Nk. Savant et Pj. Stangel, UREA BRIQUETTES CONTAINING DIAMMONIUM PHOSPHATE - A POTENTIAL NEW NP FERTILIZER FOR TRANSPLANTED RICE, Nutrient cycling in agroecosystems, 51(2), 1998, pp. 85-94
The rapid rise in fertilizer prices over the past 2 years coupled with
the notoriously low nutrient recovery of fertilizer by lowland rice a
s managed by farmers of most developing countries has prompted a re-ex
amination of urea briquette agrotechnology that improves fertilizer us
e efficiency. Urea briquettes containing diammonium phosphate (UB-DAP)
can be cost effectively produced using a portable fertilizer briquett
er on a small scale (200 kg(-1) h(1)) at the village level and at a pr
ice affordable by small rice farmers. Their improved management consis
ts of hand placement of properly sized (weight) UB-DAP (N:P = 4:1) per
briquette for every four rice hills, and at 7-10 cm soil depth, on th
e day of or the day after transplanting using modified 20 x 20 cm spac
ing (25 hills m(-2)). This management is simple to adopt, saves up to
50% of the labor normally required for its conventional hand placement
, and helps to reduce the lag period of spatial nonavailability of DAP
-P to the rice plants. Results of several farmer-managed field trials
conducted during the 1990-95 wet seasons in India demonstrate that the
UB-DAP management makes the fertilizer agronomically more efficient,
economically more attractive with less risk, and reduced losses of nut
rients as compared with conventional use of prilled urea and single su
perphosphate. The fertilizer use offers women farmers a unique opportu
nity to play an important role in increasing rice productivity. The ma
nagement of UB-DAP can be integrated with plant nutrient recycling and
limited Glircidia green manuring (an agroforestry approach). This int
egrated use of UB-DAP has the potential to increase rice production of
small resource-poor rice farmers with less fertilizer and in sustaina
ble manner in rainfed as well as irrigated transplanted rice ecoregion
s of developing countries, while protecting the environment. Therefore
, the UB-DAP fertilizer can be an important NP source for transplanted
rice in the 21(st) century.