Assessment of Soil Potassium Supplying Capacity from Soil Nutrient Reserves and Dissemination of Nutrient Management Technologies through Nutrient Manager

Assessment of Soil Potassium Supplying Capacity from Soil Nutrient Reserves and Dissemination of Nutrient Management Technologies through Nutrient Manager®, 2012

The current project was initiated to estimate the magnitude and variation in soil K supplying capacity in different soils of Bangladesh using a plant-based approach. The results are expected to help develop field-specific nutrient recommendation tools, like Nutrient Manager® (NM) for rice and Nutrient Expert® (NE) for maize, by International Rice Research Institute (IRRI) and IPNI, respectively, in collaboration with International Maize and Wheat Improvement Center (CIMMYT).

Eighteen soil samples were collected from Dinajpur, Rangpur, Bagura, Rajshahi, Nawabganj, Sirajganj, Tangail, Faridpur, Jhinaidah, Sathkhira, and Comilla districts representing diverse soil mineralogy and K fertility levels. Pot experiments with rice and maize were conducted with two treatments (zero-K and 100 mg K/kg soil) and four replications, while other limiting nutrients were applied in ample quantity to avoid any deficiency except that of K. In 2012, up to four rice crops and up to five maize crops were cultivated in pot experiments. Each rice crop was harvested at booting stage and number of tillers, plant height, straw and root dry weight were recorded. Maize was harvested at V10 stage and plant height as well as plant and root dry matter were recorded. The rice crop in K-applied pots accumulated higher dry matter (biomass) than K-omission pots in 7, 10, 13, and 14 of the 18 pots after the first, second, third, and fouth crop, respectively; and the dry matter (biomass) of maize in K-applied pots was significantly higher than in K-omission pots in 1,12, 5, 11, and 11 out of 18 pots after the respective five crops.

For both rice and maize crops, the ranges of exchangeable K in studied soils were 0.061 to 0.410 cmol/kg, 0.062 to 0.410 cmol/kg, and 0.044 to 0.266 cmol/kg after the first, second and third crops, respectively, while the non-exchangeable K ranges were 0.062 to 0.410 cmol/kg, 0.038 to 0.359 cmol/kg, and 0.016 to 0.376 cmol/kg after the first, second and third crops. Farmer participatory trials have been established at 12 locations in Rajshahi, Rangpur and Comilla districts to confirm results from the pot study for soil K supplying capacity and also for evaluation and validation of NM and NE for boro rice and rabi maize, respectively. Bangladesh-06