Rapid diagnosis method for potassium nutrition of sweet potatoes

Abstract

The invention discloses a rapid diagnosis method for potassium nutrition of sweet potatoes, which comprises the following steps: measuring potassium concentrations of inverted 5 petioles and positive 1 petioles, calculating a difference value, fitting by taking a horizontal coordinate as a petiole concentration difference and a vertical coordinate as a relative yield, and constructing a regression equation 1 of the petiole potassium concentration difference and the relative yield; according to the regression equation 1, taking the corresponding petiole potassium concentration when the relative yield is maximum as the critical concentration of plant potassium nutrition diagnosis; performing correlation analysis on the plant potassium absorption amount and the petiole potassium concentration difference value to obtain a regression equation 2; comparing the measured value with the critical value petiole potassium concentration, determining the topdressing coefficient, and calculating the topdressing amount in the period. The diagnosis method can timely and accurately judge the potassium nutrition condition of the sweet potato plants, provides a basis for subsequent accurate application amount of sweet potato potash fertilizer, and can improve the yield and quality of sweet potatoes.

Description

Technical Field

[0001] The invention relates to the field of rapid diagnosis methods for plant potassium nutrition, and in particular to a rapid diagnosis method for sweet potato potassium nutrition. Background Art

[0002] Sweet potato is a typical potassium-loving crop. Potassium fertilizer plays an irreplaceable role as a key factor in regulating the growth of sweet potato, and has an important impact on the tuber enlargement and yield formation of sweet potato. In order to save time and effort and obtain considerable yields, the potassium fertilizer application method for sweet potato is mostly a "one-shot" mode. The peak period of potassium absorption of sweet potato is in the middle of growth. The potassium fertilizer applied as a base will lead to insufficient potassium supply in the soil in the later stage due to reasons such as rain leaching or soil fixation, resulting in reduced potassium utilization efficiency. Sweet potato plants may be in a state of latent potassium deficiency, thereby limiting the increase in yield. Therefore, how to timely and accurately judge the potassium nutritional status of sweet potato and apply potassium fertilizer reasonably is a production technology problem that needs to be solved urgently in the current high-yield cultivation of sweet potato.

[0003] At present, the diagnosis of sweet potato potassium nutrition is based on the combination of the maximum biomass critical concentration curve and the KNI value as the diagnostic basis. This method requires destructive sampling and the determination of potassium content in the laboratory using a flame photometer, which takes a lot of time and cannot provide timely feedback on the potassium nutritional status of sweet potato plants.

[0004] The existing potassium nutrition diagnosis of potatoes is based on the fourth petiole as the diagnostic part for potassium nutrition diagnosis. The potassium concentration of the fourth petiole is quickly measured and fitted with the potassium content of the fourth petiole, aboveground part and underground part measured by the flame photometer. The fitting coefficient is good, and it is concluded that the potassium concentration of the fourth petiole can be used to evaluate the potassium nutrition status of potato plants. Although the potassium nutrition status of plants can be evaluated in time, the amount of fertilizer to be applied after potassium deficiency is not clear, and potassium fertilizer cannot be supplemented in time when the plant does have hidden potassium deficiency.

[0005] The existing potassium nutrition diagnosis of potatoes mentioned above is not suitable for sweet potatoes, and the existing sweet potato potassium nutrition diagnosis method is time-consuming and labor-intensive, and the nutritional status feedback is not timely. Therefore, the existing technology needs to be further improved. Summary of the invention

[0006] In response to the above problems, the present invention provides a new method for rapid diagnosis of sweet potato potassium nutrition, which can timely and accurately judge the potassium nutritional status of sweet potato plants, and then calculate the precise potassium fertilizer application amount by introducing the fertilization model, thereby providing a basis for subsequently improving the accuracy of sweet potato potassium fertilizer application, thereby improving the yield and quality of sweet potatoes, and has significant economic benefits.

[0007] To solve the above problems, this application provides the following technical solutions:

[0008] A method for rapid diagnosis of sweet potato potassium nutrition, comprising the following steps:

[0009] S1. Set different gradients of potassium fertilizer application in the field to conduct potassium nutrition diagnosis during the whole growth period. The petioles selected for sampling are: the petiole of the fifth fully expanded functional leaf and the first petiole at the base from the top;

[0010] S2. Sampling was carried out at 30d, 60d, 75d and 90d after transplanting. Ten plants were taken each time, and their fresh weight was measured to obtain relative yield. The potassium concentration of the petiole 5 and the petiole 1 was measured by taking 7 plants, and the difference was calculated. Three plants were then taken for sterilization and drying, and their biomass and potassium content were measured to calculate the potassium absorption of the plants.

[0011] S3, sweet potato, the potassium concentration difference between the fifth petiole of the fully expanded functional leaf and the first petiole at the base from the top is used as the petiole potassium concentration difference L of the diagnostic site c , L c =L top5 -L root1 ;

[0012] S4. Fitting is performed with the petiole potassium concentration difference as the horizontal axis and the relative yield as the vertical axis, and a regression equation 1 of the petiole potassium concentration difference and relative yield is constructed: Y d =aL c 2 +bL c +c;

[0013] In regression equation 1, Y d Represents the relative output in each period, L c represents the difference in potassium concentration in petiole, a, b, c regression equation coefficients; according to the regression equation, when Y d The period L corresponding to the maximum value c The value is used as the critical concentration for diagnosing potassium nutrition in petiole concentration difference, namely Lc 临界 ;

[0014] S4. Correlation analysis was performed on the potassium absorption of sweet potato plants and the difference in potassium concentration of sweet potato petioles to obtain regression equation 2: Y re =a 2 L c 2 +b 2 L c +c 2 ,

[0015] In equation 2, Y re Indicates the potassium absorption of the aboveground part, L c represents the measured petiole potassium concentration difference, a 2 , b 2 、c 2 Regression equation coefficients;

[0016] The Lc obtained in regression equation 1 临界Substitute into regression equation 2 to obtain the potassium absorption amount Y under the critical concentration difference of petiole in this period th ;

[0017] S5. Compare the measured value with the critical value of petiole potassium concentration to determine the topdressing coefficient, α = (Y th -Y re ) / Y th ,

[0018] Among them, α is the topdressing coefficient, Y th Y is the potassium absorption amount under the critical concentration difference of petiole during the period, re It is the potassium absorption amount under the actual petiole concentration difference during this period.

[0019] S6. Substitute the above-mentioned topdressing coefficient into the topdressing model to calculate the amount of topdressing for this period.

[0020] Optionally, in step S2 of the sweet potato potassium nutrition rapid diagnosis method, the potassium concentrations of the petioles 5 to 1 and 1 to 2 are measured using a portable potassium ion meter.

[0021] Optionally, in step S7 of the sweet potato potassium nutrition rapid diagnosis method, the topdressing model is K=K'*[1+α], where K is the actual topdressing potassium amount in this period, K' is the planned topdressing potassium amount in this period, and α is the topdressing coefficient.

[0022] Optionally, in the sweet potato potassium nutrition rapid diagnosis method, the regression equation 1 is:

[0023] Y 30 =-1.23E-04x 2 +0.2295x-6.29, R 2 =0.9983;

[0024] Y 60 =-6.58E-04x 2 +0.993x-229.43, R 2 =0.9713;

[0025] Y 75 =-0.0012x 2 +1.1815x-190.96, R 2 =0.9833;

[0026] Y 90 =-0.52E-04x 2 +0.2508x+83.15, R 2 =0.9153.

[0027] Optionally, in the sweet potato potassium nutrition rapid diagnosis method, Equation 2 is:

[0028] Y re30 =2E-05x 2 -0.1019x+107.45;

[0029] Y re60 =-1.75E-04x 2 +0.1246x+105.56;

[0030] Y re75 =-0.00105x 2 +0.9932x-117.78;

[0031] Y re90 =1.20E-05x 2 -0.1477x+135.40.

[0032] Optionally, in the sweet potato potassium nutrition rapid diagnosis method, the topdressing coefficient α for each period is:

[0033] α 30 =(27.12-Y re ) / 27.12;

[0034] α 60 =(110.26-Y re ) / 110.26;

[0035] α 75 =(115.56-Y re ) / 115.56;

[0036] α 90 =(119.3-Y re ) / 119.3.

[0037] Optionally, in the sweet potato potassium nutrition rapid diagnosis method, the potassium supplementation models planned for each period are:

[0038] K 30 =77.84*[1+(27.12-Y re ) / 27.12];

[0039] K 60 =77.84*[1+(110.26-Y re ) / 110.26];

[0040] K 75 =89.79*[1+(115.56-Y re ) / 115.56];

[0041] K 90 =89.79*[1+(119.3-Yre ) / 119.3].

[0042] The above-mentioned rapid diagnosis method for sweet potato potassium nutrition is based on the growth characteristics of sweet potato, and can realize rapid diagnosis of sweet potato potassium nutrition. The rapid diagnosis of sweet potato potassium nutrition in the seedling stage is most accurate by using the difference in potassium concentration between the petiole 5 and the petiole 1. Compared with the traditional topdressing method, the use of this method for fertilization can significantly increase the sweet potato yield, increasing the sweet potato yield by 11.6% and the commercial potato rate by 16%.

[0043] The present invention has the following beneficial effects:

[0044] 1. The sweet potato potassium nutrition rapid diagnosis method provided by the present invention is a rapid diagnosis of potassium nutrition based on a specific petiole concentration difference. The rapid diagnosis of potassium nutrition in the sweet potato seedling stage using the difference in potassium concentration between the petiole 5 and the petiole 1 is the most accurate. The potassium nutrition status of the sweet potato can be judged in a timely and accurate manner, providing a basis for improving the accuracy of subsequent calculation of the amount of potassium fertilizer applied to the sweet potato. After fertilization using this method, the yield and quality of the sweet potato are significantly improved.

[0045] 2. The diagnostic method of the present invention avoids the destructive sampling method of flame photometer, and adopts a handheld potassium ion meter to measure the potassium content of the petiole of the sweet potato. The determination method is simplified and the results are more timely.

[0046] 3. Compared with the diagnosis of potato single petiole, the diagnosis of sweet potato based on petiole concentration difference has a higher fit with relative yield, which proves that petiole concentration difference can better evaluate the potassium nutrition status of sweet potato plants. Compared with the critical dilution potassium concentration curve of sweet potato, the rapid diagnosis of sweet potato based on petiole concentration difference can make a real-time and rapid judgment on the potassium nutrition status of sweet potato plants and determine whether there is a hidden potassium deficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This paper is the correlation analysis between biological indicators of sweet potato seedlings and petiole potassium concentration. DETAILED DESCRIPTION

[0048] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention. In the present invention, unless otherwise specified, the equipment and raw materials used can be purchased from the market or are commonly used in the art. The methods in the following embodiments are conventional methods in the art unless otherwise specified.

[0049] Example 1 Potassium nutrition diagnosis method based on the potassium concentration difference of petioles during the growth period of sweet potato

[0050] This embodiment provides a potassium nutrition diagnosis method based on the potassium concentration difference of petioles during the growth period of sweet potatoes, and the method comprises the following steps:

[0051] (1) Different gradients of potassium fertilizer application were set in the field to conduct potassium nutrition diagnosis during the whole growth period. The petiole was selected as the fifth fully expanded functional leaf from the top. 5 ) and base 1

[0052] petiole of (root1);

[0053] (2) Sampling was carried out at 30, 60, 75, and 90 days after transplanting. Ten plants were selected each time, and the potassium concentration of petioles at each leaf position of 7 plants was measured by a portable potassium ion meter. The difference was calculated. Then 3 plants were taken for withering and drying, and their biomass and potassium content were measured to calculate the potassium absorption of the plants. Yield was measured at the harvest period.

[0054] (3) For sweet potato, the difference between the fifth fully expanded functional leaf and the first petiole at the base is used as the diagnostic site;

[0055] L c =L top5 -L root1

[0056] (4) The horizontal axis is the petiole concentration difference and the vertical axis is the relative yield. The regression equation 1 of petiole potassium concentration difference and relative yield is constructed:

[0057] Y d =aL c 2 +bL c +c;

[0058] Y d Represents the relative output in each period, L c represents the difference in potassium concentration in petiole, and the coefficients of regression equations a, b, and c

[0059] According to regression equation 1, when Y d The maximum value corresponds to the period L c The critical concentration of potassium nutrition diagnosis of petiole concentration difference is L 临界 .

[0060] (4) Correlation analysis was performed on the potassium absorption of plants and the difference in petiole potassium concentration to obtain regression equation 2:

[0061] Y re =a 2 L c 2 +b 2 L c+c 2 ;

[0062] In this formula, Y re is the potassium absorption of the aboveground part, L c represents the difference in potassium concentration in petiole, a 2 , b 2 、c 2 is the coefficient of the regression equation.

[0063] The L obtained from regression equation 1 临界 Substitute into regression equation 2 to get Y th .

[0064] (5) Compare the measured value with the critical petiole potassium concentration to determine the topdressing coefficient:

[0065] α=(Y th -Y re ) / Y th

[0066] Among them, α is the topdressing coefficient, Y th Y is the potassium absorption amount of the plant when the difference of potassium concentration in petiole is the critical value, re The petiole potassium concentration is the measured critical value of potassium absorption by the plant.

[0067] (6) Substitute the above-mentioned topdressing coefficient into the topdressing model to calculate the topdressing amount for this period. The topdressing model is: K = K'*[1+α]

[0068] K is the amount of potassium topdressing during this period, K' is the planned amount of potassium topdressing during this period, and α is the topdressing coefficient.

[0069] Example 2 Clarification of diagnostic site

[0070] 1. Experimental methods

[0071] (1) The experiment was conducted with potassium-deficient nutrient solution (K 0 ), complete nutrient solution (K 1 ), excess potassium nutrient solution (K 2 ) 3 treatments, 5 repetitions. The nutrient solution was based on the modified Hoagland nutrient solution with different potassium ion concentrations. The trace element solution and iron salt solution were kept consistent between different treatments. The variety was Yanshu No. 25.

[0072] (2) The photosynthetic parameters, chlorophyll value, fresh weight of aboveground and underground parts, root morphology and petiole potassium concentration at each leaf position were measured between 9:00 and 11:00 am on the 45th day after transplanting. The correlation between the biological indicators of sweet potato and petiole potassium concentration was also analyzed.

[0073] 2. Experimental results and analysis

[0074] The results of correlation analysis between sweet potato biological indicators and petiole potassium concentration are shown in Tables 1 and Figure 1 As shown in the figure, the results indicate that the difference in potassium concentration between the petiole 5 and the petiole 1 has a very significant correlation with some biological indicators of sweet potato seedlings, showing the same change trend due to the change in potassium application amount.

[0075] Specifically, the stepwise regression analysis of each dependent variable (petiole potassium concentration at different parts and the difference of petiole potassium concentration at different parts) and the independent variables (various sweet potato biological indicators, such as fresh weight, net photosynthetic rate, etc.) was performed, and the regression equation correlation coefficient R between the difference of potassium concentration between the petiole 5 and the petiole 1 and the independent variable (multiple biological indicators) was obtained. 2 The correlation was 0.99, which was significantly better than other groups (based on the potassium concentration of petioles in different parts, or the difference in potassium concentration in other parts, etc.), that is, the diagnostic effect of the difference in potassium concentration between the petiole 5 and the petiole 1 was better than the absolute value of petiole potassium concentration or the difference in other petiole concentrations. Therefore, the difference in potassium concentration between the petiole 5 and the petiole 1 was the most accurate for rapid diagnosis of potassium nutrition in the sweet potato seedling stage. The difference between the two can be used as an indicator for rapid field diagnosis of sweet potato potassium nutrition using a handheld potassium ion meter.

[0076] Table 1 Correlation analysis between biological indicators and petiole potassium concentration in sweet potato seedling stage

[0077]

[0078]

[0079] Note: The units of the biological indicators of sweet potato seedlings are: fresh weight of aboveground part (g), fresh weight of underground part (g), SPAD value, transpiration rate (mol·m -2 ·s -1 )), net photosynthetic rate (μmol·m -2 ·s -1 ), stomatal conductance (mmol·m -2 ·s -1 ), intercellular CO 2 Concentration (μmol·mol -1 ), total root length (cm), root surface area (cm 2 ), root volume (cm 3 ).

[0080] Example 3 Field test to verify the determination of diagnosis position and fertilization model

[0081] (1) A field experiment was conducted on sweet potato with different potassium fertilizer dosages in 2022-2023. The field experiment included five potassium gradient experiments: K0 (0 kg / hm2 2 )、K1(75kg / hm 2)、K2(150kg / hm 2 )、K3(225kg / hm 2 )、K4(300kg / hm 2 ), each treatment was repeated three times in randomized block arrangement, and the experimental variety was Yanshu 25.

[0082] (2) Sampling was conducted throughout the entire growth period. Ten plants were selected each time. Seven plants were selected to use a portable potassium ion meter to quickly measure the potassium concentration in the petioles of each leaf position. The other three plants were dried separately in different parts to measure the biomass and potassium content, and the amount of potassium absorbed by the plants was obtained. Yield was measured at the harvest period.

[0083] (3) The correlation analysis between the petiole concentration difference index of each leaf position during the two-year growth period and the amount of potassium applied was conducted, and it was found that the difference between the petiole of functional leaf 5 and the petiole of basal leaf 1 was significantly positively correlated with the change in the amount of potassium applied, as shown in Table 2 below.

[0084] Table 2 Correlation analysis between different potassium application rates and petiole potassium concentration of sweet potato during the whole growth period

[0085]

[0086] *p≤0.05**p≤0.01***p≤0.001

[0087] (4) The petiole concentration difference index of each leaf position during the two-year growth period was fitted with the quadratic equation of relative yield, and it was found that the potassium ion concentration difference index of the petiole of functional leaf 5 and the petiole of basal leaf 1 had a good correlation with the relative yield. The results are shown in Table 3.

[0088] Table 3 Correlation coefficient R2 between petiole potassium concentration measured rapidly during the whole growth period and relative yield of sweet potato

[0089]

[0090] In summary, pot experiments and field experiments showed that the difference in potassium ion concentration between the petiole of functional leaf 5 and the petiole of basal leaf 1 was the most accurate for rapid diagnosis of potassium nutrition in sweet potato seedlings, and the difference between the two could be used as an indicator for rapid field diagnosis of potassium nutrition in sweet potato using a handheld potassium ion meter.

[0091] (5) Identify the diagnosis site and establish a fertilization model

[0092] First, it is necessary to determine the critical value of the difference in potassium ion concentration between the petiole of the 5th functional leaf and the petiole of the 1st petiole of the base leaf of sweet potato at different stages, and use the critical value to judge whether there is a hidden potassium deficiency. The critical value usually requires yield calculation, and the application of relative yield can eliminate the influence of factors such as soil fertility and environment.

[0093] The relative yield in each period was used to perform quadratic fitting with the potassium ion concentration difference index between the petiole of functional leaf 5 and the petiole of basal leaf 1, and regression equation 1 was obtained. When the relative yield was the largest, the potassium ion concentration difference index of the petiole was the critical value, which was 875ppm, 672ppm, 435ppm and 110ppm in each period, respectively.

[0094] The regression equation 1 for each period is as follows:

[0095] Y 30 =-1.23E-04x 2 +0.2295x-6.29R 2 =0.9983

[0096] Y 60 =-6.58E-04x 2 +0.993x-229.43R 2 =0.9713

[0097] Y 75 =-0.0012x 2 +1.1815x-190.96R 2 =0.9833

[0098] Y 90 =-0.52E-04x 2 +0.2508x+83.15R 2 =0.9153

[0099] (6) The correlation between the potassium absorption of plants in each growth period of the two years and the potassium ion concentration difference index between the petiole of the functional leaf 5 and the petiole of the base leaf 1 reached an extremely significant level, indicating that the function can well reflect the potassium absorption of plants. The regression equation 2 for each period established based on the relationship between the potassium concentration difference between the petiole of the functional leaf 5 and the petiole of the base leaf 1 during the growth period and the potassium absorption of plants is as follows:

[0100] Y re30 =2E-05x 2 -0.1019x+107.45

[0101] Y re60 =-1.75E-04x 2 +0.1246x+105.56

[0102] Y re75 =-0.00105x 2 +0.9932x-117.78

[0103] Y re90 =1.20E-05x 2 -0.1477x+135.40

[0104] (7) The relationship between the potassium application rate and sweet potato yield in the two-year field experiment was fitted by a quadratic equation, and the correlation reached a significant level. The equation is y = -0.1775x 2 +77.159x+35598(R 2 =0.8963). According to the equation, the maximum production is 4.983t / hm 2 The corresponding recommended amount of potassium fertilizer is 197.96 kg / hm 2 .

[0105] (8) Based on the comparison between the measured value and the critical value of petiole potassium concentration, the topdressing coefficient for each period is obtained as follows:

[0106] α 30 =(27.12-Y re ) / 27.12

[0107] α 60 =(110.26-Y re ) / 110.26

[0108] α 75 =(115.56-Y re ) / 115.56

[0109] α 90 =(119.3-Y re ) / 119.3

[0110] (9) Specify the amount of potassium topdressing. According to the different proportions of potassium absorbed by sweet potato plants at different growth stages, the proportion is 39.32% at the branching and tuber stage, 45.36% at the vine and tuber stage, and 15.32% at the tuber expansion stage. Based on the target amount of potassium topdressing, the planned amount of potassium topdressing for each period is as follows:

[0111] K 30 =77.84*[1+(27.12-Y re ) / 27.12]

[0112] K 60 =77.84*[1+(110.26-Y re ) / 110.26]

[0113] K 75 =89.79*[1+(115.56-Y re ) / 115.56]

[0114] K 90 =89.79*[1+(119.3-Y re ) / 119.3].

[0115] Example 4 Verification of fertilization model

[0116] 1. Experimental methods

[0117] The topdressing model obtained by the method of Example 3 was verified in this example. The test site was selected from a sweet potato test plot with similar soil conditions in 2023, and the sweet potato variety planted was Yanshu No. 25. An experimental group and a control group were set up. The experimental group performed potassium nutrition diagnosis of petiole concentration difference 75 days after the sweet potato seedlings were transplanted according to the above scheme. The critical value of petiole potassium concentration difference 75 days after transplanting was 435ppm, and the actual petiole concentration difference was 590ppm. Substitute it into regression equation 2 and Y 75 =-0.00105x 2 +0.9932x-117.78, the critical petiole concentration difference potassium absorption Y after 75 days of transplanting is obtained th , measured petiole concentration difference potassium absorption amount Y re 115.56 kg / hm 2 、102.7kg / hm 2 The potassium topdressing coefficient is 1.11, and the required potassium topdressing amount is 99.67kg / hm 2 , divided into 500m 2 In the topdressing test area, topdressing was carried out; in the control group, 60 kg / hm2 of potassium was applied according to farmers' experience. 2 .

[0118] 2. Experimental results and analysis

[0119] The tobacco and potato yield of the control group using traditional topdressing method was 37.876t / hm 2 The final yield of tobacco and potato in the experimental group using the potassium nutrition diagnosis method of the present application for potassium supplementation was 42.832t / hm 2 Compared with the control group, the yield of tobacco potatoes in the experimental group increased by 11.6%, and the commercial potato rate of tobacco potatoes increased by 16%.

[0120] Effects of different potassium topdressing methods on the commercial quality and yield of Yanshu 25

[0121]

[0122] Different lowercase letters after the data in the same column indicate significant differences among treatments (p<0.05).

[0123] It is understandable that those skilled in the art can make equivalent substitutions or changes based on the technical solution and concept of the present invention, and all these changes or substitutions should fall within the protection scope of the claims attached to the present invention.

Claims

1. A rapid diagnosis method for sweet potato potassium nutrition, characterized in that: The following steps are involved: S1. Set different gradients of potassium fertilizer application in the field to conduct potassium nutrition diagnosis during the whole growth period, and sample petioles with 5 petioles in the opposite direction and 1 petiole in the right direction; S2. Sampling was carried out at 30d, 60d, 75d and 90d after transplanting. Ten plants were taken each time, and their fresh weight was measured to obtain relative yield. The potassium concentration of the petiole 5 and the petiole 1 was measured by taking 7 plants, and the difference was calculated. Three plants were then taken for sterilization and drying, and their biomass and potassium content were measured to calculate the potassium absorption of the plants. S3, sweet potato, the potassium concentration difference between the fifth petiole of the fully expanded functional leaf and the first petiole at the base from the top is used as the petiole potassium concentration difference L of the diagnostic site c ; S4. Fitting is performed with the petiole potassium concentration difference as the horizontal axis and the relative yield as the vertical axis, and a regression equation 1 of the petiole potassium concentration difference and relative yield is constructed: Y d =aL c 2 +bL c +c; In regression equation 1, Y d Represents the relative output in each period, L c represents the difference in potassium concentration in petiole, a, b, c regression equation coefficients; according to regression equation 1, when Y d The period L corresponding to the maximum value c The value is used as the critical concentration for diagnosing potassium nutrition in petiole concentration difference, namely Lc 临界 ; S4. Correlation analysis was performed on the potassium absorption of sweet potato plants and the difference in potassium concentration of sweet potato petioles to obtain regression equation 2: Y re =a2L c 2 +b2L c +c2, In regression equation 2, Y re Indicates the potassium absorption of the aboveground part, L c represents the measured petiole potassium concentration difference, a2, b2, c2 regression equation coefficients; The Lc obtained in regression equation 1 临界 Substitute into regression equation 2 to obtain the potassium absorption amount Y under the critical concentration difference of petiole in this period th ; S5. Compare the measured value with the critical value of petiole potassium concentration to determine the topdressing coefficient α. α=(Y th -Y re ) / Y th , where α is the topdressing coefficient, Y th Y is the potassium absorption amount under the critical concentration difference of petiole during the period, re It is the potassium absorption amount under the actual petiole concentration difference during this period; S6. Substitute the above-mentioned topdressing coefficient into the topdressing model to calculate the amount of topdressing for this period.

2. The sweet potato potassium nutrition rapid diagnosis method according to claim 1, characterized in that: In step S2, the potassium concentration of the petiole 5 in the lower part and the petiole 1 in the middle part was measured using a portable potassium ion meter.

3. The sweet potato potassium nutrition rapid diagnosis method according to claim 1, characterized in that: In step S6, the topdressing model is K=K'*[1+α], where K is the actual topdressing potassium amount in this period, K' is the planned topdressing potassium amount in this period, and α is the topdressing coefficient.

4. The sweet potato potassium nutrition rapid diagnosis method according to claim 1, characterized in that: The regression equation 1 is: Y 30 =-1.23E-04x 2 +0.2295x-6.29,R 2 =0.9983; Y 60 =-6.58E-04x 2 +0.993x-229.43,R 2 =0.9713; Y 75 =-0.0012x 2 +1.1815x-190.96,R 2 =0.9833; Y 90 =-0.52E-04x 2 +0.2508x+83.15,R 2 =0.9153。 5. The sweet potato potassium nutrition rapid diagnosis method according to claim 1, characterized in that: Equation 2 is: <h2 style=";text-align:left;direction:ltr">Y<h2 style=";text-align:left;direction:ltr"> re30 <h2 style=";text-align:left;direction:ltr"> =2E-05x<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> -0.1019x+107.45; Y re60 =-1.75E-04x 2 +0.1246x+105.56; Y re75 =-0.00105x 2 +0.9932x-117.78; AND re90 =1.20E-05x 2 -0.1477x+135.40。 6. The method for rapid diagnosis of sweet potato potassium nutrition according to claim 1, characterized in that: The topdressing coefficient α in each period is: α 30 ＝(27.12-Y re ) / 27.12； α 60 ＝(110.26-Y re ) / 110.26； α 75 ＝(115.56-Y re ) / 115.56； α 90 ＝(119.3-Y re ) / 119.3。 7. The method for rapid diagnosis of sweet potato potassium nutrition according to claim 1, characterized in that: The planned potassium chasing models for each period are: K 30 =77.84*[1+(27.12-Y re ) / 27.12]; K 60 =77.84*[1+(110.26-Y re ) / 110.26]; K 75 =89.79*[1+(115.56-Y re ) / 115.56]; K 90 =89.79*[1+(119.3-Y re ) / 119.3]。

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