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20 January 2019, Volume 40 Issue 01

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Spatial and Temporal Variation of Extreme Precipitation Indices in Southwestern China in the Rainy Season

WANG Hao, JIANG Chao, WANG He-song, SUN Jian-xin

2019, 40(01):  1-14.  doi:10.3969/j.issn.1000-6362.2019.01.001

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Based on the daily precipitation data of 477 meteorological stations from 1971 to 2013 in southwestern China, the spatial distribution and variation features of 11 extreme precipitation indices were analyzed by using the linear regression, Mann-Kendall test and moving t test. Besides, the relationship among the multi-year average of extreme precipitation indices，variation trend and altitude were also discussed. The results were as follows: (1) in the past 43 years, the decline rates of PRCPTOT, CWD, R1mm, R10mm and SDII in the rainy season of southwest China were 12.6mm·10y-1, 0.23d·10y-1, 1.57d·10y-1, 0.49d·10y-1 and 0.31mm·d-1·10y-1(P<0.05) respectively, the growth rate of CDD is 0.37d·10y-1 (P<0.05), while the changes in Rx1day, Rx5day, R95, R99, and R20mm were not significant. (2) The mutations of CDD, R1mm, and Rx1day in the rainy season occurred in the 1980s intensively, while the mutations of PRCPTOT, R10mm, Rx5day, and SDII occurred mainly around 2003. RCPTOT, CDD, R1mm, R10mm, Rx1day, and SDII showed certain stability before mutation year and a significant increase or decrease trend after mutation year. (3) From the perspective of spatial distribution, not all regions showed the tendency of drought. The extent of drought in rainy season at the junction of Yunnan, Guizhou and Guangxi provinces was more serious, the risk of heavy rain and flood disaster in the rainy season in southeastern Guangxi was greater, while rainy season in the Hengduan Mountains was more humid. (4) In terms of the contribution rate, variation trend of precipitation proportion in rainy season in southwestern had a strong regional characteristic: the contribution rate of rainy season indices for the whole year in northern Sichuan and Tibet had declined year by year, while in southeastern Guangxi it had gradually increased. (5) Judging from the relationship between the 11 indices and altitude, in high altitude regions of southwestern, the R1mm value was higher and the precipitation was mainly moderate and light rain. Besides, the multi-year average values of PRCPTOT, R1mm, R10mm and R20mm showed different degrees of upward trend. Therefore, the climate had become more humid in the past 43 years. On the other hand, in low altitude regions, R1mm was lower, while R95, R99, Rx1day, Rx5day, and SDII were higher and CWD, CDD showed an upward trend. Therefore, the risk of flooding and drought in the low altitude regions during the rainy season was relatively larger.

Effect of Conservation Tillage with Smash Ridging under Green Manure Condition on the Emission of Greenhouse Gas in the Rice Field Soil

ZHENG Jia-shun, HU Jun-ming, WEI Xiang-hua, Huang Tai-qing, LI Ting-ting, HUANG Jia-qi

2019, 40(01):  15-24.  doi:10.3969/j.issn.1000-6362.2019.01.002

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This continuous field positioning experiment was carried out in the experimental field of Guangxi Academy of Agricultural Sciences from 2016 to 2018 with setting two kinds of farming modes, including the smash ridging and the conventional tillage, along with setting up blank control with no fertilizer, conventional application of chemical fertilizer, single green manure and chemical fertilizer and double green fertilizer and chemical fertilizer 4 kinds of fertilization treatments. After 5 days of rice transplanting in 2018, the greenhouse gas emission flux of rice fields was continuously measured by separate static chamber-meteorological chromatography to study the main greenhouse gas emission characteristics and their cumulative effects of different tillage patterns and fertilization treatments under green manure and analyze the cumulative emission of greenhouse gases and the potential of warming, in order to provide reference for the conservation of tillage and fertilization management mode. The results showed that the CO2 emission flux of conventional fertilizer treatment under the smash ridging was 2.3 times that of the conventional tillage mode. The CH4 emission during the critical period of the rice field peak under the application of double green manure is 2.5 to 3.9 times that of the action of chemical fertilizers. In each treatment, the cumulative CO2 emission from paddy field treated with single-green manure plus chemical fertilizer was the lowest, which was 1469.29kg·ha-1, and the cumulative N2O emission was the least, which was 36.61g·ha-1. The cumulative emission of CH4 from single green manure plus chemical fertilizer under the two farming modes was lower than that of double green manure plus chemical fertilizer. Rational application of green manure plus chemical fertilizer has a certain positive effect on the reduction of greenhouse gas CO2 and N2O emission under the smash ridging mode. The CH4 emissions in paddy fields were related to the green manure volume and the warming potential of greenhouse gases was also affected accordingly. On a certain time scale, applying the conservation tillage with green manuring and smash ridging is an effective measure to reduce and contain agricultural greenhouse gas emissions.

Effects of LED Green Light on Growth and Quality of Lettuce

WANG Xiao-jing, CHEN Xiao-li, GUO Wen-zhong, LI Hai-ping, LI Ling-zhi

2019, 40(01):  25-32.  doi:10.3969/j.issn.1000-6362.2019.01.003

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The experiment was conducted in a closed plant factory with artificial light. Lettuce (Lactuca sativa L.) hydroponically cultured was used as materials, and the light intensity and quality were both adjustable. White light provided at 8：00-24：00 with light intensity of 200μmol·m-2·s-1 was regarded as control (W), and green light with light intensity of 50 (WG50), 100 (WG100) and 150μmol·m-2·s-1 (WG150) was respectively used instead of equal white light. Lettuce biomass, morphology, leaf number, and the contents of chlorophyll, nitrate nitrogen, vitamin C, soluble sugar, crude fiber and starch were determined, to investigate the effects of green light on the growth and quality of lettuce and explore better supply modes for green light. The results showed that: (1)the WG50 treatment significantly increased the chlorophyll content in lettuce shoot and also enhanced the dry weight of lettuce shoot by 3.69% compared with the control. (2) With the increase of green light and the decrease of basic white light, the soluble sugar and vitamin C contents in lettuce shoot rose first and then declined. The highest and lowest content of both the two indices were respectively detected under WG50 and WG150 treatment, the differences in comparison of the control reaching significant level (P<0.05). (3) Compared with the control, all the treatments with green light reduced the contents of starch, crude fiber and nitrate in lettuce leaves. The lowest nitrate content was observed in lettuce treated with WG50. In summary, green light with the intensity of 50μmol·m-2·s-1 might promote the accumulation of dry matter in lettuce and improve the quality of lettuce.

Analyzing on the Optimum Direct-sowing Date for Yongyou15 Rice Variety in Zhejiang Region

JIANG Xiao-dong, LV Run, JING Zhi-feng, MAO Zhi-jun, LI Jian-ye, YANG Shen-bin, GUO Jian-mao

2019, 40(01):  33-40.  doi:10.3969/j.issn.1000-6362.2019.01.004

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To reveal the impacts of sowing date on dry matter accumulation and yield composition of direct seeding rice, an experiment with five sowing dates was conducted at the agrometeorological experimental station of Longyou in Zhejiang province in 2017, in which the rice variety of Yongyou15 was used. The five sowing dates were May 5 (denoted as A1), May 15 (denoted as A2), May 25 (denoted as A3), June 4 (denoted as A4) and June 14 (denoted as A5). During the experiment, the leaf area index (LAI), photosynthetic production, dry matter accumulation and transfer, and the characteristics of rice yield were observed and analyzed to examine their relationships with sowing dates. The results showed that under the optimum sowing date (A2), the LAI, the photosynthetic potential, the growth rate of the rice were higher than that of other sowing dates. The output and conversion rates of the dry matter accumulation were also higher. The dry matter output of A2 was 7.87%, 15.29%, 49.43% and 56.43% higher than that of A1, A3, A4 and A5 respectively. The matter conversion rate of A2 was 5.59%, 13.18%, 28.60% and 39.83% higher than that of A1, A3, A4 and A5 respectively. Compared with the optimum sowing date (May 25) of local single cropping of late rice, proper early sowing could increase the effective panicle number, seed setting rate and grain number per panicle which finally contribute to the rice yield of direct-sowing rice. As a result, the yield of A2 reached 8879.70kg·ha-1, about 392.10, 610.20, 1445.85 and 2085.15 kg·ha-1 higher than that of A1, A3, A4 and A5 respectively. It concluded that the optimum sowing date of Yongyou 15 with direct-sowing cultivation in Longyou region is in the middle of May. Earlier or later planting (in early May or late May) may lead to a decline in rice production, sowing in June or even later could result in a significant decrease in the final yield.

Simulation of Photosynthetic Active Radiation Capture of Cut Flower Lily Based on Functional-structural Plant Model

LI Chao, GU Sheng hao, Zhang Li zhen

2019, 40(01):  41-50.  doi:10.3969/j.issn.1000-6362.2019.01.005

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In order to overcome the lack of approach to designing crop ideotype and to optimizing agronomic managements, a functional-structural plant(FSP) model for cut flower lily that can simulate growth and development of lily was developed via combination of experimental measurements and system simulations. The three- dimensional(3D) population growth of lily was reconstructed by using random algorithm to regulate leaf inclination, phyllotaxis, seedling orientation and seedling time within a reasonable range. The accumulated photosynthetic active radiation(PAR) of lily canopy in relation to different planting date(10, 20, 30 April and 10, 20, 30 May), plant density(66.7，33.3，22.2，16.7，13.3，11.1 plants·m-2) and plant type(leaf inclination were 20°, 30°, 40°, 50°, 60°, 70° and 80°) were quantitatively analyzed using the radiation module embedded in a 3D modelling platform GroIMP. The results showed that the accumulated PAR of lily canopy can be maximized by planting on April 20 and by decreasing the leaf inclination to 20°. FSP model for lily can be applied to design crop ideotype and to optimize agronomic managements, thus providing theoretical basis and technical support for evaluation of germplasm resources and genetic improvement.

Temporal and Spatial Distribution of Heat Damage during Heading and Flowering Stage of Rice in Hubei and Hunan Province

GUO Jian-mao, PEMA Rigzin, LIANG Wei-min, SHEN Shuang-he, JIANG Xiao-dong

2019, 40(01):  51-61.  doi:10.3969/j.issn.1000-6362.2019.01.006

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Temporal and spatial distribution of early and middle rice during heading and flowering stage in Hubei and Hunan province (i.e.the two-lake region）was analyzed using the daily meteorological data of 34 meteorological sites from 1961 to 2017 year and observation data of annual growth period of 28 agrometeorological sites from 1981 to 2011. Linear regression method and ArcGIS's inverse distance weight (IDW) spatial analysis function was used in this study. The results showed that, (1) days and times of heat damage on early rice in Hubei and Hunan provinces was the most in 2000s, followed by 1960s and 2010?2017, the least in 1980s; The heat damage days and times on middle rice in Hubei and Hunan provinces was the most in 1970s, followed by 1960s and 2000s and 2010?2017 , the least in 1980s. (2) The heat damage days and times on early rice high value areas was distributed in southeastern Hubei and southern Hunan, and the low value areas was distributed in southwestern Hubei and western Hunan; The heat damage days and times on middle rice was distributed in northeastern Hubei, southeastern Hubei, southwestern Hubei, western Hunan, and southern Hunan, and low value areas was distributed in northwestern Hubei and western Hunan. (3) The heat damage times on early rice and middle rice in Hunan and Hubei is slight greater than moderate, and moderate greater than severe; The heat damage times on early rice and middle rice Hunan is more serious than Hubei; The heat damage of Hubei and Hunan middle rice is more serious than early rice.