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Title: Soil carbon and nitrogen stocks of different Hawaiian sugarcane cultivars

Author
item TIRADO-CORBALA, REBECCA - University Of Puerto Rico
item Anderson, Raymond - Ray
item Wang, Dong
item Ayars, James

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2015
Publication Date: 6/19/2015
Publication URL: http://handle.nal.usda.gov/10113/61001
Citation: Tirado-Corbala, R., Anderson, R.G., Wang, D., Ayars, J.E. 2015. Soil carbon and nitrogen stocks of different Hawaiian sugarcane cultivars. Agronomy. 5(2):239-261. doi: 10.3390/agronomy5020239.

Interpretive Summary: Hawaiian sugarcane is being examined for conversion to biofuels via 2nd generation processes. Along with sugarcane stalk, sugar, and leaf production, biofuel cultivation practices have the potential to counteract carbon dioxide emissions from fossil fuels by storing carbon in the soil. This carbon and nitrogen storage also improves soil health and fertility. Hawaiian sugarcane has a unique production system that is considerably longer than other regions of the world, and the soil carbon storage potential has not been evaluated in this environment. We assessed four local sugarcane varieties on two different soil types. The results show a consistent increase with soil carbon storage across all varieties and soil types, but two of the four varieties had higher carbon storage. These varieties had more extensive root systems that can grow deeper in different soil types. The research benefits potential large consumers of Hawaiian biofuels, commercial growers looking to re-establish sugarcane and other high-production energy grasses on abandoned lands elsewhere in Hawaii, and future researchers looking to investigate alternative crops and agronomic practices to optimize the greenhouse gas reduction potential of biofuels and to improve soil health and fertility.

Technical Abstract: Sugarcane has been widely used as a biofuel crop due to its high biological productivity, ease of conversion to ethanol, and its relatively high potential for greenhouse gas reduction and lower environmental impacts relative to other derived biofuels from traditional agronomic crops. In this investigation, we studied four sugarcane cultivars (H-65-7052, H-78-3567, H-86-3792 and H-87-4319) grown on a Hawaiian commercial sugarcane plantation to determine their ability to store and accumulate soil carbon (C) and nitrogen (N) across a 24-month growth cycle on contrasting soil types. The main study objective establish baseline parameters for biofuel production life cycle analyses; sub-objectives included (1) determining which of four main sugarcane cultivars sequestered the most soil C and (2) assessing how soil C sequestration varies among two common Hawaiian soil series (Pulehu-sandy clay loam and Molokai-clay). Soil samples were collected at 20 cm increments to depths of up to 120 cm using hand augers at the three main growth stages (tillering, grand growth, and maturity) from two experimental plots at to observe total carbon (TC), total nitrogen (TN), dissolved organic carbon (DOC) and nitrates (NO-3) using laboratory flash combustion for TC and TN and solution filtering and analysis for DOC and NO-3. Aboveground plant biomass was collected and subsampled to determine lignin and C and N content. This study determined that there was an increase of TC with the advancement of growing stages in the studied four sugarcane cultivars at both soil types (increase in TC of 15–35 kg·m2). Nitrogen accumulation was more variable, and NO-3 (<5 ppm) were insignificant. The C and N accumulation varies in the whole profile based on the ability of the sugarcane cultivar’s roots to explore and grow in the different soil types. For the purpose of storing C in the soil, cultivar H-65-7052 (TC accumulation of ~30 kg·m-2) and H-86-3792 (25 kg·m-2) rather H-78-3567 (15 kg·m-2) and H-87-4319 (20 kg·m-2) appeared to produce more accumulated carbon in both soil types.