Harvest Efficiency

Materials:

• Quadrats (see Table 1)
• Paper bags
• Weighing balance
• Drying oven
• Labels and pens
• Clippers

Procedure

Samples were collected near each of the station flags in each plot, avoiding the area sampled for ANPP earlier in the year. Quadrats were selected according to the table below and oriented in an east-west direction. All biomass was clipped at ground level and placed in paper bag labeled with treatment, rep, and station. Samples were not sorted to species. Surface litter from inside the quadrat was also collected and placed in a separate bag. All samples were oven-dried at 60°C for at least 48h or until constant mass, weighed and recorded. Corn plants were then run through a thresher, the grain collected and weighed.

Table 1. Quadrat dimensions used.

Calculations

For each plot:
1. Determine the average standing biomass and the surface litter at harvest for all stations.
2. Determine the average standing biomass and surface litter at peak biomass using the data collected for Aboveground Net Primary Production (ANPP).
3. Use machine-harvested yield values in dry matter yield datatables for corn (grain) and perennials.

The following can be estimated:
Loss to senescence = biomass @ peak – biomass @ harvest
Loss to litter = surface litter @harvest – surface litter @peak
Loss to translocation = loss to senescence – loss to litter
Mechanical loss = biomass @ harvest – harvested yield
Harvest efficiency = harvested yield/biomass @ harvest