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Soil Fertility

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.
  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

soil_1.jpg (383×43)

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)
 
 

Indices Range Mean Fertility % Distribution of samples
Organic matter % 0.06-19.63 3.64 L (<2.5) M (2.5-5.0) H(>5.0) 36.1
41.5
22.4
Available nitrogen (kg/ha) 32.5100 270 L(<250) M(250-500) H(>500) 10.3
58.0
31.7
Available phosphorus (kg P2o5/ha) 0.3-315 21.96 L(10) M(10-25) H(>25) 27.5
30.1
42.4
Available potassium (K2O, ppm) 2-750 129 L(<62.5) M(63-150) H(>150) 39.3
30.6
30.1


L, M and H are the low, medium and high category of nutrient availability, respectively.