An early warning method for water core disease of "Tainong No. 17" pineapple

Abstract

The present invention relates to the field of plant disease prevention and control methods, and specifically discloses an early warning method for "Tainong No. 17" pineapple water core disease, by carrying out differentiated field in-situ tests with different nitrogen dosages, taking plant samples at different growth stages of pineapples to measure and weigh the aboveground biomass of the plants and detecting the nitrogen concentration of the leaves, obtaining the incidence of pineapple water core disease by investigation and calculation during the pineapple maturity period, and constructing a multivariate linear regression equation between the leaf nitrogen concentration at the flowering and red stage and the aboveground biomass of the plants at the fruit development stage and the incidence rate. The multivariate linear regression equation between the leaf nitrogen concentration at the flowering and red stage and the aboveground biomass of the plants at the fruit development stage and the incidence rate constructed by the present invention can effectively warn of pineapple water core disease, and take targeted prevention and control measures for pineapple water core disease in advance.

Description

Technical Field

[0001] The invention relates to the field of plant disease prevention and control methods, and in particular to an early warning method for water core disease of "Tainong 17" pineapple. Background Art

[0002] The pineapple "Tainong No. 17" (Golden Diamond Pineapple) has high yield, unique flavor and high economic value. However, due to soil-climate, fertilization and planting management, this variety has a large area of ​​​​the rupture of the flesh cell wall during the ripening period, the cell loses water and becomes water-soaked, the flesh becomes transparent, the quality decreases and it is not resistant to storage. This is a pineapple physiological disease commonly known as "water core disease".

[0003] Pineapples with water core disease are commonly known as "water pineapples". Compared with normal fruits, the taste and nutritional quality of diseased fruits are significantly reduced. The fruits are not only not resistant to storage, but even inedible and lose their commercial value. At present, the phenomenon of "water pineapples" is common. In years with heavy rain during the harvest period, the incidence of water pineapples in some low-lying plots can be as high as 30%. Pineapple water core disease seriously affects the quality and value of Tainong No. 17 pineapples. It is one of the important issues that restrict the development of the pineapple industry. It is urgent to understand its impact on fruit quality, occurrence mechanism and regulatory measures. Revealing the physiological mechanism of water core disease of "Tainong No. 17" pineapple and proposing targeted prevention and control measures are important issues that need to be solved in order to improve the quality and efficiency of the tropical specialty fruit industry. Pineapples with water core disease lose water due to the breakdown of the stability of the pulp cells, and the intercellular spaces become waterlogged, resulting in the fruit being not resistant to storage. As the disease progresses, it will emit a wine lees smell and an unpleasant odor. Yao Yanli et al. studied the physiological indicators of pineapples with water core disease in Bali and found that the soluble solids content and vitamin C content of water-soaked pineapple fruits decreased significantly, and the decrease increased with the increase in the degree of disease. The soluble solids content and ascorbic acid content of pineapples with moderate water core disease (lesion area > 23%) were 14.2% and 39.5% lower than those of the control, respectively. The total sugar content of pineapples with water core disease also showed a downward trend. The total sugar content of pineapples with moderate water core disease was significantly lower than that of normal fruits, with a decrease of 15.2%. At present, there are few studies on the effects of pineapple water core disease on the physical and chemical properties of plants, and there are relatively few reports on physiological changes related to nutrition and reproductive growth, such as plant dry matter accumulation, nutritional status, and key hormones.

[0004] At present, most of the research on the prevention and control methods of pineapple water core disease is focused on. However, due to the different regions and environments, the incidence of water core disease in different varieties of pineapples varies greatly. If comprehensive prevention and control is carried out, the workload will be large, time-consuming and labor-intensive, and it is difficult to achieve targeted prevention and control. Therefore, establishing an early warning method for pineapple water core disease can prevent and control pineapple water core disease more accurately and in a targeted manner, which is the basis for preventing and controlling pineapple water core disease. Summary of the invention

[0005] In order to establish an early warning method for pineapple water core disease with prevention as the main focus, the present invention provides an early warning method for "Tainong No. 17" pineapple water core disease. The multivariate linear regression equation between the nitrogen concentration and biomass and the incidence rate constructed by the present invention can effectively warn of the pineapple water core disease, and take targeted prevention and control measures for the pineapple water core disease in advance.

[0006] The present invention provides an early warning method for water core disease of "Tainong No. 17" pineapple, comprising the following steps:

[0007] The experimental plots with similar environment were selected to plant "Tainong No. 17" pineapple. Different amounts of nitrogen fertilizer were applied during the non-growing period of the pineapple. Then plant samples were taken at different growth periods of the pineapple plants. The aboveground biomass of the plants was weighed and the nitrogen concentration of the leaves was tested. The incidence of pineapple water core disease was investigated during the pineapple maturity period.

[0008] The multivariate linear regression equation between the leaf nitrogen concentration in the flowering and red stage of pineapple and the aboveground biomass of the plant in the fruit development stage and the incidence of pineapple water core disease was constructed. The regression equation was used to express the relationship between the leaf nitrogen concentration and the aboveground biomass of the plant and the incidence of pineapple water core disease.

[0009] By detecting the nitrogen concentration of leaves during the flowering and reddening period and the aboveground biomass of plants during the fruit development period and substituting them into the multivariate linear regression equation, the incidence of pineapple water core disease can be warned.

[0010] Furthermore, the pineapple growth period includes: before planting, slow growth period, early rapid growth period, late rapid growth period and flowering and reddening period, fruit development period, and fruit ripening period.

[0011] Furthermore, the nitrogen fertilizer treatment includes 6 treatment groups:

[0012] ①LowOptT means: the nitrogen application amount is 30% lower than the reasonable supply mass percentage, and is applied to pineapples at different growth stages according to a reasonable distribution ratio;

[0013] ②LowConT means: nitrogen application is 30% lower than the reasonable supply mass percentage and is applied to pineapples at different growth stages according to farmers’ conventional allocation ratio;

[0014] ③BalOptT means: nitrogen application is reasonably supplied and applied to pineapple at different growth stages according to a reasonable distribution ratio;

[0015] ④BalconT means: Nitrogen application is reasonably supplied and applied to pineapples at different growth stages according to the farmers' conventional allocation ratio;

[0016] ⑤HighOptT means: the nitrogen application amount is 30% higher than the reasonable supply mass percentage, and is applied to pineapple at different growth stages according to the reasonable distribution ratio;

[0017] ⑥HighConT means: the nitrogen application rate is 30% higher than the reasonable supply mass percentage, and it is applied to pineapples at different growth stages according to the farmers' conventional allocation ratio;

[0018] The reasonable supply is 450-500kg / hm2 of nitrogen. 2 ;

[0019] The conventional allocation ratio of farmers is 38-40:12:12:12:12:12:12 before planting, slow growth period, early rapid growth period, late rapid growth period, flowering and red stage, and fruit development period;

[0020] The reasonable distribution ratio is 38-40:13:16:18:9:4 for nitrogen application before planting, slow growth period, early rapid growth period, late rapid growth period, flowering and red stage, and fruit development period respectively.

[0021] Furthermore, farmers' routine allocation indicated that the nitrogen application ratios before planting, slow growth period, early rapid growth period, late rapid growth period, flowering and red stage, and fruit development period were 40:12:12:12:12:12 respectively.

[0022] Furthermore, reasonable allocation means that the nitrogen application ratio before planting, slow growth period, early rapid growth period, late rapid growth period, flowering and red stage, and fruit development period is 40:13:16:18:9:4 respectively.

[0023] Furthermore, the aboveground biomass of the plant is determined by collecting the aboveground parts of the pineapple plant, washing them, drying them, and weighing their fresh weight.

[0024] Furthermore, the leaf nitrogen concentration during the flowering and reddening period and the aboveground biomass of the plant during the fruit development period were selected to establish a multiple linear regression equation between the leaf nitrogen concentration and the aboveground biomass of the plant and the incidence rate; the slow growth period and the rapid growth period belong to the vegetative growth of pineapple plants, and the flowering and reddening period, the fruit development period and the fruit maturity period belong to the reproductive growth of pineapple plants. The flowering and reddening period and the fruit development period are the key nodes for the pineapple plant to switch from vegetative growth to reproductive growth. Therefore, the leaf nitrogen concentration during the flowering and reddening period and the aboveground biomass of the plant during the fruit development period were selected to establish a multiple linear regression equation between the leaf nitrogen concentration and the aboveground biomass of the plant and the incidence rate.

[0025] Furthermore, the multivariate linear regression equation between the leaf nitrogen concentration, plant aboveground biomass and disease incidence is as follows:

[0026] Y = 4.019X1 + 0.018X2 - 86.028;

[0027] Y is the incidence rate of water core disorder, X1 is the nitrogen concentration in leaves during the red emergence stage of flower forcing, and X2 is the above-ground biomass of the plant during the fruit development period. When the nitrogen concentration in leaves during the red emergence stage of flower forcing is 9.5 - 12 g / kg and the above-ground biomass of the plant during the fruit development period is 2700 - 3200 g, it is a low-risk warning; when the nitrogen concentration in leaves during the red emergence stage of flower forcing is 9.5 - 12 g / kg and the above-ground biomass of the plant during the fruit development period is 3300 - 3900 g, it is a medium-risk warning; when the nitrogen concentration in leaves during the red emergence stage of flower forcing is 9.5 - 12 g / kg and the above-ground biomass of the plant during the fruit development period is more than 4000 g, it is a high-risk warning. Further, the risk classification of water core disorder is as follows: when the incidence of water core disorder is 0 < Y < 10% it is a low risk, 10% < Y < 30% it is a medium risk, and Y > 30% it is a high risk. When the nitrogen concentration in leaves during the red emergence stage of flower forcing is 9.5 - 12 g / kg and the above-ground biomass of the plant during the fruit development period is 2700 - 3200 g, it is a low-risk warning; when the nitrogen concentration in leaves during the red emergence stage of flower forcing is 9.5 - 12 g / kg and the above-ground biomass of the plant during the fruit development period is 3300 - 3900 g, it is a medium-risk warning; when the nitrogen concentration in leaves during the red emergence stage of flower forcing is 9.5 - 12 g / kg and the above-ground biomass of the plant during the fruit development period is more than 4000 g, it is a high-risk warning. Further, when warning for varieties other than 'Tainong No. 17' pineapple, first obtain the multiple linear regression equation between the nitrogen concentration in leaves during the red emergence stage of flower forcing, the above-ground biomass of the plant during the fruit development period and the incidence rate according to the above fertilization method and experimental steps, and then use the equation to warn the incidence rate in different regions for easy prevention and control; for 'Tainong No. 17' pineapple, the multiple linear regression equation between the obtained nitrogen concentration, biomass and incidence rate can be directly used to calculate the incidence rate by detecting the nitrogen concentration in leaves during the red emergence stage of flower forcing and the above-ground biomass of the plant during the fruit development period, so as to warn the occurrence of water core disorder in 'Tainong No. 17' pineapple and achieve the effect of early prevention and control; when obtaining a warning for the incidence rate of water core disorder in an unknown planting area of 'Tainong No. 17' pineapple, detect the nitrogen concentration in leaves during the red emergence stage of flower forcing of the pineapple and the above-ground biomass during the fruit development period and substitute them into the above multiple linear regression equation to calculate the incidence rate.

[0028] The present invention also provides an application of a multiple linear regression equation model in predicting the incidence rate of water core disorder in 'Tainong No. 17' pineapple. The multiple linear regression equation model is the multiple linear regression equation for predicting water core disorder in 'Tainong No. 17' pineapple obtained by the above method: Y = 4.019X1 + 0.018X2 - 86.028; Y is the incidence rate of water core disorder, X1 is the nitrogen concentration in leaves during the red emergence stage of flower forcing, and X2 is the above-ground biomass of the plant during the fruit development period;

[0029] When the incidence of heart rot is 0 < Y < 10%, it is a low risk; when 10% < Y < 30%, it is a medium risk; when Y > 30%, it is a high risk. When the nitrogen concentration in the leaves during the red bud stage of flower forcing is 9.5 - 12 g / kg and the above-ground biomass of the plant during the fruit development period is 2700 - 3200 g, it is a low-risk warning; when the nitrogen concentration in the leaves during the red bud stage of flower forcing is 9.5 - 12 g / kg and the above-ground biomass of the plant during the fruit development period is 3300 - 3900 g, it is a medium-risk warning; when the nitrogen concentration in the leaves during the red bud stage of flower forcing is 9.5 - 12 g / kg and the above-ground biomass of the plant during the fruit development period is more than 4000 g, it is a high-risk warning.

[0030] Further, the steps for predicting the incidence of heart rot in "Tainong No. 17" pineapple are as follows:

[0031] Collect the leaves of "Tainong No. 17" pineapple during the red bud stage of flower forcing and detect the nitrogen concentration;

[0032] Collect the plants of "Tainong No. 17" pineapple during the fruit development period and detect the above-ground biomass;

[0033] Substitute the nitrogen concentration in the leaves and the above-ground biomass into the multiple linear regression equation Y = 4.019X1 + 0.018X2 - 86.028, where Y is the incidence of heart rot, X1 is the nitrogen concentration in the leaves during the red bud stage of flower forcing, and X2 is the above-ground biomass of the plant during the fruit development period;

[0034] Judge the risk level: When the incidence of heart rot is 0 < Y < 10%, it is a low risk; when 10% < Y < 30%, it is a medium risk; when Y > 30%, it is a high risk. When the nitrogen concentration in the leaves during the red bud stage of flower forcing is 9.5 - 12 g / kg and the above-ground biomass of the plant during the fruit development period is 2700 - 3200 g, it is a low-risk warning; when the nitrogen concentration in the leaves during the red bud stage of flower forcing is 9.5 - 12 g / kg and the above-ground biomass of the plant during the fruit development period is 3300 - 3900 g, it is a medium-risk warning; when the nitrogen concentration in the leaves during the red bud stage of flower forcing is 9.5 - 12 g / kg and the above-ground biomass of the plant during the fruit development period is more than 4000 g, it is a high-risk warning.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] 1. Through setting up different nitrogen fertilizer application experiments, the present invention has established a multiple linear regression equation between the nitrogen concentration in pineapple leaves, the above-ground biomass of the plant and the incidence rate, that is, Y = 4.019X1 + 0.018X2 - 86.028, where Y is the incidence rate of heart rot disease, X1 is the nitrogen concentration in leaves at the red appearance stage of flower forcing, and X2 is the above-ground biomass of the plant during the fruit development period; when the incidence rate of heart rot disease is 0 < Y < 10% it is a low risk, 10% < Y < 30% is a medium risk, and Y > 30% is a high risk; when the nitrogen concentration in leaves at the red appearance stage of flower forcing is 9.5 - 12 g / kg and the above-ground biomass of the plant during the fruit development period is 2700 - 3200 g, it is a low-risk warning; when the nitrogen concentration in leaves at the red appearance stage of flower forcing is 9.5 - 12 g / kg and the above-ground biomass of the plant during the fruit development period is 3300 - 3900 g, it is a medium-risk warning; when the nitrogen concentration in leaves at the red appearance stage of flower forcing is 9.5 - 12 g / kg and the above-ground biomass of the plant during the fruit development period is more than 4000 g, it is a high-risk warning. It can effectively give an early warning of pineapple heart rot disease and take targeted prevention and control measures against the heart rot disease of "Tainong No. 17" pineapple in advance. Detailed implementation manners

[0037] The following will describe the detailed implementation manners of the present invention in detail, but it should be understood that the protection scope of the present invention is not limited by the detailed implementation manners. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention. The experimental methods described in the embodiments of the present invention are all conventional methods unless otherwise specified, and the materials, reagents, etc. used in the following embodiments can be obtained from commercial channels unless otherwise specified.

[0038] The present invention provides a method for early warning of heart rot disease of "Tainong No. 17" pineapple.

[0039] Select experimental plots with similar environments to plant pineapples, apply different amounts of nitrogen fertilizers during different non-growing periods of pineapples respectively, then take plant samples at different growth stages of pineapple plants, detect the nitrogen concentration in leaves at the red appearance stage of flower forcing, weigh the above-ground biomass of the plant during the fruit development period, and at the same time obtain the incidence rate of pineapple heart rot disease through investigation and calculation;

[0040] Then construct a multiple linear regression equation between the nitrogen concentration in leaves at the red appearance stage of flower forcing, the above-ground biomass during the fruit development period and the incidence rate. The regression equation is used to represent the relationship between the nitrogen concentration in leaves at the red appearance stage of flower forcing, the above-ground biomass of the plant during the fruit development period and the incidence rate; then by substituting the detected nitrogen concentration in leaves at the red appearance stage of flower forcing and the above-ground biomass of the plant during the fruit development period of pineapples into the multiple linear regression equation, the incidence rate can be warned.

[0041] The obtained multiple linear regression equation can directly predict the incidence of heart rot disease of "Tainong No. 17" pineapple of the same variety in the same area.

[0042] If the incidence of pineapple water core disease in different regions and varieties is to be identified, it is necessary to obtain the corresponding multivariate linear regression equation after fertilization according to the method in this application, and then predict the incidence of pineapple water core disease.

[0043] Example 1: Effects of nitrogen and biomass on the incidence of water core disease in "Tainong No. 17" pineapple.

[0044] 1. Experimental Materials

[0045] 1. Fertilizer: urea (N46%), potassium dihydrogen phosphate (P2O5 52%, K2O 34%), potassium sulfate (K2O52%);

[0046] The organic fertilizer was commercial sheep manure organic fertilizer (N 1.84%, P 1.10%, K 2.94%, pH 6.9, organic matter 49%) purchased from Shandong Rongda Biological Fertilizer Co., Ltd.

[0047] 2. Pineapple variety: Tainong No. 17.

[0048] 2. Experimental Methods

[0049] 1. Pineapple planting and nitrogen fertilizer treatment methods

[0050] The test site is located in Longyue Village, Bohou Town, Lingao County, Haikou City, Hainan Province, in the science and technology courtyard jointly built by Hainan University and Hainan Tiandiren Ecological Agriculture Co., Ltd. The area is located in the tropical monsoon climate zone, with a climate suitable for crop growth, abundant rain and heat, and high accumulated temperature. The average annual temperature is 24-25℃, the average annual rainfall is 1280mm, and the annual evaporation is 2-2.5 times the rainfall. The heat is abundant, the rainfall is abundant, and the dry and rainy seasons are distinct. The soil at the test site is basalt brick red soil, with a pH value of 5.71 and an organic matter content of 29.03g·kg -1 , soil total nitrogen content 246.47 mg kg -1 , available phosphorus content 476.19 mg kg -1 , fast-acting potassium content 138.79 mg kg -1 , exchangeable calcium 352.63 mg kg -1 , exchangeable magnesium 104.28 mg kg -1 .

[0051] The experiment was repeated three times, with a total of 18 plots randomly arranged, each plot was 86 square meters, the planting specifications were 33cm×50cm×130cm, double-row planting, 3,000 plants per mu, and the experimental area was about 2.4 mu.

[0052] Pineapples were planted on September 22, 2021 (soil was turned and land was prepared before planting), flowered on August 5, 2022, and harvested at the end of December 2022. According to the amount and period of nitrogen application, a total of 6 treatments were designed in the experiment: ①LowOptT, ②LowConT, ③BalOptT, ④BalconT, ⑤HighOptT, ⑥HighConT.

[0053] ①LowOptT means: nitrogen application rate is 315kg / hm 2 (30% lower than the reasonable supply), apply nitrogen in a ratio of 40:13:16:18:9:4 (reasonable distribution) before planting (basal fertilizer), slow growth period, early rapid growth period, late rapid growth period, flowering and red stage, and fruit development period;

[0054] ②LowConT means: nitrogen application rate is 315kg / hm 2 (30% lower than the reasonable supply), apply nitrogen in a ratio of 40:12:12:12:12:12:12 before planting (basal fertilizer), slow growth period, early rapid growth period, late rapid growth period, flowering and red stage, and fruit development period (routine distribution by farmers);

[0055] ③BalOptT means: nitrogen application rate is 450kg / hm 2 (Reasonable supply), apply nitrogen in a ratio of 40:13:16:18:9:4 before planting (basal fertilizer), slow growth period, early rapid growth period, late rapid growth period, flowering and red stage, and fruit development period (reasonable distribution);

[0056] ④BalconT means: nitrogen application rate is 450kg / hm 2 (Reasonable supply), according to the nitrogen application ratio of 40:12:12:12:12:12:12 before planting (basal fertilizer), slow growth period, early rapid growth period, late rapid growth period, flowering and red stage, and fruit development period (routine distribution by farmers);

[0057] ⑤HighOptT means: nitrogen application rate is 585kg / hm 2 (30% higher than the reasonable supply), apply nitrogen in a ratio of 40:13:16:18:9:4 (reasonable distribution) before planting (basal fertilizer), slow growth period, early rapid growth period, late rapid growth period, flowering and red stage, and fruit development period;

[0058] ⑥HighConT means: nitrogen application amount is 585kg / hm 2(30% higher than the reasonable supply), apply nitrogen in a ratio of 40:12:12:12:12:12:12 before planting (basal fertilizer), slow growth period, early rapid growth period, late rapid growth period, flowering and red stage, and fruit development period (conventional distribution for farmers);

[0059] The conventional allocation (ConT) of farmers means that the nitrogen application ratio is 40:12:12:12:12:12:12 before planting (basal fertilizer), slow growth period, early rapid growth period, late rapid growth period, flowering and red stage, and fruit development period;

[0060] Reasonable allocation (OptT) means that the nitrogen application ratio before planting (basal fertilizer application), slow growth period, early rapid growth period, late rapid growth period, flowering and red stage, and fruit development period is 40:13:16:18:9:4 respectively.

[0061] The potassium and phosphorus dosages in the above six treatments were kept the same, with the phosphorus dosage being 160 kg / hm2. 2 , potassium dosage is 720kg / hm 2 The experiment was repeated three times, with a total of 18 plots randomly arranged, each plot was 86 square meters. The planting specifications were 33cm×50cm×130cm, double-row planting, 3,000 plants per mu, and the experimental area was about 2.4 mu. Organic fertilizer was applied as a base fertilizer at one time, and topdressing fertilizer was applied in the later stage with water and fertilizer. The amount and time of fertilizer application are shown in Tables 1 and 2 below.

[0062] Table 1 Fertilization settings for pineapple at different stages

[0063]

[0064] The following fertilizer dosage is based on 86m 2 Calculated by plot area, weight is Kg. Organic fertilizer is applied during the planting period, urea is applied during the slow growth period to supplement nitrogen, potassium dihydrogen phosphate is applied to supplement phosphorus, and potassium sulfate is applied to supplement potassium. Urea and potassium sulfate are applied as water fertilizer in the early rapid growth period, the late rapid growth period, the flowering and red stage, and the fruit development period to supplement nitrogen and potassium.

[0065] Table 2 Fertilizer application amount at different periods

[0066]

[0067]

[0068] 2. Effects of nitrogen fertilizer treatment at different stages on the biomass of “Tainong No. 17” pineapple plants

[0069] Plant samples were taken at five important growth stages of pineapple plants and the plants were weighed to obtain the biomass of the plants, as follows:

[0070] At 110 days (slow growth period), 238 days (rapid growth period), 318 days (flowering and red stage), 402 days (fruit development period), and 463 days (fruit maturity period) after planting, the above-ground parts of pineapple plants were collected, the plants were separated, washed, wiped clean, dried, weighed fresh weight, mixed samples were taken from various parts, and the biomass size was recorded. The plants were fixed in a constant temperature drying oven at 105°C for 30 minutes, and then dried to constant weight at a constant temperature of 75°C. The nitrogen concentration of the plant dry samples was determined, digested with H2SO4-H2O2, and the total content was determined by Nessler colorimetry. The dry matter weight of each part was weighed to convert the dry matter accumulation of each physiological part of the plant. The samples were crushed according to the above-ground part and the fruit, and then put into sealed bags for testing.

[0071] The nitrogen in the plant samples was digested with H2SO4-H2O2 and the total nitrogen concentration was determined by the Nessler colorimetric method.

[0072] 3. Detect the incidence of plants after different nitrogen fertilizer treatments

[0073] During the fruit ripening period, 100 pineapple fruits are randomly selected and tested by quality inspectors at the packaging site. The number of diseased fruits is recorded and the total amount of fruits is as large as possible, which can better avoid randomness in the data.

[0074] The calculation formula for the incidence of fruit water core disease is as follows:

[0075] Water core disease incidence = incidence / sample size*100%

[0076] 4. Analysis of the relationship between nitrogen concentration, biomass and incidence

[0077] From the fertilization situation, we can see that 95% of the nitrogen fertilizer is applied before the flowering and redning period, and the amount of nitrogen fertilizer applied in the later period is less. The nitrogen accumulated in the stems and leaves of the plants mainly comes from the nitrogen fertilizer in the early stage. The source of nitrogen in the fruiting period is mainly the nitrogen accumulated by the plants in the early stage. The leaf nitrogen concentration measured during the flowering and redning period is too high, so there will be more time to regulate the nitrogen usage in the later period, and it must be warned before the fruit matures to have warning significance.

[0078] The slow growth period and the rapid growth period belong to the vegetative growth of pineapple plants; the flowering and red stage, fruit development stage and fruit maturity stage belong to the reproductive growth of pineapple plants. Therefore, the nitrogen concentration of pineapples in the flowering and red stage, which is the key node of the transition from vegetative growth to reproductive growth, and the biomass in the fruit development stage were selected to establish an early warning equation. The nitrogen concentration of the leaves of pineapple plants in the flowering and red stage and the biomass in the fruit development stage were selected to establish a multivariate linear regression equation in SPSS.

[0079] 3. Experimental Results

[0080] 1. Effects of nitrogen fertilizer treatment at different stages on the biomass of “Tainong No. 17” pineapple plants

[0081] After nitrogen fertilizer treatment, plant samples were collected from pineapple plants at five important growth periods to detect biomass.

[0082] The biomass of pineapple plants at different stages is shown in Table 3.

[0083] Table 3 Biomass test results of pineapple plants at different growth stages

[0084]

[0085] 2. Effects of nitrogen fertilizer treatments at different stages on nitrogen concentration in leaves of “Tainong No. 17” pineapple

[0086] After nitrogen fertilizer treatment, plant samples were collected at five important growth periods of pineapple plants to detect leaf nitrogen concentrations. The nitrogen concentrations of plants at different periods are shown in Table 4.

[0087] Table 4 Results of leaf nitrogen concentration test at different growth stages of pineapple plants

[0088]

[0089]

[0090] 3. Effect of nitrogen application rate on the incidence of water core disease in pineapple variety “Tainong No. 17”

[0091] The effect of nitrogen application rate on the incidence of water core disease in "Tainong No. 17" pineapple is shown in Table 5. Among them, the incidence of pineapple water core disease in the LowOptT treatment was the lowest, at 2.4%, and the incidence of pineapple water core disease in the HighConT treatment was the highest, at 21.4%. The higher the nitrogen application rate, the higher the incidence of pineapple water core disease; therefore, the incidence of pineapple water core disease can be reduced by optimizing the fertilization treatment.

[0092] Table 5 Effect of nitrogen fertilizer on the incidence of water core disease in pineapple "Tainong No. 17"

[0093] Serial number deal with Sample size Diseased fruit Incidence (%) 1 LowOptT 125 3 2.4 2 LowConT 129 4 3.1 3 BalOptT 138 8 5.8 4 BalConT 122 14 11.5 5 HighOptT 125 19 15.2 6 HighConT 126 27 21.4

[0094] The above results show that the best fertilization method to reduce the incidence of water core disease of "Tainong No. 17" pineapple is as follows: nitrogen application rate ≤ 450kg / hm2 during the entire growth period of "Tainong No. 17" pineapple 2 , the amount of nitrogen applied in the late red stage is less than 5% of the entire growth cycle. Apply 40% organic fertilizer before planting, 13% nitrogen fertilizer in the slow growth stage, 16% nitrogen fertilizer in the early stage of rapid growth, 18% nitrogen fertilizer in the late stage of rapid growth, 9% nitrogen fertilizer in the stage of inducing flowers to turn red, and 4% nitrogen fertilizer in the fruit development stage.

[0095] It should be noted that generally, the slow growth period is from 0 to 155 days, the early rapid growth period is from 156 to 246 days, the late rapid growth period is from 247 to 306 days, the red appearance period is from 307 to 337 days, the fruit development period is from 388 to 462 days, and the fruit maturity period is from 463 to 500 days.

[0096] In summary, during the entire growth cycle of Tainong No. 17 pineapple, the nitrogen application rate ≤ 450 kg / hm 2 , the nitrogen application rate in the late stage of red appearance is less than 5% of the entire growth cycle. The nitrogen concentration in the plants during the flower induction and red appearance period should ≤ 8.56 g / kg, and the plant biomass during the fruit development period should ≤ 3.33 kg. Apply 40% of organic fertilizer before planting, 13% of nitrogen fertilizer during the slow growth period, 16% of nitrogen fertilizer during the early rapid growth period, 18% of nitrogen fertilizer during the late rapid growth period, 9% of nitrogen fertilizer during the flower induction and red appearance period, and 4% of nitrogen fertilizer during the fruit development period.

[0097] 4. Analysis of the relationship between leaf nitrogen concentration, above-ground plant biomass and incidence

[0098] The slow growth period and the rapid growth period belong to the vegetative growth of pineapple plants; the flower induction and red appearance period, the fruit development period and the fruit maturity period belong to the reproductive growth of pineapple plants. Therefore, select the leaf nitrogen concentration during the flower induction and red appearance period, which is the key node for the conversion of pineapple plants from vegetative growth to reproductive growth, and the above-ground plant biomass during the fruit development period to establish an early warning equation. Select the leaf nitrogen concentration during the flower induction and red appearance period of pineapple plants and the above-ground plant biomass during the fruit development period to establish a multiple linear regression equation in spss. The significance P < 0.005, reaching a significant level. The specific calculation formula for the occurrence of heart rot in Tainong No. 17 pineapple is:

[0099] Y = 4.019X1 + 0.018X2 - 86.028

[0100] Y is the incidence of heart rot, X1 is the leaf nitrogen concentration during the flower induction and red appearance period, and X2 is the above-ground plant biomass during the fruit development period

[0101] When the incidence of heart rot is 0 < Y < 10% for low risk, 10% < Y < 30% for medium risk, and Y > 30% for high risk. When the leaf nitrogen concentration during the flower induction and red appearance period is 9.5 - 12 g / kg and the above-ground plant biomass during the fruit development period is 2700 - 3200 g, it is a low-risk early warning; when the leaf nitrogen concentration during the flower induction and red appearance period is 9.5 - 12 g / kg and the above-ground plant biomass during the fruit development period is 3300 - 3900 g, it is a medium-risk early warning; when the leaf nitrogen concentration during the flower induction and red appearance period is 9.5 - 12 g / kg and the above-ground plant biomass during the fruit development period is more than 4000 g, it is a high-risk early warning.

[0102] This formula is used to warn of pineapple water core disease during the growth period after the pineapple blooms and turns red.

[0103] The specific calculation process of the above formula is shown in Table 6 and Table 7 below:

[0104] Table 6 Summary of prediction models

[0105]

[0106] Table 7 Prediction model coefficients

[0107]

[0108]

[0109] Example 2: Using the equation constructed in Example 1, an early warning is provided for the incidence rate in unknown pineapple growing areas.

[0110] 1. Experimental Methods

[0111] 1. Randomly select pineapples planted in a plot (the same area as the test plot in Example 1), measure the nitrogen concentration of the plants in the flowering and red stage and the fresh weight of the plants in the fruit development stage, and bring the obtained data into the early warning formula.

[0112] ① Optimized management: The current recommended nutrient management strategy is a total nitrogen application rate of 450 kg / ha;

[0113] ②20M: 20% organic substitution + 80% slow-release nitrogen fertilizer, the total nitrogen application rate is 450kg / ha;

[0114] ③60M: 60% organic substitution + 40% slow-release nitrogen fertilizer, the total nitrogen application amount is 450kg / ha.

[0115] The chemical fertilizers used in this experiment include: urea (N: 46%), potassium dihydrogen phosphate, potassium sulfate; the organic fertilizer (organic alternative) used is commercial sheep manure organic fertilizer, with nitrogen content: 1.84%, phosphorus content: 1.10%, potassium content: 2.94%, pH 6.9, organic matter 49%, provided by Shandong Rongda Biofertilizer Co., Ltd. The controlled-release nitrogen fertilizer used in the experiment is polyurethane-coated controlled-release urea (nitrogen content 42%), with a controlled-release period of ≥120 days, which can meet the nitrogen demand of pineapple throughout its growth period, and is provided by Hubei Xinyangfeng Agricultural Science and Technology Co., Ltd.

[0116] Table 8 Verification plot fertilization plan

[0117]

[0118] 2. Experimental Results

[0119] Measure the nitrogen concentration during the flower forcing and red appearance stage and the plant biomass during the fruit development stage. At the fruit maturity stage, measure the water uptake rate of the pineapple fruits in the above three plots. To ensure the accuracy of the data, randomly select the mature fruits in the plots and repeat the sampling three times. Substitute the data into the multiple linear regression model to verify the accuracy of the model. From Table 9, there is no significant difference between the incidence rate of the prediction model and the actual incidence rate.

[0120] Table 9 Verification of the actual incidence rate and the predicted incidence rate in the plots

[0121]

[0122] Example 3: Use the equation constructed in Example 1 to give an early warning of the incidence rate in an unknown pineapple planting area.

[0123] Randomly select a pineapple planting area in the same region as the test plot in Example 1. According to the method in Example 1, collect and detect the nitrogen concentration of the pineapple plants during the flower forcing and red appearance stage and the plant biomass during the fruit development stage. Then substitute into the multiple linear regression equation in Example 1 to calculate the predicted incidence rate and record it in Table 10. Compare the accuracy of the predicted incidence rate.

[0124] Y = 4.019X1 + 0.018X2 - 86.028

[0125] Y is the incidence rate of internal browning, X1 is the nitrogen concentration in the leaves during the flower forcing and red appearance stage, and X2 is the above-ground biomass of the plant during the fruit development stage

[0126] When the incidence rate of internal browning is 0 < Y < 10%, it is a low risk; when 10% < Y < 30%, it is a medium risk; when Y > 30%, it is a high risk. When the nitrogen concentration in the leaves during the flower forcing and red appearance stage is 9.5 - 12 g / kg and the above-ground biomass of the plant during the fruit development stage is 2700 - 3200 g, it is a low-risk early warning; when the nitrogen concentration in the leaves during the flower forcing and red appearance stage is 9.5 - 12 g / kg and the above-ground biomass of the plant during the fruit development stage is 3300 - 3900 g, it is a medium-risk early warning; when the nitrogen concentration in the leaves during the flower forcing and red appearance stage is 9.5 - 12 g / kg and the above-ground biomass of the plant during the fruit development stage is more than 4000 g, it is a high-risk early warning.

[0127] Table 10 The actual incidence rate and the predicted incidence rate in the pineapple planting area in Example 3

[0128] Grouping Nitrogen concentration Biomass (g) Number of diseased fruits Total number Actual incidence rate (%) Predicted incidence (%) Example 3 11.3 2678.3 2 32 6.25 7.39

[0129] Example 4: Effects of nitrogen and biomass on the incidence of internal browning in 'Tainong No. 17' pineapples.

[0130] I. Experimental materials

[0131] 1. Fertilizer: urea (N46%), potassium dihydrogen phosphate (P2O5 52%, K2O 34%), potassium sulfate (K2O52%);

[0132] The organic fertilizer was commercial sheep manure organic fertilizer (N 1.84%, P 1.10%, K 2.94%, pH 6.9, organic matter 49%) purchased from Shandong Rongda Biological Fertilizer Co., Ltd.

[0133] 2. Pineapple variety: Tainong No. 17.

[0134] 2. Experimental Methods

[0135] 1. Pineapple planting and nitrogen fertilizer treatment methods

[0136] The test site is located in Longyue Village, Bohou Town, Lingao County, Haikou City, Hainan Province, in the science and technology courtyard jointly built by Hainan University and Hainan Tiandiren Ecological Agriculture Co., Ltd. The area is located in the tropical monsoon climate zone, with a climate suitable for crop growth, abundant rain and heat, and high accumulated temperature. The average annual temperature is 24-25℃, the average annual rainfall is 1280mm, and the annual evaporation is 2-2.5 times the rainfall. The heat is abundant, the rainfall is abundant, and the dry and rainy seasons are distinct. The soil at the test site is basalt brick red soil, with a pH value of 5.71 and an organic matter content of 29.03g·kg -1 , soil total nitrogen content 246.47 mg kg -1 , available phosphorus content 476.19 mg kg -1 , fast-acting potassium content 138.79 mg kg -1 , exchangeable calcium 352.63 mg kg -1 , exchangeable magnesium 104.28 mg kg -1 .

[0137] The experiment was repeated three times, with a total of 18 plots randomly arranged, each plot was 86 square meters, the planting specifications were 33cm×50cm×130cm, double-row planting, 3,000 plants per mu, and the experimental area was about 2.4 mu.

[0138] Pineapples were planted on September 22, 2021 (soil was turned and land was prepared before planting), flowered on August 5, 2022, and harvested at the end of December 2022. According to the amount and period of nitrogen application, a total of 6 treatments were designed in the experiment: ①LowOptT, ②LowConT, ③BalOptT, ④BalconT, ⑤HighOptT, ⑥HighConT.

[0139] ①LowOptT means: nitrogen application 315kg / hm 2 (30% lower than reasonable supply), reasonable allocation;

[0140] ②LowConT means: nitrogen application 315kg / hm2 (30% lower than the reasonable supply), regular distribution to farmers;

[0141] ③BalOptT means: nitrogen application 450kg / hm 2 (reasonable supply), reasonable distribution;

[0142] ④BalconT means: nitrogen application 450kg / hm 2 (reasonable supply), regular distribution to farmers;

[0143] ⑤HighOptT means: nitrogen application 585kg / hm 2 (30% higher than reasonable supply), reasonable distribution;

[0144] ⑥HighConT means: nitrogen application 585kg / hm 2 (30% higher than the reasonable supply), regular distribution to farmers;

[0145] The conventional allocation (ConT) of farmers means that the nitrogen application ratios are 38:12:12:12:12:12:12 before planting (basal fertilizer), slow growth period, early rapid growth period, late rapid growth period, flowering and red stage, and fruit development period, respectively;

[0146] Reasonable allocation (OptT) means that the nitrogen application ratios before planting (basal fertilizer application), slow growth period, early rapid growth period, late rapid growth period, flowering and red stage, and fruit development period are 38:13:16:18:9:4 respectively.

[0147] The potassium and phosphorus dosages in the above six treatments were kept the same, with the phosphorus dosage being 160 kg / hm2. 2 , potassium dosage is 720kg / hm 2 The experiment was repeated three times, with a total of 18 plots randomly arranged, each plot was 86 square meters. The planting specifications were 33cm×50cm×130cm, double-row planting, 3,000 plants per mu, and the experimental area was about 2.4 mu. Organic fertilizer was applied as a base fertilizer at one time, and fertilizer was applied later in the form of water and fertilizer.

[0148] 2. Take plant samples at five important growth stages of pineapple plants and weigh the plants to obtain the biomass of the plants, as follows:

[0149] At 110 days (slow growth period), 238 days (rapid growth period), 318 days (flowering and reddening period), 402 days (fruit development period), and 463 days (fruit maturity period) after planting, the plants were separated, washed, wiped clean, dried, weighed fresh weight, and mixed samples were taken from various parts to record their biomass. The plants were fixed in a constant temperature drying oven at 105°C for 30 minutes, and then dried to constant weight at a constant temperature of 75°C. The nitrogen concentration of the dry samples of the plants was determined, and the samples were digested with H2SO4-H2O2 and the total content was determined by the Nessler colorimetric method. The dry matter weight of each part was weighed to convert the dry matter accumulation of each physiological part of the plant. The samples were crushed according to the aboveground part and the fruit, and then put into sealed bags for testing.

[0150] The nitrogen in the plant samples was digested with H2SO4-H2O2 and the total nitrogen concentration was determined by the Nessler colorimetric method.

[0151] 3. Detection of pineapple fruit morbidity after different nitrogen fertilizer treatments

[0152] During the fruit ripening period, 100 pineapple fruits are randomly selected and tested by quality inspectors at the packaging site. The number of diseased fruits is recorded and the total amount of fruits is as large as possible, which can better avoid randomness in the data.

[0153] The calculation formula for the incidence of fruit water core disease is as follows:

[0154] Water core disease incidence = incidence / sample size*100%

[0155] 4. Analysis of the relationship between leaf nitrogen concentration, aboveground biomass and incidence

[0156] The nitrogen concentration of leaves of pineapple plants during the flowering and red stage and the aboveground biomass of plants during the fruit development stage were selected to establish a multivariate linear regression equation in SPSS.

[0157] Implementation 5: Effects of nitrogen and biomass on the incidence of water core disease in “Tainong No. 17” pineapple.

[0158] 1. Experimental Materials

[0159] 1. Fertilizer: urea (N46%), potassium dihydrogen phosphate (P2O5 52%, K2O 34%), potassium sulfate (K2O52%);

[0160] The organic fertilizer was commercial sheep manure organic fertilizer (N 1.84%, P 1.10%, K 2.94%, pH 6.9, organic matter 49%) purchased from Shandong Rongda Biological Fertilizer Co., Ltd.

[0161] 2. Pineapple variety: Tainong No. 17.

[0162] 2. Experimental Methods

[0163] 1. Pineapple planting and nitrogen fertilizer treatment methods

[0164] The test site is located in Longyue Village, Bohou Town, Lingao County, Haikou City, Hainan Province, in the science and technology courtyard jointly built by Hainan University and Hainan Tiandiren Ecological Agriculture Co., Ltd. The area is located in the tropical monsoon climate zone, with a climate suitable for crop growth, abundant rain and heat, and high accumulated temperature. The average annual temperature is 24-25℃, the average annual rainfall is 1280mm, and the annual evaporation is 2-2.5 times the rainfall. The heat is abundant, the rainfall is abundant, and the dry and rainy seasons are distinct. The soil at the test site is basalt brick red soil, with a pH value of 5.71 and an organic matter content of 29.03g·kg -1 , soil total nitrogen content 246.47 mg kg -1 , available phosphorus content 476.19 mg kg -1 , fast-acting potassium content 138.79 mg kg -1 , exchangeable calcium 352.63 mg kg -1 , exchangeable magnesium 104.28 mg kg -1 .

[0165] The experiment was repeated three times, with a total of 18 plots randomly arranged, each plot was 86 square meters, the planting specifications were 33cm×50cm×130cm, double-row planting, 3,000 plants per mu, and the experimental area was about 2.4 mu.

[0166] Pineapples were planted on September 22, 2021 (soil was turned and land was prepared before planting), flowered on August 5, 2022, and harvested at the end of December 2022. According to the amount and period of nitrogen application, a total of 6 treatments were designed in the experiment: ①LowOptT, ②LowConT, ③BalOptT, ④BalconT, ⑤HighOptT, ⑥HighConT.

[0167] ①LowOptT means: nitrogen application is 30% lower than the reasonable supply and is reasonably distributed;

[0168] ②LowConT means: nitrogen application is 30% lower than the reasonable supply, and farmers’ regular allocation;

[0169] ③BalOptT means: reasonable supply and reasonable distribution of nitrogen fertilizer;

[0170] ④BalconT means: reasonable supply of nitrogen fertilizer and regular distribution to farmers;

[0171] ⑤HighOptT means: nitrogen application is 30% higher than the reasonable supply and is reasonably distributed;

[0172] ⑥HighConT means: nitrogen application is 30% higher than the reasonable supply and farmers’ regular allocation;

[0173] Reasonable supply is 500kg / hm 2 ;

[0174] The conventional allocation (ConT) of farmers means that the nitrogen application ratios are 39:12:12:12:12:12:12 before planting (basal fertilizer), slow growth period, early rapid growth period, late rapid growth period, flowering and red stage, and fruit development period respectively;

[0175] Reasonable allocation (OptT) means that the nitrogen application ratios before planting (basal fertilizer application), slow growth period, early rapid growth period, late rapid growth period, flowering and red stage, and fruit development period are 39:13:16:18:9:4 respectively.

[0176] The potassium and phosphorus dosages in the above six treatments were kept the same, with the phosphorus dosage being 160 kg / hm2. 2 , potassium dosage is 720kg / hm 2 The experiment was repeated three times, with a total of 18 plots randomly arranged, each plot was 86 square meters. The planting specifications were 33cm×50cm×130cm, double-row planting, 3,000 plants per mu, and the experimental area was about 2.4 mu. Organic fertilizer was applied as a base fertilizer at one time, and fertilizer was applied later in the form of water and fertilizer.

[0177] 2. Take plant samples at five important growth stages of pineapple plants and weigh the plants to obtain the biomass of the plants, as follows:

[0178] At 110 days (slow growth period), 238 days (rapid growth period), 318 days (flowering and reddening period), 402 days (fruit development period), and 463 days (fruit maturity period) after planting, the plants were separated, washed, wiped clean, dried, weighed fresh weight, and mixed samples were taken from various parts to record their biomass. The plants were fixed in a constant temperature drying oven at 105°C for 30 minutes, and then dried to constant weight at a constant temperature of 75°C. The nitrogen concentration of the dry samples of the plants was determined, and the samples were digested with H2SO4-H2O2 and the total content was determined by the Nessler colorimetric method. The dry matter weight of each part was weighed to convert the dry matter accumulation of each physiological part of the plant. The samples were crushed according to the aboveground part and the fruit, and then put into sealed bags for testing.

[0179] The nitrogen in the plant samples was digested with H2SO4-H2O2 and the total nitrogen concentration was determined by the Nessler colorimetric method.

[0180] 3. Detection of pineapple fruit morbidity after different nitrogen fertilizer treatments

[0181] During the fruit ripening period, 100 pineapple fruits are randomly selected and tested by quality inspectors at the packaging site. The number of diseased fruits is recorded and the sample size of the fruit is as large as possible to better avoid randomness in the data.

[0182] The calculation formula for the incidence of core rot in pineapple fruits is as follows:

[0183] Incidence of core rot = Number of diseased fruits / Sample size * 100%

[0184] 4. Analysis of the relationship between leaf nitrogen concentration and aboveground biomass and the incidence rate

[0185] Select the nitrogen concentration of the leaves at the red emergence stage of flower induction of pineapple plants and the aboveground biomass during the fruit development period to establish a multiple linear regression equation in SPSS.

[0186] In summary, through setting different nitrogen fertilizer application experiments, the present invention has established a multiple linear regression equation between the nitrogen concentration and biomass of pineapple plants and the incidence rate, which can effectively give early warnings for pineapple core rot. The present invention has established a multiple linear regression equation for warning the core rot of "Tainong No. 17" pineapple:

[0187] Y = 4.019X1 + 0.018X2 - 86.028, where Y is the incidence rate, X1 is the nitrogen concentration, and X2 is the biomass; when the incidence of core rot is 0 < Y < 10% it is a low risk, 10% < Y < 30% it is a medium risk, and Y > 30% it is a high risk; take targeted prevention and control measures for the core rot of "Tainong No. 17" pineapple in advance. Through experiments, it is proved that this multiple linear regression equation has high warning accuracy for the core rot of "Tainong No. 17" pineapple and can be widely used for the rapid warning and early prevention and control of the core rot of "Tainong No. 17" pineapple.

[0188] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications once they learn the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0189] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. An early warning method for "Tainong No. 17" pineapple water core disease, characterized in that: It includes the following steps: Apply different amounts of nitrogen fertilizer at different growth stages of pineapple, and respectively detect the above-ground biomass and leaf nitrogen concentration of pineapple plants at different growth stages. Investigate the incidence of pineapple heart rot disease at the mature stage of pineapple fruits; the different growth stages of pineapple include before planting, slow growth stage, early rapid growth stage, late rapid growth stage, flower induction and red appearance stage, fruit development stage and fruit mature stage; The nitrogen fertilizer treatment includes 6 treatment groups: ①LowOptT means: the nitrogen application amount is 30% lower than the reasonable supply mass percentage, and is applied to different growth stages of pineapple according to the reasonable distribution ratio; ②LowConT means: the nitrogen application amount is 30% lower than the reasonable supply mass percentage, and is applied to different growth stages of pineapple according to the conventional distribution ratio of farmers; ③BalOptT means: the nitrogen application amount is reasonably supplied, and is applied to different growth stages of pineapple according to the reasonable distribution ratio; ④BalconT means: the nitrogen application amount is reasonably supplied, and is applied to different growth stages of pineapple according to the conventional distribution ratio of farmers; ⑤HighOptT means: the nitrogen application amount is 30% higher than the reasonable supply mass percentage, and is applied to different growth stages of pineapple according to the reasonable distribution ratio; ⑥HighConT means: the nitrogen application amount is 30% higher than the reasonable supply mass percentage, and is applied to different growth stages of pineapple according to the conventional distribution ratio of farmers; Reasonable supply means nitrogen application rate is 450-500kg / hm 2 ; The conventional distribution ratio of farmers is that the nitrogen application amounts at before planting, slow growth stage, early rapid growth stage, late rapid growth stage, flower induction and red appearance stage and fruit development stage are in the ratio of 38 - 40:12:12:12:12:12 respectively; The reasonable distribution ratio is that the nitrogen application amounts at before planting, slow growth stage, early rapid growth stage, late rapid growth stage, flower induction and red appearance stage and fruit development stage are in the ratio of 38 - 40:13:16:18:9:4 respectively; Construct a multiple linear regression equation between the leaf nitrogen concentration at the flower induction and red appearance stage of pineapple and the above-ground biomass and incidence rate of plants at the fruit development stage; the multiple linear regression equation between the nitrogen concentration and biomass and incidence rate is as follows: Y = 4.019X1 + 0.018X2 - 86.028; Y is the incidence rate of heart rot disease, unit: %, X1 is the leaf nitrogen concentration at the flower induction and red appearance stage, unit: g / kg, X2 is the above-ground biomass of plants at the fruit development stage, unit: g; Warn the incidence rate of pineapple heart rot disease by substituting the detected nitrogen concentration of leaves at the flower induction and red appearance stage of pineapple and the above-ground biomass of plants at the fruit development stage into the multiple linear regression equation.

2. The early warning method for pineapple water core disease of "Tainong No. 17" according to claim 1, characterized in that, The conventional distribution of farmers means that the nitrogen application amounts at before planting, slow growth stage, early rapid growth stage, late rapid growth stage, flower induction and red appearance stage, fruit development stage are in the ratio of 40:12:12:12:12:12 respectively.

3. The early warning method for pineapple water core disease of "Tainong No. 17" according to claim 1, characterized in that, The determination method of the above-ground biomass of plants is: collect the above-ground part of pineapple plants, wash, dry the moisture, and weigh its fresh weight.

4. The early warning method for pineapple water core disease of "Tainong No. 17" according to claim 1, characterized in that, The risk grading of the incidence of pineapple heart rot disease is as follows: when the incidence of heart rot disease is 0 < Y < 10% is low risk, 10% < Y < 30% is medium risk, Y > 30% is high risk.

5. The early warning method for pineapple water core disease of "Tainong No. 17" according to claim 1, characterized in that, When warning the incidence of core rot in pineapple planting areas, the nitrogen concentration at the red-emerging stage of pineapple flower induction and the biomass during the fruit development period are detected and substituted into the above-mentioned multiple linear regression equation to calculate the incidence rate.

6. An application of a multiple linear regression equation model in predicting the incidence of water core disease in "Tainong No. 17" pineapple, characterized in that: The multiple linear regression equation model is the multiple linear regression equation for predicting core rot of "Tainong No. 17" pineapple obtained in Claim 1: Y = 4.019X1 + 0.018X2 - 86.028; Y is the incidence rate of core rot, unit: %, X1 is the nitrogen concentration in leaves at the red-emerging stage of flower induction, unit: g / kg, X2 is the above-ground biomass of the plant during the fruit development period, unit: g; When the incidence of core rot occurs, 0 < Y < 10% is a low risk, 10% < Y < 30% is a medium risk, and Y > 30% is a high risk.

Images