| الملخص: |
Carinata (Brassica carinata A. Braun), a non-food oilseed crop and an alternative bio-jet fuel feedstock, has received attention for its potential as a low-input option for production in the semi-arid regions of the Northern Great Plains of USA. The crop has a lower N fertilizer requirement as compared to the other oilseeds, suggesting less negative impact on soils and GHGs emissions. Carinata is a new crop to South Dakota (SD), thus, the best management practices have yet to be developed. In addition, no sufficient research to address the impact of growing carinata on soils and GHG emissions has been reported. The objectives of the study were to: (i) evaluate the response of seed yield and agronomic traits for carinata to N and S fertilizer rates, and (ii) evaluate the impact of growing carinata with different rates of N and S fertilizers on select soil properties and GHG emissions. Field experiments were conducted in 2017 and 2018 to assess the response of carinata to four N rates (56, 84, 112 and 140 kg N ha-1) and three S rates (0, 22 and 45 kg S ha-1) and) at Brookings, SD under conventional tillage. Increasing N fertilizer rate significantly increased plant height, branching, lodging severity, number of pods plant-1 but significantly decreased seed oil concentration. Increasing S fertilizer rate significantly increased plant height, branching, agronomic traits, seed yield, and seed oil concentration. This study showed that the economically optimal N rate was 85 kg N ha-1 and the economically optimal S rate was 36 kg S ha-1. Application of N fertilizer had minimal impact on soil parameters; N fertilizer increased soil EC, soil organic carbon (SOC), stable carbon, labile N, soil K, and soil P. Sulfur fertilizer decreased soil EC, SOC, labile N, and soil inorganic N content but increased extractable S content. Results from GHG emissions showed that, in addition to soil temperature and moisture conditions, N fertilizer increased CO2 and N2O emissions, whereas, S fertilizer application did not affect emissions. Methane fluxes fluctuated due to the impact of soil temperature and moisture. Findings from this study suggested that carinata has low nutrient requirements compared to the traditional crops grown in SD, and optimum N and S requirements for this crop were developed. This study also suggested that, in general, carinata has minimal impacts on soils and GHG emissions, however, a long-term monitoring of soils and GHG fluxes under different rotations, soils and environmental conditions can be beneficial in understanding the impacts associated with carinata production. |
