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20 April 2018, Volume 39 Issue 04

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Temporal and Spatial Variations of Agro-meteorological Disasters of Main Crops in China in a Changing Climate (Ⅲ):Drought of Summer Maize in North China Plain

WAN Neng-han，YANG Xiao-guang，LIU Zhi-juan，HE Bin，SUN Shuang

2018, 39(04):  209-219.  doi:10.3969/j.issn.1000-6362.2018.04.001

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Based on the 1961-2010 daily meteorological data from 36 meteorological stations and the 1981-2010 growth period data of summer maize from 23 agricultural meteorological stations, the spatial distribution and evolution trend of drought for summer maize in different growth period were analyzed by using the crop water deficit index (CWDI). The results showed that light drought was the most frequent during different growth periods of summer maize in North China Plain. During the period from sowing to jointing, the occurrence frequency of light drought ranged from one time in five years (20%) to two times in three years (33%) in most regions; During the period from jointing to tasseling, the light drought was mainly concentrated in the boundary area of Hebei, Henan and Shandong province and the occurrence frequency ranged from one time in five years to two times in three years; During the period from tasseling to maturity, the light drought was mainly concentrated in the central of Hebei and occurred one time in three years. The light drought in whole stages mainly occurred in most regions of Hebei, Beijing, Tianjin, the north of Henan and the west of Shandong, which occurred one time in three years. During 1961-2010, the whole region drought during sowing to jointing and tasseling to maturity were most frequent, the highest ratio of drought occurring stations occurred in 1990s; The drought strength during tasseling to maturity increased obviously in the southeast of Shandong and east of Hebei. Light drought occurred most frequently among the drought frequency at all grades during different growth periods of summer maize. The drought occurrence frequency during the period from sowing to jointing and the period from tasseling to maturity was higher than the other growth periods. The occurrence frequency of light drought was higher during the whole growing period and the center of light drought mainly concentrated in most part of Hebei province, Beijing, Tianjin, Northern Henan province and Western Shandong province with a drought frequency of more than 33%. The whole regional drought mainly occurred from sowing to jointing and tasseling to maturity during which the drought range was wider. Furthermore, the trend of drought strength for different growth stages of summer maize in North China Plain increased in northern Hebei province and decreased in southern Henan province.

Simulation of Different Irrigation Strategy on Wheat Yield in Huang-Huai-Hai Plain under the RCP8.5 Scenario

QIN Xiao-chen，ZHOU Guang-sheng，JU Hui，LI Xiang-xiang，LIU Qin

2018, 39(04):  220-232.  doi:10.3969/j.issn.1000-6362.2018.04.002

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Huang-Huai-Hai Plain (3H Plain) is widely accepted to be the largest winter wheat growing areas of China. Water shortage is comprehensively recognized as the limiting factor for winter wheat growth. In the context of global warming, precipitation and evapotranspiration during wheat growing period have experienced significant changes. Consequently, understanding the impact of different irrigation strategy on wheat yield is essential for establishing climate adaptation strategies in 3H Plain. In this paper, the phenology and yield data of six typical agro-meteorological stations representing six sub-regions were used to calibrate the CERES-Wheat crop model. Based on the calibrated model and the future climate projected by HadGEM2-ES under RCP8.5 scenario, the yield reduction rate under rain-fed conditions compared to potential yield for the short-term (2010-2039), medium-term (2040-2069) and long-term (2070-2099) were analyzed. Then the yield retrieval ability of different irrigation strategy was compared. Results showed that, compared to full-irrigated yield, rain-fed condition would decline wheat yield by 47.3%, 53.5% and 50.9% for the short-term, medium-term and long-term respectively, with the spatial distribution of higher reduction rate in sub-region Ⅰ to Ⅳ (north), and the reduction rate in sub-region Ⅵ(south) only 7.4% (short-term) ,12.8% (medium-term) and 9.7% (long-term). Comparison of different irrigation system showed there is a big difference in compensation effect (i.e. the difference of the reduction rate under rain-fed and irrigation condition) of winter wheat on different growth stage. And the compensation effect of northern sub-region was higher than that of Southern sub-region. The efficiency of irrigation on jointing stage was the highest, of which the yield retrieval ability was 16.3-18.6 percent point for different future period. The second was irrigation on grain filling stage, of which the yield retrieval ability was 5.1-6.1 percent point. While irrigation on overwintering stage could only retrieve yield by 0.4-0.6 percent point. Further analysis showed that irrigate on both jointing stage and grain filling stage could retrieve yield by 23.6-25.1 percent point. Thus, under the recognition of higher risk of water shortage in the future, securing irrigation supply for jointing stage is of first priority. And if two-times irrigation was allowed, irrigate on both jointing stage and grain filling stage could retrieve half of the yield losses.

Responses of Winter Wheat Phenology to Accumulated Temperature during Growing Periods in Northern China Wheat Belt

MA Qian-qian，HE Yong，ZHANG Meng-ting，ZHANG Cong，XU Yin-long

2018, 39(04):  233-244.  doi:10.3969/j.issn.1000-6362.2018.04.003

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Based on data collected from 19 agro-meteorological stations located in the winter wheat belt of Northern China from 1993 to 2013, this study analyzed temporal and spatial variability of winter wheat phenology and accumulated temperature in each growing period. Pearson correlation analysis and other methods were used to analyze the effects of accumulated temperature in each growing period on winter wheat phenology. The results showed that,（1）the spatial distribution of ≥0℃accumulated temperature during sowing to emergence and regreening to jointing periods along with the negative accumulated temperature value during the overwintering period (NATop) increased from east to west, and ≥0℃ accumulated temperature during jointing to heading, heading to milk-ripe, milk-ripe to maturity and sowing to maturity periods increased from southeast to northwest, while the distribution during emergency to start of overwintering period was contrary. The ≥0℃accumulated temperature for jointing to heading and milk-ripe to maturity periods decreased significantly at 21% of the investigated stations. The value of NATop, ≥0℃accumulated temperature during regreening to jointing, heading to milk-ripe and sowing to maturity periods increased significantly at 42%, 26%, 37% and 21% of the investigated stations, respectively. The variations of ≥0℃ accumulated temperature during sowing to emergency and emergency to the start of overwintering periods were much smaller. (2) Sowing and emergency date in the east was later than the counterpart in the west, of which variation trend was contrary to heading, milk-ripe and maturity date. Start of overwintering date in the southeast was later than the counterpart in the northwest, of which variation trend was contrary to regreening date. The stations of earlier jointing date were mainly located in the east. Sowing, emergency, regreening, jointing, milk-ripe and maturity date delayed significantly at 21%, 16%, 37%, 26%, 42% and 21% of the investigated stations, respectively. And most of these stations were in the east of the study area. Overwintering and heading date changed significantly only at 5% of the investigated stations. (3) Correlation analysis showed that the correlation between ≥0℃ accumulated temperature (or NATop) and multiple development stages was significant, which indicated that the growth and development of winter wheat might be directly or indirectly influenced by the accumulated temperature during growing periods. The NATop had the highest correlation with regreening, jointing, heading, milk-ripe and maturity date, and showed consistent spatiotemporal variation characteristics with multiple post-winter development stages. Spatiotemporal variability of the NATop might be the factor that caused spatiotemporal variations of winter wheat post-winter phenology.

Spatio-Temporal Variability and Cause Analysis of Reference Crop Evapotranspiration in the Main Grain Producing Areas of China

YANG Yong-gang，CUI Ning-bo，HU Xiao-tao，GONG Dao-zhi

2018, 39(04):  245-255.  doi:10.3969/j.issn.1000-6362.2018.04.004

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Under the background of global warming, the change and spatial distribution of reference crop evapotranspiration are bound to have an important impact on agricultural water resources planning and agricultural water management in the main grain producing areas of China. The main grain producing areas of China was divided into temperate humid and semi-humid area (I area), temperate arid and semi-arid area (II area), warm temperate semi-humid area (III area) and subtropical humid area (IV area) according to the difference of heat and humidity. Based on daily meteorological data of the 265 stations in the main grain producing areas of China during 1961 to 2013, the daily ET0 was calculated by Penman-Monteith equation recommended by Food and Agriculture Organization in 1998. The temporal and spatial variation of ET0 and its influencing factors were analyzed by using Arcgis spatial interpolation, Mann-Kendall trend test, sensitivity analysis and contribution rate analysis. The results showed that the annual ET0 in major grain producing areas of China was 878.9mm and had a significant downward trend as a whole at the rate of 0.47mm·y-1(P＜0.05) in the past 53 years. The annual ET0 of I, II and IV area decreased with the value of 741.8mm, 1079.8mm and 924.2mm respectively, but the trends of changes were not obvious. The annual ET0 of III area was 940.2mm, which had an extremely significant downward trend with a rate of 1.21mm·y-1(P＜0.01). Sensitivity analysis indicated that relative humidity was the most sensitive meteorological factor to annual ET0 change in the whole and I-IV area, with the sensitivity coefficient of -1.060, -1.232, -0.784, -1.114 and-1.009，respectively. Contribution analysis showed that wind speed made the greatest contribution to ET0 changed in I-III and whole area, while relative humidity was the meteorological factor that contributed most to the change of ET0 in IV area. The decrease of wind speed was the dominant cause of ET0 decrease in I-III and whole area, and the main reason for the decrease of ET0 in IV area were the decrease of wind speed and the shortening of sunshine hours.

Effects of Organic Fertilizer Substituting Chemical Nitrogen Fertilizer on Nitrogen Content in the Surface Water and Soil of Paddy Field in the Erhai Lake Basin

ZHANG Xue-li，DONG Wen-yi，LIU Qin，WANG Hong-yuan，YAN Chang-rong，LIU Hong-bin，

2018, 39(04):  256-266.  doi:10.3969/j.issn.1000-6362.2018.04.005

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Aiming at the non-point source pollution problem caused by nitrogen fertilization in paddy fields of Erhai Lake basin, a field experiment was conducted during 2015-2016 in paddy field with different soil fertility condition, including no nitrogen fertilizer (CK), inorganic nitrogen fertilizer (F), organic manure completely substituting ?chemical nitrogen fertilizer (M) and organic manure substituting?half chemical nitrogen fertilizer (MF) under the same amount of total nitrogen input. We got the results by comparing different treatments in dynamic change of total nitrogen (TN), dissolved total nitrogen (DTN), ammonium (NH4+?N), and nitrate (NO3??N). The results indicated that the content of TN, DTN, NH4+?N and NO3??N reached its peak after 1-4 days of fertilization for each treatment, then the content decreased gradually, the period within a month after fertilization was critical period to prevent nitrogen runoff loss. (2)The content of TN and DTN were relatively high within a month of fertilization of MF treatment, which extended the critical period of nitrogen loss. (3) At harvest, both of M and MF treatment could improve the content of soil total nitrogen at 0-20cm soil and changed the form of soil inorganic nitrogen in topsoil. M treatment decreased total nitrogen content and increased nitrogen loss at 20-50cm soil, compared with F and MF. Soil mineralized nitrogen was dominated by NO3??N at 0-40cm in M treatment, while inorganic nitrogen was dominated by NH4+?N in MF and F treatment. Although organic manure substituting half chemical nitrogen fertilizer improved TN at 0-20cm soil, it extended the critical period of nitrogen loss. Thus, improvement of field water management and prevention of field drainage within a month after fertilization should be applied when extending combined application of organic manure and chemical fertilizer in Erhai Lake Basin.

Impact of Climate Change on Walnut-Planting Climatic Suitability in Xinjiang

PU Zong-chao，ZHANG Shan-qing

2018, 39(04):  267-279.  doi:10.3969/j.issn.1000-6362.2018.04.006

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Based on the data of daily mean temperature, maximum temperature and minimum temperature from 102 meteorological stations in Xinjiang during 1961-2015, the fundamental spatial-temporal change characteristic of key climatic factors affecting walnut planting, such as ≥10℃ accumulated temperature(∑Tmen≥10℃), days of minimum temperature was lower than -25℃ (DTmin≤-25℃), days of the daily maximum temperature was over 40℃(DTmax≥40℃) and the days which was the last frost date earlier than the first date of daily mean temperature≥10℃(DFTmen≥10℃-LF), were analyzed by using the methods of linear regression, accumulative anomaly, T-test and mixed spatial interpolation technology based on ArcGIS. And the effect of above climatic factors change on walnut-planting climatic suitability, and the distributed areas of suitable, sub-suitable and unsuitable to walnut-planting were studied by combining with the climatic suitability zoning index of walnut planting. The main results showed that spatial distribution of above climatic factors had very obvious difference from place to place in Xinjiang, generally, ∑Tmen≥10℃ were more in south than in north, in plain and basin than in mountain regions. DTmin≤-25℃ were more in north and mountain regions than in south, plain and basin. DTmax≥40℃ were more in east, plain and basin than in west and mountain regions. DFTmen≥10℃-LF were more in west and mountain regions than in east, plain and basin. Under the comprehensive influence of above climatic factors, the climate suitable areas for walnut planting were mainly in the west of Tarim basin, sub-suitable areas were in most of Tarim basin and the south of Tuha basin. Most of the northern Xinjiang, Altai mountain, Tianshan mountain and Kunlun mountain, and the Tuha basin, eastern part of the Tarim basin were not suitable for walnut-planting. In the background of global warming, ∑Tmen≥10℃, DTmax≥40℃ and DFTmen≥10℃?LF had been significantly（P＜0.05）increased? with the rate of 64.7℃·d·10y-1，0.48d·10y-1 and 0.120d·10y-1, respectively, DTmin≤-25℃ presented significantly（P＜0.001）decreasing trend with the rate of -0.980d·10y-1, and above climatic factors had mutation in 1986 or 1997 respectively, climate warming was obvious in recent 55 years in Xinjiang. By the affected of climate warming, the suitable areas and sub-suitable areas for walnut-planting were increased, but unsuitable areas were decreased after 1997 than before in Xinjiang region, generally, climate warming was beneficial to walnut planting in Xinjiang during 1961-2015.

Grain Yield Loss Evaluation Based on Agro-meteorological Disaster Exposure in the Middle-Lower Yangtze Plain

ZHANG Yi，LIU Bu-chun，YANG Xiao-juan，LIU Yuan，BAI Wei，DONG Bo-chao

2018, 39(04):  280-291.  doi:10.3969/j.issn.1000-6362.2018.04.007

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Multiple linear regression analysis was used to identify the relationship between grain climate yield loss and the covered, affected and destroyed areas of crop, based on statistical data of crop disasters and grain yield (1949-2014) in the Middle Lower Yangtze Plain. Principal component analysis (PCA) was used to evaluate the impacts of main agro-meteorological disasters on grain climate loss. The results showed that the grain climate yield loss was significantly correlated with the whole disaster exposure at the province level (P＜0.05), and the correlation also reached extremely significant (P＜0.01), except for Hunan province. Specifically, the affected area was more closely related to grain climate yield loss. The coefficients of determination (R2) of the whole disaster exposure of yield regression models were over 0.9 except for shanghai city. According to the correlation between grain climate yield and drought, flood, windstorm, chilling, and typhoon to establish the main disaster exposure yield model, R2 of model was higher than the whole disaster exposure yield model, except for Hunan province. However, there was no significant difference between the two models based on single factor variance analysis. Two types of model error were mainly due to the fluctuation of grain crop planting structure. The model of disaster damage and yield assessment established in this study simulated the relationship between disaster exposure and grain yield. The predication results indicated that the disaster exposure model would be used as the short-term prediction for grain yield in the Middle Lower Yangtze Plain by using the data of disaster area in 2015.