Tiling Research Project

During the 1990s, southern Iowa producers faced several years of wet growing seasons. Many producers were forced to abandon wet fields in 1992 and 1993 and yields were reduced in 1996, 1998, and 1999 from late planting due to wet soils. Drainage classifications of soils in southern Iowa range from poorly drained to moderately well drained. Most efforts at draining soils have been aimed at surface drainage. Little effort has been made to drain the southern Iowa soils using the subsurface drainage tile common in other areas of the state. Many producers feel that the effects of pattern tiled, subsurface drainage would be short-lived and not effective on southern Iowa’s heavy clay soils. The pattern tile is also expensive. Little research has been conducted on the effects of subsurface drainage on southern Iowa soils using modern plastic tile, Global Positioning Systems (GPS), Geographical Information Systems (GIS), and laser-guided installation. The purpose of this project was to examine the long-term effects of subsurface, pattern tiling on yield, duration, and economics in southern Iowa soils

SDS shows up in early summer

Sudden death syndrome (SDS) generally strikes soybean around the middle of August in Iowa. Because of the unusual weather this growing season, the disease is showing up much earlier and was reported last week from several southern Iowa counties. The fields that we visited last week had several disease patches in poor drainage areas. Plants in these areas showed intervienal necrosis on leaves and root rot symptoms. The lower portion of stems, when they were split, was gray. In some plants, bluish fungal colonies could be seen on the roots, but these colonies were not as common as in plants later in the summer. Phytophthora root and stem rot also was coexisting with SDS in these fields

Diagnosing Stewart\u27s disease in field corn

Two commercial cornfields in south central Iowa were diagnosed with Stewart\u27s disease the week of May 22. Although commercial field corn does show variable tolerance to the disease and widespread economic loss is not likely, these fields are proof that the disease can infect some hybrids. Even among exposed plants within a given hybrid, some may be infected and others may not. In one field south of Albia, 2 percent of plants had been killed, 12 percent showed classic leaf symptoms, and 86 percent were symptomless. The fields with infected plants will be monitored as the season progresse

Phytophthora race 25 and soybean 1k gene strategy

Soil moisture in many regions of Iowa is at field capacity or more so planting will occur in wet soils this spring. Wet soils increase the risk of damping-off in soybean by the fungi Phytophthora and Pythium. Seedling disease concerns are further compounded this year by low-to-poor seed quality. If damping-off occurs this year, growers may have difficulty finding soybean seed for replanting and may want to consider the following strategies for controlling Phytophthora and Pythium damping-off

On the measurement of a weak classical force coupled to a quantum-mechanical oscillator. I. Issues of principle

The monitoring of a quantum-mechanical harmonic oscillator on which a classical force acts is important in a variety of high-precision experiments, such as the attempt to detect gravitational radiation. This paper reviews the standard techniques for monitoring the oscillator, and introduces a new technique which, in principle, can determine the details of the force with arbitrary accuracy, despite the quantum properties of the oscillator. The standard method for monitoring the oscillator is the "amplitude-and-phase" method (position or momentum transducer with output fed through a narrow-band amplifier). The accuracy obtainable by this method is limited by the uncertainty principle ("standard quantum limit"). To do better requires a measurement of the type which Braginsky has called "quantum nondemolition." A well known quantum nondemolition technique is "quantum counting," which can detect an arbitrarily weak classical force, but which cannot provide good accuracy in determining its precise time dependence. This paper considers extensively a new type of quantum nondemolition measurement—a "back-action-evading" measurement of the real part X_1 (or the imaginary part X_2) of the oscillator's complex amplitude. In principle X_1 can be measured "arbitrarily quickly and arbitrarily accurately," and a sequence of such measurements can lead to an arbitrarily accurate monitoring of the classical force. The authors describe explicit Gedanken experiments which demonstrate that X_1 can be measured arbitrarily quickly and arbitrarily accurately. In these experiments the measuring apparatus must be coupled to both the position (position transducer) and the momentum (momentum transducer) of the oscillator, and both couplings must be modulated sinusoidally. For a given measurement time the strength of the coupling determines the accuracy of the measurement; for arbitrarily strong coupling the measurement can be arbitrarily accurate. The "momentum transducer" is constructed by combining a "velocity transducer" with a "negative capacitor" or "negative spring." The modulated couplings are provided by an external, classical generator, which can be realized as a harmonic oscillator excited in an arbitrarily energetic, coherent state. One can avoid the use of two transducers by making "stroboscopic measurements" of X_1, in which one measures position (or momentum) at half-cycle intervals. Alternatively, one can make "continuous single-transducer" measurements of X_1 by modulating appropriately the output of a single transducer (position or momentum), and then filtering the output to pick out the information about X_1 and reject information about X_2. Continuous single-transducer measurements are useful in the case of weak coupling. In this case long measurement times are required to achieve good accuracy, and continuous single-transducer measurements are almost as good as perfectly coupled two-transducer measurements. Finally, the authors develop a theory of quantum nondemolition measurement for arbitrary systems. This paper (Paper I) concentrates on issues of principle; a sequel (Paper II) will consider issues of practice

Tiling Report 2001

Southern Iowa producers have faced several years of above-average rainfall during spring planting season. Little crop was grown in 1993 and 1995 due to above-average rainfall and flooded fields. Most yields were reduced again in 1996, 1998, 1999, and 2001 due to wet soils and late planting. Wet autumns also delay harvest. Many of the soils common in southern Iowa are described as poorly drained. Producers are hesitant to invest in pattern tiling because of local soil characteristics – high clay, silty loams. Few fields in southern Iowa are pattern tiled. Producers believe that tile lines are only functional for a limited time due to a hard pan forming over the lines and are hesitant to invest significant dollars in installation. In other areas of Iowa with well-drained soils, pattern tiling has been proven successful, however not in southern Iowa

Foliar fungicide application techniques on soybeans

Soybeans (Glycine max L.) are a major commodity crop grown on over 29 million hectare (72 million acres) in the United States. A large part of the cropland base in Iowa, 5 million hectare (11 to 13 million acres) annually, is devoted to soybean production. Although long term crop yield trends are upward, soybean yield increases have been more stagnant than corn, the common companion rotational crop, causing growers to question factors such as disease that might be slowing yield growth. In late 2004 Asian Soybean Rust (Phahopsora pachyrhizi) was detected in the United States. Because of the potential for yield loss as observed in other countries, grower concern has resulted in increased interest in this and other foliar leaf spot diseases that may be affecting yield. Midwestern U.S. agronomic row-crop growers are generally familiar and experienced with herbicide and insecticide application, but have very limited experiences in field application of fungicides. Growers customarily have existing sprayer equipment set up to apply systemic herbicides with relatively large droplets to reduce drift and carrier application rates of 94 to 14 3L/ha (10 to 15 gal/acre) to minimize water transported and maximize the range of application area covered by an individual tank

Effects of Nozzle Type and Carrier Application on the Control of Leaf Spot Diseases of Soybean

Midwestern soybean growers seek information on effective application of foliar fungicides that do not translocate throughout the plant. Field application treatments included using a two-orifice nozzle tip producing fine droplets at 187 l/ha (20 gal/ac) and 112 l/ha (12 gal/ac) and a single-orifice nozzle tip producing a coarse droplet size more typical of herbicide applications at 168 l/ha (18 gal/ac). In addition an air-assisted sprayer was used at one of the two sites of the trials. Measurements included droplet size, droplet coverage, and foliar disease severity in the top, middle, and lower parts of the plant canopy, and soybean yield. Droplet size for application treatments generally followed expected manufacturer specifications. Percentage area covered and drops/cm 2 were not statistically different among application treatments except at top of the plant canopy at one site. Percentage area covered and drops/cm 2 were statistically greater at the top of the canopy (17 - 18% coverage) than at the middle or bottom (1 – 8% coverage) at both sites. Foliar disease pressure was light so that yield or disease severity was unaffected by application method or as compared to a check area without application

Effects of Bt Transformation on Diseases of Corn

The availability of genetically engineered com hybrids that are resistant to insect pests is an exciting development for com producers and the entire com industry. These hybrids are likely to become very popular as they continue to demonstrate dependable insect protection and yield performance. But these hybrids have other advantages as well. Because of the relationship between com insects, particularly the European com borer, and certain diseases, Bt hybrids have shown reduced levels of these diseases in side-by-side comparisons