Cotton lint yield variability in a heterogeneous soil at a landscape scale

Landscape variability associated with topographic features affects the spat ial 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 fi eld on the southern High Plains of Texas in 1999 to assess soil water, soil NO3-N, cotton (Gossypium hirsutum L.) Lint yield, and N uptake variability in the landscape, and to determine the spatial correlation between these l andscape variables using a state-space approach. The treatments were irriga tion 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 field. Soil NO3-N in early spring was autocorrelat ed at a distance varying between 60 and 80 m. Measured soil volumetric wate r content (WC), total N uptake, and lint yield were generally higher on low er landscape positions. Cotton lint yield was significantly correlated to s oil WC (r = 0.76), soil NO3- N (r = 0.35), and site elevation (r = -0.54). Differences of site elevation between local neighboring points explained th e soil water, NO3-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. Th e state-space analysis showed that cotton lint yield was positively weighte d on soil WC availability and negatively weighted on site elevation. Cotton lint yield state-space models give insights on the association of soil phy sical and chemical properties, lint yield, and landscape processes, and hav e the potential to improve water and N management at the landscape-scale. ( C) 2001 Elsevier Science B.V. All rights reserved.