A method for efficient utilization of chufa and forest water and fertilizer through intercropping

Abstract

The present application relates to the cultivation technology field of special crops or plants, and discloses a kind of chufa and forest water and fertilizer efficient utilization intercropping method, no longer like traditional intercropping mode tries to water and fertilizer simultaneously to intercropped multiple crops, but directly separates the water and fertilizer management of chufa and forest by combining drip irrigation system, and does not affect each other.Avoid the waste of water and fertilizer resources caused by unified irrigation and fertilization of forest and chufa.At the same time, the tree crown of the single tree is segmented to remove the interference of remote sensing to identify the tree crown of the lack of fertilizer plot;And transform the drip irrigation system and forest cultivation method, ensure that chufa will only appear stress symptoms in a whole row of plants when under nutritional stress, use this feature to exclude the area that appears similar to lack of fertilizer symptoms due to weak light stress.Using the unique characteristics of sandy soil and chufa itself, indirect monitoring of potassium deficiency by monitoring nitrogen deficiency, timely detection of potassium deficiency is realized, and timely fertilization can be realized by setting additional fertilization interface.

Description

Technical Field

[0001] This invention relates to the field of cultivation technology for special crops or plants not mentioned, and in particular to an intercropping method for efficient water and fertilizer utilization of tiger nuts and forest trees. Background Technology

[0002] Tiger nuts (scientific name: *Cyperus esculentus* L.), also known as oil nut, underground walnut, tiger nut, etc., are plants belonging to the genus *Cyperus* in the family Cyperaceae. Rich in nutrients, they are a high-quality, high-yield, and multi-purpose economic crop with significant comprehensive utilization value, serving as oil, grain, feed, and medicinal materials. They are characterized by wide adaptability, short growing season, large biomass, high oil content, and high added value. Originally from the Nile River basin in Africa and the Mediterranean coast, they have a very long history of cultivation and are now widely distributed in tropical, subtropical, and temperate regions of Africa, Europe, Asia, North America, and Latin America.

[0003] Tiger nuts (Cyperus alternifolius) are sedges, closely related to the commonly seen nutgrass, and thus share similar characteristics: the plant relies heavily on phytoliths for strength. However, tiger nuts lack the efficient silicon absorption and accumulation mechanisms of grasses, therefore they are more likely to be classified as "non-silicon-accumulating" plants. Tiger nut plants are very brittle, making field operations extremely difficult. Furthermore, tiger nuts are not beans, but rather bean-like tubers connected to the above-ground parts by very fine roots, making normal harvesting in conventional soil nearly impossible (they will break off in the soil). Considering these factors, tiger nuts are best cultivated in sandy soil to meet their harvesting needs, and automated field operations are preferable.

[0004] Sandy soil is a typical primary soil, extremely infertile with severely insufficient nutrient supply; it also has very poor water and fertilizer retention capacity, poor absorption of applied fertilizers and the already scarce soluble nutrients in the soil, making it highly susceptible to leaching away with water. Furthermore, tiger nuts are a crop with a very short growing season; if short-term nutrient deficiency is not corrected in time, delayed fertilization cannot reverse the yield loss. Therefore, to ensure tiger nut yield, good water and fertilizer management is essential. However, the inventors discovered a series of problems that make water and fertilizer management for tiger nuts extremely difficult: 1. Sandy soil suitable for planting tiger nuts is scarce, often requiring intercropping with trees, which significantly increases the difficulty of water and fertilizer management and makes it difficult to use remote sensing to identify areas with nutrient deficiencies. Sandy soil is a soil type found in arid regions, where rainfall is insufficient to meet cultivation needs. Sandy land suitable for cultivation inevitably requires irrigation systems, is scarce, and is often fully utilized. Young trees, with limited shading and small canopies, do not hinder mechanical operations and can be intercropped with tiger nuts. However, fruit trees and tiger nuts have different biological characteristics and significantly different root depths. Tiger nuts require more frequent fertilization during cultivation, and their nutrient requirements differ from those of forest trees, making water and fertilizer management during intercropping extremely difficult. This often results in poor growth for both the trees and the intercropped herbaceous crops. This difficulty has even led many provinces, including Jilin, to completely ban intercropping between forestry and grain crops.

[0005] Furthermore, intercropping poses a significant challenge to identifying nutrient-deficient areas using remote sensing. This is because the tree canopy in the remote sensing images not only interferes with the images themselves used for analysis, but also inevitably causes varying degrees of light stress to tiger nuts in different locations (light stress refers to insufficient light leading to poor growth, a problem that intercropping cannot avoid or completely solve). The symptoms of light stress on tiger nut plants are similar to those of nutrient stress, making it difficult to distinguish between light stress and nutrient stress when performing image analysis and identification.

[0006] 2. While integrated water and fertilizer drip irrigation systems offer a high degree of automation and save manpower, they also lack human oversight during fertilization, making them prone to nutrient deficiency due to pipeline problems. Drip irrigation is the most efficient irrigation method, and it can also fertilize simultaneously, with the fertilizer flowing with the water, significantly reducing labor costs. However, because each well irrigates a large area, some plots, due to their distance from the drip irrigation head and the long water delivery pipelines, experience significant head loss, potentially leading to insufficient irrigation. In other plots, poor water quality can cause drippers to become clogged by fine sand or salt crystals, reducing flow rate. These areas may suffer from water and fertilizer deficiencies. While water shortages can be addressed by increasing irrigation time, compensating for small-area fertilizer deficiencies by increasing fertilizer application would result in significant fertilizer waste and a substantial increase in production costs.

[0007] 3. Potassium is crucial for tiger nut yield, but the symptoms of potassium deficiency do not appear immediately, making it too late to remedy the situation by the time the deficiency is detected: Tiger nuts are a potassium-loving crop. Their economic product is their underground tubers, and potassium is crucial for the synthesis, transport, and accumulation of carbohydrates, directly affecting tuber enlargement, yield, and oil / starch content. However, potassium ions are easily lost, and sandy soil has difficulty retaining them effectively. Therefore, tiger nuts are generally considered to have a high potassium requirement and are prone to potassium deficiency. When fertilizer is lacking, potassium deficiency is often the primary concern, and potassium fertilizer is mainly supplemented. However, the nutrient stress caused by potassium deficiency does not immediately show observable symptoms on tiger nut plants. Potassium is a reusable element in plants. When soil potassium supply is insufficient, plants will transfer potassium from older leaves to the more vigorous new leaves and apical meristems. In the early stages of growth, potassium requirements are relatively low, and no or only mild symptoms are observed. Furthermore, potassium in the soil exists in different forms (available potassium, slow-release potassium, and mineral potassium), undergoing a gradual release and depletion process. This means that by the time potassium deficiency symptoms are observed, the tiger nut plant has already been affected by potassium deficiency for a long time, making yield reduction unavoidable.

[0008] Soil typically retains nitrogen much better than potassium because nitrogen is gradually converted into organic nitrogen in microorganisms and humus, while potassium cannot. Summary of the Invention

[0009] This invention provides an intercropping method for efficient water and fertilizer utilization of tiger nuts and forest trees.

[0010] The technical problem to be solved is that tiger nuts need to be cultivated on sparsely cultivated land such as sandy soil with irrigation, and intercropping is often required, which brings a series of difficulties to the water and fertilizer management and fertilization of tiger nuts.

[0011] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: an intercropping method for efficient water and fertilizer utilization of tiger nuts and forest trees, which uses a drip irrigation network for integrated water and fertilizer irrigation, and irrigates tiger nuts and forest trees separately at different times through independent drip irrigation branches. During the growth process of tiger nuts, remote sensing is used to locate nutrient-deficient plots in a timely manner and supplement fertilizer. The intercropping method includes the following steps: Step 1: By screening or adjusting existing forest land, obtain forest land suitable for tiger nut intercropping and record it as suitable intercropping forest. The suitable intercropping forest meets the following conditions: Condition 1.1: The cultivated trees belong to the category of economic forests of the arbor type; Condition 1.2: The soil is sandy soil; Condition 1.3: The cultivated trees adopt a large spacing between plants and rows, and the row spacing meets the needs of tiger nut sowing and harvesting machinery operation; Condition 1.4: The planting rows of cultivated trees are oriented north-south; Step 2: Sow tiger nuts between the rows of trees, ensuring that the lateral branches of the trees do not interfere with the mechanical operation of tiger nuts, and avoid the shade of the tree canopy at noon; Step 3: Construct separate drip irrigation networks for the trees and tiger nuts, with the drip irrigation networks for the trees and tiger nuts operating independently. The drip irrigation network for tiger nuts is managed in sections. Each section is supplied with water by a unique corresponding drip irrigation branch pipe. Each drip irrigation branch pipe in each section has only one inlet, and the sections do not intersect. In the drip irrigation network for tiger nuts, the drip irrigation tapes all extend in the north-south direction, and the inlet of each drip irrigation branch pipe in each section is equipped with an interface for connecting to the bypass fertilizer tank, which is called the temporary fertilizer inlet. Step 4: Independently manage water and fertilizer for the trees and tiger nuts, and regularly take remote sensing images of tiger nut plants at noon. Segment the tree crowns of the trees in the remote sensing images, remove the crown portion from the remote sensing images, and record the remaining remote sensing images as images to be analyzed. Analyze the images to be analyzed to identify nutrient-deficient areas; the sections of the drip irrigation network that cover the nutrient-deficient areas are recorded as nutrient-deficient sections. Step 5: Connect the bypass fertilizer tank to the temporary fertilizer inlet to replenish fertilizer to the nutrient-deficient area; Step Six: Repeat steps four and five to ensure the tiger nuts receive sufficient fertilizer until harvest.

[0012] Furthermore, in step one, the trees are pruned using the following methods to facilitate subsequent operations: Prune all overgrown branches within the working height range of the tiger nuts; Prune the lateral branches between two adjacent trees in the same planting row so that in the midday remote sensing image, the images of two adjacent trees are separated by the bare ground illuminated by sunlight.

[0013] Furthermore, in step two, tiger nuts are sown from late April to mid-May; irrigation is carried out every 7-10 days after sowing until mid-to-late August; each irrigation lasts 4-6 hours, and corresponding water-soluble fertilizers are applied during the tiger nut seedling stage, tillering stage, tuber formation stage, and tuber enlargement stage.

[0014] Furthermore, in step three, the drip irrigation network for trees is managed in blocks, and the blocks are the same as those for tiger nuts. Each block of the drip irrigation network for trees is supplied with water by a unique corresponding drip irrigation branch pipe. If the drip irrigation branch pipes for trees and tiger nuts draw water from the same ground stake, a valve is installed at the inlet of the drip irrigation branch pipe. Two forest drip irrigation pipes are installed in each row of trees, with drippers on the drip irrigation pipes arranged around the trees, and at least four drippers are installed around each tree.

[0015] Furthermore, in step four, the following method is used to decouple the symptoms of low light stress and nutritional stress experienced by the tiger nut plants in the images to be analyzed: Instead of identifying areas of stress on tiger nut plants in the images to be analyzed as nutrient-deficient areas, we look for areas that do not show symptoms of nutrient stress, then project them in the north and south directions, exclude the areas covered by the projection, and the remaining areas are the nutrient-deficient areas.

[0016] Furthermore, in step four, the following methods are used to ensure that nutritional stress symptoms appear in the images to be analyzed in a timely manner: Select the characteristic elements of nutrient deficiency and determine the corresponding nutrient stress symptoms. By monitoring the nutrient stress symptoms caused by the characteristic elements of nutrient deficiency, we can indirectly determine whether tiger pea plants are nutrient deficient. The nutrient deficiency characteristic elements meet the following conditions: Condition 4.1: Easily eroded in sandy soil; Condition 4.2: Nutrient stress symptoms appear immediately after nutrient deficiency within the tiger nut plant, as the nutrients cannot be reused within the plant. Condition 4.3: At least one nutrient stress symptom caused by the absence can be monitored by remote sensing and recorded as a remote sensing symptom; and there is at least one nutrient stress symptom different from the remote sensing symptom that can be quickly identified on-site to determine whether a row of tiger pea plants is deficient in fertilizer and recorded as a subdivided symptom. When analyzing the image to be analyzed, select the areas that do not show remote sensing symptoms, project them in the north and south directions respectively, exclude the areas covered by the projection, and the remaining areas are the fertilizer-deficient areas.

[0017] Furthermore, in step four, multispectral and visible light photos of the area where the tiger nuts are located are obtained through drone aerial photography, and the images to be analyzed are obtained based on these. The element characterized by nutrient deficiency is nitrogen; The remote sensing symptoms were low NDVI and GNDVI indices in tiger nut plants. The specific symptoms are that the plant height is lower than the surrounding area, while the degree of ground exposure is higher than the surrounding area.

[0018] Furthermore, in step three, a section of the drip irrigation network that is close to the water source and free from tree shade is selected and recorded as the characteristic section. The NDVI index and GNDVI index of the tiger pea plants in the characteristic section are monitored and recorded as the characteristic NDVI index and characteristic GNDVI index, respectively. The remote sensing symptoms are defined as tiger nut plants having an NDVI index lower than 10% of the characteristic NDVI index or lower than 0.6, and a GNDVI index lower than 10% of the characteristic GNDVI index or lower than 0.6.

[0019] Furthermore, in step five, before applying fertilizer, check the specific symptoms of tiger pea plants along the drip irrigation branch pipes of the nutrient-deficient sections, and tie the drip irrigation tapes of the tiger pea plants within the irrigation area that are not nutrient-deficient. After applying fertilizer, restore the temporary fertilizer inlet to its original state and remove the bypass fertilizer tank, and then untie the drip irrigation tapes.

[0020] Compared with existing technologies, the intercropping method for efficient water and fertilizer utilization of tiger nuts and forest trees proposed in this invention has the following advantages: This invention departs from the traditional intercropping method, which attempts to simultaneously irrigate and fertilize multiple intercropped crops. Instead, it integrates a drip irrigation system to completely separate the water and fertilizer management of tiger nuts and trees, ensuring they do not interfere with each other. This avoids the waste of water and fertilizer resources caused by uniform irrigation and fertilization of trees and tiger nuts due to their different growth rhythms, root depths, and fertilizer requirements.

[0021] Simultaneously, by fully utilizing the latest image recognition techniques, interference was removed through individual tree canopy segmentation, and remote sensing was used to identify nutrient-deficient areas. Combined with a modified drip irrigation system and forestry cultivation methods, it was ensured that tiger peas only exhibited stress symptoms when subjected to nutrient stress, not when subjected to only low light stress. This characteristic was then used to eliminate areas exhibiting similar nutrient deficiency symptoms due to low light stress, allowing for the identification of truly nutrient-deficient areas for fertilization. This overcame the impact of intercropping on fertilization.

[0022] Sandy soil has a very poor nitrogen retention capacity (conventional soils have a strong nitrogen retention capacity, but sandy soils are very poor). Whenever nitrogen deficiency occurs (mild nitrogen deficiency may not necessarily affect yield, while excessive nitrogen can cause excessive vegetative growth), potassium deficiency will also occur simultaneously. Furthermore, tiger pea plants have a short growth cycle, and after nitrogen deficiency, the plants immediately show stress symptoms that can be observed using remote sensing. By monitoring nitrogen deficiency, potassium deficiency can be indirectly monitored, enabling timely detection of potassium deficiency. Combined with an additional fertilization interface, timely fertilization can be achieved. Attached Figure Description

[0023] Figure 1 This is a flowchart of an intercropping method for efficient water and fertilizer utilization of tiger nuts and forest trees according to the present invention. Detailed Implementation

[0024] Taking a tiger nut cultivation base applying the present invention as an example, an intercropping method for efficient water and fertilizer utilization of tiger nuts and trees is described. This method employs a drip irrigation network for integrated water and fertilizer irrigation, irrigating both tiger nuts and trees at different times via independent drip irrigation branches. During the tiger nut growth process, remote sensing is used to promptly identify nutrient-deficient areas and supplement fertilizer accordingly. The intercropping method includes the following steps: Step 1: By screening or adjusting existing forest land, obtain suitable forest land for tiger nut intercropping and record it as suitable intercropping forest. Suitable intercropping forest meets the following conditions: Condition 1.1: The cultivated trees belong to the economic forest category of arbor trees; this allows for the use of large spacing between trees and rows, ensuring sufficient space for mechanical operations.

[0025] Condition 1.2: The soil is sandy; as described in the background technology, tiger nuts are not suitable for cultivation in soils other than sandy soil.

[0026] Condition 1.3: The cultivated trees adopt a large spacing between plants and rows, and the row spacing meets the needs of tiger nut sowing and harvesting machinery operation; Condition 1.4: The planting rows of cultivated trees are oriented north-south; A north-south orientation not only reduces shading but also facilitates subsequent remote sensing operations. In remote sensing images taken at noon, the shadows of trees will fall on the planting rows rather than on the tiger pea plants, thus minimizing the impact on remote sensing image analysis.

[0027] Step 2: Sow tiger nuts between the rows of trees. The sowing area should be such that the side branches of the trees do not interfere with the mechanical operation of tiger nuts, and avoid the shade of the tree canopy at noon (the shade on the day with the shortest daylight during the tiger nut's growing season can be used as a reference) to ensure that the planted tiger nuts can receive the minimum amount of light.

[0028] Step 3: Construct separate drip irrigation networks for the trees and tiger nuts, with the drip irrigation networks for the trees and tiger nuts operating independently. Here's a brief description of the structure of a drip irrigation network. Generally, a drip irrigation network consists of underground drip irrigation trunk lines that transport water from the source to the ground. Then, through ground stakes, the trunk lines connect to drip irrigation branch lines. Each branch line has multiple drip irrigation tapes (also known as drip irrigation capillaries) extending to the left and right like a comb. The drip irrigation tapes have openings to drip water into the vicinity of the crop roots.

[0029] When the drip irrigation branch extends on the ground, there are no crops nearby, so you can check the condition of the nearby crops along the drip irrigation branch. If there is a lack of fertilizer, the entire area covered by the drip irrigation tape will be deficient in fertilizer. Checking along the drip irrigation branch will be very intuitive (the crops on a certain line on the left and right sides will be abnormal, making the nutrient stress symptoms that are not easy to observe in the first place also obvious).

[0030] The drip irrigation network for tiger nuts is managed in blocks, with each block supplied with water by a unique corresponding drip irrigation branch pipe. Each drip irrigation branch pipe in each block has only one inlet, and the blocks do not overlap with each other. Localized nutrient deficiency occurs because the drip irrigation network is too far from the water source or is partially blocked. Adjusting the drip irrigation network in this way ensures that the affected area can be fertilized by a single temporary fertilization port, thus simplifying the problem and preventing the nutrient deficiency area from spanning multiple areas. It also makes subsequent maintenance easier.

[0031] In the drip irrigation network of tiger nuts, the drip irrigation tapes all extend in the north-south direction, and the inlet of each segment of the drip irrigation branch pipe is equipped with an interface for connecting to the bypass fertilizer tank, which is called the temporary fertilizer inlet. The drip irrigation tapes here extend in a north-south direction, also to facilitate subsequent remote sensing operations. The symptoms of low light stress and nutrient stress are very similar in the remote sensing images, but their distribution differs. Due to the design in this embodiment, tiger nuts under low light stress will not be continuously distributed in a north-south direction, but tiger nuts under nutrient stress will be, thus allowing for differentiation between the two.

[0032] Step 4: Independently manage water and fertilizer for the trees and tiger nuts, and regularly take remote sensing images of tiger nut plants at noon. Segment the tree crowns of the trees in the remote sensing images, remove the crown portion from the remote sensing images, and record the remaining remote sensing images as images to be analyzed. Analyze the images to be analyzed to identify nutrient-deficient areas; the sections of the drip irrigation network that cover the nutrient-deficient areas are recorded as nutrient-deficient sections. Step 5: Connect the bypass fertilizer tank to the temporary fertilizer inlet to replenish fertilizer to the nutrient-deficient area; The bypass fertilizer applicator is a relatively traditional fertilization facility for drip irrigation networks. It is typically installed near the water source, directly mixing fertilizer into the drip irrigation trunk line. However, it cannot effectively determine whether the fertilizer is used up, and its application efficiency is initially high and then slows down, so it is gradually being phased out. The reason it is used here for supplemental fertilization is its portability. Although traditionally it is fixed near the water source, its structure allows for easy relocation, and with the addition of quick-release connectors, targeted fertilization can be achieved.

[0033] Step Six: Repeat steps four and five to ensure the tiger nuts receive sufficient fertilizer until harvest.

[0034] In this embodiment, the tree is fragrant pear. From late April to mid-May, tiger nuts are sown between the rows of fragrant pears. The sowing range is more than 1m away from the fragrant pears on both sides, so that the lateral branches of the fragrant pears do not affect the mechanical operation of the tiger nuts. The spacing between the rows and plants of tiger nuts is 10cm×35cm, and the sowing rate is 12-15kg / mu.

[0035] After the ground stakes are set up to distribute water in the drip irrigation system plot, a Ф90 tee is installed, and two parallel Ф90 PE branch pipes are installed. One branch pipe is fitted with forest drip irrigation pipes to control irrigation and fertilization of fragrant pears. Two drip irrigation pipes are installed on each row of fragrant pears on both sides of the pears. The service life is ≥5 years. Drip emitters are installed on the drip irrigation pipes according to the spacing between fragrant pear trees. The drip emitter flow rate is 8-10L / h, ensuring that there are more than 4 drip emitters around each fragrant pear tree. The other branch pipe is fitted with agricultural drip irrigation tape at a row spacing of 35cm-45cm to control irrigation and fertilization of tiger peas. The drip emitter spacing is 30cm-50cm, the drip emitter flow rate is 2.4-3.6L / h, and the service life of the agricultural drip irrigation tape is ≥1 year.

[0036] Pears should be irrigated starting in late March, once a month in March, April, May, and September, and twice a month in June, July, and August, for 12-24 hours each time. Water-soluble fertilizer should be applied as needed according to the flowering, fruit setting, and fruit enlargement stages of the pears. Tiger nuts should be irrigated every 7-10 days after sowing until mid-to-late August, with each irrigation lasting 4-6 hours. Water-soluble fertilizer should be applied as needed according to the seedling emergence, tillering, tuber formation, and tuber enlargement stages of the tiger nuts.

[0037] Before harvesting tiger nuts, the drip irrigation tape is manually rolled up and moved out of the planting area, and the tiger nut harvester is used for harvesting; the drip irrigation pipes on the sides of the pear rows do not need to be moved, just be careful not to damage them during the tiger nut harvesting process.

[0038] In step one, the trees are pruned in the following way to facilitate subsequent work: Prune all overgrown branches within the working height range of the tiger nuts; Even if these overgrown branches do not affect mechanical operations in the short term, they will cause problems during their subsequent growth, so they need to be pruned unconditionally.

[0039] Prune the lateral branches between adjacent trees in the same planting row so that in midday remote sensing images, the images of adjacent trees are separated by the bare ground illuminated by sunlight. This is done to facilitate individual tree crown segmentation, ensuring clear and non-overlapping crown edges (the color of the sand under sunlight differs greatly from that of the tree crown). Individual tree crown segmentation can be completed using traditional multi-scale watershed segmentation methods without relying on LiDAR point cloud assistance.

[0040] Specifically, when pruning, you can prune the branches of adjacent trees whose shadows overlap at noon.

[0041] In step three, the drip irrigation network for the trees is managed in sections, and the sections are the same as those for the tiger nuts. Each section of the drip irrigation network for the trees is supplied with water by a unique corresponding drip irrigation branch pipe. If the drip irrigation branch pipes for the trees and the drip irrigation branch pipes for the tiger nuts draw water from the same ground stake, a valve is installed at the inlet of the drip irrigation branch pipe to ensure that their water and fertilizer management can be independent of each other.

[0042] Two forest drip irrigation pipes are installed in each row of trees, with drippers on the drip irrigation pipes arranged around the trees, and at least four drippers are installed around each tree.

[0043] In step four, the following method is used to decouple the symptoms of low light stress and nutritional stress experienced by tiger nut plants in the images to be analyzed: Instead of identifying areas of stress on tiger nut plants in the images to be analyzed as nutrient-deficient areas, we look for areas that do not show symptoms of nutrient stress, then project them in the north and south directions, exclude the areas covered by the projection, and the remaining areas are the nutrient-deficient areas.

[0044] In remote sensing images, symptoms of low light stress and nutrient stress are very similar and exhibit significant coupling. Failing to distinguish between them could lead to the unnecessary application of fertilizer to areas that are not lacking in nutrients but are shaded, which is pointless (low light stress is unavoidable) and wastes fertilizer. Note that "no nutrient stress symptoms" here also includes "no low light stress symptoms," because the two are very similar in remote sensing images. If nutrient stress symptoms are absent, then low light stress symptoms are also absent.

[0045] In this embodiment, a series of methods are used to prevent tiger nuts under low light stress from distributing continuously in a north-south direction, while tiger nuts under nutrient stress will continue to distribute, thus allowing for differentiation between the two. The specific principle is as follows: Fertilizer is provided by drip irrigation tape. Nutrient deficiency occurs either because the drip irrigation tape is too far from the water source or because the inlet is blocked (the drip irrigation tape itself is replaced after each crop, making it a consumable item, so it doesn't inherently cause problems). Therefore, tiger peas under nutrient stress will be distributed continuously in a north-south direction. However, due to the discontinuous nature of the forest, it's impossible for all tiger pea plants in the north-south direction to be shaded. Some tiger pea plants will not be shaded by the trees outside of midday. These tiger pea plants, unaffected by low light stress, will not show signs of nutrient deficiency in remote sensing images taken at midday if they are not nutrient-deficient, indicating that the corresponding drip irrigation tape is functioning correctly, and all tiger pea plants in the north-south direction are not nutrient-deficient. This eliminates tiger pea plants that appear to be nutrient-deficient but are actually not.

[0046] In step four, the following methods are used to ensure that nutritional stress symptoms appear in the images to be analyzed in a timely manner: Select the characteristic elements of nutrient deficiency and determine the corresponding nutrient stress symptoms. By monitoring the nutrient stress symptoms caused by the characteristic elements of nutrient deficiency, we can indirectly determine whether tiger pea plants are nutrient deficient. The following conditions must be met to identify the nutrient deficiency characteristics: Condition 4.1: Easily eroded in sandy soil; Potassium is easily lost in poorly fertile soils. If the deficiency of other fertilizer elements is to be used to indirectly indicate the deficiency of potassium, then that fertilizer element must be easily lost in the corresponding poorly fertile soil, so that when it is lacking, potassium will also be lacking.

[0047] Condition 4.2: Nutrient stress symptoms appear immediately after nutrient deficiency within the tiger nut plant, as the nutrients cannot be reused within the plant. This ensures timely detection of nutrient deficiencies, avoiding situations like potassium deficiency where symptoms only appear after a prolonged period, leaving insufficient time for replenishment. In practice, "immediately" generally means that a nutrient deficiency can be detected within a week.

[0048] Condition 4.3: At least one nutrient stress symptom caused by the absence can be monitored by remote sensing and recorded as a remote sensing symptom; and there is at least one nutrient stress symptom different from the remote sensing symptom that can be quickly identified on-site to determine whether a row of tiger pea plants is deficient in fertilizer and recorded as a subdivided symptom. For example, potassium stress symptoms often manifest as the death of lower leaves, which are difficult to detect in remote sensing images due to the obstruction of upper leaves. Therefore, symptoms visible to remote sensing are needed, but symptoms visible to remote sensing may not be recognizable to the human eye on-site, which is detrimental to the application of drip irrigation tape.

[0049] When analyzing the image to be analyzed, select the areas that do not show remote sensing symptoms, project them in the north and south directions respectively, exclude the areas covered by the projection, and the remaining areas are the fertilizer-deficient areas.

[0050] In step four, multispectral and visible light photos of the area where the tiger nuts are located are obtained through drone aerial photography, and the images to be analyzed are obtained based on these. The characteristic element of nutrient deficiency is nitrogen; Sandy soil lacks humus and microorganisms, so most of the nitrogen fertilizer applied to it remains in easily lost forms such as ammonium, nitrate, and urea, just like potassium ions. At the same time, sandy soil itself is infertile and lacks nutrient accumulation. When nitrogen is depleted to the point of deficiency, potassium will also become deficient (tiger nuts prefer potassium).

[0051] The remote sensing symptoms were low NDVI and GNDVI indices in tiger nut plants. NDVI is derived from the reflectance values ​​of the near-infrared and red bands of an image, expressed as: NDVI = (NIR - R) / (NIR + R), where NIR is the reflectance value of the near-infrared band and R is the reflectance value of the red band. GNDVI is a vegetation index calculated using the ratio of reflectance in the green and near-infrared bands. Compared to traditional NDVI, GNDVI is more sensitive to green vegetation and can more accurately assess vegetation cover and growth status. Its calculation formula is as follows: GNDVI = (NIR + Green)(NIR − Green). Where NIR represents the reflectance in the near-infrared band, and Green represents the reflectance in the green band.

[0052] These two indices rely on analyzing color in remote sensing images to determine plant growth status. Nitrogen deficiency in tiger nut plants will immediately cause a color change, thus making them identifiable. Two indices are used for cross-verification to avoid misjudgment due to exposure issues with a single indice.

[0053] Note that if tiger nut plants are subjected to low light stress, the NDVI and GNDVI indices will also decrease. Therefore, it cannot be concluded that there is a lack of fertilizer simply because these two indices are below the standard.

[0054] In this embodiment, the specific symptoms are defined as plant height being lower than the surrounding area, while the degree of ground exposure is higher than the surrounding area. These two indicators are not actually obvious for a single tiger pea plant, but considering that the growth status of the plants corresponding to the rows of drip irrigation capillaries is checked along the drip irrigation branch pipes, a row of plants that are short and have few tillers becomes very noticeable.

[0055] In step three, a section of the drip irrigation network that is close to the water source and free from tree shade is selected and recorded as the characteristic section. The NDVI index and GNDVI index of the tiger pea plants in the characteristic section are monitored and recorded as the characteristic NDVI index and characteristic GNDVI index, respectively. The characteristic sections need to be inspected regularly for their pipe connections and tiger pea plant growth to ensure that the pipes are not blocked, there is no lack of fertilizer, and there is no shading.

[0056] Remote sensing symptoms include tiger nut plants with an NDVI index lower than 10% of the characteristic NDVI index or lower than 0.6, and a GNDVI index lower than 10% of the characteristic GNDVI index or lower than 0.6.

[0057] Depending on weather conditions, tiger nut varieties, and soil conditions, the NDVI and GNDVI indices may fluctuate in normally growing areas. Therefore, a variable characteristic value needs to be set; a value 10% lower than this value can be considered nitrogen deficiency, rather than a fixed value. However, a value below 0.6 is always a serious problem, so when it is below 0.6, the characteristic value can be disregarded, and nitrogen deficiency can be directly identified. Conversely, only when both indices are above 0.6, the NDVI index is 10% higher than the characteristic NDVI index, and the GNDVI is 10% higher than the characteristic GNDVI index, can an area be considered free of remote sensing symptoms.

[0058] In step five, before applying fertilizer, check the individual symptoms of tiger pea plants along the drip irrigation branch pipes of the nutrient-deficient sections, and tie the drip irrigation tapes of the tiger pea plants within the irrigation area that are not nutrient-deficient. After applying fertilizer, restore the temporary fertilizer inlet to its original state and remove the bypass fertilizer tank, and then untie the drip irrigation tapes.

[0059] Even within the same section, some areas may lack fertilizer while others do not, because blockages are not always located near the inlet. To conserve fertilizer, it is necessary to tie the drip tape along the drip irrigation branch pipes to the areas lacking fertilizer, and then restore the tape after fertilization.

[0060] In this embodiment, the drip irrigation branch pipe uses the ground exit pile as the water inlet, and the temporary fertilizer inlet is set close to the ground exit pile. It includes two bypass pipes connected to the drip irrigation branch pipe through a tee. Each bypass pipe is equipped with a bypass valve, and each bypass pipe end is equipped with a threaded connector. In the drip irrigation branch pipe, a control valve is installed on the pipe located between the two tee. When fertilizing, the inlet and outlet pipes of the bypass fertilizer tank are first connected to the two threaded connectors, then the two bypass valves are opened, and then the control valve is closed to create a pressure difference between the inlet and outlet pipes of the bypass fertilizer tank, so that water flows through the bypass fertilizer tank for fertilization.

[0061] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for efficient water and fertilizer utilization of tiger nuts and forest trees through intercropping, characterized in that: A drip irrigation network is used for integrated water and fertilizer irrigation. Independent drip irrigation branches are used to irrigate tiger nuts and trees at different times. During the tiger nut growth process, remote sensing is used to locate nutrient-deficient areas and supplement fertilizer accordingly. The intercropping method includes the following steps: Step 1: By screening or adjusting existing forest land, obtain forest land suitable for tiger nut intercropping and record it as suitable intercropping forest. The suitable intercropping forest meets the following conditions: Condition 1.1: The cultivated trees belong to the category of economic forests of the arbor type; Condition 1.2: The soil is sandy soil; Condition 1.3: The cultivated trees adopt a large spacing between plants and rows, and the row spacing meets the needs of tiger nut sowing and harvesting machinery operation; Condition 1.4: The planting rows of cultivated trees are oriented north-south; Step 2: Sow tiger nuts between the rows of trees, ensuring that the lateral branches of the trees do not interfere with the mechanical operation of tiger nuts, and avoid the shade of the tree canopy at noon; Step 3: Construct separate drip irrigation networks for the trees and tiger nuts, with the drip irrigation networks for the trees and tiger nuts operating independently. The drip irrigation network for tiger nuts is managed in sections. Each section is supplied with water by a unique corresponding drip irrigation branch pipe. Each drip irrigation branch pipe in each section has only one inlet, and the sections do not intersect. In the drip irrigation network for tiger nuts, the drip irrigation tapes all extend in the north-south direction, and the inlet of each drip irrigation branch pipe in each section is equipped with an interface for connecting to the bypass fertilizer tank, which is called the temporary fertilizer inlet. Step 4: Independently manage water and fertilizer for the trees and tiger nuts, and regularly take remote sensing images of tiger nut plants at noon. Segment the tree crowns of the trees in the remote sensing images, remove the crown portion from the remote sensing images, and record the remaining remote sensing images as images to be analyzed. Analyze the images to be analyzed to identify nutrient-deficient areas; the sections of the drip irrigation network that cover the nutrient-deficient areas are recorded as nutrient-deficient sections. Step 5: Connect the bypass fertilizer tank to the temporary fertilizer inlet to replenish fertilizer to the nutrient-deficient area; Step Six: Repeat steps four and five to ensure the tiger nuts receive sufficient fertilizer until harvest; In step four, the following method is used to decouple the symptoms of low light stress and nutritional stress experienced by tiger nut plants in the images to be analyzed: Instead of searching for areas of stress on tiger nut plants in the images to be analyzed as nutrient-deficient areas, we search for areas that do not show symptoms of nutrient stress, and then project them in the north and south directions respectively. We exclude the areas covered by the projection, and the remaining areas are the nutrient-deficient areas. In step four, the following methods are used to ensure that nutritional stress symptoms appear in the images to be analyzed in a timely manner: Select the characteristic elements of nutrient deficiency and determine the corresponding nutrient stress symptoms. By monitoring the nutrient stress symptoms caused by the characteristic elements of nutrient deficiency, we can indirectly determine whether tiger pea plants are nutrient deficient. The nutrient deficiency characteristic elements meet the following conditions: Condition 4.1: Easily eroded in sandy soil; Condition 4.2: Nutrient stress symptoms appear immediately after nutrient deficiency within the tiger nut plant, as the nutrients cannot be reused within the plant. Condition 4.3: At least one nutrient stress symptom caused by the absence can be monitored by remote sensing and recorded as a remote sensing symptom; and there is at least one nutrient stress symptom different from the remote sensing symptom that can be quickly identified on-site to determine whether a row of tiger pea plants is deficient in fertilizer and recorded as a subdivided symptom. When analyzing the image to be analyzed, select the areas that do not show remote sensing symptoms, project them in the north and south directions respectively, exclude the areas covered by the projection, and the remaining areas are the fertilizer-deficient areas.

2. The intercropping method for efficient water and fertilizer utilization of tiger nuts and forest trees according to claim 1, characterized in that: In step one, the trees are pruned in the following way to facilitate subsequent work: Prune all overgrown branches within the working height range of the tiger nuts; Prune the lateral branches between two adjacent trees in the same planting row so that in the midday remote sensing image, the images of two adjacent trees are separated by the bare ground illuminated by sunlight.

3. The intercropping method for efficient water and fertilizer utilization of tiger nuts and forest trees according to claim 1, characterized in that: In step two, tiger nuts are sown from late April to mid-May. After sowing, irrigation is carried out every 7-10 days until mid-to-late August. Each irrigation lasts 4-6 hours. During the tiger nut seedling stage, tillering stage, tuber formation stage, and tuber enlargement stage, the corresponding water-soluble fertilizers are applied.

4. The intercropping method for efficient water and fertilizer utilization of tiger nuts and forest trees according to claim 1, characterized in that: In step three, the drip irrigation network for trees is managed in blocks, and the blocks are the same as those for tiger nuts. Each block of the drip irrigation network for trees is supplied with water by a unique corresponding drip irrigation branch pipe. If the drip irrigation branch pipes for trees and tiger nuts draw water from the same ground stake, a valve is installed at the inlet of the drip irrigation branch pipe. Two forest drip irrigation pipes are installed in each row of trees, with drippers on the drip irrigation pipes arranged around the trees, and at least four drippers are installed around each tree.

5. The intercropping method for efficient water and fertilizer utilization of tiger nuts and forest trees according to claim 1, characterized in that: In step four, multispectral and visible light photos of the area where the tiger nuts are located are obtained through drone aerial photography, and the images to be analyzed are obtained based on these. The element characterized by nutrient deficiency is nitrogen; The remote sensing symptoms were low NDVI and GNDVI indices in tiger nut plants. The specific symptoms are that the plant height is lower than the surrounding area, while the degree of ground exposure is higher than the surrounding area.

6. The intercropping method for efficient water and fertilizer utilization of tiger nuts and forest trees according to claim 5, characterized in that: In step three, a section of the drip irrigation network that is close to the water source and free from tree shade is selected and recorded as the characteristic section. The NDVI index and GNDVI index of the tiger pea plants in the characteristic section are monitored and recorded as the characteristic NDVI index and characteristic GNDVI index, respectively. The remote sensing symptoms are defined as tiger nut plants having an NDVI index lower than 10% of the characteristic NDVI index or lower than 0.6, and a GNDVI index lower than 10% of the characteristic GNDVI index or lower than 0.

6.

7. The intercropping method for efficient water and fertilizer utilization of tiger nuts and forest trees according to claim 1, characterized in that: In step five, before applying fertilizer, check the individual symptoms of tiger pea plants along the drip irrigation branch pipes of the nutrient-deficient sections, and tie the drip irrigation tapes of the tiger pea plants within the irrigation area that are not nutrient-deficient. After applying fertilizer, restore the temporary fertilizer inlet to its original state and remove the bypass fertilizer tank, and then untie the drip irrigation tapes.

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