Phosphorus Status in Soils of Eastern Dry Zone, Karnataka, India
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Int.J.Curr.Microbiol.App.Sci (2017) 6(11): 310-324 International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 6 Number 11 (2017) pp. 310-324 Journal homepage: http://www.ijcmas.com Original Research Article https://doi.org/10.20546/ijcmas.2017.611.035 Phosphorus Status in Soils of Eastern Dry Zone, Karnataka, India M. Chandrakala1*, C.A. Srinivasamurthy2, Sanjeev Kumar3, S. Bhaskar4, V.R.R. Parama5 and D.V. Naveen6 1National Bureau of Soil Survey and Land Use Planning, Regional Centre, Hebbal, Bangalore-560 024, Karnataka, India 2Director of Research, Central Agricultural University, Imphal, Manipur, India 3National Dairy Research Institute, Karnal Haryana 132001 4Department of Agronomy, UAS, Bangalore-560 065, Karnataka, India 5Department Soil Science and Agricultural Chemistry, UAS, Bangalore, Karnataka, India 6Deptartment of Soil Science and Agricultural Chemistry, Sericulture College, Chintamani, Karnataka, India *Corresponding author ABSTRACT Phosphorus (P) deficiency is second to nitrogen (N) and its deficiency is widespread. Soil based site specific P recommendation for sustainable crop productivity mainly relies on K e yw or ds status, and availability of phosphorus. Representative soil samples (250) from different Available soil agro-ecological regions of Eastern Dry Zone (EDZ) of Karnataka were analysed for P phosphorus, Eastern status and randomly collected samples were analysed for P fractions. Results revealed that, Dry zone Karnataka, P AvP (Available phosphorus) ranged 12.74 to 94.70; 11.21 to 49.55; 10.70 to 98.32 and Fractions . 10.22 to 64.05 kg ha-1 in Bangalore Rural, Tumkur, Kolar and Chikkaballapura districts, -1 Article Info respectively. Among P fractions, total-P (range: 1218.90-3383.08 mg kg ), organic-P -1 -1 (range: 624.95-3461.85 mg kg ), reductant soluble-P (range: 132.56-364.55 mg kg ), -1 -1 Accepted: occluded-P (range: 7.38-49.69 mg kg ) and Ca-P (range: 6.21-38.76 mg kg ) content 04 September 2017 increased as the P fertility of soil increased and decreasing trend was recorded for Saloid-P Available Online: (range: 38.31-63.23 mg kg-1), Al-P (range: 61.49-164.31 mg kg-1) and Fe-P (range: 35.23- 10 November 2017 109.87 mg kg-1) fractions. Total accoun t of phosphorus is necessary tool for soil based P recommendation under both irrigated and rainfed agriculture. Introduction Phosphorus has been the subject of intensive unavailable forms and with time react further research because of its complex nature. The to become highly insoluble forms. Levels of complexity arises because of three main different pools of soil P have been affected factors. First, the total phosphorus level of not only by soil properties and climatic soil is low. Second, the native phosphorus condition but also by rate and type of P compounds are mostly unavailable for plant applied (Myungsu Park et al., 2006). uptake, some being highly insoluble. Third, when soluble phosphorus sources such as The total P content in agricultural crops those in manures and fertilizers are added to generally ranges from 0.2-0.5 per cent. soil, they are readily transformed into Analysis of 3.65 million soil samples (1997 - 310 Int.J.Curr.Microbiol.App.Sci (2017) 6(11): 310-324 1999) indicates that 42 per cent samples are Collected soil samples were air dried, low, 38 per cent medium and 20 per cent high powdered, passed through 2 mm sieve, stored in phosphorus (Motsara, 2002). There is an in polythene bags and were analyzed for increasing pressure to reduce the application available phosphorus by adopting Jackson, of fertilizers in commercial agriculture and 1973 procedure of Olsen’s extraction method minimize non-point sources of pollution of and Colorimetry for soils pH more than 6.5 both surface and ground waters. There was a and Brays extraction method for soils pH less selective crop response to nutrients in than 6.5. different soils and the responsiveness varied with soil nutrient status (Mulla et al., 1992). Based on the available phosphorus content, soils from EDZ of Karnataka were Continuous application of phosphorus results categorized as Very Low (VL: < 15 kg ha-1), in buildup of this nutrient in the soil. The Low (L: 16-30 kg ha-1), Medium (M: 31-45 buildup of phosphorus depresses the kg ha-1), High (H: 46-60 kg ha-1) and Very availability of Zn and S. However, when high (VH: > 60 kg ha-1) categories. Three nutrient additions are less than the soils from each of these categories were requirement, the crop draws the soil nutrients. selected randomly and analyzed for different With such continuous withdrawals, the native P fractions using standard procedure as given resources diminish with time. Therefore, in 2.1. application of soil based rather than uniform rates of fertilizers is must. Further, Import of Forms of phosphorus DAP increased from 0.6 million tonnes to 2.7 million tonnes during 2007-2008. Thus, to Total phosphorus realize maximum benefits and reduce nutrient losses from fertilizers, they must be applied in The total phosphorus was extracted by the right quantity and source based on initial digesting the soil with nitric acid and soil nutrient status. perchloric acid until a white residue was left. The residue was filtered and made to a known In the light of the above facts, soils of Easter volume. Total phosphorus was then estimated Dry Zone of Karnataka were analysed for by vanado-molybdo phosphoric yellow colour available phosphorus and P fractions with an method (Hesse, 1971) objective is to assess the status of available phosphorus and different phosphorus Organic phosphorus fractions in soils with different fertility levels. Organic phosphorus was determined by Materials and Methods deducting the sum of total inorganic phosphorus from total phosphorus as To know the available phosphorus status, 250 suggested by Mehta et al., (1954). soil samples were collected from 4 Agro- Ecological Systems (AES) of Eastern Dry Available phosphorus Zone of Karnataka (Fig. 1) covering parts of Tumkur, Bangalore (Urban and Rural areas), The available phosphorus was extracted using Chikkaballapura and Kolar districts. Bray’s No.1 extractant for the soils having pH less than 6.5 and Olsen’s extractant for the The details of the sampling areas are soils having pH 6.5 and above. presented in Table 1 along with P status. 311 Int.J.Curr.Microbiol.App.Sci (2017) 6(11): 310-324 The extracted phosphorus was estimated by chloro-stannous reductant. The intensity of chloro-stannous reduced molybdo-phosphoric blue colour developed was measured using blue colour method (Jackson, 1973). spectrophotometer at 660 nm. Forms of inorganic phosphorus Reductant soluble phosphorus (R-P) The method outlined by Peterson and Corey The soil residue from Fe-P estimation was (1966) was followed to fractionate soil washed twice with 25 ml of saturated NaCl inorganic phosphorus. solution by shaking and centrifuging. Soil was then suspended in 15 ml of 0.3 M sodium Saloid bound phosphorus (Saloid P) citrate solution and shaken for 15 minutes with 0.5 g sodium dithionate. The suspension Exactly 0.5 g of soil was taken in to a 50 ml was heated on a water bath at 80 ºC for a few polyethylene centrifuge tube, 25 ml of 1 M minutes. Clear supernatant solution was NH4Cl solution was added and shaken for 30 decanted into a 50 ml volumetric flask after minutes. Saloid-P was estimated by molybdo- centrifugation. Soil was then washed twice sulphuric acid reagent, using stannous with saturated NaCl and the washings chloride as reductant after taking the extract returned to sodium citrate-dithionate extract from supernatant solution after centrifugation which was taken for R-P estimation. Excess in to an aliquot of 10 ml isobutyl alcohol. of citrate and dithionate were oxidised by 1.5 Blue colour intensity was measured at 660 nm ml of 0.25 M KMnO4 solution. The R-P was using spectrophotometer. estimated by molybdate-sulphuric acid reagent with stannous chloride as reductant Aluminium phosphorus (Al-P) after taking the extract into an aliquot of 10 ml isobutyl alcohol. The blue colour intensity The soil residue left after saloid-P estimation developed was diluted with equal quantity of was shaken for one hour with 25 ml of 0.5 M absolute ethyl alcohol and read at 660 nm in NH4F (pH 8.2). The Al-P in the supernatant spectrophotometer. centrifuged suspension was determined by chloro-molybdic-boric acid reagent and Occluded phosphorus (Occl-P) chloro-stannous reductant. The intensity of blue colour developed was read in The soil residue left out in the estimation of spectrophotometer at 660 nm. R-P was added with 25 ml of 0.1 M NaOH and shaken for one hour. Supernatant solution Iron phosphorus (Fe-P) after centrifugation was taken for estimation of Occl-P by chloro-molybdic-boric acid The soil sediment from Al-P estimation was reagent with chloro-stannous reductant. washed twice with 25 ml portion of saturated NaCl solution by shaking and centrifuging. Calcium phosphorus (Ca-P) The soil was then treated with 0.1 M NaOH and shaken for 17 hours and centrifuged. The The soil residue after extraction of occluded supernatant solution was then treated with phosphorus was washed twice with 25 ml of five drops of concentrated sulphuric acid. saturated NaCl solution and washings were Phosphorus free activated carbon was used to discarded. Ca-P was extracted by using 0.25 remove suspended organic matter. The Fe-P M H2SO4 and shaking for one hour and content in the filtrate was determined by centrifuging for five minutes. The phosphorus chloro-molybdic-boric acid reagent and in supernatant solution was estimated by 312 Int.J.Curr.Microbiol.App.Sci (2017) 6(11): 310-324 chloro-molybdic-boric acid reagent with Hasan (1996) reported that the available chloro-stannous reductant.