中国生态农业学报(中英文)

Effect of root competition on growth and resource allocation of two spring wheat varieties cultivated at different times

ZHU Li, XI Nianxun, ZHANG Dayong

2020, 28(7): 945-953. doi: 10.13930/j.cnki.cjea.190867

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Abstract:
Belowground competition among individuals of the same genotype can result in root proliferation, a pattern called "tragedy of the commons". Reducing or eliminating root proliferation could increase seed yield. However, it is not clear whether root competition effect has been influenced by breeding. A greenhouse pot experiment was conducted using an old spring wheat landrace 'Monkhead' and a modern cultivar '92-46'. Root interactions were set up by adding a mesh partition or a plastic partition between two plants from the same variety. Root competition was also encouraged by placing two plants on the same side of the plastic partition. There were two nutrition treatments: 1 time nutrition application and 2 times nutrition application. We examined the effect of root competition by comparing biomass and resource allocation patterns among the partition treatments. Biomass data showed that plants in the 'mesh partition' treatment produced similar root biomass to those in the 'plastic partition' treatment without competition, but their shoot biomass and total biomass were higher. 'Monkhead' plants in the 'mesh partition' treatment produced similar seed biomass to those in the 'plastic partition' treatment without competition, whereas seed biomass of '92-46' plants in the 'mesh partition' treatment was higher. Root biomass and seed biomass in the '2 times nutrition-plastic partition with competition' treatment were similar to those in the '1 time nutrition-plastic partition without competition' treatment, but their shoot biomass and total biomass were lower. A standardized major axis regression analysis (SMA) showed that root allocation of 'Monkhead' was not affected by root competition, but root allocation of '92-46' was decreased slightly ('mesh partition' vs. 'plastic partition without competition'). Root competition had no effect on shoot allocation and seed allocation for both varieties. In addition, Our results revealed composition differences between two varieties. 'Monkhead' produced more roots and shoots, but less seeds than '92-46'. 'Monkhead' also allocated more resources to shoots and less to seeds than '92-46', whereas root allocation was similar between two varieties in most partition sets except for '1 time nutrition-plastic partition without competition'. We conclude that the presence of roots from a neighboring plant does not result in 'the tragedy of the commons' pattern in either 'Monkhead' or '92-46', but affect the resource allocation pattern in '92-46' to some extent. Modern '92-46' is somehow able to develop restraining and cooperative behaviour characteristics in the presence of roots from neighboring plants, whereas 'Monkhead' does not show any responses. The differences in resource allocation patterns between two varieties support Darwinian agriculture, which suggests that in order to enhance yield, crop breeding has consciously selected varieties associated with lower competitiveness.

Contribution of root morphology to phosphorus absorption in wheat and faba bean intercropping system

WANG Yuyun, LI Lan, ZHENG Yi, TANG Li

2020, 28(7): 954-959. doi: 10.13930/j.cnki.cjea.200163

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Intercropping is an effective way of enhancing efficient use of phosphorus resources through using the biological potential of crops. This study aims to explore the relative contribution of root morphological adaptations to phosphorus absorption under intercropping, and to explore how the wheat||faba bean intercropping system promotes phosphorus uptake. Wheat and faba bean were grown hydroponically under either adequate or deficient phosphorus levels. The effect of intercropping on their phosphorus uptake, growth traits, and root morphology were analyzed. The relative contribution of root traits to phosphorus uptake by wheat and faba bean were then analyzed using the aggregated boosted trees (ABT) method. Our results showed that under phosphorus deficient conditions, the uptake of phosphorus by wheat was higher in the wheat||faba bean intercropping system than in the monoculture. Conversely, phosphorus uptake by wheat under adequate phosphorus conditions was lower in the intercropping system. The uptake of phosphorus by faba bean was higher in the intercropping system than in the monoculture under both phosphorus conditions. The intercropping system led to a total phosphorus uptake that was 1.04 and 1.28 times higher than that of the corresponding monocrop system under adequate and deficient phosphorus conditions, respectively. This result indicated an advantage of intercropping over monocropping. Crop patterns and phosphorus availability resulted in significant effect in wheat height; interaction between these two factors was also observed (P < 0.05). Intercropping led to a decrease in plant height for both species. The ABT analysis suggested that root length and diameter played a major role in phosphorus uptake by wheat, accounting for 74.4% and 25.3% uptake, respectively. Root length, diameter, and surface area all appeared to account for the uptake of phosphorus by faba bean, accounting for 48.0%, 35.2%, and 16.9% uptake, respectively. To conclude, under phosphorus deficient condition, the improved phosphorus uptake by wheat in wheat||faba bean intercropping system was the result of an increase in root length and a decrease in root diameter, while the phosphorus uptake by faba bean was improved owing to an increase in root length.

Yellow-mud paddy soil productivity and phosphorus fractions under long-term different phosphorus supply levels in southern China

WANG Fei, LI Qinghua, LIN Cheng, HE Chunmei

2020, 28(7): 960-968. doi: 10.13930/j.cnki.cjea.200059

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Phosphorus (P) in red paddy soil is easily fixed by iron and aluminum, resulting in low P availability. Excessive phosphate fertilizer applications increase the risk of P leaching. The soil productivity, P pool balance, and characteristics of the P fractions at different levels of phosphate supply were studied in order to provide a basis for the efficient management of P in paddy fields across southern China. The study was based on a 30-year experiment in Fujian yellow-mud paddy fields. The experiment consisted of three P supply treatments in each season: control with no phosphate fertilizer (CK), 30 kg·hm^-2 P₂O₅ (P1), and 60 kg·hm^-2 P₂O₅ (P2). Double-cropping rice was planted from 1987 to 2004, and single-cropping rice was planted from 2005 onwards. The rice yields and P fractions changes under different P supply treatments over 30 consecutive years were studied. The results showed that the average grain yields of the early-season rice, late-season rice, and single-cropping rice significantly increased by 64.9%, 37.0%, and 19.9% in P1 treatment, and 67.0%, 41.2%, and 20.4% in P2 treatment, respectively. Early rice showed the highest increase in yield, followed by late rice and single-cropping rice. Under P2 treatments, in the 31^st year, the soil available P and total P contents in P2 treatment significantly increased by 190.5% and 32.4%, respectively, compared to P1 treatment. The Al-P, Fe-P, Ca-P, and total inorganic P contents also significantly increased, and the Al-P, and Fe-P fraction proportions significantly improved by 2.12 and 4.40 percentage points, respectively. However, the O-P fraction proportion significantly decreased by 9.45 percent points. Phosphate fertilizer applications generally increased the labile organic P (LOP) and medium labile organic phosphorus (MLOP) contents, but decreased the highly stable organic phosphorus (HSOP) content, especially in P2 treatment. Increasing the phosphate fertilizer application rate led to a rise in the proportion of LOP and MLOP to organic P, but it reduced the proportion of HSOP to organic P. Rice grain or straw yields were significantly positively correlated with Al-P, Fe-P, Ca-P, MLOP, and LOP contents. In conclusion, continuous applications of phosphate fertilizer significantly increased the grain yield in yellow-mud paddy soil over 30 consecutive years, but there was no significant difference in the grain yield between P1 and P2 treatments. However, apparent P deficiency was observed in P1 treatment. Increasing phosphate application rate led to a rise in the Al-P, Fe-P, and Ca-P proportions. The results showed that organic P fractions with lower activity changed into fractions with higher activity as the phosphate fertilizer application rate increased. The application of 60 kg(P₂O₅)·hm^-2 phosphate fertilizer per cropping season achieved the optimum apparent balance among P nutrients and maintained an appropriate level of available P.

Effect of phosphorus application on carbohydrate distribution in roots, stems and leaves of alfalfa and resistance to thrips (Thysanoptera: Thripidae)

HU Guixin, PENG Ran, CUI Xiaoning, LIU Yanjun, LI Yashu, ZENG Wenfang

2020, 28(7): 969-978. doi: 10.13930/j.cnki.cjea.190812

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The aim of this research was to clarify the distribution of carbohydrates in the roots, stems, and leaves of alfalfa with different phosphorus application rates, and the alfalfa's resistance to thrips. Two alfalfa varieties, 'Gannong No. 3' and 'Gannong No. 9, ' were used in this study. Odontothrips loti, which was the dominant pest of thrips in the alfalfa planting area of northern China, was selected as the research subject. Five soil phosphorus levels [0 (P1), 27(P2), 54(P3), 81(P4), and 108 mg(P₂O₅)·kg^-1soil (P5), were set. And alfalfa was infested with O. loti of 3 head·plant^-1 at the 6 leaf stage. The damage index was evaluated; the biomass of the leaves, stems and roots were measured; and the soluble sugar and starch contents of the leaves, stems, and roots were determined after the alfalfa was damaged by O. loti for 7, 14, and 21 days. The result showed that the damage index of 'Gannong No. 3' and 'Gannong No. 9' decreased gradually with increased phosphorus level, the lowest being at P3 level. The damage index of both alfalfa varieties decreased significantly after 14 and 21 days. The leaf, stem and root biomass of both alfalfa varieties increased significantly with increased phosphorus level. More biomass was distributed to the leaves in the early and middle stages (7 and 14 days), while it was distributed to the roots in the period of serious injury (21 days). However, the biomass allocated to stems was not significant. In 'Gannong No. 9', the biomass allocated to the leaves was more than that in 'Gannong No. 3' at the same phosphorus level. The soluble sugar and starch contents of the leaves, stems, and roots increased significantly with phosphorus level increasing. The soluble sugar content of the roots, stems and leaves increased, while the starch content decreased as the period of damage increased. The soluble sugar and starch contents of the leaves and roots of 'Gannong No. 9' were significantly higher than those of 'Gannong No. 3', which was damaged by thrips for 14 and 21 days. Phosphorus application enhanced the tolerance of alfalfa to thrips, with greater effect on 'Gannong No. 3'. Phosphorus application promoted the compensatory growth of the aboveground part at the moderate pest pressure and helped maintain root growth for the survival of alfalfa under severe pest pressure. Correspondingly, with the increase in damage time, the starch content of the root, stem, and leaves tended to decrease, and the soluble sugar content increased, showing that more resources were used to develop the photosynthetic and storage organs. P3 [81 mg(P₂O₅)·kg^-1 soil] was the best fertilization level for enhancing alfalfa's resistance to thrips in this research.

Optimal nitrogen application rate and nitrogen requirement characteristics of red kidney bean

GUO Caixia, HUANG Gaojian, WANG Yongliang, GUO Junling, YANG Zhiping

2020, 28(7): 979-989. doi: 10.13930/j.cnki.cjea.190874

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Red kidney bean (Phaseolus vulgaris) is one of the most important miscellaneous grain crops in Shanxi Province. However, its nitrogen requirement pattern has not been investigated, which has impeded nitrogen management. This research evaluated the nitrogen requirement pattern of the red kidney bean cultivar 'British Red' in Shanxi Province, China. The field experiments were conducted at Dongyang Agricultural Experimental Station, Shanxi Academy of Agricultural Sciences (central area of Shanxi Province), and at Caojiagou Village in Kelan County (western part of Shanxi Province). Four nitrogen application rates: 0 kg·hm^-2 (N1), 60 kg·hm^-2 (N2), 120 kg·hm^-2 (N3), and 180 kg·hm^-2 (N4), were applied at Dongyang, and five application rates: 0 kg·hm^-2 (N1), 60 kg·hm^-2 (N2), 120 kg·hm^-2 (N3), 180 kg·hm^-2 (N4), and 240 kg·hm^-2 (N5), were applied at Kelan. The accumulation and distribution of biomass and nitrogen uptake in different parts of the plants were monitored during the growth period. The grain yields and nitrogen translocation efficiencies at different nitrogen application rates were also determined. The results showed that there were significant differences in grain yield, biomass, and nitrogen accumulation among different nitrogen application treatments. The grain yield against nitrogen application rates analysis produced an odd peak curve, and the highest grain yields were found in the N3 treatment, which were 2 359.89 kg·hm^-2 and 2 452.26 kg·hm^-2 at the two field experimental sites, respectively. The hundred-grain weight was the main contributory factor to the yield difference. The dry biomass accumulation showed a pattern of "slow-fast-slow" as red kidney bean growth progressed. The highest percentage of grain in the biomass was recorded in the N3 treatment, and reached 49.97% at Dongyang and 47.65% at Kelan, respectively. The nitrogen uptakes by grain in the N4 (Dongyang) and N3 (Kelan) treatments were 0.72 g·plant^-1 and 0.99 g·plant^-1, respectively, which were higher than in the other treatments. In conclusion, the application of reasonable rates of nitrogen improved the translocation of nitrogen from vegetative parts to grain and helped improve nitrogen uptake by grain and its translocation efficiency, which might be the mechanism underlying the grain yield increase. The appropriate nitrogen application rate is 110.36 kg·hm^-2 in the central area of Shanxi Province and 126.31 kg·hm^-2 in the western part of the province, which can be finely adjusted according to the actual soil fertility and variety.

Differences in the two-crop yields and main-crop rice qualities among different hybrid mid-season rice varieties in the ratooning rice region of southern Sichuan, China

XU Fuxian, YUAN Chi, WANG Xuechun, HAN Dong, LIAO Shuang, CHEN Yong, ZHOU Xingbing, JIANG Qingshan, ZHANG Lin, JIANG Peng

2020, 28(7): 990-998. doi: 10.13930/j.cnki.cjea.200114

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Due to high temperature forced ripening, the yield of hybrid mid-season rice is low and rice quality is poor in the high temperature and drought-prone areas of south Sichuan. Therefore, it is important to make full use of the autumn temperature and light resources to improve grain yield and the quality of ratooning rice. A total of 12 new hybrid mid-season rice varieties, approved between 2015 and 2016, were used as materials to study the effects of environment on the yield and quality of main crop and ratoon in Longchang, Jiangan, Fushun, and Yibin, which are ecologically representative sites in southern Sichuan, China. The results showed that the difference in the main crop, ratooning rice, and total yields of two seasons among four sites was extremely significant. The main crop and ratooning rice yields of 12 rice varieties were significantly different, but the difference in total yields was not significant. There were 7 varieties ('Chuangliangyouhuazhan' 'Nei5you 907' 'Yixiang 4245' 'Luxiangyou 104' 'Huayou 357' 'Nei6A/Mianhui 138', and 'Longliangyou 1813') with more than 11 000 kg·hm^-2 yield over two seasons. There were no significant differences in gelatinization consistency of 6 rice varieties, but the other five traits were very significantly different among four sites. The rice quality in Yibin and Jiang'an were slightly better than in other two sites. The quality differences among 12 rice varieties and four sites were very significant, and the overall rice quality was relatively good for 'Chuangliangyou Huazhan' and 'Longliangyou 1813' varieties. There was a significant negative correlation between ratooning rice yield and main crop yield. However, there were no significant correlations between main crop yield and head milled rice rate, chalky rice rate, and chalkiness. The results showed that there was no obvious contradiction between high yields and three quality characters (milled rice rate, chalky grain rate, and chalkiness degree), indicating that improving the three quality characters under specific ecological conditions in southern Sichuan does not impeded rice yield increase. Varieties with a large grain length-width ratio had a reduced chalky grain rate, chalky degree, and amylose content, but an increased gel consistency.

Evaluation of low phosphorus tolerance and germplasm screening of spring wheat

LIU Lulu, WANG Juncheng, YAO Lirong, MENG Yaxiong, LI Baochun, YANG Ke, SI Erjing, WANG Huajun, MA Xiaole, SHANG Xunwu, LI Xingmao

2020, 28(7): 999-1009. doi: 10.13930/j.cnki.cjea.200098

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Phosphorus deficiency is one of the important abiotic stresses affecting agricultural production. Screening phosphorus-efficient crops is an important method for optimizing soil phosphorus and reducing phosphate fertilizer applications. In this study, the low phosphorus tolerance of 162 spring wheat germplasms was evaluated, and the tolerant materials were screened at seedling and adult stages. A correlation analysis and a principal component analysis of low phosphorus tolerance coefficients of eight indicators were conducted at the seedling stage to find the comprehensive indicators; a cluster analysis was performed to determine the low phosphorus tolerance of 162 materials according to their comprehensive evaluation value calculated with the subordinative function values. Then, low phosphorus tolerant materials and phosphorus sensitive materials were selected by determining the comprehensive evaluation value at the adult stage of the screened materials. The changes in acid phosphatase activity of the selected materials were analyzed. The results showed that there were different effects on the growth indicators at seedling stage and adult stage under low phosphorus stress, and that spring wheat growth inhibition increased as the stress time extension. Eight indicators at the seedling stage and 10 indicators at the adult stage were transformed into four comprehensive indicators (the cumulative contribution rate was 82.60%) and three comprehensive indicators (the cumulative contribution rate was 83.23%) by the principal component analysis, respectively. The cluster analysis showed that the 162 spring wheat germplasms at the seedling stage were divided into four types: low phosphorus tolerant (10 germplasms), slightly low phosphorus tolerant (26 germplasms), slightly low phosphorus sensitive (91 germplasms) and low phosphorus sensitive (35 germplasms). Five low phosphorus tolerant materials and four phosphorus sensitive materials were selected for phosphorus-efficient identification at the adult stage. Finally, one low phosphorus tolerant material, wp-35, and one phosphorus sensitive material, wp-119, were selected. The analysis of the two materials showed that the acid phosphatase activities in roots and leaves increased under low phosphorus stress, and that the acid phosphatase activity in wp-35 was higher than in wp-119. This study can provide germplasm resources, and a theoretical basis for the analysis of low phosphorus tolerance and the cultivation of low phosphorus tolerant spring wheat varieties.

Phosphorus efficiency comparison among cotton varieties cultivated at different times over 63 years

BAIDENGSHA·Maimaitiaili, SUN Liangbin, FENG Gu

2020, 28(7): 1010-1021. doi: 10.13930/j.cnki.cjea.200040

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Improving the phosphorus (P) fertilizer utilization rate is a major challenge when attempting to supply sufficient P nutrients in agriculture. Modifying the crop variety can effectively address this problem. The differences in P utilization efficiency among various cotton varieties cultivated at different times in Xinjiang, China, were clarified by setting up a single-factor random block design field experiment that investigated 22 different cotton varieties cultivated between 1950 and 2013. The P absorption and utilization efficiency characteristics of different cotton varieties during their seedling, budding, flowering, and wadding stages were monitored. Correlation and cluster analyses were used to evaluate the P efficiencies of cotton varieties. The results showed that P absorption efficiency, P utilization efficiency, and P transfer efficiency (from shoot to seed) differed among the 22 cotton varieties. At the wadding stage, the P absorption efficiency was 164.26-395.75 mg·plant^-1 with a coefficient of variation of 3.3%; the P utilization efficiency was 0.25-0.40 g·mg^-1 with a coefficient of variation of 67.7%; and the P re-transfer efficiency was 16.0-58.1% with a coefficient of variation of 11.1%. The P utilization efficiency, which always stayed between 0.30-0.32 g·mg^-1, did not significantly change over the three time periods (every 20 years was one period). Furthermore, P transfer efficiency did not significantly change and was around 93.9%-94.9%. In contrast, P absorption efficiency increased from 225.5 mg·plant^-1 to 286.3 mg·plant^-1, which was a 27.0% increase; and P re-transfer efficiency increased from 26.8% to 38.3%, which was an 11.5% increase. The P economic utilization efficiency rose from 20.6 mg·mg^-1 to 30.4 mg·mg^-1, which was a 47.6% increase. The correlation analysis showed that biomass was positively correlated with P absorption efficiency, but there was no significant relationship with P utilization efficiency. The lint cotton yield was positively correlated with P absorption, transfer, re-transfer efficiency, and economic utilization efficiency, but had no relationship with P utilization efficiency. The cluster analysis divided 22 cotton varieties into four types: P high-efficient type, P medium-efficient, P inefficient type, and extremely inefficient type. 'Xinluzao 50' 'Xinluzao 57', and 'Junmian 1' were P high-efficient varieties. The P high-efficient varieties had higher biomasses and yields than the other three types. In conclusion, these results highlighted that the use of high yielding cotton varieties in Xinjiang had prominently contributed to improvements in the absorption, transfer, and economic utilization of P.

Comprehensive evaluation of cold resistance in different parts of four wine grape varieties based on different thermal analysis

CHEN Renwei, ZHANG Xiaoyu, DING Qi, YANG Yu, NAN Xuejun, HU Hongyuan, FENG Rui, LI Fanghong, ZHANG Yahong

2020, 28(7): 1022-1032. doi: 10.13930/j.cnki.cjea.200151

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Freezing injury is one of the main meteorological disasters for grapes in northern China, and it seriously affects the growth and quality of wine grapes, which are soil-buried for winter protection in the northwest inland zones, and restricts the sustainable development of grapevine and the wine industry. The cold resistance of different parts of wine grape varies with the genetic characters of the grape varieties. In this paper, the cold resistance capacity of different parts of wine grape were measured using different thermal analysis (DTA) technologies to provide a theoretical basis for the prevention and mitigation of the winter freezing injury of grape. The physiological response indexes (supercooling point, freezing point, relative conductivity, and water content of branches) of four common varieties of wine grapes, namely, 'Cabernet Sauvignon' 'Merlot' 'Syrah, ' and 'Beimei', were measured by simulating the natural freezing schedule. Based on the fuzzy subordination function, the cold resistance capabilities of four wine grape varieties roots were comprehensively evaluated. The results showed that: 1) there were significant differences in cold resistance among different varieties, but the trend cold resistance of root and branch of the four varieties were identical. The order of cold resistance of the four varieties was: 'Beimei' > 'Cabernet Sauvignon' > 'Merlot' > 'Syrah'. 2) There was a significant correlation between the semi-lethal temperature and the supercooling point of the root system. Combined with the semi-lethal temperature, the temperature range of the supercooling points of the tested varieties roots was -5.2~-2.7 ℃, which could be used as the temperature reference index of the root system of four wine grape varieties. In all parts of the tested varieties, the cold resistance of branch was the strongest, the taproot was the second, the secondary root was the weakest, and the cold resistance capacity of the taproots was significantly better than that of the accessory roots. The results of this study are of significance to the monitoring, early warning, and improving the ability of wine grapes to resist overwintering freezing damage and provide a theoretical basis for the breeding of cold resistance ability in wine grape and the popularization and application of excellent varieties.

Comprehensive evaluation of quinoa seed responses to drought and salt stress during germination

WANG Zhiheng, XU Zhongwei, ZHOU Wuyan, YANG Xiuliu, HU Han, LI Chenghu, MA Weiliang, WEI Yuqing

2020, 28(7): 1033-1042. doi: 10.13930/j.cnki.cjea.200016

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With the development of quinoa industry, the responses of quinoa seeds to drought and salt stress at the germination stage have been gaining attention. In this paper, the drought resistance and salt tolerance of five quinoa cultivars (lines) (including 'South Africa No. 2' 'Longli No. 1' 'Longli No. 4', HTH-y605 and HTH-01) during germination were studied using indoor PEG-6000 simulated drought stress and NaCl simulated salt stress treatments. Germination rate and potential, seedlings length and fresh weight were determined. Principal component analysis was used to evaluate the drought resistance and salt resistance of quinoa, and the main evaluation indices for drought resistance and salt tolerance were identified. Results showed that different stresses had little effect on germination rate, germination potential, and germination index, but that they significantly inhibited seedling vigor index. The eight measured indices were classified into two component factors by principal component analysis, and the largest components related to seedling relative length and relative germination rate load, which could be used as main identification indices for quinoa drought resistance during the germination stage. The order of drought resistance of the tested cultivars (lines) was as follows: 'South Africa No. 2' > HTH-01 > 'Longli No. 4' > 'Longli No. 1' > HTH-y605. In terms of salt resistance, principal component analysis separated the eight indicators into three composition factors relating to the seedling relative length, relative germination rate, and relative germination index, respectively. The largest component factors can be used to identify quinoa cultivars (lines) with high salt resistance during germination. The order of salt resistance of the tested cultivars (lines) was as follows: HTH-01 > HTH-y605 > 'Longli No. 4' > 'Longli No. 1' > 'South Africa No. 2'. The drought resistance and salt tolerances of quinoa cultivars (lines) were sorted by the score function of the comprehensive factor of principal component analysis, and the results showed that 'Longli No. 4' had the strongest drought resistance, but the worst salt resistance. HTH-y605 had the strongest drought resistance as well as the strongest salt resistance. Correlation analysis showed that there was no significant correlation between drought resistance and salt tolerances of different quinoa cultivars (lines) at the germination stage. It was found that different quinoa cultivars (lines) were genetically diverse in terms of drought resistance and salt tolerance. The conclusion of this study provides a reference for research on the stress mechanisms of quinoa and for selective breeding of varieties, and provides theoretical and data to support the development of current low and medium yield fields.

Atmospheric reactive nitrogen in typical croplands and intensive pig and poultry farms in the North China Plain

LYU Xuemei, ZENG Yang, TIAN Shili, SUN Jie, ZHANG Guozhong, HUANG Wei, GU Mengna, XU Wen, LIU Xuejun, DONG Hongmin, MA Lin, CHENG Yisong, HU Chunsheng, WU Dianming, PAN Yuepeng

2020, 28(7): 1043-1050. doi: 10.13930/j.cnki.cjea.190879

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Reactive nitrogen (N_r) is the main precursor of atmospheric haze pollution, which leads to excessive nitrogen deposition. With prevention and control measured for air pollution in recent years, reducing N_r from agricultural sources has recently been suggested. Currently, field measurements focusing on atmospheric N_r in farmland and animal farms are still limited and are mainly focused on ammonia (NH₃), with little attention being paid to other N_r components. In order to characterize the potential impact of agricultural activities on atmospheric N_r concentrations, this study carried out simultaneous field measurements of major N_r species, including gaseous NH₃, nitric acid (HNO₃), particle ammonium (p-NH₄⁺) and nitrate (p-NO₃^-), in two farmlands (Xianghe farmland and Luancheng farmland in Hebei Province), a pig farm and a poultry farm in the North China Plain using the active denuder sampling system. The results showed that the average concentrations of NH₃ and p-NH₄⁺ inside the pig house (1 250.9 and 76.6 μg·m^-3, respectively) were significantly higher (P < 0.05) than those outside the pig house (378.5 and 4.2 μg·m^-3, respectively). However, the average concentrations of HNO₃ and p-NO₃^- inside the pig house (10.3 and 20.8 μg·m^-3, respectively) were comparable to those outside the pig house (9.8 and 22.1 μg·m^-3, respectively). In contrast, the measured N_r concentrations were similar both inside and outside the poultry house for all N_r species (overall ranged from 6.2 to 10.7 μg·m^-3) except for NH₃, which was significantly higher (P < 0.05) inside (197.7 μg·m^-3) compared to outside (77.3 μg·m^-3). In general, atmospheric N_r concentrations in the pig farm were significantly higher than those in the poultry farm (P < 0.05). The average air concentrations of NH₃, p-NH₄⁺, HNO₃ and p-NO₃^- in the farmland were 21.4, 1.9, 4.4 and 5.5 μg·m^-3, respectively, which were significantly lower than those outside the pig and poultry farms (P < 0.05). From the perspective of chemical composition, N_r mainly existed in the form of NH₃-N (accounting for more than 80%) in pig, poultry and farmland environments, which indicated that the N_r produced by agricultural activities in the North China Plain mainly diffused outward in the form of NH₃ instead of transforming into particles locally. Detailed investigations on the transmission mechanisms and transport pathways of N_r in the atmosphere are urgently needed to provide scientific support for the implementation of effective emission mitigation measures.

Effects of nitrogen fertilizer and returning straw on aquaculture water, soil nutrients, and enzyme activity in rice-crayfish fields during winter and spring

LI Wei, CHENG Yongxu, SUN Ying, LIU Xiaofei, LIU Mingming, CHEN Huangen, LI Jiayao

2020, 28(7): 1051-1060. doi: 10.13930/j.cnki.cjea.200056

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The integrated rice-crayfish breeding model is an ecological agriculture model that combines paddy field plantation and crayfish (Procambarus clakii) cultivation. This model both guarantees food production and increases economic benefits. At present, research relating to this model is focused on the efficiency of crayfish culture technology, while information regarding straw resource utilization under this model has not been reported. Rice straw is rich in nitrogen, phosphorus, and potassium. However, if improperly handled and directly immersed in water, its degradation process will cause deterioration of water quality and pollution of soil. Therefore, returning straw to the field not only effectively uses resources, but also avoids the risks caused by random straw disposal. In order to explore the optimal model for returning straw during winter and spring (when crayfish are breeding), we carried out a field experiment to study the effects of different C/N ratios of straw returning on cultured water, soil nutrients, and enzyme activity in Dec. 2017 to May 2018. The experiment consisted of five treatments: straw removal without fertilizer (CK), straw returned without N fertilizer (C/N ratio of 35:1, S), straw returned with N fertilizer (adjusted C/N ratio of 25:1, SN1), straw returned with N fertilizer (adjusted C/N ratio of 15:1, SN2), and N fertilizer without straw returned (N1). The results showed that total phosphorus (TP) content was the lowest in the CK treatment at the later stage of straw returning period. The total N content in each period was the lowest in CK treatment, followed by SN2 treatment. The ammonia nitrogen (NH₄^-) content in the treated water was lower than the safe tolerance limit of the crayfish. Additionally, the soil organic matter content increased under straw returning; the most significant result was obtained in SN2 treatment, with an increase of 56.1% compared to before the field experiment. Soil nitrate nitrogen (NO₃^-) content in SN2 treatment increased by 240% compared to that before straw returning. Returning straw reduced bulk density of soil. The SN2 treatment recorded the lowest bulk density overall. Finally, we found that N1 and SN2 treatments could increase soil polyphenol oxidase activity; activity was highest in SN2 treatment group. Among three straw returning treatments, soil urease activity in SN2 treatment was lower than that in other treatments only in the first month after returning to the field. N1 treatment showed higher enzyme activity in the early experimental stage and began to decrease in the later stage. Overall, the results suggest that an optimal C/N ratio for returning straw with N fertilizer was 15:1, in terms of soil nutrient content and enzyme activity.

Effect of straw maturing agents on fungal diversity in soil with different textures under returned straw conditions

SARULA, YANG Hengshan, TAI Jicheng, GAO Julin, LI Yuanyuan

2020, 28(7): 1061-1071. doi: 10.13930/j.cnki.cjea.190900

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Abstract:
In order to select a straw maturing agent suited to local conditions, straw return on medium and sandy loam were investigated in a continuous maize crop in the West Liaohe Plain irrigation area. Straw returned to the field was treated with Zhongnonglvkang, Renyuan, or Nongfukang maturing agent, or without maturing agent as a control. The diversity and community structure of soil fungi was studied using a high-throughput sequencing technique in 0-15 cm, 15-30 cm and 30-45 cm soil layers during the maize silking stage. The results showed that the number of OUT (operational taxonomic units) in sandy loam treated with returned straw and maturing agent was higher than that of control. However, in medium loam, the results were opposite. The relative abundance of Mortierellomycota, Ascomycota, and Basidiomycota for all treatments was higher than in the control, the dominant genera being Mortierella and Guehomyces. Different straw maturing agents and soil textures resulted in different fungi responses. The composition and abundance of soil fungi in medium loam were not significantly affected by returning straw with Zhongnong and Nongfukang application, although applying Renyuan led to significant changes. Significant composition changes and an increase in soil fungi abundance were identified in sandy loam when returned straw was treated with Zhongnong and Renyuan. The results of Linear discriminant analysis Effect Size (LEfSe) analysis showed that soil fungi diversity differed among three treatments. For sandy loam with Zhongnong application, medium loam with Renyuan, and medium loam with Nongfukang, the most significant fungal classifications were phyla Basidiomycota and Ascomycota, class Agaricomycetes, orders Pleosporales and Agaricales, and species Mortierella fimbricystis. The difference in treatment response was also reflected in the maturing agent effects on fungi in different layers of medium and sandy loam. With increased depths, the relative abundance of Mortierella spp. first increased and then decreased, while the relative abundance of Guehomyces spp. decreased. The relative abundance of Guehomyces spp. in deep soil was higher than that in surface soil after the application of straw maturing agent (except for Nongfukang in medium loam). The relative abundance of these two dominant genera in the 0-15 cm soil layer was significantly increased in sandy loam by returning straw and applying Zhongnong. In medium loam, returning straw and applying Renyuan increased the relative abundance of Guehomyces spp. in the 0-15 cm soil layer and the relative abundance of Mortierella spp. in the 15-45 cm soil layer. Under returned straw conditions, effects of straw maturing agent varied with soil texture; therefore, the combined application of straw and straw decomposing agents should be adapted according to local conditions.

Effects of salinity stress on the oxygen consumption and ammonia excretion rates of the invasive fresh snail Pomacea canaliculata

LIU Pengyuan, ZHANG Chunxia, ZHAO Benliang, ZHANG Jia'en

2020, 28(7): 1072-1078. doi: 10.13930/j.cnki.cjea.200045

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Abstract:
Pomacea canaliculata (Lamark 1822) is one of the 100 worst alien invasive species in the world. To date, P. canaliculata snails have been mainly studied in freshwater areas, such as paddy fields, canals, ditches, rivers, and lakes, whereas there have been only a few studies on the potential risk of P. canaliculata spreading to salty water areas. In order to investigate the response differences of small, medium, and large P. canaliculata snails to salt stress, we determined the oxygen consumption rate and ammonia excretion rate of the three differently sized snails under five salinity treatments (0, 2.5, 5.0, 7.5, and 10.0 g·L^-1) using the hydrostatic method. The results showed that salinity, snail size, and their interactions had significant effects on the oxygen consumption and ammonia excretion rates of the snails (P < 0.001). The oxygen consumption and ammonia excretion rates of the studied snails reached a peak at 2.5 g·L^-1 salinity. However, between 2.5-10.0 g·L^-1 salinity, they gradually decreased as the salinity increased. There was a negative correlation between oxygen consumption rate or ammonia excretion rate, and the dry meat weight (oven-dried at 65℃ for 48 h) of the snails. The oxygen consumption rate and the ammonia excretion rate followed the order small snails > medium snails > large snails. The oxygen-nitrogen ratio (O/N) for P. canaliculata ranged from 5.80 to 30.46, reaching a peak when the salinity was 2.5 g·L^-1, and then gradually decreased as the salinity increased. There were no significant differences in the O/N among the three differently sized P. canaliculata snails compared to the control group when the salinity was 2.5-7.5 g·L^-1. This study showed that the snails could survive for a short period of time in a saline environment with a salinity below 7.5 g·L^-1.

Temporal and spatial pattern evolution and grouping prediction of non-point source pollution of chemical fertilizers in China

LEI Junhua, SU Shipeng, YU Wenmeng, SUN Xiaoxia

2020, 28(7): 1079-1092. doi: 10.13930/j.cnki.cjea.190923

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Abstract:
Reducing pollution caused by chemical fertilizers while continuously increasing the output value of agriculture at the same time is an inevitable requirement to improve high quality development of agriculture. Actions aimed at achieving zero growth in chemical fertilizer use have been formulated and implemented in provinces across China. However, inconsistencies in progress and effectiveness among provinces may affect each other. The fertilizer loss coefficient method was used to calculate the emission intensity of non-point source pollution in 31 provinces across the Chinese mainland from 1997 to 2018. Spatial autocorrelation and hotspot analysis methods, based on the calculated emission intensity, were used to reveal the emission intensity temporal and spatial characteristics, and to analyze the interaction effect on neighboring provinces. According to these characteristics, the country was grouped into three regions: a hot spot region, a cold spot region, and a non-hot (cold) spot region. Then, the Environmental Kuznets Curve (EKC) trend between the non-point source pollution emission intensity of fertilizers and the per capita agricultural output value in each group was simulated and predicted under spatial heterogeneity and spatial correlation conditions. The results showed that the emission intensity varied considerably among provinces across the country. The emission intensity was spatially positively autocorrelated across the country with a cluster mode. A hot spot analysis showed that the spatiotemporal pattern for non-point source pollution caused by fertilizers was relatively stable. The hot spot region was mainly concentrated in the central and southern parts of China, especially in the middle and lower reaches of the Yangtze River. However, in recent years, the number of hotspots in the Huanghuaihai region had significantly decreased. The cold spot region was mainly concentrated in the western region and Heilongjiang Province. The EKC trend simulation, based on temporal and spatial pattern feature grouping, showed that there was a significant nonlinear EKC relationship between agricultural economic growth and chemical fertilizer non-point source pollution in each group. However, the trend and the inflection point of each curve were clearly different. The hot spot region appeared as an "inverted U-type" curve, but both the cold spot region and the non-hot (cold) spot region had "inverted N-type" curves. Most provinces in each region were in the ascending phase of the curves. Industrial structure adjustment and industrial transfer promoted the spatial spillover effect of fertilizer derived non-point source pollution among the regions. Therefore, coordinated governance among regions needs to be introduced. Based on the above results, we propose that there should be corresponding policy implications, and that suitable fertilization equipment should be developed and promoted to increase fertilizer utilization in the hot spot region. Conservation farming should be applied and the use of organic fertilizer promoted in the cold spot region. The non-hot (cold) spot region should reasonably adjust the structure of its agricultural industry and focus on the crop-livestock and poultry farming cycle. Ecological compensation and emissions trading should be implemented to achieve collaborative governance.

Habitat quality evaluation before and after unused land development based on InVEST model: A case study of Tang County

CHEN Yaqian, ZHAO Li, TAO Jinyuan, ZHANG Pengtao

2020, 28(7): 1093-1102. doi: 10.13930/j.cnki.cjea.190862

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Abstract:
At present, habitat quality is under constant threat due to the impact of human activities. Therefore, it is particularly important to assess habitat quality status and trends. In this study, the Habitat Quality module of InVEST model was used to analyze the impact of unused land development on habitat quality in Tang County, China in 2000, 2007, and 2016. The results showed that 1) from 2000 to 2016, the development direction for unused land was mainly grassland, forest land, and cultivated land. The proportion of unused land decreased from 100% (based on the unused land area in 2000) to 33.70%, whereas the proportion of grassland, forest land, and cultivated land increased from 0% to 27.43%, 21.30%, and 10.46%, respectively. 2) The proportion of unused land patches in the landscape area of Tang County decreased year by year. The average patch area decreased from 94.73 hm² before development to 6.15 hm² after development, and the forest land, water area, and grassland proportions in the landscape area increased. Furthermore, the evenness and diversity indexes increased after the unused land was developed and ecosystem stability improved. 3) After the exploitation of unused land, the habitat quality in the study area significantly improved, and the habitat quality score increased from 0.09 in 2000 to 0.28 in 2007, and then to 0.39 in 2016. The habitat quality high value areas were mainly located in the middle of the study area and northwest of Qijiazuo Town, the southern part of Huangshikou Town and the northern part of Yangjiao Town. However, the habitat quality in Chuanli Town, Juncheng Town, and Luozhuang Town, and in the southern region was lower. This study analyzed the impact of unused land development on habitat quality, and the results provide a scientific basis for making reasonable land planning decisions and for protecting habitat and biodiversity during land development.

2020 Vol. 28, No. 7