The aboveground biomass and nitrogen components of green leaves, dead leaves, stems, panicles, green leaf area, and dead leaves are measured and recorded at 0, 14, and 28 DAT, and at panicle initiation, flowering, and grain-filling stages.

Procedure

•  Use the randomized sampling layout below to collect 6-hill sample per plot. Select areas with a homogeneous crop stand that are representative of the whole sampling plot. For a non homogeneous crop stand, consider using the randomized spare sampling area.

• Cut all plants at the surface. Make sure that no leaves or stems (including dead tillers) are lost.

• Pool the plant material from all 6 hills into one composite sample per sampling plot.

• Carefully rinse off any adhering soil material and place the sample in a sampling bag.  The bag should be prelabeled with year, crop season, treatment, and date of sampling as information.

• Separate the green leaves, dead leaves, stems, and panicles.

• Immediately measure the leaf area of green leaves. Should there be a delay in leaf area measurements, wrap the green leaves with a moist cloth and keep these samples in a refrigerator for temporary storage.

• Dry the green leaves, dead leaves, stems, and panicle samples at 70°C for 3–5 days until constant weight.  Start to weigh selected samples on the third day to check when constant weight is achieved and drying can be finished.

• Record the final oven-dry weight when no change in weight occurs within 24 hours. Weigh samples immediately after taking them out from the oven to obtain the oven-dry weight of aboveground biomass.

• Calculate total aboveground dry matter yield (kg/ha).

• Grind the green leaf samples and store them in paper bags or coin envelopes with proper labels for N analysis.