Long-Term Effects of Urea and Green Manure on Rice Yields and Nitrogen Balance
J.K. Ladhaa,
D. Daweb,
T.S. Venturaa,
U. Singhc,
W. Venturaa and
I. Watanabed
a W. Ventura, Crop, Soil and Water Sciences Division, IRRI, MCPO Box 3127, 1271 Makati City, Philippines
b Social Sciences Division, IRRI, Muscle Shoals, AL USA
c International Fertilizer Development Center, P.O. Box 2040, Muscle Shoals, AL USA
d 6-58-18, Jindaiji-Kita, Chofu-shi, Tokyo, 182-0011, Japan

View larger version (25K):
[in a new window]
|
Fig. 1 Rice yield trends in the double-crop system of the long-term biofertilizer experiments conducted at the IRRI research farm. Since N input and solar radiation changed during the experiment, the regression lines are plotted holding N input and solar radiation constant over time at their mean levels in each treatment. See Table 4 for regression coefficients
|
|

View larger version (19K):
[in a new window]
|
Fig. 2 Total soil N of the long-term biofertilizer plots after 7, 16, 20, and 27 rice crops
|
|
Copyright © 2000 by the Soil Science Society of America.