中国生态农业学报(中英文)

Effects of nitrogen application and nitrification inhibitor addition on N₂O emissions in Medicago sativa L. grassland

NI Hong, YANG Xianlong, WANG Gang, LAI Xingfa, DENG Jianqiang, SHEN Yuying

2020, 28(3): 317-327. doi: 10.13930/j.cnki.cjea.190511

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Abstract:
Nitrous oxide (N₂O) is undoubtedly one of important greenhouse gases in the atmosphere, which can destroy the ozone layer and aggravate global warming. Agricultural activities, such as fertilizer application, crop straw returning, and biological nitrogen fixation, are the main sources of globally increasing N₂O. Therefore, the study of N₂O emission characteristics and its impact is of great significance for control and mitigation of environmental pollution. This study investigated the N₂O release flux of alfalfa grassland as influenced by nitrogen application and nitrification inhibitor addition, using the static chamber method in Longdong District. The treatments included nitrogen applications of 0 (N0), 50 (N50), 100 (N100), and 150 (N150) kg(N)·hm^-2; and nitrification inhibitor (dicyanogen, DCD) addition (N150+DCD). The static chambers were mounted for the estimation of N₂O emissions from the enclosed alfalfa chambers for two hours daily, and the radiation, air temperature, soil temperature, and moisture were investigated simultaneously. The results showed that the average N₂O emission rates were 3.5, 4.1, 5.0, and 6.1 μg·m^-2·h^-1 for N0, N50, N100, and N150 during the growing season, respectively. The N₂O emission flux was significantly higher in N150 than that in other treatments (P < 0.05). Meanwhile, an increasing trend in the N₂O emission rate was observed with the increasing nitrogen application gradient. Compared to the N150 treatment, the average N₂O emission rate in the N150+DCD treatment decreased by 50.7%, and the cumulative N₂O emissions significantly decreased by 61.6% (P < 0.05), indicating that the addition of a nitrification inhibitor had a significant inhibitory effect on the N₂O emissions. Moreover, the addition of a soil nitrification inhibitor reduced the accumulation of NO₃^--N in the 0-40 cm soil layer and inhibited nitrification in the soil. The dry matter yield of alfalfa per cutting was not influenced by nitrogen application, as there were no significant differences between the N0 treatment and nitrogen application treatments (P>0.05). The N₂O emissions per unit alfalfa yield were 6.5, 7.8, 11.3, and 12.5 mg·kg^-1 for the N0, N50, N100, and N150 treatments, respectively. Therefore, the N₂O emissions increased with the increasing nitrogen fertilizer application rates. It was also discovered that the N₂O emissions were deeply affected by the soil moisture content. During the growing season, the N₂O emission flux had a significant positive correlation with the soil moisture (P < 0.05), but no correlation with the soil temperature. Therefore, it could be concluded that nitrogen application can significantly stimulate N₂O emissions in alfalfa grassland, which is the main reason for the highest N₂O emissions being experienced during the alfalfa growing season. In addition, nitrogen application also had an impact on the N₂O emissions per unit yield of alfalfa. The application of nitrogen together with a nitrification inhibitor can effectively reduce the N₂O emissions caused by fertilization. While temperature may not influence N₂O emissions, precipitation can stimulate N₂O emissions during the growing season. These findings will help to provide a theoretical basis for greenhouse gas emission reduction and reduce the uncertainty concerning climate change prediction in the study area.

Effects and eco-economic thresholds of Leptochloa chinensis and Cyperus difformis on the yield of direct-seeding rice

TIAN Zhihui, LU Junyao, YUAN Guohui, SHEN Guohui

2020, 28(3): 328-336. doi: 10.13930/j.cnki.cjea.190755

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Abstract:
The weeds in rice fields are an important factor affecting rice production. It is important for agricultural development to emphasize both the economic and ecological benefits of rice field weed control. The scientific control of weeds in rice fields according to an eco-economic threshold is an effective way to ensure rice production and protect the environment. Leptochloa chinensis and Cyperus difformis are malignant weeds in rice fields and a significant threat to rice production. To determine the effects and eco-economic thresholds of L. chinensis and C. difformis on the yield of direct-seeded rice, field experiments were performed with 13 mixed densities and 6 coexistence periods with rice of L. chinensis and C. difformis. The results showed that the rice yield traits, such as the number of effective spikes, filled grains per panicle, 1000-grain weight, and rice yield, decreased with the increasing density and coexistence period with rice of L. chinensis and C. difformis. The rice yield loss rate was positively correlated with the mixed density and coexistence period of the two weeds, and there were significant differences among the treatments with different mixed weed densities and coexistence periods. When the density of L. chinensis + C. difformis was 8 + 8 plants per m², the rice yield was 2 236.37 kg·hm^-2 and the rice yield loss rate was 71.14%. At the average density of 4.67 plants per m² for L. chinensis and 3.50 plants per m²for C. difformis, when the coexistence period corresponded with the whole rice growth period, the rice yield was 5 138.33 kg·hm^-2 and the yield loss rate was 33.37%. Weeds at a low density or with a short coexistence period with rice had no significant effect on the rice yield. When L. chinensis and C. difformis coexisted with rice during the whole growth period, the threshold for the composit density of the two weeds was 4.14 plants per m². In addition, under the density conditions of the experiment, when the two weeds grew in a rice field for 16.7 days, the weeding should be conducted. In this study, the idea of controlling the weeds when the damage of L. chinensis and C. difformis reached the eco-economic threshold changed the traditional concept of weed control, and was conducive to reducing the applying times of herbicides, thus decreasing the herbicide application rate.

Prediction of high temperature disaster risks during summer maize flowering under future climate warming background in Henan Province

CHEN Huailiang, LI Shuyan

2020, 28(3): 337-348. doi: 10.13930/j.cnki.cjea.190723

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To predict the risk of high temperature disasters during the summer maize flowering period under future climate change scenarios, a high temperature risk index was established based on the long-term observational data of the summer maize booting period from 19 agro-meteorological observational stations in Henan Province and future climate change scenarios (representative concentration pathways, RCPs). Based on the high temperature risk index, the spatio-temporal characteristics and risk of high temperature disasters during the summer maize flowering period were analyzed in Henan Province. The climate change scenarios (RCPs) included the baseline climate scenario (RCP-rf, 1951-2005) and two future climate change scenarios with moderate emission (RCP 4.5) and high emission (RCP 8.5) during 2006-2050. The summer maize flowering period at each site was defined as the period from the booting stage to 7 days after booting, and then, it was interpolated into the whole province to match the gridded date of climate scenarios. The maximum temperature of higher than 32℃ and 35℃ during flowering were used as the threshold for occurrence of light and heavy high temperature disasters. A comprehensive risk index was successfully established, and the risk level was divided by integrating high temperature frequency and accumulation of temperature higher than 32℃ and 35℃ during the summer maize flowering period. The results showed that under the RCP-rf scenario, the high temperature frequency during the summer maize flowering period was 20.5%-81.0% (≥ 32℃) and 3.9%-51.9% (≥ 35℃). Compared with the baseline, the frequency of high temperature days of more than 32℃ during the summer maize flowering period increased by 9.1% (RCP 4.5) and 11.0% (RCP 8.5), and that of higher than 35℃ increased by 8.7% (RCP 4.5) and 8.3% (RCP 8.5). Under the RCP-rf scenario, the accumulation of temperature higher than 32℃ during the summer maize flowering period ranged 48.5-200.9℃·d, and that of higher than 35℃ ranged 9.8-138.5℃·d. Compared with the baseline, the accumulation of temperature higher than 32℃ during the summer maize flowering period increased by 25.4℃·d (RCP 4.5) and 25.6℃·d (RCP 8.5); and that of higher than 35℃ increased by 25.8℃·d (RCP 4.5) and 31.4℃·d (RCP 8.5). According to the comprehensive risk analysis of high temperature during the summer maize flowering period, the high-risk zones under RCP-rf scenario were distributed in the eastern and northern areas, which adjacent to Xinxiang, Zhengzhou, Xuchang, Luohe, and Zhoukou, except Shangqiu, accounting for approximately 30.1% of the main summer maize planting area. The high-risk areas covered most of the areas in the east of Luoyang and Nanyang, accounting for 63.4% of the main area of summer maize planting under the RCP 4.5 scenario and 76.3% of the main area of summer maize planting under the RCP 8.5 scenario.

Effects of the partial replacement of chemical fertilizer with manure on the yield and nitrogen emissions in leafy vegetable production

WU Xingkui, JIANG Zhencui, LU Zhixin, LU Guang, XU Yonghui, SHI Weiming, MIN Ju

2020, 28(3): 349-356. doi: 10.13930/j.cnki.cjea.190761

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Vegetables are the second largest crop in China, with leafy vegetables accounting for a large proportion, for which the yield is increasingly dependent on large inputs of chemical fertilizer, especially nitrogen. However, there are problems concerning the high application rate of chemical fertilizers and low nitrogen use efficiency of leafy vegetable production. Continuously high inputs of chemical nitrogen fertilizer can easily lead to soil quality degradation, environmental pollution, and other problems, which seriously restrict the sustainable development of vegetable production. The partial replacement of chemical fertilizer with manure could potentially increase efficiency and reduce emissions. To illuminate the best ratio for the nitrogen replacement of chemical fertilizer by manure, and to evaluate the economic benefits and environmental effects of leafy vegetable production, field experiments were conducted. To study the effects of the partial replacement of chemical fertilizer with manure on the yield, economic benefits, ammonia volatilization, and nitrous oxide emissions of Brassica oleracea and Brassica chinensis production; 5 treatments were used:pure fertilizer (0M), and chemical fertilizers replaced with 25%, 50%, 75%, and 100% organic fertilizers (25%M, 50%M, 75%M, and 100%M, respectively). The results showed that among the different treatments, the yield of B. oleracea and B. chinensis were both highest under the 25%M treatment. Compared with the 0M treatment, the yield of B. oleracea and B. chinensis significantly increased by 15.0% and 16.3%, respectively (P < 0.05). During the B. oleracea and B. chinensis seasons, compared with the 0M treatment, the 25%M treatment increased the economic benefit by 11.7% and 5.4%, respectively. However, the economic benefit was negative under the 50%M, 75%M, and 100%M treatments. Under the 25%M treatment, the cumulative ammonia volatilization emissions were 42.1 and 12.9 kg·hm^-2 during the B. oleracea and B. chinensis seasons, which were 23.4% and 41.6% lower than that of the 0M treatment, respectively (P < 0.05). There were no significant differences between the 0M and 25%M treatments concerning the cumulative nitrous oxide emissions. Under the 25%M treatment, the cumulative nitrous oxide emissions were 0.74 and 3.06 kg·hm^-2 during the B. oleracea and B. chinensis seasons, respectively. Compared with the 25%M treatment, the nitrous oxide emissions increased by 33.7%-60.8%, 50.0%-134.3%, and 56.8%-185.6% in the 50%M, 75%M, and 100%M treatments, respectively. Based on this, it is proposed that for leafy vegetable production the appropriate replacement ratio of chemical nitrogen fertilizer by manure is approximately 25%, which can achieve the greatest efficiency increase and emission reduction.

Effect of mycorrhizal fungal inoculation on the growth and phosphorus uptake by soybean genotypes with different phosphorus use efficiency

GU Xiaoting, QIN Jinzhuan, WANG Xiurong

2020, 28(3): 357-364. doi: 10.13930/j.cnki.cjea.190667

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Inoculation of arbuscular mycorrhizal fungi (AMF) can significantly promote soybean growth and phosphorus (P) uptake. However, information about the growth response of soybean genotypes with different P use efficiency to AMF inoculation is limited. In order to explore the effects of AMF inoculation on the growth and phosphate transporter gene expression in different soybean genotypes, a pot experiment was conducted to analyze plant dry weight, mycorrhizal infection characteristics, nitrogen and P contents, root traits, and mycorrhizal inducible phosphate transporter gene expression using P-efficient soybean BX10 and P-inefficient soybean BD2 under mycorrhizal (AM) and non-mycorrhizal (NM) inoculation treatments. The results showed that AMF inoculation significantly increased P uptake in the two soybean genotypes, and there were significant genotypic differences in mycorrhizal effects. Mycorrhizal inoculation significantly increased the shoot dry weight, P content, and total P uptake in BD2, but only significantly increased shoot P content and total P uptake in BX10. BD2 showed higher shoot P content than BX10 irrespective of the inoculation treatments, indicating that a high content of P was translocated from the roots to shoots in P-inefficient BD2. There was no significant difference in root traits between the two soybean genotypes under the NM treatment. However, BX10 showed higher root volume and average diameter than BD2 in the AM treatments. BD2 presented higher mycorrhizal dependence, mycorrhizal growth response, and mycorrhizal P response than BX10. Additionally, the expression of phosphate transporter genes GmPT8, GmPT9, and GmPT10, which indicate mycorrhizal P uptake pathway, was significantly higher in the mycorrhizal roots of BD2 than those of BX10, and consequently, total P uptake of BD2 was higher than that of BX10. The results indicate that mycorrhizal inoculation has greater effects on the growth and P uptake of BD2 than BX10, which can be attributed to the higher P uptake via the mycorrhizal pathway and higher P translocation efficiency of BD2 plants. The results provide a theoretical basis for studying the contribution of mycorrhizal inoculation to P uptake.

Nitrogen fertilizer efficiency and high-yield limiting factors of summer maize in the southern Hebei Province

ZHAO Xiangyang, CONG Jiahui, AN Zhichao, CHEN Mingyou, GUO Xiaowei, ZHAO Ling, CUI Zhenling

2020, 28(3): 365-374. doi: 10.13930/j.cnki.cjea.190694

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The output of summer maize from the Huanghuaihai region accounts for approximately 35% of the national maize output, and so increasing the summer maize output of this region is of great significance to China's food security. The formation of summer maize yield is affected by many factors, such as climate, cultivation, fertilization, and so on. To find the yield variation characteristics, improve the nitrogen fertilizer efficiency, understand the different yield responses to soil nutrients and management measures, and propose a scientific optimization plan, this study used the example of Quzhou County of Hebei Province to investigate nitrogen fertilizer efficiency and high-yield limiting factors of summer maize. The management and soil nutrients of farmer's fields were tracked in real time for 4 consecutive years, and the yield variation characteristics and nitrogen fertilizer efficiency were studied at the farm scale. Meanwhile, the management measures and soil nutrients were analyzed using the boundary line analysis method, to identify the main factors that limit high yields in the region. The results showed that the average summer maize yield for farmers during 2015-2018 was 10.26 t·hm^-2, the coefficient of variation was 15.64%, and the yield and nitrogen fertilizer efficiency fluctuated between years. From 2015 to 2018, the total yield gap was 4.02 t·hm^-2, which varied from 1.96 to 3.68 t·hm^-2 between years. Eliminating the yield gap could achieve a yield increase of 16.46%-34.72%. Over 4 years, the occurrences of farmers obtaining a high yield or nitrogen fertilizer efficiency was normally distributed. The proportions of obtaining one high yield and one high nitrogen fertilizer efficiency were the largest. The yield and nitrogen fertilizer efficiency of a farmer were in an unstable state over the years. The stable-high-yield farmers had significant differences concerning the number of productive ears, 1000-grain weight, sowing date, and density compared with the stable-low-yield farmers (P < 0.05). This study showed that, in this region, the optimal sowing date was June 9-14, the optimal harvest density was 56 000-59 000 plants·hm^-2, the optimal N application rate was 210-230 kg·hm^-2, the optimal P₂O₅ application rate was 45-65 kg·hm^-2, the optimal K₂O application rate was 50-60 kg·hm^-2, and the optimal N-bass application ratio was 0.7-0.8. The formation of the yield gap was caused by various factors, and the contribution of different factors to the yield gap was different in different years. Generally speaking, the density, soil organic matter, and sowing date were the main factors that influenced the yield gap. Increasing regional yields, shrinking yield gaps between farmers, and increasing nitrogen fertilizer efficiency, as well as the shift from low-yield farmers to stable-high-yield farmers, all require improvements in soil nutrients and the optimization of comprehensive management measures.

Effect of sowing date, planting density, and nitrogen application on dry matter accumulation, transfer, distribution, and yield of wheat

MA Shangyu, WANG Yanyan, LIU Yanan, YAO Kejun, HUANG Zhenglai, ZHANG Wenjing, FAN Yonghui, MA Yuanshan

2020, 28(3): 375-385. doi: 10.13930/j.cnki.cjea.190691

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To clarify the regulation mechanism of sowing date, planting density, and nitrogen application on yield, a three-factor fracture zone-test design was adopted. The sowing dates were October 12 and November 12 (represented as ST and LT, respectively); the planting densities were 2.25×10⁶ plants·hm^-2, 3.00×10⁶ plants·hm^-2, and 3.75×10⁶ plants·hm^-2 (represented as M1, M2, and M3, respectively); and nitrogen fertilizers were applied at three rates to each planting density (pure N 150 kg·hm^-2, 225 kg·hm^-2, and 300 kg·hm^-2, represented as N1, N2, and N3, respectively). The effects of different sowing dates, planting densities, and nitrogen application rates on dry matter accumulation, transfer and yield of 'Annongda 1216' were studied. The interaction of sowing date, planting density, and nitrogen application rate significantly affected yield and its components, nitrogen use efficiency, dry matter accumulation, dry matter transfer before anthesis, dry matter accumulation after anthesis, and dry matter distribution at maturity. Under the ST condition, the dry matter accumulation amount at anthesis and maturity, dry matter accumulation amount after anthesis and its contribution to grain, spike number, kernel number per spike, 1000-grain weight, and yield were significantly higher than those under LT condition. Under the ST and LT conditions, the spike number, dry matter accumulation amount at anthesis and maturity under the M2 and M3 treatments were significantly higher than those under the M1 treatment. On the other hand, the grain number per spike, dry matter accumulation amount after anthesis and its contribution to grain, grain weight and its proportion under the M2 treatment were significantly higher than those under the M1 and M3 treatments. The spike number, dry matter accumulation amount at anthesis and maturity, dry matter accumulation amount after anthesis and its contribution to grain under the N3 treatment were significantly higher than those under the N1 and N2 treatments. The grain number per spike, 1000-grain weight, grain weight and its proportion at maturity stage in the M1 and M2 treatments under the ST condition and all planting density treatments under LT condition were significantly higher than those under the N1 and N2 treatments. Under the conditions of this experiment, applying nitrogen fertilizer and increasing planting densities appropriately were beneficial to increase grain yield. 'Annongda 1216' sown on October 12 at a density of 3.00×10⁶ plants·hm^-2 with a nitrogen application rate of 300 kg·hm^-2 showed a higher yield.

Effects of the sowing dates on the nutritional and edible quality of sorghum

ZHANG Ruidong, ZHANG Zhuang, YUE Zhongxiao, LI Jiaheng, CHEN Xiaofei, XU Xiaoxue, XING Yifan, JIANG Bing, ZHOU Yufei, HUANG Ruidong

2020, 28(3): 386-394. doi: 10.13930/j.cnki.cjea.190664

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To determine the suitable sowing date of sorghum and realize high quality and efficient production, three sowing dates of April 30 (T1), May 14 (T2), and May 28 (T3) during 2013-2014 were set with sorghum 'Liaoza 11' and 'Shenza 5' as the experimental materials. After harvest, the yield and nutritional contents of crude protein, tannin, crude fat, amylose, and amylopectin in the grains were measured. The viscosity of sorghum starch was measured using a Rapid Visco Analyzer (RVA), and the edible qualities were evaluated. Meanwhile, the effects of meteorological factors on the nutrition and edible quality of sorghum were analyzed. The results showed that a delay in the sowing date could significantly increase the yield of 'Shenza 5' but had no significant effect on 'Liaoza 11'. With the delayed sowing dates, the contents of crude protein and tannin in the grain decreased, while the contents of amylose, amylopectin and total starch increased. The delay in the sowing date also increased the peak viscosity, break down viscosity, final viscosity, and expansion rate of sorghum starch. As a result, the taste scores of the two sorghum hybrids increased with the delayed sowing dates. Compared with that of T1 and T2, the taste score of 'Liaoza 11' in T3 increased by 11.86%-12.81% and 6.83%-8.44%, respectively. Compared with that of T1 and T2, the taste score of 'Shenza 5' in T3 increased by 6.48%-7.18% and 3.33%-4.06%, respectively. The contents of crude protein and tannin were negatively correlated with the eating quality (except for the texture of cold porridge), and the contents of crude fat, amylose, amylopectin, and total starch were significantly or very significantly positively correlated with the edible quality. The peak viscosity, hot pulp viscosity, break down value, final viscosity, and consistence viscosity were significantly or very significantly positively correlated with the palatability, taste, and smell. We can conclude that a late sowing date (May 28 in Shenyang) can reduce the contents of crude protein and tannin of sorghum, and increase the contents of amylopectin, which led to an increase in the peak viscosity and beak down value of sorghum, resulting in an improvement in the edible quality.

Agronomic traits and cluster analysis of winter wheat varieties (lines) in the Huanghuai and the middle/lower reaches of the Yangtze River wheat areas

WANG Yafei, LI Shijing, XU Ping, ZHANG Zhengbin, JING Ruilian

2020, 28(3): 395-404. doi: 10.13930/j.cnki.cjea.190383

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Climate warming is having a great impact on wheat breeding and production in China and worldwide. To study the regulation mechanisms of the agronomic characteristics of wheat varieties (lines) adapting to climate change in different ecological wheat areas in China, this study selected 20 materials of wheat from the north and south of the Huanghuai winter wheat areas and the middle and lower reaches of the Yangtze River winter wheat area, including good varieties with currently large distributions, new approved varieties, and new breeding lines. The experiment was conducted in Shijiazhuang City of Hebei Province, which is located to the north of the Huanghuai winter wheat area. The drought and cold resistance, root-shoot ratio, and dry leaf weight ratio were investigated before the reviving stage. After harvest, the yield and ten agronomic characteristics, including plant height, spike length, internode length under the spike, tillers number, spikelets number, grains number per spike, 1000-grain weight, biomass per plant, grains weight per plant, and economic index were tested, after which correlation, clustering, and principal component analyses were carried out. The results showed that the drought and cold resistance of different wheat varieties (lines) at the seedling stage was in the order of the north of Huanghuai winter wheat area > the south of Huanghuai winter wheat area > the middle and lower reaches of the Yangtze River winter wheat area. There were extremely significant positive correlations between grains weight per plant and tillers number, grains number per spike, biomass per plant, and economic index in three ecological wheat areas. There were more agronomic characteristics with significant and extremely significant positive correlations in the south of the Huanghuai winter wheat area and the middle and lower reaches of the Yangtze River winter wheat area, indicating that the varieties from these two ecological wheat areas had great similarities. However, there were some differences in the positive and negative correlations among other agronomic traits in different ecology wheat areas. The 20 wheat varieties (lines) were divided into two ecotypes at a Euclidean distance of 20. Varieties (lines) from the middle and lower reaches of the Yangtze River winter wheat area and the south of the Huanghuai winter wheat area were in the type Ⅰ, and those from the north of the Huanghuai winter wheat area in the type Ⅱ. The type Ⅰ was further divided into three sub-classes at a Euclidean distance of 6, which were represented by 'Bainong 207' 'Jimai 22' and 'Xinong 979', respectively. The type Ⅱ was represented by 'Changhan 58'. There were four principal components, yield, spike length, plant height, and economic index, which contributed to over 76.39% of the performance variation of the ten agronomic traits. 'Jimai 22' and other varieties (lines) from the north of the Huanghuai winter wheat area accounted for 95% of the varieties (lines) whose comprehensive scores were ranked in the top 20 varieties (lines). These results provide important reference information for wheat breeding and adaptions to climate warming.

Effects of organic fertilization and tillage method on soil aggregates and organic carbon fractions in a wheat-rice system

ZHANG Zhiyi, XIONG Guiyun, WU Maoqian, FAN Xianpeng, FENG Tingting, BA Ruixian, DUAN Shenrong

2020, 28(3): 405-412. doi: 10.13930/j.cnki.cjea.190617

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In order to clarify the effect of different exogenous organic materials and tillage methods on soil fertility, with the rice and wheat rotation system as the study object, a two-year field experiment was conducted to study the short-term effects of different exogenous organic materials, tillage methods, and their interactions on soil aggregate and organic carbon composition. The results revealed that straw returning with rotary tillage method could decrease soil bulk density and increase total porosity. Compared with non-straw-returning treatment (CKR), the >0.05-mm water-stable aggregate content with straw-returning treatment under rotary tillage (SR) significantly increased (7.2%) in the wheat growing season. In addition, exogenous organic matter and tillage methods had significant effects on soil active organic carbon. Among them, easily oxidized organic carbon (EOC) was significantly affected by the interaction of exogenous organic materials and tillage method, and the acid-hydrolyzed organic carbon (LPI_c and LPII_c) was significantly affected by the tillage method. Compared with CKR treatment, the concentration of EOC and LPI_c with straw-returning treatment under rotary tillage increased by 0.3-2.6 g·kg^-1. The content of particulate organic carbon (POC) was significantly affected by exogenous organic materials, and the average POC content with straw-returning treatments was higher than that with organic fertilizer application treatments (increased by 0.75 g·kg^-1). In the short term, exogenous organic materials, tillage methods, and their interactions had negligible effect on the stability of organic carbon (black carbon and mineral-bonded organic carbon). In conclusion, straw returning combined with rotary tillage could improve the content of soil water-stable aggregates and active organic carbon (EOC, LPI_c, and POC).

Effects of banana stem and its biochar application on soil aggregate characteristics in the Pearl River Delta

HUANG Weihao, QIN Hailong, LU Ying, LI Bo, TANG Xian, WANG Chao, YANG Yang, OU Jinqiong

2020, 28(3): 413-420. doi: 10.13930/j.cnki.cjea.190695

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Here, to investigate the effects of banana stem and its biochar application on soil fertility in the Pearl River Delta, the effects of applying 0.5%, 1.0%, and 2.0% banana stem, rice straw, and their biochar on the composition of soil water-stable aggregates were evaluated in soil culture and pot experiments. The mean weight diameter (MWD), geometric mean diameter (GMD), fractal dimension (D), and mean weight specific surface area (MWSSA) were used to evaluate soil aggregate stability. The results revealed the following:1) Water-stable aggregates in the studied soil was dominated by < 0.25-mm micro-aggregates, followed by 1-0.5-mm aggregates, accounting for 29.80%-47.55% and 18.19%-20.08% of the aggregates, respectively. 2) Applying 1.0% and 2.0% banana stem and 2% rice straw significantly increased >0.25 mm macro-aggregate content and soil aggregate stability. Compared with the control treatment, the soil aggregate MWD increased by 45.60%, 62.37%, and 65.50%, respectively; GMD increased by 43.45%, 55.34%, and 60.66% respectively; D decreased by 2.23%, 2.32%, and 2.78% respectively; and MWSSA decreased by 18.14%, 20.09%, and 23.01% respectively. 3) The MWD and GMD significantly positively correlated with >5 mm, 5-2 mm, and 2-1 mm soil aggregate percentages, and significantly negatively correlated with < 0.25-mm soil micro-aggregate percentage. The D value and MWSSA significantly positively correlated with < 0.25-mm soil micro-aggregate percentage, and significantly negatively correlated with >5 mm, 5-2 mm, and 2-1 mm soil aggregate percentages. 4) The results of principal component analysis and difference significance test indicated that applying 2.0% and 1.0% banana stem had a better effect in improving soil aggregate stability, and this effect was not significantly different from that of 2.0% rice straw application; however, the application of biochar did not increase the stability of aggregates in the short term. This study provides a reference for effectively utilizing banana stem waste and improving soil fertility.

Effects of short distance sampling on the prediction accuracy of the spatial variability of soil respiration

XIE Mengjiao, CHEN Qile, ZHANG Junmei, KANG Ying, WU Chaoyu, LIU Qi, WANG Yang

2020, 28(3): 421-428. doi: 10.13930/j.cnki.cjea.190703

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Sampling design is important for the prediction accuracy of the spatial variability of soil respiration. In this study, a plot of 1 km×1 km was selected in a summer maize field from the northern part of the Huang-Huai-Hai Plain. Each of the forty-nine sampling sites were set on the basis of three different sampling designs, including a regular grid of 7×7 unit rule (with a spacing of 167 m), completely random (with an average spacing of 433 m), and a regular grid of 3×3 unit rule combined with completely random (with an average spacing of 405 m). To optimize the layout, based on the 3 designs, we maintained the total number of samples (49) and replaced the original sampling with short-distance sampling points for 2% to 14% of the total number of samples (with a spacing of 4 m). The spatial interpolation was finished with the ordinary Kriging interpolation method. The root mean square error (RMSE) and determination coefficient (R²) were chosen as indicators to investigate the effects of short distance sampling on the prediction accuracy of the spatial variability of soil respiration. The results showed that the spatial distribution of soil respiration under the three sampling designs was high in the west and low in the east, with moderate variation. Different sampling designs had significant impacts on the prediction accuracy of the spatial variability of soil respiration. The short distance sampling under the three sampling designs increased the prediction accuracy of the spatial variability of soil respiration by 7%-13%. Without short distance samples, the sampling design of the regular grid combined with completely random had the highest prediction accuracy, which was 10% and 22% higher than the regular grid and completely random sampling designs, respectively. Upon the replacement with short distance sampling, the prediction accuracy of the optimal sampling design (regular grid combined with completely random) was increased by 4%-7%. The prediction accuracy of the spatial variability of soil respiration was most obviously improved when the proportion of short distance samples was 10% of the whole size. This study found that setting short distance samples based on the same sample size could increase the sample density within a region and improve the prediction accuracy of soil respiration spatial variation and the reliability of experimental results. Therefore, a completely random sampling design combined with a regular grid and 10% short distance samples is a better choice for the soil respiration spatial variation estimation of a 1 km×1 km plot in a summer maize field from the northern part of the Huang-Huai-Hai Plain. The results of this study provide guidance for relevant research and field sampling designs.

Soil carbon and nitrogen dynamics during vegetation restoration and their responses to extreme water-logging disasters in a typical karst depression

WU Fangji, LIU Na, HU Peilei, WANG Kelin, ZHANG Wei, ZOU Dongsheng

2020, 28(3): 429-437. doi: 10.13930/j.cnki.cjea.190711

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Abstract:
The karst region in Southwest China is one of the most ecologically fragile areas characterized with severe rocky desertification, and increased and frequent flood events. Vegetation restoration has been recognized as an effective strategy for soil carbon and nitrogen accumulation in degraded ecosystems. However, soil carbon and nitrogen dynamics following vegetation restoration have not been evaluated with a long-term, fixed-point research approach in the karst areas. Thus, we compared the effects of vegetation restoration types on soil carbon and nitrogen stocks before (in 2004) and after 10 (in 2014) and 13 years (in 2017) of cropland abandonment. Four restoration strategies were implemented in the present study, namely, restoration with plantation forest, grassland, a combination of plantation forest and grassland, and spontaneous regeneration to a natural grassland. Cropland under maize-soybean rotation (CR) was used as the control. From 2004 to 2014, there were no extreme water-logging disasters, whereas from 2014 to 2017, two extreme water-logging disasters occurred in the study region. The results revealed that soil organic carbon (SOC) stocks in all the four restored vegetation types significantly increased after 10 years of cropland abandonment, whereas after 13 years, the plantation forest, grassland, and the combination of plantation forest and grassland, except the natural grassland, showed a decreasing trend. The increase in the total nitrogen (TN) content of soil in response to vegetation restoration was less than that of SOC; the TN content significantly increased only in the grassland after 10 years of cropland abandonment. The TN content in the combination of plantation forest and grassland and natural grassland increased after 13 years of cropland abandonment, and that in the natural grassland continuously increased after cropland abandonment. The correlation analysis showed that soil exchangeable Ca²⁺ was positively correlated with SOC and TN (P < 0.05). However, the content of soil exchangeable Ca²⁺ significantly decreased in 2017 than in 2014. The reduction in soil exchangeable Ca²⁺ can be attributed to the continuous flood event in the study area in 2015 and 2016. Vegetation restoration can significantly improve soil carbon and nitrogen sequestration in karst areas. Furthermore, when compared with other vegetation restoration types, natural vegetation restoration was more beneficial to soil carbon and nitrogen sequestration, which can resist the negative effects of extreme climate disasters effectively.

Evaluation of winter wheat yield prediction ability of different statistical models—A case study of Jiangsu wheat-growing region

XU Min, XU Jingwei, GAO Ping, SONG Yingbo

2020, 28(3): 438-447. doi: 10.13930/j.cnki.cjea.190814

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Abstract:
We screened for the highest performance model among several winter wheat yield predicting models. The selected model was weighted and integrated in order to improve the accuracy of prediction, as it plays a key role in ensuring food security. Daily meteorological observations, winter wheat yield data, and growth period observations were obtained from 69 basic meteorological stations in Jiangsu Province from 1993 to 2018. Then, five methods of meteorological yield and trend yield separation (linear separation, percentage difference, 5-or 3-year sliding average, and quadratic curve) were compared. On this base, by using the fitting test and hind-casting test, we evaluated and analyzed the simulation effects of yield prediction methods based on similar years with bumper or poor harvest, key meteorological factors and climate suitability, and integrated the methods for Jiangsu winter wheat yield prediction. The results revealed the following:1) For the same yield prediction method, the yield separation methods had a greater effect on prediction accuracy. The quadratic curve method was the best among the linear separation, percentage difference, 5-or 3-year sliding average and quadratic curve methods. The prediction accuracy of the weighting method was higher than the large probability method in the similar years with bumper or poor harvest prediction method. From 1993 to 2013, the average accuracy of the methods of the similar years with bumper or poor harvest prediction, key meteorological factor, and climate suitability were 89.67%, 94.86%, and 94.96%, respectively. 2) The accuracy of the integrated prediction method was more than 96.33% in the past 5 years, and it was higher than that of the similar years with bumper or poor harvest-weighting model, key factor-quadratic curve model and climate suitability-quadratic curve model. This could probably overcome the less stability of prediction accuracy of a single prediction method. 3) The closer the predicted time to the maturity period and the more comprehensive the prediction factor information, the higher the accuracy of the prediction model. These results provide a scientific basis for selecting an optimized prediction model for winter wheat yield in Jiangsu, and the methodology of model screening can also be used in other provinces.

Discussion on the ecological compensation standard of green manure planting based on the willingness of fruit farmers to accept

REN Jing, YIN Changbin, DUAN Zhilong

2020, 28(3): 448-457. doi: 10.13930/j.cnki.cjea.190645

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Abstract:
To explore the reasonable ecological compensation standard of green manure planting for fruit farmers, the theories of utility as guides, relying on 423 green manure planting samples of fruit farmers in Shaanxi Province, and using ecological compensation theory, this paper constructed the utility function of fruit farmers' willingness to accept, and determined the compensation standard for fruit farmers. In addition, using the Binary Logistic regression model, this paper tests the factors affecting the willingness of farmers to accept. The calculation results of the ecological compensation standard for green manure planting showed that the parameter estimation result was 2 611.80 ¥·hm^-2, and the non-parametric estimation result was 3 660.75 ¥·hm^-2, both of which are dynamic adjustment intervals of the ecological compensation standards for green manure planting in orchards in Shaanxi Province. According to the survey results, approximately 77% of fruit growers tended to use green manure in orchards. Fruit growers with different personal characteristics, family characteristics, and cognitive levels would show different levels of willingness to use green manure. The regression analysis showed that for the fruit farmers in Shaanxi, the personal endowment of the fruit farmers and the family production and management characteristics had no significant impacts on the willingness to accept. The villagers suggested that the awareness of green manure and the national green manure industry policy had become the main influencing factors. The planting subsidy in the policy was the fundamental motivation for farmers to plant green manure. Based on the above conclusions, it is suggested that the vigorous implementation of green manure should first respect the willingness of farmers, and secondly, determined appropriate ecological compensation standards, and established a market-based and diversified ecological compensation system that combined control and incentives.

Construction and application of an ecological compensation model based on GIS for cross-basin areas—A case study of the Dabie Mountain areas in Anhui Province

SUN Xianbin, SUN Liangping, WANG Shengtang, LI Guangyao, ZHANG Xin

2020, 28(3): 458-466. doi: 10.13930/j.cnki.cjea.190464

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Abstract:
Marketization and diversified ecological compensation are the supporting policies to improve the main functional zones. In this paper, a standard model of ecological compensation was established using the modified ecological footprint method. And the model of ecological compensation cost distribution among functional areas across river basins was established using the theories of ecological flow and gravitational model theory. An empirical analysis of the Dabie Mountain areas in Anhui Province was carried out using the GIS technology. The results revealed the following:1) According to the ability to pay for development areas and the ecological carrying capacity, combining the value and effect scope of ecosystem services, the ecological compensation standard, and the ecological flow coefficient provided by the protected areas, the ecological compensation model of inter-basin function area were constructed based on the environment conditions in the Dabie Mountain area. Therefore, the ecological compensation model could be scientifically adapted to the real world and could be applied to analyze spatial differentiation and quantify ecological compensation standards in the Dabie Mountain area. 2) In 2015, Jinzhai-Huoshan water source and Yuexi-Taihu-Qianshan water source had the largest ecological radiation area in the urban area of Hefei-Feixi-Feidong development zone (4 521.92 km² and 5 102.92 km², respectively), and the total value of ecological radiation of the two water sources was also the largest (36.178 2 and 38.885 million ¥, respectively). Therefore, the development zone was the main source of ecological compensation costs for the water source area. The Hefei-Feixi-Feidong development zone was close to two major agricultural producing areas, and the area affected by ecological radiation was also the largest; therefore, the value of ecological services was the largest, which was 20.982 3 million ¥ and 27.171 9 million ¥, respectively. 3) The total amount of ecological compensation provided by the four development areas was 142.439 5 million ¥, and the proportion of each area was 78.38% (Hefei Urban Region, Feidong County, and Feixi County), 9.28% (Anqing Urban Region), 9.34% (Huainan Urban Region), and 2.99% (Jin'an Region). The ecological compensation was mainly provided by Hefei City. 4) Jinzhai-Huoshan water source and Yuexi-Taihu-Qianshan water source provided ecological services valued at 57.679 7 million ¥ (accounting for 29.1%) and 58.735 2 million ¥ (accounting for 29.63%), respectively, for the development area. The surrounding main agricultural production areas also provided eco-functional services valued at 81.771 7 million ¥ (accounting for 41.26%). 5) The compensation funds provided for two water source areas were 42.367 5 million ¥ (accounting for 29.74%) and 44.245 4 million ¥ (accounting for 31.04%), respectively, and they were the main areas of compensation. The surrounding main agricultural areas also received a compensation of 55.856 6 million ¥ (accounting for 39.22%). The ecological compensation model and standard provide a scientific reference for environmental protection and construction of main functional areas.

2020 Vol. 28, No. 3