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Int.J.Curr.Microbiol.App.Sci (2017) 6(11): 281-294 International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 6 Number 11 (2017) pp. 281-294 Journal homepage: http://www.ijcmas.com Original Research Article https://doi.org/10.20546/ijcmas.2017.611.033 Phosphorus Fractions- Keys to Soil based P Management M. Chandrakala1*, C.A. Srinivasamurthy2, V.R.R. Parama3, S. Bhaskar4, Sanjeev Kumar5 and D.V. Naveen6 1 National Bureau of Soil Survey and Land Use Planning, Regional Centre, Hebbal, Bangalore-560 024, Karnataka, India 2 Director of Research, Central Agricultural University, Imphal, Manipur, India 3 Department Soil Science and Agricultural Chemistry, UAS, Bangalore-560 065, Karnataka, India 4 Department of Agronomy, UAS, Bangalore-560 065, Karnataka, India 5 NDRI, Karnal, India 6 Deptartment of Soil Science and Agricultural Chemistry, Sericulture College, Chintamani, Karnataka, India *Corresponding author ABSTRACT Keywords Fertility gradients, Finger millet – maize cropping system, Graded levels of P, Soil phosphorus fractions. Article Info Accepted: 04 September 2017 Available Online: 10 November 2017 Red soils (Alfisols) of Karnataka are low in total and available phosphorus (P). When soluble P sources are added, undergo transformation into unavailable forms with time. Native P compounds, some being highly insoluble are unavailable for plant uptake. Thus, knowing the changes in P fractions in different soils is much important for P recommendation. The objective of the study was to find out the fate of the applied phosphorus in soils of different P fertility in a finger millet-maize cropping system. An experiment with creation of five P fertility gradient strips (Very low, Low, Medium, High and Very high) in one and the same field followed by response of finger millet and maize crops to graded levels of P was undertaken at UAS, Bangalore. Soil P fractions were determined in a soil after the harvest of maize in a finger millet- maize cropping system. There was an increase in total-P, organic-P, reductant soluble-P, occluded-P and calcium-P fractions with the increased gradient strips from very low to very high applied with levels of P. Whereas, saloid-P, aluminium-P and iron-P are the slowly and plant available labileP forms which were decreased as the P fertility gradients and dose of P addition increased. There was a direct relationship with addition, fixation and distribution of P fractions. Hence, continuous P fertilization can be restricted in soils of high and very high initial P status as the PUE was 20-40 per cent only in general leads to build-up and transformation in to non-labile P forms. Introduction supply phosphorus to the soil solution are important factors affecting P availability. As the basic raw material rock phosphate available in the country is only 10 per cent of the total requirement hence, fertilizer industry The total phosphorus level of soil is not only low but also P compounds are mostly unavailable for plant uptake. The concentrations of phosphorus in the soil solution (intensity) and capacity of the soil to 281 Int.J.Curr.Microbiol.App.Sci (2017) 6(11): 281-294 in India is not self sufficient in meeting the requirement of P therefore, depends on imports for the balance of 90 per cent (Chandrakala, 2014). phosphorus fertility gradients applied with graded levels of P to finger millet- maize cropping system. Materials and Methods Phosphorus (P) dynamics in soil and maintenance of its adequate supply are important for sustainability (Song et al., 2007). The application of P to each crop in a rotation and low recovery of added P has been found to result in its significant build up in soils (Brar et al., 2004). Application of fertilizer phosphorus is essential for raising the available P content in soils in order to meet the crop requirements at different stages of growth. The availability of soil P to plants depends on the replenishment of labile P from other P fractions. Nwoke et al., (2004) observed that the changes in different inorganic-P fractions in soils under a wide range of management conditions. The extent of P depletion ranged from 33 to 129 per cent over a period of 11 years (Nambiar and Ghosh, 1984; Tandon, 1987). The field experiment comprised of two stages. Fertility gradient creation was the preparatory step as per the procedure of Ramamoorthy et al., (1967) followed by finger millet-maize cropping system in the subsequent seasons. Experimental site The experiment was conducted during 20092010 at D-16 Block, Zonal Agricultural Research Station (ZARS), GKVK, UAS, Bengaluru which is located in Eastern Dry Zone of Karnataka at latitude of 12058' N and longitude of 75035' E with an altitude of 930 m above mean sea level. Soil characteristics of experiment site Surface soil (0-15 cm) was analyzed for physical and chemical properties and also determined phosphorus fractions by adopting standard procedures. Soils are reddish brown laterite derived from gneiss under subtropical semiarid climate. The soil of experimental site was red sandy clay loam in texture, acidic in reaction, low in available nitrogen (203.84 kg ha-1) and phosphorus (18.42 kg ha-1) and medium in available potassium (147.12 kg ha-1) content (Table 1). Knowing the initial soil test value and recovery of added phosphates, it will be possible to work out the amount of fertilizer phosphorus needed to build-up the soil phosphate to a given critical limit. Soil based P management relies on maintenance of adequate soil P fertility and replenishment of P nutrient removed by harvested grain. However, there is a need to know the effect of P addition and distribution in soils of different P status for sustained P management and improved PUE in the region. In the light of the above facts, a field experiment was undertaken involving gradient creation followed by response of finger millet (Eleusine coracana L.) - maize (Zea mays L.), are the major crops cultivated in Karnataka among millets and cereals, respectively. Experimental details Creation of fertility gradient strips Five equal strips (45 × 8.2 m2) were created in one and the same field and named very low (VL), low (L), medium (M), high (H) and very high (VH) gradient strips as P0, P1, P2, P3 and P4, respectively. Graded doses of phosphorus viz. 0, 20, 40, 80 and 120 kg ha-1 was applied through fertilizer and organics 50 The objective of the investigation is to assess the availability of phosphorus and their different fractions in soils of different 282 Int.J.Curr.Microbiol.App.Sci (2017) 6(11): 281-294 per cent each so as to achieve Very low (<15 kg P2O5 ha-1), Low (16-30 kg P2O5 ha-1), Medium (31- 45 kg P2O5 ha-1), High (46 - 60 kg P2O5 ha-1) and Very high (> 60 kg P2O5 ha-1) P levels in the respective strips. Exhaustive crop fodder maize (South African tall) was grown provided with recommended doses of nitrogen (100 kg ha-1), phosphorus (50 kg P2O5 ha-1) and potassium (25 kg K2O ha-1) and green fodder was harvested at 60 days after sowing. Soils in each strip analyzed for available nutrients status. Available P2O5 content obtained in P0, P1, P2, P3 and P4, was 14.82, 27.37, 38.76, 52.25, 80.72 kg ha-1, respectively. soil samples were collected at 0-15 cm depth from all the plots separately, which were analyzed for available P and their fractions as per the standard procedures as follows. Total phosphorus was estimated by vanadomolybdo phosphoric yellow colour method (Hesse, 1971). Organic phosphorus was determined by deducting the sum of total inorganic phosphorus from total phosphorus as suggested by Mehta et al., (1954). The available phosphorus was extracted using Bray’s No.1 extractant for the soils having pH less than 6.5 and Olsen’s extractant for the soils having pH 6.5 and above. The extracted phosphorus was estimated by chloro-stannous reduced molybdo-phosphoric blue colour method (Jackson, 1973). Studies on the changes in soil P and different P fractions After harvest of exhaustive crop, each strip was divided in to three replications and further each replication was sub divided in to seven treatment plots of equal size. Finger millet (GPU-28) was grown (spacing: 20 x 10 cm) during summer followed by maize (Nithyashree Hybrid) was grown (spacing: 60 x 30 cm) during kharif 2011 by imposing treatments in a factorial RCBD design. Treatment details as follows; T1: Absolute control; T2 : Package of Practice (NPK+FYM); T3: 100 % Rec. N, P &K only (no FYM); T4: 75 % Rec. P + rec. dose of N&K (no FYM); T5: 75 % Rec. P + Rec. dose of N&K only+ Rec. FYM; T6: 125 % Rec. P + Rec. dose of N&K (no FYM); T7: 125 % Rec. P + Rec. dose of N&K + Rec. FYM. Recommended dose of fertilizer for finger millet was 50- 40- 25 kg N- P2O5- K2O ha-1 whereas for maize 100-50-25 kg N-P2O5-K2O ha-1 was given. Recommended dose of FYM given was 7.5 t ha-1. The method outlined by Peterson and Corey (1966) was followed to fractionate soil inorganic phosphorus. Saloid-P was estimated by molybdo-sulphuric acid reagent, using stannous chloride as reductant. Aluminium phosphorus (Al-P) determined by chloromolybdic-boric acid reagent and chlorostannous reductant using the soil residue left after saloid-P estimation. The soil sediment from Al-P estimation, was then used to determine iron phosphorus (Fe-P) by chloromolybdic-boric acid reagent and chlorostannous reductant. Reductant soluble phosphorus (R-P) estimation was done by taking the soil residue from Fe-P, using molybdate-sulphuric acid reagent with stannous chloride as reductant. The soil residue left out in the estimation of R-P was determined for Occluded phosphorus (Occl-P) by chloro-molybdic-boric acid reagent with chloro-stannous reductant. The soil residue left over after extraction of occluded phosphorus, was used to determine calcium phosphorus (Ca-P) by chloromolybdic-boric acid reagent with chlorostannous reductant. Soil sampling and analysis After the harvest of maize in a finger milletmaize cropping system, The representative 283 Int.J.Curr.Microbiol.App.Sci (2017) 6(11): 281-294 Data presented in Table 2 to 6 depicted changes in phosphorus fractions after harvest of maize in a finger millet-maize cropping system which showed significant differences among mean values of P gradients, treatments and their interaction. fractions were higher in very low and low gradient strips, might be due to acidic soil pH resulting in transformation of added P in to Al-P and Fe-P fractions. Majumdhar et al., (2007) observed that the contribution of OrgP to T-P was 48.90 to 53.70 per cent. They also noticed significant increase in S-P, Al-P, Fe-P and Ca-P but decrease in reductantsoluble and occluded-P fractions. Setia and Sharma (2007) observed that application of P @ 17.50 or 35 kg P ha-1 increased all the forms of P in 22 years of maize-wheat cycles. The relative abundance of P fractions was in the order of saloid-P < Fe-P < Al-P < Ca-P. Jakasaniya and Trivedi (2004) also noticed that the increase in S-P, Al-P, Fe-P and Ca-P fractions with increase in rate of P addition in different soils. Org-P showed a buildup due to sorghum cropping in all soils. Fertility gradients effect Treatments effect There was an increase in, total-P (Table 2), organic-P (Table 3), RS-P (Table 5), occluded-P (Table 6) and Ca-P (Table 6) fractions with the increased fertility gradient strips from very low to very high strip. This might be due to application of P in the increasing dose in order to create fertility gradients. Enrichment of the total and available P (Fig. 1) status as the PUE (Table 8) by the crops was 20-40 per cent only in general. There was a positive correlation exists (Table 7a) between T-P and Org-P, RSP, Occl-P and Ca-P fractions (0.997*, 0.999*, 0.974* and 0.992*, respectively). There were also recorded increased Org-P, RS-P, Occl-P and Ca-P fractions with the increased T-P content of soil. Application of graded levels of P with gradient strips had direct relationship with quantity and distribution of P fractions. The quantity of P fractions was higher as the rate of P application was higher. Application of 125 % rec. P + rec. N&K + rec. FYM to very high gradient strip recorded higher T-P and Org-P followed by nutrients application as per package of practice and 125 % rec. P + rec. N&K. Labile-P forms (S-P, Al-P and Fe-P) were higher when P was added along with manure may be due to lesser fixation of P and chelating action of manures which keeps the P in solution there by reducing the transformation of labile P in to non-labile P forms. Non labile pool was enriched when P was added at higher rate without manure application. Anil kumar (2013) reported that application of manures recorded significantly higher available P over control. Data computation The experimental data were analyzed using ANOVA (One-Way). Critical differences among treatments were estimated at 5 % probability level of significance. Correlation studies were made and the values of correlation coefficient (r) were calculated and tested for their significance (Panse and Sukhatme, 1967). Results and Discussion Unlike T-P, org-P, RS-P, occl-P and Ca-P fractions, S-P (Table 3), Al-P (Table 4) and Fe-P (Table 4) fractions were decreased as the P fertility gradients increased. This may be due to transformation of these fractions in to non-labile forms of P. The Al-P and Fe-P Among the fractions Fe-P, Ca-P and organic P fractions in soil remained unaltered while Saloid-P and Al-P fractions were increased in 284 Int.J.Curr.Microbiol.App.Sci (2017) 6(11): 281-294 comparison to their initial concentration. Sukhvir Kaur (2015) reported that the application of integrated fertilizers recorded significantly higher Sa-P compared to inorganic only. concentration Fig.1 AvP2O5 in soils of different P fertility strips as influenced by graded levels of applied P Table.1 Initial soil properties of experimental site Parameters Coarse sand (%) Fine sand (%) Silt (%) Clay (%) Textural Class CEC [c mol (p+) kg-1] pH (1:2.5) EC (dS m-1) Organic Carbon (%) Available N (kg ha-1) Available P2O5 (kg ha-1) Available K2O (kg ha-1) Exchangeable Ca [c mol (p+) kg-1] Exchangeable Mg [c mol (p+) kg-1] Avail. S (mg kg-1) DTPA-Fe (mg kg-1) DTPA-Mn (mg kg-1) DTPA-Cu (mg kg-1) DTPA-Zn (mg kg-1) B (mg kg-1) Phosphorus fractions Total P (mg kg-1) Saloid–P(mg kg-1) Al-P (mg kg-1) Fe-P (mg kg-1) Reductant soluble-P (mg kg-1) Occluded-P (mg kg-1) Calcium-P (mg kg-1) Organic-P (mg kg-1) 285 Values 33.2 36.3 7.5 23.0 Sandy Clay loam 11.10 5.55 0.26 0.45 203.84 18.4 147.1 6.75 3.60 10.82 55.8 59.5 2.21 2.35 0.54 1115.0 48.70 70.52 135.66 146.85 11.07 10.53 691.67 Int.J.Curr.Microbiol.App.Sci (2017) 6(11): 281-294 Table.2 Changes in total soil phosphorus fraction (Total P) after harvest of maize Total- P(mg kg-1) P levels/Treatments P0 P1 P2 P3 P4 Mean T1 726.33 1086.50 1113.33 1331.67 1517.92 1155.15 T2 1288.67 1543.67 1676.67 1724.67 1810.83 1608.90 T3 1033.33 1220.83 1337.67 1430.42 1563.08 1317.07 T4 959.00 1198.17 1247.75 1436.25 1501.58 1268.55 T5 1121.33 1308.75 1403.75 1538.00 1757.58 1425.88 T6 1075.33 1431.00 1533.67 1694.17 1797.07 1506.25 T7 1381.00 1619.00 1701.33 1890.33 1989.75 1716.28 Mean 1083.57 1343.99 1430.60 1577.93 1705.40 1428.30 F S.Em± CD (p=0.05) P S 37.06 104.58 T S 43.85 123.74 PxT NS - - T1: Absolute control T2: Package of Practice (rec. NPK+FYM) T3: 100 per cent rec. N, P & K (no FYM) T4: 75 per cent rec. P + rec. N&K (no FYM) T5: 75 per cent rec. P + rec. N&K+ rec. FYM T6: 125 per cent rec. P + rec. N&K (no FYM) T7: 125 per cent rec. P + rec. N&K + rec. FYM P0: Very low Phosphorus fertility strip P1: Low Phosphorus fertility strip P2: Medium Phosphorus fertility strip P3: High Phosphorus fertility strip P4: Very high Phosphorus fertility strip 286 CV 11.89 Int.J.Curr.Microbiol.App.Sci (2017) 6(11): 281-294 Table.3 Changes in organic and saloid soil phosphorus fractions (mg kg-1) after harvest of maize Org-P P levels/ S- P Treatments P0 P1 P2 P3 P4 Mean P0 P1 P2 P3 P4 Mean T1 425.91 646.00 674.71 889.70 1066.52 740.57 47.98 53.81 50.73 39.27 36.07 45.57 T2 691.64 924.07 1105.90 1132.47 1197.97 1010.41 84.07 89.25 54.03 44.60 43.67 63.12 T3 418.03 614.30 758.43 864.18 971.38 725.26 64.82 72.49 49.73 40.23 34.00 52.25 T4 415.16 614.73 725.73 921.25 1065.17 748.41 64.14 77.59 48.43 41.09 36.28 53.51 T5 593.89 722.71 879.12 1020.05 1230.28 889.21 70.73 81.77 55.61 52.89 47.96 61.79 T6 466.37 792.52 933.56 1089.97 1160.29 888.54 50.20 66.47 38.95 39.55 37.93 46.62 T7 706.63 969.11 1141.60 1318.74 1417.07 1110.63 85.84 90.52 45.74 42.21 35.73 60.01 Mean 531.09 754.78 888.43 1033.77 1158.38 873.29 66.83 75.99 49.03 42.83 38.81 54.70 CV F S.Em± CD (p=0.05) S 1.92 5.42 S 2.27 6.42 S 5.08 14.35 F S.Em± CD (p=0.05) P S 12.74 35.96 T S 15.08 42.55 PxT S 33.72 95.15 6.68 T1: Absolute control T2: Package of Practice (rec. NPK+FYM) T3: 100 per cent rec. N, P & K (no FYM) T4: 75 per cent rec. P + rec. N&K (no FYM) T5: 75 per cent rec. P + rec. N&K+ rec. FYM T6: 125 per cent rec. P + rec. N&K (no FYM) T7: 125 per cent rec. P + rec. N&K + rec. FYM P0: Very low Phosphorus fertility strip P1: Low Phosphorus fertility strip P2: Medium Phosphorus fertility strip P3: High Phosphorus fertility strip P4: Very high Phosphorus fertility strip 287 CV 16.11 Int.J.Curr.Microbiol.App.Sci (2017) 6(11): 281-294 Table.4 Changes in aluminium phosphorus and iron phosphorus fractions (mg kg-1) of soil after harvest of maize Al- P P levels/ Fe- P Treatments P0 P1 P2 P3 P4 Mean P0 P1 P2 P3 P4 Mean T1 57.55 89.92 77.21 72.45 68.90 73.20 48.06 85.05 79.08 68.45 63.29 68.79 T2 100.96 104.77 86.98 85.27 87.17 93.03 101.07 90.97 84.26 90.65 90.78 91.55 T3 97.66 88.74 75.08 64.67 56.29 76.49 102.92 77.03 67.49 42.21 68.90 71.71 T4 93.78 94.48 72.21 70.67 69.24 80.07 87.24 93.07 61.26 50.38 51.32 68.65 T5 101.41 96.80 82.24 74.73 71.51 85.34 91.27 107.20 77.81 67.00 63.36 81.33 T6 85.52 83.95 65.41 63.45 61.92 72.05 85.18 75.28 69.78 44.87 61.88 67.40 T7 119.85 99.09 77.92 75.88 70.96 88.74 123.00 97.58 60.00 56.52 48.85 77.19 Mean 93.82 93.96 76.72 72.44 69.43 81.28 91.25 89.45 71.38 60.01 64.05 75.23 CV F S.Em± CD (p=0.05) S 3.38 9.52 S 3.99 11.27 S 8.93 25.20 F S.Em± CD (p=0.05) P S 1.72 4.86 T S 2.04 5.75 PxT S 4.56 12.86 9.72 T1: Absolute control T2: Package of Practice (rec. NPK+FYM) T3: 100 per cent rec. N, P & K (no FYM) T4: 75 per cent rec. P + rec. N&K (no FYM) T5: 75 per cent rec. P + rec. N&K+ rec. FYM T6: 125 per cent rec. P + rec. N&K (no FYM) T7: 125 per cent rec. P + rec. N&K + rec. FYM P0: Very low Phosphorus fertility strip P1: Low Phosphorus fertility strip P2: Medium Phosphorus fertility strip P3: High Phosphorus fertility strip P4: Very high Phosphorus fertility strip 288 CV 20.56 Int.J.Curr.Microbiol.App.Sci (2017) 6(11): 281-294 Table.5 Changes in reductant soluble phosphorus fraction (RS-P) of soil after harvest of maize RS- P (mg kg-1) P levels/ Treatments P0 P1 P2 P3 P4 Mean T1 130.18 183.03 196.17 219.13 230.17 191.74 T2 275.10 291.77 297.13 314.17 327.13 301.06 T3 307.13 317.13 326.10 337.20 345.10 326.53 T4 266.17 275.17 287.03 295.23 308.07 286.33 T5 235.20 266.90 268.23 277.10 289.20 267.33 T6 335.23 348.30 353.07 365.07 376.23 355.58 T7 304.03 314.27 323.10 338.13 346.93 325.29 Mean 264.72 285.22 292.98 306.58 317.55 293.41 F S.Em± CD (p=0.05) P S 2.62 7.39 T S 3.10 8.74 PxT S 6.92 19.54 T1: Absolute control T2: Package of Practice (rec. NPK+FYM) T3: 100 per cent rec. N, P & K (no FYM) T4: 75 per cent rec. P + rec. N&K (no FYM) T5: 75 per cent rec. P + rec. N&K+ rec. FYM T6: 125 per cent rec. P + rec. N&K (no FYM) T7: 125 per cent rec. P + rec. N&K + rec. FYM P0: Very low Phosphorus fertility strip P1: Low Phosphorus fertility strip P2: Medium Phosphorus fertility strip P3: High Phosphorus fertility strip P4: Very high Phosphorus fertility strip 289 CV 4.11 Int.J.Curr.Microbiol.App.Sci (2017) 6(11): 281-294 Table.6 Changes in occluded and calcium phosphorus fractions (mg kg-1) of soil after harvest of maize Occluded – P P levels/ Ca- P Treatments P0 P1 P2 P3 P4 Mean P0 P1 P2 P3 P4 Mean T1 11.54 19.92 25.33 29.47 35.82 24.42 5.03 8.77 10.10 13.20 17.17 10.85 T2 20.63 25.67 29.10 35.24 37.93 29.72 15.07 17.17 19.27 22.27 26.23 20.00 T3 25.73 28.64 33.27 50.42 53.26 38.26 17.03 22.50 27.57 31.51 34.17 26.55 T4 20.42 23.90 29.73 32.44 40.89 29.47 12.10 19.23 23.37 24.93 30.55 22.04 T5 18.73 20.30 25.53 29.13 35.06 25.75 10.10 13.07 15.20 17.17 20.27 15.16 T6 29.80 36.28 39.27 54.50 58.21 43.61 23.03 28.21 33.63 36.80 40.60 32.45 T7 21.77 26.17 31.27 32.68 41.03 30.58 20.07 22.27 23.00 26.17 29.17 24.13 Mean 21.23 25.84 30.50 37.70 43.17 31.69 14.63 18.74 21.73 24.58 28.31 21.60 CV F S.Em± CD (p=0.05) S 0.48 1.35 S 0.57 1.60 S 1.27 3.57 F S.Em± CD (p=0.05) P S 0.77 2.16 T S 0.91 2.56 PxT S 2.03 5.72 11.07 T1: Absolute control T2: Package of Practice (rec. NPK+FYM) T3: 100 per cent rec. N, P & K (no FYM) T4: 75 per cent rec. P + rec. N&K (no FYM) T5: 75 per cent rec. P + rec. N&K+ rec. FYM T6: 125 per cent rec. P + rec. N&K (no FYM) T7: 125 per cent rec. P + rec. N&K + rec. FYM P0: Very low Phosphorus fertility strip P1: Low Phosphorus fertility strip P2: Medium Phosphorus fertility strip P3: High Phosphorus fertility strip P4: Very high Phosphorus fertility strip 290 CV 10.16