ECONOMIC AND ENVIRONMENTAL BENEFITS OF VARIABLE RATE APPLICATION OF NITROGEN TO CORN FIELDS: ROLE OF VARIABILITY AND WEATHER

The use of meta-response functions based on EPIC-generated data resulted in comparisons between variable (VRAT) and uniform rate application technologies for 36 simulated fields. VRAT was more profitable and less nitrogen was lost to the environment in most cases. When spatial variability was small, uniform rate application techniques were adopted. However, when nitrogen use is restricted, VRAT is used on all simulated fields.Precision farming, site-specific farming, spatial variability, nitrogen restriction, rainfall, EPIC, crop growth simulation model, meta-response functions, Environmental Economics and Policy, Research and Development/Tech Change/Emerging Technologies, Resource /Energy Economics and Policy,

Widespread evidence for heterogeneous accretion of the terrestrial planets and planetisimals

The abundance and relative proportion of highly siderophile elements (HSEs) in Earth’s mantle deviate from those predicted by low-pressure equilibrium partitioning between metal and silicate during formation of the core. For many elements, high-pressure equilibration in a deep molten silicate layer (or ‘magma ocean’) may account for this discrepancy [1], but some highly siderophile element abundances demand the late addition, a ‘late veneer’, of extraterrestrial material (i.e. heterogeneous accretion) after core formation was complete [2]. Siderophile elements in smaller asteroidal bodies will not be affected by high-pressure metal-silicate equilibration and so, with highly efficient core formation [3] and if a ‘late veneer’ is absent, significant differences in the proportions of HSEs can be anticipated. Here we present new HSE abundance and 187Os/188Os isotope data for basaltic meteorites, the HEDs (howardites, eucrites and diogenites thought to sample the asteroid 4 Vesta), anomalous eucrites (considered to be from distinct Vesta-like parent bodies) angrites and aubrites (from unidentified parent bodies) and SNCs (thought to be from Mars). Our data, taken with those for lunar rocks [4], demonstrate that these igneous meteorites all formed from mantle sources that possessed chondritic (i.e. primitive solar system) elemental and isotope compositions, indicating that late accretion is not unique to Earth, but is a common feature of differentiated planets and asteroidal bodies. Variations in the total HSE abundance suggest that the proportion of ‘late veneer’ added is a simple consequence of the size of each body (cross-section and/or gravitational-attraction), and may account for the volatile element budget, and the oxidationstate of Earth, Mars, the Moon and Vesta

ASSESSING SPATIAL BREAK-EVEN VARIABILITY IN FIELDS WITH TWO OR MORE MANAGEMENT ZONES

Farmers are interested in knowing whether applying inputs at variable rates across a field is economically viable. The answer depends on the crop, the input, their prices, the cost of variable rate technology (VRT) versus uninform rate technology (URT), and the spatial and yield response variability within each field. Methods were investigated for determining the range of spatial variability over which the return to VRT covers its additional cost compared with URT in fields with multiple management zones. Models developed in this article, or variants thereof, could be used to help farmers make the VRT adoption decision.management zones, nitrogen, precision farming, site-specific management, spatial break-even variability proportions, spatial variability, variable rate technology, yield response variability, Farm Management,

EVALUATING THE RETURNS TO VARIABLE RATE NITROGEN APPLICATION

Potential benefits of variable rate nitrogen application are illustrated and information needs identified. Lower costs of precision farming services, higher crop prices, and greater divergence in yield response potentials across management zones reduce the spatial variability required for profitable variable rate application. Information needs include identification and measurement of management zones within a field and estimation of management zone yield response functions, crop and input prices, and the cost of precision farming services.production economics, management zones, nitrogen, precision farming, spatial break-even variability proportions, variable rate applications, yield response variability, Crop Production/Industries,

Economic Feasibility of Kenaf Production in Three Tennessee Counties

Since the 1940s, kenaf has been viewed as a potential source of fiber, mainly for newsprint and high quality paper. Kenaf research has once again risen to the forefront due to the recent USDA tobacco buyout. Many states and farmers dependent upon tobacco revenues have been seeking alternative crops for a number of years. This study seeks to expand the current literature by examining the economic feasibility of growing kenaf within three counties in Tennessee. Nitrogen meta-yield response functions for kenaf and four traditional crops were developed for 30 soils through crop growth simulation modeling and used to compare optimal crop budgets for each soil. Results reveal that kenaf would not compete favorably with traditional crops on any soil at prices below $49/ton, while profit-maximizing farmers could supply as much as 1,385,700 tons of kenaf if the price were$55/ton.alternative crop, economic feasibility, enterprise budgeting, kenaf, plant growth modeling, yield response functions, Agribusiness, Crop Production/Industries,

The Variable-Rate Decision for Multiple Inputs with Multiple Management Zones

Research has evaluated the relative profitability of variable-rate versus uniform-rate application of a single input in fields with multiple management zones. This paper addresses the variable-rate decision for multiple inputs. The decision-making framework is evaluated for nitrogen and water applied to irrigated cotton in fields with three management zones.Crop Production/Industries,

Economic Feasibility of Kenaf Production in Three Tennessee Counties

This article seeks to expand current literature by discussing the economic feasibility of growing kenaf within three counties in Tennessee. Results revealed that kenaf would not compete with traditional crops at prices below $49/ton, while profit-maximizing farmers could supply as much as 1,385,700 tons of kenaf at prices of$55/ton.Crop Production/Industries,

The Variable-Rate Input Application Decision for Multiple Inputs with Interactions

Research has evaluated the relative profitability of variable-rate (VRT) versus uniform-rate (URT) application of a single input in fields with multiple management zones. This study addresses map-based VRT decisions for multiple inputs in fields with multiple management zones. The decision-making framework is illustrated for nitrogen and water applied to irrigated cotton in fields with three management zones. Results suggest traditional methods of determining VRT application of a single input may by suboptimal if interactions exist among VRT inputs and URT inputs. Implications are that a systems approach to multiple-input VRT decisions can produce increased net returns to VRT.breakeven analysis, cotton, economic feasibility, multiple-inputs, precision farming, variable-rate technology, Crop Production/Industries,

Adoption of Conservation-Tillage Methods and Genetically Modified Cotton

Adoption of herbicide-tolerant cotton and conservation tillage may be simultaneously related. Bayes' theorem and a two-equation logit model were used to test the simultaneity hypothesis. Evidence for Tennessee suggests that adoption of these technologies reduced residual herbicide use and soil erosion more than if adoption of these technologies were independent.Bayes' theorem, conservation tillage, cotton, genetically modified crops, herbicide tolerant crops, simultaneous logit model, technology adoption, Crop Production/Industries, Q12, Q16, Q24, O33,

Adoption of No-Tillage Practices, Other Conservation-Tillage Practices and Herbicide-Resistant Cotton Seed, and Their Synergistic Environmental Impacts

If adoption of herbicide-resistant seed and adoption of conservation-tillage practices are determined simultaneously, adoption of herbicide-resistant seed could indirectly reduce soil erosion and adoption of conservation-tillage practices could indirectly reduce residual herbicide use and increase farm profits. Our objective was to evaluate the relationship between these technologies for Tennessee cotton production. Evidence from simultaneous estimation of a trinomial logit model for adoption of no-tillage, other conservation-tillage, and conventional-tillage practices and a binomial logit model for adoption of herbicide-resistant and conventional cotton seed suggests a simultaneous relationship. The elasticity for acreage in herbicide-resistant seed with respect to the probability of adopting conservation-tillage practices was 3.98. The elasticities for acreages in no-tillage practices and other conservation-tillage practices with respect to the probability of adopting herbicide-resistant cotton seed were 0.34 and 0.10, respectively. Adoption of herbicide-resistant cotton seed in Tennessee reduced soil erosion by 9.2 million tons through its effects on adoption of conservation-tillage practices. By 2004, increases in adoption of conservation-tillage practices increased adoption of herbicide-resistant cotton seed by 445 thousand acres, substituting non-residual herbicides for residual herbicides on those cotton acres.Environmental Economics and Policy,