Soil Fertility Management in BangladeshDr Md. Altaf HossainPrincipal Scientific OfficerSoil, Land Survey & Classification SectionSRDI, BangladeshEmail: altajolly63@yahoo.com

Geography of BangladeshBangladesh is situated between 2034 and 2638 north latitude and 8801 and 9241 east longitude. It is the fifth most populous country in Asia and ranks eighteenth in the global context.

The topography is flat with elevation not exceeding 10 meters above mean sea level. The non-undulated topography is broken in the southeast by the Chittagong Hill Tracts and hills in the northeastern part of the country. Floodplain and piedmont plains occupy almost 80 percent of the land area. Slightly uplifted fault blocks (terrace) occupy about 8 percent and hills occupy about 12 percent of the land.

Soil and Land Resources of BangladeshPhysiography: 15 (SRDI, 2013)1. Tipam-Surma Hills (High Hills) 2. Dupitila- Dihing Hills (Low Hills)3. Modhupur Clay Upland4. Himalayan Piedmont Plain5. Northern-Eastern Piedmont Plain6. Tista River Floodplain7. Brahmaputra-Jamuna River Floodplain8. Surma-Kusiyara River Floodplain9. Meghna River Floodplain10. Ganges River Floodplain11. Peat Basins12. Ganges Tidal Floodplain13. Meghna Estuarine Floodplain14. Chittagong Coastal Plain15. St. Martins Island

Soil series distribution- ( )- ( ) (, ) - - - :

High land: Above normal flood level Medium High land: Inundated upto 3Medium low land: Inundated upto 3-6Low land: Inundated upto 6-9 Very low land: Inundated >9Land type class: Based on inundation level during monsoon

Land type class in Bangladesh (%)

Soil textural class of BD (%)

Drainage class of Bangladesh (%)

Water recession class of BangladeshVery early-Water recedes within Ashwin from land surface Early- Water recedes after Ashwin but within kartik from land surface Normal- Water recedes after kartik but within Ogrohayon kartik from land surface Late- Water recedes after Ogrohayon but within 2nd week of Paush from land surfaceVery late- Water recedes after 2nd week of Paush from land surface

Water recession class of Bangladesh (%)

Soil Fertility in BangladeshSoil Fertility capability or ability of soils to supply elements essential for plant growth without a toxic concentration of any element. It is the inherent capacity of a soil to supply 14 of the 17 essential nutrient elements to the growing crop. It is the quality of soil that enables it to provide compounds or elements in adequate amounts and in proper balance for the growth of specified plants when other growth factors like light, moisture, temperature and the physical conditions of the soils are favourable. As such, a soil can be fertile for one plant and at the same time be unfertile for another plant. On the other hand soil productivity is a measure of the soils ability to produce a particular crop or sequence of crops under a specified management system. The major constraints of bangladesh soils as regards general fertility and health are briefly enunciated below.

Causes of Fertility degradationIntensive Crop Cultivation without balanced inorganic and organic fertilizerAdulterated FertilizerPoor knowledge and resource base of majority farmersRemoval of crop residues from crop field (fuel purpose)

SOIL REACTIONSoil Reaction The average pH of Bangladesh soils could be taken on the acidic side of the pH scale, between 5.5 and 6.5. The Gangetic alluvium soils, particularly the calcareous one, have pH greater than 7.0, reaching at times up to 8.5. These contain free carbonates and bicarbonates. Soils in plateaus, raised lands and hills are usually acidic in nature. Because of pH variations, the nutrient availability, particularly that of phosphorus (P) and some micronutrients, is affected. Otherwise, lowland rice cultivation is not affected by original soil reaction, as the pH tends to come to a value between 6.5 and 7.5 on submergence. liming is needed for crops other than tea in soils having pH less than 4.5, which is more prominent in acid sulphate soils and hill soils. Upland crops are adapted to local soil ph. Soils are categorized as (i) extremely acidic - having pH below 4.5; (ii) strongly acidic - pH between 4.5 and 5.5; (iii) moderately acidic - pH between 5.6 and 6.5; (iv) neutral - pH between 6.6 and 7.3; (v) moderately alkaline - pH between 7.4 and 8.4; (vi) strongly alkaline - pH between 8.5 and 9.0; and (vii) very strongly alkaline - pH >9.0

Organic MatterOrganic matter status Organic matter (OM) status of Bangladesh soil is one of the lowest in the world. The average OM content of Bangladesh soils is less than 1%, ranging between 0.05 and 0.9% in most cases. Soils of peat lands and some low-lying areas usually contain OM higher than 2% on an average. Organic matter supply in soil is one of the major constraints to the agriculture of the country. Yet, the country has been producing good crops and cereal production in 2000 exceeded 27 million ton, with a surplus of 9 million ton. This has been possible only due to the use of high doses of synthetic fertilisers and improved varieties of seeds. Most of the Bangladesh soils show an improved response when OM is incorporated along with inorganic fertilisers. The recommended doses vary between 5 to 10 tons/ha of fresh or partially decomposed cowdung. Use of green manuring plants like Sesbenia rostrate is also encouraged. Use of compost is absent or insignificant.The organic matter status has been classified as: very low (5.5.

Nitrogen statusNitrogen status Because of low level of OM the nitrogen status of Bangladesh soils is substantially low and most crops on all soils respond to nitrogen applications. In fact, nitrogen (N) fertilizers are the most commonly used fertilisers in the country. The country has as many as 6 fertiliser factories producing mostly urea from natural gas. Compared to production with no fertilisers, a 2 to 3 fold increase is common in most crops including rice with N-fertilisers. The N-fertiliser consumption during 1996-97 was more than 2 million metric ton.

Phosphorus statusPhosphorus status The available phosphorus in Bangladesh soils could be considered between low and medium. Most soils respond to P-fertilisation. Phosphorus availability is pH dependent. The source of P supply in soils is inorganic fertiliser. This again is not proportionate to the supply of inorganic N.

Potassium statusPotassium status Bangladesh soils are not deficient in potassium (K) although many soils are found to respond to K-fertilisation. These are particularly non-alluvial soils and the coastal saline soils. About 0.12 meq percent of NH4OAc extractable K is considered the critical limit for Bangladesh.

Sulphur statusSulphur status Response to sulphur (S) application is common in most soils except in coastal saline soils, acid sulphate soils and some acidic soils. Irrigated crops in the northern districts respond markedly to S-application. About four million ha of land is supposed to be S-responsive. Gypsum is the principal source of sulphur.

Zinc and BoronZinc and Boron During the recent past, soils, particularly those under constant waterlogging and irrigation have been found to respond to zinc (Zn) and boron (B) applications. The calcareous floodplain soils are one of them. About 1.7 million ha of land has been estimated to be deficient in Zn supply.

Other micronutrientsOther micronutrients Response to micronutrients other than Zn and B has not yet been reported in any soil for any particular plant. However, it has been suggested that in some peat land soils and other soils, Mn application might have a positive response. It has not yet been confirmed. Crop response to Mo application is also found in some agroecological zone (AEZ).

Cation exchange capacityCation exchange capacity In Bangladesh soils the organic matter content is low and the majority of soils contain 1:1 clays and illites. As such, the CEC of Bangladesh soils in general is not appreciably high. Classification of Bangladesh soils on the basis of CEC (meq%) is: very high (>30); high (15-30); medium (7.5-15.0); low (3.0-7.5); and very low (16.0 dS/m)197320002009197320002009197320002009197320002009197320002009833.451020.751056.26287.37289.76328.43426.43307.20274.2279.75336.58351.6939.9087.14101.92* Source: SRDI, 2012

Comparative Salt affected area between 1973 and 2009 (SRDI, 2012)Salt affected area (000 ha)Salt affected area increased during last 9 years (2000-2009)Salt affected area increased during last 36 years (1973-2009)

197320002009833.451020.751056.2635.51 (3.5%)222.81 (26.7%)

Misuse and abuse of soilsMisuse and abuse of soils It is high time for the planners and policy makers to frame rules/laws to protect arable soils from ruination. Many agricultural lands are brought under urbanisation or industrialisation. One can find numbers of brick kilns set up on fertile agricultural lands along highways. As these lands are private owned, the government has practically no control on their use. Forestlands are also brought under urbanisation and industrialisation. Only about 7% of the total land area is under forest cover now. Overexploitation, ie using the soil for intensive cultivation without replenishing it, is causing nutrient mining to an extent that ultimately will make it barren. Excessive greed, mingled with lack of farsightedness, proper awareness and absence of punitive laws, has aggravated the misuse and abuse of our limited land and this is taking a heavy toll on our soils.

LocationDominant cropping patternTotal yield (t/ha/yr)Nutrient mining (kg/ha/yr)Palima, TangailMustard-Boro-T. Aman13.0-190Polashbari, GaibandhaMustard-Boro-T. Aman10.2-270Narhatta, BograMustard-Boro-T. Aman9.5-280Palima, TangailWheat-Jute-T. Aman7.0-240Paba, RajshahiPotao-Jute-T. Aman34.5-350ThakurgaonSugarcane intercropping60.0-80JoypurhatSugarcane intercropping107.0-60RajshahiSugarcane intercropping90.0-62BograBoro-GM-T. Aman11.0-180BograWheat-GM-T. Aman7.5-170Source: DANIDA/SFFP.

Soil nutrient mining status in Bangladesh (1998-99)

Need for balanced fertilization in Bangladesh agricultureImbalanced fertilizer use is both costly in terms of nutrient loss from soil mining, decline in food supply and loss of soil fertility and land productivity and the consequent decline in food production. Bangladesh adopted a strategy for balanced fertilization to promote soil building to support sustainable land use system and ensure stable supply of food grains from existing agricultural lands.Bangladesh is gradually moving away from the traditional and rather static agriculture dependent on native soil fertility to a dynamic judicious fertilizer dependent agriculture. In a judicious fertilizer-dependent agriculture, balanced fertilization strategy has to be a cornerstone of all activities. Balanced fertilization is aimed at:Increasing crop yields;Increasing crop quality;Increasing farm income;Correction of inherent soil nutrient deficiencies;Improving soil fertility;Avoiding damage to the environment; andRestoring soil fertility and productivity of land that has been degraded by wrong and exploitative activities in the past.

Soil Fertility Management in BangladeshThe crops on a field diminish or increase in exact proportion to the mineral substances conveyed to them in manure (fertilizer).---Justus Von Liebig, 1803-1873Soil testing is needed for accurate and effective fertilization of crops. Soil testing is essentially needed to ascertain actual quantity of soil contents of different plant nutrients already present in the soil. Needed inorganic fertilizer for the crop in right quantity may be computed after adjustment in consideration of the nutrients present in the soil.

Application of recommended fertilizer to the soil will ensure improvement of fertility and productivity status of the soil and the crop under cultivation will have desired yield.Addition of organic manures to the soil improves soil structure, increases water holding capacity of the soil and improves internal condition of the soil. Inorganic fertilizers should be supplemented with organic manures. Judicious crop rotation including a green manuring crop will add appreciable amount of organic matter in the soil. Crops like Dhaincha, mung-bean, mash-kalai, cow-pea may be cultivated as green manuring crops. These crops at flowering stage may be ploughed down and incorporated into the soil.Most important step: Integrated nutrient management (INM) system needs to be adopted.

Thanks Dr Altaf