Agricultural management has a significant impact on the amount of greenhouse gases emitted by cropped fields. Alternative practices such as winter cover cropping and avoiding overfertilization can decrease the total amount of greenhouse gases that are produced. Policymakers are considering a structure in which parties (such as factories) who exceed their greenhouse-gas emissions cap can pay incentives to encourage farmers to adopt practices that curb greenhouse gases. Based on data from field studies and an ecosystem computer model, we assessed impacts on yields and the total potential for reducing greenhouse-gas emissions of certain alternative practices in California.
Carbon sequestration in agricultural land has been studied over the past few years to determine its potential for ameliorating climate change. Agricultural soils can be efficiently exploited as carbon sinks with a variety of techniques, such as reduced tillage, cover cropping and organic systems with better manure management. However, to fully understand the potential of carbon sequestration in agriculture, the economic costs of switching from conventional to conservation management must be estimated. Since carbon sequestration depends heavily on management, crop and soil type, we conducted a field-level survey of its economic aspects in Yolo County for the 2005 growing season. The survey showed that organic and conservation management can be more profitable for field crops than conventional management in Yolo County. Finally, we demonstrated how to combine the survey data with an agronomic process model to predict the rate of adoption for conservation techniques in response to carbon payments.
Ethanol use in California is expected to rise to 1.62 billion gallons per year in 2012, more than 90% of which will be trucked or shipped into the state. Switchgrass, a nonnative grass common in other states, has been identified as a possible high-yielding biomass crop for the production of cellulosic ethanol. The productivity of the two main ecotypes of switchgrass, lowland and upland, was evaluated under irrigated conditions across four diverse California ecozones — from Tulelake in the cool north to warm Imperial Valley in the south. In the first full year of production, the lowland varieties yielded up to 17 tons per acre of biomass, roughly double the biomass yields of California rice or maize. The yield response to nitrogen fertilization was statistically insignificant in the first year of production, except for in the Central Valley plots that were harvested twice a year. The biomass yields in our study indicate that switchgrass is a promising biofuel crop for California.
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