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Ability for In‐Season Correction of Nitrogen Deficiency in Corn Using Chlorophyll Meters
Author(s) -
Varvel Gary E.,
Schepers James S.,
Francis Dennis D.
Publication year - 1997
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1997.03615995006100040032x
Subject(s) - fertilizer , environmental science , growing season , agronomy , chlorophyll , crop , nitrogen , dry season , mathematics , chemistry , biology , horticulture , ecology , organic chemistry
Nitrate‐nitrogen contamination of groundwater continues to be a major concern throughout the USA. These concerns are greatest in areas where groundwater is close to the soil surface and in areas that have irrigated crops with large N fertilizer requirements. Specific objectives of this work were to use the chlorophyll meter to determine in‐season crop N status and to correct in‐season N deficiencies in irrigated corn ( Zea mays L.). Chlorophyll meter readings were used to calculate a sufficiency index [(as‐needed treatment/well‐fertilized treatment) × 100] and in‐season N fertilizer applications were made when index values were below 95%. Using this procedure, maximum yields were attained if early season N levels were adequate to maintain sufficiency indexes between 90 and 100% at the V8 growth stage. However, if the sufficiency index at V8 was below 90%, maximum yields were not achieved with in‐season N fertilizer applications because early season N was below that needed for optimum growth and yield potentials had already been reduced. Even in these causes, N applications did increase yields, but not to the maximum. These results did demonstrate that early N deficiencies could be corrected using chlorophyll meters and the sufficiency index approach when they were not severe. Although the objective was not tested in this study, less N fertilizer may be required when in‐season monitoring is used as the basis for N application. Use of the chlorophyll meter and sufficiency index should also result in greater N use efficiency and less N being available for leaching to the groundwater since these applications are made when N uptake by corn is greatest.