中国生态农业学报(中英文)

Spatio-temporal evolution characteristics of agro-ecosystem adaptability response to global change in South China hilly regions: A case study of Hengyang Basin

ZHOU Songxiu, CHEN Linlin, LIU Lanfang, WANG Peng

2017, 25(2): 147-156. doi: 10.13930/j.cnki.cjea.160884

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Abstract:
There is renewed interest in the evolution of the adaptability of ecosystem to global change. It is important to study rice farming regions in hilly areas of Hengyang Basin. As a rice-based agricultural region, it is very important to study the adaptability of agricultural ecosystem (AAE) in South China. Previous studies have shown that in Hengyang Basin, a typical agricultural ecosystem in South China, obvious spatial distribution patterns of AAE were higher in periphery regions and lower in the middle regions of the basin. However, the temporal and spatial variation characteristics of AAE were not completely clear. This research used Hengyang Basin as a case study to build the evaluation index system consisting of 12 indicators ranging from natural to social and then to economic aspects. The evaluation unit consisted of Hengyang Basin and the surrounding counties. The AAE index for Hengyang Basin was calculated using an entropy method and 16 years of data (1999-2014) to determine index weight. The results showed that a complex and highly different spatio-temporal variations in AAE in Hengyang Basin for the different counties and different years. However, the range of the AAE index for the eight counties (cities) in the basin was 0.249 8-0.679 4, which indicated a medium and high AAE level in the region. In the eight counties (cities), Leiyang City had the highest AAE, followed by Qidong County, and Changning County was the weakest. The coefficients of variation for the different counties (cities) showed that change in AAE was highest for Changning City and lowest for Hengnan County for the period 1999-2014. There was a wave-like trend in AAE for Leiyang City with rises and falls. The evaluated 16 years was divided into three periods-the period 1999-2004 was the period of low index and small amplitude oscillation, the period 2005-2010 was the one of an overall rise with significant fluctuation in adaptability, and then the period 2010-2014 was the period of rapid rise AAE index. The conclusions in this study provided a useful reference to guide sustainable agricultural development in the hilly regions of South China.

Evaluation of net carbon sink effects and costs/benefits of double-cropped rice fields under different organic fertilizer applications

HU Zhihua, LI Daming, XU Xiaolin, YU Xichu, LIU Kailou, YE Huicai, ZHOU Lijun, HU Huiwen, HUANG Qinghai

2017, 25(2): 157-165. doi: 10.13930/j.cnki.cjea.160725

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Abstract:
For theoretical reference on low carbon, high profit and efficient agriculture, a long-term organic fertilizer experiment was conducted since 1981 to study the effects and economic benefits of different organic fertilizers, fertilizer doses and application methods on carbon emission and carbon sink in paddy field ecosystems. Treatments of non-fertilizer (control), Astragalus sinicus application in early rice (15 t·hm^-2) (M1), double amount of A. sinicus application in early rice (30 t·hm^-2) (M2), A. sinicus application (15 t·hm^-2) plus pig manure application (15 t·hm^-2) in early rice (M3), A. sinicus application in early rice (15 t·hm^-2) plus pig manure application in late rice (15 t·hm^-2) with straw mulching (4 500 kg·hm^-2) in winter (M4), and NPK-chemical fertilizer in both early and late rice (NPK) were set up in the experiment. The soil samples were collected once every five years to measure organic carbon content after late rice harvest. Then rice biomass and yield were measured once every five years to evaluate the economic and carbon costs/benefits (5-year average) of the ecosystem after early rice and late rice harvest. Results showed that compared with the control, M1, M2, M3, M4 and NPK treatments significantly increased rice yield (P<0.05) in a range of 30.88%-96.52%. Increase in the years promoted rice yield most under M4 treatment. Long-term organic fertilizer application significantly increased SOC (soil organic carbon) content and soil carbon sink ability. Soil carbon sink of M2, M3 and M4 treatments were significantly higher than that of M1, NPK and CK treatments. Crop carbon sink under long-term organic fertilization treatments, which was 6.76-8.83 t(C)·hm^-2·a^-1 for double-cropped rice, was improved greatly. Compared with the control, net carbon sink under M1, M2, M3, M4 and NPK treatments increased significantly (P<0.05) with increment of 1.43-3.93 t(C)·hm^-2·a^-1. Carbon emission caused by production activity of each treatment remained unchanged for different years of fertilizer application. The differences in net carbon sink among treatments were mainly caused by variation in carbon sink of ecosystem, whose changing trend was similar to that of rice yield. Long-term organic fertilizer application significantly reduced chemical fertilizer input, but also significantly increased the economic benefits of double-cropped rice (P<0.05) to a maximum of 25 683.7 ￥·hm^-2·a^-1 (under M4 treatment). In conclusion, long-term organic fertilizer application significantly increased soil carbon sink and economic benefits. Besides, an integrated application of A. sinicus, pig manure and crop straw was obviously advantageous over sole application of A. sinicus in terms of increasing net carbon sink effects and economic benefits of paddy field ecosystem.

Differentiation regularity of Acyrthosiphon pisum (green form) sexual morphs in relation to photoperiods

ZHANG Tingwei, CHEN Wanbin, LIU Changzhong, CUI Shaowei, RAO Fuqiang

2017, 25(2): 166-171. doi: 10.13930/j.cnki.cjea.160663

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Abstract:
In order to clarify population reproduction strategy and differentiation regularity of Acyrthosiphon pisum (green form) sexual morph in relation to photoperiods, the pea aphid sexual morphs were observed after 2 continuous generations at different photoperiods (8L:16D, 10L:14D, 12L:12D and 14L:10D) in the lab. The results showed that the ovipara of pea aphid in Lanzhou area were wingless, while males were winged. Photoperiod had a significant effect on the differentiation of pea aphid sexual morphs (P<0.05). No sexual morph was produced at 14L:10D photoperiod, but a lot were differentiated under the other photoperiods (8L:16D, 10L:14D and 12L:12D). In the shorter photoperiod conditions for the 3^rd generation, percent male sexual morphs gradually diminished while percent ovipara gradually increased with decreasing illumination time. Percent male was highest (30.39%) at 12L:12D photoperiod, while percent ovipara was lowest (55.67%) at that photoperiod. At 10L:14D photoperiod, percent vivipara was highest while percent sexual morphs was lowest. Then at 8L:16D photoperiod, no male was produced and percent ovipara was highest (90.76%) in the 3^rd generation. The reproductive period of the 1^st generation also had a significant effect on the differentiation of sexual morphs in the 3^rd generation under similar short illumination conditions (P<0.05). Meanwhile, there was a certain time sequence in which pea aphid sexual morphs were differentiated (first ovipara and last males) with some vivipara transitioning to sexual morphs. Hence the critical photoperiod of green pea aphid was between 12 to 14 hours of illumination. A relatively longer illumination was advantageous to the differentiation of males, while short illumination favored higher proportion of ovipara. The results suggested that change in photoperiod was a critical factor of reproductive plasticity. The reproduction of pea aphid sexual morphs and the illumination length maternal pea aphid experienced influenced sexual differentiation of offsprings.

Farmland buffer strip planning, construction and protective effect on related natural enemy

LIU Wei'er, ZHANG Xin, ZHANG Juan, LIU Yunhui, YU Zhenrong

2017, 25(2): 172-179. doi: 10.13930/j.cnki.cjea.160592

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Abstract:
At present, the application of buffer strips is becoming increasingly important in the development of modern eco-agriculture both at national and international scales. With proper design and construction, farmland buffer strips (e.g., field margins, wild flower strips, hedgerows and shelterbelts) can provide various ecosystem and landscape services, including erosion prevention, non-point pollution control, natural pollination, pest control and landscape pattern optimization. This paper used the construction project of Modern Urban Agricultural Demonstration Farm in Shunyi District in Beijing to discuss the concept, classification, functions and planning methods of farmland buffer strips. Backed by literature review, the study demonstrated integrated spatial planning and construction of farmland buffer strips and assessed natural enemy protection service of 4 typical buffer strips by sampling and measuring the density of spiders and natural enemies/aphids ratio. The study showed that:1) Farmland buffer strips can be defined as "a strip vegetation mosaic separating different landscape features and patches in an agricultural landscape". This classification measure of farmland buffer strips was based on 3 attributes-location and neighboring land use, vegetation composition and structure, and ecosystem services types. Ecosystem and landscape services were the main factors considered during planning of buffer strips. The planning process of farmland buffer strips was summarized into 5 steps-target identification, on-site investigation, spatial arrangement planning, construction pattern design, and supervision and management. 2) According to the landscape pattern and ecosystem services demand in the study area, the study proposed a spatial arrangement of farmland buffer strips that consisted of 3 types with a total of 7 construction patterns designed in combination with the construction of field ditches, roads and shelterbelts. The results of the assessment of natural enemy protection service showed that the area 10 m within wheat fields near shelterbelt buffer strips had the highest density of spiders. Also the ratio of natural enemies to aphids in wheat fields near artificial field margins (including field ditches and road buffer strips) was largest. To some degree, the evaluation showed the efficacy of farmland buffer strips in providing natural enemy protection service, although the results could have been affected by the short monitoring time at the early stage of the development of buffer strip vegetation and disturbance to wildlife during construction. 4) The study further showed that future development of eco-agriculture should take into consideration integration of farmland buffer strips and other ecological conservational practices along with the related spatial planning and implementation at larger scales. The application of such approach needed adjustment to specific local conditions as the paper only discussed the implementation of farmland buffer strips under dryland farming in plain areas. The overall effectiveness of such approach needed a more thorough assessment with long-term monitoring of a variety of indicators that account for the status of soil, watershed, biodiversity and other landscape characteristics.

Effect of tillage and straw retention mode on seedling emergence and yield of spring wheat in the Hexi Irrigation Area

YIN Wen, CHEN Guiping, CHAI Qiang, GUO Yao, FENG Fuxue, ZHAO Cai, YU Aizhong, LIU Chang

2017, 25(2): 180-187. doi: 10.13930/j.cnki.cjea.160788

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Abstract:
Seedling emergence rate and uniformity of crops determine their growth and yield performance, while straw retention and tillage mode play an important role on seedling emergence and growth of corps. To explore the responses of seedling emergence and yield of crops to straw retention and tillage practices, a field experiment was carried out in a typical oasis irrigation region, Wuwei, Gansu Province, in 2014 and 2015, to determine the effects of treatments of straw retention combined with tillage patterns on seedling emergence, yield, and yield components of spring wheat. The treatments included reduced tillage with 25 to 30 cm high straw standing (NTSS), reduced tillage with 25 to 30 cm long straw covering (NTS), tillage with 25 to 30 cm long straw incorporation (TS), and conventional tillage without straw retention (CT, the control). The results showed that, compared with CT, reduced tillage combined with straw retention treatments (NTSS, NTS) significantly decreased seedling emergence evenness of wheat, while TS increased seedling emergence evenness. NTSS and NTS increased spring wheat tiller number by 7.4% to 10.5% and 14.6% to 19.1%, effective spike rate of tiller by 13.5% to 20.1% and 33.0% to 34.7%, spike number by 7.5% to 9.3% and 10.3% to 11.2%, kernel number per spike by 15.7% to 16.1% and 18.5% to 22.6%, and thousand-kernel weight by 7.2% to 8.9% and 13.9% to 14.2%, compared with CT, respectively. There was no significant difference between TS and CT treatments in the above parameters. NTSS and NTS treatments had 16.6% to 17.4% and 18.6% to 21.4% higher grain yield than CT. NTS had the highest increasing effect on wheat grain yield, which was 10.3% to 11.0% higher under NTS than under TS. The increase of spike number and kernel number per spike was the main reason for yield increase under reduced tillage with straw retention treatments. However, emergence rate and uniformity had no significant impact on wheat production. Meanwhile, NTSS, NTS treatments were 9.4% to 10.7% and 10.5% to 11.1% greater in harvest index than CT treatment, indicating higher conversion rate of photoassimilates in wheat under the two treatments. Therefore, our results showed that reduced tillage in combination with 25 to 30 cm high straw retention was the feasible technology of wheat production in the oasis irrigation region.

Nutrient release patterns and decomposition characteristics of different crop straws in drylands and paddy fields

DAI Wencai, GAO Ming, LAN Muling, HUANG Rong, WANG Jinzhu, WANG Zifang, HAN Xiaofei

2017, 25(2): 188-199. doi: 10.13930/j.cnki.cjea.160748

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Abstract:
To provide theoretical basis for crop straws recycling and straw use in agricultural fields, the characteristics of decomposition and release of nutrients of different crop straws[rice, wheat, corn, rapeseed (green stalk) and broad bean (green stalk)] were studied using the nylon net bag method in drylands and paddy fields. The results showed that the decomposition rate of straw was high at the early phase (0-60 d) which then dropped at the later phase (60-360 d). After 360 d, the cumulative decomposition rates of straw were 52.88%-75.80% and 45.01%-62.12% in drylands and paddy fields, respectively. The cumulative decomposition rate of broad bean was significantly lower than that of other crops in the two fields. Furthermore, rapeseed and rice decomposed faster in drylands and paddy fields. At the endpoint of the experiment, the sequence of nutrient release rate of straw in the two fields was K > P > N > C. The rate of carbon release by rice, corn, wheat, rapeseed and broad bean straws was up to 87.37% in dryland and 69.57% in paddy field. The rates of carbon release by rapeseed and rice were significantly higher than those of other crop straws in dryland and paddy field. The average rate of nitrogen release by the five straws tracked the following trend:broad bean (69.72%) > rice (68.45%) > rapeseed (63.60%) > corn (57.28%) > wheat (54.64%) in dryland. The rate of nitrogen release by broad bean was the highest (77.11%) in the paddy field. The rates of release of phosphorus by straw were 89.65%-98.96% and 90.70%-96.80% in dryland and paddy field, respectively. Then the rate of release of phosphorus by wheat was persistently lower than that of any other straw in both fields. The rate of release of potassium by rapeseed was respectively 20.91%, 5.84%, 6.67% and 5.19% higher than that of wheat, rice, corn and broad bean in dryland. Also the rate of release of potassium by wheat was significantly lower than the others. Overall, the decomposition and nutrient release rates in dryland were higher than those in paddy field. Rapeseed green straw in dryland, and rice and maize straws in paddy field were more easily decomposed than other crops straws. The release rate of potassium was highest in all the tested elements.

Response of nitrogen utilization to root interaction and plant density in barley-pea intercropping system

WANG Lili, ZHU Yongyong, ZHAO Yanhua, YIN Wen, CHAI Qiang

2017, 25(2): 200-210. doi: 10.13930/j.cnki.cjea.160530

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Abstract:
To investigate the mechanism of high planting density in cereal-legume intercropping system, a pot experiment of barley-pea intercropping system was carried out and the effects of nitrogen (N) application and root barrier on nitrogen and fertilizer use efficiency under high planting density of barley were determined. In the experiment, three factors, each with two treatment levels-N fertilizer application[no N application and N application with 100 mg(N)·kg^-1], root barrier[no barrier with root interaction and root barrier without root interaction) and planting density (low density with 15 barley plants per pot and high density with 25 barley plants per pot) were set up. The results showed that:1) N application, plant root interaction and high barley planting density improved N uptake of barley-pea intercropping system. Compared with no N application treatment, N uptake increased by 33.8% in N application treatment. There was also 81.1% increase in N uptake under no root barrier treatment over root barrier treatment. N uptake under high planting density treatment increased by 4.2% compared with low planting density treatment. Plant root interaction improved N uptake by 92.4% and 11.0%, respectively, under no N application and N application treatments. Increasing planting density with root interaction significantly increased N uptake of the intercropping system. 2) Barely plant performed better for N competition, and its' N competition ratio significantly increased under high planting density. However, N application reduced barley N competition ratio. Compared with pea, barley was highest in competitive advantage at heading stage. 3) Root interaction improved grain N content of barley and pea, respectively, by 126.7% and 26.9% under N application treatment. Also barley and pea kernel N content increased, respectively, by 188.5% and 46.5% under no N treatment. There was a significant interaction between N application and root interaction for kernel N content. 4) High barley planting density significantly improved N use efficiency by 59.8% under root interaction treatment of the intercropping system. N competition between barley and pea was positively correlated with N use efficiency in the intercropping plant population. In conclusion, interactions of N application, root barrier and barley planting density enhanced crop productivity of barley-pea intercropping system. Proper N application and sufficient root interaction made feasible high planting density intercropping system, optimized competition between barley and pea, and improved N uptake and use efficiency.

Effect of rice varieties mixed-cropping with duck raising on nutrient dynamics in paddy soils

LI Meijuan, ZHOU Nian, ZHANG Jia'en, XIANG Huimin, LIANG Kaiming

2017, 25(2): 211-220. doi: 10.13930/j.cnki.cjea.160484

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Abstract:
Rice-duck farming systems with different varieties of rice mixed-cropping could produce excellent ecological effects. However, it is for now largely unclear whether the synergy of the two farming systems (rice-duck farming and rice varieties mixed-cropping) could improve ecological conditions and production efficiency to have "1+1>2" effect when concurrently implemented. Because of large-scale rice monoculture with high application of pesticides and fertilizers, food and eco-environment security has increasingly worsened. To meet the demands for diverse taste and high-quality organic rice, and to further explore the feasibility of biodiversity model in different rice varieties mixed-cropping systems and duck-rice mixed-farming, an innovative double rice varieties mixed-cropping along with duck raising was set up and studied. To test the effects of the farming system on soil nutrient dynamics and rice quality, six different treatments were set up-including ‘Shengbasimiao’ rice variety mono-cropping with conventional farming practice (SC), ‘Shengbasimiao’ rice variety mono-cropping with duck raising (SD), ‘Shengbasimiao’ rice variety mono-cropping (CK1), mixed-cropping of rice varieties of ‘Shengbasimiao’ and ‘Huajingxian 74’ with conventional farming practice (MC), combined rice varieties of ‘Shengbasimiao’ and ‘Huajingxian 74’ mixed-cropping and duck raising (MD), and rice varieties of ‘Shengbasimiao’ and ‘Huajingxian 74’ mixed-cropping (CK2). After early and late rice planting in the first year, organic matter content of paddy soils under treatment MD was significantly higher than that under the other treatments. Although soil total nitrogen content in early rice planting under treatment MD was significantly lower than that under treatment MC, it was significantly higher than that under other treatments. After early and late rice planting, it was noted that soil alkali-hydrolyzable nitrogen content under treatment MD was significantly increased compared with that under the other treatments. The content of soil available phosphorus under CK1 was the highest among all the treatments. Generally, the average content of soil available phosphorus under rice varieties mixed-cropping systems was higher than that under rice variety mono-cropping systems. After rice cropping for one year, the contents of soil total potassium and available potassium under treatment MD were higher than those under the other treatments. Rice brown rate, milled rice rate, amylase content and gel consistency under MD were higher than those under the other treatments. However, the rate of chalky rice under MD was lower than that under the other treatments. In conclusion, the integrated farming systems of rice varieties mixed-cropping and duck raising improved soil nutrient and rice quality. This successfully tried a new farming system that ensured ecological health, and high-quality and high-yield rice production.

Effect of sowing date on dry matter accumulation and yield of maize in hilly regions of Sichuan Province, China

DOU Pan, LI Xiaodong, KONG Fanlei, WANG Xinglong, MA Xiaojun, ZHANG Jiali, YUAN Jichao

2017, 25(2): 221-229. doi: 10.13930/j.cnki.cjea.160631

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Abstract:
The main maize varieties (‘Zhenghong 505’ and ‘Chengdan 30’) were sowed at 5 dates with 15-day intervals from March 26^th to May 25^th in hilly regions of Central Sichuan Basin to investigate the effects of different sowing dates on the dry matter accumulation and yield of maize. The study also aimed at providing the theoretical basis for the selection of appropriate sowing date of maize in the hilly regions of Central Sichuan Basin. The results showed that with delayed sowing date, the growth period (especially the period from seeding to spinning) shortened, dry matter accumulation and its contribution to yield decreased after spinning and harvest index decreased. However, early sowing increased dry matter accumulation after flowering. Yield formation in late sowing needed more allocation and transport of accumulated photosynthate before flowering. The yield of ‘Zhenghong 505’ maize variety decreased with delayed sowing date, while, the yield of ‘Chengdan30’ slightly increased firstly and then decreasing with delayed sowing. There was no significant reduction in yield of early summer maize ‘Chengdan30’ sown on May 10 and spring maize sown on April 10. However, compared with spring maize, yield of summer ‘Chengdan30’ maize sown on May 25 decreased due to shortened growth period, low dry matter accumulation and low harvest index. For early spring sowing, yield of ‘Zhenghong 505’ maize variety was generally higher than that of ‘Chengdan 30’ maize variety. For summer maize, however, yield of ‘Chengdan 30’ maize variety was higher than that of ‘Zhenghong 505’ maize variety. This suggested that ‘Chengdan 30’ maize variety had a stronger vigor under summer sowing than ‘Zhenghong 505’ maize. Sowing date had greater effect on dry matter accumulation, yield and yield components of ‘Zhenghong 505’ maize than on ‘Chengdan 30’ maize. This indicated that a close attention should be paid to sowing date in maize cultivation. In the hilly regions of Central Sichuan Basin, the suitable sowing date range of spring maize was relatively wide, implying that the production obstacle was rather the contradiction between farming system and mechanized production. More attention should be paid to summer sowing in terms of selection of crop variety and sowing date, which should end by mid-April or early May.

Effect of LED supplemental lighting and root zone heating on growth and yield of soil ridged substrate-embedded sweet pepper in solar greenhouses in China

FU Guohai, YANG Qichang, LIU Wenke

2017, 25(2): 230-238. doi: 10.13930/j.cnki.cjea.160741

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Abstract:
In order to deal with resource and environmental issues of soil cultivation and sunlight deficiency and to enhance root-zone temperature for crop cultivation during low winter temperature periods in solar greenhouses in China, a field study was conducted with soil-ridged substrate-embedded cultivation (SRSC) method under greenhouse conditions to investigate the effect of root-zone heating and LED supplemental lighting on the growth and yield of sweet pepper. Six treatments were designed in the study, including the control without heating and lighting (CK), root zone heating at 15℃ (T15), root zone heating at 18℃ (T18), sole LED supplemental lighting (L), root zone heating at 15℃ plus LED supplemental lighting (T15+L) and root zone heating at 18℃ plus LED supplemental lighting (T18+L). The results showed that compared with CK, heating increased the root zone temperature under SRSC and root zone temperature changed with change in temperature of the environment. Root zone temperature under T18 was high throughout the day. Heat flux under T15 and T18 fluctuated with root zone heating and changed more violently than under CK. The data showed a lag in the time of inward heat transfer and an advance in the time of outward heat transfer with increasing root zone temperature in lateral and vertical directions, and there was more diurnal heat transfer in the vertical root zone. T15 and T18 treatments significantly increased plant height, canopy height and diameter of sweet pepper, which were more obvious under T18 than T15 treatments. The growth parameters of sweet pepper further improved with simultaneous root zone heating and LED supplemental lighting. Fresh and dry shoot and root weights of sweet pepper increased significantly under T18 than under T15 treatment. Plant biomass under simultaneous root zone heating and LED supplemental lighting was higher than that under root zone heating or sole LED supplemental lighting, and that under T18+L treatment was highest. Compared with CK, T15, T18 and L treatments improved sweet pepper yield by 30.74%, 53.0% and 14.81%, respectively. Furthermore, sweet pepper yield under T15+L and T18+L were respectively 32.86% and 15.50% higher than that under T15 and T18 and also 51.29% and 53.87% higher than that under L treatment. In summary, root zone heating and LED supplemental lighting proved to be beneficial agronomical soil cultivation measures in solar greenhouse conditions in China with high vegetable productivity and remarkably synergistic effect on single plant yield of sweet pepper. The interaction of root zone heating and LED supplemental lighting was more obvious than that of the single effect of the treatments. Also the effect of root zone heating on the growth and yield of sweet pepper was more obvious than that of LED supplemental lighting. The results of the study provided an important guide in actual crop production under solar greenhouse conditions in China.

Effect of phosphorus on leaf net photosynthesis, protective enzyme activity and nutrient uptake of maize at seedling stage in fluvo-aquic soils under water stress

LU Chuang, PANG Huancheng, ZHAO Changhai, WANG Jing, CHANG Xiaolian, LI Yuyi

2017, 25(2): 239-246. doi: 10.13930/j.cnki.cjea.160646

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Abstract:
Water stress is a major limiting factor of seedling maize in fluvo-aquic soils. A pot experiment was conducted under greenhouse conditions to study the effect of water stress and P application on net photosynthetic rate (P_n), leaf protective enzymes activities and nutrients contents of maize at seedling stage. The experiment consisted of two water and five P treatments. The water treatments included water stress (W₁, 70%-75% of field capacity) and sufficient water (W₂, 85%-90% of field capacity), the P treatments included 0 g(P)·kg^-1(soil) (P₁), 0.05 g(P)·kg^-1(soil) (P₂), 0.10 g(P)·kg^-1(soil) (P₃), 0.15 g(P)·kg^-1 (soil) (P₄) and 0.20 g(P)·kg^-1(soil) (P₅). The results showed that compared with W₂, W₁ treatment decreased P_n of maize leaf by 27.96%. Water stress significantly improved mean MDA content of maize leaf by 41.93%. But water stress decreased POD and CAT activities of maize leaf. Under W₁ treatment, P_n significantly increased by 27.56% at P₂ level over P₁ level, but further increased in P supply had no significantly promoting effect on P_n. The inhibition effect of P use on MDA under W₁ was significantly lower than that under W₂ treatment. The activities of POD and CAT were maximum at P₃ level under W₁, while those of POD and CAT were maximum at P₄ level under W₂ treatment. It was also noted that suitable P treatments (P₂, P₃ and P₄) beneficially increased N and P contents of maize plant, while it had little effect on K content under W₁ Treatment. Under W₂ treatment, increase in P supply beneficially increased N and P contents, but decreased K content of maize. In conclusion, suitable P application had a compensation effect on water stress in seedling maize in fluvo-aquic soils. Under the experimental conditions, P₃ treatment more favored the accumulation of photosynthetic processes and enhanced stress resistance of maize.

Response of maize canopy to environmental factors in the middle reach oasis of Heihe River Basin

WU Lin, LIU Xingran, MIN Leilei, SHEN Yanjun, LIU Fenggui, ZHOU Xiaoxu

2017, 25(2): 247-257. doi: 10.13930/j.cnki.cjea.160772

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Abstract:
Evapotr_anspir_ation (ET) is critical for energy and water balance in agricultur_al systems. Accur_ate estimation or measurement of ET is therefore important in improving water use efficiency and optimizing the structure of regional water use. Canopy resistance is one of the most important variables in the estimation of ET. The accur_acy of simulation of the response process of canopy resistance to environmental variables is critically important for crop ET research. A convenient approach to simulate the response process of canopy resistance to multiple factors is based on the relationship between measured latent heat, climatic variables and by using the modified Penman-Monteith (P-M) equation. However, this method has certain limitations in some pr_actical applications due to the lack of a few effective par_ameters. Another approach is to construct empirical and semi-empirical models using multiple factors (such as the Irmak model) based on measured data combined with the rearr_anged P-M equation. Based on canopy resistance values calculated by the rearr_anged P-M equation and on maize data (for the period May to September 2012) collected from the three eddy covariance observation stations in Heihe River Basin, this study constructed Irmak model taking into account the effect of atmospheric CO₂ concentr_ation of half-hourly and daily time-steps to simulate the response processes of maize to environmental variables such as net r_adiation (R_n), air temper_ature (T_a), leaf area index (LAI), relative humidity (RH), wind speed (U₃), aerodynamic resistance (r_a), effective soil water content (θ) and atmospheric CO₂ concentr_ation. In the study, the performance of the two Irmak models were tested with measured values of latent heat from the eddy covariance systems of the other two verification points. Besides, the sensitivity of environmental variables was analyzed. The results indicated that the improved Irmak model which took into account the effect of atmospheric CO₂ concentr_ation well estimated canopy resistance and ET. The coefficients of determination (R²) for canopy resistance and ET were respectively 0.76 and 0.95 for the calibr_ation phase, with root mean square errors (RMSE) of 33.1 s·m^-1 and 34.5 W·m^-2. Meanwhile, R² for canopy resistance and ET were respectively 0.68 and 0.90 for the validation phase, with RMSE of 63.2 s·m^-1 and 49.0 W·m^-2. The two verification points showed that the improved Irmak model had a good performance and strong regional applicability and spatial portability. The model also simulated the response processes of canopy resistance to environmental variables and reflected the effect of the variations in atmospheric CO₂ concentr_ation on ET. Sensitivity analysis of the improved Irmak model showed that canopy and ET were the most sensitive to net r_adiation and relative humidity, followed by air temper_ature, leaf area index and atmospheric CO₂ concentr_ation. The improved Irmak model used in this study was applicable in estimating crop water consumption and the accur_acy of ET of maize, in providing scientific basis for improvements in water use efficiency and in optimizing the structure of regional water use under increased future atmospheric CO₂ concentr_ation.

Effect of tillage method on soil water infiltration, organic carbon content and structure

YANG Yonghui, WU Jicheng, ZHANG Jiemei, PAN Xiaoying, WANG Yue, HE Fang

2017, 25(2): 258-266. doi: 10.13930/j.cnki.cjea.160720

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Abstract:
Long-term tillage can greatly influence the physical properties of soil profile. For example, subsoiling and no-tillage can increase soil organic matter content, improve soil structure, increase the stability of soil structure and thereby improve soil moisture environment. In addition, no-tillage and subsoiling rotation can significantly improve soil water storage. Most reported studies were on no-tillage with mulching or subsoiling with mulching or no-tillage and subsoiling rotation. And the investigated soil profiles were usually focused on the ploughed layer. However, the effect of long-term subsoiling or no-tillage without mulching on the physical properties, infiltration processes, organic carbon distribution and structure of soil, especially for the deep soil has been rarely reported. Thus the objective of the study was to explore the effects of long-term no-tillage, subsoiling and conventional tillage, all without mulching, on the structure and water infiltration processes of the soil profile. An undisturbed 0-100 cm soil column, and the ring-cut samples of undisturbed soil and mixed soil samples of the 0-10 cm, 10-20 cm,…, 90-100 cm layers were collected in a long-term field experiment to determine the soil infiltration processes, saturated hydraulic conductivity, soil organic carbon content and soil structure. The results showed that the time for water infiltrating from the surface to the bottom of soil column under conventional tillage was longest among all treatments. The orders of permeability rate and cumulative infiltration of soil column were as follow:subsoiling > no-tillage > tillage. Then time for cumulative evaporation of the soil column arranged from max to min was from conventional tillage to no-tillage and then to subsoiling. Also the order of saturated hydraulic conductivity in the 0-10 cm and 50-60 cm soil layers was no-tillage > subsoiling > conventional tillage, and that in 20-50 cm and 60-100 cm soil layers was subsoiling > no-tillage > conventional tillage. With the increasing depth of soil, the content of > 0.25 mm water-stable aggregates and soil organic carbon initially increased (10-20 cm layer) and then gradually decreased. In the 0-40 cm and 80-100 cm soil layer, the content of > 0.25 mm water-stable aggregates under subsoiling was highest. The order of soil organic carbon content in the 0-60 cm soil layer was no-tillage > subsoiling > conventional tillage. While soil organic carbon below the 60 cm layer of all the treatments was lower than 4.0 g·kg^-1, and followed the order of conventional tillage > no-tillage > subsoiling below the 70 cm soil layer. It was therefore concluded that reasonable tillage improved soil organic carbon content and soil structure, and then promoted soil water conservation. Subsoiling was more favorable to soil water infiltration and no-tillage more conducive for organic carbon and water storage, especially in the 0-60 cm soil layer.

Decomposition process and CO₂ release characteristics of spent mushroom substrate in paddy soils

LI Fangliang, WANG Huangping, ZHANG Qing, WANG Limin, AN Mengyu, LUO Tao

2017, 25(2): 267-275. doi: 10.13930/j.cnki.cjea.160678

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Abstract:
Spent mushroom substrate (SMS), leftovers after cultivation of mushroom, could serve as an organic fertilizer. In this study, different proportions of SMS were mixed into paddy rice soils under laboratory conditions to study the relationship between application of SMS and soil organic carbon decomposition, and further provide reference for the rational utilization of SMS for sustainable agricultural development. The study consisted of 5 treatments-no SMS application (TS), SMS mix with paddy rice soil at 10:1 (SM1), SMS mix with paddy rice soil at 5:1 (SM2), SMS mix with paddy rice soil at 2:1 (SM3) and sole SMS medium (TM). Then changes in soil organic carbon and nitrogen, decomposition process of organic carbon in soils and CO₂ release characteristics in each treatment were determined. The results showed that soil organic carbon and total nitrogen contents under different proportions of SMS treatments were significantly higher than those under TS treatment for the same incubation time. Increase in organic carbon and total nitrogen contents mainly depended on the amount of SMS added to the soil. TM treatment showed the most obvious effect, which increased soil organic carbon and total nitrogen contents by 10.7 and 11.0 times, respectively. With increasing duration of incubation time, soil organic carbon and nitrogen decreased with the decomposition of carbon and nitrogen in all the treatments. Also organic carbon and nitrogen decreased relatively quickly under TM treatment after 35 d. The more SMS supply, the greater was the residue rate. After 63 d of cultivation, the relationships between the residue rates of organic carbon (Y_C) and nitrogen (Y_N) with the amount of SMS (X) were as follows:Y_C=71.26X-0.607 5 (r²=1.000 0^**) and Y_N=74.039X-0.413 3 (r²=0.999 9^**). The release rates of CO₂ in all the treatments increased initially and then decreased before stabilization. The higher the amount of SMS, the higher was the release rate of CO₂. On the 7^th d after cultivation, the release rate of CO₂ was highest in each treatment. After 14 d of cultivation, the release rate of CO₂ in each treatment gradually decreased at a steady state. The order of the release rate of CO₂ during the culturing period was TM > SM3 > SM2 > SM1 > TS. The cumulative release of CO₂ showed a rapid growth in the early and slowed growth in the late periods. Mineralization intensity of soil organic carbon was very small after 35 d of cultivation and most of the organic carbon was fixed in the soil. In all the treatments, TM showed the lowest organic carbon mineralization intensity, indicating that SMS was beneficial for soil carbon sequestration.

Evaluation of energy-oriented utilization potential of main Chinese crop residues based on soil protection functions

ZHU Kaiwei, LIU Zhen, OU Xunmin, HE Liangping, LIN Jinchai

2017, 25(2): 276-286. doi: 10.13930/j.cnki.cjea.160671

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Abstract:
The return of crop residue to soils can prevent soil and water erosion, maintain soil organic matter and plant nutrient balance, etc. Meanwhile, the utilization of crop residue energy can relieve energy stress and improve energy structure in China. Therefore, it is important for the development of ecological agriculture and the sustainable use of agricultural biomass to evaluate ecological potential of crop residues in terms of energy utilization and protection of soil functions. To this end, this study first advanced a concept of Ecological Straw Returning Amount with the consideration of soil and water conservation, soil organic matter maintaining and crop yield increase. Then a scenario analysis method was used to design optimal ecological straw return of different crops. Three scenarios (low, medium and high return) were designed for each crop residue return. The ecological potential of straw energy use was not only affected by ecological straw return, but influenced by crop planting area, per-unit crop yield, crop planting structure and other crop residue uses such as industrial and agricultural uses. Therefore a bottom up dynamic analysis model that was coupled with Gray Neural Network and linear regression analysis was built to calculate ecological potential of straw energy utilization in different regions of China. Ecological potential of energy-oriented utilization of crop residues of different regions was evaluated from three aspects-spatial distribution, resource density and residual resource components. Then based on the direct straw-fired power generation and cellulosic ethanol project, some recommendations were put forward for the development of crop residue energy utilization. The study revealed that:1) In low, medium and high scenario conditions, ecological potentials of straw in terms of energy utilization were respectively 2.28×108 tons, 1.37×108 tons and 7.76×107 tons, with crop residual densities of 172 t·km^-2, 103 t·km^-2 and 58 t·km^-2. Available ecological straw resource for the production of bio-energy comprised mainly of paddy straw, potato straw and wheat straw under low and medium scenario conditions, and mainly of potato straw and sugar straw under high scenario condition. The resource was mainly distributed in Henan, Shandong, Heilongjiang and Sichuan Provinces under the three scenario conditions. 2) Under low scenario condition, residue resource density and total amount of straw in the provinces in mainland China (with the exception of Beijing, Tianjin, Shanghai and Tibet) met the requirement for 6 MW direct straw-fired power generation that was the equivalent of an annual output of 10 000 tons of cellulosic ethanol. Under the medium scenario, only the crop straw resources of Fujian, Guangdong, Guangxi, Hainan and Chongqing were suitable for an annual output of 50 000 tons of cellulosic ethanol. A 25 MW direct straw-fired power generation or an annual output of 50 000 tons of cellulosic ethanol was possible for Fujian, Guangdong, Guangxi, Hainan and Chongqing under the high scenario condition.

Content and bioavailability factors of soil heavy metals in mudflat coastal areas

YAO Rongjiang, YANG Jinsong, XIE Wenping, CHEN Qiang, WU Danhua, BAI Yanchao

2017, 25(2): 287-298. doi: 10.13930/j.cnki.cjea.160407

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Abstract:
The coastal zones with tidal mudflats have the most development potential for agriculture and industry in China. It is therefore vital to study the spatial patterns of soil heavy metals and to identify the intrinsic relationship between the spatial patterns of soil heavy metals and the natural and human driving factors in coastal regions. Using classical statistical and geostatistical methods, this study investigated the effect of land use types on the contents of total and bioavailable heavy metals (Pb, Cr, Cd and As) in surface soil not only to delineate the spatial distribution of these forms of soil heavy metals, but also to determine the relationship between contents of bioavailable heavy metals and basic soil physical and chemical properties. The study was conducted in a coastal area in Jiangsu Province in China-a rapidly developing industrial and agricultural region. Results indicated that soil environmental quality across the study area was generally good. The contents of soil Pb, Cr, Cd and As were lower than the accepted environmental quality evaluation standard (the first class), although there was an increasing trend of accumulation of each heavy metal in recent years. Also environmental risk and ecological toxicity of soil bioavailable Pb, Cr, Cd and As in the study area was not significant. Land use type affected total contents and bioavailable contents of Pb, Cr and Cd to different degrees. Greenhouse facility soils and greenery park soils had the highest contents of total and bioavailable Pb. Also soil contents of total and bioavailable Cr were high in residential and industrial areas, whereas greenhouse facility soils had the lowest total and bioavailable Cd contents. Land use patterns had little impact on total and bioavailable contents of As. In addition to land use type, biological absorption was another important factor affecting the contents of soil heavy metals in the study area. Total soil Pb, Cr and Cd and bioavailable Pb and Cr had significant directional trend across the study area. Spatial pattern of the contents of total and bioavailable soil heavy metals was generally influenced by various factors at different scales. The whole spatial distribution of soil heavy metal was a strip-like pattern due to large-scale tidal deposits. Patched local distributions were mostly controlled by small-range factors such as industrial emissions and human activity. Soil bioavailable Pb, Cr and Cd exhibited significant negative correlation with soil clay particle content, cation exchange capacity and pH. Because of the high content of fulvic acid of soil, a positive correlation existed between bioavailable soil Pb, Cr and Cd contents and soil organic matter content. Sol bioavailable As content was positively correlated with soil pH, but there was no significant correlation between soil bioavailable As and other soil physical and chemical properties. The correlation between bioavailability of soil heavy metals and soil basic physico-chemical properties was critical for developing appropriate management practices that control heavy metal pollution in coastal mudflat regions. The findings of this research provided additional scientific basis for source reduction, ecological activity passivation, pollution abatement and risk prevention of soil heavy metals in mudflat coastal areas.

Simulation and comparative analysis of surface temperature over Inner Mongolia using four NCAR Community Land Models

ZHANG Chao, SONG Haiqing, WU Guozhou, LI Yunpeng

2017, 25(2): 299-308. doi: 10.13930/j.cnki.cjea.160680

Abstract(1197) HTML (20) PDF(1310)

Abstract:
Surface temperature is an important geophysical parameter in energy and substance exchange processes of land-atmosphere interactions, and is a crucial element of global climate system. Time series of observed surface temperature data from meteorological stations are discrete and lack continuity in space. Satellite retrieval of land surface temperature is continuous in space, but with short time series. The simulation of surface temperatures using land surface models is an effective way of obtaining surface temperature data of high temporal resolutions. However, significant differences have been noted between different versions of land surface models, a large part of which lies in the physical processes of key land surface parameters. Thus a comparative evaluation of the performance of surface temperature for 1981-2004 was conducted over Inner Mongolia in this paper using NCAR (National Center for Atmospheric Research) Land Surface Models (CLM3.0, CLM3.5, CLM4.0 and CLM4.5) forced by NCEP (National Center for Environmental Prediction) and ground observation data. The study compared and analyzed differences in the results between models, tested the capability of models to simulate surface temperature over Inner Mongolia and provided guidance and reference for future improvements in the models. The results of the analysis of temporal and spatial variations in surface temperature over Inner Mongolia showed that:NCAR/CLMs simulations could be used to reproduce spatial and temporal variations that were in good agreement with data observed in ground stations. CLM4.5 model was the best as it had the highest correlation coefficient and lowest average deviation and RMS error for the Inner Mongolia due mainly to improvements in the calculation of roughness in the model. The simulation results for surface temperature by different CLM models were generally lower than the observed values. The mean deviation between the CLM simulated results and the ground observations was minimum during winter. Summer bias increased, especially for the eastern region. The deviation in temperature for the eastern part during summer was above 3℃. This indicated that the simulation capability of maximum surface temperature for the eastern and central regions was significantly lower than that for the western region. The differences between various versions of the model for the western region were not as obvious as those for the eastern and central regions. This was related to the improvements in snow patterns and hydrological processes of CLM4.0 and CLM4.5 model versions. In summary, CLM4.0 and CLM4.5 versions were fully applicable in Inner Mongolia, but the simulated values of surface temperature were lower than the measured ones. While the deviations were small in winter and high in summer, the in the eastern region were greater than those in the central and western regions.

2017 Vol. 25, No. 2