Vergara - 1976 - Physiological and morphological adaptability of ri

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Nitrogen applied ( lag/ho)
l3. Effect of plant type on nitrogen response of upland
rice in Peru (adapted lrom Sanchez and Nurefia.
I972).
to the other in the wet season as much as does the distribution of rainfall.
Therefore, solar energy appears to be less critical for upland rice than the
moisture supply from rain. Furthcnnore. high solar energy may even be undesirable
for upland rice if the moisture supply from rain is not adequate and
unifomi. Therefore. upland rice farming done under the shade of trees may
be helpful in minimizing susceptibility of upland rice to drought conditions
(Yoshida ct al. 1974).
Among the management factors that affect nitrogen response in upland rice.
weed control is highly critical. Studies conducted at IRRI demonstrated that
grain yield reduction and reduction in nitrogen response are more critical under
weedy conditions than when weeds are controlled adequately. Detailed results
are reported elsewhere (De Datta. 1974'. Okafor and De Datta. I976). Other
limiting factors that may affect nitrogen response in upland rice but have not
been researched adequately are insects and soil problems (iron deficiency,
manganese and aluminum toxicity. and zinc deficiency).