Sampling frequency: minimum of once per year.

* GLBRC intensive sites are comprised of two annual crop treatments that include continuous corn (G1) and a rotation of corn-soybean-canola (G2-G4) with each crop represented in separate plot per year. 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: Corn stover from the main plot is flail chopped and baled with JD 7420a tractor and JD 385 round baler. Stover moisture is determined by taking 3 moisture readings per bale with a Farmex® DHT-1 Digital Hay Tester with 32" Probe.

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. 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.

Percent recovery is calculated by using formula;

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