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- Title
Canopy Reflectance-Based Nitrogen Management Strategies for Subsurface Drip Irrigated Cotton in the Texas High Plains.
- Authors
Bronson, Kevin F.; Malapati, Adi; Scharf, Peter C.; Nichols, Robert L.
- Abstract
Nitrogen fertilizer management in subsurface drip irrigation (SDI) systems for cotton (Gossypium hirsutum L.) can be very efficient when N is injected with the irrigation water (fertigated) on a daily basis. However, the daily rates and total amounts of N fertigation are uncertain. Normalized difference vegetative index (NDVI), calculated from weekly canopy reflectance measurements can guide N management in SDI cotton. The objective of this 3-yr study (2007-2009) on an Acuff sandy clay loam (fine-loamy, mixed, superactive, thermic Aridic Paleustolls) near Lubbock, TX, was to test two canopy reflectance-based strategies for estimating and adjusting injection rates of urea ammonium nitrate (UAN) fertilizer between first square and early mid-bloom. We also evaluated three N rates; 50, 100, and 150% of the soil test-based N recommendation for a 1400 kg lint ha-1 yield goal. In the reflectance-based N strategy-i (RN1), UAN was injected starting at first square at 50% of the soil test N rate. When NDVI in RN1 fell significantly below NDVI of plots with 100% soil test N, the N injection rate was increased to match the injection rate of the 100% soil test plots. The reflectance-based N strategy-2 (RN2) had an initial N injection rate equal to that of the 100% soil test N, and was raised to match the 150% soil test N based on NDVI. Nitrogen rates for the RNI averaged across 3 yr were 22 kg N ha-1 less, or 31% less than the soil test treatment, without hurting lint or seed yields. In 2007, N rates with RN2 were 11 kg N ha-1 higher than the soil test N rate, without any yield benefit. Economic optimum N rates for lint production ranged from 23kg N ha-1 in 2009 to 75kg N ha-1 in 2008.
- Subjects
TEXAS; NITROGEN fertilizers; FERTILIZERS; PLANT regulators; AGRICULTURAL chemicals; PLANT growth; MICROIRRIGATION; COTTON
- Publication
Agronomy Journal, 2011, Vol 103, Issue 2, p422
- ISSN
0002-1962
- Publication type
Article
- DOI
10.2134/agronj2010.0161