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United States Department of Agriculture

Agricultural Research Service

Research Project: Carbon Sequestration and Nitrogen Cycling for Greenhouse Gas Mitigation by Southeastern U.S. Annual and Perennial Energy Crops

Location: Agricultural Systems Research Unit

2012 Annual Report


1a.Objectives (from AD-416):
i) Develop low-input production methods for napiergrass, energycane, forage sorghum and sweet sorghum. ii) Measure soil quality to ascertain sustainability of the proposed production methods. iii) Measure carbon and N sequestration in the soil and plant, and emission of NO2 from different cropping systems. iv) Develop comprehensive life cycle assessment models to quantify the economic and environmental value of the production systems.


1b.Approach (from AD-416):
Field experiments will be carried out at Fort Valley and Tifton. Soil will be collected at the beginning of the study to 60 cm depth to determine baseline values for pH, bulk density, texture, organic C (SOC), total N (STN), particulate organic C and N (POC and PON), microbial biomass C and N (MBC and MBN), potential C and N mineralization (PCM and PNM), NH4-N, and NO3-N contents and aggregate stability and distribution. Soil pH will be determined by a pH meter dipped in 1:2 soil-water suspensions. Bulk density will be estimated from oven dry soil weight divided by total volume. Soil texture will be determined by hydrometer method (Sheldrick and Wang, 1993). Total C and N will be determined by igniting the sample in a high temperature induction furnace in a high temperature induction furnace (Nelson and Sommers, 1996) as described above. Particulate organic C and N will be determined by the method described by Cambardella and Elliott (1992). Ammonium and nitrate N will be determined by the method described by Kenney and Nelson (1982). Aggregate stability and distribution will be determined by wet sieving method (Kemper and Rosenau, 1986). Microbial biomass C and N will be determined by the method described by Franzluebbers et al. (1996). Field experiment 1: Napiergrass and energycane will be planted in a split plot design with three replications. The crops will constitute the main treatments and plots subdivided into three fertility treatments: a) perennial clover planted between rows, b) clover +75 kg N/ha, and c) clover+ 150 kg N/ha (N rate based on preliminary yield results). Plots will be made of four rows, 9 m long spaced 1.8 m apart. The crops will be established by stem cutting obtained in the month of September, the thin top portion discarded and rest cut into sections comprising of three nodes to avoid apical dominance problem. The cuttings will be placed end-to-end in trenches 15 cm deep and covered. Perennial clover will also be seeded by drill at the same time. The N fertilizer will be applied to designated plots in spring before onset of growth. Field experiment 2: The experimental design of this experiment will be split-split plot with three replications. The main plots will comprise of three winter cover crop treatments, viz., hairy vetch annual rye and hairy vetch + annual rye. The first split will be the cover crop biomass harvested for feedstock or incorporated into the soil for enrichment. The sub-sub plots will be N fertilization at 0 kg/ha and 90 kg/ha. Cover crops will be drilled in the fall and harvested or incorporated in late April. Photoperiod sensitive sweet sorghum line will be planted at the rate of 2.24 kg/ha in early May in plots of four 9 m long rows spaced 76 cm apart. N-fertilizer will be applied to designated plots at the rate of 90 Kg N/ha. The observational parameters for this experiment will be similar to experiment #1. Harvesting of sweet sorghum will be similar to energycane. Field experiment 3: This experiment will be similar to experiment 2 excepting forage sorghum instead of sweet sorghum will be the feedstock crop. Forage sorghum stalks will be field dried without squeezing.


3.Progress Report:

Baseline soil samples were collected from the 0- to 90-cm depth at 10 places from experimental sites before the experiments were initiated in Fort Valley and Tifton GA. These were composited by depth, air-dried, and ground to 2 mm. Samples were analyzed for soil total C and N (STC and STN), particulate organic C and N (POC and PON), microbial biomass C and N (MBC and MBN), potential C and N mineralization (PCM and PNM), NH4-N, and NO3-N concentrations. Results showed that all soil C and N fractions decreased with soil depth in both Fort Valley and Tifton, except NO3-N concentration which increased with depth (Tables 1 and 2). Soils in Fort Valley had greater C and N fractions than in Tifton.

More soil samples will be collected in the coming years and results will be reported as samples are analyzed.


Last Modified: 7/25/2014
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