Yoshida - 1981 - Fundamentals of Rice Crop Science

MINERAL NUTRITION OF RICE 149
Table 3.23. Partial productive efficiency of phosphorous for
grains. a Partial productive efficiency
Growth
period
Low P Medium P High P
29 Jun-8 Jul 144 270 193
8 JuI-17 JuI 245 167 300
17 Jul-29 Jul 213 285 197
29 JuI-7 Aug 139 64 51
7 Aug-19 Aug 136 74 30
19 Aug-28 Aug –1433 27 –21
a Hayashi et al (1951).
and because the total phosphorus requirement is small relative to nitrogen. Furthermore,
if sufficient phosphorus is absorbed at early growth stages, it can be
easily redistributed to growing organs. Rice's need for phosphorus at early growth
stages advocates for basal application.
3.8.4. Varietal performance on phosphorus-deficient soils
Clear varietal differences in rice's ability to absorb soil phosphorus and in growth
and yield on a phosphorus-deficient acid soil in Thailand have been reported
(Koyama et al 1973). Varietal differences in grain yield were most remarkable
when no phosphorus was applied and progressively decreased when phosphorus
application was increased (Fig. 3.17). Variety Dawk Mali 3 grew better and
yielded higher when no phosphorus was applied. This was associated with higher
phosphorus absorption.
Studies showing varietal differences only in soil culture (pot or field) and not in
solution culture experiments led Koyama et a1 to conclude that varietal differences
in the ability to grow better on a phosphorus-deficient acid soil is caused by
differences in the ability to extract soil phosphorus. Subsequently, similar varietal
differences were observed on a wide range of varieties (Ponnamperuma 1976a).
3.9. POTASSIUM
3.9.1. Occurrence of deficiency
Potassium deficiency occurs to a limited extent in lowland rice. Low potassium
content or potassium deficiency is often associated with iron toxicity, which is
common on acid latosolic soils and acid sulfate soils.
Potassium deficiency is frequently accompanied by Helminthosporium leaf
spots, which is a common symptom of Akiochi on sandy soils in Japan and Korea.
Potassium deficiency also occurs on poorly drained soils, partly because toxic
substances produced in highly reductive soils retard potassium uptake and partly
because less soil potassium is released under poorly drained conditions.