Robert L. Zimdahl

Entry and Movement in Vegetation of Lead Derived From Air and Soil Sources

The body of information presented in this paper is directed to individuals concerned with the state of our knowledge on lead uptake and translocation by plants and its subsequent effects. Lead, a non-essential element, is taken up by many plant species primarily via their roots. Large amounts of lead are deposited on plant foliage and most remains as a topical deposit but foliar uptake has been demonstrated. To date it has been assumed that soil lead levels above 1000 ppm are required to cause observable plant effects. Environmental variables, plant age, and species are very important determinants of lead uptake. The few studies done with plant age and speciation, however, provide no clear generalization. Increasing soil lead availability increases plant uptake. Plant uptake decreases with increasing soil phosphorus, organic content, and pH. The lack of observable lead intoxication of native and agricultural plants is surprising in light of evidence that lead concentrations as low as 1 ppm have a profound...

Lead in soils and plants: A literature review*

The distribution of lead in the environment is altered by the activities of man, principally through its use as a fuel additive. Lead appears in automobile exhaust as halides, hydroxides, and oxides, with lesser amounts of carbonates and sulfates. Lead concentrations decrease rapidly with depth in the soil and distance downwind from a source, and show a positive correlation with traffic volume. Lead in soil is moved slowly by leaching, due to sorption and formation of insoluble compounds. Sorption of lead by soils is positively correlated with cation exchange capacity. Lead can be taken up by plant roots if in an available form, but soil sorption phenomena and precipitation prevent uptake of large amounts unless soil lead levels are extremely high. Lead can be absorbed by plant foliage but much of it is apparently in the form of a surface deposit. Lead content of plants grown in natural soils is generally less than 10 ppm d.w. When taken up by a plant, lead may be found principally in the roots, with little translocation to the shoot. Lead uptake is enhanced by low soil pH and can be reduced by liming the soil.

The President said

Abstract This paper is a review of and a commentary on the published addresses of WSSA presidents from the founding of the Society through 2000. The papers assumptions are that the presidential remarks will reveal what the Society has emphasized, what its major concerns and goals have been, and how the presidents have addressed what they considered to be important issues. Seven issues have been addressed by many presidents. These include the importance of agricultural production and profit, the necessity of herbicides, weed science and the environment, the regulation of herbicides, the need for education, comparison of weed science and other plant protection disciplines, and the problem of herbicide resistance. Nomenclature: Presidents; Society; WSSA.

Teaching Agricultural Ethics

A survey was conducted in the United Statesin 1998 and 1999 to determine what members of theNational Association of State Universities and LandGrant Colleges (NASULGC) and of the AmericanAssociation of State Colleges and Universities (AASCU)offered agricultural ethics as an undergraduatecourse. Of the 59 responses, the survey found 15 USuniversities that have a course on agricultural ethicsor one that includes the topic. This paper willdiscuss the surveys findings and offer six reasonsthat explain why so few universities includeagricultural ethics in their curriculum. The sixreasons are: 1) lack of education in ethics andphilosophy on the part of agricultural scientists; 2)lack of institutional or disciplinary incentives foragricultural scientists to reflect on their work andits effects; 3) lack of administrative leadership incolleges of agriculture due to their failure tounderstand the benefits of agricultural ethics; 4)continuance of the prevailing assumption thatagriculture is inherently ethically correct; 5) thefelt necessity by agricultural scientists to defendthemselves against what are perceived to be unjust andinaccurate criticisms of agriculture; and 6) areluctance to engage in ethical reflection because itmay raise more problems than it solves. The paperscentral question is why ethics is not taught in morecolleges of agriculture. Those who teach know thattheir students are tomorrows farmers, businesspeople, professors, and policy makers. If we who nowteach and administer fail to include true ethicalstudy in our students education, our students willstill be defensive when confronted with an ethicalissue and unable to respond except with assertionsbased on the production paradigm, the correctness ofwhich, although unexamined, we taught them. If theagricultural faculty does not recognize theopportunity and the obligation to participate in theshaping of values, then the values of agriculture willbe shaped elsewhere in the institution and insociety.

Rethinking agricultural research roles

An examination of the role ofUniversity weed scientists in herbicide efficacyresearch and long-term weed management studies raisesseveral important questions: who should do what kindof research and what kind of research should be done,and, because the university is a research institutionfunded by the public, there is also the importantquestion of who should pay for the research. Indeveloping a response to these questions, severaldimensions of the relationships within which weedscience works must be considered. The author‘sexperience has demonstrated that production, thedominant value in agriculture, provides a sufficientanswer to the questions for many in weed science.However, when weed scientists claim credit forexcellence in production they must also acceptsociety‘s right to hold them responsible for problemsthey now treat as externalities.

The mission of land grant colleges of agriculture

Abstract. This paper examines what land grant colleges of agriculture were designed to be and do and, using theirpublished mission statements, discusses what they now claim to be and do. Teaching ‘such branches of learning as arerelated to the agriculture and the mechanic arts’ and ‘to promote the liberal and practical education of the industrialclasses’ is what land grant colleges were designed to do; it is the land grant mission. The paper asks whether thesethings are what land grant colleges of agriculture do now. The original mission has been amended with new challengesthat must be met in a time of declining public support for higher education, societal distrust of science and a negativepublic perception of agricultural technology, in a culture that wants cheap food. The agricultural community, includingcolleges of agriculture, has been slow to accept the challenges and opportunities inherent in the questions agriculturenow faces. Agriculture remains an essential human activity in our post-industrial, information-age society. Colleges ofagriculture are in trouble, and this paper suggests that the sensible thing to do may be to turn away from self-interestin survival to take a leadership role with emphasis on the obligations of service and humanism.

An Apparatus for the Exposure of Plants to Selected Particulate Aerosols

A simple, inexpensive apparatus is described for the generation of particulate aerosols of known identity with aerodynamic size distributions characteristic of urban atmospheres. Means for using this system for the exposure of plants to selected lead aerosols are described. The design offers improvements over other systems used for similar purposes.

Lime: A Soil Amendment

Lime did not change agricultural practices as other chemicals did. It made agricultural production possible on acidic soils where it had been impossible or, if possible, production was always low. Lime assured the ability of the worlds farmers, who must till acidic soils, to fulfill their primary moral obligation: to feed people.

Weed Science - A Plea for Thought - Revisited

The original essay was written in 1991 and published by the US Department of Agriculture in 1993. After twenty years it is appropriate to ask if weed science has overcome the paralysis of the pesticide paradigm and if the discipline’s research emphases have changed. Weed scientists are confident of increasing production through intelligent use of agricultural technology, including herbicides. But, we must ask if the moral obligation to feed people is sufficient justification for the benefits and harms achieved. A continuing, rigorous examination of the science’s goals that leads to appropriate changes is advocated. People agree that all goals and the means to achieve them should be good. Inevitable value questions arise because people do not agree on what is good, true or on what ought to be done. There is little public consensus about the necessity and value of widespread pesticide use to increase food production and improve public health. Weed scientists have a research consensus, and thus a paradigm, which should be explored. The paradigm has two propositions: 1. there are weeds that must be controlled and 2. herbicides are the primary, most efficient control technology. Since 1800 the indisputable evidence shows that agriculture has contributed significantly to the fact that the majority of the earth’s population is better fed, better sheltered, protected from disease, richer and lives longer. This perception of success affects how agriculture is practiced in developed and developing nations. The conventional wisdom is that herbicides are necessary tools of modern technology avocated by nearly all parts of the agricultural enterprise. Agriculture’s practitoners should engage in regular discussion of the necessity and risks of all pesticides for continued agricultural progress. These will not and should not focus only on the scientific evidence. They will include and must address value-laden arguments. Separating issue of fact from issues of value is fundamental to debate about weed science’s future.

The Pesticide Paradigm

The use of natural and synthetic chemicals as pesticides is an ancient agricultural practice. In 1000 B.C., Homer wrote of the pest averting sulphur. In 470 B.C., Democritus suggested that residues from the production of olive oil could be used to cure blight. The harmful effects of salt were mentioned by Xenophon in 400 B.C. and the Romans sowed their enemies’ fields with salt as continuing punishment (Smith and Secoy 1976). Mercurous chloride was first used as a fungicide for seed treatment in 1755 and Bordeaux mixture (copper sulphate, lime and water) was discovered in France in 1865. It was used to control downy mildew on grapevines. Selective control of weeds began around 1900 in France, Germany and the US using sulphates and nitrates of heavy metals. The first synthetic organic chemicals were introduced in 1932 (2-methyl-4,6-dinitrophenol for weed control) and in 1934 the first patent on dithiocarbamates as fungicides was granted.