Americas and Oceania Group - International Plant Nutrition Institute

Asia and Africa Group
South Asia
North & East India Regions and Bangladesh:
Dr. Kaushik Majumdar
Site-Specific Nutrient Management for Rice-Maize Cropping Systems in Bangladesh
Project Leader: Jagadish Timsina, IRRI, Dhaka, Bangladesh. E-mail: j.timsina@cgiar.org
Site-specific nutrient management (SSNM) trials in rice-maize and rice-potato-maize systems were
conducted in Comilla, Rajshahi, and Rangpur districts of Bangladesh. Omission of N reduced boro rice yield
by 0.71, 2.13, and 1.34 t/ha in Comilla, Rajshahi, and Rangpur, respectively. However, the yield reduction
due to omission of P and K was significant in Rangpur only. There were poor or no relationships between
boro rice yield and total N, available P, and exchangeable K. The experimental data suggest that the estimated
N rates would be between 90 to 110 kg/ha for the three districts. A maintenance dose of 6 to 10 kg/ha P and
40 kg/ha K may be recommended for boro rice in the rice-rice cropping system. Omission of N, P, and K
significantly reduced the grain yield of rabi maize in all three locations. Yield decline due to K omission was
higher than P omission in Comilla, but not in Rajshahi and Rangpur. Based on the lower yield observed in the
N omission plots, N rates for rabi maize would be between 200 to 220 kg/ha in all three locations. The mean
P dose for Comilla and Rangpur districts would be 16 kg/ha and that for Rajshahi would be 22 kg/ha. The
mean K doses for Comilla, Rajshahi, and Rangpur would be 136, 65, and 36 kg/ha, respectively. Apparent K
recovery in Comilla was highest among the three districts indicating that the soils are more deficient in K than
in the other two districts.
In the rice-potato-maize system, omission of N decreased maize yield by 2.2, 2.6, and 1.0 t/ha in Comilla,
Rangpur, and Rajshahi, respectively compared with the NPK treatment. Omission of P significantly decreased
maize yield in all districts, but K omission significantly decreased yields in Comilla and Rajshahi only.
The yield responses of kharif maize to N, P, and K were much smaller than in rabi maize. The low yield
responses to N, P, and K in kharif maize were due to high amounts of fertilizer applied to the previous potato
crop. Omission plot trial data from this experiment will be useful for developing site-specific fertilizer
recommendations for the rice-maize system and for improving the Nutrient Manager and Nutrient Expert
decision support tools that are currently under development and evaluation for Bangladesh. Bangladesh-05
Assessment of Soil Potassium Supplying Capacity from Soil Nutrient Reserves and Dissemination of Nutrient
Management Technologies through Nutrient Manager
Project Leaders: Jagadish Timsina & Saiful Islam, IRRI-CIMMYT IRRI-Bangladesh Office, Dhaka, Bangladesh.
E-mail: timsina@cgiar.org
Project Cooperators: Salim Uddin (BAU), M.A. Saleque (BRRI), and R. J. Buresh (IRRI).
The current project was initiated to estimate the magnitude and variation in soil K supplying capacity
across a range of soils growing intensive rice-maize system in Bangladesh. Eighteen soil samples were
collected from Dinajpur, Rangpur, Bagura, Rajshahi, Nawabganj, Sirajganj, Tangail, Faridpur, Jhinaidah,
Sathkhira, and Comilla districts, representing diverse mineralogy and properties related to soil K supplying
capacity. The samples were analyzed for pH, organic carbon, total N, available P, exchangeable K, S, Zn, Mg
and Ca. The exchangeable K in the samples ranged from 0.149 to 0.317 cmol/kg.
A pot experiment with rice was conducted in the above soils with two treatments, Zero K (K0) and 100 mg
K/kg soil (K100), in four replications. Other limiting nutrients were applied at a set dose so that the plants are
not in deficient in any other nutrient except K. Rice seeds were sown and allowed to grow up to the booting
stage, and then harvested. Plant height, numbers of tillers, and dry weight of plant and root were determined
from each pot.
Dry matter yield in the K applied pots was significantly higher than the K omission pots in 7 out of the
18 studied soils. There was poor relationship between soil exchangeable K contents and dry matter yield
IPNI Interpretive Summaries 87