The Markong Series is tentatively classified as a member of loamy skeletal mixed thermic family of Topic Haplumbrepts.

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1 SOILS OF SIKKIM Detailed studies on the soils of the state and their distribution have not yet been done. A rapid soil survey of low intensity was conducted by the National Bureau of Soil Survey and Land Use Planning, Calcutta Regional Centre, during 1981 has established eight sub-groups and fifteen soil series and are given below: Soil sub-group Soil series Typic Haplumbrepts Markong, Hilley Lithic Haplumbrepts Gompa Typic Dystrochrepts Lingtse, Losep, Namthang Litic Dystrochrepts Machong Umbric Dystrocbrepts Thekabong, Chatrikola, Padamchen. Lithic Udorthents Putuli, Simkara, Nandugaon Aquic udifluents Majitar Ultic Hapludalfs Tariku. Brief Description of Sol Series and their Classification in Sikkim Markong Series (M): It comprises moderately deep, well-drained loamy skeletal soil with dark brown to dark reddish brown colour. They have been developed on mica schists. This soil occurs on strongly sloping (10-15%) hill top with moderate to severe erosion. Soils are under moderately dense forest and pasture land. The Markong Series is tentatively classified as a member of loamy skeletal mixed thermic family of Topic Haplumbrepts. Putuli Series (p): It comprises shallow excessively drained dark brown loamy skeletal soil having some rock particles scattered over the surface. These are developed on micaceous gneissic parent rock of talus deposits. These soils occur on moderately sloping and very steep upper hill slopes. They are moderately to severely eroded and are susceptible to land slides. The Putuli Series is tentatively classified as a member of loamy skeletal mixed thermic of Lithic Udorthents. Lingtse Series (L): It comprises very deep, moderately well-drained fine loamy soils with dark grayish brown to dark brown colour. They have been developed on gneissic parent rock. These soils occur on steep low hill slopes and moderately eroded. The soils are under terraced cultivation. The Lingtse Series is tentatively classified as a member of fine loamy mixed thermic family of Typic Dystrochrepts. Thekabong Series (T): It comprises moderately deep, moderately well drained loamy skeletal soil with dark grayish brown in colour. They have developed on micaceous gneissic

2 parent rock. These soils occur in the steep to very steep middle and lower slopes of hill. Soils are bench terraced for cultivation. The soils are moderately eroded and susceptible to severe erosion. The Thekabong Series is tentatively classified eroded and loamy skeletal mixed thermic family of Umbric Dystrocrepts Machong Series (MA): It comprises moderately deep moderately well-drained, grayish brown fine loamy soils. They have been formed from the underlain micaschists. These soils occur on the moderately steep to steep low hill slopes and piedmont. The soils are under terraced cultivation. Erosion is moderate to severe. The Machong Series is tentatively classified as a member of fine loamy mixed thermic family of Lithic Dystrochrepts. Chatrikhola Series (C): It comprises deed, moderately well-drained fine loamy soils with very dark graysh brown to dark brown colour. They are developed on micaceous gneiss parent rock. These soils occur on steep to very mid slope of low hill slopes and rare moderately to severely eroded. Chatrikhola Series is tentatively classified as a member of fine loamy mixed thermic family of Umbric Dystrochrepts. Gompa Series (G): It comprises shallow excessively drained loamy skeletal soils withn brown to dark brown colour. They have been developed on gneissic parent rock. This soil occurs on moderately sloping and steep to very escarpments. The soils are under severe to very severe erosion and are susceptible to sliding. The Gompa Series is tentatively classified as a member of loamy skeletal mixed thermic family of Lithic Haplumbrepts. Losep Series(LO): It comprises deep, moderately well-drained, loamy skeletal soils with grayish brown to yellowish brown colour. They have been developed on colluvial materiala over gneissic parent rock. These soils occur on steep lower slopes of hills and are moderately to severely eroded. The Losep Series is tentatively classified as a member of loamy skeletal mixed thermic family of Typic Dystrochrepts. Namthang Series: It comprises deep, well-drained, loamy skeletal soils with brown to dark yellowish brown colour developed from phyllite parent rock occurring on moderately sloping to strongly sloping mid hill slopes and are moderately eroded. Soils are under paddy cultivation. It is tentatively classified as a member of loamy skeletal mixed thermic family of Typic Dyestrocrepts. Simikara Series: It comprises moderately deep excessively drained coarse loamy, fragmental soils with yellowish brown to light olive brown colour and developed on micaschist parent rock. This soil occurs on very steep escarpment slope and is severely eroded. Soils are under dense forest.

3 Nandugaon Series: It comprises well-drained coarse loamy, fragmental soils with brown to dark brown colour, developed from sandstone parent rock, The soil occurs on steeply sloping mid and upper part of hills are severely eroded. Soils are under crop cultivation (Maize). It is tentatively classified as a member of coarse loamy fragmental, mixed thermic family of Lithic Udorthents. Hilly Series: It comprises vary deep moderately well-drained fine loamy soils with dark reddish brown to reddish brown colour developed on gneissic parent material. The soil occurs on steeply sloping upper hill slope and is moderately eroded. Soils are under crop cultivation. It is tentatively classified as a member of fine loamy mixed thermic family of Typic Haplumbrepts. Padamchen Series: It comprises moderately deep, moderately well-drained, fine loamy soils with brown to yellowish brown colour and developed from gneissic parent material. This soil occurs on moderately steep to upper hill slope with severe erosion under thin forest vegetation. It is tentatively classified as a member of fine loamy mixed thermic family of Umbric Dystrochrepts. Taraku Series: It comprises very deep, moderately well-drained fine loamy soils with brown to dark colour developed on sand stones. Soils occur on moderately steep to steep upper and mid-hill slopes and are moderately eroded. Soils are under horticultural crops. It is tentatively classified as a member of fine loamy mixed thermic family of Ultic Hapludalfs. Majitar Series: It comprises deep, well-drained loamy soils with grayish brown to light gray colour. They are of alluvial and collurial origin. This soil occurs on gently sloping to moderately sloping uplifted river terraces and is susceptible for river bank erosion and flooding. Soils are under horticultural crops. It is tentatively classified as a member of coarse loamy, mixed, thermic Aquic Udifluvent. Explanation of the Symbol Soil series Slope Class Markong - M Moderately sloping 5-10% D Gompa - G Moderately steep to 15-25% G steep Putuli - P Lingtse - L Very steep slopes 33-50% H Tekabong - T Very very steep slopes over 1Slope 50% Machong - MA Chatrikhola - C Losep - LO

4 Fertility Status: Soil reaction Organic matter content Available N Available phosphorous Available potash Lime requirement acidic, about 50% having ph 5.0 or below, about 45% having ph 5.0 to 6.0 and rest ph 6.0 or above. high mostly, between 2 to 5% but low up to 15 high up to 10% are also available. about 60% low, 30% medium and 10% high. about 30% low, 35% medium and 25% high. about 20% low, 35% medium and 45% high. mostly between 5.0 tonnes per hectares but varies from 0 to 40 tonnes per hectares. Water holding capacity of the soils is medium. Soil generally fall in hydrological group B AGRICULTURE SOIL FERTILITY MANAGEMENT IN SIKKIM The soil management is the primary function of sustainable land use to satisfy the human needs in such a way that the subsystems of land environment are put to most beneficial uses consistent with their inherent potentialities, while at the same time preserving its qualities for future use. Soil is directly related to the health of individuals and therefore to the health of nation. In fact in agriculture soil in agriculture soil and water must be considered together if basic resources of land and water are neglected it is bound to have serious economical, social and political repercussions on the community and nation. Although, the need of good soil fertility status for increase production was realized long ago and local method like organic manure application and use of plant residues as much etc. were developed by the ferment. The use of inorganic fertilizer has received attention only in the last 4 decades. The complexity and magnitude of soil fertility research have assumed much greater dimensions these days due to rapid change from subsistence agriculture to adoption of multiple and intensive cropping for augmenting crop production as a result of introduction of high yielding, short duration, an photo insensitive varieties of important crops. This is causing faster and greater depletion of soil fertility. Severe depletion is soil fertility is bound to occur if suitable steps are not taken simultaneously to restore it through application of balanced organic fertilizer in conjunction with organic manure. General Description The trend of mountain system is in general east-west direction, however chief ridges run in a more or less North South direction. The of Sikkim broadly grouped into 5 physiographic Zones based on geomorphology are give in (Table) with their characteristics. The steeply sloping side slope (>52%) cover an area of 43 per cent and soil erosion is the major cause of land degradation and often subjected to land slide or land slip. The National Bureau of Soil Survey and Land Use planning (NBSSLUP), regional centre, Calcutta surveyed the soil

5 of Sikkim and classified the soil in to 3 texonomic orders of Inceptisol (33.4%), Entisols (43%) and Mollisols (23 6%) and 12 great subgroups on the basis of nature and properties of soil (Anonymous 1992). The depth of soil at different places varies considerably because of differences in physiographic position and slope. The fertility of soil also depends much on the geological formation of the rocks. Table 1. physiographic classification of Sikkim soils (Anonymous 1992) Physiographic 1 soils on summit and Ridge Top Steep sloping Moderate steep sloping Moderately sloping 2 Soils of side slope of Hills very sleepy Zone/sub zones % slope >30 <30 <15 >50 Soil depth % Deep Deep to moderate Deep geographical area Land Use Forest (D) paddy and maize Temperate Forest (D) cereals Paddy (D) temperate forest Constraints APE. CT. SA E. SD. SSt E. SSt Thermic soil temperature regime Isomesic soil temperature regime Escarpments (Thermic soil temperature regime) Steeply sloping side hill Thermic soil temperature regime Isomesic soil temperature regime Cryic soil temperature <50 Very steep Moderate deep to deep moderately shallow to Moderately deep Moderately deep to deep Moderately shallow to deep Shallow to Moderately deep Shallow to moderately shallow shallow Temperate forest and maize Conifers and junipers (D) cereals in patches Temperate Forest (D) maize Paddy and maize (D) temperate forest conifers and Alpine pasture (D) careal in patches A.E.St A. SD. St. E E.A A.E. st SD, E. St

6 regime moderately steep sloping side hill Alpine pasture SD. St Thermic soil temperatue regime 3 Soils on Valley Moderately steep sloping valley Thermic soil temperature regime Isomesic soil temperature regime 4 Soils on Cliff and precipitous slope Thermic soil Temperature regime Isomesic soil temperature regime 5 Soil on Glacial Drift Moraines and Boulders Isomesic soil temperature regime Moderately deep to deep Moderately deep to deep Moderately shallow to moderately deep Shallow Extremely shallow Moraines and boulders Paddy, mazie, ginger, fruits tropical and temperate Forest careal Cereals patato temperate fruit forest Permanent fallow Barren land E.A E. st A. St. E. SD. E SD.E 3.59 Forest SD. St. E Soil Fertility Great importance is attached to characterizing the soil s nutrient supply available to plants. and to soil analysis in particular. The necessity for soil analysis for detecting the soil s nutrient reserves proved by the scientific findings all over the world. The precise knowledge of the nutrient content of the soils to allow fertilizers to be used in rational way as precondition for maintaining and improving soil fertility. Site specific nutrient management depends on a sound inventory of soil nutrient availability. It is most useful when used to. 1. To evaluate the fertility status of a given field in respect of N, P, K, organic matter ant to degree acidity.

7 2. To predict the probability of obtaining a profitable response to lime and fertilizers ant the amount to apply. 3. To evaluate the fertility status of soils on village, soil area or state wide basis by use of so test summaries. 4. Formalization of quantitative information for soil fertility maps. 5. Data in regard to change in soil fertility due to regular of mineral and organic manure as well as chemical amendments. 6. Increase knowledge of how various farming practices and crop rotation affect test trend over time and across large area.. 7. Continue to add information each year and begin more detail analysis of the records to refine the specific nutrient management plan Based on the soil test done by the Sikkim State Soil Testing Laboratory, fertility status of soils are prepared following the standard ratings (Muhreatal.1965) into low, medium and high soil fertility classes in respect of each nutrient. The nutrient indices was calculated by using the formula The values less than 1.5 are considered low, 1.5 to 2.5 medium and more than 2.5 high. A summary of mean values, ranges, percent distribution of soil samples in respect of organic matter, available nitrogen, phosphorus and potassium are given in (Table 2). The organic matter content of soil is quite high and in majority of soils, its value lies between 2 and 5 per cent. From the observation k it can be expected that in 70, 58 and 70 per cent soils, the response of crops to fertilizers N P and K could be expected from moderate to high levels. Soil fertility information has been published in the form of a bulletin (Bhutia et al. 1985), which gives the individual far met the fertility status of each of his fields and summary of soil testing data to the state, district or village level workers centers for developing suitable fertilizer use strategy. The analysis of micro nutrients indicate the low availability of molybdenum and boron and sufficient in Zu, cu, Mn an Fe (Awsthe & Awasthe 1995) Table 2. Mean, range and per cent distribution of soil samples indifferent fertility classes (Bhutia et al. 1985) Organic matter % Indices Range Mean Fertility Available nitrogen (kg/ha) Available phosphorus (kg P2o5/ha) L (<2.5) M ( ) H(>5.0) L(<250) M( ) H(>500) L(10) M(10-25) H(>25) Available potassium (K2O, L(<62.5) M(63-150) 39.3 % Distribution of samples

8 ppm) H(>150) L, M and H are the low, medium and high category of nutrient availability, respectively. General soil fertility constraints for crop productivity Before one century in Sikkim with low population density, the equilibrium between natural resources of hills and soil degradation was least and allowed the sustainable agriculture albeit as relatively lower productivity levels. At present high demographic pressure has resulted wide spread expansion of steep land agriculture. These are the soils most at risks from degradation, partly because of their inherent limitations. The following are the main soil productivity constraints. 1. Steep sloppy land leading to high soil erosion and thus loss of soil fertility resulting in low yield. 2. High soil acidity and associate problems. 3. Light texture of soil leaching losses of nutrients through water under high rainfall conditions. 4. High phosphorus fixation capacity of soil. 5. Release of soil nitrogen is low acidic soil and cold temperature. 6. Low efficiency of fertilizer utilization due to smaller size of land holding and rugged hilly terrain 7. Slow rate of transfer of modern technology coupled with lack of awareness and realization of technology Maintenance of soil fertility Two things are necessary to restore soil fertility; to remove the source of degradation and treat the symptoms of degradation.soil erosion represents the most complete form of land degradation the removal of soil resource itself- and eroded sediment deposited on adjacent lands and drainage way lead to further degradation. A healthy soil has important chemical and biological attributes including nutrient supply, acid and base buffer capacity, and organic matter decomposition. Pathogen destruction, toxic metal inactivation and toxic organic inactivation and without degradation. Soil fertility remains at an optimum level if regular doses of manure, fertilizer and amendments are added to it. It ensures better crop yield, besides maintaining the soil fertility. In the proceeding paragraphs only the methods of soil fertility maintenance will be briefed because soil erosion and other aspect of soil degradation are being given by other authors. In this the proceeding paragraphs only the methods of soil fertility restoration will be briefed.

9 Soil acidity and liming Natural variation of climatic conditions and wide range of parent materials involved in the soil formation of Sikkim, have resulted acidic soils of diverse nature. Among the four districts of Sikkim, the frequency of soil samples having ph less than 5 are 50 per cent in North Sikkim and in other districts is below 12 per cent (Bhutia et al 1985). On such type of soils, the growth of plants is restricted and low yield of crops can be attributed to Al and Mn toxicities, and deficiencies or imbalance s among the nutrient base cations. Exchangeable Al occupies the considerable portion of the soil exchange complex, where ph drops below 5 and liming of such soils are needed to improve the productive of soils. The liming of acid is important to provide acceptable plant-root environment on soils containing high levels of toxic aluminum. The field experiments conducted on acidic soils of Sikkim to maize, wheat and soybean, the highest yield were obtained when dolomite limestone rates were equivalent of exchangeable Al an soil Ph was around 5.5 (patiram et al.1991). Therefore, a ready reckoner for quick appraisal of lime requirement for the acidic soils of Sikkim is suggested to raise the ph 5.5 (Patiram 1991). The rate of limestone added in the acid soil based on exchangeable Al to raise the ph 5.5 was sufficient for 2 yeas to wheat and maize crops in a sequence, thereafter half amount to limestone is necessary for sustained crop productivity (patiram et al. 1990). Further field trials indicate that furrow applications of small does of limestone (250 kg/ha) every year to maize and soybean is economical than a relatively higher dose based on exchangeable Al. The poor and marginal farmers with resource constraints can invest on 250 kg limestone/ha in furrows every year to achieve the optimum crop productivity. Organic manuring Sikkim farmers are much more conscious about the use of manure than those in other parts of the country. Organic matter in one form or other has long been used to rejuvenate soil fertility. To the maximum extent their farming systems rely upon crop rotation, crop residues, animal manures, and legumes is used mainly for ginger and vegetable cultivation, other crops get least organic manures, Organic manure is often used to reduced the need of fertilizer inputs, by usually locally available alternative. Organic manures have the profound influence on soil physical, chemical and biological properties affecting its capacity to hold as well as release of nutrients. It forms the complex with Al and Mn, thereby decreases their toxic Bulky manure can counteract the Unfavorable impact of climate vagaries o sudden stress conditions on crop yield and deficiencies. The benefit of fertilizer can be increased by the continuous application of FYM to each crop on Al toxic, which is a almost a common practice in Sikkim. However higher yields of crops can be achieved by the application of one tonne limestone with FYM by increasing base status and surface of soil where it is possible

10 Maintenance of soil fertility Soil fertility remains at an optimum level if regular doses of organic manures and fertilizers added to it. To enhance the nutrient availability, soil ph should be adjusted around 5.5 by liming at the same time. An increase in rainfall favors plant growth at higher altitude and decrease of temperature slows the decomposition of organic matter. The analysis of higher altitude soils for organic matter may not give the true value of available N as such; there is a need to have a fresh look at the limit fixed for organic matter to Indian soils. The acidic reaction of soils and cooler soil temperature at higher elevations retards the mineralization of organic p, which in turn minimizes the available p supplying power of soil for achieving optimum productivity of crops. Bio-fertilizers as a source of supplying plant nutrients through various biological reactions on soils/plant and also improve the soil fertility. The important biofertilizers; (a) Rhizobium for leguminous crops, (b) Azotobacter/Azoperillium for non-legume, (c) blue green algae (BGA) and Azolla for irrigated rice and (d) phosphorus bacterium for solubilizing the native p have the large potential for supplementing chemical fertilizers along with organic manure for intensive farming. Agro-forestry for soil productivity Appropriate agro forestry system have the potential to control soil erosion, maintain soil organic matter and physical properties, augment N fixation, and promote efficient nutrient recycling the suitable agro forestry system available from local s experiences would heck the soil degradation and increases the ability of soil plant system to transform efficiently into biomass and the inputs provided.

11 Soil Map of Sikkim

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