Yoshida - 1981 - Fundamentals of Rice Crop Science

136 FUNDAMENTALS OF RICE CROP SCIENCE
3.10. Relationship between leaf conductance
and net photosynthetic rate of rice leaves
(Yoshida and Coronel 1976).
soils; nitrate is the major form in upland soils. Although relatively low concentrations
of ammonia are toxic to many upland crops, relatively high concentrations
are tolerated and used efficiently by rice.
Studies to determine the relative effectiveness of ammonia and nitrate as
nitrogen sources for rice often encounter difficulty with changes in the pH of the
culture solution. The changes result from the selective absorption of ammonia or
nitrate, as illustrated in 3.4.4. The secondary effect of pH changes, such as iron
Table 3.15. Average response of lowland rice, upland rice, barley,
and wheat to the application of nitrogen, phosphorus, and
potash in Japan. a
Yield index b
Crop Compost No PK NK NP Trials
fertilizer
(no.)
Lowland Without 78 83 95 96 1,161–1,185
rice
With 80 84 96 96 456–466
Upland
rice Without 38 51 84 75 117–126
With 58 70 91 95 18
Barley and
wheat Without 39 50 69 78 822–841
With 48 59 88 95 392–408
a Imai and lmaizumi (1956). b The figures are indices taking the
yield of the complete-fertilizer plot as 100.