Soil Management
Soil Management sum total of all tillage operations, cropping systems, fertiliser application, liming and other treatments applied to soil for improving soil condition of crop production. Due to lack of proper management practices, yield level of the soils of Bangladesh is generally decreasing. Moreover, poor management of soil creates undesirable environmental conditions. The truth lies behind this imperfect management is the excessive population pressure. In 1991 the area of arable land available on per capita basis was only 0.08 ha. This immense pressure on arable lands also affects the other socioeconomic aspects of soil management. The soil management in Bangladesh is classified into fertility management, management of soil physical properties and management of problem soils.
Fertility management fertility status of Bangladesh soil is moderate to low. The organic matter content is not high and it is below 2%. In floodplains and terrace soils nitrogen content is low. About 5.6, 7.5 and 8.7 million- ha land of Bangladesh is deficient in phosphorus, potassium and sulphur respectively for upland crops. Zinc deficiency is present in about 1.74 million ha and boron deficiency is now coming to attention. Major cultivable crops of Bangladesh remove huge amount of nutrient elements from soil. HYV rice uptake 108, 18, 120 and 11kg/ha N, P, K and S from soil. Wheat also uptake high amount of N and K from soil. For the present level of production of crops about 1.0 million tons of N, P, K and S are annually removed from soil.
Compared to other Asian countries during the past few years, the total fertiliser nutrient use in Bangladesh has remained static. Depending on the existing soil and land types, and varied cropping patterns it has been estimated that Bangladesh need at least 4.0 million tons of fertilisers but currently applied about 2.25 million tons, that is 56% of the total demand. This creates continuous stress on the soils of Bangladesh.
The major fertilisers are in use in Bangladesh are urea, triple super phosphate (TSP), gypsum, muriate of potash (MP), diammonium phosphate (DAP) and zinc sulphate.
The total distribution of fertilisers from 1971 to l994 shows that urea occupied 68.7%, TSP 22.2% and MP 5.2% of total fertiliser used. Trends of fertiliser use in Bangladesh show that the application of nitrogen fertiliser is the highest. The use of sulphur and zinc in agriculture started from 1980-81 and from then the use of these two increases gradually. Diammonium phosphate (DAP) as a source of nitrogen and phosphorus is now becoming popular in Bangladesh.
Besides inorganic fertilisers, manures are also important in Bangladesh agriculture. Domestic animals produce a huge amount of excreta (dung and urine) per year. Cow dung is the most important animal manure. But a large portion of it is mainly used as fuel in Bangladesh. These days biogas plant is getting popular in Bangladesh. The remaining decomposed organic matter of biogas plant can be applied directly to soil. The other biofertilisers such as inocula of Rhizobium are also commercially available.
Management of soil physical properties rice is the main cultivated crop of Bangladesh. It grows on submerged soil. The common practice of land preparation for rice culture is puddling. It is the process of complete destruction of soil structure by repeated plowing by country plow and harrowing in submerged condition. A plough pan (5 to 10 cm depths) is formed due to puddling of soil. This compact layer is favourable for rice cultivation but not for other arable crops. For the cultivation of other crops soils are usually ploughed and harrowed for several times.
Recently research on no-till farming has initiated in Bangladesh. This technique is not known to many farmers. Reduction of tillage cost in no-till farming system is promising for Bangladesh agriculture.
Management of problem soils the three major problem soils of Bangladesh are: saline soil, acid sulphate soil and peat. On an average about 0.82, 0.07 and 0. 13 million ha are occupied by Saline soil, Acid Sulfate soil and Peat, respectively. There are different methods (eg eradication, conversion, crop selection etc) for managing these soils, however, very little research has been carried out so far in Bangladesh to manage these soils properly. [TH Khan and SM Fazle Rabbi]
