Partial replacement of Fe(o,o‐EDDHA) by humic substances for Fe nutrition and fruit quality of citrus

The most widely used Iron (Fe) fertilizer in calcareous soils is the synthetic chelate Fe(o,o‐EDDHA). However, humic substances are occasionally combined with Fe chelates in drip irrigation systems in order to lower costs. We investigated the effect of various mixtures of Fe(o,o‐EDDHA) and a commercially available humic substance on Fe availability in a calcareous soil from Murcia, Spain (in vitro experiment) and on leaf Fe content and fruit‐quality attributes of Citrus macrophylla (field experiment). In the in vitro experiment, a calcareous soil was incubated for 15 d with solutions of sole Fe(o,o‐EDDHA) and humic substance and of a mixture of humic substance and Fe(o,o‐EDDHA) to determine the dynamics of available Fe. While the mixture did not significantly increase the available soil Fe, it did decrease the rate of Fe retention in the surface soil compared to sole Fe(o,o‐EDDHA). In the field experiment, the substitution in the application solution of 67% of Fe(o,o‐EDDHA) by commercial humic substance increased leaf P in lemon trees from 0.19% with sole Fe(o,o‐EDDHA) to 0.30% and leaf Fe from 94 mg kg^–1 to 115 mg kg^–1. Some quality parameters like vitamin C content and peel thickness were also improved with a partial substitution of Fe(o,o‐EDDHA) by humic substances. We conclude that a partial substitution of commercial Fe chelates by humic substance can improve crop Fe uptake and may thus be economically attractive. The underlying physiological mechanisms and ecological implications require further studies.     

Evidence of plaggen soils in European North Russia (Arkhangelsk region)

To clarify whether a particular group of soils of Archangelsk region (European N Russia) with humus‐rich topsoils exceeding the plowing zone supports an anthropogenic formation, four exemplary profiles were investigated. The investigation sites are characterized by distinct elevated surfaces, and the soils show thick toplayers of up to 60 cm with enrichment of soil organic matter and artifacts like brick, charcoal, and peat fragments, all indicating an anthropogenic origin. Increased phytolith amounts and high P contents of up to 800 mg kg^–1 citric acid–soluble P and up to 1,400 mg kg^–1 total P in the top horizons support an anthropogenic influence. These properties are very similar to the Plagganthrepts of NW Europe. The same is true regarding the main management aims: increasing soil fertility and overcoming the need of bedding materials. Having the required depths of the anthropogenic topsoil, the properties of the soils of the Archangelsk region allow a classification as Agrozems (Russian classification), Plaggenesche (German classification), and Plagganthrepts (US taxonomy). Since the high base saturation of the topsoil excludes a designation as plaggic horizon, the topsoil has to be considered as terric horizon, which leads to a classification as Terric Anthrosol according to WRB.     

横断山北部土壤钾素的区域分布特征

横断山北部是我国地理环境独特和生物多样性最丰富的地区之一，其生态恢复与重建对整个长江流域的水土流失治理及生态安全具有重要的现实意义，故一直受到国内外学术界的高度关注。但由于近40年来人类活动和气候环境的变化，其林木蓄积量大幅度减少，水土流失日趋严重，生态环境破碎化，部分野生动植物资源已濒临灭绝，已有研究表明属生态脆弱区。尽管该区实施退耕还林工程和天然林保护工程已四年，但因该区域有关生态环境（包括土壤钾素养分等）的基础研究资料较少，生态重建进度仍很缓慢。     

Nitrogen metabolism in flag leaf and grain of wheat in response to irrigation regimes

Although scarcity of irrigation water is one of the key limiting factors for wheat production in many regions of the world, by using partial irrigation at strategic times during the growing season, it might be possible to enhance productivity. We measured the changes in various parameters related to nitrogen (N) metabolism in flag leaf and grain of wheat (Triticum aestivum L.) plants (cv. Jinan 17 and Lumai 21), which were subjected to five irrigation regimes until physiological maturity. Severely deficient or excessive irrigation during grain filling decreased the photosynthetic rate (A), the concentrations of N, free amino acid, and soluble protein, as well as the activities of nitrate reductase (NR) and glutamine synthetase (GS) and increased malondialdehyde (MDA) accumulation and endopeptidase (EP) activity, though grain protein concentration might mainly depend on genotype. The activities of NR and GS were significantly positively correlated with A, but those of EP were significantly negatively correlated with A. The results indicate that while severe water stress aggravates the adverse effect on nitrogen metabolism, excessive soil moisture is also not useful during the grain‐filling stage, resulting in lower grain yield and quality. Our results suggest that applying an optimal irrigation regime in wheat fields still plays an important role in the improvement of grain yield and quality.     

长武王东沟小流域土地利用变化及驱动力研究

对王东沟流域1994年和2002年的土地利用现状进行了分析,揭示了近几年来该区土地利用变化的主要类型及各种土地利用类型的空间格局变化特征。研究表明,该区土地利用方式以耕地、园地、林地为主,变化以耕地和园地为主,并且主要集中在塬面上。自然因素、比较经济效益和宏观政策是该区土地利用变化的主要驱动力。最后,从农业可持续发展角度,对试区土地利用提出了建议。     

Sources of variation in nutrient intakes among men in Shanghai, China

BACKGROUND AND OBJECTIVE: Random errors, from any source, will attenuate epidemiological risk estimates. Before we launched the Shanghai Men's Health Study (SMHS), a large population-based cohort study investigating the diet-cancer association among Chinese men, a dietary calibration study was conducted among 96 men aged 40-75 years (mean age 56.5 years), with biweekly 24-hour dietary recalls (24HDRs) implemented over a 1-year period. Data from this study were analysed to evaluate the nature and magnitude of variances for intake of 26 nutrients among SMHS participants, to compare variance ratios of 26 nutrients among Chinese men and women and individuals in other studies, and to estimate the number of 24HDRs required for future dietary calibration studies in similar populations. DESIGN: Ninety-six healthy, free-living men in Shanghai were administered biweekly 24HDR interviews 24 times over a 1-year period. To assess between-individual and within-individual contributions to variance, a mixed effects model was fitted and ratios of within-individual to between-individual (sigma(w)(2)/sigma(b)(2)) dietary intake variances were computed. SETTING: Shanghai, China. RESULTS: In agreement with reports from studies conducted in the USA and many other countries, we found that within-individual variances were usually larger than between-individual variances in dietary intake for all nutrients. The sum of all other variation (e.g. weekday and weekend, seasonal, interviewer) accounted for less than 5% of total variation. Ratios of within- to between-individual variances (for log-transformed data) ranged from 1.25 for carbohydrate intake to near 8 for delta-tocopherol intake. CONCLUSIONS: The results of this study suggest that among middle-aged and elderly Chinese men in Shanghai, within- and between-individual variation account for more than 95% of the total variation for 26 nutrients. Further dietary validation studies in the same population could be adequately carried out with only 12 days of dietary recalls, if 100 participants were enrolled.     

Soil‐ and plant‐based nitrogen‐fertilizer recommendations in arable farming

Under‐ as well as overfertilization with nitrogen (N) will result in economic loss for the farmer due to reduced yields and quality of the products. Also from an ecological perspective, it is important that the grower makes the correct decision on how much and when to apply N for a certain crop to minimize impacts on the environment. To aggravate the situation, N is a substance that is present in many compartments in different forms (nitrate, ammonium, organic N, etc.) in the soil‐plant environment and takes part in various processes (e.g., mineralization, immobilization, leaching, denitrification, etc.). Today, many N‐recommendation systems are mainly based on yield expectation. However, yields are not stable from year to year for a given field. Also the processes that determine the N supply from other sources than fertilizer are not predictable at the start of the growing season. Different methodological approaches are reviewed that have been introduced to improve N‐fertilizer recommendations for arable crops. Many soil‐based methods have been developed to measure soil mineral N (SMN) that is available for plants at a given sampling date. Soil sampling at the start of the growing period and analyzing for the amount of NO ‐N (and NH ‐N) is a widespread approach in Europe and North America. Based on data from field calibrations, the SMN pool is filled up with fertilizer N to a recommended amount. Depending on pre‐crop, use of organic manure, or soil characteristics, the recommendation might be modified (±10–50 kg N ha^–1). Another set of soil methods has been established to estimate the amount of N that is mineralized from soil organic matter, plant residues, and/or organic manure. From the huge range of methods proposed so far, simple mild extraction procedures have gained most interest, but introduction into practical recommendation schemes has been rather limited. Plant‐analytical procedures cover the whole range from quantitative laboratory analysis to semiquantitative “quick” tests carried out in the field. The main idea is that the plant itself is the best indicator for the N supply from any source within the growth period. In‐field methods like the nitrate plant sap/petiole test and chlorophyll measurements with hand‐held devices or via remote sensing are regarded as most promising, because with these methods an adequate adjustment of the N‐fertilizer application strategy within the season is feasible. Prerequisite is a fertilization strategy that is based on several N applications and not on a one‐go approach.