Rice is the staple food in Asia and about 75% of it is produced in an irrigated lowland where transplanting is the major method of crop establishment. This system, however, is highly laborious and costly. And, with the free-market orientation on rice as encouraged by WTO, it is logical to produce rice at low cost to prevent excessive importation of cheaper but with high quality rice. It is necessary therefore to improve direct seeded rice culture, which offers low labor cost, and develop a high efficiency of fertilizer nitrogen (EFN) to sustain its productivity. This study was conducted to evaluate the growth, yield and N use efficiency of single basal application of controlled release fertilizer (CRF) in direct seeded rice (DS). The data used in this paper are taken from two sources; 1) from the summarized published data and 2) from results of field study carried out in Yamagata, northeast of Japan.
Source 1
1. The results obtained from publications in Japan showed
that average yield of rice plant was 6% higher in CRF applied plots than
in conventional fertilizer (CF) though the N application rate was 14% lower
than the CF. It could be attributed to the increased number of grains m-2
in CRF applied plots.
Source 2
1. The N application rate of CRF was reduced by 30% compared
with that of ammonium sulfate (AS) and N recovery rate of rice was determined
by the direct method using 15N. EFN was calculated as follows; EFN=(% of
N recovery) x (efficiency of utilization) (Yoshida,1981).
2. No significant difference was observed in the yield
of DS under AS and linear formulation CRF, LP100, but was found significantly
lower in sigmoidal formulation CRF, LPS100, due to smaller number of grains
m-2 production.
3. There was no significant difference in fertilizer
N recovery of rice at maturity stage between DS and transplanted rice (TPR).
Among N sources, highest recovery rate of fertilizer N was obtained in
LPS100 followed by LP100 and AS.
4. Two years average of EFN values in LPS100 was 34.4
and that of LP100 and AS were 27.0 and 22.2, respectively. In addition,
DS shows slightly higher EFN values compared with TPR.