FARMERS' DECISION PROCESSES AND ADOPTION OF CONSERVATION TILLAGE

In a transect survey of crop residue levels in 1995 and 1996, two Minnesota counties had very different percentages of cropland with desired residue cover even though the soil types were similar. To gain a better understanding of the reasons behind this difference, the farmers in these two counties were surveyed about their use or lack of use of conservation tillage practices. A statistical logit analysis of survey responses showed farmers are more apt to adopt conservation tillage if they are larger; are more concerned about erosion on their land; have made a recent major investment in the farm; use other producers for tillage information; have the management skill for conservation tillage; and believe conservation tillage will fit with their production goals and the physical setting of their farm. Two counterintuitive findings are the negative effects of the ease of finding information and the degree of control of the adoption decision. The costs and labor requirements of conservation tillage were important but not as statistically significant as those factors just listed. Some variables, that are often listed as potentially important factors, were not found to be important in this survey. These included the long-term viability of the farm; the age, education, and experience of the farmer; the debt level of the farm; whether a family member wanted to continue farming; the proportion of land rented; the use of other sources for tillage information; the complexity of conservation tillage practices; the producer's planning horizon; the risk of negative returns; the availability of support for conservation tillage systems; and the quality of conservation tillage information.Crop Production/Industries,

ENVIRO-ECONOMIC ANALYSIS OF PHOSPHORUS NONPOINT POLLUTION

The state of Minnesota seeks to reduce phosphorus loading to the Minnesota River by 40% from current levels. The state agency charged with achieving this reduction has indicated each watershed should reduce its current phosphorus loading by 40%. We hypothesized that policies targeting specific practices or regions would have a smaller negative impact on farm income than policies requiring every nonpoint polluter to reduce its contribution by 40%. Using a stylized version of one major watershed in the river basin as an example, we analyzed the cost-effectiveness of various nonpoint pollution reduction policies. We simulated current and alternative farming systems (designed to reduce phosphorus loading by changing tillage or fertilizer practices) in distinct regions within the watershed using a biophysical process model. For each system, estimates of phosphorus loading from biophysical simulation were combined with production cost and return estimates to create an enviro-economic model of the watershed. Additionally, risk premiums were estimated and included with cost estimates for each alternative system. We used a positive math-programming (PMP) version of the enviro-economic model to analyze nonpoint pollution reduction policies (pollution standard, phosphorus effluent tax, conventional tillage tax, and phosphorus fertilizer tax). When regions and practices within the watershed could be targeted for achieving the pollution reduction standard, 13,500 fewer hectares (6% reduction from the baseline cropland level) were farmed. When the same standard was uniformly applied to all regions (not targeted), cropland decline by 40,500 hectares (20%). Under either scenario, cropland was removed from production, implying some producers may exit farming. Cropland reductions resulted in farmers losing $2.8 million (5$11.4 million (21%). This finding illustrates how difficulty it is to reduce nonpoint pollution if one does not focus on specific regions. An effluent tax of $74 per kilogram of phosphorus reaching the river was needed to reduce phosphorus loading by 40$14 million (25% reduction from the baseline income level), $11 million of which were revenues from the effluent tax. Neither the conventional tillage tax nor the phosphorus fertilizer tax achieved a 40% reduction in phosphorus loading. This finding illustrates the difficulty of reducing nonpoint pollution by focusing only on one practice. Under a pollution-reduction standard, our results indicated it is more cost effective to reduce nonpoint pollution by targeting particular regions or practices in a watershed compared to not targeting. Specifically, producers farming on cropland susceptible to erosion in close proximity to water who switch from conventional tillage to conservation tillage and reduce phosphorus fertilization levels to those recommended by the state extension service will appreciably reduce phosphorus nonpoint pollution loading potential. Efforts to target those producers could minimize potential losses in farm income in the watersheds and the river basin.Environmental Economics and Policy,

TILLAGE SYSTEMS FOR MINNESOTA FARMS: ALTERNATIVE TECHNOLOGIES, ECONOMIC CONSIDERATIONS, AND DATA NEEDS

Crop Production/Industries,

Identification of novel chondroitin proteoglycans in Caenorhabditis elegans: embryonic cell division depends on CPG-1 and CPG-2.

Vertebrates produce multiple chondroitin sulfate proteoglycans that play important roles in development and tissue mechanics. In the nematode Caenorhabditis elegans, the chondroitin chains lack sulfate but nevertheless play essential roles in embryonic development and vulval morphogenesis. However, assignment of these functions to specific proteoglycans has been limited by the lack of identified core proteins. We used a combination of biochemical purification, Western blotting, and mass spectrometry to identify nine C. elegans chondroitin proteoglycan core proteins, none of which have homologues in vertebrates or other invertebrates such as Drosophila melanogaster or Hydra vulgaris. CPG-1/CEJ-1 and CPG-2 are expressed during embryonic development and bind chitin, suggesting a structural role in the egg. RNA interference (RNAi) depletion of individual CPGs had no effect on embryonic viability, but simultaneous depletion of CPG-1/CEJ-1 and CPG-2 resulted in multinucleated single-cell embryos. This embryonic lethality phenocopies RNAi depletion of the SQV-5 chondroitin synthase, suggesting that chondroitin chains on these two proteoglycans are required for cytokinesis

The evidence for automated grading in diabetic retinopathy screening

Peer reviewedPostprin

Calculating fertilizer value of supplemental feed for cattle on pasture (2006)

Most cattle maintained on pasture receive supplemental feed during some portion of the year. Supplements are commonly fed to grazing cattle when pasture forage quality and quantity are below animal requirements

Recoiling from a kick in the head-on collision of spinning black holes

Recoil ``kicks'' induced by gravitational radiation are expected in the inspiral and merger of black holes. Recently the numerical relativity community has begun to measure the significant kicks found when both unequal masses and spins are considered. Because understanding the cause and magnitude of each component of this kick may be complicated in inspiral simulations, we consider these effects in the context of a simple test problem. We study recoils from collisions of binaries with initially head-on trajectories, starting with the simplest case of equal masses with no spin and then adding spin and varying the mass ratio, both separately and jointly. We find spin-induced recoils to be significant relative to unequal-mass recoils even in head-on configurations. Additionally, it appears that the scaling of transverse kicks with spins is consistent with post-Newtonian theory, even though the kick is generated in the nonlinear merger interaction, where post-Newtonian theory should not apply. This suggests that a simple heuristic description might be effective in the estimation of spin-kicks.Comment: 12 pages, 10 figures. Replaced with published version, including more discussion of convergence and properties of final hol

Towards Closing the Window on Strongly Interacting Dark Matter: Far-Reaching Constraints from Earth's Heat Flow

We point out a new and largely model-independent constraint on the dark matter scattering cross section with nucleons, applying when this quantity is larger than for typical weakly interacting dark matter candidates. When the dark matter capture rate in Earth is efficient, the rate of energy deposition by dark matter self-annihilation products would grossly exceed the measured heat flow of Earth. This improves the spin-independent cross section constraints by many orders of magnitude, and closes the window between astrophysical constraints (at very large cross sections) and underground detector constraints (at small cross sections). In the applicable mass range, from about 1 to about 10^{10} GeV, the scattering cross section of dark matter with nucleons is then bounded from above by the latter constraints, and hence must be truly weak, as usually assumed.Comment: 12 pages, 2 figures; minor updates to match published versio