Vergara - 1976 - Physiological and morphological adaptability of ri

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6. Nitrogen response of 1R8 and [R10 in fannefs field.
Calamba. Laguna. Philippines. 1968,73. DBH = days
before harvest.
than did [R20 (Fig. 6). The nitrogen response of IRS was somewhat higher
than that of [R20 During the wet season. solar energy received by IRS and
IRZO in the ripening period was similar Therefore. nitrogen responses of these
varieties were also similar (Fig 6). In the wet season, 1R8 suffered from more
damage due to diseases and insects than did IRZO. Othem-"ise. the nitrogen response
of [R8 would have been higher than that of lR20.
Seasonal effects on nitrogen response clue to the solar energy level were evident.
howexrer. in the experiments conducted in the farmer's field. as in those recorded
at IRRI and BPI stations.
The data show that nitrogen response depends not only on the level of solar
energy but also on varietal resistance to insects and diseases.
Management factors
Experiments were conducted at the Institute farm during the 1966 crop seasons
to determine the nitrogen response and _vield potential of two varietal types
under three levels of management (insect and weed control) practices. The
degree of insect control and fertilizer applications differed between dry and wet
seasons. Weed control levels were the same for both seasons.
The varieties were IRS. representing modern varieties with good plant type.
and Sigadis, representing old varieties with poor plant type.