Site preparation of abandoned fields and early establishment of planted small-sized seedlings of silver birch

Field experiments at two sites in Sweden investigated the possibility of establishing silver birch (Betula pendula Roth) on abandoned fields by planting small (5–10 cm tall) seedlings. The effects of five modes of soil preparation (no preparation, rotary cultivation, deep ploughing, soil inversion, and removal of topsoil) with or without preliminary herbicide weed control on seedling performance were studied for three growing seasons following plantation. Both a split-plot design and a randomized block design were used to evaluate the experiments. Where there was no site preparation, seedling survival was close to nil. The highest seedling survival rates on the site with sandy soil were obtained on sites prepared by removing topsoil, or by transposing it by deep ploughing. On the site with silty soil, the best survival was observed on sites created by soil inversion or rotary cultivation. The tallest seedlings were found on sites with topsoil retained within the soil profile. Herbicide application with glyphosate promoted seedling survival and seedling height in combination with no soil preparation, but was of little effect when followed by mechanical soil preparation.     

低山丘陵区耕地与基本农田保护研究

选取典型低山丘陵区－－黄山市为研究对象,在分析耕地资源利用存在的主要问题基础上,针对低山丘陵区耕地后备资源有限的情况,建议耕地与基本农田保护必须要打破传统的保护模式,建立以提高耕地质量为主、数量增加为辅的动态平衡机制,并提出灵活的占补平衡措施。     

Fungi,bacteria and protozoa in soil from four arable cropping systems

Summary The effects of four cropping systems on soil microorganisms were investigated during 3 years. The cropping systems were B0, barley without nitrogen fertilizers; B120, barley with 120 kg N ha^–1 year^–1; GL, grass ley receiving 200 kg N ha^–1 year^–1; and LL, lucerne ley without nitrogen fertilizer additions. At samplings in September during three consecutive years no differences were found between treatments. Total fungal lengths ranged between 0.7 and 2.0 × 10³ m and bacterial numbers between 3.5 and 7.2 × 10⁹ g^–1 dry wt. soil.Twenty samplings over 3 years in B120 and in GL indicated higher numbers of bacteria and protozoa during the growing season, except for periods with moisture stress. No clear seasonal trends were found for the fungi. When comparing mean values for the 20 samplings, the grass ley contained significantly (P < 0.05) higher numbers of amoebae. Means of the bacterial numbers and biomass, total and FDA-active hyphal lengths were also higher or equal (FDA-active hyphae) but not significantly so.Seventy-nine per cent of the bacterial biomass and 73% of the total fungal lengths were found in the top soil, where also 85% of the oxygen was consumed.     

关于耕地生态保护规划基本问题的探讨

在界定耕地生态保护规划基本概念的基础上，系统阐述了耕地生态保护规划的原则、内容以及规划程序和方法，并对全面开展耕地生态保护规划的编制和方案评优提出政策建议。     

The microbial PLFA composition as affected by pH in an arable soil

The influence of soil pH on the phospholipid fatty acid (PLFA) composition of the microbial community was investigated along the Hoosfield acid strip, Rothamsted Research, UK - a uniform pH gradient between pH 8.3 and 4.5. The influence of soil pH on the total concentration of PLFAs was not significant, while biomass estimated using substrate induced respiration decreased by about 25%. However, the PLFA composition clearly changed along the soil pH gradient. About 40% of the variation in PLFA composition along the gradient was explained by a first principal component, and the sample scores were highly correlated to pH (R² = 0.97). Many PLFAs responded to pH similarly in the Hoosfield arable soil compared with previous assessments in forest soils, including, e.g. monounsaturated PLFAs 16:1ω5, 16:1ω7c and 18:1ω7, which increased in relative concentrations with pH, and i16:0 and cy19:0, both of which decreased with pH. Some PLFAs responded differently to pH between the soil types, e.g. br18:0. We conclude that soil pH has a profound influence on the microbial PLFA composition, which must be considered in all applications of this method to detect changes in the microbial community.     

耕地质量的概念和评价与管理对策

耕地是最重要的农业资源之一,耕地质量是国家粮食安全和农产品质量安全的重要基础。本文根据文献资料,归纳总结了耕地质量概念及评价方法的研究现状,认为耕地质量是个多层次的概念,包含耕地的土壤质量、空间地理质量、管理质量和经济质量四层涵义,评价指标包含自然和社会经济两大因素。分析了我国耕地质量变化状况,结果表明,总体上我国耕地质量等级偏低,其中肥力质量、管理质量及经济质量逐渐趋好,但是健康质量和环境质量却日趋恶劣,部分区域耕地质量问题严重。文章还提出了针对我国国情的耕地质量建设及管理建议。     

辽宁省耕地质量与环境保障问题及其体系建设

本文通过分析我省当前耕地质量与环境保障体系建设的有关问题,探讨建设我省耕地质量及其环境预测预警监测体系、无公害农产品生产基地环境评价系统、主要农作物平衡施肥技术体系模式,并提出我省整个耕地质量及其环境保障体系的各项保障措施。     

耕地生态经济系统动态监测研究

在分析中国耕地生态经济系统运行的波动性、结构的复杂性、“体质”的脆弱性和调控的滞后性4个特征的基础上，指出开展耕地生态经济系统的动态监测，可使耕地管理由静态、被动状态走向动态、主动状态，实现耕地生态经济系统调控的超前性，切实有效地保护耕地。并阐述了耕地生态经济动态监测预警系统所包含的警义、警源、警兆和警度4个方面的基本内容以及构建中国耕地生态经济动态监测机制的基本思路与方法。     

Molecular diversity of bacterial chitinases in arable soils and the effects of environmental factors on the chitinolytic bacterial community

The molecular diversity of bacterial chitinases in the bulk soils of arable land was investigated using culture-independent methods. The results demonstrate that bacterial chitinases in arable soils are highly diverse and comprise unique groups when their sequences were compared to those in public databases. The diversity of bacterial chitinases in arable soil was further evaluated using conventional phylogenetic analysis, the UniFrac analysis of the phylogenetic data, and the multidimensional scaling (MDS) analysis of T-RFLP profiles to elucidate the relationship between the diversity of bacterial chitinases and soil characteristics. These analyses indicate that environmental factors such as soil type and pH are responsible for shaping the composition of bacterial chitinases.     

Land use in agricultural landscapes with chernozems contaminated after Chernobyl accident: Can we be confident in radioecological safety of plant foodstuff?

Agricultural land use in the area of the post-Chernobyl Plavsk radioactive hotspot (Tula region, Central Russia) has raised a problem of radioecological safety of obtained plant foodstuff. Verification of ¹³⁷Cs activities and inventories in components of “soil-plant” systems of the territory has been conducted in 2014–2017 in 10 agrosystems and 2 semi-natural meadows. It was revealed that density of ¹³⁷Cs contamination of arable chernozems and alluvial calcareous soils nowadays varies in a range 140–220 kBq/m² and exceeds radiation safety standard by ˜ 3.5–6 times. Deep plowing of the arable soils up to 30-cm in 1986–1987 resulted in decreasing of ¹³⁷Cs inventories in rooting zone by ≈ 70% for crops cultivated with shallow disk plowing (wheat, barley), and by ≈ 35% for crops cultivated with middle plowing (buckwheat, amaranth, white mustard). The investigated plants and their compartments can be grouped on the basis of transfer factor values as follows: maize (stems and leaves) > amaranth > bromegrass > vegetation of dry meadow, galega, sunflower (seeds), vegetation of wet meadow > maize (grain), soybean (pods), barley (grain), buckwheat (grain), potatoes (tubers) > white mustard (seeds), wheat (grain). It is noticeable that generative plant compartments are characterized by less ¹³⁷Cs activities in comparison with stems and leaves; and that ¹³⁷Cs root uptake is not coincide with total flux of mineral nutrients in “soil-plant” systems. In sum, ¹³⁷Cs soil-to-plant transfer in the area of the Plavsk radioactive hotspot is characterized by considerable discrimination, so ¹³⁷Cs activities in plants are completely in accordance with national standards.