Department of Sericulture

Soil Testing

Soil is the Nature�s invaluable asset. Nutrient supplying ability of the soil to the plants is termed as �fertility�. Cultivation of plants in a particular area for longer periods depletes the soil of its fertility. Availability of nutrients depends on the physical and chemical properties of the soil. Plants require definite quantity of nutrients based on their age and development status. Therefore the soil which provides the necessary requirement of the plants through its different stages in required quantity is referred to as �fertile soil�. The nutrient requirement of the mulberry plants is given in the Table-1.

Soil testing is conducted to calculate the availability of nutrients to the plants, and to know the physical and chemical properties of the soil. In addition to knowing the fertility of the soil, soil testing also helps in reclamation of the soil and to estimate the correct dose of chemical fertilizers to be applied to the soil.

Mulberry is a deep rooted perennial plant from which 4-6 crops can be harvested depending on the climate and cultural practices. Higher yield of the mulberry leaf naturally depletes the nutrients of the soil proportionally to the greater extent. Therefore, soil of the mulberry garden has to be tested before taking up of the mulberry plantation and for every two years once, to make corrective measures in the cultural practices.

The ideal time for the collection of soil sample is when the silkworm rearing has reached the final stage, when almost all the leaf has been harvested. During rainy season, soon after the irrigation and after burning refuses in the garden, soil sample should not be collected.

Collected soil sample should represent the entire area of the mulberry garden. The location and number of spots of soil sample collection should be based on the extent of the land and variation of soil in the given extent of land.

In the identified spot for soil sample collection, weed, grass, and debris should be removed. Generally for the purpose of soil testing and for recommendation of the fertilizers, the sample of spoil from one foot depth required. In the identified place, a pit of �V� shape of about one foot deep has to be dug. From the sides of the pit about 1 inch soil has to be scraped and collected. Likewise from each pit about 250-500 g of soil sample has to be collected. If the land is hard, 1x1x1 ft cubic pit has to be dug. The soil from the sides of the pit has to be sraped out and collected. Likewise the soil sample has to be collected from 5-6 places. Spade or mumty can be used to scrape the soil sample.

The soil sample from various pits and spread on a cloth or plastic sheet and mixed well. Pebbles, debris, litter etc are discarded. The fine soil is spread in the shape of a disc and divided into four equal parts. Soil of one set of opposite quarters is discarded, The remaining two parts are mixed well and process repeated for 2-3 times Finally the sample is reduced to 500-700 g. Air dry the sample under shade and collect in clean cloth bag of polythene bag with proper label. The following information has to be provided along with the soil sample (Table-1).

Fertility of the soil is directly related to the pH of the soil. If the pH of the soil is less than 6.3, it is referred to as �Acidic soil� and if more than 8.3, �Alkaline soil�. Further, if the soil contains high quantity of soluble salts and has higher electrical conductivity, lower pH and lesser exchangeable sodium, such soils are called �Saline soils�. Generally these kinds of soils are called �problematic soils�. These kinds of soils are not suitable for mulberry cultivation. For mulberry cultivation, the soil that has pH in the range of 6.3 to 7.2 is ideal (Table-4).

Reclamation of the problematic soils.

pH of the soil should be adjusted to normal range by using Lime or Gypsum. If the soil is acidic, lime stone ( Clacium carbonate), dolomite, calcitite or burnt lime should be used and if the soil is alkaline, gypsum is to be used. The quantity of these materials depend on the existing pH of the soil which is known by soil test. Green manure, growing Thyencha in the problematic soil and mulching in it reduces the soil pH. Reclamation of the saline soil is bringing down the soil concentration step by step. Any practice that will reduce the upward movement of water and salt by reducing evaporation or by increasing infiltration will enhance the salt leaching and soil reclamation. Therefore plenty of good quality water for irrigation for flooding and leaching and use of surface mulches are helpful in reclamation of saline soil (Table-2 and Table-3).

Soil testing Institutes:

• Karnataka State Sericulture Research and Development Institute
• Central Sericultural Research and Training Institute, Mysore,
• Agricultural University, Bangalore,
• Department of Agriculture,
• Department of Horticulture,
• Juwari Agricultural Development Laboratory.

Table 1. Format for furnishing information for soil analysis

Table-2. Recommended dosage of chemical fertilizers for irrigated mulberry garden per ha/yr.

Table-3. Fertility rating of the soil with respect to mulberry.

Table-4. Quantity of materials required to reclaim the soil.