Method for carrying out water-saving irrigation according to internal and external temperature difference of rice canopy

Abstract

The invention discloses a method for carrying out water-saving irrigation according to temperature difference inside and outside a rice canopy, which is characterized in that the temperature difference inside and outside the rice canopy is used as a diagnostic index of irrigation, and an irrigation water layer in a field is determined according to growth periods and soil types. Compared with a conventional irrigation method, the method for carrying out water-saving irrigation according to the difference value of the internal temperature and the external temperature of the rice canopy has the advantages that the number of grains per ear, the maturing rate and the thousand seed weight are remarkably increased, so that the yield is remarkably increased, and the amplification is 9.65%-14.46%. Compared with a conventional irrigation method, the method for carrying out water-saving irrigation according to the difference value of the internal temperature and the external temperature of the rice canopy can reduce the irrigation water consumption by 24.33%-26.38%, and the utilization efficiency of the irrigation water can be improved by 46.71%-53.23%.

Description

Technical Field

[0001] The present invention relates to rice planting, and in particular to a method for water-saving irrigation based on the temperature difference between the inside and outside of a rice canopy. Background Art

[0002] Rice is one of the world's most important food crops and the largest consumer of agricultural water. To address the threat of dwindling water resources, scientists and researchers at home and abroad have developed a variety of water-saving irrigation technologies. Among them, alternating wet-dry irrigation, characterized by alternating soil drying with water layer irrigation, is the most important water-saving irrigation technology for rice production in my country and around the world. Compared with conventional irrigation, which primarily relies on water layer irrigation, alternating wet-dry irrigation effectively conserves irrigation water and reduces methane emissions from rice fields. However, rice yields under alternating wet-dry irrigation vary significantly between fields, years, and regions. Yield reductions from alternating wet-dry irrigation are common. Zhang et al. (Zhang YJ et al. Agricultural Water Management, 2023, 281:108-265) analyzed 200 published papers and 3,194 observational data on alternating wetting and drying irrigation for rice worldwide. Their results showed that compared with layer irrigation, alternating wetting and drying irrigation increased water use efficiency (yield / (rice growing season precipitation + irrigation water volume)) by an average of 31%, but yield decreased by an average of 6% (95% confidence interval). Numerous studies have shown that soil drying during alternating wetting and drying irrigation is the most important factor affecting rice yield. Therefore, researchers have long sought to identify irrigation indicators that reflect rice water requirements, such as leaf water potential, leaf water content, soil water potential, soil water content, and soil water depth. Leaf water potential or leaf water content directly reflects plant water status, but these techniques require high precision and require damaging plant samples, making them difficult to apply in production. Because soil moisture conditions (such as soil water potential, soil water content, and soil water depth) are related to plant water status, some researchers use these conditions as irrigation indicators to guide irrigation. However, these water-saving irrigation techniques only consider soil moisture, ignoring the water status of aboveground plants and climatic factors such as temperature. Consequently, it is difficult to align water supply with rice's water needs, and thus to achieve a synergistic improvement in rice yield and water use efficiency.

[0003] In 2014, Zhao Yangbo et al. installed an FSR-5A infrared thermometer in the field to measure the canopy temperature of rice 1.5 m above the field surface, and recorded the meteorological temperature through a YG-QXZ small automatic weather station 50 m away from the rice field, aiming to diagnose rice water shortage by observing the canopy temperature changes [Zhao Yangbo et al. Journal of Irrigation and Drainage Machinery Engineering, 2018, 36(10): 932-936]. They believed that when the upper limit of the canopy temperature difference (canopy temperature - meteorological temperature) of direct-seeded rice and transplanted rice at noon during the jointing and heading stage reaches 1.5 ℃, and when the upper limit of the canopy temperature difference exceeds 2.4 ℃ and 2.5 ℃ respectively during the flowering and fruiting stage, the soil moisture has reached the stress level and the rice should be irrigated. The shortcomings of this method are: (1) limited applicability. At present, the plant height of most rice varieties in production at maturity is less than 120 cm. Therefore, measuring the rice canopy temperature at 1.5 m from the field surface is actually measuring the outer canopy temperature of the rice. The outer canopy temperature of the rice is mainly regulated by the meteorological temperature or atmospheric temperature. The difference between the outer canopy temperature and the meteorological temperature measured during most of the rice growth period and most of the measurement time is very small. Zhao Yangbo et al. also observed this result [Zhao Yangbo et al. Journal of Irrigation and Drainage Machinery Engineering, 2018, 36(10): 932-936]. Therefore, the applicability of this canopy temperature difference in diagnosing rice water shortage is limited. The limitation is more serious when the rice canopy height is low or in the early and middle stages of rice growth. (2) It is difficult to reflect the water status of the rice plant. Zhao Yangbo et al. observed that during the jointing and heading stage and the flowering and fruiting stage, the rice canopy temperature was higher than the meteorological temperature at noon on sunny days. Physiologically speaking, when light intensity is high and temperatures are high at noon on sunny days, C3 plants like rice experience a "midday nap" phenomenon, causing stomata to partially or completely close, reducing transpiration and increasing canopy temperature (Wu Weihua, Plant Physiology, Beijing: Science Press, 2004, pp. 170). During the jointing and booting stages and the flowering and fruiting stages, when light intensity is high and temperatures are high at noon, the midday nap phenomenon is most likely to occur. Even if rice leaves have high water content, transpiration will decrease and canopy temperature will rise. Therefore, during the jointing and booting stages and the flowering and fruiting stages, the rice canopy temperature at noon on sunny days is higher than the meteorological temperature. This canopy-air temperature difference does not reflect the moisture status of rice leaves and is difficult to use to guide irrigation. Summary of the Invention

[0004] The present invention provides a method for water-saving irrigation based on the temperature difference between the inside and outside of the rice canopy. The temperature difference between the inside and outside of the rice canopy is used as a diagnostic indicator for irrigation. The irrigation water layer in the field is determined according to the growth period and soil type. This solves the key technical problem of mismatch between water supply and rice's demand for water in rice water-saving irrigation, and the difficulty in synergistically improving rice yield and water use efficiency under water-saving irrigation conditions.

[0005] To achieve the above objectives, the present invention provides a method for water-saving irrigation based on the temperature difference between the inside and outside of the rice canopy. This method uses the temperature difference between the inside and outside of the rice canopy as an irrigation diagnostic indicator, and determines the irrigation water layer in the field based on the growth period and soil type. The details are as follows: 1. Rice transplanting greening and early tillering period (from transplanting to 18 days after transplanting): the field is naturally dried from the shallow water layer, when the temperature difference between the inside and outside of the rice canopy is ≤5.5 on a sunny day o C, cloudy ≤ 2.4 o C, the field irrigation layer of sandy soil is 2.5-3.5 cm, the field irrigation layer of loamy soil is 2.0-3.0 cm, and the field irrigation layer of clay soil is 1.5-2.5 cm; the temperature difference between the inside and outside of the rice canopy is >5.5 on sunny days o C, cloudy>2.4 o C. No irrigation in the fields.

[0006] 2. Middle tillering stage (from 19 days after transplanting to the critical leaf stage of effective tillering): the field is naturally dried from the shallow water layer, when the temperature difference between the inside and outside of the rice canopy is ≤6.2 on a sunny day o C, cloudy ≤ 2.8 o C, the field irrigation layer of sandy soil is 3.5-4.5 cm, the field irrigation layer of loamy soil is 3.0-4.0 cm, and the field irrigation layer of clay soil is 2.5-3.5 cm; the temperature difference between the inside and outside of the rice canopy is >6.2 on sunny days o C, cloudy>2.8 o C. No irrigation in the fields.

[0007] 3. Late tillering and jointing stage (from the critical leaf stage of effective tillering to the elongation of the second internode at the base): the field is naturally dried from the shallow water layer. When the temperature difference between the inside and outside of the rice canopy is ≤6.6 on a sunny day, o C, cloudy ≤ 3.1 o C, the field irrigation layer of sandy soil is 3.0-4.0 cm, the field irrigation layer of loamy soil is 2.5-3.5 cm, and the field irrigation layer of clay soil is 2.0-3.0 cm; the temperature difference between the inside and outside of the rice canopy is >6.6 on sunny days o C, cloudy>3.1 o C. No irrigation in the fields.

[0008] 4. Earing and booting stage (from the elongation of the second internode at the base to the completion of pollen grain filling): The field is naturally dried from the shallow water layer. When the temperature difference between the inside and outside of the rice canopy is ≤6.9 on a sunny day, o C, cloudy ≤ 3.3 o C, the field irrigation layer of sandy soil is 4.5-5.5 cm, the field irrigation layer of loamy soil is 4.0-5.0 cm, and the field irrigation layer of clay soil is 3.5-4.5 cm; the temperature difference between the inside and outside of the rice canopy is >6.9 on a sunny day o C, cloudy>3.3o C. No irrigation in the fields.

[0009] 5. During the heading and flowering period (from the beginning of rice ears to the complete emergence of rice ears): the field is naturally dried from the shallow water layer, when the temperature difference between the inside and outside of the rice canopy is ≤6.4 on a sunny day o C, cloudy ≤ 3.0 o C, the field irrigation layer of sandy soil is 5.0-6.0 cm, the field irrigation layer of loamy soil is 4.5-5.5 cm, and the field irrigation layer of clay soil is 4.0-5.0 cm; the temperature difference between the inside and outside of the rice canopy is >6.4 on a sunny day o C, cloudy>3.0 o C. No irrigation in the fields.

[0010] 6. In the early stage of grain filling (from the time when all rice ears emerge to 15 days after heading): the field is naturally dried by shallow water layer, when the temperature difference between the inside and outside of the rice canopy is ≤5.7 on sunny days o C, cloudy ≤ 2.9 o C, the field irrigation layer of sandy soil is 4.0-5.0 cm, the field irrigation layer of loamy soil is 3.5-4.5 cm, and the field irrigation layer of clay soil is 3.0-4.0 cm; the temperature difference between the inside and outside of the rice canopy is >5.7 on a sunny day o C, cloudy>2.9 o C. No irrigation in the fields.

[0011] 7. Mid-filling period (16 days to 28 days after heading): The field is naturally dried from the shallow water layer. When the temperature difference between the inside and outside of the rice canopy is ≤5.3 on a sunny day, the field is naturally dried from the shallow water layer. o C, cloudy ≤ 2.6 o C, the field irrigation layer of sandy soil is 3.5-4.5 cm, the field irrigation layer of loamy soil is 3.0-4.0 cm, and the field irrigation layer of clay soil is 2.5-3.5 cm; the temperature difference between the inside and outside of the rice canopy is >5.3 on sunny days o C, cloudy>2.6 o C. No irrigation in the fields.

[0012] 8. Late filling period (29 days after heading to maturity): The field is naturally dried from the shallow water layer. When the temperature difference between the inside and outside of the rice canopy is ≤4.2 on a sunny day, the rice o C, cloudy ≤ 2.2 o C, the field irrigation layer of sandy soil is 3.0-4.0 cm, the field irrigation layer of loamy soil is 2.5-3.5 cm, and the field irrigation layer of clay soil is 2.0-3.0 cm; the temperature difference between the inside and outside of the rice canopy is >4.2 on sunny days o C, cloudy>2.2 o C. No irrigation in the fields.

[0013] The outer canopy temperature and plant temperature within the canopy of rice to be measured in the present invention are measured by using a thermometer at 100 cm above the rice canopy between 10:00 and 11:00 a.m. or 3:00 and 4:00 p.m. The outer canopy temperature is measured at 100 cm above the rice canopy, and the plant temperature within the canopy is measured at 3 to 14 cm below the top of the rice canopy using an infrared thermal imager. Specifically, in the early tillering stage, the plant temperature within the canopy is measured at 3 to 5 cm below the top of the canopy; in the middle tillering stage, the plant temperature within the canopy is measured at 6 to 8 cm below the top of the canopy; from the late tillering stage to the heading stage, the plant temperature within the canopy is measured at 9 to 11 cm below the top of the canopy; and from the emergence of all rice ears to maturity, the plant temperature within the canopy is measured at 12 to 14 cm below the top of the canopy.

[0014] The calculation method of the temperature difference between the inside and outside of the rice canopy in the present invention is: the temperature difference between the inside and outside of the rice canopy = the outside canopy temperature 100 cm above the rice canopy - the plant temperature inside the canopy 3 to 14 cm below the top of the rice canopy.

[0015] The temperature difference between the inside and outside of the rice canopy at each growth stage in the present invention is a critical index value for irrigation. When the temperature difference between the inside and outside of the rice canopy is less than or equal to the set index value, the field is irrigated with water; when the temperature difference between the inside and outside of the rice canopy is greater than the set index value or on rainy days, no irrigation is performed.

[0016] The irrigation water layer mentioned in this invention refers to the height from the field surface to the field water surface, which can be directly measured with a ruler. On sunny days, the maximum value of the irrigation water layer index value is taken; on cloudy days with a maximum temperature of ≥33 o C, take the larger value of the irrigation layer index value; on cloudy days with the maximum temperature <33 o C, take the smaller value of the irrigation layer index.

[0017] The methods for determining each growth stage of rice in the present invention are well known in the industry and are described in detail in the rice chapter of various textbooks on crop cultivation.

[0018] Through the above technical solution, the present invention achieves the following beneficial effects: 1. Compared with conventional irrigation methods, water-saving irrigation based on the temperature difference between the inside and outside of the rice canopy significantly increased the number of grains per panicle, seed set rate, and 1000-grain weight, thereby significantly increasing yield by 9.65% to 14.46%. Compared with conventional irrigation methods, water-saving irrigation based on the temperature difference between the inside and outside of the rice canopy can reduce irrigation water consumption by 24.33% to 26.38% and improve irrigation water use efficiency by 46.71% to 53.23%.

[0019] 2. The main advantages of the water-saving irrigation method of the present invention are: (1) Fast: the temperature outside the canopy can be measured instantly by a thermometer, and the temperature of the plant inside the rice canopy can be measured instantly by an infrared thermal imager camera, thereby obtaining the temperature difference between the inside and outside of the rice canopy; (2) Accurate: The moisture status of the rice plant can be accurately diagnosed without destroying the plant; (3) Advanced: Compared with the previous methods of using a soil moisture tensiometer to detect soil water potential, using a soil moisture meter to determine soil moisture content, and using a polyvinyl chloride tube to detect soil water burial depth, the thermometer and infrared thermal imager camera can be used to respectively measure the temperature outside the canopy and the temperature of the plant inside the rice canopy. The technology is advanced and can be used for non-destructive detection and diagnosis of the moisture status of rice plants in large-scale rice production, if combined with drone technology or remote sensing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Figure 1 shows the outer canopy temperature (A) and the difference between the inner and outer canopy temperatures (B) measured at different times on the same day under different soil water potential conditions. Different letters above the columns indicate significant differences at the 0.05 level. In Figure B, ns indicates no significant difference at the 0.05 level. The comparison was made between the same soil water potential and different measurement times. Figure 2 The relationship between the temperature difference between the inside and outside of the rice canopy and the soil water potential at different growth stages. Asterisks (**) indicate significant correlation at the 0.01 level (n=18). Figure 3 Figure 2 shows the relationship between the temperature difference between the inside and outside of the rice canopy and the leaf water potential at different growth stages. Asterisks (**) indicate significant correlation at the 0.01 level (n=30). DETAILED DESCRIPTION

[0021] The following is a detailed description of the specific embodiments of the present invention in conjunction with the examples. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0022] The principle of the water-saving irrigation method according to the present invention based on the temperature difference between the inside and outside of the rice canopy is as follows: (1) the leaf transpiration rate reflects the moisture status of the soil and the plant: if the soil moisture supply is sufficient or the plant moisture status is good, the leaf transpiration rate is high, and vice versa, the leaf transpiration rate is low; (2) the leaf transpiration rate is closely related to the plant temperature in the canopy: if the leaf transpiration rate is high, the plant temperature in the canopy is low, and vice versa, the plant temperature in the canopy is high; (3) the canopy plant temperature is not only regulated by the leaf transpiration rate, but also by the atmospheric temperature outside the canopy, that is, under the same soil water potential, the canopy plant temperature will vary greatly due to the different atmospheric temperatures outside the canopy at different growth stages of the rice or the different observation times of the day during the same growth period ( Figure 1A). However, under the same soil water potential, the temperature difference between the inside and outside of the rice canopy did not differ significantly between different atmospheric temperatures outside the canopy or at different measurement times ( Figure 1 B); (4) At different growth stages of rice, the temperature difference between the inside and outside of the rice canopy is significantly correlated with the soil water potential and leaf water potential ( Figure 2 AF, at each growth stage of rice, the temperature difference between the inside and outside of the rice canopy is extremely significantly negatively correlated with the soil water potential, that is, the greater the temperature difference between the inside and outside of the rice canopy, the higher the soil water content; Figure 3 AF, during each growth period of rice, the temperature difference between the inside and outside of the rice canopy is extremely significantly negatively correlated with the leaf water potential, that is, the greater the temperature difference between the inside and outside of the rice canopy, the higher the leaf water content). In other words, the temperature difference between the inside and outside of the rice canopy reflects not only the soil moisture status, but also the plant moisture status, as well as factors such as atmospheric temperature. (5) Based on the relationship between the temperature difference between the inside and outside of the rice canopy and soil water potential, leaf water potential and yield formation, and based on the characteristics of rice water demand at different growth periods, the temperature difference index of the rice canopy that needs to be irrigated at each growth period of rice is determined, and irrigation is carried out according to soil type.

[0023] Example From 2023 to 2024, three soil types (sand, loam, and clay) were selected in Yangzhou and Lianyungang, and the high-yield indica / japonica hybrid rice variety Yongyou 2640 (seeds purchased from Ningbo Seed Company) was planted. Irrigation method trials were conducted. Urea was applied at a rate of 240 kg / hm2 (pure nitrogen equivalent) per soil type. 2 The application ratio is 4:1:1:1:1.5:2.5:basal fertilizer (1 day before transplanting):tillering fertilizer I (7 days after transplanting):tillering fertilizer II (15 days after transplanting):flowering-promoting fertilizer (leaf age remaining 3.0-3.5):flower-preserving fertilizer (leaf age remaining 1.0-1.5) . Superphosphate equivalent to 75 kg / hm2 of P2O5 should be applied once before transplanting for each soil type. 2 , using potassium chloride equivalent to K2O 90 kg / hm 2Potassium fertilizer is applied twice, including base fertilizer and flower-promoting fertilizer, with the ratio of the two times being 7:3. Two irrigation methods were set for each soil type: (1) conventional irrigation method (control), i.e., draining the field at the end of tillering and the beginning of jointing, maintaining a 4-5 cm water layer in the field during the rest of the growth period, and cutting off water one week before harvest; (2) water-saving irrigation based on the temperature difference between the inside and outside of the rice canopy (referred to as temperature difference irrigation method), i.e., irrigation was carried out according to the method in Table 1: starting from the time of transplanting and returning to green, the field was allowed to dry naturally from the shallow water layer until there was no water layer on the field surface, and then the outer canopy temperature 100 cm above the rice canopy was measured with a thermometer (Deli Intelligent Thermometer, Deli Group Co., Ltd., Ningbo, Zhejiang) between 10:00 and 11:00 in the morning or 3:00 and 4:00 in the afternoon, and the plant temperature inside the canopy 3-14 cm below the top of the rice canopy was measured with an infrared thermal imaging camera (Wuhan Guide Infrared Co., Ltd., Wuhan, Hubei); when measuring the canopy plant temperature, the camera lens was aimed at the rice plant and the distance between the camera lens and the target plant was 30-40 cm, the plant temperature inside the canopy can be directly read from the display window of the infrared thermal imager camera; the temperature difference between the inside and outside of the rice canopy is calculated according to the formula: the temperature difference between the inside and outside of the rice canopy = the temperature outside the canopy 100 cm above the rice canopy - the plant temperature inside the canopy 3 to 14 cm below the top of the rice canopy; when the temperature difference between the inside and outside of the rice canopy reaches the set value in Table 1, water is applied according to the soil type. The irrigation depth of each soil type is listed in Table 1. After irrigation, the soil is allowed to dry naturally. When the temperature difference between the inside and outside of the rice canopy reaches the set value in Table 1, water is applied again, and the soil is allowed to dry naturally, and this cycle is repeated. The same soil type is used as an independent experiment, and a randomized block design is adopted with a plot area of ​​30 m 2 , repeated 3 times. Except for the water management method, the other cultivation measures of temperature difference irrigation method and conventional irrigation method, such as seedling raising, transplanting, fertilization period and amount, and pest and disease control, are exactly the same.

[0024] Table 1 Water-saving irrigation methods based on the temperature difference between the inside and outside of the rice canopy

[0025] From transplanting to the stabilization of tiller number (milky stage), 20 holes were fixed in each plot to observe the number of tillers. During the soil drying period (when the soil dries naturally, the temperature difference between the inside and outside of the rice canopy reaches the index value in Table 1) and the rewatering period (there is a water layer in the field) at the beginning of panicle differentiation, heading and flowering stage, and mid-grain filling stage, the LI-6800 portable photosynthesis meter produced by LI-COR, USA, was used to measure the photosynthetic rate of the topmost expanded leaf of the rice plant. At the heading stage and maturity stage, 5 holes of rice plants were sampled in each plot to measure the non-structural carbohydrates in the stem and leaf sheath. At the rice maturity stage, 10 holes were sampled in each plot to measure the yield components (number of panicles, number of grains per panicle, fruit set rate and 1000-grain weight). The fruit set rate was determined by the water drift method. 5 m 2Actual rice harvest and yield are calculated.

[0026] The results showed that compared with the conventional irrigation method (control), the temperature difference irrigation method significantly increased the number of grains per ear, the fruit setting rate and the 1000-grain weight, thus significantly increasing the yield by 9.65% to 14.46% (Table 2). o High temperatures exceeding 10°C resulted in a significant decrease in yield compared to 2023 under the same irrigation method. However, the yield increase achieved with the temperature differential irrigation method compared to the control was consistent with the 2023 results. The yield increase trends for the temperature differential irrigation method across the three soil types were also consistent (Table 2). Compared to conventional irrigation (control), the temperature differential irrigation method reduced irrigation water use by 24.33% to 26.38% and increased irrigation water use efficiency (yield / irrigation water use) by 46.71% to 53.23% (Table 3).

[0027] Leaf photosynthetic rates measured at the beginning of panicle differentiation, heading and flowering, and mid-grain filling stages showed no significant differences between conventional irrigation (control) and differential temperature irrigation during the soil drying period (when the soil naturally dries and the temperature difference between the inside and outside of the rice canopy reaches the index values ​​in Table 1). However, during the rewatering period (when a water layer is present in the field), the leaf photosynthetic rate under differential temperature irrigation was significantly higher than that under conventional irrigation (Table 4). The differential temperature irrigation method significantly increased the tillering rate to ear formation, the translocation rate of stem and sheath substances after anthesis, and the harvest index compared to conventional irrigation (Table 5).

[0028] Table 2 Effects of irrigation methods on rice yield and its components

[0029] Note: Temperature difference irrigation refers to water-saving irrigation based on the temperature difference between the inside and outside of the rice canopy. The method is shown in Table 1.

[0030] Asterisks (*) indicate significant differences compared with conventional irrigation (control) at the 0.05 level, within the same year, soil type, and column.

[0031] Table 3 Effects of irrigation methods on rice irrigation water volume and irrigation water use efficiency

[0032] Note: Temperature difference irrigation refers to water-saving irrigation based on the temperature difference between the inside and outside of the rice canopy. The method is shown in Table 1.

[0033] Irrigation water use efficiency = rice yield / irrigation water volume.

[0034] Asterisks (*) indicate significant differences compared with conventional irrigation (control) at the 0.05 level, within the same year, soil type, and column.

[0035] Table 4 Effects of irrigation methods on photosynthetic rate of rice leaves (µmol CO2m -2 s -1 )

[0036] Note: Temperature difference irrigation refers to water-saving irrigation based on the temperature difference between the inside and outside of the rice canopy. The method is shown in Table 1.

[0037] Drying period: When the soil dries naturally, the temperature difference between the inside and outside of the rice canopy reaches the index value in Table 1; Rewatering period: There is a water layer in the field.

[0038] Asterisks (*) indicate significant differences compared with conventional irrigation (control) at the 0.05 level, within the same year, soil type, and column.

[0039] Table 5 Effects of irrigation methods on rice tillering rate, post-anthesis material translocation rate, and harvest index at maturity

[0040] Note: Temperature difference irrigation refers to water-saving irrigation based on the temperature difference between the inside and outside of the rice canopy. The method is shown in Table 1.

[0041] The tiller-to-ear rate = number of effective ears at maturity / the highest tiller number at jointing stage × 100.

[0042] Material transport rate = (the amount of non-structural carbohydrates in the stem and sheath at the heading stage - the amount of non-structural carbohydrates in the stem and sheath at the maturity stage) / the amount of non-structural carbohydrates in the stem and sheath at the heading stage × 100.

[0043] Harvest index = grain yield (dry weight) / dry weight of the aboveground plant at maturity × 100.

[0044] Asterisks (*) indicate significant differences compared with conventional irrigation (control) at the 0.05 level, within the same year, soil type, and column.

[0045] The above results show that compared with conventional irrigation methods, temperature difference irrigation can not only enhance rice material production capacity (increase leaf photosynthetic rate), but also improve material production efficiency (increase stem-to-earing rate, translocation rate of stem-sheath material after flowering, and harvest index), thereby saving water while synergistically improving yield and water use efficiency.

[0046] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0047] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0048] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for water-saving irrigation based on the temperature difference between the inside and outside of the rice canopy, characterized in that: The steps include: Measure the temperature outside the rice canopy and the plant temperature inside the canopy, calculate the temperature difference between the inside and outside of the rice canopy, and irrigate as follows: (1) During the early stages of rice transplanting and tillering, the field is naturally dried from the shallow water layer. When the temperature difference between the inside and outside of the rice canopy is ≤5.5 on a sunny day, o C, cloudy ≤ 2.4 o C, field irrigation, irrigation layer 1.5-3.5 cm; (2) In the middle of tillering, the field is naturally dried by the shallow water layer. When the temperature difference between the inside and outside of the rice canopy is ≤6.2 on a sunny day, o C, cloudy ≤ 2.8 o C, field irrigation, irrigation layer 2.5-4.5 cm; (3) During the late tillering and jointing stages, the field is naturally dried from the shallow water layer. When the temperature difference between the inside and outside of the rice canopy is ≤6.6 on a sunny day, the field is naturally dried from the shallow water layer. o C, cloudy ≤ 3.1 o C, field irrigation, irrigation layer 2.0-4.0 cm; (4) During the ear growth and booting stages, the field is naturally dried by the shallow water layer. When the temperature difference between the inside and outside of the rice canopy is ≤6.9 on a sunny day, the field is naturally dried by the shallow water layer. o C, cloudy ≤ 3.3 o C, field irrigation, irrigation layer 3.5-5.5 cm; (5) During the heading and flowering period, the field is naturally dried from the shallow water layer. When the temperature difference between the inside and outside of the rice canopy is ≤6.4 on a sunny day, the field is naturally dried from the shallow water layer. o C, cloudy ≤ 3.0 o C, field irrigation, irrigation layer 4.0-6.0 cm; (6) In the early stage of grain filling, the field is naturally dried from the shallow water layer. When the temperature difference between the inside and outside of the rice canopy is ≤5.7 on a sunny day, the field is naturally dried from the shallow water layer. o C, cloudy ≤ 2.9 o C, field irrigation, water layer 3.0–5.0 cm; (7) In the middle of grain filling, the field is naturally dried from the shallow water layer. When the temperature difference between the inside and outside of the rice canopy is ≤5.3 on a sunny day, the field is naturally dried from the shallow water layer. o C, cloudy ≤ 2.6 o C, field irrigation, irrigation layer 2.5-4.5 cm; (8) In the late filling period, the field is naturally dried from the shallow water layer. When the temperature difference between the inside and outside of the rice canopy is ≤4.2 on a sunny day, the field is naturally dried from the shallow water layer. o C, cloudy ≤ 2.2 o C, field irrigation, irrigation layer 2.0-4.0 cm.

2. The method according to claim 1, wherein The external canopy temperature was measured 100 cm above the rice canopy between 10:00 and 11:00 a.m. or 3:00 and 4:00 p.m., and the plant temperature inside the canopy was measured 3 to 14 cm below the top of the rice canopy. In the early tillering stage, the plant temperature was measured 3 to 5 cm below the top of the canopy; in the middle tillering stage, the plant temperature was measured 6 to 8 cm below the top of the canopy; from the late tillering stage to the heading stage, the plant temperature was measured 9 to 11 cm below the top of the canopy; and from the emergence of all rice ears to maturity, the plant temperature was measured 12 to 14 cm below the top of the canopy.

3. The method according to claim 1, wherein The internal and external temperature of the rice canopy = the external canopy temperature 100 cm above the rice canopy - the internal canopy plant temperature 3 to 14 cm below the top of the rice canopy.

4. The method according to claim 1, wherein On sunny days, take the maximum value of the irrigation layer index value; on cloudy days with the maximum temperature ≥33 o C, take the larger value of the irrigation layer index value; on cloudy days with the maximum temperature < 33 o C, take the smaller value of the irrigation layer index.

5. The method according to claim 1, wherein During the early stages of rice transplanting and tillering, the irrigation layer in the field should be 2.5-3.5 cm in sandy soil, 2.0-3.0 cm in loamy soil, and 1.5-2.5 cm in clay soil. In the middle tillering period, the irrigation layer in the field is 3.5-4.5 cm for sandy soil, 3.0-4.0 cm for loamy soil, and 2.5-3.5 cm for clay soil. During the late tillering and jointing stages, the irrigation layer in the field should be 3.0-4.0 cm for sandy soil, 2.5-3.5 cm for loamy soil, and 2.0-3.0 cm for clay soil. During the ear growth and booting stages, the irrigation layer in the field should be 4.5-5.5 cm for sandy soil, 4.0-5.0 cm for loamy soil, and 3.5-4.5 cm for clay soil. During the heading and flowering period, the irrigation layer of sandy soil should be 5.0-6.0 cm, that of loamy soil should be 4.5-5.5 cm, and that of clay soil should be 4.0-5.0 cm. In the early stage of grouting, the field irrigation layer of sandy soil is 4.0-5.0 cm, the field irrigation layer of loamy soil is 3.5-4.5 cm, and the field irrigation layer of clay soil is 3.0-4.0 cm; In the middle of filling period, the irrigation layer of sandy soil is 3.5-4.5 cm, the irrigation layer of loamy soil is 3.0-4.0 cm, and the irrigation layer of clay soil is 2.5-3.5 cm. In the late stage of grouting, the field irrigation layer of sandy soil is 3.0-4.0 cm, the field irrigation layer of loamy soil is 2.5-3.5 cm, and the field irrigation layer of clay soil is 2.0-3.0 cm.

Images