GLBRC: Corn Stover Removal

Sampling frequency: minimum of once per year.

* GLBRC intensive sites are comprised of three annual crop treatments that include continuous corn (G1), continuous corn with winter cover crop (G2), and a rotation of corn-soybean (G3-G4) with a cover crop, with each crop represented in a separate plot per year. The cover crops are harvested each spring, prior to planting the main crop (corn or soy beans). In the treatments with cover crops (G2-G4), one-third of the stover non-removal microplot is also a cover crop non-removal plot, in which the cover crop is killed with a herbicide and the biomass left on the field. For more details, click experimental layout.

* To study the effect of stover removal on soil properties and yields, the experimental plots (KBS: 131 × 91 ft; Arlington: 140 × 90 ft) are split into a 60 ft wide main plot and a 15 ft microplot on the west side of the plot with the exception of corn rotations plots (G2R1, G3R1, G4R1) in block 1 of KBS site which are on the east side of plot.

* As a treatment the main plot gets 100% stover removal while microplots get 0% removal. Corn stover is removed shortly after the grain harvest in October or November.

A. KBS Protocol, 2009-2014: Corn stover from the main plot is flail chopped directly into a forage wagon and removed. Stover moisture is determined by weighing a representative grab sample (wet weight), then drying at 60°C and subtracting the dry weight from wet weight.
KBS Protocol, 2015-onward: Corn stover is windrowed and baled. The bales are weighed and stover moisture is determined as in previous years.

B. Arlington Protocol: Corn stover from the main plot is flail chopped directly into a forage wagon using a Case IH 684 Tractor and pull type flail chopper (10 – 13 cm cut height). Stover is weighed at field moisture in the chopper wagon using 4 – 4,500 kg x 2.25 kg wheel scales (one for each wheel of the wagon). A representative grab sample is then dried at 60°C until it ceases to lose weight to determine moisture content of harvest biomass and calculate dry matter harvested.

* Micro-Plot Grain Yields: To compare grain yield differences between treatments

A. KBS Protocol: The middle 5 ft wide area (2 corn rows without stover removed) is harvested out of the 15 ft wide microplot and is compared with a 5 ft wide control area (2 corn rows with stover removed) on the opposite side of the field. This is to avoid the edge effects and overcoming the harvest machinery differences. Equipment used for harvesting the main plot is different from microplot. This protocol is started from 2010 season and in years 2008 and 2009, yields from microplot area (2 corn rows) were compared to 60 ft wide main plot. There were no separate harvests from 5 ft area from the main plot in 2008 and 2009.

B. Arlington Protocol: The western 15 ft (6 corn rows without stover removed) is harvested and compared to the eastern 15 ft (6 corn rows with stover removed). This is done to compare harvest numbers from one plot edge (0% stover removal micro-plot) to another (100% stover removal border rows). The same equipment is used as the main plot which facilitates harvest on the same day as the main plot and provides a larger area to minimize variability in yield. In year 2008, the 5 ft wide area (2 corn rows without stover removed) was hand harvested while in 2009 a small plot combine was used to harvest the same areas. Like KBS, there were no separate harvests from 5 ft area from the main plot in 2008 and 2009.

* To determine the efficacy of the harvesting machinery, the amount of residue remaining on the ground after the machine harvest is determined by placing a PVC frame (quadrat) of size 0.5×0.5m. 2009-2014 KBS, 2009-present ARL: Three samples per plot are taken randomly. The samples are weighed and dried at 60C for a minimum of 48 hours and dry weights are recorded. Percent moisture is calculated to overcome the moisture differences between stover removal and residue sampling dates.
2015-present KBS: Wind-rowing the corn stover results in an unequal distribution of stover across the field. To get a representative sample, walk a transect from the southwest corner of the plot to the northeast corner of the plot. Take a sample from each of the wind-rowed and non-wind-rowed strips with a 0.5 × 0.5 m quadrat. Then measure the width of each of the wind-rowed strips. Multiply the width of the strips by the length of the plot and use this information to get a weighted average of the wind-rowed and non-wind-rowed areas.

* GLBRC Scale-up sites L1 and M1 will have all stover removed and baled, starting in 2015. The stover will be windrowed and baled in the same way as the BCSE.

To determine the efficacy of stover removal, collect residue from the scale-up fields, using 1 m2 quadrats (dimensions: 1.52m x 1.66 m). At each station flag, place the quadrat entirely within a windrowed area and collect the residue. Repeat in an area between the windrows. Keep the within-windrow and between-windrow samples separate. Record wet weight and dry weight. To scale to the field, measure the average width of the between- and within-windrow areas, then calculate the ratio (W:B). Calculate the average dry weight of the within-windrow stover (WS) and the between-windrow stover (BS). Calculate weight of remaining stover as:
(WS * W:B) + (BS *(1-W:B))

Percent recovery (for both scale-ups and BCSE) is calculated as:

Percent recovery = (Weight of machine harvested stover) / (Weight of machine harvested stover + Weight of stover remaining on soil)

References

National Research Council (NRC). 2009. Liquid Transportation Fuels from Coal and Biomass. National Academies Press, Washington, D.C