorillonitic, thermic Udic Pellustert) under irrigation near Temple, TX in 1982 and 1983. Plants were stressed using horizontal shade panels that reduced the light by 79% for approximately 13‐day intervals. In order to define when number of kernels was affected, the panels were moved three times each week to provide an overlapping series of treatments. The number of kernels of each treated plant was measured and treatment means were compared with unshaded controls. The growth stage when shading decreased the final kernel number was closely associated with early kernel development, occurring near the end of the lag period of grain filling. Duration of the sensitive period varied from 6 to 23 days. It was speculated that a stress applied in the first 1 to 2 weeks after pollination caused a temporary shortage of assimilate for the ear, severely limiting endosperm cell number of some tip kernels. These kernels would not fill later, even if stress was relieved.
In Vitro Digestion, Chemical Composition, and Fermentation of Ammoniated Grass and Grass‐Legume Silage1
Authors: Moore K. J. , Lechtenberg V. L. , Lemenager R. P. , Patterson J. A. , Hendrix K. S.
Published: July 2010

Post harvest treatment of low‐quality grass hays with anhydrous ammonia (NH3) has been demonstrated to improve energy availability and crude protein concentration. Two experiments were conducted to determine what effect NH3treatment would have on the composition, fermentation, and digestibility of grass and grass‐legume silage. In the first experiment mature first‐cutting orchardgrass (Dactylis glomerataL.) herbage was harvested, ammoniated at 0, 7.5, 15, and 30 g/kg dry weight (DW), and ensiled at a moisture concentration of 703 g/kg wet weight (WW) for 8 weeks. The ensiled herbages had pH values of 4.4, 4.8, 5.8, and 5.9, respectively. Ammoniation at 7.5, 15, and 30 g/kg DW increased the concentration of total N by 5, 11, and 24 g/kg DW, respectively. Ammoniation at 30 g/kg DW increased (P<0.05) in vitro digestibility of dry matter (DM), neutral detergent fiber (NDF), acid detergent fiber (ADF), hemicellulose, and cellulose by 104, 132, 110, 132, and 128 g/kg, respectively. Ammoniation at 7.5 and 15 g/kg DW had no effect (P>0.05) on the digestibility of DM or any fiber constituent. In the second experiment, mature first‐cutting herbage composed of approximately 90% orchardgrass and 10% white clover (Trifolium repensL.) was ammoniated at 0,15, and 30 g/kg DW prior to ensiling for 10 weeks at a moisture concentration of 635 g/kg WW. The silages had pH values of 4.7,6.8, and 7.1, respectively. Ammoniation at 15 and 30 g/kg DW increased (P<0.05) the concentration of total N by 14 and 23 g/kg DW, respectively. Ammoniation at 15 and 30 g/kg DW increased (P<0.05) the extent for in vitro NDF digestion by 126 and 236 g/kg NDF. Rate constants for in vitro NDF digestion did not differ (P>0.05) among ammoniated silages but were greater (P<0.05) than those observed in the control. Rate constants averaged 0.061/h for the ammoniated silages and 0.051/h for the control.
Effect of Irrigation Interval on St. Augustinegrass Rooting1
Authors: Peacock Charles H. , Dudeck A. E.
Published: July 2010

Irrigation is an integral part of a turfgrass management program. Turfgrass rooting characteristics within the soil profile determine how much soil moisture is available to support turfgrass growth. Determination of optimum irrigation intervals and the effects on turfgrass rooting will help provide better utilization of irrigation water resources. Rooting response to irrigation intervals was studied on ‘Floratam’ St. Augustinegrass [Stenotaphrum secundatum(Walt.) Kuntze] during the 1980 and 1981 growing seasons. Root mass and length on a dry‐weight basis were determined in 15‐cm profile increments to a depth of 75 cm from field plot samples at beginning and end of the study period. Treatments received the same irrigation volume but irrigation interval was every 2, 3, 4, or 6 days.Root mass and length density were unaffected by irrigation treatments during 1980. Total root mass density decreased 42% and root length density decreased 37% within the profile on a land‐area basis from beginning to end of the study period. Over 40% of the root mass occurred below 30 cm in the profile.Root mass density increased during 1981 from initial to final sampling for all profile depths except 60 to 75 cm but there was no treatment effect. In contrast to 1980, only 9% of the roots were distributed below 30 cm in the soil profile. Root length density increased for the 30‐ to 45‐cm and 45‐ to 60‐cm depths but was unchanged for the other depths. Total root mass density on a land‐area basis increased for all treatments but total root length density did not. This indicates that with the irrigation volume applied, St. Augustinegrass increased root size but not root length, regardless of irrigation interval. This would afford an advantage in survivability but not in drought avoidance.
Soil Compaction and Moisture Stress Preconditioning in Kentucky Bluegrass. I. Soil Aeration, Water Use, and Root Responses1
Authors: Agnew M. L. , Carrow R. N.
Published: July 2010

Soil compaction and moisture stress are major problems on recreational turfgrass sites. In the greenhouse, we investigated root responses to soil compaction and moisture stress preconditioning, and their effects on water use of Kentucky bluegrass (Poa pratensisL. ‘Ram I’). The compaction treatments included: (i) NC = no compaction, (ii) LT = long‐term compaction (equivalent to 720 J energy) over a 99‐day period, and (iii) ST = short‐term compaction for 9 days. Irrigation regimes were initiated at the same time as LT compaction. They included: (i) well watered = irrigation at −0.045 MPa and (ii) water stressed = irrigation at −0.400 MPa. Ninety‐nine days after initiation of preconditioning treatments and after watering each treatment to saturation, a dry‐down cycle was started. Compaction treatments reduced ODR to below 0.20 µg cm−2min−1for 143 h compared with 26 h in the uncompacted turf. Long‐term compaction increased root weights in the upper 5 cm and decreased root weights in the lower 10 to 20 cm profile. Short‐term compaction decreased root weights only at 15 to 20 cm. Root porosity was increased by LT compaction, but the greatest increase was for the combination of LT compaction and water stress resulting in root porosities of 23%. Plants with higher root porosities also exhibited greater water uptake during low soil O2conditions. Soil compaction reduced total water use and moisture extraction in the deeper zones. Moisture stress preconditioning had no effect on root distribution but resulted in greater total water use, primarily from the 0‐ to 5‐ and 5‐ to 10‐cm soil zones.
Soil Compaction and Moisture Stress Preconditioning in Kentucky Bluegrass. II. Stomatal Resistance, Leaf Water Potential, and Canopy Temperature1
Authors: Agnew M. L. , Carrow R. N.
Published: July 2010

In this greenhouse study we investigated the effects of soil compaction and moisture stress preconditioning on stomatal diffusive resistance (Rs), leaf water potential (Ψ1), and canopy minus air temperatures (ΔT) of Kentucky bluegrass (Poa pratensisL. ‘Ram I’). The compaction treatments were: (i) NC = no compaction, (ii) LT = long‐term compaction over a 99‐day period, and (iii) ST = short‐term compaction for 9 days. The compactive treatment was equivalent to 720 J energy. Irrigation regimes were initiated at the same time as LT compaction and were: (i) well‐watered = irrigation at −0.045 MPa and (ii) water‐stressed = irrigation at −0.400 MPa. Ninety‐nine days after initiation of preconditioning treatments, a dry‐down cycle was started by watering each treatment to saturation. At this time, we monitored on a daily basis Rs, Ψ1, and ΔT. Under low soil O2, Rsremained low for 2 days and then increased over a 5‐day period for all treatments, even though Ψ1did not change until the fifth day after irrigation (DAI). By DAI 9, Rsdeclined but then increased between DAI 10 to 13 as soil water potential (Ψs) and Ψ1decreased. As soil water deficits increased, plants preconditioned to LT compaction or water‐stressed exhibited lower Ψ1(0.2 to 0.4 MPa), higher Rs, and higher Δ (1 to 2°C) compared with uncompacted or well‐watered plants. Regardless of the cause for higher Rs(i.e., low soil O2, LT compaction or water‐stress preconditioning), the result would be lower photosynthesis and greater high‐temperature stress.
Intake and Digestibility of Dry Matter and Fiber of Flaccidgrass and Switchgrass1
Authors: Burns J. C. , Mochrie R. D. , Timothy D. H.
Published: July 2010

Subtropical grasses are generally considered of lower nutritive value than temperate grasses. Flaccidgrass (Pennisetum flaccidumGriseb.) and switchgrass (Panicum virgatumL.) are subtropical species with high quality potentials. The objective of this study was to compare dry matter intake and the digestive coefficients for dry matter and several fiber constituents from hays of flaccidgrass (FG) and switchgrass (SG) with ‘Coastal’ bermudagrass [Cynodon dactylon(L.) Pers.] at similar neutral detergent fiber (NDF) concentrations. Initial growths were harvested as hay at appropriate development stages to obtain forages having similar NDF. Tall fescue (Festuca arundinaceaSchreb.) was included to provide comparisons with a temperate species. Hay intakes by eight Holstein heifers were measured in two squares of a 4 by 4 Latin square design. Digestion coefficients were calculated from data obtained during the fourth intake period of each square and were analyzed as a completely random design. The subtropical hays had similar NDF concentrations (0.710 to 0.753 g kg−1), but intakes differed. Coastal bermudagrass (CB) intakes of 2.70 kg 100 kg−1of body weight were followed by FG (2.29) and SG (2.09). Tall fescue (TF) intakes were similar to those for FG (2.25 vs. 2.29 kg 100 kg−1body weight). Dry matter digestibility of CB averaged only 0.496 compared with the greater but similar coefficients for the other three hays (0.624 g kg−1). The digestive coefficients for NDF and constituent acid detergent fiber (ADF) and cellulose were similar for FG, SG, and TF, averaging 0.649, 0.587, and 0.675, respectively, compared with lesser coefficients of 0.486, 0.435, and 0.517 from CB. Hemicellulose digestion was similar for FG and SG (avg 0.741) and appreciably greater than for CB (0.537); whereas, that for TF was intermediate (0.683). The greater digestibility of dry matter and fiber of FG and SG, compared with CB, partially explains the reported greater than expected animal daily performance from these two subtropical species and supports their use in ruminant feeding systems.
Tropical Legumes for Green Manure. I. Nitrogen Production and the Effects on Succeeding Crop Yields1
Authors: Reddy K. C. , Soffes A. R. , Prine G. M.
Published: July 2010

The energy shortage of the 1970s and knowledge that N prices may continue to escalate renewed interest in growing legume green manure crops to furnish N. The objective of this study was to evaluate the ability of selected green manure crops to furnish N to succeeding crops. This study evaluated seven tropical legumes and a marigold (Tagetes erectaL.) cv ‘Cracker Jack’ grown for different lengths of the summer under fumigation (F) and nonfumigation (NF) on Arredondo fine sand (loamy, silicious, hyperthermic Grossarenic Paleudults) during 1979, 1980, and 1981. Split‐plot and randomized complete block designs with five replicates were used. In the basic experiment, fumigation and nonfumigation were main plots and tropical legumes and fallow were the subplots. The green manure crops were grown for three different periods, early summer, full summer, and late summer. Early and late summer plantings usually included only the legume crops and fallow in a randomized complete block design. Average top growth N yields in kg ha−1were 40 for ‘PI 305070’ mungbean [Vigna radiata(L.) Wilcz.], 250 for ‘Norman’ pigeonpea [Cajanus cajan(L.) Millsp.], 190 for ‘FL 81d’ pigeonpea, 170 for showy crotalaria (Crotalaria spectabilisRoth.), 220 for hairy indigo (Indigofera hirsutaL.), 170 for jointvetch (Aeschynomene americanaL.), 190 for velvetbean [Mucuna deeringiana(Bort.) Merr.], and 60 for marigold. The dry matter yield of legumes (harvested before seeding) with higher N yields usually exceeded 10 000 kg ha−1for full‐season production in all 3 yr. Fumigation increased dry matter yield of legumes and marigold, but not their N yield.

The grass crops, rye (Secale cerealeL.), ryegrass (Lolium multiflorumL.), maize (Zea maysL.), and wheat (Triticum aestivumL.) produced significantly higher dry matter (up to 100%) when planted after green‐manure summer legumes than when planted after summer fallow. Calculated uptake of N from green manure by these grass crops was relatively low, averaging from −2 to 23 kg ha−1. Applying 50 and 100 kg N ha−1as ammonium nitrate to the green‐manured plots did not increase recovery of N from green manure by wheat.
Effect of Mefluidide on Cool‐Season Perennial Grass Forage Yield and Quality1
Authors: Sheaffer C. C. , Marten G. C.
Published: July 2010

Seasonal forage production of cool‐season perennial grasses is not uniform. Spring production is often under‐utilized in pastures while deficits frequently occur in the summer. We determined the effect of date of mefluidide {N‐[2,4‐dimethyl‐5‐[[(trifluoromethyl)sulfonyl] amino]phenyl]acetamide} application on distribution of forage yield and quality of orchardgrass (Dactylis glomerataL.), tall fescue (Festuca arundinaceaSchreb.), reed canarygrass (Phalaris arundinaceaL.), smooth bromegrass (Bromus inermisLeyss.), and Kentucky bluegrass (Poa pratensisL.) and the effect of a prespray clipping of these grasses on mefluidide activity. Two field experiments were each conducted for 2 yr on a fine‐silty over sandy or sandy‐skeletal, mixed, mesic Typic Hapludoll. In the first experiment, mefluidide (0.42 kg/ ha) was applied to the grasses in late September, late April, or mid‐May. In the second, mefluidide (0.42 kg/ha) was applied to the initial grass growth in early to mid‐May or to regrowth in late May to early June following an early spring defoliation. Forage dry matter yield and quality responded differently to mefluidide treatments each year in both experiments possibly due to differences in grass morphological development at application. However, all grass species responded similarily in yield or quality to meflufdide treatment. A late April mefluidide application (grasses vegetative, no culm elongation) consistently increased first harvest leafiness and forage quality compared to the control. Mean (over 2 yr) leaf/stem ratios and crude protein and neutral detergent fiber concentrations were 2.7, 16.3 dag/kg, and 54.6 dag/kg, respectively, for the April mefluidide treatment and 1.1, 13.1 dag/kg, and 61.5 dag/kg, respectively, for the control. However, increased forage quality was accompanied by decreased first harvest yields (mean yields of 2.0 and 4.0 Mg/ha for the April mefluidide treatment and control, respectively). Clipping spring growth before applying mefluidide to the regrowth had no consistent effect on grass forage yield or quality. Increased forage quality of the first crop due to mefluidide treatment may justify its use in extensive systems where surplus spring growth is usually wasted.
Yield and Seed Growth at Various Canopy Locations in a Determinate Soybean Cultivar1
Authors: Wallace S. U.
Published: July 2010

The purpose of this study was to investigate yield and seed growth in various parts of the canopy of a determinate soybean [Glycine max(L.) Merr.] cultivar. ‘Braxton’ soybeans were grown in a Cecil sandy loam soil (clayey, kaolinitic, thermic Typic Hapludults) with irrigation (I) applied when soil moisture tension exceeded 0.02 MPa and no irrigation (NI). Row width was 0.96 m, with intrarow spacings of 51, 102, and 152 mm in 1982 and 51 mm in 1983. Pods sampled during reproductive growth were separated into nine groups on the basis of pod location in one of three strata (based on canopy height) with a further separation into main stem pods or pods on lower, middle, or upper branches. Plot yields averaged 3068 and 1400 kg ha−1for the I and NI treatments, respectively. Intrarow spacing did not significantly influence yield. Yield in the upper canopy stratum increased from 33% of total crop yield in the NI treatment to 42% in the I treatment. With an increase in intrarow spacing from 51 to 152 mm, the relative yield contribution of main stems decreased from 31% of total yield to 15% while that of lower branches increased from 48 to 66%. Most pod groups did not differ in single seed weight, seeds per pod, or seed growth rate. These averaged 151 mg seed−1, 2.02, and 3.97 mg seed−1day−1, respectively. It was concluded that both irrigation and intrarow spacing influenced distribution of yield on branches and that yield increases in I soybeans were associated with increases in pod number and in percentage of total crop yield in the upper canopy.
The pe and pH Alfalfa Seedling Rhizospheres1
Authors: Blanchar R. W. , Lipton D. S.
Published: July 2010

Changes in pe and pH of alfalfa [Medicago sativaL.] rhizospheres may be important considerations in the description of nodulation and nutrient uptake. Growth chamber studies were done where alfalfa seedlings were grown into a Sharon sandy loam soil and in situ measurements of pH and pe in zones 0 to 0.5, 0.5 to 1, and 1 to 3 mm from root surfaces made. The pe of the soil 0 to 0.5 mm from lateral and main roots was 7.8 ± 0.05 and was the same as that of the soil at greater distances. The pH in the zone 0 to 0.5 mm from lateral roots was 4.2 ± 0.3, in the same zone near main roots 6.8 ± 0.4, and at distances greater than 3 mm it was 5.54 ± 0.9.
Intraraceme Competition in Field‐Grown Soybean1
Authors: Spollen W. G. , Wiebold W. J. , Glenn D. Scott
Published: July 2010

Abscission probability for positions within a soybean [Glycine max(L.) Merr.] raceme may not be equal. The influence of the two most proximal pods on abscission probability and growth of remaining pods within a raceme was studied using the soybean cultivar ‘Williams’. Plants were field grown (1982, Beltsville silt loam, Typic Fragiudult; 1983, Mattapeake silt loam, Typic Hapludult). Treatment consisted of removing or not removing the two most proximal (raceme Positions 1 and 2) pods. More flowers were produced at Node 8 than at either Node 10 or 12. Abscission probabilities for Positions 1, 2, 3, 4, and 5 of untreated racemes were 4, 10, 56, 77, and 99%. Removal of proximal pods decreased the abscission probability at Position 3 in five out of six instances (Nodes 8, 10, 1982; Nodes 8,10, and 12,1983) and at Position 4 in four of six instances (Node 8, 1982; Nodes 8, 10, and 12, 1983), but usually did not increase individual pod or seed weights. In most instances, individual pod and seed weights were smaller at Position 4 than at Position 1. The presence of proximal pods on soybean racemes interfered with the development of distal pods and increased the abscission probability of reproductive structures borne at distal positions.
Irrigation Effects on Agronomic Characters of Meadowfoam1
Authors: Pearson C. H. , Jolliff G. D.
Published: July 2010

Meadowfoam (Limnanthes albaBenth.), a winter annual adapted to Mediterranean climates, produces a seed oil that has potential uses in industry. Insufficient water during flowering and seed development of meadowfoam might cause the highly variable seed yields previously experienced. The effects of irrigation on oil yield, seed yield and yield components, plant growth and development, and honey bee (Apis melliferaL.) foraging were determined. Irrigation treatments included: none (control), early irrigation (EI) during flowering, and continued irrigation (CI) from flowering until maturity. The soil was a fine‐silty, mixed, mesic Aquultic Argixeroll. Seed yield was not increased with irrigation in 1981, probably because above‐average precipitation occurred during May and June, but in 1982 seed yield in the irrigated treatments averaged 32% higher than in the control. Seed yield differences between the El and CI treatments were not significant. Seeds per flower and 1000‐seed weights in the irrigated treatments in 1982 were 9 and 5% higher than in the control, respectively. Bee foraging at late flowering was greater in the irrigated treatments than in the control. Greater bee activity in the irrigated treatments may account for more seeds per flower in these treatments than in the control. The seed oil content in the irrigated treatments was significantly lower than in the control; however, meadowfoam in the irrigated treatments in 1982 yielded 29% more total oil than in the control. Compared with the control, irrigated plants were taller in both years and in 1982 produced more dry matter and had a smaller canopy light transmittance. In some years meadowfoam can be successfully grown in Mediterranean climates without irrigation; however, in other years irrigation during flowering and seed development, particularly during flowering, may be required to achieve high seed and oil yields.
Development Rate and Growth Duration of Oats in Response to Delayed Sowing1
Authors: Colville D. C. , Frey K. J.
Published: July 2010

Number of days and number of growing degree‐days have both been used to predict plant development, but advantages of each are not completely understood. The effect of delayed sowing on the rate of development and duration of growth in oats (Avena sativaL.) was determined in field studies over 2 yr on a Coland loam (Cumulic Haplaquoll) soil at the Hinds Experiment Farm near Ames, IA. Number of growing degree‐days (GDD) and number of days to reach emergence, tiller initiation, fourth‐, fifth‐, and flag‐leaf stages, heading,and 80% panicle ripe were computed. Yield, bundle weight, and test weight were measured, and straw yield and vegetative growth index were calculated. Correlations were calculated for these values with number of days and with number of GDD to each stage of development.

With delayed sowing, significant correlations occurred between yield factors and GDD, rate of development, and duration of growth. Number of days to reach each stage of development was significantly reduced by delayed sowing, whereas number of GDD was not. Neither, straw yield, or test weight. Both, however, could be useful for predicting rate of development and duration of growth; however, since number of GDD is less variable throughout a growing season, its use is recommended.
Alfalfa Response to Potassium, Irrigation, and Harvest Management1
Authors: Sheaffler C. C. , Russelle M. P. , Hesterman O. B. , Stucker R. E.
Published: July 2010

The purpose of this research was to evaluate the combined effect of irrigation, K fertilizer, and harvest management variables on the production of multi‐disease‐resistant, winterhardy alfalfa (Medicago sativaL.) cultivars. A field experiment was conducted on a sandy, mixed Udic Haploboroll to determine the effects of three irrigation regimes, three harvest managements, and four annual K rates (0, 167, 334, and 501 kg ha−1) on forage yield, forage quality, and persistence of‘Ramsey’ and ‘520’ alfalfa. No, full, and medium irrigation treatments were applied. Both full and medium irrigation regimes applied 3.5 cm of water when 50% of the extractable soil water had been depleted, but the medium irrigation was less frequent. Harvest managements consisted of: two harvests at full flower and one in late fall (HI), three harvests at one‐tenth flower and one in late fall (H2), and three harvests at one‐tenth flower (H3). Forage dry matter yield response to K increased with increasing irrigation, from 0.0033 Mg ha−1kg−1K in nonirrigated to 0.0058 Mg ha−1kg−1K in fully irrigated alfalfa. Yield response to K was similar for harvest managements within no and medium irrigation regimes, but for the full irrigation regime, yield increased 0.0071 Mg ha−1kg−1K with harvest at one‐tenth flower, and only 0.0031 Mg ha−1kg−1K with harvest at full flower. Following a severe winter after 2 yr of harvesting, the greatest stand and yield losses occurred with full irrigation and the most intensive (four‐cut) harvest management. Mean final stands in the four‐cut management were 19, 39, and 74% for full, medium, and nonirrigated alfalfas, respectively. Stand persistence and residual yield were increased by K fertilization under more frequent (one‐tenth flower) harvest of irrigated alfalfa. Cultivars did not consistently differ in yield in two production years, but the less winterhardy 520 had greater final stands than Ramsey. Potassium fertilization is beneficial to yield and stand of alfalfa, although the response varies with irrigation and harvest management.
A Procedure to Select Drought‐Tolerant Sorghum and Millet Genotypes using Canopy Temperature and Vapor Pressure Deficit1
Authors: Chaudhuri U. N. , Deaton M. L. , Kanemasu E. T. , Wall G. W. , Marcarian V. , Dobrenz A. K.
Published: July 2010

Plant temperatures have been identified as indicators of plant water use and yield. The purpose of this experiment was to determine the potential of using canopy temperature for selecting drought‐tolerant genotypes. In 1983, 219 sorghum [Sorghum bicolor (L.) Moench] genotypes, assembled from Purdue University, the University of Arizona, Texas A & M University, and commercial seed companies, and 42 millet [Pennisetum americanum (L.) Leeke] genotypes from the University of Arizona, the University of Nebraska, and Kansas State University, were planted under a line source irrigation system at Yuma, AZ. The soil was a Typic Calciorthid. Five common sorghum hybrids also were used as checks. In 1984 only 27 genotypes of both crops were studied. Canopy temperature of the genotypes was measured for 7 days starting 67 to 60 days after planting in 1983 and 1984, respectively. Using all the data from each crop, an overall regression of canopy minus air temperature (DT) onto the observed vapor pressure deficit (VPD) was computed. This linear regression relationship was interpreted as the general relationship between VPD and DT for a crop. Also, a linear model of individual DT on the observed VPD was computed for each genotype. This equation predicted DT (DT) at a given value of VPD for each genotype. The sensitivity of each genotype to change in VPD was obtained by regressing the observed DT on the DT from the first regression. The genotype having coefficients < 1.0 are interpreted as having lesser sensitivity to changes in VPD. The mean temperature of a genotype higher than the average mean temperature of all the genotypes is considered as warmer. Warmer genotypes and those less sensitive to changes in VPD produce viable heads furthest from an irrigation sprinkler source.
Use of the Diagnosis and Recommendation Integrated System with Alfalfa1
Authors: Russelle M. P. , Sheaffer C. C.
Published: July 2010

Improved means are needed to diagnose plant nutrient response to treatments. Our objective was to evaluate the sensitivity of two diagnostic techniques to irrigation, K fertilization, and harvest management of alfalfa (Medicago sativaL.). Comparison of forage concentrations of essential elements with critical values was not as useful in diagnosing the order of limiting nutrients as were Diagnosis and Recommendation Integrated System (DRIS) indexes. Several elements were present in the forage at concentrations below published critical levels, even at herbage dry matter yields of 13.9 Mg ha−1. The DRIS indexes reflected the general improvement in nutrient balance resulting from irrigation. Diagnoses based on DRIS indexes were not affected by harvest management, in contrast to the critical value approach. The relationship between the summation of absolute values of DRIS indexes and herbage yield was best described by a power function that incorporated a minimum index value at which yields were no longer limited by overall nutrient balance. The DRIS approach can effectively resolve nutritional responses of alfalfa to fertilizer and irrigation managements in the presence of differing harvest managements
Effect of Planting Date, Nitrogen Levels, Row Spacing, and Plant Population on Kenaf Performance in the San Joaquin Valley, California1
Authors: Bhangoo M. S. , Tehrani H. S. , Henderson J.
Published: July 2010

Kenaf (Hibiscus cannabinus L.) is an annual fiber crop whose stems are a potential source of paper pulp. It can be grown under different climatic conditions resulting in a wide range of yield. Several studies in the southeastern USA have shown positive yield responses from higher plant populations. Effects of N on yield have been inconsistent. This study was conducted on a Hanford sandy loam soil (coarse‐loamy, mixed, non‐acid, thermic Typic Xerorthent) at California State University, Fresno, and was designed to investigate the effects of planting date (20 May, 20 June, 20 July 1981), row spacings (38 and 76 cm), plant population (86 450,172 900, and 345 800 plants/ha, 1980) and N (0, 45, 90, 135, and 180 kg N/ha, 1980‐1983) on the components of biological yield, basal stem diameter, and root growth of the cultivars, Tainung‐1 and a variation of Cuba‐2032. Total dry matter and stem yields were maximized at 345 800 plants/ha. Tainung‐1 resulted in higher stem yield than that of Cuba‐2032. Narrow row spacing (38 cm) resulted in higher yields than 76‐cm row spacing for both cultivars. Basal stem diameter was 2.3 cm for the lowest plant population and decreased to 1.63 cm for highest population. Cultivars and row spacings had no effect on stem diameter. Total dry matter yield was highest for the 20 May planting and decreased significantly with delayed plantings. Applied N at the rate of 135 and 180 kg/ha resulted in 71.0 and 83.5% increases in yield over the 0 kg N/ha rate. Nitrogen content in whole plants and leaf tissue increased, whereas the P and K content in whole plants decreased with an increase in applied N. Root growth increased with N rates up to 90 kg N/ha but was depressed at the 180 kg N/ha rate.
Influence of Soil and Applied Chloride on Several Wheat Parameters1
Authors: Fixen P. E. , Buchenau G. W. , Gelderman R. H. , Schumacher T. E. , Gerwing J. R. , Cholick F. A. , Farber B. G.
Published: July 2010

Previous field studies have indicated yield responses of small grain crops to KCl on very high K‐testing soils, which were likely due to Cl fertilization. Suggested mechanisms for the involvement of Cl range from plant disease effects to effects on plant water relations. The possibility that climatic and biological environment may interact with the Cl response could make plant and soil diagnostic relationships difficult to interpret. The objectives of this study were to determine the relationships of plant tissue and soil Cl concentrations to hard red spring wheat (Triticum aestivum L.) yield, and to examine possible interactions with plant diseases and water relationships. Field experiments at 14 locations over 3 yr were conducted on Typic Argiustolls, Pachic and Udic Haplustolls, and Pachic Udic and Udic Haploborolls. A critical plant Cl concentration of 1.5 g kg−1 for whole plants at head emergence assured 96% of maximum grain yield. Soil Cl levels > 43.5 kg ha−1 (60 cm) or 75 kg ha−1 (120 cm) were adequate for near‐maximum wheat yield. Both soil and plant Cl tests appeared to have potential as tools for diagnosing Cl responsive situations. Root and crown samples were taken at seven locations and rated for common root rot (Cochiobolus sativus). No influence of Cl on root rot was detected. Leaf rust (Puccinia recondita) and leafspot (complex of diseases) were suppressed at only one location by Cl addition. Leaf relative water content was measured at two locations and showed significant elvation due to Cl addition at both sites. The lack of detectable disease effects at some yield responsive sites and the good correlation between plant Cl concentration and yield response suggest that the beneficial effect of Cl was more general than disease reduction.
Yield and Nitrogen Yield of Sorghum Intercropped with Nodulating and Nonnodulating Soybeans1
Authors: Elmore R. W. , Jackobs J. A.
Published: July 2010

Nitrogen transfer between intercropped legumes and nonlegumes has not been consistently documented. However, N transfer between mixtures of nodulating (Rj1) and nonnodulating (rj1) soybeans (Glycine max (L.) Merr.) has been shown. A 2‐yr field study was conducted to examine the effects of intercropped nodulating and nonnodulating soybeans on sorghum [Sorghum bicolor (L.) Moench] yield and N yield, and N transfer. In both years, the soybean cultivar (cv.) Clark 63 (Rj1) and its rj1 isoline, L73‐1054, were planted at different distances between sorghum (‘DeKalb BR45+’) rows. Nitrogen rate was either 0 to 100 kg N/ha in 1979 and either 0 or 175 kg N/ha in 1980. The soil was a Cisne silt loam (mesic Mollic Albaqw in both years. Monocultures of both crops were also planted in both years. Sorghum N yield was 9% greater with Rj1 than with rj1 in 1979. This was due to increased N yield of sorghum associated with Rj1 in 0.4 m rows; soybean cv. had no effect on sorghum N yield in 0.8 m rows. Sorghum yield was not affected by soybean cv. Yields and competition of rj1 soybeans in 1980 were severely reduced by the hotdry growing season confounding N‐accumulation differences between rj1 and Rj1. However, from the 1979 results, we conclude that sorghum N accumulation was increased by association with Rj1 soybeans through N transfer, and that closer proximity of sorghum and soybeans enhanced this beneficial effect.