Division S-4- Soil Fertility and Plant Nutrition

Date

2003

Authors

Segarra, Eduardo
Green, Cary J.
Lascano, Robert J.
Bordovsky, James P.
Mosier, Arvin R.
Keeling, J.Wayne
Booker, J.D.
Bronson, Kevin F.
Chua, Teresita T.

Journal Title

Journal ISSN

Volume Title

Publisher

Soil Science Society of America

Abstract

Nitrogen recommendations for Upland cotton (Gosspium hirsutum L.) in the western USA are based on spring soil NO³--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 compute these with soil test-based N management. The secondary objective was to determine the fate of 15N as affected by N management irrigation modes. Urea ammonium nitrate was applied with low energy precision (LEPA) center-pivot, surface drip, and subsurface drip irrigation. Microplots received 3 atom% 15N. Soil test N application was based on 0- to 60-cm soil NO³-N and 1400 kg lint hn- 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 plot 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 hu- 1 less than soil test N application of 134 kg ha- I, with similar yields. In Lubbock. 2001 lint yields were near the expected yield, and in three of four cases, N applications with ill-season monitoring equaled soil test N applications of 101 kg hn-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.

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Citation

Chua, T., K. Bronson, J. Booker, J. Keeling, A. Mosier, J. Bordovsky, R. Lascano, C. Green, E. Segarra. "In-Season Nitrogen Status Sensing in Irrigated Cotton: I. Yields and Nitrogen-15 Recovery." _Soil Science Society American Journal_ 67 (2003): 1428-1438.