Soil risk maps – Interpreting soils data for policy makers,agencies and industry

Surface runoff, erosion, compaction and the leaching of potential pollutants from land can degrade the soil resource and damage the water environment, reducing crop yields, causing loss of valuable nutrients and organic matter, together with increasing flood risk. Increasingly, it is recognized that scientific information must be translated into practical tools to change practices and protect the soil and water resource. Working alongside agencies in Scotland, we applied a suite of simple, transparent, rule-based models to identify areas most at risk of exporting sediment and pollutants that may degrade water quality based on field-scale (1:25,000) soil maps. The maps have been used by Scottish Environment Protection Agency, Scottish Water and Scottish Government to assess soil risks to waters from field to regional scale. The work brought scientists together with policy makers, agencies and the water industry to pool their knowledge to apply these practical tools for decision-making. It highlights the need to apply existing knowledge to answer salient questions. All three examples described show that providing the right type of information, which is based on fundamental soils data, can directly influence the implementation of policies, investment and monitoring decisions and provide evidence in support of government. However, this requires both researchers and agency scientists to develop skills as knowledge brokers and to normalize the use of soil data in everyday agency settings.     

Effects of Irrigation Patterns and Nitrogen Fertilization on Rice Yield and Microbial Community Structure in Paddy Soil

Water and nitrogen (N) are considered the most important factors affecting rice production and play vital roles in regulating soil microbial biomass, activity, and community. The effects of irrigation patterns and N fertilizer levels on the soil microbial community structure and yield of paddy rice were investigated in a pot experiment. The experiment was designed with four N levels of 0 (N0), 126 (N1), 157.5 (N2), and 210 kg N ha-1 (N3) under two irrigation patterns of continuous water-logging irrigation (WLI) and water-controlled irrigation (WCI). Phospholipid fatty acid (PLFA) analysis was conducted to track the dynamics of soil microbial communities at tillering, grain-filling, and maturity stages. The results showed that the maximums of grain yield, above-ground biomass, and total N uptake were all obtained in the N2 treatment under WCI. Similar variations in total PLFAs, as well as bacterial and fungal PLFAs, were found, with an increase from the tillering to the grain-filling stage and a decrease at the maturity stage except for actinomycetic PLFAs, which decreased continuously from the tillering to the maturity stage. A shift in composition of the microbial community at different stages of the plant growth was indicated by principal component analysis (PCA), in which the samples at the vegetative stage (tillering stage) were separated from those at the reproductive stage (grain-filling and maturity stages). Soil microbial biomass, measured as total PLFAs, was significantly higher under WCI than that under WLI mainly at the grain-filling stage, whereas the fungal PLFAs detected under WCI were significantly higher than those under WLI at the tillering, grain-filling, and maturity stages. The application of N fertilizer also significantly increased soil microbial biomass and the main microbial groups both under WLI and WCI conditions. The proper combination of irrigation management and N fertilizer level in this study was the N2 (157.5 kg N ha-1) treatment under the water-controlled irrigation pattern.     

基于新农村建设中水土保持问题的探讨——以贵州岩溶山区为例

贵州岩溶地区水土流失的因素别有人口压力过大,自然灾害严重,矿产资源的不合理开采,森林覆盖率低,当地干部群众认识不足,文章从岩溶山区水土保持生态环境特征进行分析,指出水土流失是制约全面推进建设社会主义新农村建设的主要问题之一.     

Effect of Integrated Nutrient Management on Soil Physical Properties and Crop Productivity under a Maize (Zea mays)–Mustard (Brassica campestris) Cropping Sequence in Acidic Soils of Northeast India

A five-year (2001/02–2006/07) field experiment was carried out on acidic clay loam soil classified as Typic Hapludalf with a maize–mustard crop sequence to study the effect of continuous application of nitrogen, phosphorus, and potassium (NPK) fertilizers alone and in combination with lime, farmyard manure (FYM), and biofertilizers on soil physical properties, soil organic carbon (SOC), soil microbial biomass carbon (SMBC), and crop yields on the hilly ecosystem of Meghalaya. Significant improvement in the soil physical conditions of the soil was observed under integrated application of organic manure and inorganic fertilizers. Addition of NPK fertilizers along with organic manure, lime, and biofertilizers increased soil organic carbon (SOC) content, aggregate stability, moisture-retention capacity, and infiltration rate of the soil while reducing bulk density. The SOC content under the treatment of 100% NPK + lime + biofertilizer + FYM was significantly greater (68.58%) than in control plots. Maize and mustard crop yields also significantly increased (4.73- and 21.09-folds, respectively) with continuous application of balanced inorganic (100% NPK) + lime + biofertilizer + FYM as compared to the control plots. However, crop yields drastically reduced under application of integrated nutrients without FYM as compared to the treatment with FYM application. Thus, the results suggest that integrated use of a balanced inorganic fertilizer in combination with lime and organic manure sustains a soil physical environment that is better for achieving higher crop productivity under intensive cropping systems in the hilly ecosystem of northeastern India.     

三岔河小流域水土保持基础效益评价研究

通过对“东北黑土区水土流失综合防治试点工程”中建立的不同措施的径流小区的监测,选择具有典型黑土的黑龙江省宾县三岔河小流域作为研究对象,分别对地埂植物带、荒山灌木埂、横垄、水平坑(坑内植树)、裸地、顺垄6个小区进行了为期2 a的观测。经实测分析计算得出:相对于裸地来说,水平台田、荒山灌木埂、横垄、地埂植物带和顺垄减少侵蚀量分别为99.14%,97.65%,90.66%,87.7%和58.72%,减沙保土效果最好的是水平台田,顺垄保土效果最差。     

Ecosystem fertility and fallow function in the humid and subhumid tropics

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 cmol_c 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.