Comparison of Three Alternative Oilseed Crops for the Central Great Plains

Abstract

Diversification of the traditional dryland cropping system in the central Great Plains (winter wheat [Triticum aestivum L.]-fallow) could lead to a more sustainable production system. Selection of suitable crops to rotate with winter wheat requires knowledge of productivity under a widely varying precipitation regime. The objectives of this study were to determine water use/yield relationships and likely average production levels for spring canola (Brassica napus L.), crambe (Crambe abyssinicia Hochst), and sunflower (Helianthus annuus L.), and to determine differences in oil concentration and soil water extraction patterns among these three crops. Canola, crambe, and sunflower were grown under a line-source, gradient irrigation (GI) system to determine seed yield and oil concentration under a range of water use. Sunflower was also grown in several dryland rotations following a variety of crops, which resulted in a range of starting soil water conditions. Soil water extraction was monitored with a neutron probe and time-domain reflectometry. All three crops exhibited linear responses of yield to water use. Sunflower was less responsive than canola and crambe, which had nearly identical water use/yield functions. Oil concentrations showed a trend for increasing oil content with increasing water use. Sunflower extracted water from lower soil depths than canola and crambe, which were similar in soil water extraction. Median yield levels predicted from long-term precipitation records at Akron, CO, were 1130, 1180, and 1520 Iblacre for canola, crambe, and sunflower, respectively. All three crops are agronomically feasible oilseed crops for dryland rotations with winter wheat in the central Great Plains.