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20 July 2020, Volume 41 Issue 07

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 Characteristics of Temperature Sensitivity of Soil Respiration in a Summer Maize- Winter Wheat Rotation Cropland

LU Chuang, HU Hai-tang, HUAI He-ju, CHENG Cheng, TIAN Yu-jie, LI Cun-jun

2020, 41(07):  403-412.  doi:10.3969/j.issn.1000-6362.2020.07.001

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 The temperature sensitivity of soil respiration (Q10) is often used in exponential models to predict or interpolate soil respiration (RS). However, beyond temperature, Q10 can be influenced by factors such as soil water content, substrate availability and microbial activity, so that Q10 may vary with seasonally fluctuating conditions and processes, and differences between Q10 derived from different time scales may exist. In order to understand the variation of RS and Q10 on croplands soils, RS was measured continuously for half an hour by a multichannel automatic soil CO2 efflux system (Li-8150, USA) in a summer maize-winter wheat double cropping system from June 2018 to June 2019 in Beijing suburb. Summer maize growth season was divided into three stages (2018-06-22—2018-07-15, 2018-07-16—2018-08-15, 2018-08-16—2018-09-17), and winter wheat growth season were decomposed into five stages (2018-10-01—2018-11-22, 2018-11-23—2019-02-25, 2018-02-26—2019-04-10, 2019-04-11—2019-05-13, 2019-05-14—2019-06-17) according to the phenology. Seasonal variation of RS and Q10 values at different crop growth stages were studied, respectively, and their responses to the influence factors including soil temperature at 5cm depth, soil water content, leaf area index and aboveground biomass were analyzed in this article. Moreover, diurnal dynamics of soil respiration rate at different growth state were calculated. The main results are showed as follow: (1) the diurnal variation of the soil respiration rates in different growth stages appeared as a single-peak curve as well as the soil temperature. But soil temperature often peaked later than the half-hourly soil respiration rates at the wheat growth season. The lag time of soil temperature for each growth stages were 4.5, 5.0, 5.0, 2.5, 0.5h. The relationships between diurnal RS and soil temperature showed a clockwise nearly elliptic curve. (2) Q10 exhibited a strong seasonal variation. At seedling, jointing to tasseling, and flowering to mature stage of summer maize, Q10 values were 2.27, 6.13 and 1.28 respectively. During the whole growth period of summer maize, soil water content ranged from 19.52% to 45.43%, and an quadric curve downwards of soil moisture could explain 50% of variation for RS (P<0.05), with the threshold value being 27.84%, which came to about 83.83% of field capacity. Exponential models of soil temperature could only explain 3% of variation for RS (P>0.05), and the Q10 value obtaining from whole growth stage of summer maize was 1.29. (3) Q10 values at different growth stages of winter wheat were 4.17, 8.41, 6.57, 2.53, 1.92, respectively, negatively correlated with soil temperature (P<0.05). At the scale of whole winter wheat season, Q10 value reached to 2.50, and soil temperature was a major factor influencing RS, which explained 88% of the variation for RS (P<0.01). On one-year scale, soil temperature and soil water content explained 54% (P<0.01), 28% (P<0.05) of the variation for RS, and Q10 was 1.72. In consideration of the difference of Q10 at each stage, we found that RS may decoupled from soil temperature at higher soil water content which were closed to field capacity, influencing the applicability of Q10 value. Additionally, time scale should be ascertained with caution, for the Q10 values obtained from inappropriate scales may underestimate or overestimate the future soil respiration rates under the conditions of global warming.

 Microclimate Environment Test for Wide-span Plastic Greenhouse with External Thermal Insulation

DONG Xiao-xing, HUANG Song, YU Lu-ming, LI Sheng-li

2020, 41(07):  413-422.  doi:10.3969/j.issn.1000-6362.2020.07.002

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 Agricultural facilities will be improved to be more large-scale, simplified, lighter and easier to be assembled as facility agriculture production moves towards mechanization and intensification. As the most important type of horticultural facility in northern China, solar greenhouses are mainly used for the annual production of warm-season vegetables. However, the span of solar greenhouses are mostly 8-10m, and the back wall are mainly made of clay or brick. All these result in the small cultivation area, low efficiency of wall construction and low utilization of land. In addition, plastic greenhouses have poor thermal insulation property and cannot be used in winter in northern China. Therefore, neither of these two common facilities can meet the production requirements. The large-span plastic greenhouses with external thermal insulation property are designed and put into practice. The span is extended from 8-12m to 20m and external thermal insulation system is equipped. They have a north-south orientation, steel structure skeleton and bolt connection, with the advantages of strong temperature buffering capacity, high land utilization rate, low production cost and high degree of assembly. However, the internal microclimate environment is not clear, that makes it impossible to produce scientifically. In order to find out the microclimate environment in the large-span external thermal insulation plastic greenhouse and effectively guide the cultivation. The microclimate environment, such as temperature, ground temperature, relative humidity and light conditions inside and outside the greenhouse had been monitored annually. And the application prospect of the new greenhouse had been discussed. The calculation showed that new plastic greenhouse had good heat-insulating property in winter. The average temperature indoor in January was 10.9℃, and the average ground temperature indoor was 12.7℃. The lowest indoor temperature was 6.8℃, and the lowest indoor ground temperature was 12.3℃, which were 8.9℃ and 9.5℃ higher than the open ground. In summer, the air and ground temperature in the shed was higher than the open field, but the raise of air temperature was smaller, and the ground temperature was slightly larger. The relative humidity in the shed was large, which was close to saturation in the day and night during November to following February. The light transmittance of the shed was 51.8%-67.5% in sunny days. There was a moving shadow band of 2.0-3.5m wide. The study showed that microclimate environment in the new greenhouse could basically meet the requirements of warm-season vegetables. In some areas of Zhumadian city, large-span external thermal insulation plastic greenhouses could basically meet the environmental conditions required for thermophilic fruits and vegetables, and could be used for their annual production.

 Simulation and Distribution of Flower Stage in Main Production Areas of Fuji Apple in China

BAI Qin-feng, HUO Zhi-guo, WANG Jing-hong, LIANG Yi

2020, 41(07):  423-435.  doi:10.3969/j.issn.1000-6362.2020.07.003

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 In the five main production areas of Fuji apple in China, Fushan(in Shandong province and belongs to the Around Bohai bay production area), Sanmenxia(in Henan province and belongs to the old Yellow River production area), Xifeng(in Gansu province and belongs to the Loess Plateau production area), Zhaotong(in Yunnan province and belongs to the southwest cold highland production area), Akesu(in Xinjiang Uygur Autonomous Region and belongs to the Xinjiang production area)were selected as representative sites. Using SPSS statistical software, the meteorological factors affecting Fuji apple flowering were analyzed and screened, and the flowering simulation models of Fuji apple were constructed. The mean absolute error (MAE) and graded weighted full score method were used to test the models, and the epitaxial test of the models were carried out by using the phenological observation data of 12 sites around the representative sites. On this basis, using the meteorological data of 416 sites in China's apple production areas from 1981 to 2018, the first and terminal flower of Fuji apple were simulated year by year. The results showed that, the full scores of single site tested were 66.7%-100.0%, the mean absolute errors (MAE) were 0.4-3.4d, and the MAE of epitaxial tests were 1.2?5.1d. From 1981 to 2018, the flower stages of Fuji apple in China have three characteristics: large time difference, early change trend, and the dividing point of early change around 1997. Zhaotong’s average first flower was the earliest, at 82.0d (March 21), Xifeng’s average first flower was the latest, at the 109.0d (April 19), with a difference of 27.0d. Zhaotong’s average terminal flower was the earliest too, at 101.0d (April 11), Xifeng’s average terminal flower was the latest too, at 119.0d (April 29), with a difference of 18.0 days. The early change range of Fuji Apple's first flower, in Zhaotong was 4.5d·10y-1, which was the largest, and in Fushan was 1.6d·10y-1, which was the smallest. The early change range of Fuji apple's terminal flower, in Zhaotong was 3.8d·10y-1, which was the largest too, and in Akesu was 1.2d·10y-1, which was the smallest. On the whole, the spatial distribution characteristics of the flower stage of Fuji apple in China were gradually postponed from south to north. In the southwest cold highland production area, the average first flower was before 90 days (March 31) and the average terminal flower was before 105 days (April 15). In the old Yellow River production area, the average first flower was between 91-100d (April 1 to 10), and the average terminal flower was between 106-110d (April 16-20). In the Loess Plateau production area, the average first flower was between 101-110d (April 11 to 20), and the average terminal flower was between 111-120d (April 21 to 30). In the Xinjiang production area, the average first flower was between 96-115d (April 6 to 25), and the average terminal flower was between 106-125d (April 16 to May 5).In the Around Bohai bay production area, the average first flower was between 101-120d (April 11 to 30), and the average terminal flower was between 111-130d (April 21 to May 10).

 Improvement Effects of Red and Blue LED Continuous Lighting before Harvest on Quality of Hydroponic Lettuce

ZHANG Yu-bin, LIU Wen-ke, YANG Qi-chang, ZHA Ling-yan, ZHOU Cheng-bo, SHAO Ming-jie, Wang Qi, LI Bao-shi, WU Qi-bao

2020, 41(07):  436-445.  doi:10.3969/j.issn.1000-6362.2020.07.004

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 Plant factory is the most advanced production facility in the field of facility horticulture. It could make the best use of water, fertilizer, electric energy, and other resources to meet the needs of plant growth and realize high-yield and high-quality leaf vegetable production. In theory, plant factories could produce vegetable products with rich nutrient elements according to people's wishes. It was particularly important to improve the yield and quality of vegetables by regulating the light environment under certain conditions of nutrition supply. It was found that the yield and quality of lettuce could be significantly improved by short-term red and blue LED light before harvest. In a plant factory with the controllable environment, the red and blue LED light of different light intensity was used to light continuously (CL) 72 hours before harvest, and "Italian bolting resistant" lettuce (Lactuca sativa L.) was used as the experimental material. The effects of irradiation on the contents of C, N, P, K, Ca, Mg, Fe, Mg, Cu, and Zn in lettuce leaves were studied. After the lettuce was planted, it was continuously cultivated for 17 days under the light period of 6：00-22：00. The red and blue light intensity in the culture stage were all 150μmol·m-2·s-1. CL treatment with different light intensities for 72h was started from the 18th day after transplantation. The light intensity of CL was 100, 150, 200, 300 and 500μmol·m-2·s-1 (represented by CL100, CL150, CL200, CL300 and CL500). And set a growth light intensity of 150μmol·m-2·s-1 during the whole growth period and a light period of 6：00-22：00 as control treatment (CK). In the experiment, samples were taken at the beginning and the end of concentrated continuous irradiation and 4 lettuce plants were randomly selected as repeated samples in each treatment, then dried and ground into powder. The contents of K, P, Ca, Mg, Fe, Mn, Cu and Zn were determined by atomic absorption spectrophotometer and inductively coupled plasma mass spectrometer, and the contents of N and C were determined by combustion isotope analysis. The results showed that the fresh weight and dry weight of lettuce increased with the increase of CL light intensity, and reached the maximum value respectively at CL500. The content of P, K, Ca and Mg in the dry matter of lettuce was the highest under the treatment of CK. After continuous irradiation with LED red and blue light for the last 72 hours before harvest, the content of C in lettuce dry matter increased with the increase of CL light intensity. The total amount of C, N, Fe and Zn in lettuce dry matter increased with the increase of CL light intensity, which was the highest under CL500 treatment. The total amount of P, K, Mg and Cu showed a trend of increasing first and then decreasing with the increase of CL light intensity. Under the treatment of CL200, the total amount of P and K was the highest; under the treatment of CL300, the total amount of Mg and Cu was the highest. The light intensity of CL has no significant effect on the total amount of Ca and Mg. Therefore, continuous red and blue LED light could be applied before harvesting for improving the quality of lettuce or producing functional vegetables rich in some nutrients.

 Classification of Drought Degree during Vegetative Growth Stage of Maize Based on Threshold Indicator Taxa Analysis (TITAN)

MA Xue-yan,ZHOU Guang-sheng, LI Gen

2020, 41(07):  446-458.  doi:10.3969/j.issn.1000-6362.2020.07.005

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 Drought was a major disaster that limited the growth and yield of crops worldwide. The loss of crop output caused by drought even exceeds the sum of the losses caused by all other factors, and was the most important factor threatening world food security. The influence of drought on crops was closely related to drought intensity, drought duration and the development stage of crops. It was of great significance for efficient agricultural drought prevention and drought relief to accurately assess the drought damage degree of crops and scientifically classify the drought damage levels of crops. Existing methods on crop drought assessment and grading were mostly based on yield reduction. However, yield reduction reflected the drought damage degree of the entire growth period of crop, which could not be applied to the assessment of crop drought damage degree during certain development period, restricting timely formulation and implementation of disaster prevention and mitigation measures. At present, the assessment and research on the progress of drought were generally based on one or several environmental indicators, such as precipitation, soil moisture, water deficit index, etc., or based on some single growth indicator, such as biomass. On the one hand, drought had a cumulative effect on crops, and the environmental indicators observed at that time could not necessarily reflect current growth state and damage degree of crops. On the other hand, a single growth indicator could not accurately reflect the overall growth status of crops. Since different growth indicators may have different response thresholds to drought degree, different conclusions may be drawn when grading and evaluating the drought degree of crops based on the response thresholds of different growth indicators to drought degree. Therefore, this study intended to investigate the responses of maize growth indicators to drought of different intensity and duration during its vegetative growth period (from the 3-leaf stage to jointing stage) based on a field plot experiment performed in 2014, and put forward a new way to accurately evaluating and classifying drought damage degree of maize based on response synchronicity of multiple growth indicators. In the field plot experiment, six different irrigations were performed during the three-leaf period of maize with the irrigation amounts (named treatments T1-T6) were 150, 120, 90, 60, 30, and 10mm, respectively, equivalent to 100%, 80%, 60%, 40%, 20% and 7% of the local average precipitation in July (150mm), respectively. No extra irrigation was performed thereafter. Precipitation was blocked completely by the auto-rain-shelter during the entire growth period. Then, six continuous drought processes of different initial soil moisture gradients were formed as time proceeded. Observations on soil water content, maize growth indicators were performed every 7-day after the irrigation treatments. Based on the observation data, the response regularity of maize morphological (plant height and leaf area) and biomass (stem dry mass, leaf dry mass, and total dry mass) indicators to the drought degree (D) was studied. By using of Threshold Indicator Taxa Analysis method (TITAN), the response turning points of growth indicators of maize's to drought degree were determined, and based on the response synchronicity of these growth indicators, the response turning point of maize plant level to drought degree was identified. Then the drought degree was divided into 4 levels according to these turning points. The results showed that, when 0＜D≤0.07, maize was affected by light drought, and the average decrease of maize growth indicators was only1.2%-3.0%; when 0.07＜D≤0.47, maize was affected by medium drought with an average decrease of leaf area of 15.9%, plant height of 8.6%, stem dry mass, leaf dry mass, and total dry mass of 18.8%, 15.4% and 12.4%, respectively; when 0.47＜D≤0.73, maize was affected by severe drought with an average decrease of leaf area of 37.8%, plant height of 16.9%, stem dry mass, leaf dry mass and total dry mass of 43.3%, 45.2% and 28.9%, respectively; when 0.73＜D≤1, maize was affected by extreme drought, with an average decrease of leaf area of 83.6%, plant height of 53.3%, leaf dry mass and stem dry mass above 90%, and total dry weight of 87.0%. The results would provide a method and basis for quantitative classification and evaluation of drought damage degree of crops.

 Temporal and Spatial Variations of Meteorological Drought and Drought Risk Analysis in Hedong Area of Gansu Province

HUANG Hao, ZHANG Bo, MA Shang-qian, MA Bin, CUI Yan-qiang, WANG Xiao-dan, MA Chun-rong, CHEN Kun-quan, ZHANG Ting

2020, 41(07):  459-469.  doi:10.3969/j.issn.1000-6362.2020.07.006

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 Meteorological drought in rain-fed agricultural areas has always been the focus of attention, especially for the area at the junction of monsoon and arid areas with less precipitation. Understanding the characteristics of meteorological drought is particularly important for agricultural production. Based on the monthly climate data of 60 meteorological stations from 1988 to 2017 in Hedong, Gansu，linear tendency estimation, Mann-Kendall abrupt change detection, wavelet power spectrum and hurst index were used to analyze the spatio temporal changes, abrupt change, periods of change and the continuity of trends of the three drought indicators: occurrence times, intensity and duration of drought events in Hedong area. The risk of meteorological drought in different time periods in Hedong area was shown by the drought risk index. The results showed that, firstly, as for the interannual change, the occurrence times, intensity and duration of drought events in Hedong area increased significantly (P < 0.05) from 1988 to 2017, and t-1, 0.61level·10y-1 and 0.48months·10y-1 respectively. Among all the geographic zones, increasing trend in Longzhong plateau was the most significant. Secondly, in space, the proportions of stations with significant increase in the occurrence times, intensity and duration of droughts events among the total stations were 18.0%, 31.1% and 26.2% respectively. There were only a few stations with decreasing trend in Hedong area, but the change trend of these stations was not significant (P>0.05). Thirdly, the Hovmoller chart showed that the occurrence times, intensity and duration of drought events were clustered in years and space, reflecting that the adjacent stations in Hedong area had similar spatial and temporal characteristics of drought. The Hurst index showed that in the future, the occurrence times, intensity and duration of drought events in most area of Hedong will still maintain an increasing trend, but there was only a small area with strong persistence (hurst values close to 1). What’s more, the drought indicator abrupt change appeared in 1994, the occurrence times, intensity, and duration of drought events after the abrupt change increase by 0.76 times, 2.29 level, 1.70 months, which also reflected the trend of drought in recent years. The oscillation period of drought index in Hedong area was within 6 years, reflecting that drought has a short-term fluctuation. Furthermore, the area with the highest risk of drought among all study areas within 30 years was Longzhong plateau. However, there was a significant difference in the distribution of drought risk in study areas in every 10 years. From 1988 to 1997, Hedong area faced the greatest drought risk, while from 2008 to 2017, the drought risk was relatively small.

 

2020, 41(07):  470-472.  doi:10.3969/j.issn.1000-6362.2020.07.007

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