bluuebunny/crossref_metadata_2025 huggingface dataset:
Wheat Canopy Temperature: Relation to Plant Water Potential1
Authors: Ehrler W. L. , Idso S. B. , Jackson R. D. , Reginato R. J.
Published: July 2010

Drought‐induced stomatal closure causes a rise in canopy temperature that can be detected remotely by infrared thermometers. Remote sensing of such a rise could lead to large scale irrigation scheduling and improvements in yield forecasts, provided that the increase in canopy temperature is a reliable indicator of plant water stress. Plant water stress can be measured reliably and simply by determining the plant water potential (Ψplant). This experiment was undertaken to demonstrate that crop canopy temperature responds specifically to changes in Ψplant and therefore can be used for long term crop monitoring by remote sensing techniques.

The temperature difference between plant canopy and air (ΔT) was related to Ψplant, as shown by simultaneous, daily measurements of these parameters at 12 sites on six plots under different irrigation treatments. These data were obtained on clear days at predawn (just before sunrise) and 1400 hours. At predawn, Ψplant ranged from −2.0 bars in recently irrigated soil, in which the volumetric water content (θv) = 0.28, to −16 bars at the wilting point (θv = 0.15). At 1400 hours, Ψplant ranged from −15 bars when θv was 0.28 to −30 bars at the wilting point.

At 1400 hours, ΔT was −3.8 C at full plant hydration (Ψplant = −15 bars). Increasing drought decreased Ψplant progressively and increased ΔT accordingly: when Ψplant decreased to −19 bars, ΔT was zero; when Ψplant was −48 bars, ΔT increased to 4.8 C. In demonstrating the relationship between ΔT and Ψplant these results support the validity of the temperature difference method for sensing plant response to drought.
Straw Mulch Effects on Soil Temperatures and Sorghum Germination and Growth1
Authors: Unger Paul W.
Published: July 2010

The possibility that lower than normal temperatures in residue‐covered soils may affect crops has caused concern regarding the use of conservation tillage systems in some regions. To evaluate this possibility in the Southern Great Plains, soil temperatures were measured at a 10‐ cnl depth in field plots on which 0 (check), 1, 2, 4, m 12 metric tons/ha of wheat (Triticum aestivum L.) straw were applied on the surface. The soil was Pullman clay loam, a fine, mixed, thermic Torrertic Paleustoll (order Mollisol). Objectives were to determine the effects of mulch‐induced temperatures on grain sorghum [Sorghum bicolor (L.) Moench] planting dates, germination, emergence, and growth, and to obtain information concerning effects of mulch rates on soil temperatures at various seasons and under specified climatic conditions. Increasing mulch rates delayed the time that soil reached favorable temperatures for sorghum germination and growth. However, temperatures were near optimum before normal planting dates and, therefore, mulches did not affect sorghum germination and only slightly delated emergence. Since temperatures with high mulch rates rarely, if ever, reached the optimum for sorghum growth, plants on these plots grew slower early in the season than those on plots with low mulch rates. Later in the season, when soil water limited growth, plants on high mulch late plots grew more than on other plots because of higher water contents. Increased mulch rates decreased average soil temperature means, maximums, minimums, and standard deviations during all seasons of fallow front wheat harvest to sorghum planting. However, when temperature of bare soil approached or fell below 0 C, the temperature effect was reversed. The change in temperature for each metric tons/ha of mulch as compared with bare soil was greatest for the 1‐metric ton/ha rate and generally decreased as mulch rates increased.
Agronomic Cropping for Maximum Biomass Production1
Authors: Crookston R. Kent , Fox Carl A. , Hill David S. , Moss Dale N.
Published: July 2010

With recent widespread awareness of dwindling petroleum supplies, considerable attention has been directed towards plants as photosynthetic energy converters. The purpose of this 3‐year study was to investigate the bioproductivity of agronomic crops as a potential energy source in Minnesota. Experiments were conducted in the field at St. Paul on a Waukegan silt loam (Typic Hapludoll) and at Waseca on a Webster clay loam (Typic Haplaquoll). Both double‐cropping and monocropping systems were evaluated. The double‐cropping system consisted of growing fall‐planted winter rye (Secale cereale L.) at recommended seeding rates and harvesting it on 15 June, near the peak of its vegetative production and before the formation of acceptable grain. After the rye was harvested, the plots were fertilized, disked, and planted to corn (Zea mays L.). Three corn hybrids: ‘Pioneer 3780’ (full season), ‘NKPX74’ (14% more than full season), and ‘Pioneer 3030’ (28% more than full‐season) were grown at each of two populations that exceeded normal production populations by approximately 25% and 100% (75,000 plants/ha and 125,000 plants/ha). Corn was chosen to follow the rye for double‐cropping since, in a preliminary study, we determined that it produced more biomass than sorghum (Sorghum bicolor [L.] Moench) or sudangrass (Sorghum blcolor [L.] Moench) when grown on rye plots following the rye harvest. A corn‐only or monocropping system was established adjacent to the double‐cropping plots. The same three corn hybrids were grown at the same two populations, but they were planted as early in the season as possible and grew uninterrupted. Rye produced an average biomass yield (dry weight of aboveground portion) of 9.6 metric tons/ha (MT/ha) by 15 June. The largest average biomass yield from corn planted after the rye harvest (double cropped) was 16.3 MT/ha, produced by NXPX74 at 125,000 plants/ha. The rye plus corn double‐cropping yields thus averaged 25.9 MT/ha. The largest average monocropped corn yield of 18.8 MT/ha (produced by NKPX74 at 125,000 plants/ha) was 7.1 MT/ha below the double‐cropped yields. Due to interactions and yield fluctuations across environments, however, the two systems were not determined significantly different. Since costs and risks of successfully producing two crops per season would be an important consideration, we suggest that monocropped corn would be preferred over rye‐corn double cropping as a biomass production system in Minnesota.
Early‐Season Water Management for Cotton1
Authors: Grimes D. W. , Dickens W. L. , Yamada H.
Published: July 2010

Vegetative development of cotton (Gossypium hirsutum L.) in early season affects plant responses through the entire growth period. In the irrigated West, soils are usually irrigated before planting. With soils initially wet, scheduling a first irrigation is important to achieving desired plant growth and development. A 2‐year field study was conducted on contrasting soils to evaluate how first irrigation scheduling affected vegetative growth, maturity rate, and production.

Main stem elongation was stimulated by a lower plant water deficit in early irrigations. Although a delayed first irrigation slowed vegetative growth through mid‐June, when irrigations were normalized main stem elongation was accelerated well into the July and August fruiting period. Vegetative growth was frequently increased in the fruiting period by early first irrigations. Either early or late first irrigations delayed maturity.

A multiple regression model used to express relative yields (R2 = 0.72) had as independent variables the time of first irrigation (days after 30 April) and the water available to the plant in the top 61 cm of soil at planting. This yield equation predicted an optimum time for a first season irrigation from known soil water retention capability.
Growth and Nutrient Accumulation and Distribution in Wild Rice1
Authors: Grava John , Raisanen K. A.
Published: July 2010

Wild rice (Zizania aquatica L.) is a newly cultivated crop and its nutrient requirements are not well defined. To develop a sound fertilization program, a better understanding of the growth, nutrient uptake and distribution in the plant is essential. The purpose of this research was to investigate the dry matter, N, P, and K accumulation, and distribution pattern of wild rice throughout its growth cycle. This study utilized a portion of an NP factorial experiment conducted with K2 cultivar on peat soil (Terric Borohemist) in a grower's paddy in northcentral Minnesota. Plant samples were collected from six 3.7‐ ✕ 3.7‐m areas receiving 40, 19.7, and 55.7 kg/ha of N, P, and K, respectively. Dry matter accumulation and nutrient element concentration in various above‐ground plant parts wre determined at 10 growth stages. At the jointing stage, the second leaf was separated and analyzed for N, P, and K.

Although N, P, and K uptake preceded dry matter production, the accumulation patterns were similar. Accumulation rates were slow during the vegetative development phase, e.g., first 50 days after emergence. Following the jointing stage, during a 30‐day period of rapid growth, the plant accumulated over half of its dry matter and plant nutrients. Accumulation of plant nutrients continued at a relatively rapid rate until maturity. The effectiveness of topdress N application at jointing is partially explained by data indicating that wild rice accumulated 70% of its total N during flowering and grain formation. The second leaf at jointing contained 3.83% N, 0.55% P, and 3.73% K.

A single plant produced 30 g of total dry matter and took up 300 mg N, 110 mg P, and 740 mg of K. The grain contained 38, 22, and 3% of the total amount of N, P, and K, respectively, taken up by the plant. Nearly 85% of total K accumulated in stems. In this study, wild rice produced nearly 11,800 kg/ha of dry matter and contained 120, 40, and 290 kg/ha of N, P, and K, respectively. A major portion of nutrient elements was supplied by the soil.
Role of Inoculation in Establishing Subclover on California Annual Grasslands1
Authors: Jones M. B. , Burton J. C. , Vaughn C. E.
Published: July 2010

Subclover (Trifolium subterraneum L.) has been difficult to establish in California annual grasslands even with approved cultural, inoculation, and fertilization practices. Symptoms indicated a Rhizobium insufficiency. The objectives of this study were to develop dependable inoculum and methods of establishing annual clovers in northern California. Rhizobia were isolated from nodules of vigorous clover plants growing among plants showing extreme N‐deficiency symptoms. These rhizobia were screened in growth chamber tests for effectiveness and competitiveness against native ineffective rhizobia. The best strains were further tested in the field with several stickers and seed coating materials, and were compared with commercial inoculants available at the time. In the field tests rhizobial strains differed in ability to compete with ineffective native rhizobia and in ability to survive the long summer drought. In composites, poor or moderately effective rhizobial strains reduced the effectiveness of the good strains. Subclover growth increased in field experiments as the amount of inoculum was increased, indicating that high rhizobial numbers were important. Peat inoculum applied with 40% gum arabic solution as a sticker and a lime coating was much superior to peat inoculum applied as a water slurry. Vacuum‐inoculation treatment gave no better results than uninoculated seed. The effectiveness of inoculation sticker materials fell generally in the following order: “PELGEL‐PELINOC” > gum arabic‐lime > methyl‐cellulose‐lime > sugar lime.
Effects of Overirrigation on Growth and Quality of Alfalfa1
Authors: Peterschmidt N. A. , Delaney R. H. , Greene M. C.
Published: July 2010

Irrigation in excess of field capacity has long been recognized as a problem in the intermountain western U.S. Priority water rights and gravity flow systems provide cheap water in this region. In addition, there is a lack of adequate information concerning consequences of over irrigation on specific crops.

A field study on the effects of five irrigation regimes on growth and quality of ‘Thor’ alfalfa (Medicago sativa L.) was conducted near Riverton, Wyoming, from 1974 through 1976. Irrigation levels were: 1) 90% of the available soil moisture depleted (AMD) and irrigated to field capacity (FC), 2) 50% AMD and irrigated to FC, 3) 10% AMD and irrigated to FC, 4) 50% AMD and irrigated to twice FC, and 5) 50% AMD and irrigated to four times FC.

Irrigation to two and four times FC reduced plot forage yield 1.26 and 1.97 metric tons/ha/year, respectively, compared to the driest treatment yield. Reduced yield did not result from a decrease in stand density. Further, high irrigation levels increased alfalfa forage P content and had no effect on percent of in vitro dry matter digestibility and percent protein.

These data provide practical field collected information on effects of Overirrigation on alfalfa production as necessary justification for alternative decisions on irrigation.
Relationship Beween Soybean Seed Vigor and Yield1
Authors: Egli D. B. , TeKrony D. M.
Published: July 2010

The relationship between the vigor of soybean [Glycine max (L.) Merr.] planting seed and yield of the resulting crop has not been clearly determined. Studies were conducted in 1975, 1976, and 1977 to evaluate the relationship between seed vigor and yield in soybeans by experimental techniques that duplicate as closely as possible practices followed by commercial producers of soybeans. The cultivars ‘Cutler 71’ and ‘Kent’ were used in 1975 and 1976, and ‘Williams’ and Kent in 1977. Three to six lots of seed of each cultivar were selected to provide a wide range in seed vigor and maintain a high viability (standard germination). Two seeding rates were used, 16 and 33 viable seed/m (13 and 26 viable seed/m in 1977) in 3‐row plots with 76 cm between the rows (66 cm in 1975).

Standard germination of the 27 lots included in the experiment ranged from 77.0 to 98.5% and averaged 90%. The 4‐day germination was closely related to the standard germination but averaged 6.3 percentage points lower. The accelerated‐aging germination averaged 69.5% and ranged from 18.0 to 97.5%. Field conditions at planting were near optimum and field emergence was high for all seed lots in all 3 years of the experiment. Thus, there was no relationship between seed vigor and emergence or final stand, regardless of cultivar or planting rate. Seed vigor had no effect on yield regardless of cultivar or planting rate. In the absence of stand differentials, there appears to be no yield advantage associated with the utilization of high vigor planting seed.
Ameliorative Role of Zn, K, and Gypsum on Maize Growth under Alkali Soil Conditions1
Authors: Shukla U. C. , Mukhi A. K.
Published: July 2010

Information is needed on the ameliorative role of Zn in relation to gypsum and K on plant growth under alkali soil conditions. A greenhouse experiment was conducted, growing maize (Zea mays L.) as an indicator crop for 45 days. Treatment combinations of three levels of Zn (0, 5, 10 ppm), and three levels of K (0, 50, 250 ppm) were superimposed on a normal, an alkali, and a gypsum‐treated alkali soil.

Shoot dry matter yield in alkali soil was only 35% of the normal soil. The application of 5 ppm Zn, 250 ppm K, and gypsum to the alkali soil resulted in the recovery of yield to 91, 75, and 70% of that obtained in the normal soil. The highest yield was recorded with the application of 10 ppm Zn, 250 ppm K, and gypsum to the alkali soil, which was 14 and 59% more than normal, and Zn‐treated alkali soils, respectively. The magnitude of Zn and K response in alkali soil was less after gypsum treatment. Responses to the above nutrients were also negligible in the normal soil.

Zinc concentration decreased under alkali soil conditions. Gypsum and K enhanced Zn utilization by the plans. Shoot Na was highest in the alkali, and lowest in the normal soil. Zinc decreased Na. The highest decrease was in the alkali soil. An application of 250 ppm K also decreased Na. The effectiveness of Zn, K, and gypsum treatments in decreasing Na concentration was diminished when any of the above two treatments were applied together.

The highest shoot K was in the normal soil, and was similar in the alkali and gypsum‐treated soils. The highest increase in shoot K with K was in the alkali and gypsum‐treated alkali soils. Zinc decreased shoot K in the alkali soil. Shoot Ca decreased with Zn or K in the normal soil, but increased in the alkali, and at their low levels in the gypsum‐treated soil. Interrelationships between Na, Zn/K, and Ca, showed decreased effectiveness when applied together, on Ca concentration. Accumulation of shoot Mg was more in the alkali than in other soils when K or Zn were not applied. The antagonism between K and Mg was evident. Antagonism between K and Ca in relation to Mg concentration was also noted.

The yield increase in alkali soil with Zn was associated with the enhanced uptake of Zn and Ca, decreased concentration of Na, and widening of Ca/Na and K/Na ratios. The increase in yield with K, and gypsum treatments was also greatly associated with the enhanced uptake of Ca and other plant nutrients.
Effect of Population Density, Planting Date, and Genotype on Plant Growth and Development of Cotton1
Authors: Galanopoulou‐Sendouka Stella , Sficas A. G. , Fotiadis N. A. , Gagianas A. A. , Gerakis P. A.
Published: July 2010

Previous work has suggested that a very dense cotton (Gossypium hirsutum L.) population may be superior to the conventional one, especially in marginal regions for cotton production, like Greece. Three population densities (100, 50, and 25 cm between rows with 10 cm within row spacing), three planting dates in 1974 and two in 1975, and three varieties were used in an experiment carried out at Sindos, Greece, to investigate the effect of the above factors on growth and development of cotton.

Planting date and density differentiated growth and development greatly. The influence of planting date was strongest on earliness, while density affected most morphological characteristics and yield components. Early sowing overcame the effect of reduced and prolonged seedling emergence, produced earliness and increased yield, particularly in the shorter growing season of 1974. Late planting dates were inferior in flowering rate, maturation rate index, flower and boll number, boll weight, yield, lint percentage, and Micronaire index.

Increasing density reduced individual plant growth and productivity. However, in per unit land area, there was higher total dry matter production, earlier and more abundant foliage and fruiting, but not a proportional increase of economic yield and earliness. The very dense plants showed lower efficiency of leaves, higher fruit shedding, and smaller boll size. Medium density compared to high density was more consistent in earliness and high yield.

No significant interaction between density and planting date was found for yield. Considering earliness, the superiority of high densities was reduced under late planting. The relative performance of the three cultivars was not substantially affected by population density and planting date.
Response of Several Sugarbeet Cultivars to N Fertilization: Yield and Crown Tissue Production1
Authors: Halvorson A. D. , Hartman G. P.
Published: July 2010

The level of plant available N greatly affects sugarbeet (Beta vulgaris L.) quality, sucrose production, and the amount of lower quality crown ussue produced. The response of several sugarbeet cultivars to N fertilization was studied in 1977 and 1978 to determine: i) what level of available N was needed by each cultivar to maximize sucrose production; ii) if each cultivar would respond similarly to N fertilization; and iii) if crown tissue production varies with cultivar. Nitrogen rates from 0 to 448 kg/ha were used as main plots with three to five commercially‐grown sugarbeet cultivars as subplots in the study. Root and sucrose yield, sucrose content, clear juice purity, and crown tissue production were determined for each treatment. All sugarbeet cultivars tested responded similarly to increasing levels of available N with crown tissue growth increasing linearly, sucrose content and clear juice purity decreasing linearly, and whole root yield increasing curvilinearly. Addition of some N fertilizer was needed to maximize sucrose production; however, as the level of N fertilization increased above the N level needed for maximum sucrose production, sucrose production decreased. Root tissue growth and sucrose production were maximum at the same N level, but maximum sucrose production did not coincide with maximum whole root yield. Sucrose production was maximum at the same N level for all cultivars. Thus, sugarbeet producers need not vary N fertilizer rates for each sugarbeet cultivar grown. However, total amount of sucrose production per unit area and crown growth did vary with cultivar. At optimum N fertilization, crown tissue accounted for 12 to 17% of the whole root yield, depending on year and cultivar grown. Results of this study indicate that N fertilization influences sugarbeet quality, crown tissue production, and level of sucrose production more than does sugarbeet cultivar.
Effect of Mid‐ to Late‐ Season Water Stress on Sugarbeet Growth and Yield1
Authors: Carter J. N. , Jensen M. E. , Traveller D. J.
Published: July 2010

Costs of irrigation (labor, water, and energy) and sometimes limited‐late‐season water are factors associated with the choice of crop and economic returns. Sugarbeets (Beta vulgaris L.) have shown certain tolerance to water stress, therefore the objective of this study was to evaluate growth rates and characteristics, sucrose accumulation, and N uptake by sugarbeets grown under mid to late‐season soil water deficit and plant water stress.

Sugarbeets were grown in a field experiment on a Portneuf silt loam soil (Durixerollic Calciorthids; coarsesilty, mixed, mesic) under normal irrigation until 15 July, after which further irrigation was terminated or reduced on two treatments during a 2‐year period. Root yield, sucrose concentration, sucrose yield, plant N uptake, and petiole NO3‐N were determined from samples taken throughout each season. These experiments demonstrated that very little, if any, sucrose yield reduction can be expected in the Idaho area if irrigations are discontinued after filling the soil profile with water about 1 August and if the soil contains at least 200 mm of available water to a soil depth of 160 cm. During dry years, there may be an advantage to applying a light irrigation about 1 month after water cutoff and to have sufficient surface soil water present at harvest to prevent loss of roots by breaking. Use of deficit water management during August, September, and October curtailed leaf growth, reduced leaf area when no longer needed, reduced N uptake from the soil, increased sucrose concentration in the beet root, and decreased fresh root yield. These effects on yields were mainly caused by dehydration of the beet tops and roots so sucrose production was scarcely affected even though only 70% of the normal irrigation water was applied. Limited irrigations reduced evapotranspiration rates because of drier surface soil and partial stomatal closure, thereby decreasing the rate of water extraction from the soil reservoir by the plant. Use of mid to late‐season deficit water management could substantially reduce sugarbeet production costs in irrigated areas and economically benefit the consumer, producer, and manufacturer.
Yield and Quality of Alfalfa Harvested During Autumn and Winter and Harvest Effects on the Spring Crop1
Authors: Collins Michael , Taylor Timothy H.
Published: July 2010

The production of pasturage is insufficient to meet the needs of grazing animals during autumn in mid‐latitude states of the eastern U.S. The possibility for use of perennial forage legumes after frost has not been studied.

The object of this experiment was to gain information concerning the yield and quality during autumn and winter of alfalfa (Medicago sativa L.) produced during late summer and early autumn and to determine the effects of such harvests on spring growth and yield.

In replicated field plot experiments, we measured alfalfa yield, forage quality, root reserves and spring growth for two seasons. Stockpiling periods started in early August and early September with an array of harvests during autumn and winter.

Two‐year average yields were 1,520 and 892 kg/ha on 1 November for growth made from early August and early September, respectively. The loss of a potential hay harvest must be considered when August stockpiling is contemplated. Forage quality declined during autumn due largely to leaf drop and stem death. On 1 November, alfalfa stockpiled from early August was significantly lower in leaf percentage, N and P concentration, and in vitro dry matter disappearance (IVDMD) than that stockpiled from early September. Forage IVDMD decreased from 59.1% to 45.4% between 15 October and 15 November for alfalfa stockpiled from early August but remained about the same, 69.9 to 70.0 for alfalfa stockpiled from early September. Crude protein (CP) generally and Ca always exceeded beef cow requirements while P and Mg concentrations declined below requirements regardless of stockpiling period. Supplementation of energy, P, and Mg would be necessary during late autumn and winter. Harvests on or after 1 November generally did not reduce root carbohydrate reserves and, with one exception, did not reduce first harvest yield in the following year, indicating that grazing or clipping could occur after that date at this location.

Acceptable yields of quality forage were produced during a 6 week or longer period in late summer and autumn. This forage could be utilized by mid‐November with little reduction of the following spring crop.
Establishment of Alfalfa by Conventional and Minimum‐Tillage Seeding Techniques in a Quackgrass‐Dominant Sward1
Authors: Mueller‐Warrant G. W. , Koch D. W.
Published: July 2010

Minimum‐tillage establishment of forages offers potential advantages over the conventional method in terms of reducing energy and labor requirements, erosion hazard, and improving flexibility, and timeliness of operation. Our objective was to compare these methods of establishing alfalfa (Medicago sativa L.) with various herbicides, time intervals between herbicide application and seeding, and seeding dates. The seedings were established on a Charlton fine sandy loam (Entic Haplorthod) of high fertility in a sward dominated by quackgrass (Agropyron repens L.). Conventional renovation consisted of plowing, disking, cultipacking, and seeding; minimum‐tillage renovation consisted of mowing and seeding with a J. D. Powrtill seeder.

Delaying application of glyphosate IN‐(phosphonomethyl) glycine] from 2 to 16 May had no apparent effect upon quackgrass control, but did lead to a significant reduction (52%) in densities of alfalfa seedlings and, subsequently, of second year alfalfa plants in plots seeded 21 May 1977 by minimum‐tillage. At the first harvest of the seeding year, a delay in glyphosate application resulted in significantly lower forage yield (1.84 vs. 2.82 metric tons/ha) and higher percent crude protein (20.0 vs. 16.8%) for the 21 May and 4 June minimum‐tillage seedings. In subsequent harvests, there were no yield differences due to glyphosate application date for alfalfa established by minimum‐tillage. Date of glyphosate treatment did not affect plant densities, forage yield, or quality of conventionally‐seeded alfalfa.

For glyphosate treatments, conventional seeding resulted in an average of 0.6 metric tons/ha more alfalfa than minimum‐tillage during the seeding year. Yields of total forage and alfalfa seeded by the two techniques after glyphosate treatment were similar during the second year, except that yields for conventional seeding continued to be higher than for minimum‐tillage for the 4 June seeding (9.2 vs. 8.5 metric tons/ha of alfalfa).

In terms of alfalfa and total forage yields, glyphosate was more important for minimum‐tillage than for conventional seedings. EPTC (S‐ethyldipropylthiocarbamate) produced yields similar to glyphosate with conventional seeding, while with paraquat (l,l'‐dimethyl‐4,4'‐ bipyridinium ion) yields were similar to those with glyphosate only at the earliest minimum‐tillage seeding. Seeding without herbicide led to substantial yield reductions, especially with minimum‐tillage seedings.
Forage Quality of selected Warm−Season Weed Species1
Authors: Bosworth S. C. , Hoveland C. S. , Buchanan G. A. , Anthony W. B.
Published: July 2010

Although weeds are a common component of pasture, hay, and silage, limited information is available on forage quality of warm−season weeds. Forage quality of 17 warm−season weeds and two cultivated forage species seeded in pure stands was determined at vegetative, flowering, and fruiting development stages to ascertain nutritive value for ruminants. At the vegetative stage, 16 of the 17 weed species had greater in vitro dry matter digestibility (IVDMD) than ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.] or ‘Millex 23’ pearlmillet [Pennisetum typhoides (Burm) Staph & C. E. Hubb.]. The majority of forbs had crude protein (CP) concentrations of 20% or more at the vegetative stage. Generally, IVDMD declined as plants matured. Some grass weeds were lower in CP and comparable to pearlmillet and bermudagrass. Crude protein concentrations generally declined as plants matured. All weed and forage species had nutritionally adequate amounts of Ca, Mg, and K. Phosphorus levels were sub−optimum for high producing ruminants in seven forbs and had high Ca:P ratios which could cause metabolic disorders in ruminants if used as a sole feed source. Many of these warm−season weed species at the vegetative stage can offer ruminants a nutrient level comparable to that of cultivated grasses such as Coastal bermudagrass and pearlmillet.
Phosphorus Requirements of Soybean and Cowpea as Affected by Mode of N Nutrition1
Authors: Cassman K. G. , Whitney A. S. , Fox R. L.
Published: July 2010

A field experiment was conducted on a tropical soil (Humoxic Tropohumult) with a high P sorption capacity to compare the critical external and internal P requirements of soybean (Glycine max (L.) Merr.) and cowpea (Vigna unguiculata (L.) Walp.) as affected by the predominant mode of N nutrition during crop growth. The experiment had a split‐plot design with two N‐level subplots established within each of six P‐level mainplots. Phosphorus treatment ranged from 0.0015 (unamended soil) to 0.08 (1,880 kg P/ha) µg P/ml in 0.01M CaCl2 solutions equilibrated with soil for 6 days. Nitrogen levels were either deficient (plants primarily dependent on N fixation) or sufficient (N fertilizer supplied at rates sufficient to satisfy the crop N requirement). Nitrogen‐fixing soybeans required 750 kg P/ha to obtain a 90% relative yield which was 320 kg P/ha more than that required by N‐supplied plants to obtain a comparable relative yield. The P concentration of N‐fixing soybean plants was significantly lower than that of N‐supplied plants at all levels of applied P fertilizer. The external P requirement and tissue P concentration of cowpea were unaffected by soil N level. The data show that cowpea was more tolerant of P stress than soybean, especially when dependent on N fixation. The cowpea cultivar grown without P or N fertilizer yielded 72% of the maximum yield obtained at optimum P levels while the comparable relative yield for the soybean cultivar was 28%. We conclude that (i) some N‐fixing grain legumes can make respectable yields with little or no P fertilizer while others might not and, (ii) screening N‐fixing grain legumes for tolerance to nutrient stress should be conducted on N‐deficient soil to Insure that nutritional requirements are assessed for the N‐fixing plant, especially on the highly weathered soils of the tropics.
Aluminum Tolerance of Triticale and Wheat Cultivars Developed in Different Regions1
Authors: Mugwira L. M. , Sapra V. T. , Patel S. U. , Choudry M. A.
Published: July 2010

The differential tolerance of crop varieties to high Al is often related to the amounts of labile Al in the soils in which the plants were developed. The objective of this study was to evaluate the Al tolerances of triticale (X Triticosecale, Wittmack) and wheat (Triticum aestivum L.) developed in different regions. Twenty‐seven triticale and 37 wheat cultivars were tested in growth chambers and under greenhouse conditions for Al tolerance in 1/5‐strength Steinberg solution containing 0 or 6 ppm Al, highly Al‐toxic Bladen soil ((Typic Albaquult), and mildly Al‐toxic Dothan soil (Typic Paleudult). The Bladen soil had a pH of 4.6 and KCl‐extractable Al of 3.75 me.e/100 g. The corresponding values for the Dothan soil were 4.5 and 1.45, respectively. Each cultivar was also grown in soils limed to pH 5.8. The relative root lengths (A1/no A1) of two triticale and six wheat checks in the nutrient solutions were correlated to their relative top growth (unlimed/limed) in the Bladen soil but not in the Dothan soil. When grown in nutrient solutions, Al tolerance of the triticales followed the order Canada and Mexico > California > Alabama > Oregon while in the Bladen soil Alabama triticales had higher Al tolerance than Canadian triticales. On the average, Brazilian wheats had higher A1 tolerance than U.S. wheats. Wheat varieties from Indiana and the Plains States were more sensitive to A1 than those developed in the Eastern States. There were large differences in the A1 tolerances of triticale cultivars from each region probably reflecting differences in the A1 tolerances of the parent species. More work should be conducted with triticales from stable and non‐segregating lines.
Seasonal Nitrogen Fixation and Dry Matter Accumulation by Peanuts1
Authors: Tonn W. H. , Weaver R. W.
Published: July 2010

Yield improvement of peanut (Arachis hypogaea L.) is partially dependent on N nutrition. The differential ability of peanut cultivars to fix N symbiotically and best utilize this N supply are traits that may be useful in plant breeding. Four peanut cultivars representing Spanish and Virginia subspecies var. vulgaris and var. hypogaea, respectively, were grown for 1 year on a sandy soil to determine seasonal patterns of nodulation, acetylene reduction, and N accumulation in pods, leaves, and stems. The two Virginia cultivars ‘Florunner’ and ‘Florigiant’ accumulated more N in vegetative organs than the Spanish cultivars ‘Tamnut 74’ and ‘Starr’. The Virginia cultivar also maintained a higher percentage N in the leaves throughout the season than did the Spanish cultivars. The Virginia cultivar tended to accumulate N in fruit at a faster rate than the Spanish cultivars. Nodule mass on the Virginia cultivars was more than 50% greater than on the Spanish cultivars at midseason. Acetylene reduction was also substantially higher for the Virginia cultivars at midseason. Conclusions are restricted because severe insect damage to plants terminated the experiment approximately 3 weeks before the normal harvest date. The result suggest that the Virginia cultivars have greater N fixing capability than Spanish cultivars.
The Influence of Sorghum‐Sudangrass Roots on Nutrient Leaching1
Authors: Long F. Leslie
Published: July 2010

An active root system can reduce leaching by taking up water and nutrients and transporting them to the aboveground portion of the plant, but little is known concerning the quantitative influence of roots on leaching. This study was conducted to determine the influence of sorghum‐sudangrass (Sorghum bicolor [L.] Moench ✕ S. sudanense (Piper) Stapf) roots on the movement of NO3, K, Ca, and Mg in a simulated field soil profile of Dothan loamy sand (Plinthic Paleudults) in the Auburn rhizotron.

Two rates of N (250 and 500 kg/ha) and one rate of K (63 kg/ha), Ca (50 kg/ha), and Mg (25 kg/ha) were applied. Nutrient movement was monitored by analysis of soil solution samples taken at 48 to 72‐hour intervals over a 132‐day period from depths of 20, 40, 60, 80, 100, 120, 140, and 180 cm. Soil water status was determined by tensiometers and the neutron‐scattering technique. Rainfall and supplemental irrigation maintained soil water tension generally less than 0.3 bar. Sorghum‐sudangrass roots proliferated the soil profile to 160 cm and reached a maximum density of 3 cm root length per cm8 of soil in the Ap horizon, with lesser amounts in the A2 and B horizons. Roots took up NO3 and did not allow any appreciable leaching below 80 cm at 250 kg of N/ha or below 100 cm at 500 kg of N/ha. Root uptake of K was sufficient to prevent any appreciable accumulation of K at any depth measured. Uptake of Ca and Mg was sufficient to virtually prevent leaching of these nutrients below 40 cm at 250 kg of N/ha or below 80 cm at 500 kg of N/ha. From the results of this study, it is evident that nutrient leaching through soil can be virtually eliminated by the natural mechanism of root uptake, thereby preventing any possible pollution of groundwater.
Glyphosate Timing Effects on Establishment of Sod‐Seeded Legumes and Grasses1
Authors: Welty L. E. , Anderson R. L. , Delaney R. H. , Hensleigh P. F.
Published: July 2010

Sod‐seeding establishment of small‐seeded legumes and grasses has great potential for increasing forage production on previously non‐tillable lands. However, consistently successful stand establishment has been difficult to achieve via sod‐seeding. Even when adequate stands are obtained, they often lack the vigor associated with conventional establishment. A delay between the spraying of a non‐selective chemical for sod control and seeding with a minimum‐till drill has been suggested to improve sod‐seeding stand establishment. We conducted two field experiments to determine the optimum time interval needed between spraying glyphosate [N‐(phosphonomethyl) glycine] and sod‐seeding various grass and legume species with minimum‐till drills. The soils were classified as Cumulic Haploborolls and Ustic Tomfluvents in the first experiment and Udic Haploborolls and Typic Eutrochrepts in the second.

A 14 day interval between spraying glyphosate and sodseeding alfalfa (Medicago sativa L.), alsike clover (Trifolium hybridum L.), and tall fescue (Festuca arundinacea Schreb.) with either the John Deere Powr‐till drill or the Melroe 701 No‐till drill was needed for adequate establishment at Laramie, Wyoming in 1978. In 1979, a 7 to 14 day spray‐plant interval was needed for adequate establishment of alfalfa, alsike clover, creeping meadow foxtail (Alopecurus mundinaceus Poir.), and meadow bromegrass (Bromus biebersteinii Roem. & Schult.) when seeding with the John Deere drill. When seeding with the Melroe drill in 1979, no differences among spray‐plant intervals were obtained for the same species.

At Kalipell, Montana in 1978, a 28 day delay between spraying glyphosate and sod‐seeding alfalfa with the John Deere drill was needed for adequate establishment; whereas ladino clover (Trifolium repens L.) required a 14 day interval between spraying and seeding. In 1979 at Kalispell, a 28 day spray‐plant interval was needed for adequate establishment of alfalfa. Ladino clover establiihment was very poor for all spray‐plant intervals. Inadequate legume establishment was associated with slug (Agriolimax reticulatum Müller) predation. Spraying 28 days prior to seeding allowed sufficient time for grass desiccation. This permitted sunlight to penetrate the canopy which dried out the furrow thereby providing a less favorable slug environment.
Determining Soil‐Induced Plant Water Potential Depressions in Alfalfa by Means of Infrared Thermometry1
Authors: Idso S. B. , Reginato R. J. , Reicosky D. C. , Hatfield J. L.
Published: July 2010

To ascertain the ability of a remote sensing technique to evaluate the soil‐induced component of plant water potential depressions in forage crops, field experiments were conducted to measure the air vapor pressure deficit and foliage‐air temperature differentials of well‐watered alfalfa (Medicago saliva L.) at five different sites throughout the United States. At two of these sites, data were also acquired for various degrees of stressed alfalfa along with concurrent measurements of total plant water potential. The temperature and vapor pressure data were used to construct a plant water stress index which was related to the plant water potential. Different results were obtained for the two sites studied; but after a procedure was developed to remove variable atmospheric effects, the remaining soil‐induced plant water potential depressions were found to be well described by a single function dependent upon the plant water stress index. These results demonstrate the ability of surface temperature measurement by means of infrared thermometry to rapidly assess large areas of cropped land for plant water potential depressions arising from shortage of soil moisture.
Grain Yields, Soil Water Storage, and Weed Growth in a Winter Wheat‐Corn‐Fallow Rotation1
Authors: Hoefer R. H. , Wicks G. A. , Burnside O. C.
Published: July 2010

This research involves factors affecting crop production in a no‐till crop rotation of winter wheat (Triticum aestivum L.)−corn (Zea mays L.)−fallow. Experiments were conducted in the field at North Platte, Nebr. during 1974 to 1977 on a Holdrege silt loam (fine−silty, mixed, mesic Typic Argiustolls) to determine the effect of weed control in growing winter wheat and stubble after harvest on annual weed growth, soil water storage, and winter wheat and corn yields. Winter wheat was an excellent competitor to weeds. Winter wheat allowed to grow until harvest (10 July) reduced weed weight taken 7 weeks after harvest (1 September) 56% as compared with plots where winter wheat and weeds were removed on 22 May. Weed competition reduced winter wheat yields by 15% in 1975 but not in 1976 when weeds succumbed to drought and competition from winter wheat. Glyphosate [N−(phosphonomethyl)glycine] applied after winter wheat harvest did not immediately kill weeds which resulted in unnecessary soil water loss when compared to plots receiving tillage. Volunteer wheat and weeds emerged after an application of glyphosate or one tillage after harvest. A residual herbicide should be applied to prevent these weeds from using soil water. Weeds in plots that were allowed to produce viable seed in the winter wheat or in the stubble after harvest significantly reduced weed control in corn planted the following spring as compared with plots in which weeds were not allowed to produce viable seed. Escaped weeds that produce seed during any period of a crop rotation will provide competition to subsequent crops. Standing stubble trapped snow which increased corn yields as compared to plots where tillage had knocked stubble down. Removal of winter wheat stubble after corn planting caused less brace root penetration, more lodging. and reduced corn yields 15% as compared to plots where stubble was left undisturbed.
Fallow Systems for Winter Wheat in Western Nebraska1
Authors: Fenster C. R. , Wicks G. A.
Published: July 2010

The need for conservation of soil and water and the energy situation makes it imperative to develop more efficient fallow systems for controlling weeds, to utilize moisture efficiently, and maximize wheat production under limited rainfall.

Research was conducted at North Platte and Sidney, Nebr. from 1972 through 1977 to develop a weed control program in a limited and no‐tillage winter wheat (Triticum aestivum L.)‐fallow rotation. The experimental areas in fallow were sprayed with glyphosate [N‐(phosphonomethyl)glycine] at 0.8 kg/ha after harvest to eliminate soil water loss from existing weeds in wheat stubble. Six tillage and/or herbicide treatments were applied to separate replicated plots the first few days of August, October, and April.

Atrazine [2‐chloro‐4‐(ethylamino)‐6‐(isopropylamino)‐s‐triazine] + glyphosate at 0.8 + 0.8 kg/ha at Sidney and 1.3 + 0.8 kg/ha at North Platte was the most effective fallow weed control treatment but allowed too much weed growth 65 and 77 Mg/ha, respectively. Downy brome (Bromus tectorum L.) control at North Platte was unsatisfactory with August application of atrazine which left 40 plants/m2. Russian thistle (Salsola kali L. var. tenuifolia Tausch) and volunteer winter wheat were not always controlled in April by herbicides that were applied in August or October. The earlier the herbicides were applied during the fallow period the sooner subsequently emerging weeds appeared the following spring. Tillage reduced wheat residues 42% at Sidney and 78% at North Platte when compared to the no‐tillage plots. April tillage at North Platte had less weed growth because August and October tillage planted volunteer wheat and downy brome. Plots treated with residual herbicides stored 24 and 21% more soil water at Sidney and North Platte than tillage treatments. Wheat yields were increased 11% on no‐till plots only at North Platte when compared to tillage. Grain yields were not significantly different when comparing time of initial fallow treatments.
Influence of Mycorrhizae on the Mineral Contents of Cowpea and Soybean Grown in an Oxisol1
Authors: Yost R. S. , Fox R. L.
Published: July 2010

Cowpea (Vigna unguiculata) and soybean (Glycine max) were grown in the field on a Tropeptic Eutrustox which, for a period of 8 years, had been maintained at 10 different soil P levels by appropriate P fertilizer applications. Effects of methyl bromide fumigation of the soil on mycorrhizal infection and concentrations of P and other nutrients in the plants were compared. Plants grown on nonfumigated soils with soil P levels below 0.025 to 0.05 mg P/liter contained higher Ca and K percentages than plants grown on fumigated, low P‐status soils. Differences in Ca and K percentages in the plants were more closely related to crop growth rates than to vesicular arbuscular mycorrhizal infection levels. Differences in Ca and K percentages were small. In contrast, silicon percentages of mycorrhizal soybean plants were 0.5 to 0.9% Si while non‐mycorrhizal plants contained 0.2 to 0.3% Si. The pattern of Si percentages at different levels of soil P was different from that of other nutrients. The levels of Si in mycorrhizal soybean plants were greater than in non‐mycorrhizal plants at all levels of soil P, while with other nutrients, differences diminished with increasing soil P level. Crop growth rate and P absorption strongly affected the percentage composition of other nutrients with the notable exception of Si. If mycorrhizae consistently enhance Si uptake by plants such as soybean then Si uptake may indicate mycorrhizal activity. Silicon content of cowpea, however, was not altered by the presence or absence of mycorrhizae.
Growth and Yield Response of Chile Pepper to Trickle Irrigation1
Authors: Beese F. , Horton R. , Wierenga P. J.
Published: July 2010

Optimizing rates of water application to irrigated crops is an important method for conserving water in arid areas. Trickle irrigation is one method of applying water to crops with minimal losses. This field study was conducted to determine chile (Capsicum annuum L.) growth and development when irrigated by trickle irrigation at different levels of water application. Chile peppers were grown on a 2‐ha field irrigated with a trickle irrigation system. Water application rates of 0.8, 1.2, and 1.4 times a control treatment were maintained from mid‐June (74 days after emergence) to maturation in September. Throughout the growing season measurements were made of leaf area index, and of the accumulation of dry matter in stems, leaves, roots, and pods. The data show a clear response of the rate of leaf area development and dry matter production to water application rates. From the start of treatments the dryer treatments had lower rates of leaf area development and dry matter production, resulting in lower final yields of above and below ground plant parts. However, water use efficiencies varied little and were between 8.1 and 8.2 cm actual ET per ton of dry mass production. The results indicate that limiting the water applied to chile during the period of rapid vegetative growth reduces final yield, but has limited effect on water use efficiency.