COMPLETION REPORT 1. Title of the Scheme : Studies on the fixation and release of phosphorus in different soils under the influence of soil conditioners 2. Location : AICRP WM Dept. of Agronomy Agricultural College & Research Institute Madurai - 625 104 Tamil Nadu, India 3. Name of the Institute : Tamil Nadu Agricultural University Coimbatore -641 003 Tamil Nadu, India 4. Principal Investigator : Dr.P.P.MAHENDRAN Professor (Soil Science) Department of Soil Science and Agricultural Chemistry Agricultural College & Research Institute Killikulam, Thoothukudi District, Tamil Nadu, India Co Principal Investigator(s) : 1. Dr. P. Balasubramaniam Professor and Head Department of Soil Science and Agricultural Chemistry Anbil Dharmalingam Agricultural College and Research Institute Trichy, Tamil Nadu, INDIA 2. Dr.A.Gurusamy Professor (Agronomy) Department of Agronomy Agricultural College and Research Institute Madurai, Tamil Nadu, INDIA 5. Name of the sponsor/ project owner / company : Borregaard SEA Pte, Ltd., (100% subsidiary of Borregaard AS, Norway) 111C, 4 th Floor, Telok Ayer Street, Singapore 068580 6. Background of the study Phosphorus is one of the major essential plant nutrients and without its adequate supply the plant can neither reveal its potential productivity nor complete its normal reproductive process. P deficiency in Indian soils is very serious. About 49 per cent soils test low in available P and the same percentage of them test medium. The widening ratio of N: P2O5: K2O in fertilizer application is worsening the situation.
Over mining the soil reserves of P and K in the intensively cropped irrigated areas, disproportionate use of N to P, low use efficiency (hardly 10-20%) and high P fixation in soils is adding another dimension to P problem of soils in India. To feed the galloping human population, it is estimated that India will need to more than double its consumption of fertilizers by the year 2025 and the needs for phosphatic fertilizer use will also be more than double. Realizing that the P reserves of the soil are not inexhaustible and for manufacture of phosphatic fertilizers the country depends on import of raw material, a sound policy and strategy are required for both manufacture and use of phosphates. Thus, understanding of the dynamism of P fixation, availability, mobilization and recycling becomes most important for development of strategy for use and management of P in soil. The acid soils are generally poor in productivity even after fertilization. One important nutritional problem of these soils is P deficiency, which is linked not only to low available P content of the soils but also to their capacity to fix fertilizer P in highly insoluble forms. Phophate fixation, consisting of adsorption and precipitation reactions is considered as primary cause of inefficient utilization of phosphorus. It is generally believed that adsorption is fast reaction occurring at low concentrations and precipitation is relatively slow process occurring at relatively higher concentrations. Surface adsorption is the dominant factor in determining the phosphate concentration levels in soil solution. In acid soils, phosphate is adsorbed on the surface of layered silicate clay minerals, and iron and aluminum oxides. The reservoir of P that is composed of adsorbed and precipitated P is a source for the regeneration of solution P, the concentration of which influences the diffusion of P to the plant roots and absorption by plants. The adsorption behavior of phosphate has been used to characterize the P supplying power of soils, to measure phosphate requirements of crops and the effectiveness of phosphatic fertilizers. Phosphate adsorption depends upon the properties of soils and P sources. It is, however, known that clay, organic matter, CaCO3 in alkaline calcareous soils and Fe 3+ and Al 3+ in acid soils play major role in phosphorus adsorption. Soils differ widely in their chemical and physical make up according to geological and geographical location. Consequently, it is almost impossible to draw a generalized fixation model from the results of the specific soils. The present study is, therefore, undertaken to examine the effect of soil properties on the phosphate adsorption and suitable soil amendments were worked for optimum P release in acid and alkali soils. 7. Work plan The investigation was taken up in laboratory condition with the following objectives. 1. Survey and collection of problem soils with varied P fixing capacity 2. Studying the quantitative fixation of P in acidic and calcareous sodic soils 3. Characterizing P release pattern in soil over a period of time with graded levels of P under the influence of soil conditioner To fulfill the above objectives, the following work plan was formulated
8. Technical programme Survey and Lab Study (Incubation Experiment) A. Soils 1. Acid soil 2. Calcareous sodic soil B. P Solutions (Potassium Dihydrogen Phosphate used as P source) 1. Control 2. 50 ppm P 3. 150 ppm P 4. 250 ppm P C. Soil Conditioner In all the treatments, known quantity of liquid formulation of test products (Soil Conditioner) were added at the following doses. 1. No product 2. Product 1 @ 10 kg/ha 3. Product 1 @ 20 kg/ha 4. Product 2 @ 4 kg/ha 5. Product 2 @ 8 kg/ha D. Period of incubation 7, 14, 21, 30 days The treatment combinations [2 soils x 4 P levels x 5 products x 4 periods of incubation = 160 x 2 = 320] in the lab study were statistically analyzed in Completely Randomized Design. PROTOCOL Acid Soil Phosphorus was extracted by following the procedure given by Bray and Kurtz (1945) and this method is primarily meant for soils which are moderate to strongly acidic with ph 5.5 or less. Procedure Five gram of soil was taken in a 100 ml plastic container. Prescribed doses of product 1 (@ 10 and 20 kg/ha) and product 2 (4 and 8 kg/ha) were added to the respective container based on the treatment schedule. Calculated quantities of P levels (0,50,150,250 ppm P) were also added and the samples were incubated for different periods viz., 7,14,21 and 30 days. After expiry of incubation periods, each container was added with 50ml of Bray s extractant (0.03N NH 4F + 0.025N HCL) and shaken for 5 minutes using mechanical shaker. Then filtering was done through Whatman No. 1 filter paper and preserved the filtrate. The filtrate was fed into Inductively Coupled Plasma - Optical Emission Spectroscopy (ICP-OES) and the extractable P was expressed in ppm (mg/kg).
Alkali Soil Phosphorus was extracted as per the method proposed by Olsen et al. (1954) as it is widely applicable for neutral, alkaline and calcareous soils Procedure Five gram of soil was taken in a 100 ml plastic container. Prescribed doses of product 1 (@ 10 and 20 kg/ha) and product 2 (4 and 8 kg/ha) were added to the respective container based on the treatment schedule. Calculated quantities of P levels (0,50,150,250 ppm P) were added and the samples were incubated for different periods viz., 7,14,21 and 30 days. After expiry of incubation periods, each container was added with a pinch of Dargo-G- 60 activated charcoal (P free) and 50ml of Olsen s extractant (0.5M NaHCO 3) and shaken for 30 minutes using mechanical shaker. Then filtering was done through Whatman No. 1 filter paper and preserved the filtrate. The filtrate was fed into Inductively Coupled Plasma - Optical Emission Spectroscopy (ICP-OES) and the extractable P was expressed in ppm (mg/kg). Determination of P fixing / releasing capacity of soils P fixed = P added to the soil - (P extracted from treatment P extracted from untreated control) x 100 P added to the soil The term phosphorus fixation refers the fixation of inorganic-p by Al, Fe oxides and Ca to produce P- containing compounds of lower solubility when P- fertilizers are added to soils. It involves series of reactions which removes P from soil solution render it unavailable for plants and reduces its efficiency to only 15-20% temporary or permanently depending upon stage / time of chemical fixation reactions. P-fixation in acidic soils Most of the P-fixation occurs in acidic soils, where H2PO4 reacts with the surface of insoluble oxides of iron, aluminum and manganese, involves series of chemical fixation reactions and thus interlocks the P. P-Fixation in alkaline soils The availability of P in alkaline soils is determined principally by the solubility of the various Ca-phosphate compounds present. In alkaline soils, soluble H2PO4 quickly reacts with calcium to form a sequence of products of decreasing solubility. For instance, highly soluble mono-calcium phosphate (CaH2PO4)4 added as concentrated superphosphate fertilizer rapidly reacts with calcium carbonate (CaCO3) to form first dicalcium phosphate and then reacts again with CaCO3 to form tri-calcium phosphate with decreasing solubility gradually. The tri-calcium phosphate may undergo further reactions to form even more insoluble compounds, such as, hydroxyl carbonates and hydroxyl apatites. These compounds are thousand times less soluble than freshly formed tricalcium phosphates. Note In acid soils, Iron and Aluminum compounds and some of the clay colloids are responsible for P fixation in soil. Similarly, calcium compounds will fix the added P to unavailable form in alkali soil. In this context, any soil amendment / conditioner believed to reduce P fixation must coat or form layer over the surface of the above mentioned compounds (Fe, Al, clay colloids and Ca compounds) which can fix the added P.
Based on this scientific background, the test products were mixed with the soil before adding P solutions. The test products may coat the compounds responsible for P fixation and cause significant decrease in the fixation of P in soil. Therefore, the test products were thoroughly mixed with the soil before adding P solutions. 9. Results The acid and alkali soils were collected and analyzed for the basic properties and the results are given below. Soil Properties of Acidic Soil S. No Soil Properties Value 1. ph 4.6 2. Electrical Conductivity (d S/m) 0.06 3. Clay(%) 33.5 4. Silt(%) 5.6 5. Coarse Sand(%) 37.3 7. Fine Sand(%) 22.1 8. Cation exchange capacity (cmol p+/kg) 10.3 9. Organic Carbon(%) 1.57 10. Organic Matter(%) 2.71 11. Iron Oxides(%) 9.82 12. Aluminium Oxides(%) 20.10 13. Sesquioxides (%) 29.92 14. Total P (%) 0.09 15. Available P (ppm) 1.60 Inference Acidic soil had low ph, high amount of clay, iron, aluminium and sesquioxides which are responsible for formation of insoluble P compounds in soil (P fixation). Soil Properties of Alkali Soil S. No Soil Properties Value 1. ph 9.2 2. Electrical Conductivity (d S/m) 1.02 3. Clay(%) 26.3 4. Silt(%) 13.2 5. Coarse Sand(%) 28.3 7. Fine Sand(%) 31.1 8. Cation exchange capacity (cmol p+/kg) 18.0 9. Organic Carbon(%) 0.41 10. Organic Matter(%) 0.71 11. Calcium carbonate (%) 2.80 12. Exchangeable sodium percentage 30.0 13. Total P (%) 0.21 14. Available P (ppm) 57.0 Inference Alkali soils had high ph, high concentration of clay, calcium carbonate, exchangeable sodium contents of soil may create favorable conditions for fixing P in the alkali soils. Low organic carbon may decrease the availability of P in soil.
Effect of test products on P availability in acid soils at different levels of added P 0 ppm P Treatment Particulars Extractable P at % P increased over control at 7 14 21 30 7 14 21 30 No product 1.6 1.6 1.7 1.6 1.63 - - - - Product 1 @10kg/ha 1.6 1.7 1.7 1.6 1.65 0 6.2 0 0 Product 1 @20kg/ha 1.5 1.6 1.6 1.7 1.60-0 - 6.2 Product 2 @4kg/ha 2.5 3.2 3.3 3.1 3.03 56.3 100 94.1 93.7 Product 2 @8kg/ha 3.3 3.5 3.4 3.6 3.45 106.2 118.7 100.0 125.0 2.10 2.32 2.34 2.32 DAI-Days after incubation SEd CD (0.05) Products (H) 0.14 0.29 P levels (P) 0.13 0.26 Period of incubation (I) 0.13 0.26 H x P x I 0.59 1.18 50 ppm P Treatment Particulars Extractable P at % P fixed at % P released at 7 14 21 30 7 14 21 30 7 14 21 30 No product 3.4 3.8 3.7 3.5 3.60 96.4 95.6 95.8 96.2 96.00 3.6 4.4 4.2 3.8 4.00 Product 1 @10kg/ha Product 1 @20kg/ha Product 2 @4kg/ha Product 2 @8kg/ha 11.7 16.2 17.8 17.4 15.77 79.8 70.8 67.6 68.4 71.65 20.2 29.2 32.4 31.6 28.35 11.7 16.0 17.3 17.2 15.55 79.8 71.2 68.6 68.8 72.10 20.2 28.8 31.4 31.2 27.90 4.6 6.3 7.8 7.9 6.65 94.0 90.6 87.6 87.4 89.90 6.0 9.4 12.4 12.6 10.10 13.5 17.3 18.8 18.5 17.02 76.2 68.6 65.6 66.2 69.15 23.8 31.4 34.4 33.8 30.85 8.98 11.92 13.08 12.90 85.24 79.36 77.04 77.40 14.76 20.64 22.96 22.60 SEd CD (0.05) SEd CD (0.05) Products (H) 0.14 0.29 0.11 0.23 P levels (P) 0.13 0.26 0.09 0.18 Period of incubation(i) 0.13 0.26 0.10 0.21 H x P x I 0.59 1.18 0.40 0.81
150 ppm P Treatment Particulars Extractable P at % P fixed at % P released at 7 14 21 30 7 14 21 30 7 14 21 30 No product 5.3 5.8 6.0 5.9 5.75 97.5 97.2 97.1 97.1 97.21 2.5 2.8 2.9 2.9 2.78 Product 1 @10kg/ha Product 1 @20kg/ha Product 2 @4kg/ha Product 2 @8kg/ha 17.2 25.1 24.2 22.3 22.20 89.6 84.3 84.9 86.2 86.23 10.4 15.7 15.1 13.8 13.76 18.1 26.3 25.8 25.2 23.85 89 83.5 83.9 84.3 85.15 11.0 16.5 16.1 15.7 14.85 6.5 10.3 12.2 11.7 10.17 96.7 94.2 92.9 93.3 94.27 3.3 5.8 7.1 6.7 5.72 20.0 30.4 31.3 30.8 28.12 87.7 80.8 80.2 80.5 82.26 12.3 19.2 19.8 19.5 17.73 13.42 19.58 19.90 19.18 92.10 87.99 87.78 88.24 7.90 12.01 12.22 11.76 SEd CD (0.05) SEd CD (0.05) Products (H) 0.14 0.29 0.11 0.23 P levels (P) 0.13 0.26 0.09 0.18 Period of incubation(i) 0.13 0.26 0.10 0.21 H x P x I 0.59 1.18 0.40 0.81 250 ppm P Treatment Particulars Extractable P at % P fixed at different DAI % P released at 7 14 21 30 7 14 21 30 7 14 21 30 No product 7.2 7.9 7.6 7.6 7.57 97.8 97.5 97.6 97.6 97.60 2.2 2.5 2.4 2.4 2.40 Product 1 @10kg/ha Product 1 @20kg/ha Product 2 @4kg/ha Product 2 @8kg/ha 18.3 26.3 25.9 24.1 24.02 93.3 90.1 90.3 91.0 91.16 6.7 9.9 9.7 9.0 8.83 20.4 28.1 27.9 26.0 25.60 92.5 89.4 89.5 90.2 90.40 7.5 10.6 10.5 9.8 9.60 7.7 11.6 13.8 13.5 11.65 97.6 96.0 95.1 95.2 95.98 2.4 4.0 4.9 4.8 4.01 26.3 31.2 31.4 29.3 29.55 90.1 88.2 88.1 88.9 88.81 9.9 11.8 11.9 11.1 11.18 15.98 21.02 21.32 20.40 94.24 92.22 92.11 92.60 5.76 7.78 7.89 7.40 SEd CD (0.05) SEd CD (0.05) Products (H) 0.14 0.29 0.11 0.23 P levels (P) 0.13 0.26 0.09 0.18 Period of incubation(i) 0.13 0.26 0.10 0.21 H x P x I 0.59 1.18 0.40 0.81
Acid soil RESULTS Extractable P The extractable P content increased successively with increasing levels of added P. The highest extractable P was recorded at 250 ppm P level while it was lowest in the soil without addition of P. Among the levels of products, the soils treated with Product 2 @ 8 kg/ha recorded significantly higher extractable P compared to other levels of products. The next best treatment in increasing the extractable P was product 1 applied @ of 20 kg/ha. The soils without product registerd the lowest extractable P. The period of incubation was also significantly influenced the extractable P in soil. The extractable P steadily increased up to 21 days after incubation and there after slight reduction was noticed. The interaction between levels of P, periods of incubation and levels of products had significant influence on the extractable P content in the soil. The acid soil treated with Product 2@ 8 kg/ha with 250 ppm P at 21 days after incubation recorded the highest extractable P. P Fixation Significant variation in per cent P fixation was noted among the products, levels of added P and days after incubation. In general, the per cent P fixation was decreased due to addition of products. The soils treated with product 2 @ 8 kg/ha was found to record lower values of per cent P fixation followed by product 1 (20 kg/ha and 10kg/ha) and product 2 (4 kg/ha). The highest value of per cent P fixation was noted in the soil without products.
Varying levels of added P was significantly influenced the percentage of P fixation in soils. Addition of P at 50 ppm recorded the lowest P fixation in the soils followed by 150 and 250 ppm P levels. The percentage of P fixation was higher during initial stage of P fixation (7 days), thereafter increasing periods of incubation up to 21 days decreased the P fixation considerably. The interaction between levels of P, products and period of incubation was significant. The combination of treatment viz., product 2 (8kg/ha), 50 ppm P and 21 days after incubation recorded the lowest values of per cent P fixation. P release It followed trend reverse to per cent P fixation. Among the products, soils treated with product 2 (8 kg/ha) recorded significantly higher P release values followed by product 1 applied at 20 and 10 kg /ha. The soils without products had low P release values. The per cent P release was significantly influenced by the levels of added P. The P level at 50 ppm registered higher P release values compared to 150 and 250 ppm P levels. The periods of incubation on per cent P release revealed that the P release registered a sharp increase due to increasing periods of incubation. The highest P release was observed under 21 days after incubation. The interaction of product 1 (8 kg/ha), 50 ppm P and 21 days after incubation was highly significant and their combination recorded the highest P release in acid soils.
Summary The performance of products 1 and 2 in acid soils without adding P was assessed with an aim to know whether the products having the ability to extract the P which has already fixed. It was noted that the product 1 has not released the P already fixed in acid soil. However this product addition can prevent the fixation of added P. Interestingly product 2 tried at two levels has the capacity to release the P already fixed in soil and also prevent the fixation of added P. The percentages of P increase due to addition of product 2 at 4 and 8 kg/ha ranged from 56 to 100 and 100 to 125 respectively compared to soil without products. The treatment of acid soils with the products significantly increased the extractable P at different periods of incubation compared to soil without products. The extractable P in acid soil without addition of products ranged from 3.4 to 3.8, 5.3 to 6.0 and 7.2 to 7.9 ppm respectively at 50,150 and 250 ppm of added P levels. Comparing the levels of product 1, 20 kg/ha performed better than the level 10 kg/ha. Similarly the product 2 at 8 kg/ha extracted more P compared to 4 kg/ha for the added P levels of 50,150 and 250 ppm. In general, the treatment of acid soils with products greatly reduced the P fixation. The reduction in P fixation was observed up to 21 days after incubation and thereafter the per cent P fixation was stabilized or slightly decreased. The percentage of P fixation in acid soil without products was more than 95 per cent. But acid soils treated with products significantly decreased the P fixation at different days after incubation. In general the product 1 added at 20 kg/ha reduced more P fixation compared to product 1 with 10 kg/ha at all the levels of added P. The product 2 applied at 8 kg/ha greatly decreased the P fixation compared to product 2 tried at 4 kg/ha.
Among the different levels of test products, the product 2 tried at 8 kg/ha is the best one in reducing the P fixation from 96.4 to 65.6, 97.5 to 80.2 and 97.8 to 88.1 per cent at 50,150 and 250 ppm of added P levels, respectively. Due to reduction in P fixation, the per cent P release was increased due to treatment of products. In acid soils without products, the P release ranged from 2.2 to 4.4 per cent only. But addition of products increased the per cent P release from 6.0 to 34.4 per cent. Comparing the levels of product 1, the acid soil treated with 20 kg/ha recorded numerically higher P release values than the level of 10 kg/ha for the added levels of 50,150 and 250 ppm P. In the same way, the product 2 applied at 8 kg/ha is superior in increasing the P release compared to the level of 4 kg/ha. Among the levels of test products, the product 2 applied at 8 kg/ha excelled other levels in releasing more P at different days after incubation. Comparing the per cent P fixation and P release at different levels of added P, addition of P at 50 ppm along with the products significantly decreased the P fixation and increased P release than 150 and 250 ppm P levels. It clearly indicates that the higher dose of P application, though it enhanced the extractable P, it is not correspondingly decreased the per cent P fixation in contradiction to the logical phenomenon. This might be due to occurrence of various reactions in soil with relevant to P fixation and availability and presence of other elements may also interfere with the availability of P or even the product may also be influenced by certain level of P addition.
Alkali Soil Effect of test products on P availability in alkali soils at different levels of added P 0 ppm P Treatment Particulars Extractable P at % P increased over control at 7 14 21 30 7 14 21 30 No product 57 56 57 58 56.98 - - - - Product 1 @10kg/ha Product 1 @20kg/ha Product 2 @4kg/ha Product 2 @8kg/ha 62 65 66 68 65.28 8.7 16.1 15.8 17.2 68 71 73 73 71.25 19.3 26.8 28.1 25.9 65 68 68 69 67.51 14.0 21.4 19.3 19.1 71 76 77 78 75.50 24.6 35.7 35.1 34.5 64.60 67.21 68.20 69.22 SEd CD (0.05) Products (H) 0.25 0.50 P levels (P) 0.22 0.45 Period of incubation (I) 0.22 0.45 H x P x I 1.02 2.03 50 ppm P Treatment Particulars Extractable P at % P fixed at % P released at 7 14 21 30 7 14 21 30 7 14 21 30 No product 91 93 93 92 92.25 32 28 28 30 68 72 72 70 Product 1 @10kg/ha Product 1 @20kg/ha Product 2 @4kg/ha Product 2 @8kg/ha 108 115 116 117 114.00-2 -16-18 -20 102 116 118 120 108 112 114 114 112.00-2 -10-14 -14 102 110 114 114 102 109 111 113 108.75 10-4 -8-12 90 104 108 112 109 117 119 118 115.75-4 -20-24 -22 104 120 124 122 103.6 109.2 110.6 110.8 SEd CD (0.05) Products (H) 0.25 0.50 P levels (P) 0.22 0.45 Period of incubation (I) 0.22 0.45 H x P x I 1.02 2.03
150ppm P Treatment Particulars Extractable P at % P fixed at % P released at 7 14 21 30 7 14 21 30 7 14 21 30 No product 108 115 118 114 113.75 66.0 61.3 59.3 62.0 62.05 34.0 38.7 40.7 38.0 37.95 Product 1 @10kg/ha Product 1 @20kg/ha Product 2 @4kg/ha Product 2 @8kg/ha 118 128 130 126 125.50 59.3 52.7 51.3 54.0 54.28 40.7 47.3 48.7 46.0 45.71 115 128 130 128 125.25 61.3 52.7 51.3 52.7 54.47 38.7 47.3 48.7 47.3 45.52 109 118 120 116 115.75 65.3 59.3 58.0 60.7 60.80 34.7 40.7 42.0 39.3 39.20 115 126 130 126 124.25 61.3 54.0 51.3 54.0 55.12 38.7 46.0 48.7 46.0 44.87 113.0 123.0 125.6 122.0 62.6 55.9 54.2 56.5 37.3 44.0 45.7 43.4 SEd CD (0.05) SEd CD (0.05) Products (H) 0.25 0.50 0.20 0.42 P levels (P) 0.22 0.45 0.13 0.26 Period of incubation(i) 0.22 0.45 0.18 0.37 H x P x I 1.02 2.03 0.58 1.19 250 ppm P Treatment Particulars Extractable P at % P fixed at % P released at 7 14 21 30 7 14 21 30 7 14 21 30 No product 120 128 136 131 128.75 74.8 71.6 68.4 70.4 71.27 25.2 28.4 31.6 29.6 28.72 Product 1 @10kg/ha Product 1 @20kg/ha Product 2 @4kg/ha Product 2 @8kg/ha 128 132 140 136 134.00 71.6 70.0 66.8 68.4 69.18 28.4 30.0 33.2 31.6 30.81 125 128 142 131 131.50 72.8 71.6 66.0 70.4 70.18 27.2 28.4 34.0 29.6 29.81 128 134 144 131 134.25 71.6 69.2 65.2 70.4 69.10 28.4 30.8 34.8 29.6 30.90 132 140 144 132 137.00 70.0 66.8 65.2 70.0 68.00 30.0 33.2 34.8 30.0 32.00 126.6 132.4 141.2 132.2 72.1 69.8 66.2 69.9 27.8 30.1 33.7 30.1 SEd CD (0.05) SEd CD (0.05) Products (H) 0.25 0.50 0.20 0.42 P levels (P) 0.22 0.45 0.13 0.26 Period of incubation(i) 0.22 0.45 0.18 0.37 H x P x I 1.02 2.03 0.58 1.19
Extractable P Alkali soil RESULTS Application of products significantly increased the extractable P at all the levels over control. The soils treated with product 2 (8 kg/ha) recorded the highest extractable P followed by product 1 (10 and 20 kg/ha) and product 2 (4 kg/ha). The soil without product registered the lowest extractable P. Addition of graded levels of P markedly influenced the extractable P content of soil. Among the levels, P added at 250 ppm recorded the highest extractable P followed by 150 and 50 ppm levels. The lowest extractable P was recorded by the soils without P. The extractable P was significantly influenced by the periods of incubation. The maximum extractable P was observed under 21 days after incubation. The combined effect of product 2 (8 kg/ha), 250 ppm P and 21 days after incubation registered the highest extractable P. P fixation and release The per cent P fixation was significantly influenced by the products. Application of product 2 @ 8 kg/ha and product 1@10 kg/ha favorably reduced the P fixation at all the P levels up to 21 days after incubation compared to other levels of products. The per cent P release was increased by the imposition of varying levels of products. Among the products, product 1 tried at 10 kg/ha and product 2 applied at 8 kg/ha recorded comparatively higher P release values compared to other products.
Summary Interestingly addition of both the products extracted P which has already fixed in the alkali soil compared to soil without products. The magnitude of efficiency in extracting P was more in case of product 2 at 8 kg/ha irrespective of different periods of incubation. The extractable P in alkali soil was correspondingly increased from 50 to 250 ppm of added P. In general, all the products behaved similarly and having the capacity to release the P originally fixed in the soil. Application of products with 50 ppm added P significantly enhanced the extractable P from 91 to 119 ppm. Among the different products, the product 2 tried at 8 kg/ha recorded the maximum extractable P at 21 days after incubation. Similarly the product 1 at 10 kg/ha also had a similar effect in extracting P. The product 2 at 4 kg/ha increased the extractable P over control, however it was less than product 2 at 8 kg/ha. In case of per cent P fixation, almost all the products recorded negative values which indicates that the extractable P was more and above the available as well as added P in the soil. Hence the negative sign was observed. This may be due to the release of already fixed P by the products in the soil. Similar observations on extractable P were also observed by the addition of 150 and 250 ppm of P levels. Further increasing levels of P addition from 50 to 250 ppm, there was an increasing trend of per cent P fixation with simultaneous reduction of P release was noticed. Among the different days after incubation, the P release was increased up to 21 days thereafter it was stabilized or slightly declined.
Conclusions Application of products 1 and 2 is highly effective in extracting P which has already fixed in the alkali soil. However in acid soil, the product 2 alone had the capacity to release the fixed P, but not product 1. The percentage of P fixation was greatly reduced by the application of products. Among the levels of products, product 2 applied at 8 kg/ha was found to superior in reducing the fixation of added P and increasing the release of P in acid soils. But in alkali soil, all the products behaved similarly in releasing the P in soil. Application of 50 ppm P with different levels of product 1 and product 2 significantly reduced the P fixation and correspondingly increased P release compared to 150 and 250 ppm of added P levels. Hence among the graded levels of P application, 50 ppm alone is sufficient for both acid and alkali soils. Further, the P recommendation for the majority of crops may not exceed 50 ppm P. These findings and fact clearly pave the way for recommending the suitability of products for acid and alkali soils for the purpose of reducing P fixation. Comparing the different days of incubation for P release, the extractable P was gradually enhanced up to 21 days by the application of products thereafter it was stabilized or declined. This finding clearly indicates that the products are highly effective in reducing the P fixation up to 21 days or even a month period. Among the levels of products, product 2 at 8 kg/ha excelled other levels in enhancing the P release and reducing the P fixation in acid and alkali soils. Hence it may be concluded that application of product 2 at 8 kg/ha would be the best option for acid soil for reducing the P fixation. However for alkali soil either product 1 or product 2 may be recommended after considering its cost. These findings of lab study need to be investigated in detail by conducting pot culture experiment as biological release is most important than chemical release for the uptake of phosphorus. Hence the products are to be studied under biological release condition by growing plants for drawing a sound scientific conclusion.
Pot Experiment Based on the lab research work, it has been concluded that application of product 2 at 8 kg/ha would be the best option for reducing the P fixation in acid soils. However for alkali soil, product 1 and product 2 performed equally in reducing the P fixation. Hence, a preliminary study under pot culture experimentation was conducted in acid soil using the product 2 (8kg/ha) alone with the test crops like maize, black gram and brinjal. The following are the treatment structure. Number of test crops : 3 ( Maize, black gram and brinjal) Number of pots taken : 9 (3 pots per crop) Number of pots with the product 2 @ 8 kg/ha : 6 (2 pots per crop) Number of pots without test products : 3 (1 pot per crop) Two and half kg of soil was taken in each pot and thoroughly mixed with the product 2 @ 8 kg/ha. Based on the recommended dose of P for each crop, amount of P fertilizer was calculated and applied by following standard procedures. Then test crops were grown in the pots and crops were grown for a period of 21 days with recommended management practices. After 21 days, the plants were uprooted and data on Dry Matter Production (DMP), P content and P uptake and root volume for each test crop was recorded. Soil samples were collected at weekly interval from the pots up to a period of 21 days for the estimation of available P, percentage of P fixation and release. Note: 1. For recording the DMP, five plants were uprooted, washed in distilled water, dried in hot air oven and finally the average of 5 plants weight is recorded as dry weight. 2. Total P concentration in plant was estimated by following standard protocol 3. P uptake was computed in plants using DMP and Total P Properties of Acidic Soil S. No Soil Properties Value 1. ph 4.9 2. Electrical Conductivity (d S/m) 0.04 3. Organic Carbon(%) 1.60 4. Organic Matter(%) 2.75 5. Total P (%) 0.09 6. Available P (ppm) 1.90
Performance of product 2 @ 8kg/ha on DMP, P content and P uptake of Maize Treatments DMP (g/plant) P content (%) P uptake (mg/plant) Root volume (ml) T 1-Control (No product) T 2- Product 2 @8 kg/ha 2.15 0.14 3.01 0.90 8.92 0.16 14.27 1.70 Performance of product 2 @ 8kg/ha on DMP, P content and P uptake of Brinjal Treatments DMP (g/plant) P content (%) T 1-Control (No product) T 2- Product 2 @8 kg/ha P uptake (mg/plant) Root volume (ml) 4.26 0.52 22.15 1.10 8.31 0.61 50.69 2.20 Performance of product 2 @ 8kg/ha on DMP, P content and P uptake of Black gram Treatments DMP (g/plant) P content (%) T 1-Control (No product) T 2- Product 2 @8 kg/ha P uptake (mg/plant) Root volume (ml) 2.72 0.21 5.71 0.82 9.05 0.28 25.34 2.90 Application of product 2 (8kg/ha) in acid soil had a profound influence on Dry Matter Production (DMP). The soil treated with the product recorded the highest DMP in all the test crops while it was lowest in the soil without addition of product. The combined effect of product and rhizosphere region of crops released more available P in soil and hence the test crops could absorb P efficiently and recorded the highest P uptake comparing to the crop grown under untreated soil. Root proliferation is stimulated when soil is rich in available P. Owing to release of native as well as added P in soil due to influence of product and rhizosphere, more root volume was noticed in the test crops. The plants grown in soil without test product registered low root volume. The rhizosphere is the critical zone of interactions among plants, soils, and microorganisms. Plant roots can greatly modify the rhizosphere environment through their various physiological activities, particularly the exudation of organic compounds such as mucilage, organic acids, phosphatases, and some specific signaling substances, which are key drivers of various rhizosphere processes. The
chemical and biological processes in the rhizosphere not only determine mobilization and acquisition of soil nutrients as well as microbial dynamics, but also control nutrient use efficiency of crops, and thus profoundly influence crop productivity. Effect of test product on P availability in acid soil grown with Maize Added P: 15ppm Treatments T 1-Control (No product) T 2- Product 2 @8 kg/ha Extractable P in acid soil (ppm) 7 DAS 15 DAS 21 DAS 3.10 3.80 4.90 5.80 7.10 9.60 DAS Days after sowing: Initial soil available P = 1.90 ppm Effect of test product on P availability in acid soil grown with Brinjal Added P: 10 ppm Treatments T 1-Control (No product) T 2- Product 2 @8 kg/ha Extractable P (ppm) 7 DAP 15 DAP 21 DAP 2.40 2.90 3.70 4.80 5.60 7.90 DAS Days after sowing: Initial soil available P = 1.90 ppm Effect of test product on P availability in acid soil grown with Black gram Added P: 10 ppm Treatments T 1-Control (No product) T 2- Product 2 @8 kg/ha Extractable P (ppm) 7 DAP 15 DAP 21 DAP 2.90 3.50 4.70 5.10 6.80 8.90 DAP Days after planting: Initial soil available P = 1.90 ppm The plant available P was extracted at weekly interval in the experimental soils. In general there was an increasing trend of extractable P both in treated and untreated soils. However, the magnitude of release of available P was more in product treated soils. A steady state of release of P was noticed from 7 to 21 days of crop growth in the soils received the test product. This could be possible due to combined influence of product and rhizosphere in the soil.
Effect of test product on P fixation and release in acid soil grown with Maize Treatments T 1-Control (No product) T 2- Product 2 @8 kg/ha Per cent P fixation at different DAS Per cent P release at different DAS 7 14 21 7 14 21 92 87 80 8 13 20 74 65 48 26 35 52 Effect of test product on P fixation and release in acid soil grown with Black gram Treatments Per cent P fixation at different DAS Per cent P release at different DAS 7 14 21 7 14 21 T 1-Control (No product) T 2- Product 2 @8 kg/ha 90 84 72 10 16 28 68 51 30 32 49 70 Effect of test product on P fixation and release in acid soil grown with Brinjal Treatments Per cent P fixation at different DAP Per cent P release at different DAP 7 14 21 7 14 21 T 1-Control (No product) T 2- Product 2 @8 kg/ha 95 90 82 5 10 18 71 63 40 29 37 60 Spectacular variation in per cent P fixation was noted between treated and untreated soils. The percentage of P fixation in acid soil without product was more than 70 per cent. However, there was a remarkable release of P was observed due to integration of product 2 (8 kg/ha) and test crops. The soils treated with product 2 @ 8 kg/ha and grown with maize and black gram crops were found to record lower values of per cent P fixation. The percentage of P fixation was higher during initial stage of P fixation (7 days after sowing), thereafter increasing periods of crop growth up to 21 days decreased the P fixation considerably.
In acid soils, iron and aluminium compounds and some of the clay colloids are responsible for P fixation in soil. The test product may coat or form layer over the compounds responsible for P fixation and that could be a possible reason for decreasing the fixation of P in soil. It has been well proved that the concentration of P ions in the soil solution is governed by common major factors, namely: (i) ph, (ii) the concentrations of metal cations such as Ca, Fe and Al and (iii) the concentrations of competing inorganic (especially bicarbonate, and possibly sulphate) and organic ligands such as carboxylic anions. By modifying these factors as a consequence of their uptake and exudation activities, plant roots can indeed shift the chemical equilibria that determine the mobility and bioavailability of soil inorganic P. However, it seems that the relative importance of the various processes involved in such root-induced modifications of the bioavailability of soil P is still largely unknown. A great deal of research has focussed on the exudation of organic anions and protons and their effect on P bioavailability, whereas little has been done on the effect of the release of inorganic ligands such as bicarbonate ions. All these processes will possibly result in a build-up of P concentration in the soil solution and, hence in an increased bioavailability of P to plants. Conclusion Application of product 2 @8 kg/ha has shown positive results in reducing P fixation and enhancing crop growth. The combination of product and growing crops in acid soil had added advantage in releasing more P and convincingly reduced the P fixation. Hence, application of product 2 @ 8kg/ha to the crops grown in acid soils is a suitable management practice in reducing P fixation and increasing the P concentration in soil. However these findings should be confirmed by doing field experiments under natural conditions.
Annexure - I Procedure adopted for calculating doses of products (Lab study) Product 1 (10 and 20 kg/ha) 2000000 kg soil = 10 kg 5 kg soil = 50/2000000 = 0.000025 kg 5 kg 0.025 g 5000g = 0.025 g 5g = 5 x 0.025 5000 = 0.000025g = 0.025 mg = 25µg = 25 ppm 1 ml of 25 ppm to 5 g soil = 10 kg /ha 2 ml of 25 ppm to 5 g soil = 20 kg /ha Product 2 (4 and 8 kg/ha) 2000000 kg soil = 4 kg 5 kg soil = 20/2000000 = 0.00001 kg 5 kg 0.01 g 5000g = 0.01 g 5g = 5 x 0.01 5000 = 0.00001g = 0.01 mg = 10µg = 10 ppm 1 ml of 10 ppm to 5 g soil = 4 kg /ha 2 ml of 10 ppm to 5 g soil = 8 kg /ha
Annexure - II Procedure adopted for calculating varying levels of P (Lab study) 50 ppm - P 50 mg P/ kg of soil 1000 g of soil = 50 mg P 5g of soil = 0.25 mg P 5g soil needs 250 µg P Prepared 50 ppm P and added 5 ml to 5g soil =250µg P 150 ppm - P 150 mg P/kg of soil Prepared 150 ppm and added 5 ml to 5g soil = 750 µg P 250 ppm - P 250 mg P/kg of soil Prepared 250 ppm added 5 ml to 5g soil = 1250 µg P
Annexure III Liquid form of products for incubation experiment
Annexure IV Analyzing samples using ICP (OES) at TNAU, Coimbatore
Annexure - V Effect of test products on extractable P in acid soils at different levels of added P (Lab study) 0 ppm P Extractable P (mg/kg) at Treatment Particulars 7 14 21 30 R1 R2 R1 R2 R1 R2 R1 R2 No product 1.5 1.7 1.4 1.8 1.6 1.8 1.9 1.3 Product 1 @10kg/ha 1.6 1.6 1.7 1.7 1.5 1.9 1.6 1.6 Product 1 @20kg/ha 1.4 1.6 1.2 2.0 1.7 1.5 1.4 2.0 Product 2 @4kg/ha 2.3 2.7 3.1 3.3 3.3 3.3 3.0 3.2 Product 2 @8kg/ha 3.4 3.2 3.6 3.4 3.3 3.5 3.7 3.5 50 ppm P Extractable P (mg/kg) at Treatment Particulars 7 14 21 30 R1 R2 R1 R2 R1 R2 R1 R2 No product 3.2 3.6 3.7 3.9 3.6 3.8 3.5 3.5 Product 1 @10kg/ha 11.8 11.6 16.3 16.1 17.9 17.7 17.2 17.6 Product 1 @20kg/ha 11.9 11.5 16.0 16.0 17.1 17.5 17.2 17.2 Product 2 @4kg/ha 4.5 4.7 6.2 6.4 7.7 7.9 7.8 8.0 Product 2 @8kg/ha 13.6 13.4 17.5 17.1 18.7 18.9 18.3 18.7
150 ppm P Annexure V continued Extractable P (mg/kg) at Treatment Particulars 7 14 21 30 R1 R2 R1 R2 R1 R2 R1 R2 No product 5.4 5.2 5.7 5.9 5.8 6.2 6.0 5.8 Product 1 @10kg/ha 17.1 17.3 25.0 25.2 24.1 24.3 22.1 22.5 Product 1 @20kg/ha 18.0 18.2 28.4 24.2 25.7 25.9 25.1 25.3 Product 2 @4kg/ha 6.4 6.6 10.2 10.4 12.1 12.3 12.0 11.4 Product 2 @8kg/ha 19.0 21.0 29.5 31.3 30.2 32.4 30.7 30.9 250 ppm P Extractable P (mg/kg) at Treatment Particulars 7 14 21 30 R1 R2 R1 R2 R1 R2 R1 R2 No product 7.1 7.3 7.7 8.1 7.5 7.7 7.4 7.8 Product 1 @10kg/ha 18.4 18.2 26.1 26.5 25.8 26.0 23.4 24.8 Product 1 @20kg/ha 20.3 20.5 28.1 28.1 27.7 28.1 25.9 26.1 Product 2 @4kg/ha 7.6 7.8 11.4 11.8 13.7 13.9 13.4 13.6 Product 2 @8kg/ha 26.2 26.4 31.1 31.3 30.3 32.5 29.0 29.6
Annexure - VI Effect of test products on extractable P in alkali soils at different levels of added P (Lab study) 0 ppm P Extractable P (mg/kg) at Treatment Particulars 7 14 21 30 R1 R2 R1 R2 R1 R2 R1 R2 No product 57.3 56.7 56.3 55.7 57.0 57.0 57.1 58.8 Product 1 @10kg/ha 61.4 62.6 64.7 65.3 66.4 65.6 68.2 68.1 Product 1 @20kg/ha 68.0 68.0 70.9 71.1 72.4 73.6 72.7 73.3 Product 2 @4kg/ha 65.2 64.8 68.1 68.0 67.2 68.8 68.0 70.0 Product 2 @8kg/ha 69.8 72.2 76.3 75.7 77.5 76.5 79.6 76.4 50 ppm P Extractable P (mg/kg) at Treatment Particulars 7 14 21 30 R1 R2 R1 R2 R1 R2 R1 R2 No product 90.7 91.3 93.0 93.0 94.0 92.0 91.9 92.1 Product 1 @10kg/ha 109.0 107.0 115.0 115.0 116.0 116.0 116.0 118.0 Product 1 @20kg/ha 108.0 108.0 113.0 111.0 114.0 114.0 113.7 114.3 Product 2 @4kg/ha 101.8 102.2 109.6 108.4 110.6 111.4 111.8 114.2 Product 2 @8kg/ha 108.6 109.4 116.7 117.3 118.5 119.5 118.0 118.0
150 ppm P Annexure VI continued Extractable P (mg/kg) at Treatment Particulars 7 14 21 30 R1 R2 R1 R2 R1 R2 R1 R2 No product 107.6 108.4 113.9 116.1 118.0 118.0 113.0 115.0 Product 1 @10kg/ha 118.0 118.0 127.7 128.3 131.0 129.0 125.8 126.2 Product 1 @20kg/ha 116.0 114.0 127.8 128.2 130.0 130.0 127.5 128.5 Product 2 @4kg/ha 109.0 109.0 117.9 118.1 119.0 121.0 117.0 115.0 Product 2 @8kg/ha 114.8 115.2 125.6 126.4 129.0 131.0 124.6 127.4 250 ppm P Extractable P (mg/kg) at Treatment Particulars 7 14 21 30 R1 R2 R1 R2 R1 R2 R1 R2 No product 119.0 121.0 128.0 128.0 135.8 136.2 132.1 129.9 Product 1 @10kg/ha 126.5 129.5 132.0 132.0 139.9 140.1 138.0 134.0 Product 1 @20kg/ha 125.0 125.0 127.0 129.0 141.6 142.4 131.0 131.0 Product 2 @4kg/ha 127.0 129.0 133.0 135.0 143.0 145.0 132.0 130.0 Product 2 @8kg/ha 132.0 132.0 142.0 138.0 144.0 144.0 132.0 132.0
Annexure VII Product 2 (8 kg/ha) calculation for pot experiment 2000000 kg soil = 8 kg 2.5 kg soil = 2.5x 8 2000000 = 0.00001 kg 2. 5 kg soil needs = 0.01 g = 10 mg = 10,000 microgram of product 2 Add 10000 micro gram of product 2 to the soil of 2.5 kg Prepare 1000 ppm of product 2 and add 10ml to 2.5 kg soil To prepare 1000ppm of product 2 =weigh 1 g (or) 1000 mg dissolved in to 1000ml of water
Annexure VIII P fertilizer calculations for pot experiment Brinjal / Pulse Recommended dose = 50kg P2O5/ha 50Kg P2O5/ha 2000000Kg soil = 50 0.4= 20 Kg P/ha = 20Kg P 2.5 Kg soil= 2.5 20.0 2000000 = 0.000025 Kg 2.5 Kg soil needs = 0.025g P =25mg P = 25,000microgram P Add 25000 microgram of P to the soil of 2.5 Kg. Prepare 1000 ppm of P; add 25ml to 2.5Kg soil. Maize Recommended dose = 75Kg P2O5/ha 75Kg P2O5/ha 2000000Kg soil = 75 0.4= 30Kg P/ha = 30Kg P 2.5 Kg soil= 2.5 30.0 2000000 = 0.0000375 Kg 2.5 Kg soil needs = 0.0375g P =37.5mg P = 37,500 microgram P Add 37,500 microgram of P to the soil of 2.5 Kg. Prepare 1000 ppm of P; add 37.5ml to 2.5Kg soil.
Annexure IX POT CULTURE EXPERIMENT Maize Black gram Brinjal (egg plant)