Effects of No-tillage Fallow as Compared to Conventional Tillage in a Wheat-fallow System

The benefits of reducing tillage by use of herbicides for weed control emphasizes why research was started to study a fallow system where all tillage was replaced by herbicides. Wheat planting was then the only soil disturbing operation. Objectives of the research were to compare the effects of no-tillage (chemical), stubble-mulch and plow (bare fallow) systems of fallow on: 1. Grain yield. 2. Grain protein. 3. Residue retention. 4. Soil nitrate-nitrogen accumulation. 5. Soil water accumulations during fallow. Data presented are in the form of a progress report. These experiments will continue

EC58-123 Questions and Answers about Stubble Mulching

Extension Circular 58-123 provides questions and answers about Stubble Mulch farming

EC58-123 Questions and Answers about Stubble Mulching

Extension Circular 58-123 provides questions and answers about Stubble Mulch farming

Date of Planting Studies of Winter Wheat and Winter Barley in Relation to Root and Crown Rot Grain Yields and Quality

This study was undertaken to determine the nature of root and crown rot of wheat and to ascertain the proper time to plant winter wheat so as to conserve moisture, minimize root and crown rot and thereby maximize yield. Studies conducted for 15 years at several locations in western Nebraska reveal that planting date is a significant factor for higher yields, particularly in certain years

Weed Control for Reduced Tillage Systems

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Non-equilibrium dynamics and floral trait interactions shape extant angiosperm diversity.

Why are some traits and trait combinations exceptionally common across the tree of life, whereas others are vanishingly rare? The distribution of trait diversity across a clade at any time depends on the ancestral state of the clade, the rate at which new phenotypes evolve, the differences in speciation and extinction rates across lineages, and whether an equilibrium has been reached. Here we examine the role of transition rates, differential diversification (speciation minus extinction) and non-equilibrium dynamics on the evolutionary history of angiosperms, a clade well known for the abundance of some trait combinations and the rarity of others. Our analysis reveals that three character states (corolla present, bilateral symmetry, reduced stamen number) act synergistically as a key innovation, doubling diversification rates for lineages in which this combination occurs. However, this combination is currently less common than predicted at equilibrium because the individual characters evolve infrequently. Simulations suggest that angiosperms will remain far from the equilibrium frequencies of character states well into the future. Such non-equilibrium dynamics may be common when major innovations evolve rarely, allowing lineages with ancestral forms to persist, and even outnumber those with diversification-enhancing states, for tens of millions of years

Unit 1 -- soils and soil testing

1 online resource (PDF, 4 pages)This archival publication may not reflect current scientific knowledge or recommendations. Current information available from the University of Minnesota Extension: https://www.extension.umn.edu

Unit 2-Soil Acidity and the Importance of Liming

This archival publication may not reflect current scientific knowledge or recommendations. Current information available from the University of Minnesota Extension: https://www.extension.umn.edu

The role of asymmetric interactions on the effect of habitat destruction in mutualistic networks

Plant-pollinator mutualistic networks are asymmetric in their interactions: specialist plants are pollinated by generalist animals, while generalist plants are pollinated by a broad involving specialists and generalists. It has been suggested that this asymmetric ---or disassortative--- assemblage could play an important role in determining the equal susceptibility of specialist and generalist plants under habitat destruction. At the core of the argument lies the observation that specialist plants, otherwise candidates to extinction, could cope with the disruption thanks to their interaction with generalist pollinators. We present a theoretical framework that supports this thesis. We analyze a dynamical model of a system of mutualistic plants and pollinators, subject to the destruction of their habitat. We analyze and compare two families of interaction topologies, ranging from highly assortative to highly disassortative ones, as well as real pollination networks. We found that several features observed in natural systems are predicted by the mathematical model. First, there is a tendency to increase the asymmetry of the network as a result of the extinctions. Second, an entropy measure of the differential susceptibility to extinction of specialist and generalist species show that they tend to balance when the network is disassortative. Finally, the disappearance of links in the network, as a result of extinctions, shows that specialist plants preserve more connections than the corresponding plants in an assortative system, enabling them to resist the disruption.Comment: 14 pages, 7 figure

Total Synthesis of Spirastrellolide F Methyl Ester—Part 2: Macrocyclization and Completion of the Synthesis

Marvel of the sea: A concise and highly convergent total synthesis of the methyl ester of the marine macrolide spirastrellolide F (see picture), which has exquisite antimitotic properties, is reported. In this approach, the northern and the southern hemispheres of this intricate target are stitched together in only two consecutive steps (Suzuki coupling, Yamaguchi lactonization) without any interim protecting-group manipulations