Table of Content

20 November 2020, Volume 29 Issue 11

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Dynamic monitoring of net primary productivity and its response to climate factors in native grassland in Inner Mongolia using a light-use efficiency model

WU Ni-tu, LIU Gui-xiang, YANG Yong, SONG Xiang-yang, BAI Hai-hua

2020, 29(11):  1-10.  DOI: 10.11686/cyxb2019543

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Based on a light-use efficiency model and MODIS data, the net primary productivity (NPP) of grassland during the growing seasons from 2000 to 2018 in native grassland in Inner Mongolia was continuously estimated, and the spatial-temporal change trend of NPP over the past 20 years was also analyzed using a least square method at pixel scale to determine the degree of grassland degradation. It was found that NPP increased from west to east across Inner Mongolia, with an annual average of 198.04 g C·m^-2·yr^-1. An area of potential grassland degradation of 162200 km² was identified. The areas of severely and heavily degraded grassland identified were 2000 and 11100 km², respectively. The latter were mainly distributed in areas with intensive human activities, such as mining areas, or construction land and its surrounding areas. In terms of grassland types, the potentially degraded areas of temperate steppe, temperate meadow, temperate desert and temperate desert-steppe were 52200, 14000, 40400 and 22100 km² respectively. Through analyzing the correlation between NPP and climate factors in the last two decades, it was found that NPP is significantly correlated with precipitation, but has no correlation with temperature. The response of NPP to precipitation was the most sensitive in temperate meadow, that of temperate desert steppe was the second, and that of temperate steppe was the lowest. Based on the above results, this paper puts forward some suggestions for grassland ecological protection.

Effects of fence enclosure on the plant community composition and niche characteristics in a temperate meadow steppe

NIE Ying-ying, XU Li-jun, XIN Xiao-ping, CHEN Bao-rui, ZHANG Bao-hui

2020, 29(11):  11-22.  DOI: 10.11686/cyxb2020239

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This study explored the effects of fence enclosure on community composition and niche characteristics in temperate meadow steppe. The indexes Levins niche breadth, Pianka niche overlap and species diversity were used to evaluate the degree of resource utilization by species and the intensity of interspecific competition inside and outside the enclosure. It was found that: the fencing enclosure significantly promoted vegetation restoration of degraded grassland. The aboveground biomass and belowground biomass in the enclosure treatments were enhanced by 255.06% and 51.06%, respectively. The species diversity and richness were enhanced in fenced enclosures by 10.36% and 10.34%, respectively. The two species with the highest niche breadth in enclosures were Iris ventricosa and Leymus chinensis, with values of 0.921 and 0.873, respectively. In comparison, the two species with the highest niche breadth in the freely grazed grassland were Taraxacum mongolicum and Carex duriuscula, with values of 0.912 and 0.791, respectively. Our results clearly show that enclosure by fencing is an efficient restoration measure that not only promotes species diversity but also improves grassland productivity. Compared with free grazing, fencing enclosure increases the overall niche overlap value and inter-species competition of plant communities and their component plant populations.

Relationship between soil moisture and vegetation cover in Qilian Mountain alpine steppe

LU Feng-shuai, ADE Lu-ji, CHENG Yun-xiang, HOU Fu-jiang

2020, 29(11):  23-32.  DOI: 10.11686/cyxb2020015

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This study investigated the relationship between soil moisture and vegetation cover in alpine steppe meadow in the Qilian Mountains with the aim of improving the precision of remote sensing estimates of soil moisture and vegetation cover. Six sample areas with different stocking rates of Cervus elaphus kansuensis (1.00, 1.45, 2.45, 3.45, 4.85, 6.90 AUM·ha^-1) in were set up, AUM means animal unit. Through comparing data from monthly field measurement of vegetation cover and soil moisture and SPOT-TM images combining Landsat5 multispectral images and SPOT2 panchromatic images, we analyzed the relationship between soil moisture, vegetation cover and normalized difference vegetation index (NDVI) and quantitatively explored the dynamics of seasonal change in vegetation cover and soil moisture in the sample areas in the Qilian Mountain alpine steppe. Except for Achnatherum inebrians, Convolvulus ammannii and Stragalus leucocephalus, the response of population cover to surface soil moisture was relatively sensitive, with the population cover of species inversely proportional to soil moisture in the range between c. 5% and c. 25%. The response of plant community cover to surface soil moisture was also relatively sensitive. In the soil moisture range from 10.0% to 1.1%, the community cover increased in the inverse proportional function. The results are highly relevant to remote sensing monitoring of the drought resistance and water use efficiency of plant species, populations and communities in arid and semi-arid steppe grassland, and provide scientific data for vegetation and soil moisture management in steppe grasslands.

An evaluation of soil nutrient status and balance in Meitan tea plantations

LIU Shu-jun, YAO Xin-zhuan, ZHAO De-gang, LÜ Li-tang

2020, 29(11):  33-45.  DOI: 10.11686/cyxb2020061

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This research investigated the soil nutrient status and balance in Meitan tea plantations. Six indicators were selected (pH, organic matter, total nitrogen, alkaline nitrogen, available phosphorus and available potassium) and data on these collected for six categories of tea plantation. The data were evaluated by principal component analysis. It was found that: 1) The soil pH of Meitan tea plantations ranged from 3.73 to 7.26, with an average value of 5.01. In 61.11% of the surveyed tea plantations, the soil tests satisfied the standard set for high quality tea plantations. Hence, the soil pH of Meitan tea plantations was generally suitable, although soil in 16.67% of the tea plantations had an acidification trend. 2) The contents of organic matter, total nitrogen, alkaline nitrogen, available phosphorus and available potassium in Meitan tea plantations were in most cases rich, with average values of 22.84 g·kg^-1, 1.43 g·kg^-1, 124.50 mg·kg^-1, 44.16 mg·kg^-1 and 135.61 mg·kg^-1, respectively. For the same list of tests, soil in 61.11%, 70.37%, 61.11%, 55.56% and 59.26%, respectively, of the tea plantations met the standard for high quality tea plantations, but the status for individual nutrients differed between plantations. 3) The integrated fertility index (IFI) range for the surveyed Meitan tea plantations was 0.179-0.989, with an average value of 0.683. In 51.85% of the tea plantations soil was at level Ⅰ status, and in 31.48%, it was at level Ⅱ. Hence, the soil nutrient status is generally good. There were obvious differences in IFI between the different categories of tea plantations, with the ranking being: medium mountain yellow soil>hilly yellow soil>hilly calcareous soil>low mountain yellow soil>medium mountain calcareous soil>low mountain calcareous soil. 4) There was a very significant negative correlation between pH and organic matter, total nitrogen, and available phosphorus, and a significant negative correlation of pH with alkaline nitrogen. There was a significant (P<0.05) and a very significant (P<0.01) positive correlation between the nutrient indexes; i.e. the values for the various nutrients at any one test site were relatively close and homologous. Tea plantation values for soil pH were negatively correlated with IFI (P<0.01), and test values for other nutrients were positively correlated with IFI (P<0.01).

Effects of soil plastic mulching and fertilizer application on the water utilization and yield of Tartary buckwheat crops in a semiarid rain-fed area

FANG Yan-jie, ZHANG Xu-cheng, YU Xian-feng, HOU Hui-zhi, WANG Hong-li, MA Yi-fan, ZHANG Guo-ping, LEI Kang-ning

2020, 29(11):  46-56.  DOI: 10.11686/cyxb2020233

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This research investigated the effects of fertilizer application and soil-plastic mulching on soil water storage, periodic evapotranspiration (ET), plant development, yield and water use efficiency (WUE) of Tartary buckwheat crops grown in a semiarid rain-fed area, in order to identify cultivation techniques that enhance crop drought resistance and efficient resource utilization. A field experiment comprising three treatments was conducted from 2015 to 2017 at Dingxi Experimental Station of Gansu Academy of Agricultural Sciences. The three treatments were: traditional planting without fertilization application (TNF), whole field soil-plastic mulching without fertilization application (MNF), and whole field soil-plastic mulching with fertilization application (MF). The soil water content for the 0-300 cm soil depth, crop dry matter, leaf area index and yield of Tartary buckwheat were recorded. The soil water storage, periodic measurements of ET, harvest index, rainwater use efficiency (RUE) and water use efficiency (WUE) were calculated, to determine the effects of fertilizer application and soil plastic mulching and bunch seeding on water utilization and yield. It was found that MF increased soil water storage by 18.9-42.4 mm in the 0-140 cm soil layer during the seedling stage, and the ET in the pre-flowering period, as compared with TNF and MNF. Compared to TNF and MNF, respectively, MF increased the dry matter quality at maturity by an average of 96.3% and 3.7%, the leaf area index by 123.7% and 7.6%, the number of ears by 9.3% and 3.9%, the grain weight per plant by 139.2% and 12.1%, the grain plumpness by 14.5% and 4.4%, and reduced the ear height by 34.0% and 26.8%. Compared to TNF, MF significantly promoted the population-level statistics of Tartary buckwheat, with a yield increase of 33.6%-130.4%, a biomass increase of 62.8%-182.5%, an enhancement of WUE of 34.5%-106.4%, and these effects were more pronounced in dry seasons. Therefore, the cultivation practice comprising whole-field soil plastic mulching with fertilizer application improves the yield and WUE of Tartary buckwheat, can be recommended as a suitable planting mode for drought amelioration and yield increase of Tartary buckwheat in the semi-arid area of the northwest Loess Plateau.

Effect of drinking water temperature on production performance, blood biochemical parameters and rumen microstructure of fattening sheep in winter

ZHAO Juan-juan, ZHANG Wei-tao, GUO Wei-ting, SUN Xin-sheng, WANG Chao, ZHAO Shou-pei, CHE Da-lu, GAO Yu-hong

2020, 29(11):  57-66.  DOI: 10.11686/cyxb2019574

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The objective of this study was to evaluate the effects drinking water temperature on production performance, apparent digestibility of nutrients and blood biochemical parameters in fattening sheep in winter, and rumen structure was also observed using a microscope. Information on the ideal temperature of drinking water for fattening sheep might well lead to improved production efficiencies through mechanisms such as alleviation of cold stress. A flock of 135 healthy fattening sheep with similar weight were randomly assigned into three groups, with drinking water supplied at 2, 8 and 20 ℃ for the respective groups. Each treatment contained three pens (15 sheep·pen^-1). The experiment duration was 28 days. It was found that: 1) Compared with the 2 ℃ group, the 8 and 20 ℃ groups had increased daily water consumption (P<0.05). Although there was no statistical difference (P>0.05) in daily feed intake and daily gain between any of the groups, the feed conversion efficiency in the 20 ℃ group was higher than that in 2 ℃ group (P<0.05). 2) There was a difference (P<0.01) between groups in the serum glucose (GLU) contents. The GLU content in 8 and 20 ℃ groups was 1.39 and 1.14 times higher, respectively, than that in the 2 ℃ group, and the 20 ℃ group had decreased the serum cholesterol (P<0.05). The serum urea nitrogen, total protein and serum hormone (triiodothyronine, thyroxine and growth hormone) contents did not differ between groups (P>0.05). 3) The length, width, and surface area of rumen papilla in the 20 ℃ group were increased (P<0.05) compared with the 2 and 8 ℃ groups. The group drinking water at 20 ℃ had reduced rumen muscle layer thickness (P<0.05) and increased submucosal thickness (P<0.05). However, there was no difference (P>0.05) in thickness of mucosal epithelium among groups. 4) With increase in drinking water temperature, the apparent digestibility of crude fat, neutral detergent fiber (NDF) and phosphorus (P) increased (P<0.05), especially P and NDF, while the digestibility of other nutrients did not differ between treatment groups (P>0.05). The results showed that drinking warm water improved the feed conversion efficiency of fattening sheep. In addition, drinking warm water may improve rumen function and promote the digestion and absorption of nutrients.

Sublethal effects of pyridaben on the development and reproduction of Petrobia harti

HE Heng-guo

2020, 29(11):  67-73.  DOI: 10.11686/cyxb2020128

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Petrobia harti is a very serious worldwide pest mite harming Oxalis corymbosa, and pyridaben as a broad-spectrum, contact-killing acaricide that is highly effective against P. harti. To clarify the sublethal effects of pyridaben on P. harti and provide data for developing comprehensive control strategies for this mite with minimal usage of pyridaben, the toxicity of pyridaben against P. harti was determined by a leaf impregnation method. The sublethal doses used were determined by a regression equation of P. harti death rate on pyridaben concentration, in order to identify concentrations predicted to be lethal to 10% or 20% of a test population of mites (LC₁₀ and LC₂₀, respectively). The effects of the LC₁₀ and LC₂₀ sublethal pyridaben doses on the development, fertility and life-history parameters of P. harti were evaluated by establishing a life table. It was found that the fecundity of P. harti was significantly decreased after treatment with the sublethal doses of pyridaben (P<0.05) with the number of eggs laid per female reduced, respectively, by 53.37% and 55.46% in the F₀ generation and 41.34% and 45.24% in the F₁ generation in the LC₁₀ and LC₂₀ treatments, compared to the controls. Similarly, the oviposition duration was significantly shortened, respectively, by 3.11 and 4.75 days in F₀ generation and 3.47 and 2.81 days in the F₁ generation. The average adult longevity was also significantly shortened, respectively, by 1.45 and 2.04 days in the F₀ generation and 3.24 and 4.00 days in the F₁ generation. Compared to the control, after treatment with sublethal pyridaben doses, the net reproductive rate (R₀), intrinsic rate of increase (r_m) and finite rate of increase (λ) of P. harti were all significantly decreased in the LC₁₀ and LC₂₀ treatments (the R₀ from 28.54 to 16.91 and 15.48; the r_m from 0.1650 to 0.1276 and 0.1249; the λ from 1.17941 to 1.1435 and 1.1330; P<0.05), while the mean generation time (T) and the population doubling time (Dt) were both significantly prolonged (the T from 20.31 to 22.17 and 21.94 days; the Dt from 4.20 to 5.43 and 5.55 days, respectively; P<0.05). The results indicated that the sublethal doses of pyridaben at LC₁₀ and LC₂₀ decreased the development rate and fecundity of laboratory populations of P. harti.

Effects of three fungicides on the activities of protective enzymes and detoxifying enzymes in Apis mellifera

DUAN Xin-le, XIONG Man-qiong, LIU Wen-bin, ZHAO Bi-an, HUANG Shao-kang, LI Jiang-hong

2020, 29(11):  74-82.  DOI: 10.11686/cyxb2020148

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This research aimed to clarify the effects of fungicides applied in Medicago sativa production on the safety of an important pollinating insect, the honeybee (Apis mellifera), One-day-old adult honeybees were fed a diet containing dimetachlone, prochloraz, iprodione, at a range of concentrations (diluted with water 1:500, 1:1000, 1:1500, 1:2000 and 1:2500) or no fungicide (Control). Subsequently, the activities of three protective enzymes, superoxide dismutase (SOD), guaiacol peroxidase (POD), catalase (CAT), and three detoxifying enzymes, carboxylesterase (CarE), glutathione S-transferase (GST), cytochrome P450 (P450) in the honeybees were measured. It was found that different concentrations of all the three fungicides could induce increased activities of SOD and POD in the honeybees. In particular, treatment with prochloraz solution at the 1:1500 dilution (0.17 mg·L^-1) induced a 1.82-fold SOD activity and a 5.40-fold POD activity compared to the Control treatment. All three fungicides showed low concentration induction and high concentration inhibition of CAT, CarE and GST activities, and showed inhibition (prochloraz) or induction (dimetachlone and iprodione) of P450 activity. With extended treatment time, the 1:1000 dilution of all three fungicides (0.40, 0.25 and 0.50 mg·L^-1 of dimetachlone, prochloraz, and iprodione, respectively) showed an overall induction effect on the activities of the three protective enzymes in Italian bees, but a variable effect on the activities of detoxifying enzymes. Specifically, dimetachlone initially increased the activities of the three protective enzymes and then inhibited activity after 6 h; iprodione induced P450 activity at all times, but inhibited the activities of CarE and GST in the first 12 h, then induced their activity thereafter; prochloraz elicited a gradual decrease in P450 activity with time, but initially induced then later inhibited the activities of CarE and GST. The results indicate that Italian bees can reduce the negative effects of fungicides by regulating the activities of protective and detoxifying enzymes in their bodies, but the fungicides have an impact on the normal physiology and metabolism of bees, even so. Therefore, care should be taken when applying fungicides to protect bees and ensure their safety while pollinating agricultural crops.

Effect of lactic acid bacteria preparations on microbial population counts and silage quality in maize silage during fermentation and on aerobic exposure

WAN Xue-rui, DOU Si-yuan, LI Yu, HE Yi-qun, WANG Chuan, ZHANG Xiao-li, LEI Zhao-min

2020, 29(11):  83-90.  DOI: 10.11686/cyxb2019581

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This research investigated the effect of lactic acid bacteria (LAB) preparations on microbial population counts and silage quality of whole maize silage during fermentation and on aerobic exposure after fermentation. The aim was to test if inoculation with LAB preparations can improve silage quality and aerobic stability. Three different LAB preparations [Homofermentative (Homo), Heterofermentative (Hetero), combined Homo+Hetero] were added to whole maize during ensiling. A blank control treatment was also included. Data on microbial population count, fermentation quality and nutrient contents of silage were evaluated during fermentation at 3, 7, 15, and 30 days after ensiling, and on completion of fermentation, after 1, 3, 7, 15 and 30 days of aerobic exposure. It was found that both during maize silage fermentation and during subsequent aerobic exposure, the LAB population counts, the lactic and acetic acid concentrations were significantly increased compared with the blank control treatment, while the numbers of aerobic bacteria, yeasts and molds and crude protein loss were significantly reduced and the concentrations of NH₃-N and the pH were obviously reduced by addition of the three LAB preparations. These results indicate that LAB preparations improve maize silage nutritional quality and inhibit secondary fermentation after aerobic exposure. The combination treatment Homo+Hetero performed best, and Homo performed better than Hetero.

Effects of fertilization and legume-grass ratio on forage yield and NPK utilization efficiency

ZHANG Yong-liang, YU Tie-feng, HAO Feng, GAO Kai

2020, 29(11):  91-101.  DOI: 10.11686/cyxb2020009

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The amounts of nitrogen, phosphorus and potassium applied and the ratio of legume to grass in mixed sowings are key factors affecting the yield and fertilizer use efficiency of mixed grassland. The forage yield and utilization efficiency of nitrogen, phosphorus and potassium under different application ratios of those nutrients were analyzed to provide a scientific basis to manage cultivation of mixed grass-legume grassland for high yield. Field experiments were conducted on mixed swards of alfalfa and smooth brome. The experiment comprised two row configurations (legume:grass inter-row pattern 2:2 and 1:2) and seven nitrogen, phosphorus and potassium combinations: N₂₈₀P₁₅₀K₀ (A₁), N₃₅₀P₁₀₀K₃₆₀ (A₂), N₁₄₀P₃₀₀K₃₀₀(A₃), N₄₂₀P₂₅₀K₁₂₀ (A₄), N₇₀P₅₀K₆₀ (A₅), N₂₁₀P₀K₂₄₀ (A₆) and N₀P₂₀₀K₁₈₀ (A₇), where subscripts after each element indicate the application rate as kg·ha^-1 N, P₂O₅, and K₂O, respectively. The highest value for annual total yield of mixed legume-grass forage (11.68 t DM·ha^-1) occurred in the A₂ treatment, and yield in this treatment was significantly higher than in other treatments (P<0.01). Alfalfa yield in the A₂ treatment was 8.60 t DM·ha^-1, and it was significantly higher than A₁, A₅, A₆ and A₇ treatments (P<0.01). Grass yield in the A₁ treatment was 3.80 t DM·ha^-1, and it was significantly higher than in other treatments (P<0.01). Yields of grass and grass-legume forage were lowest in the zero nitrogen treatment, A₇. The combined grass-legume yield was significantly related to the rate of N fertilizer. Both combined grass-legume yield and alfalfa yield displayed a N×K interaction (P<0.05). The NPK partial productivity, and uptake efficiency of grass, alfalfa and grass-legume forage all showed a downward trend with increase in NPK level, and the A₅ treatment was significantly superior to other treatments (P<0.01). The nitrogen utilization efficiency of alfalfa decreased significantly in the zero potassium (A₁) and low potassium (A₅) treatments, and the potassium utilization efficiency of grass, alfalfa and grass-legume forage decreased significantly in the zero phosphorus (A₆) and high phosphorus (A₃) treatments. The annual total yield of alfalfa and legume-grass forage in the 2:2 row configuration were significantly higher than in the 1:2 configuration, with extreme significance (P<0.01). Also, the partial productivity, uptake rate and uptake efficiency of alfalfa NPK, and partial productivity of NPK, N uptake rate and N uptake efficiency of grass-legume forage in the 2:2 row configuration mixture were significantly higher than in the 1:2 configuration with extreme significance (P<0.01), and the partial productivity, uptake amount and absorption efficiency of grass NPK were significantly lower in the 2:2 than in the 1:2 configuration with extreme significance (P<0.01). Considering forage yield and nutrient utilization efficiency, alfalfa-smooth brome mixed sowing in a 2:2 row configuration, and fertilizer application of 140 kg·ha^-1 N, 100 kg·ha^-1 P₂O₅, and 120 kg·ha^-1 K₂O can be recommended, based on these results.

Effects of tied-ridging rainwater harvesting on sediment yield, nutrient loss and alfalfa fodder yield on sloping land

ZHAO Xiao-le, WANG Qi, ZHANG Deng-kui, ZHOU Xu-jiao, WANG Xiao-yun, ZHAO Wu-cheng, CHEN Jin, LEI Jun

2020, 29(11):  102-117.  DOI: 10.11686/cyxb2020004

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In this research two experiments were conducted to investigate the effects of slope and cultivation system on soil erosion control. In Experiment 1, a completely random design was used to study the runoff efficiency and the rainfall threshold to produce runoff for ridges along different slopes (0°, 5° and 10°). In Experiment 2, a split-plot design with slope (5° and 10°) as the main plot factor and tillage method (traditional planting, open ridging and tied-ridging) as the split-plot treatment was adopted to study the effect of tied-ridging rainwater harvesting on soil moisture, runoff, sediment yield, nutrient loss, alfalfa fodder yield and water use efficiency (WUE). The mean runoff efficiencies for ridges along slopes of 0°, 5° and 10° were 88.2%, 91.1% and 92.7%, respectively. The threshold precipitation to produce runoff for the respective treatments was 1.55, 1.33 and 1.00 mm, respectively. Compared with traditional planting, the decreases in runoff, runoff efficiency, sediment yield, total nitrogen loss, total phosphorus loss and organic matter loss for open ridging were 62.3%-67.9%, 51.0%-54.5%, 95.6%-96.4%, 95.3%-96.2%, 95.3%-96.1% and 94.1%-95.6%, respectively, whereas the corresponding decreases for tied-ridging were 76.4%-79.9%, 67.8%-68.2%, 98.4%, 98.1%-98.2%, 98.2% and 97.8%-97.9%, respectively. The open ridging and tied-ridging increased shallow-layer (0-60 cm) soil moisture. The increase in alfalfa forage yield and WUE for open ridging were 40.3%-50.4% and 4.4-11.5 kg·ha^-1·mm^-1, respectively. The corresponding increases for tied-ridging were 16.0%-18.7% and 2.0-5.3 kg·ha^-1·mm^-1. The runoff, runoff efficiency, sediment yield, total nitrogen loss, total phosphorus loss and organic matter loss for the 10° slope were 1.44, 1.40, 2.34, 2.24, 2.39 and 1.97 times greater than those for the 5° slope. Lastly, average soil water storage, alfalfa fodder yield and WUE for the 5° slope were 1.05, 1.28, and 1.41 times greater than those for the 10° slope. Tied-ridging rainwater harvesting was particularly beneficial for reducing runoff, sediment yield and nutrient loss. Open-ridging was offered particular effects on increase of alfalfa fodder yield and WUE.

Effects of rooting media amendments on seed germination and seedling growth of four bioenergy grass species grown on electrolytic manganese residue

LUO Yang, LIU Fang, REN Jun, ZHU Jian

2020, 29(11):  118-128.  DOI: 10.11686/cyxb2020005

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This research investigated seed germination and seedling growth of four species of bioenergy grass (Pennisetum americanum×Pennisetum purpureum, Pennisetum purpureum, Pennisetum hydridum and Sorghum sudanense), grown on electrolytic manganese residue (control) or electrolytic manganese residue after adding one of three amendments (5% diatomite, 5% charcoal or 2.5% charcoal+2.5% diatomite). Germination percentage for the four bioenergy grasses ranked: P. purpureum>P. americanum×P. purpureum>S. sudanense>P. hydridum. The three amendments all significantly improved the germination percentage, germination energy and germination index of P. hydridum, and for the other three grasses the germination energy and germination index in the mixed amendment treatment of diatomite and charcoal were also significantly higher than those of the control group (P<0.05). Compared with the control group, in the amendment treatments, the fresh weights of P. americanum×P. purpureum, P. purpureum, P. hydridum and S. sudanense were increased by 36.54%, 7.69%, 35.71% and 23.88%, respectively. Amendment application also enhanced chlorophyll content and the activities of antioxidant enzymes (superoxide dismutase, peroxidase, catalase), while the malondialdehyde content of leaves was decreased. Based on the germination, growth and physiological parameters, for the tested bioenergy grasses grown on the electrolytic manganese residue, P. purpureum with 2.5% charcoal and 2.5% diatomite amendment performed best, followed by P. americanum×P. purpureum with 5% diatomite amendment.

Effects of drought and salt stress on seed germination characteristics of Halogeton glomeratus

HE Jian-jun, YAO Li-rong, WANG Jun-cheng, BIAN Xiu-xiu, SI Er-jing, YANG Ke, WANG Hua-jun, MA Xiao-le, LI Bao-chun, SHANG Xun-wu, MENG Ya-xiong

2020, 29(11):  129-140.  DOI: 10.11686/cyxb2020008

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To explore the effects of drought and salt stress on germination characteristics of halophytes, this study simulated drought stress with different concentrations of PEG-6000 and four sodium salts (NaCl, Na₂SO₄, NaHCO₃, Na₂CO₃) to evaluate the effects of those treatments on the seed germination characteristics of Halogeton glomeratus. It was found the germination percentage and germination energy decreased with increasing PEG-6000 concentration, while the seedling fresh weight, dry weight, plant height and root activity initially increased and then decreased at higher PEG-6000 concentration. Cluster analysis and principal component analysis showed that the different PEG-6000 concentrations could be divided into two groups with 6% PEG-6000 as the point of separation. Fresh weight appeared to be an important parameter. In addition, germination percentage germination energy, seedling fresh weight, dry weight, plant height and root activity declined with increase in concentration of the four sodium salts. This indicated that salt stress inhibited seed germination and seedling growth, with the effects of the four tested sodium salts ranked: Na₂CO₃>NaHCO₃>NaCl>Na₂SO₄. Cluster analysis and principal component analysis showed that the sodium salt concentrations were divided into two groups with the separation points falling at 50.00 mmol·L^-1 NaHCO₃, 62.50 mmol·L^-1 Na₂SO₄, 25.00 mmol·L^-1 Na₂CO₃ and 100.00 mmol·L^-1 NaCl. Among the plant traits evaluated as indicators of H. glomeratus stress tolerance in the germination stage, the germination index was the key indicator of NaHCO₃ and Na₂SO₄ stress, root activity emerged as the primary indicator of Na₂CO₃ stress and dry weight was the major indicator of NaCl stress in H. glomeratus.

Effects of nitrogen application rate on chlorophyll fluorescence characteristics and dry matter accumulation in switchgrass (Panicum virgatum) leaves

HE Hai-feng, YAN Cheng-hong, WU Na, LIU Ji-li, CHANG Wen-wen

2020, 29(11):  141-150.  DOI: 10.11686/cyxb2020007

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The effect of nitrogen fertilizer application rate on chlorophyll fluorescence characteristics and dry matter accumulation of switchgrass (Panicum virgatum) is of great significance for the improvement of light use efficiency and biomass yield of switchgrass in saline-alkali land. In this research, the patterns of variation in chlorophyll fluorescence parameters and dry matter accumulation in switchgrass were studied in field conditions with a range of nitrogen application treatments: no nitrogen (0 kg·ha^-1, N₀), low nitrogen application (60 kg·ha^-1, N₆₀), medium nitrogen application (120 kg·ha^-1, N₁₂₀) and high nitrogen application (240 kg·ha^-1, N₂₄₀), and the comprehensive effect of nitrogen application on chlorophyll fluorescence and dry matter accumulation in switchgrass was evaluated using a multivariate Grey relational analysis procedure. It was found that: under N₆₀, N₁₂₀ and N₂₄₀ treatments, the PSⅡ maximum photochemical efficiency (F_v/F_m), PSⅡ actual photochemical quantum efficiency (Φ_PSⅡ), potential activity (F_v/F_o), photochemical quenching (qP), non photochemical quenching (NPQ) and biomass yield were significantly higher, and the heat dissipation of quantum ratio (F_o/F_m) was significantly lower than for the N₀ treatment during the flowering and seed maturation stages of switchgrass development. During the flowering period of switchgrass, the PSⅡ potential activity (F_v/F_o) was initially increased and subsequently decreased across the range of nitrogen application rates, with a maximum observed value of 3.13 at N₁₂₀ (increased 16.26% compared with N₀). The effect of nitrogen application rate on dry matter accumulation differed between the crop growth stages. Dry matter accumulation was high during jointing and booting periods, reached its maximum at the seed filling stage, and decreased slightly thereafter. The maximum observed dry matter accumulation (378.13 g·hole^-1) occurred under the N₂₄₀ treatment during the post-flowering stage and was, respectively, 24.33%, 20.09% and 7.24% higher than that of the N₀, N₆₀ and N₁₂₀ treatments. Grey relational analysis showed that the association between the weighted correlation index and the ideal fertilization level was the highest under the N₂₄₀ treatment. In summary, the N₂₄₀ treatment in this study in the Yinbei saline-alkali area of Ningxia optimized the photochemical activity of PSⅡ and dry matter accumulation of switchgrass.

Historic experience from American public rangeland management policies

JIANG Xiao-qun, LIN Zhe-yan, SHI Yu, ZHAO Jin-ling, LI Ang

2020, 29(11):  151-164.  DOI: 10.11686/cyxb2019497

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After China has halted grassland degradation, it will be very important to rapidly improve current grassland management policies, especially those related to determining the grassland-livestock balance and payments for ecosystem services, and to achieve sustainable development goals (SDGs) for ecological conservation and improvement of herders’ well-being. Over the past 90 years, the United States has created and adjusted its public rangeland management systems and the US experience provides much valuable information for the reform of grassland management policies in China. The lessons from American public management suggest that multiple use and ecosystem service of grassland are two key concepts for sustainable management of grassland. These concepts should be firmly confirmed by social consensus, through the legal system, and in administrative management. Furthermore, public ownership rights form the legal premise for establishing multiple ecosystem services of grassland. The other stakeholder industries beyond animal husbandry provide the economic foundation to realize multifunctional grassland systems. Precise and responsive management by administrative agencies will guarantee the balance between livestock production and ecological conservation. The public participation of multiple stakeholders is the engine to drive forward the reform of grassland management systems. Meanwhile, the twists and turns of public rangeland management evolution in the United States suggest that common elements in the historic development of grassland management policy include: failure and adjustment of ecological policies, the flexibility to reconsider grazing prohibition and supervision intensity, and conflict and compromise between interest groups. All these elements may appear in China’s journey to achieve sustainable grassland management. In the next stage, optimization of grassland property rights, refinement of administrative management, coordination between herders and ecological conservation are the core tasks in the drive to achieve sustainable grassland management in China.

Discussion on grassland contract and management digitalization

WANG Jia-ting, QIAO Jiang, Naya, LIU Zhao-ming, ZHI Rong, LI Ping

2020, 29(11):  165-171.  DOI: 10.11686/cyxb2020302

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Grassland is an important natural resource and plays a key role in maintaining the stability of ecosystems on a regional scale. Confirmation of grassland contracts and property rights provides an institutional guarantee for grassland ecological protection and development, and is a specific measure to implement the relevant central government requirements. Previous research showed that the speed of determining grassland ownership varies from region to region due to unique local factors in the various grassland areas in China, and in some regions the progress towards determining the ownership of grasslands is relatively slow. Based on analysis of the historical background and current situations relating to contract and property confirmation for grasslands, we here summarize the basic work in grassland contract and property confirmation, including data collection, contract content, contract optimization, issuing of certificates of ownership, landholder training, information management and improvement of grassland dispute resolution mechanisms, et al. The thinking of the planning sector in grassland management including the main building blocks, basic function, workflow, key technologies, is put forward. Finally, consideration of and suggestions for the next stage of the work involving ‘three property rights separation’ are put forward. This research is of great significance to furthering the development of the contract and information management of grasslands in China.

Regulation mechanisms of rhizosphere nutrient cycling processes in grassland: A review

MA Yuan, ZHANG De-gang

2020, 29(11):  172-182.  DOI: 10.11686/cyxb2019571

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Understanding of the transformations and recycling processes of carbon, nitrogen and phosphorus in the soil rhizosphere is fundamental to solving the problems currently limiting the sustainable utilization of grassland agricultural ecosystems and improving grassland productivity. Rhizosphere processes in grassland can reflect the soil carbon, nitrogen and phosphorus nutrient turnover rates, affect the competition for and capture of nutrients by plants and soil microorganisms, and also determine the nutrient balance of each component in the rhizosphere microenvironment. Compared with crop systems, the coupling between carbon, nitrogen and phosphorus in grassland is stronger. Therefore, the structure and function of rhizosphere micro-ecosystems play an important role in maintaining nutrient transformation and circulation. Many literature reports indicate that the critical factor that regulates the rhizosphere microenvironment is the key substance of the plant and soil for material exchange and information transmission. The root exudates and rhizosphere exudates are also the key substances that mediate rhizosphere microorganisms and enzyme activities. When the grassland environment changes, the rhizosphere exudates, rhizosphere enzyme activities, and the composition and diversity of rhizosphere soil microorganisms will also change fundamentally, which will cause a change of supply and availability of soil nutrients, and in turn will affect grassland productivity and utilization efficiency of nutrients. So, further research on the regulation mechanism of nutrient cycling in grassland rhizosphere process is very important for revealing the distribution and utilization of nutrients and nutrient exchanges between grassland plants and microorganisms. This article reviews the mechanisms and interactions involving rhizosphere exudates, rhizosphere enzymes, and rhizosphere microorganisms involved in nutrient cycling, summarizes the mechanisms of grassland rhizosphere processes contributing to nutrient cycling and provides a perspective for consideration when formulating future research on rhizosphere microdomains in grassland ecosystems.

Increase in soil coarse sand content and decrease in soil nutrient levels accompany the transformation of perennial communities to annual communities in desert grassland

WANG Lei, SONG Nai-ping, CHEN Lin, YANG Xin-guo, WANG Xing

2020, 29(11):  183-189.  DOI: 10.11686/cyxb2020174

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This research studied the distribution of plant communities in response to soil environmental factors in desert steppe. We selected a soil habitat transition gradient from sierozem to sandy soil in Yanchi, Ningxia, China. Within, at the edge of, and outside of the sierozem habitat, vegetation characteristics and soil sampling were conducted using a line transect method. Based on the soil environmental factors and community species composition data, we quantitatively classified the plant communities using multivariate regression trees and redundancy analysis. Then we analyzed the differences between the different plant communities using principal component analysis. It was found that dominant species of the plant communities changed from Stipa breviflora+Cleistogenes squarrosa+Thermopsis lanceolate to Sophora alopecuroides+Pennisetum centrasiaticum and to Artemisia scoparia+Salsola collina across the soil gradient. Key soil factors associated with the shift of plant community species dominance included soil coarse sand, soil organic carbon and soil total phosphorus contents. Across the habitat gradient from sierozem to sandy soil, height, cover and biomass of the plant communities showed a statistically significant increase, community species abundance showed a significant decrease, and plant community diversity showed an increase and then a decrease. As soil texture became coarser and soil nutrient content decreased along the gradient, perennial plant communities were replaced by annual plant communities. Compared with the plant communities in the sierozem habitat, the proportion of perennial plant species, plant species diversity and biomass were low in sandy habitats.

Degradation characteristics of conventional and unconventional roughage in the rumen of dairy cows

LIU Xiang-sheng, DENG Bo-bo, WANG Kuo-peng, FENG Li-mei, ZHAO Guo-qi, LIN Miao

2020, 29(11):  190-197.  DOI: 10.11686/cyxb2019567

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The purpose of this study was to evaluate the rumen degradation characteristics of conventional roughage (corncob, soybean pod shell) and unconventional roughage (corn silage, alfalfa hay) for dairy cows. Three Holstein cows with permanent ruminal cannulas were used to evaluate the ruminal degradability of dry matter (DM), crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF) using the nylon-bag technique. It was found that: 1) The CP content in alfalfa hay (17.55%) was significantly higher than that in soybean pod shell (11.10%; P<0.05). The CP content in corncob (2.97%) was significantly lower than that in corn silage (8.41%; P<0.05). The NDF and ADF content in corncob (79.98% and 43.35%, respectively) were significantly higher than in the other three feedstuffs (P<0.05). 2) The DM effective degradability of alfalfa hay was the highest (P<0.05) among the tested feedstuffs, which ranked: alfalfa hay>soybean pod shell>corn silage>corncob. The CP effective degradability of soybean pod shell was significantly higher than the other three feedstuffs (P<0.05), which ranked: soybean pod shell>alfalfa hay>corn silage>corncob. The NDF effective degradability of alfalfa hay was significantly higher than soybean pod shell (P<0.05); there was no significant difference in NDF digestibility between corn silage and soybean pod shell (P<0.05). The ADF effective degradability of corncob was the highest (P<0.05) among the tested feedstuffs; there was no significant difference in ADF effective degradability between alfalfa hay, corn silage and soybean pod shell. In conclusion, corncob and soybean pod shell can be used as unconventional forage resources.

Effects of re-watering after drought on leaf photosynthetic light response characteristics of sugar beet

LI Si-zhong, ZHANG Li-ming, GAO Wei-shi, BAI Xiao-shan, LIU Jun, DONG Xin-jiu, YANG Hong-ze, SHA Hong, GAO Yan

2020, 29(11):  198-204.  DOI: 10.11686/cyxb2020011

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This research explored the physiological leaf response mechanisms of sugar beet to re-watering after drought with a focus on photosynthetic physiological traits and photo-responsive parameters. Two cultivars with different drought resistance, ‘XJT9907’ (a drought sensitive type) and ‘XJT9916’ (a drought tolerant type) were studied. A controlled water deficit was imposed on plants in the leafy growth stage, whereby soil moisture content was allowed to fall to 45%-50% of field water holding capacity for 7 days, then irrigation water was added to raise soil moisture to 70%-75% of the field water holding capacity for 48 hours. At this point, the photosynthetic physiological parameters of leaves were determined, and nonlinear regression used to fit sigmoid curves for the relationship between net photosynthetic rate of leaves and light intensity. It was found that drought stress during the leafy growth stage of sugar beet development significantly reduced the SPAD value, net photosynthetic rate (P_n), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), and transpiration rate (T_r) of both sugar beet varieties. After re-watering, the SPAD value, net photosynthetic rate (P_n), stomatal conductance (G_s), intercellular CO₂ concentration (C_i) and transpiration rate (T_r) of sugar beet leaves under drought stress treatments all improved. The values of physiological parameters for drought tolerant XJT9916 were significantly higher than those of drought sensitive XJT9907, although none of the values exceeded those of plants with a normal level of water supply, indicating a degree of compensation effect. After the re-watering treatment, the maximum net photosynthetic rates (P_nmax) of XJT9916 and XJT9907 varieties were, respectively, 6.2% and 17.1% lower than the control, and the apparent quantum efficiency (AQY) was, respectively, 6.5% and 12.2% lower than the control. Similarly, comparing drought tolerant and drought sensitive varieties to control plants. respiration rates (Rd) were, respectively, 19.1% and 14.9% lower than the control, light saturation points (LSP) were 19.6% and 14.1% lower than the control, while the light compensation points (LCP) were, respectively, 15.4% and 17.6% (P<0.05) higher than the control. For the drought sensitive variety, the light energy utilization interval was comparatively narrow, and the light energy utilization efficiency was reduced. Taken together, the results show that when the soil moisture content is 45%-50% of the field water holding capacity during the sugar beet leafy growth period, the photosynthetic potential of sugar beet leaves is not realized, the photosynthetic capacity of the leaves is weakened and cannot be restored to normal levels after re-watering. The drought-tolerant sugar beet variety XJT9916 has strong photosynthetic recovery ability in the context of re-watering after drought.