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20 February 2022, Volume 43 Issue 02

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A Test about Microclimate in Prefabricated Solar Greenhouse with Double Film and Double Insulation Structure Cover in Zhengzhou Region

YU Run-cai, DONG Xiao-xing, DU Nan-shan, GUO Zhi-xin, ZHANG Tao, PIAO Feng-zhi

2022, 43(02):  83-92.  doi:10.3969/j.issn.1000-6362.2022.02.001

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The prefabricated solar greenhouse has the tendency to replace the traditional greenhouse in the protected cultivation in China. The prefabricated solar greenhouse with double membrane and double insulation cover is one of them. But studies on microclimate of such greenhouses are lack. Therefore, the study of the microclimate in this kind of greenhouse is necessary, which can provide the basis for cultivation and management. The tested greenhouse is located in Zhengzhou, Henan province. Temperature, ground temperature at −0.1m（0.1m depth underground）, relative humidity and illuminance were measured both inside and outside the tested greenhouse. There are three recorders in the greenhouse, one 10m from the east wall, one 50m from the east wall and one 10m from the west wall, and there is also a 10m away from the southern greenhouse. The test period was from Nov.1, 2020 to Feb.28, 2021. The results showed that the ten-day average air temperature was 11.4−21.4℃, and the ten-day average of daily minimum air temperature was 9.4−16.7℃ in the greenhouse. The ten-day average temperature of soil temperature at 0.1m depth was 15.4−22.9℃, and the ten-day average of daily minimum soil temperature at 0.1m depth was 15.7−21.1℃ in the greenhouse ,and the max air temperature and soil temperature difference between indoor and outdoor was 17.0℃ and 15.6℃. During the coldest January late of the test, the ten-day average of daily minimum air temperature and soil temperature at 0.1m depth was 7.9℃ and 2.2℃. Ten-day average of daily minimum air temperature and soil temperature at 0.1m depth greenhouse was 9.9℃ and 15.8℃. The illuminance in the greenhouse increased gradually in the whole period. The typical sunny days illumination changed between 2000−22000lx, and average light transmittance were 42%, 52%, 49% and 45% in the greenhouse. The light transmittance existed obvious differences between each month, which was highest in December. The typical cloudy days illumination change between 300−4000lx and average light transmittances were 34%, 35%, 36% and 33% in the greenhouse, when light transmittance was not obvious difference between each month. The relative humidity was relatively high and was close to 100% at night in the greenhouse. The relative humidity is 95.4%−99.0%, and the proportion of the duration of leaf condensation is 89.1%−99.5% at night from late-Nov. 2020 to late-Jan. 2021. Come to a conclusion, the prefabricated solar greenhouse with double film and double insulation structure cover has better thermal insulation performance, and it can be used for the basis for cultivation and management. But the illumination transmittance light is low.

Research Progress on the Mechanism of High Light Use Efficiency in Wheat

LI Yi-bo, TAO Fu-lu

2022, 43(02):  93-111.  doi:10.3969/j.issn.1000-6362.2022.02.002

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Crop yield is dependent on crop biomass and harvest index. The increases in crop yield in the past benefit mainly from the increase in harvest index, the increase in biomass has been small. Light use efficiency is a bottleneck to further increase crop biomass and yield. Wheat (Triticum aestivum L.) is a widely cultivated cereal crop globally, providing energy to up to 20% of the world's population. It is necessary to reveal the intrinsic mechanism and extrinsic factors affecting the light use efficiency of wheat, which is important for improving the utilization efficiency of crop resources and productivity. Achieving high light efficient production of wheat under limited natural resources has become the focus of study at home and abroad. Here, the definition of light use efficiency, the main processes, the characteristics of light use efficiency in wheat were summarized from relevant references, showing a more significant potential to improve light use efficiency. The effects of external factors such as light, water, nutrient and tillage system on wheat light use efficiency were summarized. The results indicated that light use efficiency was regulated by internal factors such as photosynthesis at the individual plant scale, and by abiotic factors such as temperature, precipitation and tillage practices at the field scale. The current problems and the adaptation mechanism of wheat in the context of climate change were also analyzed, aiming to provide a theoretical reference for the practical research of the high light use efficiency of wheat. Future research on light use efficiency can use high-throughput phenotypic observation techniques combined with molecular markers to design ideotypes in the target environment, providing scientific evidence for crop breeding.

Comparison of Grain Dehydration Process and Yield Formation for Summer Maize under Different Sowing Dates in Huanghuaihai Plain

ZOU Jun-li, CUI Zhao-yun, XU Yi, ZHU Xia

2022, 43(02):  112-123.  doi:10.3969/j.issn.1000-6362.2022.02.003

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To reveal the impacts of sowing date on growth stage, grain dehydration process, dry matter accumulation and yield of summer maize, an experiment with three sowing dates was conducted at the agrometeorological experimental station of Taian in Shandong province in 2014 and 2015, in which the summer maize variety of Jundan 29 was used. The three sowing dates were June 5 (denoted as M−10), June 15 (denoted as M) and June 25 (denoted as M+10). The results showed that under the delay of sowing date (M+10), the duration of the summer maize at the whole growth period was shortened. Among them, the duration change from tasseling to maturity period was the largest, which was 7−10 days shorter than that of M and M+10. The water content and dry matter accumulation in kernels in summer maize of M−10 were higher than those of M+10. The grain dehydration rate of early sowing before physiological maturity was slower than that of late sowing, while that of early sowing after physiological maturity was faster than that of late sowing. The yield and yield structure factors of summer maize were significantly affected by different sowing dates under different meteorological conditions. Compared with the normal sowing date (June 15) of local summer maize, early sowing date (M−10) could increase the 100-grain weight and harvest index of summer maize, and reduce the bald point ratio. Compared with late sowing date (June 25), the grains per spike of summer maize under early sowing was significantly increased by 4.5% (2014) and 7.8% (2015) respectively. The 100-grain weight under early sowing was significantly increased by 12.3% (2014) and 16.8% (2015), and the bare tip ratio was significantly decreased by 21.4% (2014) and 12.5% (2015). It could be seen that the later the sowing date, the lower the yield. As a result, summer maize of Jundan 29 could be sown appropriately early in Huanghuaihai plain. Later sowing might easily lead to the delay of growth period and the occurrence of low temperature, which seriously affected the yield.

Quantitative Assessment on the Relative Influence of Climatic Change and Human Activities on Net Primary Productivity in Beijing-Tianjin-Hebei

GAO Xu-xu, YU Chang-wen, ZHANG Jing, ZHANG Jin-long

2022, 43(02):  124-136.  doi:10.3969/j.issn.1000-6362.2022.02.004

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Climate change and human activities are two driving factors that have vital influence on vegetation growth capacity. Quantitative assessment of the relative impact of climate change and human activities on net primary productivity (NPP) in Beijing-Tianjin-Hebei (BTH) can significantly improve the understanding of driving mechanism and help the improvement of ecological environment. Based on NPP data derived from Carnegie-Ames-Stanford Approach (CASA) model and meteorological data from 2001 to 2020, the relative contributions of climate change and human activities to NPP in BTH were quantitatively assessed by the methods of trend analysis and “detrended regression residuals methods”. The results showed that: (1) 47.8% of total area in BTH exhibited significant restoration, while only 4.5% underwent significant degradation. The annual NPP in developed urban agglomeration except Beijing decreased faster compared with other regions, while the middle of Zhangjiakou was the area with the fastest increase in annual NPP. (2) The climate change and human activities drove the NPP variation jointly as important forces in BTH and both induced a rapid increasing trend in the most areas. The spatial average influence of climate change on NPP variability was 1.5gC·m−2·y−1, while the impact of human activities was 2.4gC·m−2·y−1. (3) The contributions of climate and human activities accounted for 25.8% and 74.2% respectively to the significant increase of NPP in BTH in the past 20 years. The regions where the contribution rates of climate change were more than 80%, were mainly distributed in the northwest of Zhangjiakou and east of Cangzhou which covered 1.3% of the total areas. While there were 22.1% regions of BTH where the contributions of human activities were over 80% in the southwest of Zhangjiakou, Chengde, the south of Cangzhou and Hengshui. (4) The significant degeneration of vegetation was mainly induced by human activities whose contribution rats reached 94.9%. The results indicate that the human activities should be more focused on the ecological construction of vegetation restoration in BTH.

Hyperspectral Estimation of Chlorophyll Content in Winter Wheat Leaves under Low Temperature Stress

LI Wei-yi, SUN Ming-xin, ZENG Feng-ling, WANG Feng-wen

2022, 43(02):  137-147.  doi:10.3969/j.issn.1000-6362.2022.02.005

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For real-time monitoring of chlorophyll content in wheat under low temperature adversity, leaf spectral reflectance and SPAD (Soil and Plant Analyzer Development, SPAD) values were measured in 12 varieties of winter wheat at the seedling stage using a cold wave cooling process. Observations on December 28, 2020 (maximum/minimum temperature of 15℃/3℃) were used as pre-stress data, and observations on December 31 (maximum/minimum temperature of 1℃/−9℃) were used as post-low temperature stress data to analyze the patterns of changes in the raw spectra and SPAD values of wheat leaves before and after low temperature stress. The inverse model of chlorophyll content of wheat leaves before and after low-temperature stress was developed using the original spectral data, first-order spectral derivatives and three vegetation indices as independent variables and cross-validated, respectively. The results showed that: (1) compared with the pre-stress period, the overall SPAD of wheat leaves showed an increasing trend after low temperature stress, the spectral reflectance decreased in the visible light region where chlorophyll absorption was better, and the leaves showed freezing characteristics. (2) The accuracy of the two hybrid models constructed before and after low temperature stress was poor after cross-validation, indicating that the model for estimating chlorophyll content of wheat at room temperature was not applicable to the estimation of chlorophyll content of wheat after low temperature stress. (3) Among the hybrid models constructed using spectral data for the inversion of chlorophyll content in winter wheat under low temperature stress, the model with the first-order spectral derivative at 694 nm was the most effective, with an R2 of 0.694 and a RMSE of 3.191, indicating that the use of the characteristic spectral bands of wheat leaves for the estimation of chlorophyll content under low temperature stress was the most effective. The results can be used as a reference for non-destructive monitoring of chlorophyll content in multiple varieties of winter wheat.

Effects of Low Temperature Stress at Seedling Stage on Chlorophyll Content and Canopy Hyperspectral of "Hongyan" Strawberry

XU Ruo-han, YANG Zai-qiang, SHEN Meng-yin, WANG Ming-tian

2022, 43(02):  148-158.  doi:10.3969/j.issn.1000-6362.2022.02.006

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From September 2020 to January 2021, take “hongyan”(Fragaria×ananassa Duch “Benihope”) strawberry as test material to carry out low temperature environmental control test in Nanjing University of Information Science and Technology. Four low temperature treatments 21℃ (daily maximum temperature) / 11 ℃ (daily minimum temperature), 18℃/8℃, 15℃/5℃ and 12℃/2℃ were set, and the duration was set at four levels of 3d, 6d, 9d and 12d, with 25℃/15℃ as the control (CK). The chlorophyll content of strawberry leaves and canopy hyperspectral reflectance were measured. The effects of low temperature stress on chlorophyll content and canopy reflectance spectrum of strawberry were studied. The sensitive bands and characteristic parameters of chlorophyll content estimation model were selected. The results show that: (1) Under the same low temperature condition, Chla, Chlb and Chl(a+b) content of strawberry leaves decreased with the extension of stress days. Under the same stress days, the lower the temperature, the lower Chla, Chlb and Chl(a+b) content, that is, the greater the degree of low temperature stress, the greater the decline of chlorophyll content. (2) The changes of canopy spectral reflectance of strawberry seedlings under different temperatures and the same stress days were roughly the same. In the visible region, there are green peaks and red valleys in the reflection spectrum curve of strawberry canopy. In the near-infrared reflection platform, the spectral reflectance increases gradually with the decrease of temperature, that is, the reflection platform increases gradually. (3) The first-order differential spectrum curve of strawberry canopy changed violently, with obvious peaks and valleys, and occasionally double peaks in the red edge range. With the deepening of low temperature stress, the higher the value of the highest peak of the first-order differential spectrum, the near-infrared reflectance of strawberry canopy spectrum increased and the red edge position shifted blue, and then the peak gradually decreased and the red edge position shifted red. (4) The correlation coefficient between Chl(a+b) content and original spectral reflectance of strawberry canopy is negatively correlated. The correlation between Chl(a+b) content and reflectance in near-infrared band is significantly higher than that in visible band. The correlation between Chl(a+b) content and original spectral reflectance is good, reaching a significant level. The correlation coefficient of 737nm band is the largest, so it can be used as a sensitive band to predict chlorophyll content. The correlation between Chl(a+b) content and DVI, MSAVI, PVI, RDVI, SAVI and TSAVI in vegetation index is very significant, which can be selected as a characteristic parameter to predict chlorophyll content.