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In‐Season Nitrogen Status Sensing in Irrigated Cotton
Author(s) -
Chua Teresita T.,
Bronson Kevin F.,
Booker J. D.,
Keeling J. Wayne,
Mosier Arvin R.,
Bordovsky James P.,
Lascano Robert J.,
Green Cary J.,
Segarra Eduardo
Publication year - 2003
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/sssaj2003.1428
Subject(s) - lint , irrigation , drip irrigation , hectare , agronomy , environmental science , soil test , nitrogen , malvaceae , growing season , mathematics , soil water , chemistry , biology , agriculture , soil science , ecology , organic chemistry
Nitrogen recommendations for Upland cotton ( Gossypium hirsutum L.) in the western USA are based on spring soil NO − 3 –N tests. In‐season monitoring of plant N status is another approach. Our primary objective was to test spectral reflectance and chlorophyll meter measurements as in‐season N decision aids for irrigated cotton, and to compare these with soil test‐based N management. The secondary objective was to determine the fate of 15 N as affected by N management and irrigation modes. Urea ammonium nitrate was applied with low energy precision (LEPA) center‐pivot, surface drip, and subsurface drip irrigation. Microplots received 3 atom% 15 N. Soil test N application was based on 0‐ to 60‐cm soil NO − 3 –N and 1400 kg lint ha −1 expected yield. Thirty‐four kilograms of N per hectare was applied when green vegetative index (GVI) or chlorophyll meter readings relative to well‐fertilized plots were <0.95. Lint yield responded to N at Lubbock in 2000 and 2001, but not at Ropesville. Nitrogen applied with in‐season monitoring in 2000 at both sites was 34 to 101 kg N ha −1 less than soil test N application of 134 kg ha −1 , with similar yields. In Lubbock, 2001 lint yields were near the expected yield, and in three of four cases, N applications with in‐season monitoring equaled soil test N applications of 101 kg ha −1 Nitrogen‐15 recovery in plants ranged from 19 to 38%, and was affected by N management in two of three site‐years, but not by irrigation. This study indicates that basing N applications on in‐season monitoring can reduce N applications in low yielding seasons and match the yield potential in high‐yielding seasons.