调亏灌溉促进涌泉根灌枣树生长提高产量

调亏灌溉是作物通过主动调节自身营养达到节水和提高果实产量等目的。该文通过微灌枣树试验,研究了涌泉根灌下调亏灌溉对山地枣树生长与产量的影响。2013年分别在萌芽展叶期和开花坐果期进行轻度、中度和重度3个调亏水平调亏处理试验。结果表明:轻度和中度水分亏缺均对枣吊的生长起到抑制作用,能够有效减少新梢生长及夏季修剪量,而对枣树果实的生长起到了促进作用,达到增产的目的。轻度、中度和重度水分亏缺与充分灌溉相比,枣吊长度分别减少了7.2%、13.2%和19.7%(P0.05)。枣树坐果期,果实生长缓慢,轻度、中度、重度调亏以及充分灌溉果实生长量分别为果实最终体积的14.5%、14.1%、13.8%和13.5%。与充分灌溉相比,轻度调亏的枣树最终产量提高了22.1%(P0.05)。可见,调亏灌溉会较为显著的影响枣树的最终产量。适宜的水分亏缺对枣树果实生长与产量有促进作用,且提高了水分利用率。     

黄淮海平原盐碱土改良技术——以山东省鲁西北平原开发试区为例

山东省鲁西北平原开发试验区重盐碱荒地实施引淡水淋盐降低耕层土壤全盐量、增施有机肥减轻盐害、农田覆盖减少蒸发、种衣剂和“开大沟、留大背、浇大水,沟内集中施用有机肥、NP肥”植棉法等10项农业综合技术,使耕层土壤全盐量明显下降,土壤容重减小,土壤孔隙度增大,田间持水量增加,土壤保水保肥能力提高,林木覆盖率由开发前的4.5%提高到21.0%,粮食单产由治理前的6345kg/hm²增加到1.253万kg/hm²,粮食总产量由785万kg增加到1816万kg,人均收入由628元增加到1425元,经济、社会和生态效益显著。     

Digital soil mapping in Germany—a review

Digital soil mapping as a tool to generate spatial soil information provides solutions for the growing demand for high‐resolution soil maps worldwide. Even in highly developed countries like Germany, digital soil mapping becomes essential due to the decreasing, time‐consuming, and expensive field surveys which are no longer affordable by the soil surveys of the individual federal states. This article summarizes the present state of soil survey in Germany in terms of digitally available soil data, applied digital soil mapping, and research in the broader field of pedometrics and discusses future perspectives. Based on the geomorphologic conditions in Germany, relief is a major driving force in soil genesis. This is expressed by the digital–soil mapping research which highlights the great importance of digital terrain attributes in combination with information on parent material in soil prediction. An example of digital soil mapping using classification trees in Thuringia is given as an introduction in digital soil‐class mapping based on correlations to environmental covariates within the scope of the German classification system.     

Effects of potentially inhibiting substances on C and net N mineralization of a sandy soil—a case study

Recently, indirect evidence was obtained for inhibition of soil net N mineralization by sterols in soil organic matter, which could have been caused by their antioxidant or antimicrobial properties. The objective of this study was to test the effect of potential inhibitors (i.e., individual compounds with known antioxidant and/or antimicrobial properties) on soil microbial mineralization processes during incubation for 7 and 14 d. A sandy agricultural soil was amended with four substances: two phenolic acids differing in their antioxidant capacity (AOC) (acetovanillone with no AOC, ferulic acid with large AOC), Trolox, an analogue of vitamin E (large AOC), and β‐sitosterol (no AOC, but potential antimicrobial properties). The two compounds with large AOC (ferulic acid and Trolox) showed no significant inhibition of C and net N mineralization; and the Trolox amendment actually caused a significant increase in C and net N mineralization after 7 d of incubation. Acetovanillone with no measurable AOC caused a significant increase in C mineralization (109% of substance C added), indicating degradation of the substance, and a very pronounced negative net N mineralization within 7 d (–356%), which was interpreted as N immobilization. Only β‐sitosterol showed strong inhibition of net N mineralization after 7 and 14 d (–59% and –26%, respectively) which was not interpreted as N immobilization, since there was no concomitant increase in C mineralization. Thus, an antimicrobial effect of β‐sitosterol specificly on microorganisms of the N cycle was suggested, but there was no clear inhibitory effect caused by the antioxidant compounds.     

Seedball‐induced changes of root growth and physico‐chemical properties—a case study with pearl millet

Seedball is a cheap “seed‐pelleting‐technique” that combines local materials, seeds and optionally additives such as mineral fertilizer to enhance pearl millet (Pennisetum glaucum (L.) R. Brown) early growth under poor soil conditions. The major objective here was to study the mechanisms behind positive seedball effects. Chemical effects in the rhizosphere and early root development of seedball‐derived pearl millet seedlings were monitored using micro‐suction‐cups to extract soil solutions and X‐ray tomography to visualize early root growth. Pearl millet (single seedling) was grown in soil columns in a sandy soil substrate. Root and shoot biomass were sampled. X‐ray tomography imaging revealed intense development of fine roots within the nutrient‐amended seedball. Seedball and seedball+NPK treatments, respectively, were 65% and 165% higher in shoot fresh weight, and 108% and 227% higher in shoot dry matter than the control treatment. Seedball+NPK seedlings showed promoted root growth in the upper compartment and 105% and 30% increments in root fresh and dry weights. Soil solution concentrations indicate that fine root growth ass stimulated by release of nutrients from the seedballs to their direct proximity. Under real field conditions, the higher root length density and finer roots could improve seedlings survival under early drought conditions due to better ability to extract water and nutrients from a greater soil volume.     

Establishing a spatial grouping base for surface soil properties along urban–rural gradient—A case study in Nanjing,China

Conventional classification systems based on vegetation and land use are frequently used to characterize or describe urban soils to determine the influence of urbanization on soils. In this study, the sensitivity of different grouping methods in reflecting soil variations along an urban–rural gradient was compared. The objective of this study was to determine the most sensitive grouping system in depicting and explaining variations of soil attributes around an urban area. Grouping methods, including urban–rural division, in situ vegetation type, land use types in different scales and numerical clustering, were compared for both single soil attributes and “soil set” defined by multiple variables. The result shows urbanization has a strong impact on many soil properties, especially that of gravel content, sand content, pH, phosphorus and soil compaction. In terms of the variations of soil attributes, in situ vegetation type is the most sensitive in comparison with local land use types and district-viewed land use types. In other words, soil properties in this study are not sensitive to coarser spatial resolution. Therefore, it's hard to interpret the spatial variation of urban soil by regular methods using natural soil-landscape paradigm. Furthermore, vegetation would best proxy the delineation of single attribute of urban soils. Numerical clusters effectively reflect the land use types and their change during urbanization. All clusters were interpreted as different sets with practical meanings: soil in abandoned greenbelt, soil in ill-managed greenbelt, soil in new vegetable land, extreme urban conditioned soil, soil in well-managed greenbelt, soil in highly mellowed vegetable land, soil in common urban–peri-urban greenbelt and weak-urban-impacted soil. They can be used as bases for soil regionalization in urban and peri-urban environment.     

The conservation implications of bird reproduction in the agricultural “matrix”: a case study of the vulnerable superb parrot of south-eastern Australia

Where agriculture has recently been imposed on natural systems, habitats that are modified, but not destroyed, within the agricultural matrix, are often, undervalued for their conservation benefits. Ecological research in the agricultural matrix in such landscapes has been limited in many countries. Yet many organisms live and breed in these landscapes. This paper outlines a large-scale case study of the vulnerable superb parrot that breeds in trees in the agricultural matrix of south-eastern Australia. Superb parrot nest trees were located, measured and compared with a set of randomly chosen non-nest trees. Increasing tree diameter had the largest influence over whether a superb parrot nested in a tree. There was a strong preference for nesting in dead trees and Blakely's red gum. There was limited eucalypt regeneration surrounding trees. The large size and poor health of nest trees requires urgent habitat management to provide alternative nest sites and regenerate trees across the whole agricultural matrix. This will require a long-term vision on the scale of centuries.     

Analysing resilience in dryland agro‐ecosystems: a case study of the Makanya catchment in Tanzania over the past 50 years

Dryland agro‐ecosystems in sub‐Saharan Africa provide the resource base for some of the fasted growing populations today. However, rainfall variability and poor soils make these systems inherently vulnerable, and land degradation reduces their capacity to cope with disturbances. In this paper we propose a theoretical framework for interpreting dynamics and resilience in such systems, where two aggregate variables, the agricultural soil water index and the ecosystem insurance capacity, are particularly important. We apply the framework to the case of the Makanya catchment in Tanzania and conclude that the studied area has moved towards an increasingly degraded state, where ecosystem services other than food have been lost, over the past 50 years. Three main drivers behind this are identified; a) institutional changes affecting strategies for natural resource management, b) increased dry‐spell frequency, and c) high population growth. We suggest that the reason for the dramatic effects is that these changes occurred simultaneously, reducing the adaptive capacity of the local population. However, several trends in the area today indicate that there is a window of opportunity for positive change. Copyright © 2007 John Wiley & Sons, Ltd.     

Effects of extensive land use and re‐wetting on diffuse phosphorus pollution in fen areas—results from a case study in the Drömling catchment,Germany

Fen‐soil cultivation in NE Germany resulted in severe peat degradation; therefore present and future management is aimed to restore degraded sites by re‐wetting. Evidence in the literature indicates that decreasing redox potentials in re‐wetted fens may result in an increased risk of diffuse water pollution with P. However, little is known about the impact of different fen‐preserving land‐management schemes on the redox potential in soil and on the P dynamics in adjacent surface water. We investigated effects of peat degradation and re‐wetting on redox potential and P mobilization on extensive grassland, re‐wetted intensive grassland, and alder swamp forest in the Drömling (Saxony‐Anhalt, Germany). The results showed that the redox potentials of peat lands were almost below the theoretical stability fields of Fe(III)‐containing minerals. The re‐wetted site was characterized by the highest concentrations of soluble reactive P (SRP) in surface water. Average SRP concentrations up to 0.36 mg l^–1 indicated an increased P load. The concentration of SRP in the Ohre river, which is the central drainage channel of the Drömling catchment, significantly increased since 1996. The P concentrations of surface water were found to be indirectly correlated with the redox potentials.     

Additional nitrogen in arctic‐alpine soils and plants—a pilot study with 15NO $ _3^ - $ and 15NH $ _4^+ $ fertilization along an elevation gradient

Nitrogen (N) deposition has been increasing in alpine ecosystems, but its fate in soils and plants remains unclear. We assumed that the increased N load will be efficiently retained in alpine ecosystems but that the degree of N use efficiency changes with elevation. Thus, we performed a 3‐year ¹⁵N tracer experiment, in which we added 1 g m^?2 of either NH₄¹⁵NO₃ or ¹⁵NH₄NO₃ fertilizer to a plot of 1 m² in size at three elevations. Composite soil samples and aboveground plant material from lichens, dwarf shrubs, and graminoids were collected annually for three years and analyzed for their ¹⁵N accrual. We found a cumulative and plateauing rise in ¹⁵N concentration in soils and plants at all sites. However, overall recovery of the tracer decreased with time, amounting to 71% of fertilizer recovered in the soils in the first year, 69% recovered in soils and plants in the second year, and 37% in soils and plants in the third year. Moreover, the fertilizer use efficiency varied among fertilizer types and plant functional types. This utilization pattern appears to be modulated by elevation.