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Title: TEMPORALLY STABLE PATTERNS IN GRAIN YIELD AND SOIL WATER ON A DRYLAND CATENA

Author
item Andales, Allan
item Green, Timothy
item Ahuja, Lajpat
item Erskine, Robert - Rob
item PETERSON, GARY - COLORADO STATE UNIVERSITY

Submitted to: Agricultural Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2006
Publication Date: 4/13/2007
Citation: Andales, A.A., Green, T.R., Ahuja, L.R., Erskine, R.H., Peterson, G.A. 2007. Temporally stable patterns in grain yield and soil water on a dryland catena. Agricultural Systems 94 (2007) 119-127).

Interpretive Summary: Grain yields from dryland cropping systems can be affected by water availability, topographic position, and crop rotation. The temporal stability over multiple years of observed spatial patterns on a dryland catena is investigated. Questions remain about: 1) relationships between yield, soil water content, and topographic position; 2) whether the crop rotation system affects yield; and 3) possible interactions between landscape position and crop rotation. Data have been collected along a soil catena for winter wheat and corn grain yields and soil water content from 1986 to 1999 as part of a long-term study of sustainable dryland agroecosystem management in eastern Colorado, USA. The experiment included two-year (wheat [Triticum aestivum (L.)]-fallow), three-year (wheat-corn [Zea mays (L.)]-fallow), and four-year (wheat-corn-millet [Panicum miliaceum (L.)] or sunflower [Helianthus annus (L.)]-fallow) rotations arranged in a randomized block design (two replicates of each rotation/phase) with repeated measurements from three slope positions. Over all years, Analysis of Variance revealed a strong effect of topographic position on both corn and wheat yield (p < 0.0001), but no significant effect of crop rotation (p > 0.44) or rotation by position (p > 0.56). Yield at the toeslope was significantly different (p < 0.05) from yields at summit and sideslope positions. The patterns of yield and soil water along the catena were temporally stable over time, as shown by high correlations between slope positions. Linear regressions between slope positions explained 69 to 90% and 65 to 85% of the spatial-temporal variances in grain yields and profile soil water, respectively. Such spatial relationships can be useful for estimating spatial patterns from either temporal data collection or simulation results at limited spatial locations within a field.

Technical Abstract: Grain yields from dryland cropping systems can be affected by water availability, topographic position, and crop rotation. The temporal stability over multiple years of observed spatial patterns on a dryland catena is investigated. Questions remain about: 1) relationships between yield, soil water content, and topographic position; 2) whether the crop rotation system affects yield; and 3) possible interactions between landscape position and crop rotation. Data have been collected along a soil catena for winter wheat and corn grain yields and soil water content from 1986 to 1999 as part of a long-term study of sustainable dryland agroecosystem management in eastern Colorado, USA. The experiment included two-year (wheat [Triticum aestivum (L.)]-fallow), three-year (wheat-corn [Zea mays (L.)]-fallow), and four-year (wheat-corn-millet [Panicum miliaceum (L.)] or sunflower [Helianthus annus (L.)]-fallow) rotations arranged in a randomized block design (two replicates of each rotation/phase) with repeated measurements from three slope positions. Over all years, Analysis of Variance revealed a strong effect of topographic position on both corn and wheat yield (p < 0.0001), but no significant effect of crop rotation (p > 0.44) or rotation by position (p > 0.56). Yield at the toeslope was significantly different (p < 0.05) from yields at summit and sideslope positions. The patterns of yield and soil water along the catena were temporally stable over time, as shown by high correlations between slope positions. Linear regressions between slope positions explained 69 to 90% and 65 to 85% of the spatial-temporal variances in grain yields and profile soil water, respectively. Such spatial relationships can be useful for estimating spatial patterns from either temporal data collection or simulation results at limited spatial locations within a field.