Cotton lint yield variability in a heterogeneous soil at a landscape scale Hong Li a , Robert J. Lascano b,* , Jill Booker b , L. Ted Wilson c , Kevin F. Bronson a a Texas A & M University, Rt. 3, Box 219, Lubbock, TX 79403, USA b Texas A & M University-USDA-ARS, 3810 4th Street, Lubbock, TX 79415, USA c Texas A & M University, 1509 Aggie Drive, Beaumont, TX 77713, USA Abstract Landscape variability associated with topographic features affects the spatial pattern of soil water and N redistribution, and thus N uptake and crop yield. A landscape-scale study was conducted in a center pivot irrigated ®eld on the southern High Plains of Texas in 1999 to assess soil water, soil NO 3 -N, cotton (Gossypium hirsutum L.) lint yield, and N uptake variability in the landscape, and to determine the spatial correlation between these landscape variables using a state-space approach. The treatments were irrigation at 50 and 75% cotton potential evapotranspiration (ET). Neutron access tubes were placed at a 15-m interval along a 710 m (50% ET) and 820 m (75% ET) transect across the ®eld. Soil NO 3 -N in early spring was autocorrelated at a distance varying between 60 and 80 m. Measured soil volumetric water content (WC), total N uptake, and lint yield were generally higher on lower landscape positions. Cotton lint yield was signi®cantly correlated to soil WC r  0:76, soil NO 3 - N r  0:35, and site elevation r 0:54. Differences of site elevation between local neighboring points explained the soil water, NO 3 -N and lint yield variability at the micro-scale level in the landscape. Soil WC, cotton lint yield, N uptake, and clay content were crosscorrelated with site elevation across a lag distance of 30±40 m. The state-space analysis showed that cotton lint yield was positively weighted on soil WC availability and negatively weighted on site elevation. Cotton lint yield state-space models give insights on the association of soil physical and chemical properties, lint yield, and landscape processes, and have the potential to improve water and N management at the landscape-scale. # 2001 Elsevier Science B.V. All rights reserved. Keywords: Landscape-scale; Soil heterogeneity; Water; NO 3 -N; Cotton lint yield; N uptake; Clay; Site elevation; State-space analysis 1. Introduction In the semiarid, southern High Plains of Texas, cotton production is primarily limited by the amount of water and N available to the plants, and wind erosion is the greatest hazard affecting soil water and nutrient use on the High and Rolling Plain soils. It is well established that landscape positions in¯uence soil water redistribution, N use, and crop yield (Ciha, 1984; Halvorson and Doll, 1991; Brubaker et al., 1993; Stevenson and Van Kessel, 1996; Kravchenko and Bollock, 2000). For example, slope position was strongly related to winter wheat yield in southeastern Washington (Ciha, 1984). Water is not evenly distrib- uted in landscapes with topographic in¯uences, which had a signi®cant effect on spring wheat grain yield and crop water use (Halvorson and Doll, 1991). Slope length affected crop yield (Simmons et al., 1989), N Soil & Tillage Research 58 (2001) 245±258 * Corresponding author. Tel.: 1-806-723-5238; fax: 1-806-723-5271. E-mail address: r-lascano@tamu.edu (R.J. Lascano). 0167-1987/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved. PII:S0167-1987(00)00172-0