Head rice yield data were described by quadratic relationships
with HMC. These relationships were used to estimate
both the maximum HRY that could have been attained for a
given HRY versus HMC lot set and the HMC at which that
maximum HRY occurred. Based on this procedure, the optimal
HMCs for maximizing HRYs were found to vary from
18.7% to 23.5% for the long-grain cultivars and 21.5% to
23.8% for the medium-grain Bengal cultivar produced in the
mid-South rice producing region. The general ranges of optimal
HMCs were 19% to 22% for long-grain cultivars and
22% to 24% for medium-grain Bengal.
The primary cause of HRY reduction as HMC decreased
below optimal levels was attributed to moisture adsorption
fissuring. The percentage of fissured kernels accounted for
77% of the variation in HRY reduction from the peak HRY
that could have been attained for that particular field.
Maximum HRYs varied from 63.8% to 70.6%. Based on
recent research, the effects of nighttime air temperatures during
kernel development could offer an explanation for this inexplicable
variation and merits further, specific
investigation