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20 October 2017, Volume 38 Issue 10

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Advances of Impacts and Adaptation of Climate Change on Crop Rotations in China

LIU Huan, XIONG Wei, LI Ying-chun, YANG Di

2017, 38(10):  613-631.  doi:10.3969/j.issn.1000-6362.2017.10.001

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As a major agricultural practice in mainland China, crop rotation that experiences multiple harvests during a certain period and in a same land plays a vital role in increasing its land productivity and securing national food production. To devise better adaption and increase national food production under a fasting warming world, it is necessary to add the understandings regarding statues of current crop rotation systems in China, impacts of climate change on the systems, and responses of the systems to various warming trajectories. This paper reviews latest works related to crop rotations, with particular focuses on the responses of crop rotations to historical and future climate change. Most studies investigate the interactions between crop rotation and climate change based on three methods: crop modeling, statistical analysis, and field experiment, each method exhibits specific defects and merits. Authors summarize current understandings about the influence of climate change on crop rotation from four aspects: crop growth, crop spatial distribution, cost and benefits, and production risks. Authors explore adaptive practices in rotations and in the end recommend research directions for the future. This review increases the understandings about the impact of climate change on crop rotations and provides useful information for developing wise rotation strategy in coping with climate change. Previous studies illustrated that climate change has already affected and would continue to influence crop rotations, but discrepancies existed among studies because differences in spatial and temporal scales, methodology, and research subjective. Majority of the studies showed that warmer climate and increasing heat resource made it possible for some rotation systems to move north, which had substantially altered crop patterns and shifted planting area for a few major crops. Higher temperature physiologically speeds up crop growth, accelerating crop phenology and leading to lower yield. But this acceleration, on the other hand, creates great opportunities for switching of crop varieties and replacement of crop type. The increases in total heat resources during the growing-season lead to spatial and temporal variations of climatic disasters, requiring reconsideration of conventional copping strategies. For example, although reduction of cold disaster has been observed in many crop areas, on the contrary, the occurrence of the cold disaster actually has increased recently in many crop areas due to shifting of planting boundaries and over-adaptations. Together with increased heat stresses under warming climate, these new disaster patterns posed additional threats for alleviation of agricultural climate disasters, jeopardizing the productivity, stability, and sustainability of many rotation systems. Theoretically, yield loss caused by climate change could be offset by appropriate adjustment of crop patterns, adoption of new crop varieties, such as cultivars with longer growth period, and optimization of management practices. However, because of complexity of the systems, we failed to make a concrete and consistent conclusion regarding the interactions between climate change and crop rotation based on reviewed researches. Future works are recommended to emphasize the integration of multi methods to increase understandings related to mechanism, comprehension, and systematization of crop rotation systems, and to pursue in-depth investigation with wider connection between climate change and crop rotation and decreasing research uncertainty.

Errors Transmission of Radiation Estimation in APSIM Maize Model

MAO Yang-yang, ZHAO Yan-xia, ZHANG Yi, HU Zheng-hua, WEI Liang

2017, 38(10):  632-643.  doi:10.3969/j.issn.1000-6362.2017.10.002

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Taking three typical maize land sites in North China (Juxian station in Shandong province, Zhengzhou and Nanyang stations in Henan province) as the research objects, the effects of radiation models on crop yield simulation were investigated. Five radiation models, including the Angstrom-Prescott (A-P) model, Ogelman model, the Bahel model, the comprehensive model of sunshine duration and diurnal temperature range model (referred to as the comprehensive model), and Liu’s model (followed by simulation scheme 1-5) , were used to simulate the total solar radiation and validated against measurement (simulation scheme 0). The radiation results of the five models were further utilized to drive APSIM model to simulate the maize yield. The results showed that the estimated errors（εi）of A-P model was the smallest in the Juxian station, and that of the comprehensive model was the smallest in Zhengzhou and Nanyang stations. Different radiation estimation models had significantly different effects on yield simulation results of APSIM model, scheme 4 rendered the best result. The radiation errors brought by the five radiation models had enlarged the final results of maize yield simulated by APSIM model. The propagation error transferred to APSIM maize model simulation yield was 2.23, 2.28, 1.63, 1.85, 1.90 for the A-P model, the Ogelman model, the Bahel model, the comprehensive model, and the Liu’s model, respectively. It is obvious that the selection of the radiation model and the empirical coefficient of the radiation model should be taken into full consideration; with regard to the errors of crop yield simulation caused by radiation models two factors should be taken into account: the errors of the five radiation models and these errors transmitted to the crop model with augmentation. Generally speaking, Scheme 4 has the smallest error compared with other schemes. Therefore it was recommended to use scheme 4 to drive APSIM model in the absence of field measured radiation.

Simulation of Light Response of Photosynthesis of Cucumis sativus L. Leaves under Water Stress

ZHANG Man-yi, YANG Zai-qiang, HOU Meng-yuan

2017, 38(10):  644-654.  doi:10.3969/j.issn.1000-6362.2017.10.003

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For Cucumis sativus L. (cv. Boxin525), four different soil moisture levels were designed, which were normal irrigation (CK, soil relative humidity was 70%-80%), light water stress (T1, soil relative humidity was 60%-70%), moderate water stress (T2, soil relative humidity was 50%-60%) and severe water stress (T3, soil relative humidity was 35%-45%), respectively. Light response curves of cucumber leaves were measured under each treatment using LI-6400 portable photosynthesis system. Four different models (i.e. rectangular hyperbola, non-rectangular hyperbola, exponential and Ye Z P model) were applied to simulate light response curves of cucumber leaves, and the simulation effects were evaluated by statistics methods. Based on the experimental data and simulation results, the effect of water stress on light response curves of cucumber was discussed. The results indicated that water stress caused decline of net photosynthetic rate (Pn), at a PAR (photosynthetically active radiation) level of 800μmol·m-2·s-1, Pn decreased by 17.92%, 26.49% and 50.00% under T1, T2 and T3 treatments, respectively, compared with CK. The simulated light response curves showed a similar trend with the measured ones in response to water stress, and the variation amplitude of Pn-PAR curve decreased as water stress aggravated. Water stress affected light response curve parameters of cucumber leaves significantly. The initial quantum efficiency of cucumber leaves derived from the four mentioned models all increased at first and dropped afterwards with the aggravation of water stress, and the dark respiration rate was the highest under T2 treatment. Compared to CK, the average light saturation point calculated by four models decreased by 24.28%, 31.99% and 38.33%, respectively, under T1, T2 and T3, and the average maximum net photosynthetic rate declined by 23.88%, 33.19% and 55.78%, respectively, under T1, T2 and T3. The deviation degree of simulated light response curve and mean relative error of light response parameters achieved the lowest under CK, and the simulation effects of light response curve were weakened by water stress. The Ye Z P model performed best in simulation of the light response curve, next was the exponential model, the non-rectangular model, and the rectangular hyperbola model was the least effective one. The study indicated water stress significantly influenced light response of photosynthesis of cucumber leaves, and reduced photosynthetic capacity of leaves.

Projected Changes in Extreme Precipitation Events in Guizhou Based on CMIP5 Simulations over the 21st Century

ZHANG Jiao-yan，LI Yang，ZHANG Dong-hai，CHEN Zhen-hong，YANG Yi

2017, 38(10):  655-662.  doi:10.3969/j.issn.1000-6362.2017.10.004

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Under three different scenarios of greenhouse gas emission including RCP8.5, 4.5 and 2.5, the daily precipitation data in Guizhou, covering the period of 2006-2016 from 8 CMIP5 models provided by the National Climate Center, were examined in this study by using the Taylor diagrams. The data from two models (CCSM4 and IPSL-CM5A-MR) with the best simulation results were selected to calculate the extreme precipitation indices during three periods of 2018-2044, 2045-2071 and 2072-2098 subsequently. The indices included maximum number of consecutive dry days(CDD), numbers of days with precipitation ≥20mm·d-1(R20mm), maximum 5 day precipitation total(Rx5day) and simple daily intensity index(SDII), respectively, in comparison to those during the period 1986-2005. It was indicated that the CDD over the eastern regions grew during the 21st century under the three RCPs scenarios and the increase was proportional to the emission scenario. This described that more attention should be paid on the potential drought over the eastern Guizhou in future. Besides, the increases in R20mm, Rx5day and SDII were also detected in Guizhou during the 21st century. In the late 21st century, the increment of the extreme precipitation was more obvious under high emission(RCP8.5) than those under lower emission (RCP4.5 and 2.6). Overall, it was suggested that extreme precipitation events over Guizhou showed an uprising trend with more gas emission, under the background of the global warming.

Effect of Silicate Application on Rice Physiological Properties under Nighttime Warming

ZHENG Ze-hua, LOU Yun-sheng, ZUO Hui-ting, SHI Yi-fan, WANG Ying

2017, 38(10):  663-671.  doi:10.3969/j.issn.1000-6362.2017.10.005

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Field experiment with rice was conducted to investigate the effects of silicate (Si) application on variations of net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductivity (Gs) and intercellular CO2 concentration (Ci) at the tillering stage, jointing stage, filling stage, maturity stage under nighttime warming. The experiment was designed with two nighttime warming levels, i.e. nighttime warming (NW) and control (CK, ambient temperature), and two Si application levels, i.e. control (Si0) and Si1 (slag fertilizer, 200kg SiO2·ha-1). The results showed that, (1) nighttime warming increased the temperature of rice canopy and of 5cm depth soil by 1.21℃ and 0.41℃ at night (19：00-6：00) during entire rice growth season. (2) Nighttime warming decreased Pn, Tr, Gs by 11.0%, 9.0% and 20.2%, but increased Ci by 1.2%. Silicate application increased Pn and Gs by 16.1% and 25.8%, but decreased Tr and Ci by 11.0% and 2.0%; silicate application increased Pn and Gs by 22.0% and 33.6%, but decreased Tr and Ci by 7.7% and 2.3% under nighttime warming. It is suggested that nighttime warming decreased Pn, Tr and Gs, but increased Ci, in contrast, silicate application increased Pn and Gs, but decreased Tr and Ci. Namely, silicate application mitigated obviously the depressive effects of nighttime warming on photosynthetic properties. (3) The effect of nighttime warming or silicate application on chlorophyll content (SPAD value) was not obvious. Nighttime warming decreased SPAD value by 3.0%, but silicate application increased SPAD value by 4.7%. Compared with Si0, silicate application increased SPAD value by 5.7% under nighttime warming.

Heat Flux Changes at Junction between Root Zone Matrix and Soil Ridge of Sweet Pepper

LI Zong-geng, FU Guo-hai, LIU Wen-ke

2017, 38(10):  672-678.  doi:10.3969/j.issn.1000-6362.2017.10.006

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A novel soil-ridged substrate-embedded cultivation (SSC) method was used to cultivate sweet peppers in Chinese solar greenhouse. Five treatments, including soil ridge (SR), normal ridge (NR), narrow normal ridge (NRn), short normal ridge (NRs) and the double plant density of the normal ridge (NRd), were set to observe diurnal heat flux changes of east and west horizontal directions and the vertical direction of the root zone by using heat flux plates, and select a kind of ridge which was most suitable for vegetables winter production in Chinese solar greenhouse. The results showed that soil heat flux of each treatment presented unimodal curve diurnal changes synchronously, but the time of heat absorption and heat release were different. For east horizontal direction of ridges, the root zones of SR, NR, NRn and NRd absorbed heat at 9：00-14：00 on sunny days, and the time of heat absorbing delayed 2 hours on cloudy days. NRs absorbed heat at 23：00-14：00 on sunny days, and NRs absorbed heat all day when it was cloudy. For west horizontal direction of ridges, NRs absorbed heat all the time, and the rest four treatments absorbed heat at 9：00-17：00. In the vertical direction of root zone, heat flux changes showed that SR, NR, NRn and NRd absorbed heat at 11：00-18：00 in sunny days and 12：00-17：00 in cloudy days. Release heat time of NRs was 2-3 hours later than other treatments. Difference of heat absorption and release of five treatments changed with different locations on horizontal directions of east and west and vertical direction of root zone. Each treatment primarily absorbed heat on the horizontal direction of east side and vertical direction of root zone, but released heat on the horizontal direction of west side. In the junction between east and west lateral soil of ridge and matrix of root zone, the heat absorbed by the root zone of NRs was larger than that of the exothermic heat, while that of NRd was much less than released. So NRd treatment could maintain well root zone temperature in winter, it had a better application prospect in vegetables production in winter and early spring in Chinese solar greenhouse.

Weather Index Insurance Design of Middle-Season Rice Heat Damage Based on Regional Difference of Flowering Stage

LIU Kai-wen, LIU Ke-qun, DENG Ai-juan, YANG Tao, SU Rong-rui, XI Wang, FENG Ming

2017, 38(10):  679-688.  doi:10.3969/j.issn.1000-6362.2017.10.007

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Under the control of open top chamber (OTC), rice “Guangliangyouxiang 66” was tested to simulate heat damage during heading and early grain filling periods. The relationship model of heat damage and yield reduction was established, and its accuracy was verified by field investigation data. Based on the historical observation data of the highest temperature of each day between July 16th and August 31st from 1981 to 2016, the Weibull model was used to establish the heat damage risk distribution model of the pilot counties. Subsequently, according to these two models, a variety of pure premium rate scheme of the pilot counties was determined in different deductible excess and insurance period, for providing various choices. The results showed that, 20 days after initial flowering period was the optimal insurance period length of heat damage insurance about heading and early grain filling periods. The pure premium rate achieved the lowest value when flowering in late July, and decreased gradually with flowering delay. Between different regions, pure premium rate fluctuated greatly, in which, the high value regions of pure premium rates are in the mountainous regions of southeast of Hubei province such as Xian’an, Chibi, Xishui and Macheng, and the humpy ground in northern Hubei, such as Xiangyang and Suizhou, were divided into low risk area.