Harvest Efficiency


In use from 2014-08-01


Starting in 2014, we will estimate harvest efficiency and losses to senescence in the perennial plots and continuous corn (G1, G5-7 and G9-10). Just prior to plot harvest, we will clip all vegetation in 3 quadrats per plot and measure the weight to get harvest aboveground net primary production (HANPP).



Quadrats (1m2, as a 2.0 × 0.5 m rectangle, and 1.0 m2, as a 1.52 m x 0.66 m rectangle)
Paper bags
Weighing balance
Drying oven
Labels and pens

Sample near each of the station flags in each plot, according to the table below. These locations will avoid the quadrats clipped for ANPP earlier in the year. Orient the quadrat in an east-west direction. Clip all biomass at ground level and place in labeled paper bag (note treatment, rep, and station). Also collect surface litter from the quadrat and place in a separate bag. Place both bags in the drying oven at 60°C for at least 48h or until it reaches constant mass. Record weight of dried biomass.

Table 1. Quadrat sizes and sampling locations.

Treatment Quadrat dimensions Location of quadrat relative to station flag
G1 – cont. corn 1.52 m x 0.66 m 1.5 m S, 1.5 m W
G5 – switchgrass 2.0 m x 0.5 m 2m S, 2m W
G6 – Miscanthus 1.52m x 0.66 m 1.5m S, 1.5m W
G7 – grass mix 2.0 m x 0.5 m 2m S, 2m W
G9 – old field 2.0 m x 0.5 m 2m S, 2m W
G10 – prairie 2.0 m x 0.5 m 2m S, 2m W


All units are g/m2, and the results from the stations should be averaged, to get one number for ANPP, HANPP, and surface litter for each plot.

Loss to senescence = ANPPHANPP
Loss to litter = surface litter @harvest – surface litter @peak
Loss to translocation = loss to senescence – loss to litter
= ANPPHAB + (surface litter @ harvest – surface litter @ peak)
Mechanical loss = Harvest Yield – HANPP
Harvest efficiency = Harvest Yield/HANPP

Date modified: Wednesday, Jan 20 2021



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