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Title:   Author  item
                                            Jaradat, Abdullahitem
                                            Archer, Daviditem
                                            Johnson, Janeitem
                                            Van Kempen, Stephenitem
                                            Wagner, Stevenitem
                                            Eklund, James
  Submitted to: Meeting Abstract
                                    Publication Type: Abstract Only
                                    Publication Acceptance Date: 7/28/2004
                                    Publication  Date: 7/28/2004
                                    Citation: Jaradat, A.A., Archer, D.W., Johnson, J.M., VanKempen, S.J., Wagner, S.W., Eklund, J.J. 2004. Sampling strategies for crop yield assessment within and among crop rotations [abstract]. Seventh International Conference on Precision Agriculture Conference Abstracts. p. 223.Interpretive Summary:
                                Technical Abstract: Long-term 2- and 4-year crop rotations were designed to provide reliable information to formulate long-term strategies for crop sequencing that optimize crop and soil use options in the upper Midwest of the U.S. Multilevel sampling and monitoring at the single plant, plants per unit area and experimental plot levels were designed to quantify the spatio-temporal dynamics of alfalfa, corn, soybeans and wheat crops in 192 geo-referenced experimental plots, and their responses to alternative cropping systems, tillage and fertility treatments. Baseline soil information and crop yield were collected from all 192 plots during 2002 and 2003. Data on plant phenology, yield per plant and its components and yield per m**2 were collected in 2003 from one geo-referenced and one random sampling site within each of 16 plots per crop. The multivariate dataset was analyzed with the objective of identifying the hierarchy of constraints to plant growth, development and yield and to refine the sub-sampling strategy in future years. Variability in sub-sampled seed weight of corn, wheat and soybean explained 82.9, 54.8 and 30.7% of the variability in whole plot seed yield, respectively, indicating a highly diverse response of the three crops to different management practices. Variability in cropping system (conventional vs. organic), tillage (moldboard vs. strip tillage), nitrogen fertilizer and the previous crop in the crop rotation explained 47.8, 46.0 and 45.7% of the variability in seed yield of corn, soybeans and wheat in 2003, respectively whereas variation in electrical conductivity and in two factors derived from 42 soil physical and chemical variables explained 9.5, 19.4 and 16.2% of the variation in seed yield of corn, soybeans and wheat, respectively. Seed yield of corn and soybeans responded positively to conventional cropping system (46.7 and 26.9%, respectively) and positively and negatively to conventional tillage (49.4 and -10.2%, respectively) whereas corn, soybeans and wheat yields responded positively to nitrogen fertilizer (18.9, 3.1, and 30.1%, respectively). The information is being used to characterize the different cropping systems as to their productive capacity and to refine the sampling strategies as to their successively increasing scale and intensity.


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