Abstract
Experiments were carried out in the three permanent manurial plots of Bangladesh Agricultural University farm soil (Aeric Haplaquepts; Sonatola silt loam) under different fertility and water management conditions. The objectives of the experiments were to study the nutrient dynamics and under ultimately making a nutrient balance for paddy soils normal practices of rice production. The results show that the soil remained under reduced condition for 8-10 months of the year due to the presence of shallow ground water level, higher amount of medium and fine soil pores, low permeable subsurface layer and high rainfall/irrigation etc. (Analysis of soil solution shows higher concentration of nutrients in wet period than in dry period. Application of urea increased the concentration of some basic cations in the soil solution and enhanced their loss by percolating water. Submergence of soil reduced the concentration of S04 and NO3 but increased
2-
P in soil solution. The content of Fe and Mn in soil solution was low and variable in different periods of the year. The balance of F, S, Zn and Cu was negative when they were applied and positive when they were applied. A fractionation study of soil Zn shows that a major portion of native Zn was in oxide and silicate bound forms, whereas the added Zn was tran -formed into organically bound form. Rain and irrigation
waters added some amount of nutrients but their resultant
effect on nutrient loss was greater.