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  • Wiley  (5)
  • Phillips, S. B.  (5)
  • 1
    In: Agronomy Journal, Wiley, Vol. 97, No. 6 ( 2005-11), p. 1603-1611
    Abstract: Corn ( Zea mays L.) grain yields are known to vary from plant to plant, but the extent of this variability across a range of environments has not been evaluated. This study was initiated to evaluate by‐plant corn grain yield variability over a range of production environments and to establish the relationships among mean grain yield, standard deviation, coefficient of variation, and yield range. A total of forty‐six 8‐ to 30‐m corn transects were harvested by plant in Argentina, Mexico, Iowa, Nebraska, Ohio, Virginia, and Oklahoma from 2002 to 2004. By‐plant corn grain yields were determined, and the average individual plant yields were calculated. Over all sites in all countries and states, plant‐to‐plant variation in corn grain yield averaged 2765 kg ha −1 (44.1 bu ac −1 ). At the sites with the highest average corn grain yield (11478 and 14383 kg ha −1 , Parana Argentina, and Phillips, NE), average plant‐to‐plant variation in yield was 4211 kg ha −1 (67 bu ac −1 ) and 2926 kg ha −1 (47 bu ac −1 ), respectively. As average grain yields increased, so did the standard deviation of the yields obtained within each row. Furthermore, the yield range (maximum corn grain yield minus the minimum corn grain yield per row) was found to increase with increasing yield level. Regardless of yield level, plant‐to‐plant variability in corn grain yield can be expected and averaged more than 2765 kg ha −1 over sites and years. Averaging yield over distances 〉 0.5 m removed the extreme by‐plant variability, and thus, the scale for treating other factors affecting yield should be less than 0.5 m. Methods that homogenize corn plant stands and emergence may decrease plant‐to‐plant variation and could lead to increased grain yields.
    Type of Medium: Online Resource
    ISSN: 0002-1962 , 1435-0645
    Language: English
    Publisher: Wiley
    Publication Date: 2005
    detail.hit.zdb_id: 1471598-3
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  • 2
    Online Resource
    Online Resource
    Wiley ; 1998
    In:  Soil Science Society of America Journal Vol. 62, No. 3 ( 1998-05), p. 683-690
    In: Soil Science Society of America Journal, Wiley, Vol. 62, No. 3 ( 1998-05), p. 683-690
    Abstract: The scale or resolution where distinct differences in soil test and yield parameters can be detected has not been thoroughly evaluated in crop production systems. This study was conducted to determine if large differences in soil test and forage yield parameters were present within small areas ( 〈 1 m 2 ). A 2.13 by 21.33 m area was selected for intensive forage and soil sampling from two bermudagrass [ Cynodon dactylon (L.) Pers.] pasture sites (Burneyville and Efaw, OK). Each 2.13 by 21.33 m area was partitioned into 490, 0.30 by 0.30 m (1 by 1 ft) subplots. Bermudagrass forage was hand harvested at ground level from each 0.30 by 0.30 m subplot. Prior to forage harvest, spectral radiance readings (red, 671 ± 6 nm; green, 550 ± 6 nm; and near infrared, 780 ± 6 nm) were recorded from each subplot. Composite samples composed of eight soil cores, 0 to 15 cm deep and 1.9 cm in diameter, were collected from each subplot. At both locations, bermudagrass forage yield harvested from 0.30 by 0.30 m subplots ranged from 〈 1300 to 〉 10 000 kg ha −1 . Soil pH ranged from 4.37 to 6.29 within the 2.12 by 21.33 m area at Burneyville and 5.37 to 6.34 at Efaw. No P or K fertilizer would have been recommended at Efaw using mean soil test P and K. The range in recommended fertilizer rates would have been 0 to 31 and 0 to 17 kg P ha −1 and 0 to 107 and 0 to 108 kg K ha −1 at Burneyville and Efaw, respectively, if recommendations were based on individual 0.30 by 0.30 m grid data. Significant differences in surface soil test analyses were found when samples were 〈 1 m apart for both mobile and immobile nutrients.
    Type of Medium: Online Resource
    ISSN: 0361-5995 , 1435-0661
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 1998
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
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  • 3
    Online Resource
    Online Resource
    Wiley ; 1999
    In:  Soil Science Society of America Journal Vol. 63, No. 5 ( 1999-09), p. 1237-1243
    In: Soil Science Society of America Journal, Wiley, Vol. 63, No. 5 ( 1999-09), p. 1237-1243
    Abstract: Although alfalfa ( Medicago sativa L.) usually obtains a high percentage of its required N via symbiotic N fixation, additional fertilizer N applied once in the spring can increase forage yields. However, little is known about alfalfa yield response to low N rates ( 〈 50 kg N ha −1 ) immediately following each cutting. Low N rates (immediately following each cutting) were evaluated for total alfalfa dry matter production on a Grant silt loam (fine‐silty, mixed, thermic, Udic Argiustoll). This nonirrigated experiment was initiated on a 2‐yr‐old alfalfa stand where sufficient P and K had been applied. Nitrogen rates of 11, 22, and 44 kg N ha −1 were applied immediately following each cutting for 5 yr (4–5 cuttings yr −1 ). After 5 yr of continuous N application, no differences in soil NH 4 –N or NO 3 –N were found at depths 〉 15 cm (0‐ to 240‐cm sampling depth). In 1994, total alfalfa dry matter yield (sum of five harvests) increased 1.29 Mg ha −1 from a total annual N application of 110 kg N ha −1 (22 kg N ha −1 following each cutting). Total forage N decreased from the second to the fifth harvest in most years. By‐harvest dry matter yield increases due to applied N were only found in late‐season harvests, consistent with late‐season decreased N 2 ‐fixing capacity in alfalfa documented by others.
    Type of Medium: Online Resource
    ISSN: 0361-5995 , 1435-0661
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 1999
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
    Location Call Number Limitation Availability
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  • 4
    Online Resource
    Online Resource
    Wiley ; 1997
    In:  Journal of Environmental Quality Vol. 26, No. 6 ( 1997-11), p. 1632-1637
    In: Journal of Environmental Quality, Wiley, Vol. 26, No. 6 ( 1997-11), p. 1632-1637
    Abstract: To ensure that NO 3 ‐N concentrations in groundwater do not exceed the maximum contaminant level (MCL; 10 mg L −1 ), drinking water supplies are continuously sampled and analyzed. Water sampling and analytical methods have changed during the past 40 yr, and failure to apply the errors associated with those methods places researchers at risk of reporting invalid NO 3 ‐N changes. The objectives of this research were to compare analytical procedures, seasonal samplings, and storage methods for well water NO − 3 N analyses using historical and recent well water data, to identify where changes in NO 3 ‐N concentration have taken place and possible reasons for the changes; and to determine if age of water, well depth, and NO 3 ‐N concentration are related. Benchmark NO 3 ‐N analyses were obtained for 46 water wells which were then sampled each season (fail, winter, spring, and summer) over a 2‐yr period. For each sampling, four samples were taken from each well; two were frozen immediately (common today) and two were stored at ambient temperature (benchmark procedure). Nitrate‐N was determined on subsamples from all four samples using phenoldisulfonic acid (benchmark procedure) and automated Cd reduction (common today). This work suggests that a minimum difference of 6.15 mg NO 3 ‐N L −1 is required before declaring significant differences between historical and current well water NO 3 ‐N levels.
    Type of Medium: Online Resource
    ISSN: 0047-2425 , 1537-2537
    Language: English
    Publisher: Wiley
    Publication Date: 1997
    detail.hit.zdb_id: 120525-0
    detail.hit.zdb_id: 2050469-X
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  • 5
    Online Resource
    Online Resource
    Wiley ; 1999
    In:  Journal of Production Agriculture Vol. 12, No. 2 ( 1999-04), p. 254-257
    In: Journal of Production Agriculture, Wiley, Vol. 12, No. 2 ( 1999-04), p. 254-257
    Type of Medium: Online Resource
    ISSN: 0890-8524
    Language: English
    Publisher: Wiley
    Publication Date: 1999
    detail.hit.zdb_id: 2806272-3
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