Table of Content

20 March 2019, Volume 28 Issue 3

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Effectiveness of different artificial restoration measures for soil and vegetation recovery on coal mine tailings in an alpine area

YANG Xin-guang, LI Xi-lai, JIN Li-qun, SUN Hua-fang

2019, 28(3):  1-11.  DOI: 10.11686/cyxb2018609

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Opencast coal mining causes major damage to the local ecological environment in alpine coal mining regions. It is important to evaluate the effectiveness of different artificial restoration options for revegetation and soil reclamation of coal mine tailings, in order to optimize the ecological restoration process. In this study, three restoration measures [revegetation of untreated mine tailings (R), revegetation with soil replacement (R-S), and revegetation and fertilization (R-F)] were implemented. Differences in vegetation community composition, plant growth and soil parameters under the different restoration measures, undisturbed grassland (UG) and untreated coal mine tailings (CK) were monitored and compared after 5 years. The main results were: The artificial grasslands that were developed under R, R-S, and R-F treatments differed in their botanical species composition, and there was significant variation in plant growth characteristics, including vegetation ground cover, height, density and above-ground biomass (P<0.05). Soil organic matter content increased significantly (P<0.05) in R, R-S, and R-F treatments, compared to CK. Compared with natural undisturbed grassland, the three artificial restoration treatments R, R-S, and R-F had inferior soil quality including soil fertility and pH value, at the end of the 5 year study period. Plant growth parameters were positively correlated with soil total nitrogen, soil organic matter, and especially with soil total phosphorus. Thus, synergistic promotion should be developed between the soil and plants. A single method such as artificial revegetation used alone is not conducive to ecological restoration. The combined use of artificial revegetation in conjunction with soil replacement or fertilization, proved to be effective for ecological restoration of coal mine tailings at this alpine site. From the perspective of effective vegetation restoration and cost reduction, treatments that include fertilizer, especially organic fertilizer are likely to perform better than replaced topsoil treatments. Using these cost-effective synergies arising from plant-soil interactions, reclamation of coal mine tailings and grassland ecosystem restoration would be facilitated.

Effects of different restoration measures on the soil organic carbon and nitrogen reserves in a desert steppe grassland ecosystem in Ningxia

YU Shuang, XU Dong-mei, XU Ai-yun, LIU Jin-long, TAO Li-bo

2019, 28(3):  12-19.  DOI: 10.11686/cyxb2018494

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This study investigated the changes of soil organic carbon and nitrogen in a desert steppe ecosystem in Ningxia under grazing (CK) and different vegetation restoration regimes, which included deep ploughed (S), shallow ploughed (Q), no-tillage (M) and enclosed (F). Soil samples were collected from 0-10 cm, 10-20 cm, 20-30 cm, and 30-40 cm soil depths. The results showed that the soil organic carbon contents were significantly greater (P<0.05) in the shallow ploughed treatment (14.90 and 14.50 g·kg^-1 in the 0-10 cm and 10-20 cm soil layers, respectively) than those in deep ploughed, enclosed and grazing treatments. For the 20-30 cm soil layer, the organic carbon content in the different treatments ranged from 5.03 to 9.93 g·kg^-1, and was highest in the shallow tillage treatment and lowest in the enclosed treatment (P<0.05). The total nitrogen (TN) contents for the 0-10 cm and 10-20 cm soil layers were both highest in the shallow ploughed treatment (0.17 and 0.22 g·kg^-1, respectively), and they were significantly higher (P<0.05) than those in the enclosed and grazing treatments. For the deeper soil layers, the total nitrogen contents were highest in the deep ploughed treatment (0.14 and 0.13 g·kg^-1, respectively, for 20-30 cm and 30-40 cm soil depths), while those in the enclosed treatment were significantly lower (P<0.05). Expressed on an area basis, the soil organic carbon densities in different soil layers of the various treatments ranged between 0.49 and 1.58 kg·m^-2, while the total nitrogen densities ranged from 0.013 to 0.039 kg·m^-2. The soil organic carbon densities at each depth of 0-40 cm layer and the total nitrogen densities at 0-10 cm and 10-20 cm were higher in the shallow ploughed and lower in the enclosed treatment. The total nitrogen densities for the 20-40 cm soil depth were highest in the deep ploughed and lowest in the enclosed treatment. For the 0-40 cm soil depth, the soil organic carbon and total nitrogen reserves in the shallow ploughed treatment were 47.72 and 1.09 t·ha^-1, respectively, and were significantly higher than those in the enclosed treatment (P<0.05). Thus, the shallow ploughed treatment is the most conducive among the tested treatments for accumulation of soil organic carbon and nitrogen reserves in desert steppe grassland of this region.

A study of soil nutrient characteristics and soil soluble organic carbon levels in different types of alpine grassland in Qinghai Province

ZHANG Miao-miao, CHEN Wei, LIN Li, ZHANG De-gang, WU Yu-xin, XIAO Hai-long

2019, 28(3):  20-28.  DOI: 10.11686/cyxb2018540

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This study aimed to explore the differences in soil carbon, soil nutrients and soluble organic carbon, and their correlation with soil nutrient levels in 4 different types of alpine grassland in Qinghai province. Measurements made included: soil organic carbon, total nitrogen, total phosphorus, total potassium, and soluble organic carbon in the 0-10 cm and 10-20 cm soil layers. Correlations between soluble organic carbon and organic carbon and nutrients were determined. The results showed that the ranking of the grassland types for contents of total nitrogen, organic carbon and soluble organic carbon in tested soil layers was alpine meadow>alpine meadow steppe>alpine steppe>alpine desert, with the differences being significant (P<0.05). As expected, the soil total nitrogen and organic carbon content tended to decrease with increasing soil depth. The soluble organic carbon aromaticity and humus indexes for the different alpine grassland types had the same rankings as for total nitrogen and organic carbon, above. There was a significant positive correlation between soluble organic carbon and soil total nitrogen and organic carbon (P<0.05). It was concluded that the contents of organic carbon, total nitrogen and soluble organic carbon in alpine meadow and alpine meadow steppe were high, and the structure of organic matter was complex. The soluble organic carbon aromaticity and humus indices were, to a certain degree, indicative of soil nutrient status.

Difference in soil microbial diversity in artificial grasslands of the Northwest Plateau of Sichuan Province

WU Wen-xian, ZHANG Lei, HUANG Xiao-qin, YANG Xiao-xiang, XUE Long-hai, LIU Yong

2019, 28(3):  29-41.  DOI: 10.11686/cyxb2018489

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In order to determine the influence of sown species in artificial grassland on soil microbial diversity in the Northwest Plateau of Sichuan province, an experiment was set up comparing stands of Medicago sativa (Ms), Avena sativa (As), and natural grassland (NG). The microbial community composition and structure of soil samples from the three vegetation types were analyzed by using Illumina Hiseq high-throughput sequencing technology. The results showed: 1) There was no significant difference among the three vegetation types with respect to the abundance and diversity of bacterial communities isolated from soil samples. The fungal community was nearly the same for As and NG, while Ms had higher fungal diversity than the other two vegetation types. 2) The dominant phyla of bacteria for the three samples were Proteobacteria, Acidobacteria, Actinobacteria and Verrucomicrobia. Acidobacteria were less abundant in the As soil than in the NG soil (P<0.05), whereas Actinobacteria had higher relative abundance in the As soil than in the NG soil (P<0.05). At the class level, Spartobacteria, α-proteobacteria, β-proteobacteria, Thermoleophilia, Acidobacteria and Actinobacteria were the predominant bacterial communities, and their relative abundance differed significantly among the three vegetation types (P<0.05). 3) The dominant fungal phyla were Ascomycota, Zygomycota, and Basidiomycota. The dominant taxonomic classes were Zygomycotes, Sordariomycetes, Agaricomycetes, Leotiomycetes, and Dothideomycetes, and the relative abundance of these dominant classes also differed significantly among the three vegetation types. 4) Beta-diversity analyses showed that the structure of soil fungal communities were significantly different among the three vegetation types, and soil microbial diversity coefficients for NG were greater than those for Ms and As. A cluster analysis showed that restoration by artificial grassland increased the relative abundance of beneficial microbes, but the relative abundance of soil plant pathogenic fungi was also significantly increased.

Effects of different crop rotations on soil nutrient, microorganism abundance and soil allelochemical levels in alfalfa

YIN Guo-li, CAI Zhuo-shan, TAO Rong, WU Fang, CHEN Jian-gang, SHI Shang-li

2019, 28(3):  42-50.  DOI: 10.11686/cyxb2018408

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This research aimed to explore the effects of different alfalfa crop rotations on soil nutrient, microorganism abundance, and allelochemical (autotoxin) levels. The alfalfa cultivar used was ‘Gannong No. 3’ and rotations compared were alfalfa-wheat (AW), alfalfa-wheat-wheat (AWW), alfalfa-corn (AC), alfalfa-corn-corn (ACC), and continuous alfalfa (CK). The results showed that: 1) Compared with CK, after the AC rotation, soil organic matter, ammonia, alkali decomposed ammonia, quick-test phosphorus were all reduced; after the AC rotation, the same soil parameters were more depleted than in AW (P<0.05). 2) In the various alfalfa-corn and alfalfa-wheat rotations, the numbers of soil bacteria and actinomycetes were increased significantly (P<0.05), with the treatment rankings being AWW>AW>ACC>AC. However, the number of fungi decreased, compared with CK, with percentage decreases being 48.96%, 65.19%, 66.72%, and 74.91% (P<0.05) for AC, ACC, AW, and AWW, respectively. 3) In the various alfalfa-corn and alfalfa-wheat rotations, soil levels of major allelochemicals, including chlorogenic acid, ferulic acid, caffeic acid, p-hydroxybenzoic acid, and coumarin, were all reduced. Average reductions after one year were, respectively, 17.90% and 27.50% (P<0.05) compared with CK, for AC and AW rotations. In AWW the allelochemical reduction compared to CK was 24.20%. It is concluded that well managed rotation of alfalfa, corn, and wheat could significantly improve soil microbial ecology, reduce the soil autotoxin content, and that soil nutrient deficiency was not the primary limiting factor to continuous cropping of alfalfa. In the semi-arid area in which the study was conducted, alfalfa-wheat rotation appeared the most suitable of the tested rotations and 2 years in wheat had a more pronounced soil detoxification effect. Alfalfa-corn rotations should be avoided, as they excessively deplete farmland fertility. Additionally, the population counts of soil microorganisms (particularly actinomycetes) and levels of soil allelochemicals assayed (as listed above) were generally significantly related.

Effects of Stellera chamaejasme patches on the surrounding grassland community and on soil physical-chemical properties in degraded grasslands susceptible to S. chamaejasme invasion

BAO Gen-sheng, WANG Yu-qin, SONG Mei-ling, WANG Hong-sheng, YIN Ya-li, LIU Sheng-cai, YANG You-wu, YANG Ming

2019, 28(3):  51-61.  DOI: 10.11686/cyxb2018205

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Species composition of a grassland community has significant effects on soil nutrient contents and nutrient distribution. Under grazing pressure, native plant species may be replaced by invasive or toxic weeds highly adapted to the local soil type, resulting in degraded grassland. Stellera chamaejasme is one such invasive species that has become the dominant species in degraded grassland in parts of the Qinghai region, where it is often found with patchy distribution within stands of other plant species. However, few studies have examined the effects of S. chamaejasme patches on the surrounding grassland community or on soil physical-chemical properties in degraded grassland of Qinghai-Tibet Plateau. Therefore, aboveground biomass, diversity indexes and soil nutrient contents were measured within or between S. chamaejasme patches in natural grassland or after herbicide treatment. It was found that aboveground biomass, species richness index and Shannon-Wiener index were significantly lower between patches than within patches untreated with herbicide. However, after herbicide application, the aboveground biomass and diversity indexes did not differ between and within S. chamaejasme patches. Meanwhile, soil water content, organic matter content, total nitrogen, available phosphorus, and NH4+-N contents were significantly higher within patches than between unsprayed patches. In addition, soil water, organic matter, and herbage total nitrogen contents within unsprayed patches were higher than within herbicide sprayed patches. However, available potassium content was higher within, than between patches receiving herbicide, Therefore, soil water and nutrient within-patch were higher than between-patch, demonstrating that S. chamaejasme patches had characteristics of a “fertile island”. Effective restoration of degraded S. chamaejasme grassland should include improvement measures, such as control of grassland carrying capacity, weed control, fencing and fertilization. With such measures in place, ecologically sustainable development of grassland where S. chamaejasme is present, can occur.

Effect of planting grasses and adding polyacrylamide on the shear performance and erodibility-resistance of purple soil in barren hillsides

ZHOU Tao, CHEN Yun, WANG Run-ze, LI Tie, TANG Han, ZHAI Ting-ting, LIU Xiao-hong

2019, 28(3):  62-73.  DOI: 10.11686/cyxb2018196

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This study investigated the effect of planting a grass-legume mixture and adding polyacrylamide (PAM) on the shear performance and erodibility-resistance of purple soil in a pot trial. Cynodon dactylon and Trifolium repens were chosen as the plant species. The experiment had four treatments: CK, bare soil; GL, planted in C. dactylon and T. repens; PAM, a single application of PAM; and GL+PAM. Root parameters, basic physical and chemical properties, shear strength (including its constituent components), and erodibility-resistance parameters were measured. The roots of C. dactylon and T. repens significantly reduced soil bulk density, and increased soil porosity and soil organic matter (P<0.05), and improved the soil shear performance and erodibility-resistance. PAM effectively promoted the growth of the root system, significantly improved the soil microstructure (P<0.05), especially the non-capillary porosity, which after the single application of PAM was 1.15-1.31 times that of CK. PAM also increased the shear strength and internal friction angle φ, the erodibility-resistance parameters of water stable aggregates >0.25 mm (WSA_0.25), water stable aggregates >0.5 mm (WSA_0.5), mean weight diameter (MWD) and geometric mean diameter (GMD) of soil aggregates. The improvement in shear performance and erodibility-resistance obtained using optimal concentration of PAM would be expected to stabilize purple soil in barren hillsides better. The main effect of roots in the GL pots was the improvement of soil shear performance (P<0.05), especially cohesion. PAM had a stronger effect on erodibility-resistance because of the formation of larger aggregates, thus significantly improving the degree of aggregation and soil aggregate structure (P<0.05). Compared with GL or PAM alone, GL+PAM produced the most obvious improvement in the shear performance and erodibility-resistance of purple soil in barren hillsides. The best performance was obtained with C. dactylon planting and addition of polyacrylamide at 30 g·m^-3 soil. The critical root diameter conferring shear performance and erodibility-resistance of soil was 0<d≤0.2 mm. Root length density and root surface area density of roots for which 0<d≤0.2 mm (RLD_0.2, RSAD_0.2), root length density (RLD) and root volume density (RVD) are key indexes of the contribution of roots to soil shear performance.

Ploidy determination of orchardgrass (Dactylis glomerata) using flow cytometry

XU Lei, CHEN Pei-lin, FENG Guang-yan, ZHONG Min-yi, JING Ting-ting, HUANG Lin-kai, ZHANG Xin-Quan

2019, 28(3):  74-84.  DOI: 10.11686/cyxb2018316

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Orchardgrass (Dactylis glomerata) is one of world’s most important forage grasses. Various ploidy levels exist, though most varieties are tetraploid or diploid. Rapid ploidy determination is needed to ascertain genetic background of collected germplasm and facilitate progress in breeding programmes. In this study, four kinds of nuclear DNA lysis buffer screen and two flow cytometry methods were compared in order to establish a rapid orchardgrass ploidy determination method. It was found that DNA extract quality varied with different lysis buffers. A superior nuclear suspension with complete peaks, small percentage of fragments, and clear fluorescent signal was obtained using Otto lysis buffer. In flow cytometry, both internal and external standard methods were tested. The external standard method was faster and simpler, while the internal standard method had higher accuracy in plant ploidy detection, with coefficient of variation being about 5%. There were 22 diploids and 24 tetraploids among 46 accessions tested, mainly using the external standard method. This work provided information on ploidy status of accessions, to support an orchardgrass breeding program.

Seed polymorphism and germination behavior of Salsola nitraria in the Gurbantunggut Desert

WANG Meng-ru, WEI Yan

2019, 28(3):  85-92.  DOI: 10.11686/cyxb2018168

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Salsola nitraria has a strong drought and salt-tolerance capacity in Xinjiang desert. Experiments were conducted to study the seed polymorphism and germination of S. nitraria. It produces three types of fruits that differ markedly in morphological characteristics and germination. Type A fruits are green and spherical and have winged perianth; Type B fruits are red and spherical, the perianth is without wings; Type C fruits are yellow and spherical, the perianth is without wings. Seeds were germinated in incubators at 5 ℃/15 ℃, 10 ℃/20 ℃, 15 ℃/25 ℃, 20 ℃/30℃, and 25 ℃/35℃ (12 h dark/12 h light) for 14 d. Germination percentages of type A seeds under all five temperature regimes were >92%; germination percentages of type B seeds under all five temperature regimes were <60%; germination percentages of type C seeds at all five temperature regimes were <5.3%. Type B seeds have no-deep physiological dormancy and seeds require 2 weeks of cold stratification to germinate. Type C seeds have deep physiological dormancy and scarification was an effective means of breaking the seed dormancy. Germination of type A seeds was not affected by NaCl at concentrations below 0.2 mol·L^-1, but was decreased by NaCl at higher concentrations, and fell to nearly zero at concentrations above 0.8 mol·L^-1. Seeds incubated in NaCl at concentrations of 0.05-4.0 mol·L^-1 recovered after being transferred to distilled water. Bracts of type A seeds formed a mechanical barrier to water uptake, and had a significant influence on the final seed germination percentages. Removal of bracts promoted seed germination. Further research into seed polymorphism in S. nitraria and the associated germination differences may reveal its ecological adaptive mechanism and provide data for ecological construction in the Xinjiang desert.

The effects of plant community structure on population density of plateau pikas (Ochotona curzoniae) in alpine meadow grassland

ZHANG Ling-fei, WEI Wan-rong, SHI Gao-yu, ZHANG Wei-guo

2019, 28(3):  93-100.  DOI: 10.11686/cyxb2017045

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This study investigated the effects of pasture renovation by grass reseeding or complete resowing with Elymus nutans on population density of alpine plateau pikas. To compare the population density of plateau pikas in different vegetation types, a 50 ha area of fenced pika-damaged (Pika) pasture was identified, and 20 ha of reseeded (R) and 10 ha resown E. nutans plots (En) were established within the Pika pasture. It was found that plant species number, species diversity, density, height, aboveground biomass and vegetation ground cover all differed in the three kinds of plots. The E. nutans % of biomass in the three pasture types was: Pika 3%, R 55%, and En 91%. The plant species diversity gradient was R>Pika>En. However, vegetation ground cover, density, height and aboveground biomass ranked En>R>Pika. There were significant differences in total burrow number and occupied burrow numbers in the three kinds of plots. Total burrow number per 50 m×50 m sampling plot was 210, 110, and 40 for Pika, R, and En grassland, respectively, while occupied burrow numbers were 120, 50 and 11 for Pika, R, and En grassland. The burrow number in the Pika plot was 2.26 times and 17.09 times that in the R and En plots, respectively. Thus, the data indicate that E. nutans vegetation has a very strong inhibitory effect on occupation by plateau pikas. Correlations between plant species numbers and vegetation characters, and pika population density were also observed. Neither total burrow number, nor available burrow number was significantly correlated with plant species numbers, but burrow numbers did show a quadratic function correlation with Shannon plant species diversity index. There were significantly negative correlations between pika burrow numbers and vegetation cover, density, height and aboveground biomass. These results proved that, compared with undisturbed grassland damaged by pika, the changes of vegetation structure in both reseeded grassland and resown grassland had an important influence on population density of plateau pikas.

The effect of sulfur forms on growth, physiology and secondary metabolism of Isatis indigotica at the seedling stage

MIAO Yu-jing, GUAN Jia-li, CAO Yi-wen, SHA Jun-tao, TANG Xiao-qing, GENG Li, WANG Lei

2019, 28(3):  101-110.  DOI: 10.11686/cyxb2018223

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To investigate the effect of S in different chemical forms on the growth, physiology and secondary metabolism of Isatis indigotica, an experiment with six treatments [CK (no added S), Na₂SO₄, Na₂SO₃, NaHSO₃, Na₂S and Na₂S₂O₃] was set up, and the changes in leaf fresh and dry weight, photosynthetic physiology, nitrogen and sulfur metabolism, nutritional components and content of indigo and indirubin studied, using a pot trial. It was found that the fresh and dry weight were greatest in the Na₂SO₄ treatment, with the NaHSO₃ treatment being second highest. Compared with CK, the other S treatments did not significantly promote biomass accumulation. The net photosynthetic rates and chlorophyll contents in sulfur treatments were higher than those observed in CK, and the highest observed net photosynthetic rate and chlorophyll contents occurred in the NaHSO₃ and Na₂S, respectively. Na₂S₃ and Na₂SO₄ increased the activities of nitrogen and sulfur metabolism enzymes respectively compared to other treatments, with the CK being no inhibiting obvious in their effect. The responses of nutritional components to sulfur forms differed. Soluble protein and soluble amino acid concentrations were decreased in CK plants compared to S-treated plants, with the highest soluble protein, free amino acid, and soluble sugar concentrations observed in the NaHSO₃, Na₂SO₄ and NaHSO₃ treatments, respectively. In contrast to the physiological responses, the levels of secondary metabolites indigo and indirubin were the highest in Na₂S treatment. Considering both growth stimulation and secondary metabolite accumulation, the Na₂SO₄ treatment is recommended as the most beneficial in the cultivation of I. indigotica seedlings.

Evaluation of physiological responses and tolerance to low-temperature stress of ten Elymus nutans varieties

LIANG Kun-lun, JIA Cun-zhi, SUN Jin-hao, WANG Ming-yan, FU Hua, MAO Zhu-xin

2019, 28(3):  111-121.  DOI: 10.11686/cyxb2018357

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This study investigated the cold-resistance capacity and adaptability of Elymus nutans germplasm collections from alpine grasslands. Germplasm collections of E. nutans were made from 7 localities in Gansu (Luqu, Zhuoni, Xiahe, Zhouqu, Hezuo, Lintan and Maqu), 2 localities in Sichuan (Aba and Ruoergai) and 1 locality in Qinghai Provinces (Gangcha). Plant seedlings (28 days old) from each collection were kept at 4 °C for 8, 24, and 72 h and physiological effects of the low temperature exposure were evaluated and the data analyzed using subordinate function analysis. It was found that under low temperature exposure, the relative membrane permeability of the germplasm collections was increased. The largest increases were found in Ruoergai and Aba for 8 h cold-stress (318% and 143%, respectively, compared to Control). Chlorophyll content was decreased by cold exposure, compared to Control, while free proline and soluble sugar were increased, with values of 458 μg·g^-1 FW and 4.80% FW in Aba and Zhuoni exceeding those of control by up to 95% and 207%, respectively. Enzyme activity of superoxide dismutase (SOD) and peroxidase (POD) was enhanced with short exposure, but weakened with longer exposure to cold stress. The strongest SOD enzymatic activity was found in Maqu and Luqu subjected to 24 h cold-stress (respectively, 147% and 148% higher than in Control plants). Meanwhile, the strongest POD enzymatic activity was found in Gangcha (220% higher than in Control plants). The evaluation of membership functions of the 10 regional germplasm collections on physiological index showed that those collected from Luqu, Zhuoni and Aba have stronger cold tolerance, the Ruoergai collection has moderate cold tolerance, and Lintan, Gangcha, Xiahe, Zhouqu, Hezuo and Maqu collections have weak cold tolerance.

Response of leaf osmolyte content to low temperature in autumn, and its relationship with chilling injury in centipede grass

LIU Nan-qing, LIN Shao-yan, SHEN Yi-xin

2019, 28(3):  122-130.  DOI: 10.11686/cyxb2018218

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Cold stress is a major problem for centipede grass (Eremochloa ophiuroides) and leaf osmolyte level is generally understood to be closely related to cold tolerance, but there are few studies specifically investigating response to cold stress in centipede grass. In this study, the relationship between cold tolerance of eight different genotypes and their leaf osmolyte content was studied in yield plot experiments conducted in Jurong Jiangsu during the winter chilling period from November to December of 2014. Our results indicated that the leaf color (greenness) was consistently decreased, while the leaf electrolyte leakage (EL) and malonaldehyde (MDA) contents were consistently increased during exposure to autumn chilling. Among the 8 genotypes, the EL and MDA content of genotypes E02, E07, E09 and E10 were significantly lower than those of the other four genotypes. However, the contents of soluble sugar, proline, spermidine and spermine of these genotypes were significantly higher than those of other genotypes. A correlation analysis of the data demonstrated a positive link between cold tolerance of centipede grass and particular osmolyte contents, in particular: soluble sugar, proline, spermidine, and spermine. Therefore, those four osmolytes in leaves play important roles in enhancing cold tolerance of centipede grass.

Effect of planting density on photosynthetic performance and yield of winter rye

ZHANG Xue-yue, ZUO Shi-yu, TIAN Li-xin, LI Li-jie, REN Xiao-song, LIU Zhao-yue, LI Jing

2019, 28(3):  131-141.  DOI: 10.11686/cyxb2018199

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This experiment aimed to explore the relationship between plant population density and photosynthetic performance and yield of winter rye in a cold region. The variety used was ‘Dongnong winter rye 001’, and the experiment comprised 5 replicates sowing densities (D₁, 225×10⁴ plants·ha^-1; D₂, 275×10⁴ plants·ha^-1; D₃, 325×10⁴ plants·ha^-1; D₄, 375×10⁴ plants·ha^-1; D₅, 425×10⁴ plants·ha^-1), arranged in a completely random design. Leaf chlorophyll content measured using a SPAD meter (CCM-200+) reached the maximum at the heading stage. With increased crop density, the SPAD value decreased, and the density-induced decrease was more pronounced after anthesis. The maximum values of net photosynthetic rate, stomatal conductance, transpiration rate and intercellular carbon dioxide concentration of rye leaves occurred at the flowering stage. With increasing crop density, many photosynthetic parameters, including the maximum photochemical efficiency (F_v/F_m), the actual photochemical efficiency (Φ_PSⅡ) and the photochemical quenching coefficient (q_P) showed progressive reduction; however, the non-photochemical quenching coefficient (q_N) increased. The yield of fresh and hay winter rye (Secale) were highest at D₃, after which the biomass yield decreased with increasing density. It is concluded that establishing the correct population density (D₂) to obtain higher photosynthetic capacity before flowering is the basis for obtaining high yield of winter rye in cold regions.

Effect of combined applications of selenium and zinc on herbage yield, Zn, Se accumulation and amino acid content of alfalfa

TIAN Chun-li, LI Bin, LIU Fang, ZHAO Ying, LIU Shi-liang, JIE Xiao-lei, HU Hua-feng

2019, 28(3):  142-153.  DOI: 10.11686/cyxb2018185

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This experiment investigated the effect of added zinc (Zn) and selenium (Se) in calcareous soils with severe Zn and Se deficiencies, on alfalfa yield and herbage Zn, Se, and amino acid content in a pot experiment. The design was a 3×3 complete factorial with three levels of Zn (0, 0.10, 0.40 g·kg^-1), and three levels of Se, also (0, 0.30, 1.80 mg·kg^-1). A comprehensive evaluation of alfalfa herbage amino acid composition as indicated by the amino acid score (AAS), chemical score (CS) and essential amino acid index (EAAI), was also undertaken. It was found that all treatments expect for Zn alone at 0.10 g·kg^-1 significantly increased alfalfa herbage yield. Se alone provided a greater increase in alfalfa herbage yield than Zn alone, and combined Se-Zn applications had the best effect. Similarly, alfalfa Se content was significantly increased by Se application, with combined application of Se and Zn showing a synergistic effect. Application of Zn significantly increased alfalfa Zn content, and combined application of Zn and Se at the lower rate promoted Zn absorption, whereas Se application at the higher rate was not conducive to Zn absorption. The total amino acid content of alfalfa herbage ranged from 15.88-18.89 g·100 g^-1, with the Se₁Zn₁ treatment having the highest value, and the Se₂Zn₂ treatment having the lowest. Meanwhile essential amino acid content of alfalfa herbage ranged from 5.11-6.45 g·100 g^-1, with the Se₁Zn₂ treatment having the highest values, and the Se₂Zn₂ treatment having the lowest value. The treatments Se₁Zn₀, Se₂Zn₁, Se₀Zn₂ and Se₁Zn₂ all had an essential∶total herbage amino acid value close to 40%. The first limiting amino acids in all treatments were the sulfur-containing amino acids (methionine+cystine). The results obtained in this study suggest that in the severely Se and Zn deficient calcareous soil tested, the optimal Zn application rate was 0.1-0.4 g·kg^-1 soil, and the optimal Se application rate was 0.3 mg·kg^-1 soil. These rates not only improved alfalfa herbage yield, but also improved amino acid composition and quality.

Effects of phosphorus application on hay yield and phosphorus contents of alfalfa under drip irrigation

SUN Yan-mei, LIU Xuan-shuai, ZHANG Qian-bing, WU Hao, ZHANG Xin-tian, MIAO Xiao-rong, LIU Jun-ying, YU Lei, MA Chun-hui

2019, 28(3):  154-163.  DOI: 10.11686/cyxb2018200

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This research aimed to explore the effect of different phosphorus (P) fertilizer application rates on the yield and P use efficiency of alfalfa, and to determine the soil total P and available P levels and plant tissue P levels under the different P fertilizer regimes. P fertilizer rates applied in the experiment were (as P₂O₅ equivalent) 0 kg·ha^-1 (CK), 50 kg·ha^-1 (P₁), 100 kg·ha^-1 (P₂) and 150 kg·ha^-1 (P₃). The P fertilizer was applied together with irrigation water under drip irrigation, beginning at the branching stage of spring growth following winter dormancy, and subsequently 3-5 d after the first, second and third cuts. The maximum P concentration of leaves and stems was attained under the P₂ treatment. The P concentration of leaves was 0.223%, 0.275%, 0.292% and 0.218%, under CK, P₁, P₂, and P₃ treatments, respectively; and the corresponding P concentration of stems was 0.202%, 0.223%, 0.201% and 0.146%. Hence, the P concentration of alfalfa leaves was higher than the P concentration of stems. The hay dry matter yield and elemental P yield were also maximized under the P₂ treatment (6.54 t·ha^-1 and 13.78 kg·ha^-1, respectively). Soil total P concentration and available P concentration increased with increased P fertilizer. The P fertilizer treatments had significantly greater soil P than the CK treatment (P<0.05). The P use efficiency decreased with increased P application, and was highest (28.37%) in the P₁ treatment at the first cutting. The phosphorus uptake of drip-irrigated alfalfa was significantly positively correlated with the hay yield of alfalfa (P<0.01). In conclusion, for the P₂ treatment (100 kg·ha^-1 P₂O₅), and this treatment promoted absorption of soil available P by the alfalfa roots, improved the P use efficiency of alfalfa, and improved the hay yield.

Effects of seeding rate and row spacing on the hay yield and quality of alfalfa in saline-alkali land

LÜ Hui-gang, KANG Jun-mei, LONG Rui-cai, XU Hua-ling, CHEN Xiao-fang, YANG Qing-chuan, ZHANG Tie-jun

2019, 28(3):  164-174.  DOI: 10.11686/cyxb2018153

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Appropriate seeding rate and row spacing are essential for optimizing alfalfa hay yield and quality. This paper reports a field experiment conducted from 2015 to 2017 to study the effects of seeding rate and row spacing on alfalfa hay yield, quality and other traits at the Dongying Academy of Agricultural Sciences experimental base, in the Huang-Huai-Hai area of Shandong Province. The Medicago sativa cultivar used was Zhongmu No.3. The experiment used a randomized complete block design with three replicates. Each replicate had 9 treatment combinations. Treatments were arranged as 3×3 factorial combination of three seeding rates (7.5, 15.0 and 22.5 kg·ha^-1) and three row spacings (15, 30 and 40 cm). Individual plot size was 5 m by 6 m, with 1.0 m spacing between the adjacent plots. This study was designed to determine the optimum seeding rate and row spacing when cropping alfalfa on saline-alkali land. It was found that seeding rate had significant effects on the yields in the establishment year but no significant effects on total yields over three years. Yield increased with seeding rate and the highest total yield was obtained at the seeding rate of 22.5 kg·ha^-1. There were significant differences for three years yields among row spacing treatments, with the total yield of the 15 cm row spacing treatment being the highest, and wider row spacings giving lower yields. The row spacing effect was large during establishment year, and gradually diminished over successive growing seasons. Considering seeding rate and row spacing, the combination of 22.5 kg·ha^-1 seeding rate and 15 cm row spacing resulted in the highest total yield over three years. Seeding rate and row spacing significantly affected the number of branches per m^-2 and branch weight. With increase in seeding rate and decrease of between-row spacing, the number of branches per m^-2 increased while the weight of branches decreased. There was a significant positive correlation between crop yield and number of branches per m^-2, and a significant negative correlation between crop yield and branch weight. With increase in seeding rate and decrease in row spacing, crude protein and relative feed value increased, but neutral detergent fiber and acidic detergent fiber levels decreased. The highest feed quality value was obtained with 22.5 kg·ha^-1 seeding rate and 15 cm row spacing. Based on both yield and feed quality data, the optimal planting regime at this site was 22.5 kg·ha^-1 seeding rate and 15 cm row spacing. In conclusion, it is recommended to plant saline-tolerant alfalfa varieties at a seeding rate of 22.5 kg·ha^-1 and a row spacing of 15 cm in saline-alkali land of Shandong province and Huang-Huai-Hai areas. The effects of seeding rate and row spacing on yield diminished in successive growing seasons. Optimal seeding rate and row spacing is helpful to improve the yield and quality of alfalfa crops.

Nutritional value of new Rumex varieties in stands of differing age in four ecological areas of Heilongjiang province

ZHAO Qiao-qin, XU Yong-qing, ZHOU Jing, FENG Shan-shan, CAI Zhen-xue, FENG Zhe, FENG Xu, PENG Li-na, DONG Jia-min, YAO Shu-kuan, LI Feng-lan, HU Bao-zhong

2019, 28(3):  175-183.  DOI: 10.11686/cyxb2018472

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In order to increase the range of high-protein forage options in Heilongjiang Province, a new variety of sorrel, ‘Щавель Чемпион’ (Rumex patientia×R. tianschanicus cv. Champion) was introduced. This study reports nutritional analyses of herbage from 2-3 year old stands sampled at key growth stages (rosette stage, stem elongation stage, flowering stage and fruiting stage) in Harbin, Xunke, Nenjiang and Huma regions of Helongjiang Province. It was found that the levels of crude protein (CP), crude fat (EE), crude ash (Ash), neutral detergent fiber (NDF), acid detergent fiber (ADF), Calcium (Ca) and Phosphorus (P) of ‘Щавель Чемпион’ in 3 year old stands was higher than in 2 year old stands in all four sampled growth stages. Environmental conditions in different provincial regions also had a significant impact on the yield and nutritional status of the Rumex herbage. For example, yield accumulation in Huma is much lower than in other areas because of its higher latitude, and lower accumulated temperature. CP levels of Rumex in Xunke and Nenjiang were the highest (P<0.05). ADF content of Rumex grown in Xunke was the lowest (P<0.05), and the Ash content of Rumex planted in Nenjiang was the highest (P<0.05). To summarise, the content of CP, ADF and Ash in Rumex herbage varies with crop growth stage and region; the nutritional value of the herbage increased with stand age in this study.

Effects of bacterial community composition on fermentation characteristics of Lactobacillus plantarum in low moisture content rice stalk silage

SI Hua-zhe, LI Zhi-peng, NAN Wei-xiao, JIN Chun-ai, LI Guang-yu, LIU Han-lu

2019, 28(3):  184-192.  DOI: 10.11686/cyxb2018217

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An experiment was conducted to investigate the effects of differences in the bacterial community on low moisture rice stalk silage fermentation characteristics, and the correlation between bacterial community composition and fermentation outcomes in the presence of lactic acid bacteria (Lactobacillus plantarum). In this study, volatile fatty acids (VFAs) were measured by gas chromatography, and bacterial community composition was measured by high-throughput 16S rRNA gene sequencing during ensiling (i.e. after 3, 5, 7, 10, 15, 30, 60 d). It was found that the inoculation of L. plantarum decreased either propionic acid, isobutyric acid, butyric acid, isovaleric acid, valeric acid contents (P<0.05), or abundance of Proteobacteria, while Enterobacter increased acetic acid content (P<0.05), and Lactobacillus, reduced microbial diversity compared to control samples. The most abundant phylum in low moisture silage were Proteobacteria, Firmicutes, Actinobacteria, Cyanobacteria, Bacteroidetes. The most abundant genera in low moisture silage were Enterobacter, Lactobacillus, Klebsiella, Serratia, Latococcus, Pantoea, Citrobacter, Raoultella, Enterococcus, Salmonella, Clostridium. Lactobacillus abundance was positively correlated with acetic acid and negatively correlated with valeric acid (VAL), and moreover, showed negative correlation with presence of the genera Enterobacter, Citrobacter, Bacillus, Pluralibacter, Lactococcus, and Weissella, the abundance of genera above-metioned were positively correlated with two or three production of propionic acid, isobutyric acid, butyric acid, isovaleric acid, and valeric acid. Lactococcus, Anaerobacter, Enterococcus, and Clostridium presence was positively correlated with propionic acid, isobutyric acid, and butyric acid formation. Fifteen genera altered VAL production during fermentation, while 5 operational taxonomic units were associated with acetic acid production. Weissella presence showed positive correlation with both propionic acid and isobutyric acid production. In summary, inoculation of L. plantarum improved the fermentation quality, inhibited VFA content, and reduce the diversity of bacterial genera in low moisture rice stalk silage.