Introduction

Direct seeding culture of paddy rice

Paddy rice production in Japan

Paddy rice is a staple food and is grown mainly by transplanting culture in Japan. Transplanting culture method is applied in about 99.7% of total rice cultivation area (about 2 million ha). Recently, however, several direct seeding culture methods has been developed aiming to reduce production costs.

Direct seeding culture in Japan

Direct sowing of paddy rice into puddled and leveled soil (named as DIPPS) is one of those new methods. It is one of modified method of direct seeding in submerged paddy field (water seeding), and has advantages over former method as described below.

What's DIPPS?

DIPPS had been developed to improve unstableness of seedling establishment due to the floating of seedling in the former method. Floating of seedlings leads not only to poor seedling establishment but also to low lodging resistance. That is because in the floated seedling the bases of roots are not located in a soil but above the soil, and such rooting system makes plant supporting force of roots much weaker.

In order to prevent floating of seedlings, seeds are sown into soil in DIPPS. But rice plant can not germinate and grow well when sown into submerged soil. DIPPS method became feasible only after coating technology of seeds with calcium peroxide (CaO2) which promotes germination and seedling growth had been established.

Advantages of DIPPS over former direct seeding method

Why DIPPS?

Direct seeding in well-drained paddy field is the major method of direct seeding culture in Japan (applied in about 50% of direct seeding culture area). In this method, paddy field is maintained in drained conditions before submerging until seedling establishment.

This method requires low precipitation during the period of tillage, seeding and early seedling growth. For example, precipitation after seeding affects germination. It also requires such soil condition that 1) water percolation rate is small even without puddling and 2) ground water level is low at seeding time and becomes higher after submerging period. Unfortunately, these requirements are satisfied in a limited area in Japan.

DIPPS does not require such soil conditions. In addition, as submerging starts from the beginning in DIPPS, it is advantageous especially in cold district, because soil temperature is kept higher in DIPPS than in direct seeding in well-drained paddy field.

Problems to be solved


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