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Int.J.Curr.Microbiol.App.Sci (2019) 8(10): 1102-1112 International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 8 Number 10 (2019) Journal homepage: http://www.ijcmas.com Original Research Article https://doi.org/10.20546/ijcmas.2019.810.129 Comparison of Reduced P Application and Supplemental Enhancement of Nitrogen (N) and Zinc (Zn) on their Availability and Yield of Rice (Oryza sativa L.) Crop in High- P Soil Maishnam Anand Singh1*, P. Surendra Babu2 and M. Chandini Patnaik2 1 Department of Soil Science, College of Agriculture, PJTSAU, Rajendranagar, Hyderabad-500030, India 2 AICRP on Micro & Secondary Nutrients and Pollutant Elements in Soil and Plants); A.R.I, Rajendranagar, Hyderabad- 500 030, India *Corresponding author ABSTRACT Keywords High P soil, Phosphorus fixation, RDF, RDP, P- fertility Regime, Yield, Paddy Article Info Accepted: 10 September 2019 Available Online: 10 October 2019 The present investigation entitled “Comparison of Reduced P Application and Supplemental Enhancement of Nitrogen (N) and Zinc (Zn) on their Availability and Yield of Rice Crop (Oryza sativa L.) in High-P Soil” was carried out at AICRP on Micronutrients, Hyderabad Centre, ANGRAU to (i) determine the availability of nitrogen and zinc under different P regimes of the same soil, (ii) to determine whether reducing the P application or supplementing additional nutrients is a better choice in high- P soil in terms of yield of paddy crop. A laboratory experiment was conducted after developing low (16), medium (40), high (63), v. high (102) and v.v high (128 kg P 2O5 ha-1) soil- P fertility regimes of a low P soil using its P- fixation characteristic curve and by employing 3 levels each of N and Zn to determine the availability of these nutrients under different P- fertility regimes. Net house experiment was conducted employing a high- P soil (89 kg P2O5 ha-1) using paddy as test crop with two (2) treatments comprising different individual supplementation doses and their combination of N and Zn in combination of two levels of P application (100 % and 70 % RDP). Different P–fertility regimes were made using P- fixation characteristic curve. Under laboratory condition, the availability of N and Zn increased with increasing levels of their applications, irrespective of soil P fertility regimes in 45 days of contact period. Likewise, the availability of N increased with the increase in contact period from 15 to 45 days. However, in case of zinc the availability decreased as the contact period in the soil increased from 15 to 30 days and there after increased by 45th day of incubation. Under laboratory condition the nitrogen availability increased from 219 to 314 kg N ha-1 in the same soil as the P- fertility regime shifted from low to v.v high thereby registering a 43 per cent enhancement. The available DTPA- Zn extraction decreased by 22 per cent (from 3.28 to 2.55 mg kg-1) as the available soil P increased from 16 kg (low P-regime) to 128 kg P2O5 ha-1 (v.v high P-regime) of the same soil. The Net house experiment results revealed that additional application of nutrients like N and Zn and their combination beyond their current recommended levels enhanced the yield of paddy in a high P soil. Reduced level of P application (i.e. supply of 70% RDP only) to paddy crop decreased its grain yield over supplemental nutrients’ treatments in this high-P soil experiment when compared to that of full supply of 100% recommended dose of P indicating that additional supply of N augment the yield of paddy crop in a high-P soil but not when the P supply is reduced on such soil. The choice between reducing the Pfertilizer in a high- P soil without affecting the yield and realization of enhanced yield with addition of supplemental doses of nutrients will depend upon whether the reduction in input cost is priority or improving the productivity with little more expenditure. 1102 Int.J.Curr.Microbiol.App.Sci (2019) 8(10): 1102-1112 Introduction The importance of phosphorus in crop production, their behavior in soil and its interrelation with other nutrients in soils and plants is well documented. The use efficiency of applied P fertilizer seldom exceeds 20 to 25 per cent and most of the applied phosphorus is fixed. The continuous use of P fertilizer in the crop production results in gradual enhancement in its availability over years (Nambiar, 1994). The general perception of Indian soils’ available P being low to medium status has changed over years due to continuous, increased and discriminate use of P fertilizers. The recent soil fertility mapping undertaken by Department of Agriculture and Co-operation through IISS, Bhopal indicated such paradigm shift in the available P status of Indian soils. Recent studies of AICRP on Soil Test Crop Response (STCR), Hyderabad center revealed that 67 % of 5736 soil samples analyzed from 10 districts of Andhra Pradesh were found to be high in available phosphorus status (Reddy et al., 2013). The occurrence of P accumulated soils or high- P soils offer the following opportunities/ constrains in crop production. Possible saving of P fertilizer from current recommended doses without affecting the yields of crops Ability of such soils to provide current yield levels of yield with continued application of reduced amount of P Interference in availability (reduction/ enhancement) of other nutrients availability in soils. Therefore, it is essential to understand the consequences of occurrence of P accumulated soils in terms of extent of saving of P fertilizer, duration upto which P fertilizer can be reduced on such soils, the kind of nutrient interactions and possible environmental pollution (Eutrophication). A decade long experiment conducted by Radio Tracer Laboratory (RTL), ANGRAU revealed that the P application can be reduced to an extent of 25 to 50 per cent from the current recommended dose of fertilizer in high- P soils without affecting the yields of crops like rice, maize and sunflower (Annual Report of RTL, 2008- 2010). The interrelationship of P with other nutrients for their availability in soils and uptake was studied for several crops in the past but not in high- P soils. The Liebig’s law of minimum indicated that the yield of crops is limited by most limiting factor (nutrient). However, it is not known that which element/ nutrient would be limiting if P accumulation increases in soil. With this background, an initial attempt in the form of the current research aspect entitled “Comparison of Reduced P Application and Supplemental Enhancement of Nitrogen (N) and Zinc (Zn) on their Availability and Yield of Rice Crop (Oryza sativa L.) in High-P Soil was undertaken. Materials and Methods Different experiments are carried out and materials and methods employed to achieve the objective of this investigation.1) Development of different P- fertility regimes of the selected Soil. 2) Availability of Nitrogen and zinc in a soil with different Pfertility regimes and contact periods. 3) Effect of different supplemental doses of N and Zn on yield of rice crop in a high P soil. Twenty five soil samples from different fields of College Farm, ANGRAU, Hyderabad and Directorate of Rice Research, Hyderabad were collected and analyzed for available P2O5. One soil having low available P2O5 (< 23 kg P2O5 ha-1) (Muhr et al., 1965) was selected to employ in incubation study of experiment no: 2. The bulk soil sample collected from different spot of selected field was processed and final available P2O5 was once again determined to ascertain the low status of 1103 Int.J.Curr.Microbiol.App.Sci (2019) 8(10): 1102-1112 available P2O5 to be employed in the incubation study. The physico- chemical characteristics of the soil was analyzed following standard procedures (Tandon, 1993; Linsay et al., 1978) and given in table 1. From the P- fixation characteristic curve, it was found that there is a need to determine precise value of P-fixation to develop different Pfertility regimes of same soil. The classification of low, medium and high categories was based on Muhr et al., (1963). The v. high and v.v high regimes were arbitrarily fixed as there is no such soil classification available in the literature in order to mimic the v. high status of Paccumulated soil. Therefore, P – fixation characteristics of the soil was once again determined by employing P solution in the range of 10 to 50 ppm P solution with narrow intervals of 5 ppm. The quantities of P to be added to arrive at different P- fertility regimes were found from the final graph (Fig. 1 and 2). Accordingly, different P- fertility regimes of medium (23- 56 kg P2O5 ha-1), High (56- 80 kg P2O5 ha-1), Very. High (80- 110 kg P2O5 ha1 ) and Very. Very High (>110 kg P2O5 ha-1) were made (Table 3). No P- solution was added to the original soil and is taken as such to designate it as low P- regime soil. The above treated soils were saturated with water, stirred well and left it for drying in laboratory at 70 0C in an oven. The soil thus obtained was grounded and analyzed for final available P2O5 to employ in incubation studies. Different treatments were employed in the incubation studies. Hundred grams of each of five P- fertility regime soils was taken in thirty plastic bottles. Different solutions of treatments (i.e. 3 levels of nutrients x 2 replication x 5 P- fertility regimes) were introduced into this soil as per the necessity. Samples were drawn from each set after 15, 30 and 45 days of contact period from same plastic bottles containing soil and analyzed for required nutrients. Treatments and replications were made so as to draw the samples for analysis after 15, 30 and 45 days of contact. Throughout the incubation periods the soil moisture was maintained at field capacity based on weight loss at an interval of 5 days. The details of the treatments are given below: Levels of P fertility : 5 Nutrient Studied : 2 (N and Zn) P- Fertility regimes : 5: low (< 23 kg P2O5 ha-1), medium (23- 56 kg P2O5 ha-1), high (56- 80 kg P2O5 ha-1), v. high (80- 110 kg P2O5 ha-1), v.v high (> 110 kg P2O5 ha-1) Levels of Nutrient studied : N: 100, 125 and 150 % RDZn: 25, 50 and 100 % RDZn No. of P- levels : 2 (100 % RDP and 70 % RDP) No. of contact periods : 3 (15, 30 and 45 days) Replications : 2 Design of experiment : CRD The details of 100 % RDF and 25 % recommended doses of supplemental nutrients are given below: 100 % RDF : kg P2O5 + 40 kg K2O 25 % Excess N : 25 % Zn : (i.e. ¼ of 25 kg ZnSO4/ha rice crop) 120 kg N + 60 30 kg N 6 kg of ZnSO4 recommended for At the end of each contact period, samples were drawn from the treated soil of each set to analyze N and Zn following standards methods. A pot culture experiment was conducted in net house at ARI, Rajendranagar, Hyderabad during kharif 2013 to study the effect of different supplemental doses of nutrients (N and Zn) on yield of Rice crop in a High P soil under varying levels of P application. One soil having high P availability was selected from twenty five soil samples collected and analyzed. The physiochemical properties of the soil are given in table 2. The potting of soil was done taking six 1104 Int.J.Curr.Microbiol.App.Sci (2019) 8(10): 1102-1112 (6) kilograms of each of selected bulk and the processed soil was filled in a plastic buckets with a hole made at the bottom. The following treatments were imposed in this experiment (Table 1). No. of supplemental Nutrients: 9 Levels of P : 2 (100 % RDP & 70 % RDP) Total Treatments : 3X2=6 Replication : 3 Total no. of Pots : 3 x 2 x 3 = 18 Design of experiment : CRD RDF of crop : 120: 60: 40 (N: P2O5: K2O kg ha-1) RD Zn of crop : 25 kg ZnSO4 ha-1/ crop. Results and Discussion The results obtained in this investigation are presented below followed by discussion. The P- fixation characteristic curve obtained following the standard procedure of Ghosh et al., (1983) is given in Figure 1. It was noticed from the figure that the actual P- fixation was not very sharp as the concentration employed became very wide at higher levels. Therefore, from the graph a range of 10 to 50 ppm P solution were once again employed with small intervals @ of 5 ppm each to obtain the inflexion point from where P- fixation became constant. The P- fixation characteristics of the soil employed with the desire concentration is given in Figure 2. From the graph it was clear that the P- fixation capacity of the low P- soil selected for developing different P- regimes was 72 %.The P- fixation as well as the P- extraction curves was used to determine the approximate levels of P- availability status of the soil with the known addition of the soil duly allowing for the P- fixation. The following are the different levels of concentration of P- added (Table 3) and the P- availability of such soil after three (3) cycles of alternate wetting and drying under laboratory condition. This soil of different P-fertility regimes developed @ 3 kg for each regime was employed in the incubation study. Availability of Nitrogen under varying Pfertility regimes with varying contact periods Effect of P-fertility regimes The availability of Nitrogen increased significantly from 219 to 311 kg N/ha as the P-fertility of the same soil increased from low (< 23 kg P2O5 ha-1) to very high level (>110 kg P2O5/ha) over N and incubation period levels. Effect of varying levels of Nitrogen The available nitrogen increased significantly from 223 to 299 kg as the added N to soil was increased from 100% RDN to 150% RDN. Effect of Contact period The available nitrogen in the soil increased significantly as the contact period of added nitrogen increased from 15 to 45 days over Pfertility regimes and levels of N. Interaction of P- fertility x Nutrient levels The interaction effect of P Fertility x Nutrient levels on extracted available N in the soil was significant. At any given level of added N (100 or 125 or 150% RDN), the highest available nitrogen was found to be in the soil with highest P-fertility regime. Interaction of P-fertility x Contact period Data in table 4 indicated that highest N availability was noticed at 45 days of contact 1105 Int.J.Curr.Microbiol.App.Sci (2019) 8(10): 1102-1112 periods in the soil with highest P-fertility regime. Interaction of N levels x contact period from 15 to 30 days. However, the DTPA zinc increased significantly and reduced to original status (2.96 mg/kg) by the time the contact period increased to 45 days. The nitrogen availability in soil was significantly affected by the interaction of N levels x Contact period. Application of 150% RDN to soil after 45 days of contact period resulted in highest Nitrogen estimation over P fertility regimes. Interaction of P-fertility x Zinc levels Interaction of P- fertility x N levels x Contact period It was also found to be non-significant. Interaction effect of P-fertility x Zinc levels was found to be non-significant. Interaction of P-fertility x Contact period Interaction of P-fertility x Zinc levels x Contact period It was found to be non-significant. Availability of Zinc under different Pfertility regimes with varying contact periods Effect of P-fertility regimes The DTPA extractable zinc decreased significantly with increasing phosphorus fertility level. The decreasing was noticed from low phosphorus to high phosphorus level (3.28 to 2.66 mg/kg). Subsequent enhancement in phosphorus fertility resulted in statistically similar zinc extractability in the range of 2.55 to 2.68 mg/kg. Effect of varying level of Zinc Applicability of the increasing levels of Zinc from 25 to 100% RD Zn significantly increased the DTPA Zn extraction from 2.57 to 3.07 mg/kg (over P-fertility and Contact period) as given in Table 5. Effect of Contact period The DTPA extractable Zinc decreased significantly from 2.87 (mean of 2.6, 2.9 and 3.12) to 2.66 mg/kg with increasing contact It was also found to be non-significant. Effect of different supplemental doses of nutrients and P levels on paddy grain and straw yield in a high P soil These result as indicated in Table 6 shown that supplemental enhancement of Nitrogen (T2) recorded highest paddy grain yield and straw yield of 13.0 gm pot-1 and 15.9 gm pot-1 respectively. The application of RDF-NK + 25% RD Zinc (T3) recorded paddy grain yield and straw yield of 12.7 gm pot-1 and 15.6 gm pot-1 respectively whereas amongst the three (3) treatments the application of 100% RDF of NK (T1) had shown less paddy grain yield and straw yield of 12.1 gm pot-1 and 14.6 gm pot-1. On the other hand, reduced application of P (i, e 70 % RDP) significantly reduced the paddy grain yield over different treatments as compared to the recommended dose of P (i.e. 100% RDP). These result indicated that in a high P soil, there is a possibilities to improve the yield of paddy crop by additionally supplying of N in excess of the recommended dose. 1106 Int.J.Curr.Microbiol.App.Sci (2019) 8(10): 1102-1112 Table.1 Different treatments employed in the experiment S.No Set-I Set-II With 100 % RDP With ST based Phosphorus (70 % RDP) 1 Only RDF of NPK (100 % RDP) RD-NK + STBP ( i.e 70% RDP) 2 RDF-NPK + 25% Excess N RD-NK + STBP + 25% Excess N 5 RDF-NPK + 25% RD Zn RD-NK + STBP + 25% RD Zn Table.2 Salient characteristics of soil used in incubation study and pot culture experiment S No. Soil characters I) Physical properties a) Mechanical composition II) a) i) Sand (%) ii) Silt (%) iii) Clay (%) iv) Textural class (USDA) Physico-chemical properties Soil reaction (pH) (1:2.5 soil : water suspension) Electrical conductivity (1:2.5 soil : water extract) (dS m-1) Water Holding capacity (WHC at 33 KPa) (%) b) III) a) b) c) d) e) f) g) Soil used for incubation study Soil used for pot culture experiment 66 11 23 Clay loam 38 27 35 Silty clay loam 7.91 8.01 1.11 0.94 30.69 Available nutrients Nitrogen (kg ha-1) Phosphorus (kg P2O5 ha-1) Potassium (kg K2O ha-1) Sulphur (mg kg-1) Boron (mg kg-1) Free Calcium Carbonate (%) Available Micronutrients (ppm) 252 16 343 10.4 4.2 1.95 296 89 361 12 2.6 1.8 Cupper (Cu) Manganese (Mn) Iron (Fe) Zinc (Zn 6.21 4.11 10.22 2.12 4.72 3.22 14.58 1.66 1107 Int.J.Curr.Microbiol.App.Sci (2019) 8(10): 1102-1112 Table.3 Details of development of different P- fertility regimes using P- fixation Curve Desired Pfertility Regimes Low (< 23 kgP2O5/ha) Medium (23-56 P2O5/ha) High (56- 80 P2O5/ha) V. High (80110P2O5/ha) V.V High (> 110P2O5/ha) Desired availability of kg P2O5/ha for experiment Amount of P (µg/g) added using fig. 2 Amount of kg P2O5/ ha added to get desired Pregime Used as such (16kgP2O5/ha) 45 Used as such Used as such Final available kg P2O5/ha after 3 cycles of wetting and drying Used as such 26.0 133 40 70 40.2 206 63 100 57.2 293 102 125 71.9 368 128 Fig.1 P- Fixation characteristic curve of a low-P soil employed for development of different Pfertility regimes Fig.2 Detail P- Fixation curve obtained with selected range of P application 1108 Int.J.Curr.Microbiol.App.Sci (2019) 8(10): 1102-1112 Table.4 Effect of varying P- fertility and Nitrogen levels on Nitrogen availability at different contact periods: P-Fertility levels Nutrient Levels 100% RDN 125% RDN 150% RDN Grand Mean 15 D 30 D 45 D Mean 15 D 30 D 45 D 15 D 30 D 45 D Mean 231 Mea n 228 Low (16 kg P2O5/ha) Medium (40 P2O5/ha) High (63 P2O5/ha) V. High (102 P2O5/ha) V.V High (128 P2O5/ha) Mean 150 178 186 182 192 226 220 257 251 254 219 160 184 198 191 198 231 245 238 231 264 282 273 230 175 211 217 214 210 251 260 256 249 284 291 288 248 200 231 248 240 225 276 284 280 265 316 319 318 273 243 274 301 288 251 314 315 315 311 359 364 362 314 186 216 230 223 215 260 267 263 255 296 301 299 257 Factor P-Fertility levels (PF) Nutrient levels (NL) Contact periods (CP) PF X NL PF X CP NL X CP SEm( +) 2.35 1.82 1.82 4.08 4.08 3.16 PF X NL X CP NS CD (5%) 4.74 3.67 3.67 8.22 8.22 6.37 NS 1109 Int.J.Curr.Microbiol.App.Sci (2019) 8(10): 1102-1112 Table.5 Effect of varying P- fertility and Zinc levels on Zinc availability at different contact periods: P-Fertility levels 15 D 2.73 25% RDZn 30 D 45 D 2.51 2.79 2.41 2.28 High (63 P2O5/ha) 2.34 V. High (102 P2O5/ha) V.V High (128 P2O5/ha) Low (16 kg P2O5/ha) Medium (40 P2O5/ha) Mean Factor CD (5%) Nutrient Levels 50% RDZn 30 D 45 D Mean 2.94 3.21 3.05 15 D 3.30 100% RDZn 30 D 45 D 3.11 3.39 2.73 2.89 2.64 2.71 2.60 2.79 2.58 2.75 2.68 8.11 11.30 2.77 Mean 2.68 15 D 3.00 2.57 2.42 2.76 2.59 2.84 2.10 2.50 2.31 2.66 2.44 2.45 2.12 2.61 2.39 2.70 4.99 7.80 11.09 2.45 5.22 Grand Mean Mean 3.27 3.00 2.97 2.83 2.66 2.45 2.94 2.73 2.55 3.01 2.79 3.10 2.97 2.68 5.40 8.20 11.48 2.95 2.72 P-Fertility levels (PF) Nutrient levels (NL) Contact periods (CP) PF X NL PF X CP NL X CP PF X NL X CP 0.11 0.23 0.09 0.18 0.09 0.18 0.20 NS 0.20 NS 0.15 NS NS NS 1110 Int.J.Curr.Microbiol.App.Sci (2019) 8(10): 1102-1112 Table.6 Effect of different supplemental doses of nutrients and P levels on paddy grain and straw yield in a high P soil T. No T1 T2 T3 Treatments 100% RDF of NK RDF-NK + 25% Excess Nitrogen RDF-NK + 25% RD Zinc Mean S Em ( + ) CD (P= 0.05) Grain yield (gm pot-1) 100 % 70 % Mean RDP RDP 12.5 11.8 12.1 Straw yield (gm pot-1) 100 % 70 % Mean RDP RDP 14.9 14.2 14.6 13.7 12.3 13.0 16.6 15.1 15.9 13.9 11.4 12.7 17.1 14.1 15.6 13.7 Treatm ents (T) 0.30 0.64 12.5 P- Levels 13.1 TXP 15.1 P-Levels 15.9 TXP 0.14 0.30 0.44 NS 16.7 Treatme nts (T) 0.36 0.75 0.17 0.35 0.50 NS The recommendation to apply nutrients either in excess or when they are present in sufficient quantities (above critical limits) is not generally accepted practiced. However, the current study indicated that in a high P soil additional supply of nutrients beyond current recommendation is required and is helpful in improving the yield. On the other hand, Tabar (2012) reported highest yield of rice when highest levels of 150 kg N and 90 kg P fertilizer was added. Once again, these experiments were not conducted in a high P soil. In this experiment, Zn was also supplied (25 % RD Zn) though it was not required as per the critical limits in the soil. However, not much advantage was obtained due to additional Zn supply over and above 100 % recommended dose of fertilizer. On the other hand, Sri Ramya (2014) while working with zinc requirement for high P soil reported that about 7 per cent of higher yield of paddy can be realize in high P soil upon application of 12.5 kg ZnSO4 ha-1 even when the high P soil contain DTPA Zn of about 0.6 mg Zn kg soil-1. Das et al., (2005) suggested the synergistic interaction between phosphorus and zinc on their availability in soil in relation to their contents in Stevia (Stevia rebaudiana). In the present study the additional yields obtain due to supplementation with zinc to high P soil was only 5 %. These results points out that for a high P soil, though sufficient available nutrient (current critical limits) are present, additional supplementation of N would help in realizing higher yield in paddy crop in a high- P soil. On the other hand, reduced application of P (i, e 70 % RDP) significantly reduced the paddy grain yield over different treatments. Surendra babu et al., (2008) and Sri Ramya (2014) reported similar yield of paddy in a high- P soil even when P application was reduced by 25 per cent in high- P soil. The extent of benefits due to different supplemental nutrients both under 100 and 70 per cent RDP is shown in Table 6. In conclusion, it can be stated that for a high- P regime soil, the addition of different nutrient in small quantities of N and Zn as supplemental doses even when they are beyond recommendation levels this help in increasing the yield of paddy grain and straw yield. References Anonymous. 2010. Annual Report of Radio tracer Laboratory, (2008- 2010), ARI, ANGRAU, HYD-30. 1111