Corn-Switchgrass Study for Greenhouse gas Reduction through Agricultural Carbon Enhancement network and Resilient Economic Agricultural Practices in Lincoln, Nebraska
Lincoln NE Corn-Switchgrass Experiment USDA-ARS REAP Study (Ithaca, NE) – NEMEIRR Sustainable intensification of high-yielding production systems may help meet increasing demands for food, fuel, and fiber worldwide. Specifically, corn stover is being removed by producers for livestock purposes, and stover is also targeted as a primary 2nd generation biofuel feedstock. The NEMEIRR experimental objectives are to quantify how stover removal (no removal, moderate removal, high removal) and tillage management (no-till, disk) affect crop yields, soil organic carbon, soil greenhouse gas emissions, and other soil responses (microbial community structure, function; soil health). This experiment is conducted in a fully irrigated continuous corn system in the western Corn Belt, and soil and plant measurements have been taken since study establishment in 2001. By: V.L. Jin (1 Sep 2016). marginal or idle cropland in the USA alone [In Approxi-mately 40% of USA maize (Zea map L) grain production is used for fuel ethanol production and the non-grain biomass or stover remaining after grain harvest has been proposed as a significant cellulosic feedstock for advance biofue Is production [18,191. No-till or minimum-till farming practices have increased in the USA because of their con-servation benefits and reduced production costs (201. Infor-mation on the effect of maize stover removal under no-till management on soil C from long-term Arles has not been available to date [211. Most of the research on SOC in agricultural production systems focused on C in the 0 to 30 cm depth 122-271. A few studies in which soil sampling has been conducted at greater depths indicate that !reduc-tion agriculture affects soil C deeper in the soil profile 128,291. We initiated a replicated, long-term, non-irrigated soil C sequestration study in 1998 in eastern Nebraska. USA. to evaluate the effects of N fertilizer and harvest management treatments on SOC for switchgrass managed far biomass production and for a no-till maze production system with and without stover removal. It is the longest on-going C sequestration study on these crops grown for bioenergy. Our hypotheses were that N knilization and harvest manage-ment practices affect soil C sequestration in both no-till maize and switchgrass biomass production systems and that these changes occur deeper than 30 cm in the soil profile. Herein, we report the changes in SOC that occurred during the period from 1998 to 3007. Materials and Methods Experiment Field. The field used in the study was similar to the marginally productive fields expected to be used for switchgrare biomass production anti is in the western part of the main maize production area of the USA. it is located on the University of Nebraska’s Agricultural Research and Development Center (ARDC), Ithaca. Nebraska, USA (latitude 41.151, longitude 96.401 which is 50 km west of Omaha, NE. The field has Yutan silty clay loam (fine-silty, mixed, supaactive, mesic Mollie I 11,h:daft) and Tomek silt loam (fine, smectit ic, mesic Pachic Argiudoll ) soils. The ranges in the surface three depths of the Yutan soil for water 01 and kw CEC were 6.2 to 6.8 and 26 to 32 emotes kg r,respectively. The corresponding range in the surface three depths of the Tomek soil were water p11 values of 6.1 to 7.0 and a CEC range of from 24.4 to 32.3 moles kg-I. It is one of the least productive fields of the ARDC and is typical of marginally productive cropland fields Out might be used for switchgrass production for bier energy. The field used in the study was previously in sorghum (Sorghwn bicolor (L) Moench) in 1996 and in soybeans (Gipine mar (L) Merr.) in 1997. Experimental Design The study is a randomized (r-3) complete block split-split plot experimental design. Large rots were used so that field scale equipment could be used. Main plot lengths are the width of the field (ISO m) and are 18 m wide. Main plot treatments were two cultivars of switchgrass, Trailblazer and Cave-in-Rock, and no-till maize. The maize hybrid used was a commercial glyphosate (Roundupt? tolerant hybrid adapted to the region. The experiment was established in 1998 with the planting of the switchgrass plots. In 1998, plots designated for the no-till maize treatments were planted to glyphosate tolerant soybeans and grown using no-till management. No-till maize production began in 1999. Main plots were subdivided into three subplots which were used for N fertility treatments. Subplots are 30 m long x18 m wide and are separated by 15 m wide alleys. Nitrogen (N) fertilizer rates were randomly assigned to the subplots within species main plots. No fertilizer was applied during the establishment year for the switchgrass. In 1999, N fenilizer treatments were NI -0, 1¦2 – 80, N3-180, and N4-240 kg N he’. From 2000 on. they were NI -0, N2-60, N3-120, and N4-180 kg N he’. Fertilizer rates were reduced for 2000 and thereafter because of the 1999 resuhs on maize and the summarization of previous fertility re-search on switchgrass [34 Rates on the switchgrass were NI, N2, and N3. Rates used on no-till maize were N2, N3, and N4. Ammonium nitrate fertilizer was broadcast with a bulk spreader throughout the duration of the study. The 0 N-rate for switchgrass was used as a low input treatment only for switchgrass. In 2001. the switchgrass and corn subplots were split lengthwise into 9 m wide sub-subplots for harvest treatments. Switchgrass Management Switchgrass plots were seeded directly into the soybean stubble from the previous year using a no-till drill with a planting rate of 6.7 kg he’ (pure live seed basis). A re-emergence application of 2 kg hat atrazine [Aaoex 4 Lit: 6-chloro-N-erhyl-Isr-(1-methylethyl)-1, 3. 5-triazine-2, 4- di amine’ was applied for weed control. There were no other management inputs the establishment year. The 60 and 120 kg N ha-I rates represent the low to high rates recom-mended switchtoass grown for bioenergy [301 with the 0 rate representative or a no-input system. A previous study [301 showed that switchgrass harvested after a killing frost had significantly less N in the biomass than switchgrass harvested at anthesis indicating N was being recycled to the roots of switchgrass late in the growing season. Begin-ning in 2001. harvest treatments were applied to the sib-subplots within switchgrass cultivar N-fertility subplots to determine if harvest date might affect SOC. One harvest treatment (H I) was a mid-August harvest and the other (le) was a harvest in October or November, following a killing frost. Plots were harvested only once a year. A 4.6)(0.9 m (4.2 m2) area was harvested in each subplot with a flail-type plot harvester in 1998 and the following April, all remaining biomass from the previous year was removed with a field harvester prior to spring green-up. In 1999 and thereafter, switchgrass yield harvests weir made with flail harvesters and associated weighing equipment by harvesting a 0.9 to 1.8 m wide swath (varied with harvester used) the full 30 m length of the plots. At time of harvest, subsamples were collected from each sub-subplot, weighed for moisture con-tent, dried at 50°C for 48 h. and reweighed to determine dry matter content Yields were adjusted to a dry weight basis. The C concentration of the switchgrass samples was deter-mined using near infrared spectrometer (NIRS) procedures and calibrations 1311. A field flail harvester was used to remove all remaining biomass from the plots immediately following the yield harvests using the same harvest height of 10 cm. Maize Management Maize seed was planted directly into soybean stubble of the previous year in 1999 with a no-till drill and the maize plots of the previous year thereafter. The maize was gown in 0.76 m wide rows. The N rates that were used represent the low-to-high rates for maize grown under rarofed conditions in the region. Nitrogen fertilizer was applied using the same equipment as for switchgass plots. Glyphosate herbicide was applied after the maize had emerged and was about 40 cm in height. No other management inputs were applied until grain harvest Aboveground samples (one row 4.4 m long) were collected soon after physiological maturity in each N rate subplot and later from each sub-subplot for total biomass yields. Ears were removed and stalks were then cut at ground level, chopped and weighed. A representative subsample was collected, dried and weighed for gravimetric moisttre determination to calculate stover dry matter pro-duction. Ears were dried and weighed, added to the calcu-lated stover weight to obtain total biomass yields on a dry weight basis. Maize grain yields were determined with a plot combine equipped with a weighing unit, subsamples were collected for moisture determination, and yields were adjusted to oven dry weight basis. Because of the emerging interest in using maize stover for biomass energy, in 2001 stover harvest treatments were applied to the sro-subplots. The harvest treatments were no residue harvested (11 1 ) and approximately 50 % of the stover remaining after grain harvest (112). Stover was harvested from the 112 treatments after grain harvest using the flail forage harvesters that were used to harvest switchgass plots. Harvested stover yields were determined by harvesting the stover from two non-border rows of each sub-subplot its entire 30 m length with a plot-flail harvester. The remaining rows were harvested with a field scale flail harvester set at the same 10 cm height as the plot harvester. All stover weights were con-vetted to a dry-weight basis (50°C oven for 48 h). Maize grain and stover samples were analyzed for total C by dry combustion 1321. Soil Sampling and Analysis Baseline soil samples were obtained in July 1998 and plots were thereafter re-sampled at approximately 3-year intervals in May 2001. April 2004, and in May 2007. The initial sampling location was in the center of each subplot. Subse-quent soil samples were offset a fixed distance from each subplot or sub-subplot center to prevent re-sampling of a previous sampling site from which soil had been removed. Sample collection was done using the procedures described by Follett et al. [331. In brief, the plant material was re-moved from the soil surface and then, using a flat-bladed shovel. undercutting and removing the soil from the 0-5. 5 -10, and 10-30 an depths. Samples were also collected from the 30-60. 60-90. 90-120. and 120-150 cm depths at the July 1998 and May 2007 sampling dates using a hydraulic probe. Soil bulk densities were determined using the USDA-NRCS National Soils Laboratory methods (34J. The stan-dardized procedure (Soil Survey Laboratory method 3B1) to measure bulk density requires collection of field occurring fabric (clods), coating them with Saran F-310 in the field (NRCS 2004; Soil Survey Laboratory method 311), transport to the laboratory, and desorption to 33 kPa (1/3 bar). After reaching equilibrium, the clod is weighed in air to measure mass and in water to measure its volume, and next dried at 110°C (230°F) with its mass and volume again determined. A correction is made fir mass and volume of rock fragments and the plastic coating with the BD value reported for < mm (0.079in) soil fabric. Once samples Were collected they were sieved through a 2 mm sieve and < mm plant material picked from the soil. air dried (room temperature), subsampled, mechanically ground to pass through a 0.2-mm sieve, and the robsamples were stored in sealed glass containers with screw type lids All soils were checked for carborstes and in the very few casts where carbonates existed they were removed prior to analyses for organic C using accepted procedures [35,36J. All analyses were on an oven dry weight (55°C). The methodology is such that both the isotopic C analyses and the analyses for the total SOC are date at the same time for the same sample.