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20 December 2019, Volume 40 Issue 12

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Water Manipulations Altered Grazing Effects on Carbon Exchange in a Desert Steppe

LIU Qian, ZHANG Fang-min, CHEN Ji-quan, ZHAO Xiao-han, JING Yuan-shu

2019, 40(12):  737-746.  doi:10.3969/j.issn.1000-6362.2019.12.001

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Based on a long term grazing experiment (10 years) that includes no grazing (CK), light grazing (LG) and heavy grazing (HG) over a Stipa breviflora desert steppe in Siziwang, Wulanchabu, Inner Mongolia, China, a manipulative experiment of water input was conducted during 2012?2013. The grazing plots were treated as the block factor for nested water treatments. We aimed at exploring the responses of net ecosystem exchange (NEE), ecosystem respiration (RE) and gross ecosystem exchange (GEE) of carbon under two water additions: irrigation vs no-irrigation. We found that: (1) the desert steppe was a net carbon sink. Irrigation indirectly increased RE and the ecosystem carbon sink by elevating soil volumetric water content (Vwc) without grazing (P<0.01). NEE, RE and GEE were found to be more sensitive to Vwc due to irrigation (P<0.001). (2) The differences in NEE, RE and GEE among the grazing treatments were not significant under no-irrigation treatment, whereas positive deviations of ΔNEE and ΔGEE with grazing after August were significantly greater than the negative deviations before August (P<0.001). (3) The interactive contributions from irrigation and grazing treatments produced no significant effect on NEE, RE and GEE, but increased Vwc under grazing that enhanced ecosystem carbon sink and RE. When the grazing intensity was explored, both the magnitudes and changes of RE and GEE with Vwc at grazed sites were higher than those at no grazing plots (0.26 and 0.61, respectively), indicating that grazing resulted in a decrease in the sensitivity of carbon exchange to Vwc.

Analysis on the Effects of Increasing Efficiency and Reducing Emission of Nitrogen Fertilizer in an Eggplant Field on North China Plain

ZHENG Yi-min，GUO Li-ping，YANG Rong-quan，CAO Fei，NIU Xiao-guang，DIAO Tian-tian，YUN An-ping，XIE Li-yong

2019, 40(12):  747-757.  doi:10.3969/j.issn.1000-6362.2019.12.002

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In order to investigate the effects of different nitrogen fertilization on vegetable yield, nitrogen recovery rate and the ammonia volatilization as well as the N2O emissions during the whole eggplant growth season (between June to November), six treatments were set in a typical open-ground eggplant field on the North plain. Six treatments included no fertilization (CK), conventional nitrogen rate (N1), nitrogen rate reduction by 20%(N2), nitrogen rate reduction by 50% (N3), nitrogen rate reduction by 20% combined with inhibitor coated urea (N2I), and nitrogen rate reduction by 20% with amendment of biochar (N2B). The results showed that, (i) compared with conventional N rate (N1), reduction of N by 20% (N2) did not have significant impact on the eggplant yield; while N rate reduction by 50% (N3) resulted in the obvious decrease of vegetable crop. Application of inhibitor coated urea or biochar can improve the N recovery efficiency to some extent, respectively. (ii) Both ammonia volatilization and N2O emissions were closely related to the fertilization with the emissions higher than no fertilizer treatment significantly. Both the ammonia volatilization and N2O emissions of each fertilization treatment were occurred after fertilization events, with the emission factors of 9.6%?14.8% for ammonia and 0.9%?1.1% for N2O.(iii) Compared with the conventional N rate treatment (N1), the cumulative ammonia volatilization emissions of N2, N3, N2I and N2B decreased by 20.3%, 48.6%, 41.7% and 30.7%, respectively. Under the premise of not affecting the yield, N rate reduction by 20% combined with inhibitors coated urea (N2I) showed the lowest environmental risks for gas emissions. (iv) Compared with conventional N rate treatment (N1), the cumulative N2O emission of N2, N3, N2I and N2B showed decrease by 21.5%, 41.7%, 44.2% and 31.6%, respectively. The cumulative N2O emission of N2I treatment was much lower than with conventional N rate (N1), and it was almost equivalent to that emitted from the treatment which showed N reduction by 50% (N3). Therefore, reducing N application rate by 20% or more and combined with inhibitor coated urea is the appropriate N management practice to ensure the vegetable yield, improve the N efficiency, and reduce ammonia volatilization and N2O emissions in eggplant fields on North Chinese Plain.

Simulation Model of Material Accumulation and Distribution of Fresh Cut Tulips of Different Varieties

CHENG Chen，YU Wei-dong，YAN Jin-tao，LIU Hai-peng，FENG Li-ping

2019, 40(12):  758-771.  doi:10.3969/j.issn.1000-6362.2019.12.003

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With the increase of flower tourism projects, seedballs were imported about 17 million dollar to China in 2017, mainly towards lilies and tulips, and the demand for tulip seedball has also increasing significantly. Therefore, it is important to explore the quantitative relationship between the accumulation and distribution of tulip matter and meteorological environmental factors in solar greenhouse, and to establish a simulation model of dry and fresh matter accumulation and distribution index. The experiment was carried out in the international flower port solar greenhouse base named B2 in Yangzhen (40°10′27″N, 116°47′41″E, altitude 38m), Shunyi district, Beijing in 2016?2017. By means of collecting tulip experiment observation data of four kinds of different varieties (‘Pink Impression’; ‘Daydream’ ; ‘Esmee’ and ‘Queen of Night’), correspondingly, which were divided to four types of florescence (early blossoming, medium blossoming, later blossoming and very later blossoming), in growing seasons by multicast hydroponic way. StanGDD (Standardized growing degree days) was used as the environment driving variable to quantitatively analyze the variation law of dry and fresh matter accumulation and distribution index of different organs of tulip. The regression equations were obtained through statistical analysis and fitting, and used the independent experiment data to verify the model. The results showed that, firstly, the accumulation of dry and fresh matter in roots, stems and leaves revealed a Logistic curve with StanGDD. The accumulation of fresh matter in seedballs were not changed with StanGDD, but the accumulation of dry matter in it showed a quadratic function which decreased first and then increased with StanGDD. The accumulation of dry and fresh matter in flowers revealed a quadratic function which increased first and then decreased with StanGDD. The accuracy of dry and fresh matter accumulation model ranked by stem and flower < root < leaf < seedball. Secondly, the dry and fresh matter distribution index of stems and leaves showed a Logistic curve with StanGDD. The dry and fresh matter distribution of seedballs index revealed a quadratic function which decreased first and then increased with StanGDD, but the dry and fresh matter distribution index of flowers displayed the opposite tendency. The dry and fresh matter distribution index of roots displayed a decreased linear with StanGDD. The accuracy of dry and fresh matter distribution index model ranked by stem < root and bud < leaf < seedball. Thirdly, the simulation accuracy of dry matter accumulation and distribution model of different organs were higher than that of fresh matter. In general, the simulation model of matter accumulation and distribution of tulip in solar greenhouse had a high simulation accuracy.

Effect of Integrated Fertilization Level of Water and Fertilizer on Maize Grain Filling and Dehydration Process

FU Jiang-peng, HE Zheng, JIA Biao, LIU Zhi, LI Zhen-zhou, LIU Hui-fang

2019, 40(12):  772-782.  doi:10.3969/j.issn.1000-6362.2019.12.004

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The field experiment of drip irrigation water and fertilizer integration was carried out in Ningxia Yellow River Irrigation District which using the maize variety“Tianci 19”as the material, and six different nitrogen fertilizer levels 0(N0), 90(N1), 180(N2), 270(N3), 360(N4) and 450(N5) kg·ha-1 in 2017 and 2018. The fresh weight of 100 grains of maize was determined, and the grain moisture content was calculated. The grain filling model based on Logistic equation was developed and verified, and the dynamic characteristics of maize grain dehydration were analyzed. To explore the effects of different nitrogen levels on maize grain filling and dehydration process, and the dynamic changes of maize grain filling and water content. The results showed that: (1) the grain filling process of the maize variety “Tianci 19” treated with different nitrogen application levels in 2017 was consistent with Logistic equation under the condition of integrated drip irrigation and water fertilization. The model test results were RMSE=0.203 and R2=0.954 (P<0.01). (2) The grain filling rate of maize kernels in each treatment showed the characteristics of increasing first and then decreasing. The grain filling rate was the highest with 270 kg·ha-1 (N3) during the two-year test period. (3) Nitrogen application increased maize time to maximum grain filling rate (Tmax), maximum grain filling rate (max), growth at maximum grain filling rate (Wmax) and active grain filling stage (T), N3 (270kg·ha-1) treatment shortens the time to maximum grain filling rate (Tmax) and prolongs the active grain filling stage (t3). (4) Logistic equation was used to divide the filling process of nitrogen application into three stages: pyramid stage, fast increase stage and slow increase stage. The grain filling rate was the highest in the fast increase stage and the grain accumulation. (5) Drip irrigation water and fertilizer integration of topdressing nitrogen fertilizer can significantly promote the regulation of maize grain filling and dehydration process. The water content of grain in each treatment showed a monotonous decreasing trend, and the dehydration rate was significantly different in the late stage of physiological maturity. In the two-year experiment, the water content of maize seeds treated with 270 kg·ha-1 nitrogen treatment was lower, and the dehydration rate was faster in the late stage of physiological maturity.

Effect of Different Oligosaccharides by Spraying on Plant Growth and Quality in Lettuce

HE Jiu-xing, ZHAO Jie-chun, BAI Wen-bo, ZHENG Li, ZHANG Yuan-cheng, YU Meng-meng, Kimoto Hisash, Saito Makoto, LV Guo-hua

2019, 40(12):  783-792.  doi:10.3969/j.issn.1000-6362.2019.12.005

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Experiments in climate chamber were performed to explore the levels of various components of single and mixed oligosaccharides on growth, yield and performance of lettuce. A short-growing type of lettuce (var. ramosa Hort) and three oligosaccharides, such as cello-oligosaccharides (ZH-A), xylo-oligosaccharides (ZH-B), and chitosan oligosaccharides (ZH-C) were selected. The mixed oligosaccharides (ZH-M) (Mass Ratio, ZH-A:ZH-B:ZH-C=1:1:1) and the conventional polysaccharide sodium alginates (GY-D) were prepared for the experiment. 80mg·L?1 of each was applied 4 times (every 3 days) to lettuce by foliar spraying after three days of planting and the water (CK) was used as a control. Growth characteristics (biomass, leaf area and fluorescence photosynthetic), root phenotypic characteristics (root length, root surface area and root volume) and the quality characteristics (soluble sugar, chlorophyll, Vc, and nitrate contents) of lettuce were measured at the harvest stage (23 days after planting). The results showed that foliage spraying can significantly increase the biomass of lettuce in all single oligosaccharide treatments and the (GY-D) treatment. The cello-oligosaccharide showed the significant increase in root growth and decrease in nitrate content. The chitosan oligosaccharide showed the substantial increase in chlorophyll content, the maximum photosynthetic efficiency (Fv/Fm) and the soluble sugar content. The mixed oligosaccharides (ZH-M) showed the best effects on lettuce growth, such as the above and underground biomass and the quality characters. In the ZH-M treatment, the fresh weight and leaf area index increased by 52.58% and 57.60% at the harvest stage. And, root dry weight, total root lengths, root total volume and root surface area increased by 35.07%, 89.10%, 49.23% and 40.68%, respectively. The content of soluble sugar, chlorophyll, and Vc rose by 25.20%, 21.50% and 12.08% respectively, while the nitrate content dropped by 27.65%. In conclusion, significant differences in interaction and regulation regime were found among the different oligosaccharides on plant physiology and growth. Compared with the single oligosaccharide, the mixed oligosaccharides showed the multiplying influences on plant growth and quality improving.

Effect of Hose Material and Length on the Stability Time of CO2 /H2O Analyzer in Farmland Microclimate

WANG Zhi-wei, WANG Meng, WANG Qiu-tao, ZHU Xiao-wei, WANG Chun-shan, WANG Hao,

2019, 40(12):  793-799.  doi:10.3969/j.issn.1000-6362.2019.12.006

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Concentrations of CO₂ and H₂O are important indicators of farmland microclimate. When using CO₂ and H₂O analyzers to determine indicators in the field, the hose must be used to transfer the gas to the analyzer，but the material and length of the hose will affect the setting time and accuracy of the CO₂ and H₂O when they were determined. In this study, 8 hoses and 5 lengths were used to screen the best material and length for CO₂ and H₂O measurements. The results showed that the setting times of CO₂ in different material hoses were in 9.20−11.47s, and the setting times of H₂O were in 9.67−18.93s. The stability analysis of the setting time of CO₂ and H₂O using the AMMI model shows that in the CO₂ concentration stability, the fixed effect caused by the length was the largest, followed by the material, and the material and the length were mutually exclusive. The setting time of CO₂ concentration of the peristaltic pump tube in the material was the shortest; while in the setting time of H₂O concentration, there was a significant interaction effect between the material and the length, in which the fixed effect caused by the material was the largest, and the length in the second place, and the setting time of H₂O concentration of Polyvinyl chloride(PVC) pipe was the shortest. Different materials had different interactions with different lengths. Each material had its own special adaptability to different lengths. Therefore, in the test process, chose the material and length of the shortest setting time according to the required measurement indicators to ensure the accuracy and efficiency of the data.