Functions of Nitrogen in Crop Plants - Nitrogen Management in Crop Production - page 11

TABLE 1.3
Plant Height of 19 Upland Rice Genotypes as Influenced by N
and Genotype Treatments
Genotype Plant Height (cm)

CRO 97505 106cde

CNAs 8993 104cde

CNAs 8812 93 g

CNAs 8938 99efg

CNAs 8960 112abc

CNAs 8989 99efg

CNAs 8824 94 g

CNAs 8957 105cde

CRO 97422 108bcd

CNAs 8817 109bcd

CNAs 8934 105cde

CNAs 9852 104cde

CNAs 8950 106cde

CNA 8540 93 g

CNA 8711 118a

CNA 8170 93 g

BRS Primavera 115ab

BRS Canastra 94fg

BRS Carisma 102def

Average 103

F-test
N level (N)

**

Genotype (G) **

N × G NS

CV (%) 4

Source: Adapted from Fageria, N. K., O. P. Morais, and A. B. Santos. 2010. Nitrogen
use efficiency in upland rice genotypes. J. Plant Nutr . 33:1696-1711.
Note: Means followed by the same letter in the same column are not significantly
different at the 5% probability level by Turkey's test. Plant height values are
across two N rates (0 mg N kg −1 and 400 mg N kg −1 ).
**, NS: Significant at the 1% probability level and nonsignificant, respectively.

in mechanized agriculture in South America as well as in the United States. Under direct seed-
ing, tillering capacity rarely affects grain yield within conventional seeding rates because the total
panicle number per square meter depends more on the main culm than on tillers (Yoshida, 1981).
Low seed rate is required more, however, by heavy-tillering cultivars as compared to low-tillering
cultivars. Jennings et al. (1997) reported, however, that a combination of high tillering ability and
compact or nonspreading culm arrangement is desirable. Compact culms that are moderately erect
allow increased solar radiation to tillers and less mutual shading per unit of land area.
N fertilization significantly increases tillering in cereals, especially in rice (Fageria et al., 2003).
Figure 1.7 shows the increase in tiller number with increasing levels of N in lowland rice grown on
an Inceptisol of central Brazil. Murata and Matsushima (1975) reported that an N concentration of
more than 35 g kg −1 (3.5%) is necessary for active tillering; at 25 g N kg −1 (2.5%), tillering stops, and
below 15 g N kg −1 (1.5%), death of tillers takes place. Data in Table 1.4 show that N significantly
increased tillering in lowland rice. About 66-96% of the variation in tillering was apparently due