Soil Water Content, CO2 Flux, and Crop Yields in Wheat-Camelina Cropping System.

Camelina (Camelina sativa L. Crantz) has been identified as a potential fallow replacement crop in dryland wheat (Triticum aestivum) based cropping systems in the Great Plains. Cropping sequence affects quantity and quality of soil residue returned to the soil, the ability of soils to sequester carbon, and plant available water. A field experiment was conducted to investigate the impact of replacing fallow with camelina on crop yields, soil water content at wheat planting, soil carbon dioxide (CO₂) flux, and residue return. Crop rotations evaluated in this study were: wheat-fallow (W-F), wheat-sorghum-fallow (W-S-F), wheat-spring camelina (W-SC), and wheat-sorghum-spring camelina (W-S-SC). Crop residue by weight measured at winter wheat planting increased with cropping intensification. Ground cover in the 3-yr rotations (W-S-SC and W-S-F) were similar to W-SC but greater than W-F. Soil CO₂ flux in W-SC was significantly different from other rotation systems. Average flux CO₂ rate from W-SC rotation was 1.3 umol m^-2 s^-1, 3.1 umol m^-2 s^-1, and 1.0 umol m^-2 s^-1 in spring, summer, and fall, respectively. Soil water content measured at wheat planting in the top 0-60 cm was greatest in W-S-F (18.1 cm). However, soil water content in W-SC (15.0 cm) and, W-S-SC (15.1 cm) were not different from W-F (16.5 cm). Increasing cropping intensity decreases wheat yield, but it was not significantly different from W-F rotation. Camelina yield was affected by crop rotation, and may be attributed to low soil moisture.