[0020] The method for grading calcareous purple soil phosphorus in the present invention first collects the calcareous purple soil sample air-dried through a 100-mesh sieve, and then uses a chemical extractant to extract step by step, that is, use different chemical reagents to extract the organic phosphorus and inorganic in the soil sample step by step Phosphorus component, the specific steps are as follows:
[0021] 1) Use deionized water to extract water-soluble phosphorus H from soil samples 2 O-P, including water-soluble organic phosphorus H 2 O-P o And water-soluble inorganic phosphorus H 2 O-P i;
[0022] 2) In the soil sample after step 1), the anion exchange resin is used to extract the easily transformable phosphorus in the soil sample, namely resin-soluble phosphorus Resin-P, including resin-soluble organic phosphorus Resin-P o And resin-soluble inorganic phosphorus Resin-P i;
[0023] 3) Sodium bicarbonate NaHCO is used in the soil sample after step 2) extraction 3 , Ammonium acetate NH 4 OAC, ammonium fluoride NH 4 F extracts active phosphorus in soil samples, mainly including active organic phosphorus La-P, dicalcium phosphate Ca 2 -P, octacalcium phosphate Ca 8 -P and aluminum phosphate Al-P; use chloroform CHCl at the same time 3 Extract microbial biomass SM-P;
[0024] 4) Sodium hydroxide NaOH and sodium citrate Na are used in the soil sample after step 3) extraction 3 C 6 H 5 O 7 Extract slow phosphorus from soil samples, including slow organic phosphorus Sl-P, iron-type phosphorus Fe-P and closed storage phosphorus O-P;
[0025] 5) In the soil sample after step 4), use HCl and ultrasonic to extract the chronic organophosphorus Ch-P and the organophosphorus Sonic-P in the soil sample o And inorganic phosphorus Sonic- P i , And calculate the stable organic phosphorus St-P in the soil;
[0026] 6) After step 5), the soil sample is extracted by ICP method to extract residual phosphorus Re-P.
[0027] The present invention will be further described in detail below with reference to the drawings and specific embodiments.
[0028] The specific operation of the limestone purple soil phosphorus classification of the present invention is as follows, see also figure 1 The technical roadmap shown:
[0029] (1) Weigh 1.0000g of soil sample (passing 100 mesh), place it in a 100ml centrifuge tube, add 50ml deionized water, shake for 1h (20-25℃), centrifuge for 8min (3500 r·min), and pass the supernatant through Filter the phosphorus-free filter paper into a 100ml Erlenmeyer flask, and use the molybdenum antimony method to determine H in the filtrate 2 O-P i , ICP method to determine the total phosphorus in the filtrate (P t1 ), H 2 O-P o Then use the difference subtraction method, namely H 2 O-P o =P t1 -(H 2 O-P i );
[0030] (2) Add 2g of NaCl saturated anion exchange resin and 50ml of deionized water to the above centrifuge tube, continuously shake for 16h (20-25℃), pour the suspension into a 100ml beaker equipped with 80 mesh sieve, and wash away with a small amount of water Soil particles, so that only resin remains on the sieve. Use 25ml 0.7M NaCl solution to transfer the sieve resin to a 50ml beaker, place the beaker on the electric hot plate for 45 minutes, after cooling, filter the solution into a 50ml volumetric flask, and use 0.7M NaCl solution to make the volume constant. Draw 40ml of the above solution and use the molybdenum antimony method to determine Resin-P in the filtrate i , ICP method to determine the total phosphorus in the filtrate (P t2 ), Resin-P o Use difference and subtraction, namely Resin-P o =P t2 -(Resin-P i );
[0031] (3) Transfer the suspension in the above 100ml beaker to a 100ml centrifuge tube, centrifuge for 8min (3500 r·min), discard the supernatant, and divide the soil residue into B 1 And B 2 Two groups, to the soil residue B 2 Add 50ml 0.5M NaHCO 3 The solution was shaken for 1h (20-25℃), centrifuged for 8min (3500 r·min), the supernatant was filtered through non-phosphorus filter paper into a 50ml Erlenmeyer flask, and the Ca in the filtrate was determined by the molybdenum antimony method 2 -P i , ICP method to determine the total phosphorus in the filtrate (P t3 ), NaHCO 3 -P o Then use the subtraction method, that is, NaHCO 3 -P o = P t3 -(Ca 2 -P i ); The soil residue B 1 Transfer to a 100ml beaker, put it in a desiccator, and put in a small beaker containing 30ml of 1M NaOH solution and 30ml of ethanol-free chloroform. Seal the desiccator with a small amount of petroleum jelly. Use a vacuum pump to evacuate until the chloroform boils and keep it for at least 2 min. Close the valve of the desiccator and place it in the dark at 25°C for 24 hours, transfer all the soil in the beaker to a 100ml centrifuge tube, and add 50ml 0.5M NaHCO 3 The solution was shaken for 1h (20-25℃), centrifuged for 8min (3500 r·min), the supernatant was filtered through a non-phosphorus filter paper into a 100ml Erlenmeyer flask, and the CHCl in the filtrate was determined by the molybdenum antimony method 3 /NaHCO 3 -P, microbial biomass phosphorus (SM-P) is: SM-P=(CHCl 3 /NaHCO 3 -P)-(Ca 2 -P i );
[0032] (4) After CHCl 3 / NaHCO 3 Soil residue B after leaching 1 Use 950ml·L -1 Wash twice with alcohol, discard the clear liquid. Then add 50ml 0.5M NH 4 OAC, shake for 1h (20-25℃), centrifuge for 8min (3500 r·min), filter the supernatant through non-phosphorus filter paper into a 100ml Erlenmeyer flask, and determine the Ca in the filtrate by the molybdenum antimony method 8 -P, ICP method to determine total phosphorus in the filtrate (P t4 ), NH 4 OAC-P o Use difference and subtraction, that is, NH 4 OAC-P o = P t4 -(Ca 8 -P);
[0033] (5) Wash the soil residue after leaching in the above step (4) with saturated NaCl solution twice, and discard the clear solution. Then add 50ml 0.5M NH 4 F, shake for 1h (20-25℃), centrifuge for 8min (3500 r·min), filter the supernatant through non-phosphorus filter paper into a 100ml Erlenmeyer flask, determine the Al-P in the filtrate by the molybdenum antimony method, and determine the filtrate by ICP method Total phosphorus (P t5 ), NH 4 F -P o Use difference and subtraction, that is, NH 4 F -P o = P t5 -(Al-P), the active organic phosphorus (La-P) is: La-P=NH 4 OAC-P o +NH 4 F -P o +NaHCO 3 -P o;
[0034] (6) NH 4 After F extraction, the soil residue was washed twice with saturated NaCl solution, and the clear liquid was discarded. Then add 50ml 0.1M NaOH, shake for 1h (20-25℃), centrifuge for 8min (3500 r·min), filter the supernatant through a non-phosphorus filter paper into a 100ml Erlenmeyer flask, and determine Fe-P in the filtrate by the molybdenum antimony method. ICP method to determine the total phosphorus in the filtrate (P t6-1 ), NaOH -P o Then use the subtraction method, that is, NaOH -P o = P t6-1 -(Fe-P). At the same time, draw 25ml of the filtrate into a 50ml centrifuge tube, add HCl to adjust the pH to 1.0-1.8, let stand overnight, filter through a non-phosphorus filter paper into a 50ml Erlenmeyer flask, and determine the NaOH/HCl-P in the filtrate by the molybdenum antimony method i , ICP method to determine the total phosphorus in the filtrate (P t6-2 ), NaOH/HCl -P o Then use the subtraction method, namely NaOH/HCl -P o = P t6-2 -(NaOH/HCl-P i );
[0035] (7) Wash the soil residue after NaOH extraction with saturated NaCl solution twice, and discard the clear solution. Then add 50ml 0.3M Na 3 C 6 H 5 O 7 , Shake for 1h (20-25℃), centrifuge for 8min (3500 r·min), filter the supernatant through a non-phosphorus filter paper into a 100ml Erlenmeyer flask, determine the OP in the filtrate by the molybdenum antimony method, and determine the total phosphorus in the filtrate by ICP method (P t7 ), Na 3 C 6 H 5 O 7 -P o Then use the difference subtraction method, namely Na 3 C 6 H 5 O 7 -P o = P t7 -(O-P). The slow organic phosphorus (Sl-P) in the soil is: Sl-P=NaOH/HCl -P o +Na 3 C 6 H 5 O 7 -P o;
[0036] (8) Na 3 C 6 H 5 O 7 The soil residue after leaching was washed twice with saturated NaCl solution, and the clear solution was discarded. Then add 20ml of 0.1M NaOH solution and place it in an ultrasonic disperser for dispersion. Add 30ml of 0.1M NaOH solution to the dispersed soil residue, shake for 1h (20-25℃), centrifuge for 8min (3500 r·min), and pass the supernatant Phosphorus filter paper is filtered into a 100ml Erlenmeyer flask, and the Sonic-P in the filtrate is determined by the molybdenum antimony method i , ICP method to determine the total phosphorus in the filtrate (P t8 ), Sonic -P o The difference and subtraction method is used, namely Sonic -P o = P t8 -(Sonic-P i );
[0037] (9) Add the above soil residue to 50ml 1M HCl, shake for 1h (20-25°C), centrifuge for 8min (3500 r·min), filter the supernatant through a non-phosphorus filter paper into a 100ml Erlenmeyer flask, and measure by molybdenum antimony method HCl-P in the filtrate i , ICP method to determine the total phosphorus in the filtrate (P t9 ), HCl -P o Then use the subtraction method, that is, HCl -P o = P t9 -(HCl-P i );
[0038] (10) Use the ICP method to determine the residual phosphorus (Re-P) of the above soil residue.
[0039] It should be particularly noted that the present invention uses different chemical extractants to dissociate and extract the soil phosphorus form and activity step by step according to the difference between the soil phosphorus form structure complex degree and activity. So as to achieve the purpose of separating soil phosphorus form. Therefore, the present invention has strict requirements on the selection and sequence of chemical extractants. First, the chemical extractant can not affect the composite degree and activity between the original phosphorus form and structure of the soil, nor can it stimulate the transformation and migration between the original phosphorus form and structure; secondly, the extraction sequence must be in accordance with the weak extractant The strong extractant is transformed step by step, that is, the chemical extraction ability is gradually enhanced. Otherwise, it may cause the loss of high-activity and low-complexity phosphorus forms in the soil and the increase of low-activity and high-complexity phosphorus forms, resulting in soil phosphorus The grading deviation of element form affects the effect of phosphorus grading.
[0040] Finally, it should be noted that the above-mentioned examples of the present invention are merely examples for illustrating the present invention, rather than limiting the embodiments of the present invention. Although the applicant has described the present invention in detail with reference to preferred embodiments, for those of ordinary skill in the art, other changes and modifications in different forms can be made on the basis of the foregoing description. It is not possible to give an exhaustive list of all implementation methods. All obvious changes or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.
