Yoshida - 1981 - Fundamentals of Rice Crop Science

92 FUNDAMENTALS OF RICE CROP SCIENCE
Calculation:
Maximum grain yield
= (400 × l0 4 × 0.45 × 0.945 × 0.90 × 0.26 × 0.83 × 0.75
– 1500 × 0.015 × 3900) × 40/3900
= 1640 g/m 2 (dry weight)
= 19.1 t/ha (brown rice at 14% moisture content).
= 23.8 t/ha (rough rice at 14% moisture content). (2.11)
Method 2. The equation 2.8 can be rewritten as:
(2.12)
where T is the effective grain-filling period discussed in Chapter 1.
Assumptions
(a) The effective grain-filling period is 35 days for temperate regions and 25
days for the tropics.
(b) Two E µ values are used: 3.5% represents the high efficiency and 2.5%, the
moderately high efficiency; 3.3% is the highest recorded E µ in Japanese IBP trials
(Kanda 1975).
(c) The heat of combustion for the grain is 4,000 cal/g.
(d) The ratio of husk weight to the dry grain weight is 20%.
(e) The contribution of the carbohydrate stored before flowering is negligible
when the maximum potential yield is to be achieved.
Calculation:
When appropriate corrections are made for weight (× 10 -6 ), area (× 10 4 ), husk
(× 1/0.8), and moisture content (× 1/0.86), grain yield will be computed as:
(2.13)
(2.14)
The E µ value of 4.0% is higher than the maximum recorded value of 3.3% for rice.
Substituting 4.0% for the E µ value in equation 2.13 gives 20.4 t/ha when T is 35
days and 23.2t/ha when T is 40 days. Thus, methods 1 and 2 give basically similar
estimates of the maximum potential yield. That implies that the efficiencies of
component processes along the flow of energy are well integrated into a single E µ
value. An important assumption in the foregoing estimates is that high photo-