Vergara - 1976 - Physiological and morphological adaptability of ri

NITROGEN RESPONSE or RICE l.\‘ TROPICAL CONDITIONS 521
GFOIH
8
yieldtt/hol
o 50 4 l 200 =50
Nnrogen Upplied I
kg/hcl
8. Nitrogen response (av. of two varieties) at two
management levels. ALCRIP. Ilyderabad. I973 wet
season (Shastry et al.. I974}.
affect nitrogen response of rice varieties. Iletailed results from these experiments
are presented elsewhere (De Datta and Sharma. ]9(i8').
Recent data from the IRRI Statistics Department (Ciomcz. 1974. nnpilb/islzezi)
also showed that the degree of weed infestation and its control affect nitrogen
response in rice. In experiments conducted during the I973 wet season by All
India Coordinated Rice Improvement Project in Hyderabad. using a package of
practices called "minikits," 50 kg N/ha with good management gave yields
similar to those at I50 kg Nfha under a stih-optimal management level (Fig. 8').
The data in Figure 8 are averages for two modern varieties. Sona and Jaya.
Management factors in the minikits inxtolved age of seedlings, depth oftransplanting.
plant spacing. and water management (Shastry et al.. I974).
In a recent stud)‘ by the lRRl Agricultural Economics Department. nitrogen
responses were recorded for modern varieties in some selected villages in South
and Southeast Asia in the dr_\' and wet seasons (Anden and Barker. I973).
The villages were classified into three groups according to the range of nitrogen
Lise: low N, 0-60; moderate N, 30-100; high N. 50-190 kg/ha (Fig. 9). On
the average for the wet season. the fanners in the first group using 60 kg N/ha