The procedure, which can be used for both broadcast and row-planted plots, can be used to make fairly accurate estimates of grain yield during a single visit by researchers to the field. This procedure is especially useful for production systems in which harvests are typically carried out in stages. This procedure is remarkably accurate in the Botswana production situation because much more of the variability in sorghum and millet grain yields is due to head numbers per hectare than to average weight per head. The procedure is as follows:
Sub-Sampling. Sub-sample the plot with a 2m by 2m quadrat. Take 20 quadrat sub samples in a systematic pattern. Usually, this pattern consists of two passes through the plot with 10 equally spaced sub-samples. If the plot is row planted, each pass follows rows near, but not on, the border. In such a case, select rows that are one-fourth of the plot width from the border on both sides of the plot. Preferably, three people work: two carry the quadrat, and one carries the sample bags and records data. The front carrier follows a sampling line and the rear carrier counts paces. The quadrat is placed on the ground, without bias, at the toe of the rear carrier. For row planting, record the number of rows in each sub-sample and average row spacing in each plot.
Data and Sample Collection. In each sub-sample, counts are made on the number of plants and number of grain heads. Heads are recorded as:
HR -- Heads already harvested before measurement.
MT -- Heads ready for harvest.
GR -- Heads that are green. These can reach maturity.
GZ -- Heads that are completely missing due to livestock feeding.
At this point, there are two options:
Option 1: Harvest the MT heads and put them in large, brown kraft paper bags. Labelling includes field, plot, and quadrat number. Close and staple bags. Pack sample bags from plot in a large burlap bag.
Option 2: Harvest the MT heads and bulk all sub-samples from the plot in a large burlap bag. This is the option now recommended.
Drying, Threshing, and Weighing Samples. Which approach to use here is based on the options used above:
Option 1: Oven dry or sun dry the sub-samples. For sun drying, the heads should be removed from the bag. For this option, a protected space is required, reached by the sun, in which to spread and dry the samples. Alternatively, heads may be left in the bags to dry, but the bags must be opened fully. When the samples are left in the bags, drying will take a little longer, but it reduces the danger of samples getting mixed up or lost, When samples reach a uniform threshing moisture, the heads are counted and threshed, grain weighed, and the data recorded on the harvest data sheet, A labelled bag is used to hold a sample throughout the final weighing process.
Option 2: If the grain is wet, it is first dried, and then bulked sub-samples are threshed and weighed at the farm,
Additional points to note are:
