Rice Responses to Nitrogen Under High Solar Radiation and Intermittent Flooding in Peru¹

Abstract

The purpose of this study was to characterize the varietal responses of rice (Oryza sativa L.) to N fertilization in a tropical desert climate where extremely high N application rates are needed to attain maximum yields. Eight rice cultivars of contrasting plant type and growth duration were tested at applied N levels of 0 to 480 kg N/ha in a field experiment with an intermittently flooded water regime. Among the semi‐dwarf cultivars, the earlier maturing ‘IR8x2019; produced a maximum yield of 11.7 ton/ha at 480 kg N/ha and the later maturing ‘IR5’ produced a maximum yield of 9.9 ton/ha at 400 kg N/ha. Among the tall‐statured cultivars of the traditional plant type, the earlier maturing ‘CEL 895’ produced a maximum yield of 10.6 ton/ha at 320 kg N/ha and the later maturing ‘Minabir 2’ attained its highest yield of 7.9 ton/ha at 40 kg N/ha. Yield responses to N were primarily a function of effective tillering capacity and not of panicle size. Increases in dry matter production from panicle initiation to harvest were highly correlated with grain yields. A 0.85% N content in the above‐ground parts at harvest was associated with maximum yields as well as a total N uptake of approximately 180 kg N/ha, suggesting the existence of an internal N requirement for rice in this environment. The apparent recovery of added N averaged 30%, which is considerable lower than in constantly flooded environments. The results indicate that: i) the shorter the growth duration of a cultivar within a specific plant type, the higher the yields and N response; ii) the extremely high N rates required are due to high levels of N uptake and low fertilizer recovery intermittent flooding.

Rice Responses to a Short‐Duration Green Manure. II. N Recovery and Utilization1

“…Green manure density Green manure duration Fallow with vs. without inorganicN above this ratio ( Table 5). Examination of the original reports surveyed by van Keulen and van Heemst (1982) showed that, for rice, the ratio exceeded 0.075 Mg kg-1 N in two cases (Williams et al, 1972;Sanchez et al, 1973). However, ratios closer to 0.070 Mg kg-1 N were more common.…”

Season and plant type affect the response of rice yield to nitrogen fertilisation in a semi-arid tropical environment

“…Response of grain yield to N rate varied with genotype in Experiment 1 (dry season) such that yield in the early-maturing genotypes (Newbonnet and Lemont) was more responsive to N rates >70 kg/ha than in the late-maturing genotype (Starbonnet). Similarly, Sanchez et al . (1973) found that within a specific rice plant type in Peru, the earlier maturing genotype produced a higher grain yield in response to N than its later maturing counterpart, suggesting that early maturity increases the responsiveness of grain yield to N in a high solar radiation environment.…”

“…Generally, short-statured and earlymaturing genotypes are more responsive to N than tall-statured and late-maturing genotypes (De Datta et al . 1968;Sanchez et al . 1973;De Datta and Malabuyoc 1976).…”

Environmental Impact of Common agricultural policy

“…Apart from a better control of lodging, this is because modern varieties require considerably less nitrogen per kg grain yield than traditional varieties, but take up nitrogen at least as efficiently (cf. Sanchez et al, 1973). This increased efficiency is a general phenomenon because it is directly related to the much better seed/straw ratios of modern varieties compared with traditional ones.…”