休闲期覆膜与施氮量对旱地小麦水氮利用效率和籽粒产量的影响

为探寻旱地小麦休闲期覆盖下的适宜施氮量,在旱地小麦休闲期覆盖与不覆盖条件下,分别设置75、150和225kg·hm-2三个施氮量,分析了休闲期覆盖配施氮肥对旱地小麦水氮利用效率和籽粒产量的影响。结果表明,休闲期覆盖显著提高播种至孕穗期0~300cm土壤蓄水量,其中播种期土壤水分增加70~81mm,其蓄水保墒效果可延续至孕穗期,进而提高了小麦产量和水分利用效率。休闲期覆盖促进了小麦植株对氮素的吸收和积累,增加了植株花前氮素转运量、花后氮素积累量以及籽粒氮素积累量,提高了氮素收获指数和氮素生产效率。休闲期覆盖配施氮素150kg·hm-2时,蓄水、增产和水分高效利用、氮素积累与转运的效果最好。     

黄土旱塬区麦田休闲期降水与土壤贮水的变化特征

为提高休闲期降水资源利用效率和确保区域粮食安全,利用1981—2020年陇东黄土高原旱作麦田定位土壤水分和气象观测资料,分析了冬小麦田休闲期间降水与土壤水分的变化特征及其影响因素。结果表明:(1)近40年陇东黄土高原休闲期降水以14 mm/10 a的速率增加,降雨总日数和小雨日数呈减少趋势,中雨、大雨日数呈弱增加趋势;(2)近40年休闲期1 m土层平均以9.5 mm/10 d的速率充水,贮水量平均增加97 mm,21世纪以来贮水量增加明显;(3)休闲期降水与1 m土层贮水增量符合二次函数关系,1 m土层开始贮存水分的降水阈值为175 mm,贮水增量与中、大雨总日数相关性最高,前期降水主要以土壤蒸发消耗为主,后期降水则大部贮存于土壤中;(4)休闲期1 m土层平均贮水效率为0.27,贮水效率随着麦收时的土壤墒情增加而线性递减,当麦收时1 m土层贮水量小于田间持水量的45%～48%时,贮水效率较高,1 m土层水分得到充分补充的降水阈值为388 mm。该研究成果揭示了近40年陇东黄土高原休闲期降水和土壤贮水的转化规律,同时为指导区域水资源高效利用提供科学依据。     

Plant Diversity and Vegetation Structure in Encroached and Non-encroached Areas of Borana Rangelands： The Case of Hallona and Medhacho Pastoralist Associations

The Borana rangelands are important areas of cattle production in Ethiopia. However, these rangelands are threatened by the increasing changes in the natural vegetation from grass and forbs dominated into unpalatable bushy woody vegetation resulting in the loss of some of the highly desirable grass species. This study was conducted to assess the impacts of bush encroachment on the biodiversity, structure and cover of the native vegetation in bush encroached and non-encroached sites. Vegetation data were collected from both sites by laying quadrate plots along transects using a systematic sampling method. According to the results, higher number of species was recorded in the non-encroached sites than that in the encroached sites. The diversity indices for the non-encroached and the encroached sites were 3.16 and 2.67, respectively. The abundance and cover analysis indicated that there was high density and cover of herbaceous species in the non-encroached site. There was a significantly higher density of woody species cover in the encroached site. Generally, the bush encroachment in the Borana rangelands has hampered the diversity of the native vegetation, particularly the grasses and forbs and reduced the ground cover, exposing large parts of the rangelands for soil erosion and other degradation process.     

休闲期深翻覆盖配施氮磷肥对旱地小麦群体动态、叶面积的影响及其与产量的相关性

采用大田试验方法,研究了休闲期深翻覆盖配施氮磷肥对旱地小麦群体动态、叶面积的变化及其与产量相关性的影响。结果表明,氮磷比为1∶0.5和1∶0.75时,增加施氮量可提高各生育期群体茎数、单株叶面积及成穗率,可显著提高可育小穗数、干物质量,降低不可育小穗数,从而提高穗数、穗粒数及产量;施氮量为150 kg/hm2时,增加施磷量可提高各生育期群体茎数、单株叶面积及成穗率,可显著提高可育小穗数、干物质量,可提高产量及其构成因素,其中,氮磷比为1∶1较1∶0.5提高成穗率13.10%,从而提高穗数22.7%,提高穗粒数3.79%,提高产量18.92%;施氮量为180 kg/hm2时,各生育期群体茎数、单株叶面积、成穗率、穗长、可育小穗数、不可育小穗数、干物质量以氮磷比为1∶0.75最高,1∶1居中,1∶0.5最低,其中,氮磷比为1∶0.75较1∶0.5提高成穗率11.43%,提高穗数19.35%,提高穗粒数4.95%,提高产量17.31%;施氮量为180 kg/hm2时,氮磷比为1∶0.75对各生育期群体茎数、叶面积、成熟期农艺性状、产量及其构成因素的影响较施氮量为150 kg/hm2、氮磷比为1∶1时效果更好。相关分析表明,各生育期群体茎数与穗数、穗粒数密切相关,且与穗数关系更密切;生育中后期单株叶面积与穗数、穗粒数相关较密切,且与穗数关系更密切。总之,休闲期深翻覆盖配施氮肥180 kg/hm2、氮磷比为1∶0.75时更有利于促进群体有效分蘖,提高成穗率;有利于提高叶面积,从而提高干物质量;有利于提高穗数、穗粒数,最终提高产量。     

Microbial dynamics and natural remediation patterns of Fusarium‐infested watermelon soil under 3‐yr of continuous fallow condition

Long‐term monoculture of watermelon results in inhibited growth and decreased crop yields, possibly because of imbalance in microbial ecology caused by accumulation of the pathogen in soil. This results in serious problems in the economics of watermelon production. We investigated the build‐up of Fusarium in soil under watermelon cultivation and changes over 3 yr of fallow in a microcosm. We focused on changes in the microbial community of Fusarium‐infected soil, including the diversity of the microfloral species composition, and species abundance. Long‐term monoculture of watermelon leads to changes in microbial diversity and community structure. The microbes most readily cultured from infested soil were suppressed by watermelon wilt pathogen Fusarium oxysporum f. sp. niveum (FON). Of 52 isolated and identified culturable microbes, 83.3% of bacteria, 85.7% of actinomycetes, 31.6% of fungi and 20.0% of Fusarium sp. were inhibited by FON on bioassay plates. Prior to fallowing, infested soil was a transformed ‘fungus‐type’ soil. After 3 yr of fallow, the infested soil had remediated naturally, and soil microbial diversity recovered considerably. Abundance of dominant bacterial populations was increased by 118–177%, actinomycetes, fungi and FON were decreased by 23–32, 33–37 and 50%, respectively. The ratio of bacteria: actnomycetes: fungus: Fusarium sp. in infested soil changed from 24 000:100:4:1 prior to fallow to 57 000:100:3.5:1 after fallowing, nearer to the 560 000:400:8:1 ratio of healthy soil not used for watermelon cultivation. This suggests the ‘fungus‐type’ soil was converting to ‘bacteria‐type’ soil and that disrupted microbial communities in infested soil were restored during fallow.     

对退耕还林工程中种草的探讨

分析种草在退耕还林工程中的重要地位和作用 ,提出退耕种草的草种选择和种植模式 ,并探讨发展草产业的途径和方向     

Assessing landscapes: a case study of tree and shrub diversity in the seasonally dry tropical forests of Oaxaca, Mexico and southern Honduras

Tropical dry forests, with their distinct and economically important diversity, are acknowledged conservation priorities because of alarming rates of forest conversion. Whilst it is realised that terrestrial conservation requires an understanding of landscape level patterns of diversity, forests are rarely assessed accordingly. Here we demonstrate that, in the case of the seasonally dry tropical forests of the Pacific watershed of Mesoamerica, landscape level assessment of woody diversity can inform decision making relevant to both between-landscape and within-landscape prioritisation. We report floristic surveys of dry forest landscapes in Oaxaca, Mexico and southern Honduras. It is noted that these forests are floristically similar to other seasonally dry tropical forests in the neotropics. By calculation of Genetic Heat Indices, a relative measure of the concentration of restricted range species in a sample, we determine that the conservation of the tree diversity of the coastal lowlands of Oaxaca should be prioritised over that of southern Honduras. The current conservation status of forested areas in Oaxaca is briefly described. We suggest that the greater degree of anthropogenic disturbance in southern Honduras may explain the relative lack of restricted range species there. We argue that some forest fallows can act as analogues of mature forest and therefore landscape elements other than mature forest need to be included in forest conservation assessments. We conclude that diversity sampling of any forest type should not be limited to mature forests, but extended to other elements of forested landscapes.     

长期施肥对红壤双季稻冬闲田春季杂草群落的影响

利用始于1982年的红壤双季稻田长期施肥定位试验,于2012年采用田间调查法研究了在无机肥(化肥NPK)与有机肥(M)氮磷钾养分等量条件下,长期施用有机肥、无机化肥和有机肥无机肥配施模式下红壤双季稻冬闲田春季杂草生物量及群落密度和群落多样性的变化。结果表明:有机肥无机肥配施改变了优势杂草种类,增加了杂草总密度和总生物量。化肥氮钾配施有机肥(NKM)处理的杂草种类数量最多,化肥氮磷配施有机肥(NPM)处理的最少。施肥处理中,M处理的杂草群落多样性指数、均匀度指数和优势度指数均最高,分别为1.118 6、0.732 3和0.629 7;其杂草总密度最低,为297.0株?0.25m?2。NPK处理的杂草总生物量最低,为58.0 g?0.25m?2。NPM处理的杂草群落多样性指数值、均匀度及优势度指数值均显著低于其他处理;其杂草总密度和杂草总生物量均最高,分别为539.7株?0.25m?2和109.5 g?0.25m?2;其优势杂草日本看麦娘的密度为428.0株?0.25m?2,相对密度为79.31%,明显高于其他处理优势杂草的密度和相对密度。春季杂草总干物质量与土壤碱解氮正相关(相关系数为0.703),与土壤p H负相关(相关系数为0.697),相关性不显著;与土壤有效磷显著正相关(相关系数为0.758*)。长期不同施肥模式下红壤稻田磷素是导致田间春季杂草群落特征变化的主要因素,通过改变土壤有效磷和碱解氮含量及土壤p H,能有效调控红壤双季稻冬闲田春季杂草生物量及群落密度和生物多样性。     

长江中游栓皮栎林水文生态效益研究

1998～ 1999年实测了河南境内长江中游栓皮栎林的林外降水、林内降水、树干径流以及下层植被和枯落物对降水的影响 ,并建立了相关的计算模型。结果表明 :观测期内栓皮栎林冠层能截留降水 2 0 .77% ,并将 4.85 %的降水转化为树干径流 ,枯落物的最大持水量为 13.40 t/ hm2 ,林外降水和林内降水、树干径流之间为线性关系 ,而林冠截留符合灰色模型     

Effect of improved fallow on crop productivity, soil fertility and climate-forcing gas emissions in semi-arid conditions

The impacts of fallow on soil fertility, crop production and climate-forcing gas emissions were determined in two contrasting legumes, Gliricidia sepium and Acacia colei, in comparison with traditional unamended fallow and continuous cultivation systems. After 2 years, the amount of foliar material produced did not differ between the two improved fallow species; however, grain yield was significantly elevated by 55% in the first and second cropping season after G. sepium compared with traditional fallow. By contrast, relative to the unamended fallow, a drop in grain yield was observed in the first cropping season after A. colei, followed by no improvement in the second. G. sepium had higher foliar N, K and Mg, while A. colei had lower foliar N but higher lignin and polyphenols. In the third year after fallow improvement, a simulated rainfall experiment was performed on soils to compare efflux of N₂O and CO₂. Improved fallow effects on soil nutrient composition and microbial activity were demonstrated through elevated N₂O and CO₂ efflux from soils in G. sepium fallows compared with other treatments. N₂O emissions were around six times higher from this nitrogen-fixing soil treatment, evolving 69.9 ngN₂O–N g⁻¹soil h⁻¹ after a simulated rainfall event, compared with only 8.5 and 4.8 ngN₂O–N g⁻¹soil h⁻¹ from soil under traditional fallow and continuous cultivation, respectively. The findings indicate that selection of improved fallows for short-term fertility enhancement has implications for regional N₂O emissions for dry land regions.