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41.
针对我国南方地区冬闲田数量多、利用率低的现象,充分利用冬闲田种草养畜,不仅可以解决牲畜季节性青绿粗饲料缺乏问题,还能促进农民增收和农业可持续发展。一年生黑麦草由于适生范围广,鲜草产量高,营养丰富且柔嫩多汁,适口性好,家畜家禽喜欢采食,深受农户青睐,成为一种极具发展前途的越年生优质牧草,近年来在畜牧业生产中得到广泛应用。本文从一年生黑麦草生物性状、营养特性、冬闲田的丰产栽培技术、青贮技术以及在各类畜禽的饲喂研究角度进行综述,并指出今后的研究重点和方向。旨在为一年生黑麦草在畜牧业中的进一步推广应用提供参考。  相似文献   
42.
Microarthropods, such as soil mites (Acari) and springtails (Collembola), with body width between 0.08 mm and 0.5 mm play important roles in soil fertility maintenance through their regulatory activities in decomposition and nutrient turnover. Observations were made at IITA, Ibadan, southwestern Nigeria to evaluate the effects of natural regrowth of vegetation — mainly the shrub Chromolaena odorata — and three planted woody fallow species (Acacia leptocarpa, Senna siamea, and Leucaena leucocephala) on soil microarthropods in a degraded Alfisol. Populations of soil microarthropods were higher in the rainy season than the dry season, and populations were greater under natural fallow than for continuous cropping with maize (Zea mays) and cassava (Manihot esculenta). Populations of soil microarthropods were comparable under leucaena and natural fallow, but populations in the rainy season were 38% higher under senna than natural fallow and 36% higher under acacia than natural fallow. Regression analysis indicated that soil microarthropod population under fallow species was positively correlated with the lignin contents of leaf litter.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   
43.
Ecosystem fertility and fallow function in the humid and subhumid tropics   总被引:10,自引:4,他引:6  
The regeneration of natural vegetation (fallowing) is a traditional practice for restoring fertility of agricultural land in many parts in the tropics. As a result of increasing human population and insufficient fertilizer inputs, the ecosystem fertility functions of traditional fallows must now be improved upon via the use of managed fallows. Interactions between vegetation and soil determine nutrient losses and gains in crop—fallow systems and are influenced by fallow species, patterns and rates of biomass allocation, and crop and fallow management. Nutrient losses occur through offtake in crop harvests during the cropping phase and through leaching, runoff, and erosion in the cropping phase and the initial stage of fallows $#x2014; when nutrient availability exceeds nutrient demand by vegetation. Gains in nutrient stocks in later stages of fallow are generally more rapid on soils with high than low base status due to greater quantities of weatherable minerals and lack of constraints to N2 fixation, deep rooting, and retrieval of subsoil nutrients by fallow vegetation. On low base status soils (exchangeable Ca < 1 cmolc kg–1), N2 fixation and atmospheric inputs are likely to be the main sources of nutrient additions. On high base status soils limited by N, gains in N stocks by inputs from N2 fixation and retrieval of subsoil nitrate can occur relatively rapidly; hence short-term fallows can often improve crop performance. Large losses of Ca associated with soil organic matter (SOM) mineralization and soil acidification during cropping and fallow establishment, combined with chemical barriers to root penetration, suggest that long-duration fallows (> 5 yr) are needed for recovery of cation stocks and crop performance on low base status soils. On both soils, however, residual benefits of fallows on crop yields usually last less than three crops.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   
44.
Within different land‐use systems such as agriculture, forestry, and fallow, the different morphology and physiology of the plants, together with their specific management, lead to a system‐typical set of ecological conditions in the soil. The response of total, mobile, and easily available C and N fractions, microbial biomass, and enzyme activities involved in C and N cycling to different soil management was investigated in a sandy soil at a field study at Riesa, Northeastern Germany. The management systems included agricultural management (AM), succession fallow (SF), and forest management (FM). Samples of the mineral soil (0—5, 5—10, and 10—30 cm) were taken in spring 1999 and analyzed for their contents on organic C, total N, NH4+‐N and NO3‐N, KCl‐extractable organic C and N fractions (Corg(KCl) and Norg(KCl)), microbial biomass C and N, and activities of β‐glucosidase and L‐asparaginase. With the exception of Norg(KCl), all investigated C and N pools showed a clear relationship to the land‐use system that was most pronounced in the 0—5 cm profile increment. SF resulted in greater contents of readily available C (Corg(KCl)), NH4+‐N, microbial biomass C and N, and enzyme activities in the uppermost 5 cm of the soil compared to all other systems studied. These differences were significant at P ≤ 0.05 to P ≤ 0.001. Comparably high Cmic:Corg ratios of 2.4 to 3.9 % in the SF plot imply a faster C and N turnover than in AM and FM plots. Forest management led to 1.5‐ to 2‐fold larger organic C contents compared to SF and AM plots, respectively. High organic C contents were coupled with low microbial biomass C (78 μg g—1) and N contents (10.7 μg g—1), extremely low Cmic : Corg ratios (0.2—0.6 %) and low β‐glucosidase (81 μg PN g—1 h—1) and L‐asparaginase (7.3 μg NH4‐N g—1 2 h—1) activities. These results indicate a severe inhibition of mineralization processes in soils under locust stands. Under agricultural management, chemical and biological parameters expressed medium values with exception for NO3‐N contents which were significantly higher than in SF and FM plots (P ≤ 0.005) and increased with increasing soil depth. Nevertheless, the depth gradient found for all studied parameters was most pronounced in soils under SF. Microbial biomass C and N were correlated to β‐glucosidase and L‐asparaginase activity (r ≥ 0.63; P ≤ 0.001). Furthermore, microbial biomass and enzyme activities were related to the amounts of readily mineralizable organic C (i.e. Corg(KCl)) with r ≥ 0.41 (P ≤ 0.01), suggesting that (1) KCl‐extractable organic C compounds from field‐fresh prepared soils represent an important C source for soil microbial populations, and (2) that microbial biomass is an important source for enzymes in soil. The Norg(KCl) pool is not necessarily related to the size of microbial biomass C and N and enzyme activities in soil.<?show $6#>  相似文献   
45.
世界耕地休耕时空配置的实践及研究进展   总被引:4,自引:4,他引:0  
该文立足于探索中国耕地休耕时空配置的关键问题,沿着"典型国家及地区实践→理论成果提炼→关键问题探讨"的逻辑思路,从地理学、农学、土地科学和管理学等多学科视角,采用文献法、对比法、归纳法和实地调查法,对耕地休耕时空配置进行了研究,得到以下主要结论:1)典型国家及地区的耕地休耕时空配置主要有4种类型:目标导向型时空配置、执行方式导向型时空配置、多条件约束导向型时空配置和技术导向型时空配置。2)耕地休耕时空配置的内涵本质就是实现对休耕地"定位、定量、定时"的宏观调控,主要包括了休耕目标、休耕空间(休耕区域和休耕规模)布局和休耕时间(休耕时序和休耕时长)安排;耕地休耕时空配置过程为"休耕目标→约束条件→空间布局→时间安排",各个环节之间又相互联系,其中,约束条件主要包括粮食市场、粮食安全、生态安全、耕地质量和社会经济。3)中国耕地休耕时空配置需解决的2个关键问题是不同空间尺度的耕地休耕空间布局和不同区域的耕地休耕时间安排,而构建综合模型或评价指标体系和划分评价等级标准是解决这2个关键问题的难点和重点。  相似文献   
46.
针对西南干热河谷旱季休闲农田面积扩大的实际,选择旱季初和旱季末2个时段,研究24 h休闲农田温度与农田蒸发量的变化规律及协同关系。结果表明:休闲农田温度曲线和蒸发量累计曲线大致呈现波形函数曲线变化,随着土壤深度和农田覆盖物的增加,曲线依次向后推移,波幅也逐渐变小,表明农田覆盖物对土壤起到一定的稳温和保水作用,可明显降低农田土壤水分散失;休闲农田温度与农田蒸发量的协同函数均呈现正向协同关系,且协同系数普遍较大,随着土壤深度和地表覆盖物逐渐增加,协同关系逐渐减弱,而干旱却有利于协同关系加强,说明在气候干燥区,农田温度升高,农田蒸发量增大,温度与蒸发量的协同关系增强,农田温度仍然是农田蒸发的主要推动因素。故西南干热河谷地区要开发利用季节性休闲农田,就必须做好旱季农田土壤水分的保蓄,增加地表覆盖物,减少农田水分的无效蒸发,为休闲农田的开发利用奠定良好的水分基础。  相似文献   
47.
夏闲期种植不同绿肥作物对土壤养分及冬小麦产量的影响   总被引:4,自引:0,他引:4  
为探明种植绿肥作物对关中土壤肥力及冬小麦产量的影响效果,在夏闲期种植光叶苕子(Vicia villosa Rothvar)、毛叶苕子(Vicia villosa Roth)、紫云英(Astragalus sinicus)和草木樨(Melilotus suaveolens Ledeb.)等四种绿肥作物,以免耕休闲为对照,分析了冬小麦主要生育时期的土壤速效养分动态变化及其产量效应。结果表明,夏闲期种植绿肥的土壤速效磷、速效钾和碱解氮都有不同程度的提高,增加量主要受绿肥的养分含量以及生物量影响。与对照相比,种植并翻压光叶苕子、毛叶苕子、紫云英和草木樨,均可显著提高冬小麦单位面积穗数、穗粒数和千粒重,冬小麦依次增产21.1%(P<0.05)、24.3%(P<0.05)、6.0%和11.6%。  相似文献   
48.
In Germany, sugar beet is often rotated with 2 years of cereal. Extensive fallow periods between cereal harvest and autumn primary tillage allow for a weed flora to develop. Broad‐leaved weeds could potentially be alternate hosts for the common nematode Heterodera schachtii, one of the most important pests of sugar beet. Between 2009 and 2012, annual weeds developing in cereal stubble fields during July to mid‐October in the season prior to sugar beet were surveyed, including known hosts of H. schachtii. Yearly weather patterns and agronomic practices possibly impacted weed species composition and weed population densities. During September, Chenopodium album, Cirsium arvense, Convolvulus arvensis, Mercurialis annua, Polygonum spp., Solanum nigrum and Sonchus spp. occurred at the highest frequencies. Weed hosts of H. schachtii were present, but densities, frequencies and uniformity were limited. In 2010 and 2011, staining for nematodes in roots revealed juvenile penetration of some weeds but few adult stages. No indication of nematode reproduction of H. schachtii was found on these weed hosts. A fairly stable weed flora was detected on stubble fields that could provide some carry over for weed species. An elevated risk for nematode population density build‐up on these weeds was not found and management of these weeds at the observed densities during the stubble period for nematological reasons appeared unnecessary.  相似文献   
49.
为给旱地夏闲期管理提供参考依据,采用大田试验,研究了夏闲期施肥与覆盖处理对旱地冬小麦土壤储水量、产量及水分利用效率的影响。结果表明,夏闲期施肥可明显提高播前0~100、100~200 cm土层储水量,增加了冬小麦穗数、籽粒产量和水分利用效率;不论施肥与否,地膜覆盖与纸覆盖均可提高播前底墒,增加小麦穗数和穗粒数,显著提高籽粒产量和水分利用效率,且地膜覆盖处理效果优于纸覆盖;施肥可增进覆盖的保水、增产及高效用水的作用。因此,旱地夏闲期可通过施肥与覆盖技术改善土壤水分状况,为旱地秋播作物高产创造条件。  相似文献   
50.
湖南冬闲田马铃薯氮吸收分配规律研究   总被引:1,自引:0,他引:1  
试验采用“3414”设计方案,分析冬闲田马铃薯在不同肥料水平下氮肥吸收分配规律。结果表明:马铃薯地上部全氮含量在全生育期间其动态变化呈现为苗期低,块茎形成期高,而在块茎成熟期缓陧下降的趋势,且在整个生育期内,氮素浓度的变化表现为地上部〉块茎;块茎中氮的含量均在块茎形成期最高,块茎成熟期下降。  相似文献   
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