A.B. Onken a , K.F. Bronson a , J.D. Booker a , R.J. Lascano a , T. L. Provin b , and H.A. Torbert c
aTexas A&M University, Texas Agricultural Experiment Station, Lubbock, Texas
bTexas A&M University, Texas Agricultural Extension Service, College Station, Texas
cUSDA-ARS, Grassland Soil & Water Research Laboratory, Temple, Texas
Phosphorus is the second most limiting nutrient in cotton ( Gossypium hirsutum L.) production after nitrogen. Response to P fertilizer, however, is often hard to predict in the Southern High Plains, even with soil test-based applications. Landscape position has a strong influence on yields and perhaps on fertilizer response as well. The objective of this 5-year study (1994 to 1998) was to determine P fertilizer response in irrigated cotton in different landscape positions. We used an 825-m transect of end to end 15-m plots across a broad swale in an Amarillo fine sandy loam in Lamesa, TX that included three landscape positions, sideslope, bottomslope and drainageway. A randomized complete block design was used with 11 replicates and 5 P rates (0, 22.4, 33.6, 44.8, and 56 kg P ha -1 ). Analysis of variance showed a linear or quadratic response to P fertilizer in 3 of 5 years, and an effect of landscape position in 4 of 5 years. Four-year lint yield averages, excluding 1997, were 1355 kg ha -1 in the bottomslope position in the landscape, and 1210 and 1226 kg ha -1 on the sideslopes and in the narrow drainageway, respectively. Cross-correlation using the 55 plots as a transect revealed few effects of soil properties on lint yield, but negative correlation between yield and elevation. In 1997, the one year without a landscape effect on yield, more rain fell during the growing season than in the other 4 years. This suggests that yield potential is higher in lower landscape positions because of more favorable soil water relations. Cotton lint response to P fertilizer was evident only in the bottomslopes and in the drainageway, and was absent in the sideslopes, meaning that variable rate fertilizer applications could be linked to management zones based on landscape position.
Bronson, K.F., A.B. Onken, J.D. Booker, R.J. Lascano, T.L. Provin, and H.A. Torbert. 2001. Irrigated cotton yields as affected by phosphorus fertilizer and landscape position. Commun. Soil Sci. Plant Anal. 32 (11&12): 1959-1967.