HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Hong, N. Articles by Sudduth, K. A. Search for Related Content PubMed PubMed Citation Articles by Hong, N. Articles by Sudduth, K. A. Agricola Articles by Hong, N. Articles by Sudduth, K. A. Related Collections Ground Water Quality Nitrogen

Economically Optimal Nitrogen Rate Reduces Soil Residual Nitrate

^a Div. of Plant Science, Univ. of Missouri, Columbia, MO 65211
^b USDA-NRCS, Columbia, MO 65203
^c USDA-ARS, Cropping Syst. and Water Quality Res. Unit, Columbia, MO 65211

View larger version (25K): [in this window] [in a new window]   Fig. 1. Locations of the six different producers' fields in Missouri where experiments were conducted.

View larger version (35K): [in this window] [in a new window]   Fig. 2. Daily precipitation in 2000 and 2001 for the three soil regions (CP = claypan, DL = deep loess, MD = Mississippi delta). The symbol represents the total precipitation during the study period for each region.

View larger version (12K): [in this window] [in a new window]   Fig. 3. Economically optimal N rate distributions for the sites where residual soil NO3–N was sampled in the six experimental fields. In the field abbreviations on the x axis, CP = claypan soil region, DL = deep loess soil region, MD = Mississippi delta soil region, 00 = 2000, and 01 = 2001.

View larger version (12K): [in this window] [in a new window]   Fig. 4. The frequency distributions of the EONR for the sampled treatments in six experimental fields. The EONR is the difference between the total N applied and economically optimal N rate (EONR).

View larger version (29K): [in this window] [in a new window]   Fig. 5. Plateau-linear response functions describing the response of the post-harvest residual soil NO3–N content within a 0.9-m depth to the EONR in the six experimental fields. The EONR is the difference between the total N applied and economically optimal N rate (EONR). Location abbreviations are CP = claypan soil region, DL = deep loess soil region, MD = Mississippi delta soil region, 00 = 2000, and 01 = 2001.

View larger version (17K): [in this window] [in a new window]   Fig. 6. Comparisons of the post-harvest residual soil NO3–N (RSN) content for different sample classes via the box-and-whiskers diagram. The upper and lower limits of each box signify the 25th and 75th percentiles for the RSN, the horizontal line in the center of the box indicates the median, the "+" sign in each box indicates the mean, and the "whiskers" or arms represent the full range of the RSN observed in each class. The EONR is the difference between the total N applied and economically optimal N rate (EONR). Different letters above the upper limits of each box indicate mean significance differences at the 0.05 probability level. The sample size of each class is given below the lower limits of each box. The class with EONR = 0 contains one value from each field, which was estimated from the plateau-linear function shown in Fig. 5. All other classes consist of observations classed from individual plot samples.