Leaching loss, Plant nutrients, Sandy loam soil, Boro rice.
Leaching loss of NPK under continuous standing water (CSW) condition was studied through an experiment at the net house of the Department of Soil Science, BAU, Mymensingh in the boro season (February to June) of 2009. Soil was collected from the river side of Brahmaputra and it was processed by hand. The soil of the experiment was sandy loam in texture with pH 6.6, total N 0.08%, available P 7.00 μg/g, exchangeable K 0.07 me/100g soil, and available S 7.5 μg/g, respectively (Table 1). Each pot received 6.67 kg soil (weight in dry basis) with an opening at the bottom for collecting leachates. The upper surface area of the pot was 380 cm2. boro rice cv BRRI dhan29 was used as the test crop. One hill (3 seedlings) was planted in each pot. The treatments were T0 (control), T1 (N120, P25, K60, S20 kg/ha, recommended dose of fertilizer (BARC, 2005)), T2 (N180, P37.50, K90, S30 kg/ha, 150% of T1), T3 (75% N of T1 from chemical fertilizer and 25% N from cowdung 2.5 t/ha and PKS of recommended dose from chemical fertilizer on the basis of PKS content in cowdung), T4 (as T1 but N109 kg/ha from USG) and T5 (as T1 but N applied as foliar spray). N, P, K, and S content in cowdung was 1.2, 1, 1.6, and 0.13%, respectively. Fertilizers were applied as per treatments. All the fertilizers except urea were applied as basal to the individual pots and mixed well. The first split of urea was applied as top dressing after 10 days of transplanting boro rice followed by the second and third splits at 35 and 58 days after transplanting. In case of the treatment T4, one piece (0.90 g) of USG was placed in each pot after 10 days of transplanting. In that case, doses of N was 109 kg/ha. In case of foliar application of urea (T5), onethird urea was applied after 10 days of transplanting and rest portion was sprayed at the rate of 3% in 6 equal splits at 10 days interval after the first application. Leachates from individual pots were collected in every day which were preserved in refrigerator and all leachates were mixed together at 15 days intervals and analyzed for N by rapid test method using soil testing kit, P by Olsen method (Olsen et al., 1954), K by flame photometer (Black, 1965) and S by turbidimetric method (Page et al., 1989). But in case of initial soil analysis, total N was determined by micro-Kjeldhal method (Page et al., 1989), texture by hydrometer method (Black, 1965) and pH by glass electrode pH meter method (Black, 1965).