Soil testing

soil management ......

1. Presentation On Soil Testing . COURSE :- SOIL MANAGEMENT COURSE :- ACP-416 CREDIT HOUR :- 4(1+3) YEAR/SEMESTER :- 4 TH YEAR/ 2 ND SEMESTER Submitted To Dr. T.P. Chandrakar SUBMITTED BY – NANDKISHOR YADAV Bsc (Ag)4 th year SG CARS JAGDALPUR

2. Introduction: Soil testing is an acceptably accurate and rapid soil chemical analysis for assessing available nutrient status for making fertilizer recommendations. The result of a soil test is known as soil test value. A soil test value measures a part of the total nutrient supply in the soil and represents only as an index of nutrient ability.

3. Objectives: Soil test programmes have following objectives: To provide an index of nutrient ability. To predict the probability of profitable response to fertilizer. To provide a basis for fertilizer recommendation. To evaluate the soil fertility status and a county soil area or a statewide basis by the use of the soil test summaries.

4. Phases: Phases of soil testing programme are as follows: Collecting the soil samples. Extraction and determining the available nutrients. Calibrating and interpreting the analytical results. Making the fertilizer recommendation and management.

5. Soil Sampling Sampling is done to obtain a composed soil sample representing a seemingly uniform area or field with similar cropping and management history. Sampling Time Soil samples can be taken any time that soil conditions permit, but sampling directly after fertilization should be avoided. It is important to sample at similar times year after year for comparing analysis at regular time intervals.

6. Sampling depth F or most purposes, soil sampling is done to a depth of about 20cm. In some case , especially in irrigated areas sampling to a depth of 60-100cm is desirable, especially for monitoring nitrate leaching. Depth wise soil samples should be taken where there is a concern about Boron toxicity. Sampling Tools Augers are generally used for soil sampling.

7. A uniform slice should be taken from the surface to the depth of insertion of the tool; the same volume of soil should be obtained in each sub sample. Soil samples for micro nutrient analysis should be taken using stainless steel auger. Drying of Soil samples The soil fresh samples received in the laboratory should be dried in wooden or enameled trays. During drying, the soils are allowed to dry in the air. The trays may be placed in racks in hot air cabinet with a temperature not more than 35 ˚ C.

8. Only air drying is recommended for some of the nutrients present in the sample. Preparation of soil samples After drying, the samples are ground with a wooden pestle and mortar in preparation and clods and large aggregates are crushed and mixed. The purpose of grinding is to reduce heterogeneity and to provide maximum surface area for physical and chemical reactions. After grinding, the soil is screened through a 2mm sieve. To reduce the size of the large sample sub sampling is essential.

9. Sample splitting can be performed with a mechanical sample splitter, such as a Riffle- type Sample Splitter. Quartering can also be done by dividing into four equal portions. If the soil is to be analyzed for trace elements, containers made of copper(Cu), zinc(Zn) and brass must be avoided during grinding and handling.

10. Extraction Different extractants are used to extract the specific nutrients from soil in the laboratory. The ability of an extractant to extract a plant nutrient in quantities related to plant requirements depends on the reactions that control nutrients supply and availability. The extractants commonly used in soil testing programmes are given in the following table: S.No Plant Nutrient Common Extractant 1. Available Nitrogen Alkaline Permanganate 2. Available Phosphorous Sodium bicarbonate (for neutral or alkaline soils), Bray and Kurtz extractant number 1 (for acid soils)

11. S.No Plant Nutrient Common Extractant 3. Available Potassium Ammonium Acetate 4. SO 4 2- CaCl 2 5. Micronutrient cations (Zn, Cu, Mn , Fe) Diethylene pentaacetic acid (DTPA) 6. Boron Hot water 7. Molybdenum Grigg’s Reagent ( ammonium oxalate of pH 3) 8. Organic Carbon Chromic acid

12. I nterpretation For macro nutrients, the result is generally classified into categories of supply e.g : low, medium and high. For these categories, the nutrient amounts required for an optimal or state yield level are estimated. For micronutrients, a critical level is generally used to decide whether an application of that nutrient is needed. Available Nutrient Low Medium High Nitrogen <280 280-560 >560 Phosphorous <10 10-24.6 >24.6 Potassium <108 108-280 >280

13. For nutrients other than N,P,K, a single critical level is usually designated. S.No Nutrient Method/ Extractant Low Medium High 1. N(% organic C) Organic carbon <0.5 0.5-0.75 >0.75 2. N(kg/ha) Alkaline permanganate <280 280-560 >560 3. P 2 O 5 (kg/ha) Sodium Bicarbonate <23 23-56 >56 4. K 2 O (kg/ha) Ammonium acetate <130 130-335 >335 5. S (kg/ha) Heat soluble, CaCl 2 <20 20-40 >40 6. Ca (%of CEC) Ammonium acetate <25 7. Mg (% of CEC) Ammonium acetate <4 8. Zn (µg/g) DTPA <0.6 0.6-1.2 >1.2 9. Mn (µg/g) DTPA <3.0 10. Cu (µg/g) DTPA/Ammonium acetate <0.2 11. Fe (µg/g) DTPA <2.5-4.5

14. S.No Nutrient Method/ extractant Low Medium High 12. Fe (µg/g) Ammonium acetate <2.0 13. B (µg/g) Hot water <0.5 14. Mo (µg/g) Ammonium acetate <0.2

15. Fertilizer Recommendation Fertilizer recommendation refers to the way conclusions are drawn based on soil tests. In our country, following 3 methods are generally used: Fertility group approach Critical level approach Target yield approach Fertility group approach In this method, soil test results and General Recommendation Dose (GRD) are used.

16. On the basis of soil test, soil is categorized into low, medium and high fertility group and fertilizer is recommended as per following table: Critical level approach In this method, soils are divided into two categories on the basis of soil fertility level. This dividing level is known as critical level. This method is used for micronutrient application as it doesn’t determine the quantity of fertilizer to be used but only helps in determining whether or not fertilizer should be used. Fertility level of soil Fertilizer recommendation Low GRD + 50% of GRD Medium GRD High GRD - 50% of GRD

17. Target yield approach Fertilizer prescription for desired crop yields based on available nutrient status is the main concept of this approach For obtaining a given yield, a definite quantity of nutrient must be taken up by plant. Once this is known, fertilizer to be applied can be estimated by taking into account the efficiency of contribution from soil available nutrients and the efficiency of uptake from applied fertilizer nutrients towards total uptake of nutrients.

18. Calculation of basic parameters. Nutrient requirement Percent nutrient contribution from soil to total nutrient uptake(E s ) Percent nutrient contribution from fertilizer to total uptake( E f )  

19. Percent nutrient contribution from FYM to total uptake(E FYM ) Considering the above basic parameters, fertilizer recommendation equations are derived as follows: Where; S= soil test value for available nutrient(kg/ha) Y=Yield Target FYM=Farmyard manure(t/ha)

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