More than 0.5 million ha of irrigated cotton ( Gossypium hirsutum L.) are grown
in the Southern High Plains of Texas. Conservation tillage cotton in terminated wheat
has been shown to improve water use-efficiency and reduce wind erosion. However, limited
N fertilizer response research has been done in this system. The objective of
this 3-yr field study at Lubbock, TX was to characterize the response to
N fertilizer (0, 28, 56, 84, or 112 kg N ha -1 ) at varying
irrigation levels (0, 25, 50, or 75 % ET replacement) for conventional and
conservation tillage cotton in an Acuff loam (Aridic Paleustoll). Additionally, we tested the
chlorophyll meter as an indicator of in-season N status of cotton and compared
it to petiole NO 3 - -N analysis. Cotton lint yields showed a quadratic response to
irrigation level in 1996 and 1997, and a linear response in the drought
year of 1998. Maximum lint yield varied from 71 to 97 % ET
replacement. In 1997 and 1998, cotton lint yields responded to N at the
50 and 75% estimated evapotranspiration (ET) replacement irrigation levels, but not at the
0 or 25% ET levels. Quadratic-plateau models indicated that 19 to 38 kg
N additional fertilizer ha -1 was needed to produce economically optimum lint yields near
1100 kg N ha -1 with conservation tillage than with conventional tillage. Chlorophyll meter
and petiole NO 3 - -N readings were positively related to N rate but were not
affected by tillage system.
Bronson, K.F., A,B, Onken, J.W. Keeling, J.D. Booker, and H.A. Torbert. 2001.
Nitrogen response in cotton as affected by tillage system and irrigation level. Soil
Sci. Soc. Am. J. 65: 1153-1163.