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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Semigroup forum 91 (1999), S. 393-400 
    ISSN: 1432-2137
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: log ) to determine the optimal interpolation method for mapping soil properties. Relationships between statistical properties of the data and performance of the methods were analyzed using soil test P and K data from 30 agricultural fields. For InvD weighting, we used powers of 1,2,3, and 4. The numbers of the closest neighboring points ranged from 5 to 30 for the three methods. The results suggest that KOlog can improve estimation precision compared with KO for lognormally distributed data. The criteria helpful in deciding whether KOlog is applicable for the given data set were the Kolmogorov-Smirnov goodness-of-fit statistic, coefficient of variation, skewness, kurtosis, and the size of the data set. Careful choice of the exponent value for InvD weighting and of the number of the closest neighbors for both InvD weighting and kriging (KO or KOlog) significantly improved the estimation accuracy (P ≤0.05). However, no a priori decision could be made about the optimal exponent and the number of the closest neighbors based on the statistical properties of the data. For the majority of the data sets, kriging with the optimal number of the neighboring points, a carefully selected variogram model, and appropriate log-transformation of the data performed better than InvD weighting. Correlation coefficients between experimental data and estimated results of kriging were higher than those of InvD for 57 out of a total of 60 data sets, kriging mean absolute errors were lower for 44 data sets, and kriging mean errors were lower than those of InvD weighting for 31 data sets.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2137
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Zea mays L.) was overplanted and thinned to 44000 to 104000 plants ha-1 . The objective of our field research was to estimate the economic value, to the farmer, or variable rate seeding (VRS) as compared with uniform rate seeding (URS). We first estimated the correlation between field quality and economically optimal plant density for the Midwest Corn Belt was 67900 plants ha-1. For every tonne per hectare increase in site quality, as measured by yield potential, the predicted value of the site-specific economically optimal plant density increased by approximately 1200 plants ha-1 . We compared differences in revenues minus seed costs on four simulated fields. The value of VRS, ignoring the costs of VRS equipment and services, ranged from $12.83 ha-1 for farmers with VRS technology and full information to $0.15 ha-1 for farmers with VRS technology but only partial information. Profitable implementation of VRS will require detailed and expensive information regarding site characteristics, production inputs, and stochastic factors. Therefore, VRS will remain economically infeasible for most commercial corn growers until the cost of obtaining such information decreases considerably.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Semigroup forum 92 (2000), S. 75-91 
    ISSN: 1432-2137
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Zea mays L.) and soybean [Glycine max (L.) Merr.] yield data collected from 1994 to 1997, a detailed terrain map, and relatively densely sampled soil organic matter (OM) content, cation exchange capacity (CEC), and P and K soil test concentrations from eight fields in central Illinois and eastern Indiana. Soils of the Illinois fields were classified as Haplaquolls and Argiudolls; soils of the Indiana fields were classified as Hapludalfs. Topographical land features used in the study included elevation, measured with survey grid global positioning system (GPS) and land-based laser, and slope, curvature, and flow accumulation, derived from elevation data. Soil properties explained about 30% of yield variability (from 5 to 71% for different fields), with OM content influencing yield the most. The cumulative effect of the topographical features explained about 20% of the yield variability (6–54%). Elevation had the most influence on yield, with higher yields consistently observed at lower landscape positions. Curvature, slope, and flow accumulation significantly affected yield only in certain conditions, such as extreme topographical locations (undrained depressions or eroded hilltops) combined with very high or low precipitation. Soil properties and topography explained about 40% of yield variability (10–78%).
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Agronomy journal 91 (1999), S. 928-933 
    ISSN: 0002-1962
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Glycine max (L.) Merrill] plants grown with no-tillage (NT) often appear smaller than those grown with conventional tillage (CT), yet they produce similar grain yield. Our objective was to test the hypothesis that the early-season growth depression is offset by compensatory growth and changes in plant development. A 2-yr field study was conducted at Urbana, IL, on a long-term tillage experiment. Grain yield, moisture, protein, and oil content were similar for CT and NT treatments. Total plant, stem, leaf, and pod dry biomass were all initially about 15 to 20% greater under CT, but the difference declined until about R5 or R6; thus, compensatory growth did occur. At the initiation of sampling (V2) crop growth rate was about 20% greater under CT, but the difference declined until about R2. The advantage shifted to NT until about R6. Leaf area index (LAI) was greater for CT until about R4. Net assimilation rate was greater for NT until about R5. Increases in early-season crop growth rate for CT was due to increased LAI. Greater crop growth rate for NT late in the season was due to increased net assimilation rate. Leaf weight ratio was larger for the CT crop until about R6. Specific leaf area was less in CT than NT. This work supports our hypothesis that compensatory growth and alterations in plant development occur when soybean is grown in NT systems and helps to explain why grain yield does not decrease with NT even though early-season growth is affected.
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  • 5
    ISSN: 1573-1618
    Keywords: precision agriculture ; value of information ; economic complementarity ; economic optimality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An ultimate purpose of much agronomic and agricultural economic research is to provide management guidelines (e.g., on application rates of fertilizer, seed, and herbicides) to farmers. Ideally, farm management guidelines or recommendations would be determined by applying sound economic theory to data from agronomic experiments. While information provided by agronomic data about the relationship between crop yields, managed inputs, soil characteristics, and weather variables has always been valuable, we argue in this paper that because such information and precision agriculture technology are economic complements, the advent of precision agriculture technology has made information provided by agronomic experiments now even more valuable than ever. The purpose of this paper is to point out and respond to two practical implications of the complementarity between precision technology and information from agronomic research. The first implication is that because precision technology has made information more valuable, it is also more costly now when agronomists make mistakes in using economic theory to derive incorrect farm management recommendations from the information. Therefore it is more important than ever that agronomists understand some basic economic theory about agricultural production and precision technology. Our response is to provide here an economic primer on precision agriculture and information. We also recommend increased collaboration between agronomists and agricultural economists in precision technology research. The second implication is that, because precision technology has made the information more valuable, there is more need than ever for long-term, multi-regional agronomic experiments. For before scholarly experts can provide separate management recommendations for many very small areas of farmers' fields, they will need to know much more than they currently do about the relationships between crop yields, input application rates, soil characteristics, and weather variables. Our response is to call for agronomists to begin designing and implementing such experiments, and to call for increased public funding of such experiments.
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  • 6
    Publication Date: 2004-05-01
    Print ISSN: 0002-1962
    Electronic ISSN: 1435-0645
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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  • 7
    Publication Date: 1998-11-01
    Print ISSN: 0002-1962
    Electronic ISSN: 1435-0645
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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  • 8
    Publication Date: 2004-01-01
    Print ISSN: 0011-183X
    Electronic ISSN: 1435-0653
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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  • 9
    Publication Date: 2005-11-01
    Print ISSN: 0002-1962
    Electronic ISSN: 1435-0645
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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  • 10
    Publication Date: 1994-01-01
    Print ISSN: 0002-1962
    Electronic ISSN: 1435-0645
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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