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Brassicaceae oilseed crops have proven potential as vegetable oil feedstock for biofuels and food uses. However, meeting a growing demand for vegetable oils for food and industrial uses will require identifying oilseed species that are best suited for various growing environments within a particular region. The objective of this study was to compare growth dynamics, seasonal water use (WU), seed yields, and water use efficiency (WUE) of canola (Brassica napus L.), camelina (Camelina sativa L.), and white mustard (Sinapis alba L.) to determine their suitability under three different environments within the northern Great Plains. Comparisons were made among these species over three growing seasons between 2013 and 2016 at Morris, MN; Mandan, ND; and Sidney, MT, situated along a strong precipitation gradient from east to west. Generally, growing season precipitation was similar at Morris and Mandan, but both were considerably greater than at Sidney. Seasonal WU was similar among these oilseed species at Morris and Mandan but was greatest for camelina at the drier Sidney environment. Canola seed yield was the greatest at Morris and had higher WUE than camelina and white mustard. At Mandan and Sidney, canola and camelina had similar seed yields and WUE, which were generally greater than white mustard. Under abundant moisture and low stress (e.g., Morris), seed yield per millimeter of water used could be maximized by growing canola, while in a drier more stressful environment like Sidney, seed yield per millimeter of water used could be maximized by growing camelina. Core Ideas: Water use, growth, and seed productivity were evaluated for three Brassicaceae oilseeds.Camelina and mustard were earlier to mature than canola.There was little difference in seasonal water use for the three species at each location.Camelina and canola had similar water use efficiency at two out of three locations. [ABSTRACT FROM AUTHOR]

Perennial forages have the potential to diversify annual crop rotations and provide yield benefits to subsequent cash crops. Little is known about the duration of and extent to which yield benefits are observed in semiarid no-till systems following perennial forages, which may depend on the perennial crop type and duration of the perennial phase. Five perennial forage and forage combinations, alfalfa (Medicago sativa L.; PALF), intermediate wheatgrass [Thinopyrum intermedium (Host) Barkw. & D.R. Dewey subsp. Intermedium; IMWG], switchgrass (Panicum virgatum L.; SWG), alfalfa--intermediate wheatgrass mixture (PALF+IMWG), alfalfa--switchgrass mixture (PALF+SWG), and an annual cropping system of continuous spring wheat (Triticum aestivum L.) fertilized with 67 kg ha-1 of N (CWF) were evaluated for their impacts on wheat yields in a 7-yr study conducted near Mandan, ND. Wheat yields following 2 yr of alfalfa were comparable to CWF, and 3 and 4 yr of alfalfa, respectively, were 19 and 41% higher. After 5 yr of PALF+SWG, which was primarily comprised of alfalfa, wheat yields were 23% higher than CWF, and comparable to CWF after 3 and 4 yr in PALF+SWG. Four years in PALF+IMWG were needed to produce wheat yields comparable to CWF. Yield benefits persisted for up to 3 and 4 yr following 3 yr of PALF or 5 yr of PALF+IMWG, respectively. Overall, alfalfa and alfalfa--perennial grass mixtures showed the greatest promise for enhancing yields. These results indicate that a perennial phase of at least 2 yr is needed to provide yield benefits to subsequent no-till annual crops. [ABSTRACT FROM AUTHOR]

To further understand the impact of tillage on carbon dioxide (CO2) emission, we compare the performance of two conceptual models that describe CO2 emission after tillage as a function of the non-tilled emission plus a correction resulting from the tillage disturbance. The models assume that C in the readily decomposable organic matter follows a first-order reaction kinetics equation as and that soil C-CO2 emission is proportional to the C decay rate in soil, where Csoil( t) is the available labile soil C (g m−2) at any time ( t) and k is the decay constant (time−1). Two possible relationships are derived between non-tilled ( FNT) and tilled ( FT) soil fluxes: (model 1) and (model 2), where t is time after tillage. The difference between these two models comes from an assumption related to the k factor of labile C in the tilled plot and its similarity to the k factor of labile C in the non-till plot. Statistical fit of experimental data to conceptual models showed good agreement between predicted and observed CO2 fluxes based on the index of agreement (d-index) and with model efficiency as large as 0.97. Comparisons reveal that model 2, where all C pools are assigned the same k factor, produces a better statistical fit than model 1. The advantage of this modelling approach is that temporal variability of tillage-induced emissions can be described by a simple analytical function that includes the non-tilled emission plus an exponential term, which is dependent upon tillage and environmental conditions. [ABSTRACT FROM AUTHOR]