中国生态农业学报(中英文)

Yield and economic benefits of peanut intercropping with maize and sesame

WU Yanyan, WANG Jiangtao, LI Xue, SUN Zengguang, GUO Binbin, YIN Fei, JIAO Nianyuan

2021, 29(8): 1285-1295. doi: 10.13930/j.cnki.cjea.210056

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Abstract:
Peanuts are an important oil crop in China. Intercropping peanuts with maize or sesame improves the field microclimate and the utilization of light and heat resources and increases yield and income. Different high crops in the intercropping systems have different effects on the canopy light intensity, photosynthetic capacity of the functional leaves, dry matter accumulation, and yield of intercropping crops. The purpose of this study was to optimize the peanut intercropping system and to select suitable crops for peanut intercropping. To assess the effects of different intercropping systems on peanut yield and the economic benefits, a field experiment was conducted in 2018 and 2019 with five treatments: maize intercropping with peanut (maize‖peanut, M‖P), sesame intercropping with peanut (sesame‖peanut, S‖P), monocultured peanut (SP), monocultured maize (SM), and monocultured sesame (SS). The different planting patterns were assessed for their effects on the interspecific competition index, dry matter accumulation, photosynthetic rate response curves to light in the functional leaves, yield, and the economic benefits of peanuts. The results showed that: 1) compared with intercropped peanuts in maize‖peanut, the maximum net photosynthetic rate (P_nmax), yield, and maximum dry matter accumulation of intercropped peanuts in sesame‖peanut increased by 18.0%-20.7%, 64.2%-70.0%, and 26.5%-31.8%, respectively. 2) When the dry matter accumulation of intercropped sesame entered the period of 16-19 days after the slow-growing period, the intercropped peanuts in sesame‖peanut were still in the period of rapid dry matter accumulation. The fast growth periods of dry matter accumulation of sesame and peanut in sesame‖peanut intercropping system staggered each other, however, those of maize and peanuts in maize‖peanut intercropping system were overlapped. At the mature stage, the competitiveness index of peanuts against sesame and maize in the intercropping systems was -2.31~-2.06 and -4.68~-4.34, respectively. This indicates that the competitiveness of intercropped peanuts to sesame is stronger than that to maize. 3) The land-equivalent ratio of sesame‖peanut intercropping system increased by 3.0%-4.0% compared with maize‖peanut intercropping system, and those of both systems were greater than 1. The economic benefits of sesame‖peanut intercropping system significantly increased by 16.7%-50.8% compared with maize‖peanut intercropping system, reaching 23 000-24 000 ¥·hm^-2. Compared with maize‖peanut intercropping system, sesame‖peanut intercropping system improved the land utilization rate, yield, and income. Sesame‖peanut intercropping system staggered the rapid growth periods of dry matter accumulation of two crops, reduced the intensity of interspecific competition between high and low crops, and improved the canopy light intensity and net photosynthetic rate of intercropped peanuts.

Effects of time of spring one irrigation on the grain filling characteristics and water use efficiency of winter wheat

LIU Zhiliang, LI Xiaoshuang, CAO Caiyun, ZHENG Chunlian, MA Junyong, LI Kejiang, YANG Huiying, LI Shuning, DANG Hongkai

2021, 29(8): 1296-1304. doi: 10.13930/j.cnki.cjea.201015

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Abstract:
There is a serious contradiction between water resources and grain production in the Hebei Plain; therefore, this study aimed to investigate the optimal time of once irrigation in spring for winter wheat to provide a technical basis for regional food security and groundwater overdraft control. A field positioning experiment was conducted from 2018 to 2020, with the water-saving winter wheat cultivar 'Heng 4399' under five treatments of spring one irrigation time (0 d after jointing, AJ0; 5 d after jointing, AJ5; 10 d after jointing, AJ10; 15 d after jointing, AJ15; and 20 d after jointing, AJ20) and two control treatments (no spring irrigation, CK1; and spring two irrigations, CK2). The effects of different treatments on the grain filling characteristics, yield, and water use efficiency of winter wheat were analyzed. The results showed that the delay of one spring irrigation time increased the duration of grain filling and the theoretical maximum 1000-grain weight, and decreased the average grain filling rate. Compared with AJ0, the duration of grain filling was prolonged by 3-7 d, the average grain filling rate decreased by 2.40%-13.51%, and the theoretical maximum 1000-grain weight increased by 1.61%-18.62% in the other spring one irrigation treatments. Under the spring one irrigation condition, the spike number per unit area, grain number per spike, and grain yield of winter wheat first increased and then decreased with the delay of irrigation date, whereas the 1000-grain weight gradually increased. Grain yield in the AJ5 treatment was the highest, followed by AJ10, and there was no significant difference between AJ5 and AJ10 (P>0.05), but both were significantly higher than those of AJ0, AJ15, and AJ20 (P < 0.05). The yields of AJ5 and AJ10 increased by 96.04% and 52.18% in 2018-2019, and 90.15% and 49.84% in 2019-2020, respectively, compared to CK1. However, compared to CK2, the same treatments decreased by 0.80% and 16.75% in 2018-2019, and 3.79% and 18.03% in 2019-2020, respectively. In the two experimental years, the water use efficiency of spring one irrigation treatments was higher in AJ0, AJ5, and AJ10, and there was no significant difference among the treatments (P>0.05). AJ15 and AJ20 significantly decreased the water use efficiency compared to the above-mentioned treatments (P < 0.05). Compared to CK1 and CK2, the water use efficiency of AJ5 increased by 20.78% and 18.47% (P < 0.05) in 2018-2019, and by 41.07% (P < 0.05) and 5.33% (P>0.05) in 2019-2020, respectively; AJ10 increased by 12.34% and 10.19% (P>0.05) in 2018-2019, and by 37.50% (P < 0.05) and 2.67% (P>0.05) in 2019-2020, respectively. In summary, under spring one irrigation conditions of winter wheat in the experimental area, the optimal irrigation date is 5-10 days after jointing, which resulting in a higher yield and water use efficiency.

Alleviating effect of strong reduction and flooding treatment on continuous cropping obstacles in Rehmannia glutinosa

GU Li, LI Xuanzhen, LI Mingjie, YU Zhijian, LIN Meigui, WANG Jianming, XIE Jiawei, ZHANG Zhongyi

2021, 29(8): 1305-1314. doi: 10.13930/j.cnki.cjea.210114

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Abstract:
Rehmannia glutinosa is a popular medicinal herb in China. During R. glutinosa cultivation, serious consecutive monoculture problems are often encountered and have not yet to be effectively resolved. Preliminary studies found that an imbalance in the microbial communities in the rhizosphere soils is the main reason for consecutive monoculture problems; the abundance of pathogenic microorganisms significantly increased, whereas the beneficial microorganisms were inhibited. Therefore, it is important to control and alleviate the consecutive monoculture problem by inhibiting and balancing pathogenic microbes. This study sought to develop critical technology for alleviating the consecutive monoculture problems of R. glutinosa with strong reducing and flooding measures that may effectively inhibit the proliferation of pathogenic microbes. The key indices of treated R. glutinosa were analyzed, including plant growth and development, the physical and chemical properties of continuous cropping soil, the bacterial community structure, and its biological functions. The results indicated that the strong reducing and flooding treatments significantly increased the relative abundance of anaerobic heterotrophic bacteria, including Ruminococcus and Enterococcus, in the continuous cropping soils. This enhanced soil denitrification, creating special soil environments rich in Fe²⁺ and organic acids that inhibited pathogenic bacteria. Compared with the control soils, in the soils treated with strong reducing, the Fe²⁺ and organic acid levels increased by 4.73 times and 3.54 times, respectively, and in the soils treated with flooding, the same values increased by 1.65-fold and 1.12-fold, respectively. Concurrently, the beneficial bacteria community, such as Pseudomonas, was rapidly rebuilt in the treated soils; these bacteria have important roles that inhibit the proliferation of pathogens. The two methods, reducing and flooding, have different effects on the soil physical and chemical properties and the bacterial community structure of the consecutive cropping soils. Thus, the two methods have different efficiencies for alleviating the consecutive monoculture problem of R. glutinosa. Due to addition of straws, the strong reducing method increased contents of organic matter, available nitrogen, available phosphorus and available potassium of the consecutive cropping soils, while the flooding method did not show these effects. The Shannon index and Chao1 index under flooding decreased, while Shannon index decreased and Chao 1 index increased under the strong reduction. Both methods effectively increased the survival rate and yield of replanted R. glutinosa. The survival rate and yield of continuous cropping R. glutinosa treated with strong reducing increased by 1.94 times and 4.04 times, respectively, compared with those of the control plants. In contrast, the strong reducing treatment has more optimized effects that alleviate the consecutive monoculture problems of R. glutinosa. Both treatments alleviate the consecutive monoculture problem and improve the survival rate and yield of replanted R. glutinosa via improvements in the physical and chemical properties of the continuous cropping soils and their microbial communities. This study provides an important theoretical basis and technical reference for future studies of the strategies used to alleviate the consecutive monoculture problem during R. glutinosa production.

Effects of microbial fertilizer application on the quality and pharmacological activities of radix pseudostellariae under continuous monoculture regimes

WU Hongmiao, ZHANG Shengkai, JIAO Yanyang, LIN Yu, WU Huiming, QIN Xianjin, LIU Yazhou, CHEN Jun, LIN Wenxiong

2021, 29(8): 1315-1326. doi: 10.13930/j.cnki.cjea.200966

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Abstract:
The continuous monoculture problem commonly causes huge economic losses in modern agricultural production. The occurrence and development of continuous cropping obstacles pose a serious threat to the yield and quality of Chinese medicinal plants; therefore, it is important to explore effective strategies to alleviate the continuous cropping obstacles. In this study, we evaluated the effects of microbial fertilizer application on the continuous cropping obstacles and pharmacological activities of radix pseudostellariae (Pseudostellaria heterophylla). The effects of microbial fertilizer application on the yields of continuous monocultured radix pseudostellariae for 4 years under field localization experiments were investigated. Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and high-performance liquid chromatography-mass spectrometry (HPLC-MS) were used to analyze the effects on the rhizosphere soil microorganisms and the main effective components of radix pseudostellariae. We also used pharmacological tests to analyze the efficiency of radix pseudostellariae under different treatments. Our results showed that microbial fertilizer significantly improved the growth of continuous monocultured radix pseudostellariae, and the yield increased by 68.28%, 111.58%, 257.54%, and 133.23% in 4 years, respectively. Microbial fertilizer application significantly increased the abundance of beneficial Pseudomonas spp., decreased pathogenic Fusarium oxysporum in the rhizosphere soil, and increased the contents of total polysaccharides and heterophyllin B in radix pseudostellariae as compared with those of the consecutive monoculture treatments. The types and contents of amino acids in radix pseudostellariae under microbial fertilizer application were similar to those in the 1-year monoculture and standard radix pseudostellariae. Eight types of amino acids in the microbial fertilizer amendment and the newly planted radix pseudostellariae were not significantly different. Pharmacological tests showed that radix pseudostellariae alleviated the damage caused by cyclophosphamide in mice. There were no significant differences in the spleen index, liver weight, epididymal fat weight, and white or red blood cell content of mice treated with plants of the microbial fertilizer amended and newly planted radix pseudostellariae. The effect of radix pseudostellariae on platelet recovery of mice under microbial fertilizer amendment was consistent with that of standard radix pseudostellariae. Moreover, the total antioxidant capacity of radix pseudostellariae under microbial fertilizer amendment was stronger, and the superoxide dismutase content was significantly higher than that of newly planted and standard radix pseudostellariae. Compared with newly planted radix pseudostellariae, the microbial fertilizer amendment significantly increased the expression of immune factors IL-2 and IFN-r in the liver tissue of mice. There was no significant difference in the expression of TNF-α between the microbial fertilizer amendment and newly planted radix pseudostellariae. In conclusion, microbial fertilizer amendment effectively alleviated the continuous cropping obstacle and improved the quality and pharmacological activities of radix pseudostellariae. Our results provide guidance for studying alleviation strategies in other Chinese medicinal plants under consecutive monoculture regimes and for evaluating the quality and pharmacological activities of modified medicinal plants.

Comprehensive evaluation and identification trait selection of drought resistance at the seedling stage of Brassica napus L.

LI Yangyang, LI Chi, REN Junyang, LI Zhi, ZHANG Jinfeng, LYU Rongrong, ZHANG Heng, WU Dan, WANG Qin, ZHOU Qingyuan, YIN Jiaming, LI Jiana, LIU Liezhao, TANG Zhanglin

2021, 29(8): 1327-1338. doi: 10.13930/j.cnki.cjea.200877

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The yield and quality of Brassica napus L. are often affected by drought stress in China. To identify drought-tolerant and drought-sensitive germplasms, screen for indices of drought tolerance to reduce cost and improve efficiency, provide a basis for breeding drought-tolerant varieties, and investigate the mechanisms of drought tolerance, 229 B. napus accessions were subjected to two water treatments (drought stress and well watering) at the seedling stage. The shoot fresh weight, shoot dry weight, root fresh weight, root dry weight, leaf peroxidase activity, malonaldehyde content, proline content, soluble protein content, soluble sugar content, and leaf relative water content were measured. The drought resistance index, clustering analysis, subordinative function, principal component analysis, and gray correlation analysis were used to comprehensively evaluate drought tolerance. The correlation coefficients between the drought resistance index of each trait and the average value of the subordinative function, composite value of the principal component factors, and comprehensive relation degree and those among the drought resistance indexes of the ten traits were calculated to determine the drought tolerance index. The results showed significant differences between the drought-stressed and well-watered plants at the seedling stage. During drought stress, the leaves of drought-stressed plants gradually wilted and curled to different degrees, and the leaves were born slowly and became smaller, while the old leaves turned yellow. After 30 days of stress, the drought-stressed plants were shorter, weaker, and had lower biomass than the well-watered plants. The shoot fresh weight, shoot dry weight, root fresh weight, leaf relative water content and soluble protein content were lower, and the leaf peroxidase activity, malonaldehyde content, proline content, and soluble sugar content increased under drought stress. The root dry weight did not differ between drought stress and well watering. The 229 B. napus accessions were divided into eight groups, and the accessions of each group showed different drought tolerance characteristics. The significant correlation between the average value of the subordinative function, composite value of the principal component factors, and the comprehensive relation degree indicated that the comprehensive evaluation was reliable. Therefore, by means of the subordinative function, principal component analysis, and gray correlation analysis, accessions RR002, 9801C, Yan81-2, 07037, Zheyou758, and 09-P64-1 were identified as drought tolerant. Accessions 11-P30, CY16PXW-35, 08-P35, 09-P36, Jia972, and A148 were drought sensitive. The correlations of shoot fresh weight, shoot dry weight, root fresh weight, root dry weight, leaf proline content, soluble sugar content with the average value of the subordinative function, composite value of the principal component factors, and the comprehensive relation degree were significant with high correlation coefficients, as did those among shoot fresh weight, shoot dry weight, root fresh weight, and root dry weight. The shoot fresh weight, leaf proline content and soluble sugar content can serve as rapid, simple, and accurate traits to identify comprehensive drought tolerance at the seedling stage in B. napus.

Prediction of tea yield and picking date based on the AquaCrop model

MA Yuming, CHEN Jie, JIN Zhifeng, HAO Lu

2021, 29(8): 1339-1349. doi: 10.13930/j.cnki.cjea.210018

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Abstract:
This study aimed to verify the applicability of crop models for the yield and picking data prediction of different tea varieties in Zhejiang Province and to fill the gap in tea simulations of crop models. Three tea varieties ('White Leaf 1' 'Longjing43', and 'Longjingqunti') were selected in the typical tea planting areas of Zhejiang Province (Anji County, Songyang County and Hangzhou City). Based on the AquaCrop model recommendations and the tea plant conservative parameters provided by the Food and Agriculture Organization (FAO), the parameters of the AquaCrop model were obtained from field experiments, data collection, and parameter sensitivity analysis, and the model was localized and corrected using data from previous years. The yield forecast models for Anji and Songyang Counties and prediction models of the spring tea picking data for the three tea varieties were established based on the AquaCrop. The AquaCrop model simulated the average total annual tea output of Songyang County from 2013 to 2017 to be 1.497 t·hm^-2, with a relative error of 1.98%. The average annual output of spring tea in Anji County from 2014 to 2018 was 0.164 t·hm^-2, with a relative error of 0.99%. The normalized root mean square error of the AquaCrop model for tea yield simulation in Songyang and Anji Counties was 2.20% and 1.10%, respectively; and the root mean square error was 0.0325 t·hm^-2and 0.0018 t·hm^-2, respectively; the conformity index was 0.84 and 0.88, respectively. The prediction standard of the tea growing degree-days (GDDs) for 'White Leaf 1' 'Longjing43', and 'Longjingqunti' were determined, and the prediction formulas of the three tea GDDs were obtained via the stepwise regression method. The mean absolute errors (MAE) of AquaCrop model based GDDs prediction of three tea varieties were 1.1 d, 2.1 d, and 1.1 d, respectively. The AquaCrop model based on stepwise regression prediction of the tea picking data was significant (P < 0.01), with the simulated MAEs for three tea varieties were 0.7 d, 0.7 d, and 0.9 d, respectively. The results show that the AquaCrop model has good adaptability to different tea varieties in Zhejiang Province after correction. Localized AquaCrop models can be used to study the water management and yield potential of tea gardens. Both prediction models the AquaCrop model of the tea picking data based on GDDs prediction and stepwise regression prediction have applicable value, and the predictions based on the stepwise regression analysis model is more accurate with higher practical value than the GGDs forecasting model.

Influence of apple grafting combinations on carbon storage in orchards

LYU Jiahong, LI Hui, DENG Mingjiang, CHAI Xiaofen, HAN Zhenhai, WANG Yi

2021, 29(8): 1350-1358. doi: 10.13930/j.cnki.cjea.200770

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Orchard ecosystems are an important form of agriculture that plays a significant role in the carbon sink of terrestrial ecosystems in China. Estimating carbon sequestration and economic value of orchards is a central part of global carbon cycle research. In this study, six orthogonal combinations of three stock species (Malus micromalus, M. baccata, and M. hupehensis) and two scions of apple cultivars ('Fuji' and 'Golden Delicious') were examined for the carbon storage in the vegetation layers, soil, and litter of apple orchard. Carbon storage in the orchard ecosystems was summarized, and the carbon sequestration capacities of different soil-vegetation systems were explored. This work provides a theoretical basis for improving the carbon storage of apple orchards. The results showed that, compared with other tissues, the roots had the highest carbon content, while the trunk biomass was the highest among all organs biomasses, accounting for 33.89% to 47.95% of the total biomass. The carbon storage of each organ was different and in the sequence of trunk > branches > root. Carbon storage in the trunk accounted for more than 38% of the whole plant. When comparing the plant carbon storage of each combination, there were significant differences between scions. When M. baccata and M. hupehensis were used as stocks, the combination with 'Fuji' as the scion was significantly higher than that with 'Golden Delicious'. Comparison of the litter carbon storage in the various stocks and scions showed significant differences between different scions of the same stock; the stock combination with 'Fuji' was significantly higher than the combination with 'Golden Delicious'. Carbon storage in the litter indicated that there were significant differences in carbon storage among stocks. Carbon storage in the litter of combinations with M. baccata as the stock was significantly higher than in the combinations with M. micromalus and M. hupehensis as stocks. However, there were no significant differences between the latter two. Carbon storage in the 0-20 cm soil layer (57.86-80.91 t·hm^-2) was significantly higher than that in the 20-40 cm (20.15-25.97 t·hm^-2), 40-60 cm (11.54-14.62 t·hm^-2), and 60-100 cm (17.41-33.98 t·hm^-2) soil layers. 'Golden Delicious'/M. baccata had the highest carbon storage value per area. Moreover, there was little difference in the economic value of carbon storage in each stock combination, with an average of RMB 170.84 thousand Yuan per hectare.

Correlation between the rhizome expansion ability and endogenous hormones contents of wild Poa pratensis in Gansu Province

YUAN Yajuan, BAI Xiaoming, ZHU Yanan, ZHANG Yujing, YAN Yubang, ZHANG Caizhong, LI Yujie

2021, 29(8): 1359-1369. doi: 10.13930/j.cnki.cjea.200976

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Poa pratensis is a typical rhizome grass, of which rhizome is an important organ for nutrient storage and vegetative reproduction that plays an important role in improving plant surface invasion and underground soil consolidation. The occurrence and development of rhizomes are closely related to endogenous hormones. This study investigated the hormone regulation mechanism of rhizome expansion by examining the correlation between the rhizome expansion ability and endogenous hormones contents in nine ecotypes of wild P. pratensis from different areas of Gansu Province and 'Midnight Ⅱ' P. pratensis (the control). The purpose of this study was to provide a theoretical and practical basis for new variety breeding and lawn maintenance and management of P. pratensis. The results indicated that: 1) there were differences in the rhizome expansion ability among the wild P. pratensis ecotypes. P. pratensis from Yuzhong had the largest tiller number, rhizome number, aboveground biomass, and stem node length, whereas P. pratensis from Xihe had the largest coverage area, longest rhizome, and highest rhizome biomass. The rhizome expansion ability of P. pratensis from strong to weak was P. pratensis from Yuzhong > from Xihe > from 'Midnight Ⅱ' > from Weiyuan > from Lingtai > from Qingshui > from Sunan > from Qinzhou > from Xiahe > from Anding. 2) The distribution of endogenous hormones in the rhizome and stem base of P. pratensis was significantly different; the gibberellic acid (GA₃), indole-3-acetic acid (IAA), and abscisic acid (ABA) contents were rhizome > stem base; the zeatin (ZT) content was stem base > rhizome; and the GA₃ content in the two parts was significantly higher than that of the other hormones. 3) Correlation analysis showed that the rhizome expansion ability of P. pratensis was positively correlated with the ZT content, stem base ZT/ABA, and IAA/ABA (P < 0.05) but negatively correlated with rhizome GA₃/IAA (P < 0.05). However, there were no correlations between the IAA, GA₃, and ABA contents. In summary, P. pratensis from Yuzhong, which has better rhizome expansion ability than 'Midnight Ⅱ', is good for variety breeding; the higher ZT content and ratio of IAA/ABA to ZT/ABA and the lower GA₃/IAA ratio are beneficial to the rhizome expansion.

Optimization of the planting structure in the upstream region of Baiyangdian Lake based on the non-dominated sorting genetic algorithm (NSGA-Ⅱ)

WANG Lu, DU Xiong, WANG Rong, YANG Yanmin, HU Yukun, HOU Zhenjun

2021, 29(8): 1370-1383. doi: 10.13930/j.cnki.cjea.201021

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Reasonable planting structures are the basis of the optimal allocation of regional water and land resources. The upstream region of Baiyangdian Lake suffers from the perils of water shortage and an unreasonable planting structure. On the base of the current status of the main crop planting structure, this study considered the crop planting area as optimization variable, the water resources, land resources, and social needs as the constraints, while seeking to maximize the economic and ecological benefits and to minimize the irrigation water consumption based on the non-dominated sorting genetic algorithm (NSGA-Ⅱ) of the crop planting structure adjustment model. This study also proposed the planting structure optimization schemes under different scenarios of various water restrictions and agricultural mechanization levels in the mountain area and plain area of the upstream of Baiyangdian Lake. The results showed that, at the current status of mechanization level, the area of the rotations of two crops in a year scaled down, while vegetables and mung beans-fresh maize areas increased, the economic benefits should increase 12.6%, and ecological and water-saving benefits decreased under the no-restricted irrigation water; while wheat-maize, mung beans-fresh maize, spring sweet potato, vegetables and fruits areas increased under restricted irrigation water inducing increased economic and water-saving benefits. In the 20% water-saving scenario, almost all crop areas would be scaled down, including vegetables, area of wheat-maize decreased 21.5%, and economic and ecological benefits decreased. In the scenario without water limitation, the optimized economic benefit increased the most, the ecological benefit decrease the least, water consumption increased, and the grain yield decreased the least. However, in the scenario of 20% water saving, the economic and ecological benefits and grain yield decreased. Under current and future mechanization levels, the fruit tree area increased under different water restriction scenarios. With no-water limitation, the economic and ecological benefits maximally improved after optimization, and water use and grain yield maximally decrease. Under the 20% water-saving scenario, the economic benefit increased the least, the ecological benefit decreased, and grain yield decreased the most. These results indicate that the current and future mechanization scenarios are not limited by water in the plain or mountainous areas, and the optimized economic and ecological benefits are relatively high. Moreover, in the plain areas with low water-saving requirements, the vegetable planting area should be increased, and the grain planting area should be reduced. In areas with high water-saving requirements, the planting area of all crops, including fruits and vegetables, should be reduced. In the mountainous areas, the grain planting area should be reduced, and the fruit tree planting area should be expanded. This study provides a decision basis for future regional planting structure adjustment. Past adjustments in the planting structure, with more adjustments according to different crop types, tended to ignore adjustments in the different cropping systems or to consider the fixed number of years or different climate scenarios. This paper proposed different scenarios of mechanization and water limitations and highlighted the optimization results under different scenarios for similar areas after adjustment in the planting structure.

Effects of long-term exogenous organic material addition on the organic carbon composition of soil aggregates in farmlands of North China

SUN Xue, ZHANG Yuming, ZHANG Lijuan, HU Chunsheng, DONG Wenxu, LI Xiaoxin, WANG Yuying, LIU Xiuping, XING Li, HAN Jian

2021, 29(8): 1384-1396. doi: 10.13930/j.cnki.cjea.210380

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Soil organic carbon and aggregates play an important role in soil fertility, crop yield, and the farmland environment, all of which are key components for sustainable agriculture. A wild long-term organic material and mineral fertilizer field experiment was initiated in 2003 at the Luancheng Agroecosystem Experimental Station of the Chinese Academy of Sciences. The experiment sought to investigate how different fertilization patterns affect the soil aggregate composition and the levels of organic carbon in the aggregates to better understand how different agricultural management practices serve as physical protection mechanisms. There were six treatments: no fertilization (i.e., conventional, CK), straw application alone (S), organic manure application alone (M), mineral fertilizer application (NPK), NPK plus straw (SNPK), and NPK plus organic manure (MNPK). The contents of total organic carbon (TOC), soluble organic carbon (DOC), acidolytic active organic carbon (AC), resistant organic carbon (ROC), and labile organic carbon (LOC) were examined within the aggregate fractions, including the total soil, large aggregates (>2 mm), small aggregates (0.25-2 mm), and microaggregates (< 0.25 mm). The results showed that fertilization had a significant effect on the distribution and stability of soil aggregates. SNPK significantly increased the amount of >0.25 mm aggregates. The contents of DOC and ROC were positively correlated with the amount of large aggregates and promoted the formation of large aggregates. Compared with NPK, SNPK and MNPK significantly increased the contents of SOC components in the aggregate fractions, and SNPK addition improved the SOC content compared to MNPK. In the aggregate fractions, the content of each organic carbon component was in the order of small aggregates > large aggregates > microaggregates, and more than 70% of the organic carbon came from the >0.25 mm aggregates. The LOC/TOC ratio in the MNPK and SNPK treatments increased to 14.95% and 15.70%, respectively, which was 11.94% under CK treatment. MNPK was conducive to LOC storage in large aggregates, which improved the soil fertilizer supply capacity; while SNPK promoted LOC migration to the small-sized aggregates, enhanced its stability in the aggregates, and improved the soil fertilizer retention capacity. In conclusion, long-term organic and inorganic fertilizer combined application improved soil carbon storage and stability. The study provides a theoretical basis for a nutrient management strategy with partial substitution of chemical fertilizer by organic manure and straw.

The response of soil organic nitrogen fractions and nitrogen availability to salinity in saline soils of the Yellow River Delta

SUN Han, QU Jie, WANG Xiaowen, ZHENG Wenkui, LI Chengliang, LIU Yanli

2021, 29(8): 1397-1404. doi: 10.13930/j.cnki.cjea.210002

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Abstract:
The soil organic nitrogen composition and nitrogen availability play important roles in the soil fertility and agricultural production of saline soils. This study investigated the effects of soil salinity on soil organic nitrogen fractionation and nitrogen availability in saline soils of the Yellow River Delta (YRD). Soil samples were taken from three wheat-maize rotation fields with low (2.28 g·kg^-1, S1), moderate (3.73 g·kg^-1, S2), and high (6.69 g·kg^-1, S3) salinities on the Huibang Bohai Farm in the YRD. The crop yields were recorded, and the soil organic nitrogen fractions, including ammonia nitrogen (AN), amino acid nitrogen (AAN), amino sugar nitrogen (ASN), hydrolyzable unknown nitrogen (HUN), non-hydrolyzable nitrogen (NHN), soil inorganic nitrogen, and microbial biomass nitrogen were quantified. The activities of the nitrogen transformation-related enzymes (i.e., urease, protease, and nitrate reductase) were determined, and the relationships between the soil organic nitrogen fractions, inorganic nitrogen, crop yield, and soil salinity were analyzed. The results showed that total acid hydrolyzable nitrogen (TAHN), which is the sum of AN, AAN, ASN, and HUN, was the main fractions of soil organic nitrogen, taking up 68.79%, 61.60%, and 52.30% of the total organic nitrogen in S1, S2, and S3 soils, respectively. The contents of the four TAHN fractions (AN, AAN, ASN, and HUN) were all significantly higher in S1 than in S2 and S3 (P < 0.05), and the contents of AN, AAN, and HUN were all significantly higher in S2 than in S3 (P < 0.05). The contents of these fractions were AN > HUN > AAN > ASN in S1, and AN > AAN > HUN > ASN in S2 and S3. Conversely, the NHN content was in the order of S1 > S2 > S3, but the differences were not significant (P>0.05). For the same soil, the NHN content was lower than the TAHN content. The highest soil nitrate nitrogen content (22.08 mg·kg^-1) and microbial biomass nitrogen (20.71 mg·kg^-1) were found in S1, which was significantly higher than those in S2 and S3 (P < 0.05). The ammonium nitrogen content did not differ among the three soils. The activities of urease and nitrate reductase were in the order of S1 > S2 > S3, and the differences were significant (P < 0.05). Protease activity was significantly higher in S1 than in S2 and S3 (P < 0.05). The total yield of wheat and maize in S1 was 1.74 times of that in S2 and 5.85 times of that in S3. Correlation analyses showed that the inorganic nitrogen, microbial biomass nitrogen, AN, and HUN contents had negative exponential relationships with the soil total soluble salt content, whereas the total yield of wheat and maize and the AAN content had significant negative linear relationships with the soil total soluble salt content. The soil inorganic nitrogen content was significantly and positively correlated with the soil TAHN content. The high total soluble salt content in the soils inhibited the formation of acid hydrolyzable organic nitrogen and improved the soil nitrogen availability. These results provide theoretical support for the regulation of soil nitrogen availability in saline soils in the YRD.

Applicability of spatial interpolation methods to predict total phosphorus in the typical irrigated areas of the Sanjiang Plain

ZHANG Di, JIANG Baizhi, LIU Guohui, ZHANG Hui, NIE Fan, SUN Qi, JI Mingyuan

2021, 29(8): 1405-1416. doi: 10.13930/j.cnki.cjea.200955

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Abstract:
In the late 1990s, the "Dryland to Paddy" project was implemented in the Sanjiang Plain. After planting rice in the Albic soil, the barrier soil layer turns into a favorable soil layer, the low-yield soil becomes high-yield soil, and the Albic soil phosphorus pool increases. After flooding, the availability of phosphorus (closed storage phosphorus[O-P] and iron-bound phosphorus[Fe-P]) increases with the decrease in soil redox potential (Eh) and the increase in pH, which substantially affects soil phosphorus heterogeneity. Therefore, we urgently need an optimal interpolation method to improve the prediction accuracy of total phosphorus in the Albic soil of typical irrigation areas of the Sanjiang Plain. This will help evaluate the impact of climate change and land use on the soil phosphorus pools and provide a reference for estimating future soil phosphorus pools. This study used the inverse distance weighting (IDW) method, radial basis function (RBF), ordinary Kriging (OK), global polynomial method (GPI), local polynomial method (LPI), geographic weighted regression (GWR), and geographic weighting regression to Kriging (GWRK) to predict the distribution of soil phosphorus in the Bawusan, Qiliqin, and Daxing irrigation areas of the Sanjiang Plain. The cross-validation method was used to obtain the mean error (ME), root mean square error (RMSE), and relative improvement (RI) to compare the accuracies of the various methods to determine the best interpolation method for assessing the spatial heterogeneity of phosphorus in the same soil type with different sampling densities. Based on the assumptions of regression analysis, this study incorporated 24 environmental variables for exploratory regression analysis, including elevation, pH, organic matter, exchangeable sodium, total nitrogen, available phosphorus, available copper, cultivated layer bulk density, and rice yield. According to the regression results, the auxiliary variables that were significantly correlated with phosphorus were selected for least square analysis. Finally, exchangeable sodium, cation exchange capacity, and available phosphorus were selected as auxiliary variables for the Bawusan irrigation area; organic matter, available zinc, and available boron were selected as auxiliary variables for the Qiliqin irrigation area; and cation exchange capacity, available zinc and copper were selected as auxiliary variables for the Daxing irrigation area. Compared to OK, RI indicated that the GWRK method with environmental auxiliary variables significantly improved the simulation accuracy of the spatial distribution of phosphorus. The IDW, GPI, and LPI methods reduced the accuracy of phosphorus spatial distribution simulation, whereas the RBF method was inconsistent. When comparing the mapping effect and interpolation speed of the seven interpolation methods, LPI, GPI, GWR, and GWRK had better mapping effects, whereas IDW, RBF, LPI, GPI, and OK were faster. The GWRK method had a better mapping effect, but it should be combined with environmental auxiliary variables, and the operation was complicated and slow. Sampling evenness also affected the prediction results. Nonetheless, GWRK had the lowest ME and RMSE, indicating that it is the best interpolation method. RBF is an optional method when the sampling evenness is lower. GWRK is the best interpolation method, but the results are affected by the number of auxiliary variables and collinearity between the variables.

Spatio-temporal characteristics of the hydrothermal conditions in the growth period and various gro wth stages of maize in China from 1960 to 2018

LIU Hang, ZHANG Xiaolong, WANG Yixuan, GUO Ying, LUO Jianmei, SHEN Yanjun

2021, 29(8): 1417-1429. doi: 10.13930/j.cnki.cjea.201009

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Abstract:
Hydrothermal conditions affect crop distribution and agricultural development. Maize is an important food crop in China and is primarily used as a fodder and energy crop. However, the growth of maize is sensitive to climate change. Understanding the spatiotemporal characteristics of the hydrothermal conditions, especially during the growth period and at various growth stages of maize, is crucial for food security and for coping with the impacts of climate change. This study aims to explore the spatiotemporal characteristics of the hydrothermal conditions during the maize growth period and its various growth stages in different regions of China from 1960 to 2018. The mean temperature (T_mean), growth degree-day (GDD), killing degree-day (KDD), sunshine hours (SD), effective precipitation (P_e), and irrigation water requirement (IR) served as the hydrothermal condition indicators, incorporating the data from 422 meteorological stations and 292 agricultural stations. The spatial and temporal variations of each indicator were explored using trend and spatial analysis methods. The results showed that T_mean and GDD generally increased in the maize growth period, 0.18~0.36℃·(10a)^-1and 5.73~41.23℃·(10a)^-1, respectively, and T_mean and GDD had risen more rapidly in Northeast China, the Gansu-Xinjiang Region, and the Huang-Huai-Hai Plain. KDD increased in the summer maize planting areas, including the Huang-Huai-Hai Plain and Gansu-Xinjiang Region. KDD tended to increase nationally except in the southwestern part of the Huang-Huai-Hai Plain, where there was an insignificant decline. In the various growth stages, KDD mainly increased from the seedling stage to the flowering and kernel stages. SD in the maize growth period showed a significant downward trend, and there was a significant downward trend in each maize growth stage in the Huang-Huai-Hai Plain and the Loess Plateau. SD declined the most in the flowering and kernel stages. Changes in P_e and IR during the maize growth period were generally non-significant, but the changes varied in different regions. P_e in different growth stages generally decreased, except in the Gansu-Xinjiang Region and Inner Mongolia, where, in past years, the P_e values increased non-significantly. IR in the maize growth period tended to decrease in southern Xinjiang and the southwestern part of the Huang-Huai-Hai Plain, whereas IR increased non-significantly in parts of Northeast China. In the various growth stages, P_e decreased and IR increased at the heading and flowering stages in the Huang-Huai-Hai Plain and Northeast China, whereas IR tended to decrease during the sowing and seedling stages in the Huang-Huai-Hai Plain and the western part of the Loess Plateau. Overall, there was an increasing trend of heat resources during the maize growth period in the whole country. Solar radiation tended to decrease, with no significant changes in P_e and IR. However, there were significant differences in the water and heat conditions among growth stages and regions; KDD significantly increased from the seedling stage to flowering stage in the Huang-Huai-Hai Plain and Loess Plateau, whereas SD decreased in the same regions. Thus, high-temperature stress may negatively impact maize growth and affect water consumption in different maize growth stages. This study illustrated that changes in the hydrothermal conditions during different maize growth stages were more important than those experienced during the entire maize growth period. However, knowledge of the possible spatio-temporal changes in the hydrothermal conditions in different maize growth stages is still lacking; particularly, the climate extremes during different maize growth stages in different regions of China. The results of this study highlight the impact of climate change on crop production, although more detailed research is needed.

Spatiotemporal characteristics of heat and rainfall in the three cotton areas of China under climate warming

HAN Wanrui, LEI Yaping, LI Yabing, HAN Yingchun, WANG Guoping, FENG Lu, LI Xiaofei, ZHANG Yongjiang, WANG Zhanbiao

2021, 29(8): 1430-1441. doi: 10.13930/j.cnki.cjea.210131

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Abstract:
Considerable climate change has occurred across the cotton planting area of China in the past few decades. Thus, it is important to study the temporal and spatial changes in water and heat resources during each growth period of the cotton-growing season and to propose corresponding technologies and strategies to stabilize the cotton production of China. Based on observational data from 377 meteorological stations and 50 agometeorological stations, this study analyzed the climatic trend rates of growth degree days (GDD), heat degree days (HDD) and rainfall from 1961 to 2017 in sowing-emergence, emergence-squaring, squaring-flowering, flowering-boll opening, boll opening-harvesting, and the entire growth period of cotton in the Northwest Inland (total cotton output accounts for > 80% of the country, including the northern Xinjiang subregion, southern Xinjiang subregion, eastern Xinjiang subregion, and the Hexi Corridor subregion), Yellow River Basin, and Yangtze River Basin cotton areas from 1961 to 2017. This study also recommended strategies to cope with the climate change-induced variations. The results showed that GDD generally increased over the past 56 years; during the entire growth period of cotton, 94.16% of the sites recorded increased cotton GDD. High GDD values at each growing stage were primarily distributed in the Naomao Lake, Hami, Yiwu, and Hongliuhe areas of the eastern Xinjiang subregion and in Jiuquan, Gaotai, and Zhangye of the Hexi Corridor subregion (the exception being the sowing-emergence and boll opening-harvest stages) followed by the northern Xinjiang subregion. The spatial distribution of HDD during each growth period markedly differed. During the squaring-flowering and flowering-boll opening periods, HDD tended to increase. Among all sites, 85.94% and 76.40% recorded increased cotton HDD, respectively. During the flowering period, cotton HDD increased, and there was a high-temperature risk in the east of lower reaches of Yangtze River subregion, east of the southern and northern Xinjiang subregion, the west of the Hexi Corridor subregion, the northwest of the extra-early maturing subregion of the Yellow River Basin, and in the eastern part of the upper reaches of the Yangtze River subregion. Overall, the lowest risk of high temperature was in the northern Xinjiang subregion. Rainfall during the entire growth period increased in the middle and lower reaches of the Yangtze River in the Yangtze River Basin and in most of the Northwest Inland. In other regions, rainfall tended to decrease. During the entire growth period of cotton, precipitation moved northward, and high precipitation in the Northwest Inland cotton area was primarily distributed in northern Xinjiang. During the sowing-emergence period, the drought risk in most cotton areas increased, except for areas with increased precipitation (the northern Xinjiang subregion). The GDD in the three major cotton areas increased overall, which benefited cotton area expansion and led to high yield and good quality. However, varieties with high yield potential should be selected. During the squaring-boll opening period of cotton in the Northwest Inland cotton area, there was a high-temperature risk in cotton planting in the eastern parts of the southern and northern Xinjiang subregions, the eastern Xinjiang subregion, and the western Hexi Corridor subregion. High-temperature resistant varieties and reasonable water and fertilizer management measures must be employed to cope with increased high-temperature risks. Drought risk is increasing in the cotton areas of the Yellow River Basin and the northern Yangtze River Basin; therefore, appropriate drought-resistant varieties and management measures should be adopted to reduce risks caused by climate change.

Impact of farmers' cognition on their participation behavior in the conser-vation of agricultural heritage systems: A case study of Anxi Tieguanyin Tea Culture System in Fujian Province

LIU Jilong, ZHANG Yongxun, LI Xiande

2021, 29(8): 1442-1452. doi: 10.13930/j.cnki.cjea.210022

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Abstract:
Farmers are the main actor and direct participant in the conservation of agricultural heritage systems (AHS), so their cognition towards AHS conservation can impact their participation in AHS conservation, as well as the sustainability of the AHS. Farmers' cognition of AHS conservation reflects the current measures of AHS conservation and is important for policy makers to establish improved policies. However, at present, farmers' inadequate participation in AHS conservation due to limited cognition has become a common problem in most AHS sites. According to the available literatures and on-site investigations, local conservation of Anxi Tieguanyin Tea Culture System (ATCS) in Fujian Province, one of the China National Important Agricultural Heritage Systems (China-NIAHS), has faced similar problems. This study used structural equation modeling (SEM) to estimate the impact of farmers' cognition on their participation behavior in the conservation of ATCS in Fujian Province under the framework of the Theory of Planned Behavior (TPB). We divided the farmers' cognition toward ATCS conservation into three dimensions: their attitude toward the behavior (ATT), the subjective norm (SN), and the perceived behavioral control (PBC). In total, 209 households engaging in tea planting in Anxi County were interviewed and included in the analysis. Our results showed that ATT positively influenced the willingness to participate in ATCS conservation, but it was not significant (P=0.396). This was in agreement with the results of other prior studies. However, the SN and PBC had significant positive impacts on farmers' willingness to participate in ATCS conservation (P < 0.1%) and indirectly and positively impacted farmers' behavior to participate in ATCS conservation via the intermediary role of their willingness to participate in ATCS conservation. The indirect effects of SN and PBC on farmers' behavior to participate in ATCS conservation were 0.292 and 0.442, respectively. The ability to participate in ATCS conservation and the institutional environment of ATCS conservation were critical factors for farmers' willingness to participate. The ability to participate in ATCS conservation primarily comprised the mastery of professional knowledge and basic technology and the affordability of the time costs of participating. The institutional environment of ATCS conservation mainly involved the initiative of the village committee and the county government in carrying out ATCS conservation. The ATT, SN, and PBC had a significant positive mutual influence. ATT and PBC had the largest mutual effect (0.652). These results inform policy recommendations to further promote the conservation and development of AHS. The publicity of AHS conservation should be strengthened to enhance the level of farmers' cognition of AHS conservation. Various levels of government should establish AHS conservation system to construct a good institutional environment to increase the initiative of carrying out AHS conservation. It is also necessary to improve and implement incentive policies to enhance farmers' abilities of participating in AHS conservation.

Estimation of elasticity relationship between agricultural ecosystem service values and urbanization

DENG Chuxiong, ZHU Damei, LI Zhongwu, LIU Changchang, NIE Xiaodong

2021, 29(8): 1453-1466. doi: 10.13930/j.cnki.cjea.200986

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Abstract:
The intensification of human activities and global climate change has exerted immense pressure on the ecological environment. According to the Millennium Ecosystem Services Assessment, approximately 60% of ecosystem services are declining globally. Therefore, to better maintain ecological health, promote human well-being, and achieve more sustainability in harmonizing environmental protection and socio-economic development, there is an urgent need to explore the relationship between ecosystem service values and urbanization. Using remote sensing monitoring data of land use from 2005 to 2015, this study investigated 58 counties in the hilly region of central Hunan Province. The transfer matrix of land use, evaluation method of ecosystem service values, estimation of the urbanization level, bivariate local spatial autocorrelation analysis, and construction of the elastic coefficient were used to analyze the spatial-temporal relationship between ecosystem service values and urbanization. The results showed that: 1) from 2005 to 2015, the value of agroecosystem services values decreased by ￥ 23.75×10⁸, and the high- and low-value areas were adjacent to each other in the hilly region of central Hunan Province. The level of urbanization increased by 6.24% in general, with low levels in the middle of the hilly area and high levels near the perimeter. 2) There were significant negative spatial correlations between the urbanization level and agroecosystem service values (P < 0.001) from 2005 to 2015. 3) The relationship between urbanization and agroecosystem service values was inconsistent in the hilly region of central Hunan Province from 2005 to 2015. These results provide a reference for coordinating the relationship between urban expansion, agricultural production, and the ecological benefits, strengthening the protection of green vegetation, reasonably controlling the growth of construction land, promoting the adjustment of industrial structure, and exploring the intensive and economic utilization of resources during land space planning.

2021 Vol. 29, No. 8