Agriculture Reference
In-Depth Information
factors have little effect. Although NIRS technology is very accurate and relatively easy to use, the cost of
the equipment is beyond the range of most seed laboratories.
Nuclear magnetic resonance (NMR) spectroscopy
. This method is used to measure moisture con-
tent of various crops. It is rapid, nondestructive and accurate over a wide range of moisture contents (Fig.
11.4). The NMR signals must be correlated with moisture values determined by standard reference methods
which must be checked periodically. NMR equipment is also very expensive and not practical for most seed
testing laboratories.
Figure 11.4 Nuclear magnetic resonance (NMR) is a rapid, non-destructive method to determine seed mois-
ture content (also has the capability of oil and protein determination).
Microwave oven method.
The speed at which drying, and therefore moisture determination, can
be accomplished by the use of microwaves make them a potential irst choice method. The wide avail-
ability and low-cost of microwave ovens also makes them ideal as a method for seed drying. In principle,
microwave drying is the same as air-oven drying except that the heating source in the former is microwave
energy. The basic difference is that heating in microwaves is based on a pre-determined time period rather
than a set temperature and time.
Although seed moisture determination using microwaves may seem like a practical, inexpensive and
simple procedure, variable power outputs depending on model and age, in addition to variations due to
sample size and initial moisture content, make standardization dificult. A suggested procedure using micro-
waves for seed moisture determination is described in the Seed Moisture Determination Handbook (AOSA,
2007). For seed laboratories wishing to use this method, it is strongly recommended to calibrate it against
the air-oven method for routinely tested species. It is a useful, quick method for determining seed moisture
content of some grasses when swathing the crop.
THE AIr-oVEn METHod
The air-oven is considered an oficial method by both AOSA and ISTA for determining seed moisture
content in seed testing laboratories. This is because this method has been calibrated against other primary
methods for many crops and achieved reliable, consistent and reproducible results. The following are brief
descriptions of the method.
Equipment:
Seed grinder, controlled oven (capable of being heated at a constant 100 or 130°C ± 1°C),
analytical balance with precision up to 0.001 g, and heat-resistant containers.
Sampling and sub-sample size:
Sample should be truly representative of the entire seed lot. It should
be kept in moisture proof container until the moisture test is performed. Drawing two sub-samples (replica-
