Direct sowing of rice into drained soil is a relatively new farming practice,
replacing transplanting, being developed for use in External Low Input
Sustainable Agriculture in Korea. Field experiments were conducted to
investigate the importance of tillage, sowing rate, and top-dressing of
fertiliser nitrogen (N) to rice growth and grain yield in a direct-sown,
rice–vetch cropping system.
From 1993 to 1997, Chinese milk vetch
(Astragalus sinicus L. Vetch) was grown during the
winter season (October–May) at Uiryong, Korea. Until 1995 transplanted
rice (Oryza sativa L.) was grown during the summer
season, but in 1996 and 1997 the direct-sowing method was used. In 1996, the
treatments applied to rice were either tillage or no-tillage of the paddy
before the rice crop was sown, combined with 2 rates (0 or 2
g/m2) of fertiliser N top-dressed onto the paddy
just after the panicle initiation stage. In 1997, the treatments were either
tillage or no-tillage of the paddy before the rice crop, combined with 2 rice
sowing rates (400 or 800 seeds/m2), and 3 rates (0,
2 or 4 g/m2) of fertiliser N top-dressed just after
the panicle initiation stage.
Rice yielded 243–435 g/m2 in 1996 and
493–678 g/m2 in 1997, the lower yield in 1996
was attributed to fewer established seedlings and productive panicles. There
was no effect of tillage treatment. Across years, yield was correlated with
shoot N content, and grain N-use efficiency exceeded 50 g grain/g shoot N
content. Rice residues contained about 5 g N/m2 and
vetch residues released 6–8 g N/m2 during the
4 weeks after submergence, therefore the release of N from residues was
potentially sufficient to supply the rice crop demand. In both years, however,
the yield of unfertilised rice was N limited, so increasing the shoot N
content appeared to be the most important issue to be resolved in sustaining
yield in External Low Input Sustainable Agriculture. A low rate of top-dressed
fertiliser N (2–4 g N/m2) increased yield by
increasing the number of panicles and spikelets, and to a lesser extent,
1000-grain weight. Growing rice using no-tillage practices did not limit the
yield of rice, except in 1996 when no fertiliser N was applied and the N
uptake by rice was low. A high sowing rate combined with top-dressed
fertiliser N in 1997 reduced yield through crop lodging and an increase in the
number of unproductive tillers. This problem may be overcome by the use of a
variety less susceptible to lodging.
Peran Eksopolisakarida Azotobacter dan Bahan Organik untuk Meningkatkan Nodulasi dan Biomassa Kedelai pada Dua Ordo Tanah
