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20 April 2017, Volume 38 Issue 04

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Using Path Analysis to Identify Impacting Factors of Evapotranspiration at Different Time Scales in Farmland

ZHANG Xue-song, YAN Yi-lan, HU Zheng-hua

2017, 38(04):  201-210.  doi:10.3969/j.issn.1000-6362.2017.04.001

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Based on the data measured by large-scale weighing lysimeter and agricultural meteorological observation from 2011 to 2015, the distributing characteristics of evapotranspiration at different time scales in winter wheat farmland were analyzed, and the impacting factors were identified by path analysis. The results showed that the change of evapotranspiration displayed a downward-parabola pattern with a single peak at hourly scale, and the maximum evapotranspiration was from 0.9mm·h-1 to 1.1 mm·h-1 and the cumulative value throughout the day was from 7.0mm to 9.1mm on the typical sunny day during flowering-milky stage within 4 years. The mean annual evapotranspiration was 385.4mm, the mean diurnal evapotranspiration was 2.6mm·d-1 and the maximum value was 11.0mm·d-1 during the whole winter wheat growing period. The daily scale variation of evapotranspiration at early growing stage was greater than that at later stage. During the growing season, the evapotranspiration rate was lower during the sowing to turning-green period with an average of 1.1mm·d-1 than that of 4.2mm·d-1 after turning-green period. (2) The impacting factors of evapotranspiration at different time scales mainly included net radiation (Rn), saturated vapor pressure deficit (VPD), ground temperature (Tg0) and soil water content at 20cm (SW20). At hourly scale, VPD had the largest direct effect on evapotranspiration variation on the typical sunny day. Rn and Tg0 affected evapotranspiration indirectly via Rn. The ranking of the decision coefficient of every factor was VPD＞Tg0＞Rn. At daily scale, Rn, as the most critical factor, had the largest direct impact on evapotranspiration, while VPD had the largest indirect influence. VPD and Tg0 affected evapotranspiration indirectly via Rn and the indirect negative influence of SW20 was imposed by Tg0 path. The ranking of the decision coefficient of impacting factors was Rn＞VPD＞Tg0＞SW20.At the whole growing season scale, Tg0 and Rn were the only two most important factors with direct influence and could drive evapotranspiration change. The decision coefficient indicated that Tg0 could significantly increase the variation of evapotranspiration more than Rn.

Root Zone Temperature and Heat Flux Changes of Tomato Cultivated on SRSCs with Different Plastic Films Covering in Chinese Solar Greenhouse

FU Guo-hai，LIU Wen-ke

2017, 38(04):  211-220.  doi:10.3969/j.issn.1000-6362.2017.04.002

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Based on soil ridged substrate-embedded cultivated method (SRSC), the authors further alleviate the problem of high temperature stress in the process of substrate cultivation and further promote the growth of tomato seedlings in summer in Chinese solar greenhouse by studying on the effect of heat insulation and cooling effect of different plastic films. A pot experiment was carried out to test changes of temperature and heat flux and record growth of tomato plants. In this study, five treatments were set, including soil ridge covered by transparent film as control (CK), SRSC ridge covered by transparent film (TM), SRSC ridge covered by black film (HM), SRSC ridge covered by ordinary reflective film (PF), SRSC ridge covered by highly reflective film (QF). Results showed that SRSC method could decrease temperatures under plastic film and in root zone compared with CK before planting, and temperatures under plastic film and in root zone of QF were the lowest. Average maximum temperatures under plastic film and in root zone of QF were 12.78 and 9.73℃ cooler than CK, and the average daytime temperatures under plastic film and in the root zone of QF were 7.88 and 6.16℃ cooler than CK, and QF had the best effects on the decrease of temperatures. After planting, changes of temperature under plastic film and in the root zone of each treatment were consistent with the former, and QF had?the best effects on the decrease of temperatures in this stage, and average maximum temperatures under plastic film and in root zone of QF were 8.96 and 8.97℃ cooler than CK, and average daytime temperatures under plastic film and in root zone of QF were 6.02 and 5.47℃ cooler than CK. But the cooling effect of QF was worse than the previous period caused by high environmental temperature. On the root zone cooling effect, cooling capacity followed by QF>PF>HM>TM>CK, respectively. At night, temperatures under plastic film and in root zone decreased to a suitable level. Root zone temperature and heat number has no direct relationship, and root zone heat transfer and root zone temperature of QF were the most slow in all treatments, and that suggested that slower of heat transfer, cooler the root zone temperature. Plant height and stem diameter of tomatoes cultivated on PF and QF were both higher than that of CK, and the effect of QF was the most significant. The biomass of tomato seedlings was gradually increased with effect of heat insulation and cooling increasing, and the fresh and dry shoot and root weight of QF was the best, and the growth of tomato seedlings was the best. In a word, SRSC covered highly reflective film can improve the ridge root zone heat effect and conducive to the growth of tomato seedlings compared with SRSC with other types of plastic film covering.

Ventilation Simulation in a Large-scale Greenhouse Based on CFD

ZHANG Fang, FANG Hui, YANG Qi-chang, CHENG Rui-feng, ZHANG Yi, KE Xing-lin, LU Wei, LIU Huan

2017, 38(04):  221-229.  doi:10.3969/j.issn.1000-6362.2017.04.003

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To solve the problem that the inner available space of the traditional Chinese solar greenhouse is usually small, a new-type large-scale greenhouse which was tunnel type and had a wide span with steel frame and south-north orientation was designed. The?distribution?of airflow and temperature patterns, the effect of vent openings under different outdoor wind speed conditions on airflow and temperature patterns in a naturally ventilated large-scale greenhouse were studied. Firstly, simulation model of the airflow and temperature patterns in a naturally ventilated large-scale greenhouse was established by means of three-dimensional computational fluid dynamics (CFD). Secondly, the model was validated via the comparison with the field experimental results at the same locations where 13 temperature sensors were installed under the typical sunny day when the vent opening degree was 50%. The comparison between simulations and measurements showed that the absolute error was within 2.8℃, the square error was within 1.6℃, the maximum relative error was less than 9.9% and the average relative error was around 4.1%. An agreement existed between simulated and experimental results. Finally, the model which was validated was used to study the effect of vent opening degree (25%, 50%, 75% and 100%) under different outdoor wind speed (1, 2, 3, 4m·s-1) conditions on airflow and temperature patterns. The results showed that, the average temperature of the top of the greenhouse was higher than the bottom of the greenhouse, and the colder air outside went into the greenhouse from the west side vent, so the average temperature of the west of the greenhouse was lower than the east of the greenhouse. From south to north, the average airflow rates decreased in the greenhouse. Because of the west and east vents, the average air velocity in the center of greenhouse was lower than the side. When both top and side vents full opened, the airflow in greenhouse was relatively low. Temperature distribution was uniform in the large-scale greenhouse when the vent opening degree was 100%. The outdoor wind speed had a significant positive correlation with the ventilation rate when vent opening degree was kept constant. For the purpose of cooling, the optimum vent opening degree was 75%-100%. If the temperature of the greenhouse was suitable for crop growth and the outdoor wind speed was faster than about 3m·s-1, the optimum vent opening degree should be less than 75%.

Effects of Spraying Lanthanum in Early Flowering Stage on Photosynthetic Characters and Chlorophyll Fluorescence Parameters of Medicago sativa under Enhanced UV-B Radiation

WANG Wei, WANG Yan, LIANG Bian-bian, ZHAO Tian-hong, TIAN Rong-rong, WU Hong-yan

2017, 38(04):  230-239.  doi:10.3969/j.issn.1000-6362.2017.04.004

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Taking Medicago sativa as an experimental material, the experiment was implemented in the plastic greenhouse in Shenyang, April-October, 2015. Lanthanum (La) was sprayed in the early flowering stage, conducted nine treatments, which were CK (no UV-B radiation and La treatment), T1 (only subjecting to 5% UV-B radiation), T13 (subjecting 5% UV-B radiation and spraying 30mg·L-1 La), T16 (subjecting 5% UV-B radiation and spraying 60mg·L-1 La ), T19 (subjecting 5% UV-B radiation and spraying 90mg·L-1 La), T2 (only subjecting to 10% UV-B radiation), T23 (subjecting 10% UV-B radiation and spraying 30mg·L-1 La), T26 (subjecting 10% UV-B radiation and spraying 60mg·L-1 La ), and T29 (subjecting 10% UV-B radiation and spraying 90mg·L-1 La), to reveal the effects of spraying La in early flowering stages on physiological characteristics of Medicago sativa under enhanced UV-B radiation. The results showed that, with the increased of UV-B radiation, Chla, Chlb, A, E, gs, Ci, Fv/Fm, qP and NPQ declined compared with those of CK, so it was concluded that UV-B radiation can reduce the photosynthetic characters of Medicago sativa leaves; On the contrary, with sprayed the concentrations of La (sprayed the 30mg·L-1 of La under UV-B radiation enhanced by 5%, sprayed the 60mg·L-1 of La under UV-B radiation enhanced by 10%), the above indicators significantly enhanced by 12.91%, 11.93%, 22.22%, 22.25%, 96.26%, 7.10%, 12.85%, 11.55%, 123.66% and 140.81%, 63.12%, 37.90%, 22.80%, 108.28%, 6.08%, 3.81%, 37.95%, 199.68%, respectively. Results showed that sprayed La can alleviate the damage of photosynthetic characters of Medicago sativa leaves under UV-B radiation. In addition, the content of soluble sugar and soluble protein was also increased in the growth period, it demonstrated that UV-B radiation and La could promote the synthesis of sugar and protein of Medicago sativa leaves.

Chilling Injury Risk of Early Rice in Centralized Seedling Mode in Jingzhou

LIU Kai-wen, WANG Hai-rong, ZHU Jian-qiang, SU Rong-rui, GAO Hua-dong

2017, 38(04):  240-247.  doi:10.3969/j.issn.1000-6362.2017.04.005

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According to investigations of early rice seedling modes in Jingzhou, chilling injury was usually occurred, and initiated by yield reduction. Based on the average daily temperature observations of 6 national meteorological stations, and development period observations between 1981 and 2014, the average effective accumulated temperature of each stage was counted under the traditional seedling mode(TS). Furthermore, two kinds of centralized greenhouse seedling modes, which were 10 days(CS-10) or 20 days(CS-20) earlier than TS, were set to analyze the change rules of chilling accumulative temperature(accumulated value of the difference between critical temperature of chilling injury and average daily temperature in each stage) and the chilling injury characteristics of weibull probability density distribution. The results indicated that, compared with TS mode, advanced with seedling date, the beginning date of transplanting-tillering stage, panicle differentiation, flowering, grain filling and maturation stage were respectively 14d, 10d, 8d, 11d and 7d earlier in CS-10 mode, and 24d, 15d, 11d, 17d, 10d earlier in CS-20 mode. In addition, in the early stage(transplanting-tillering stage and panicle differentiation stage), the probability of mild chilling injury(0＜H≤10℃·d, chilling accumulated temperature) reduced, and increased in the later stage(flowering stage and grain filling stage). Nevertheless, moderate and above chilling injury(H＞10℃·d) was increased rapidly in the transplanting-tillering stage and panicle differentiation stage, which were separately reached 14.7%, 49.7% in the CS-10 mode, and 57.1%, 71.7% in the CS-20 mode. For reducing the risk of chilling injury, the suitable sowing date of centralized seedling mode in Jingzhou should be later than March 25th, which was 7 days earlier than TS mode.

Effect of Seed Coating Agents on External Morphology and Ultrastructure of Cotton Radicles and Seedlings under Low Temperature Treatments

LEI Bin, LI Jin, DUAN Liu-sheng, ZHANG Peng-zhong, LI Jie, TAN Wei-ming

2017, 38(04):  248-256.  doi:10.3969/j.issn.1000-6362.2017.04.006

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In this study, ‘Xinluzhong 54’ cotton seeds coated with three different homemade seed coating agents (Mian 1, Mian 2 and Mian 3) were sown in plastic nutrition boxes and cultured at 25℃. On the 4th and 7th days when cotton seed radicles had grown into cotton seedlings, the coated cotton seeds were exposed to four low-temperature treatments at 5℃, 10℃, 15℃ and 20℃. The uncoated cotton seeds exposed to the same low-temperature treatments served as the control group (CK). The external morphologies and ultrastructures of the cotton radicles and seedlings were observed at 24 hours after low-temperature exposure to explore the effects of seed coating agents on improving the cold resistance of cotton by simulating the late spring cold climate in Xinjiang Province. The results showed that there was no significant difference between the coated and uncoated treatments at 20℃. Cotton seeds germinated normally at the germination rate of 92.24%-95.51%. The radicle growth lengths of the three different seed coating agents were 3.66-3.81cm, and the cotton seedlings grew well with dark green leaves and erect stems. The mitochondrial structure of radicle cells was complete, and the structures of mitochondria and chloroplasts in mesophyll cells were normal. Compared with the control, the seed germination rate of the coated seeds increased by 4.45-6.98 percentage points at 15℃. The radicle growth speed declined, but the growth amount increased by 25.27%-36.05%. The cotton seedlings grew well with dark green leaves and erect stems. Mitochondria cristae in radicle cells were clear. In addition, the structures of chloroplasts and mitochondria in mesophyll cells were clear, which were significantly better than after CK treatment. Cotton seed germination was inhibited at 10℃, but the germination rate of the coated seeds increased by 0.73-4.25 percentage points compared with that of the uncoated seeds. Radicle growth was limited, and the leaves were dark green. Approximately 19.15%-42.55% of the seedling leaves drooped and wilted. There were more mitochondria and endoplasmic reticula in the radicle cells of seedlings compared with that in seedlings from uncoated seeds. The outline of the chloroplast in mesophyll cells was clear with few inclusions. The Main 1 treatment was better than the other treatments. The cotton germination rate after different treatments was lower than 50.00% at 5℃. The seedling leaves in the uncoated group lost color and wilted with a wilting rate of 74.47%, whereas that of the coated treatment group was 60.42%-67.45%. The mitochondrial structure in the radicle cells was clear, and the mitochondrial structure in mesophyll cells was normal, while chloroplasts expanded into a spherical shape. The grana lamellar structure disintegrated, inclusions were turbid, and no significant difference was observed between coated and uncoated treatment groups. Our results show that seed coating agents can stimulate cotton seed germination, increase the seed germination rate and radicle growth speed under low-temperature treatments, protect the external morphology and cell ultrastructure stability of cotton radicles and seedlings, maintain normal growth, and enhance the ability of seedlings to resist damage from the low-temperature climate.

Regionalization of Climatic Suitability for Major Kiwifruit Cultivars in China

QU Zhen-jiang, ZHOU Guang-sheng

2017, 38(04):  257-266.  doi:10.3969/j.issn.1000-6362.2017.04.007

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Based on the information of geographical plantation for kiwifruits (Actinidia deliciosa and Actinidia chinensis) in 171 counties in the Chinese mainland in 2013, and the meteorological data of 2084 stations from 1981 to 2010, 9 factors that might have potential influence on the distribution of the kiwifruit plantation were selected considering the combination of its physiological demand and quality formation. And the relationship between potential distribution of the kiwifruit plantation and climatic factors was established by using the maximum entropy (MaxEnt) model via ArcGIS. Then, the dominant climatic factors and their appropriate ranges that affect the distribution of kiwifruit plantation were investigated. And the region of climatic suitability for the kiwifruit plantation was divided basing on presence probability. The results showed that the dominant climatic factors affecting the distribution of the kiwifruit plantation in China were the coldest monthly mean temperature, annual sunshine hours, annual relative humidity, hottest monthly mean temperature, frost-free duration and precipitation, the frost-free duration, and the coldest average temperature. The suitable region of the kiwifruit was mainly located within east of 102°E and 24-36°N. Among them, the most suitable region included mainly the middle and eastern parts of Sichuan, mid-western parts of Chongqing, Guizhou Plateau, the southwest of Hunan and the north of Qinling Mountains. Hunan, Hubei and Chongqing were the more suitable region that has higher climate adaptability for further development. The north of Qinling Mountain and northwest Sichuan, where were widely cultivated up to data, should be controlled to a proper scale and enhanced the quality and benefit of the kiwifruit plantation.