S. Peng et al., NITROGEN USE EFFICIENCY OF IRRIGATED TROPICAL RICE ESTABLISHED BY BROADCAST WET-SEEDING AND TRANSPLANTING, Fertilizer research, 45(2), 1996, pp. 123-134
Broadcast wet-seeding is gradually replacing transplanting in irrigate
d rice systems of Southeast Asia. Previous studies reported higher fer
tilizer-N use efficiency for broadcast-seeded than transplanted rice d
espite similar grain yields in treatments that received N fertilizer.
To re-examine this issue, we compared crop performance and the recover
y efficiency (epsilon(r) Delta N uptake per unit N applied), agronomic
efficiency (epsilon(a), Delta grain yield per unit N applied), and pa
rtial factor productivity from applied N (PFP, grain yield per unit N
applied) in broadcast-seeded and transplanted rice across a wide range
of N fertilizer rates at research stations and in farmers' fields. Ri
ce crop established by broadcasting had more rapid leaf area developme
nt, dry matter accumulation, and N uptake than transplanting during ve
getative growth stages, but slower growth rates and N uptake after pan
icle initiation, particularly during the grain filling period. Without
applied N, grain yield and N accumulation at maturity were significan
tly lower in broadcast-seeded than transplanted rice, whereas yields a
nd N uptake were comparable for both planting methods with equivalent
rates of applied N. Although both epsilon(r) and epsilon(a) were highe
r for broadcast-seeded than transplanted rice, this advantage was an a
rtifact of lower yields and reduced N uptake by broadcasting without a
pplied N rather than improved performance with applied N. In contrast,
PFP values were similar for broadcast-seeded and transplanted rice at
comparable fertilizer-N rates and in the absence of lodging. We concl
ude that the PFP from applied N provides a more relevant measure of N
use efficiency of different crop establishment methods, and that the s
ystem-level N use efficiency of broadcast-seeded rice was not greater
than that of transplanted rice.