Soil aggregation: Influence on microbial biomass and implications for biological processes

Our 1988 paper, describing the effects of cultivation on microbial biomass and activity in different aggregate size classes, brought together the ‘aggregate hierarchy theory’ and the ‘microbial biomass concept’. This enabled us to identify the relationships between microbial and microhabitat (aggregate) properties and organic matter distribution and explain some of their responses to disturbance. By combining biochemical and direct microscopy based quantification of microbial abundance with enzyme activities and process measurements, this study provided evidence for the role of microbial biomass (especially fungi) in macroaggregate dynamics and carbon and nutrient flush following cultivation. In the last ten years environmental genomic techniques have provided much new knowledge on bacterial composition in aggregate size fractions yet detailed information about other microbial groups (e.g. fungi, archaea and protozoa) is lacking.We now know that soil aggregates are dynamic entities – constantly changing with regard to their biological, chemical and physical properties and, in particular, their influences on plant nutrition and health. As a consequence, elucidation of the many mechanisms regulating soil C and nutrient dynamics demands a better understanding of the role of specific members of microbial communities and their metabolic capabilities as well as their location within the soil matrix (e.g. aggregates, pore spaces) and their reciprocal relationship with plant roots. In addition, the impacts of environment and soil type needs to be quantified at the microscale using, wherever possible, non-destructive ‘in situ’ techniques to predict and quantify the impacts of anthropogenic activities on soil microbial diversity and ecosystem level functions.     

Organic input quality is more important than its quantity: C turnover coefficients in different cropping systems

Annual C input to soil is a major factor affecting soil organic carbon (SOC) dynamics. However different types of C-sources can have different behaviour, in relation to their chemical characteristics and how they interact with soil. Root-derived C, in particular, should be more efficient than other organic materials as a result of the physicochemical and biological characteristics of the surrounding environment, leading to a reduction in the C decomposition rate.To test this hypothesis, we considered a long-term experiment underway in Northern Italy since 1962, comparing permanent meadow and 6 different crop rotations over a wide range of nutrient inputs, in both organic and inorganic forms. C inputs from amendments were measured and those from crops were calculated using allometric functions and crop and residues yields. The time evolution of SOC was studied through a single-pool, first-order kinetic model, allowing the estimation of humification coefficients for residues, roots, farmyard manure and cattle slurries.The highest value of the humification coefficient was estimated for farmyard manure, which confirmed its high efficiency in stabilising SOC content. Root C presented a humification coefficient 1.9 times higher than above-ground plant materials while slurries were intermediate, with a humification coefficient roughly half that of farmyard manure and even lower that of roots.The quality of C input thus seems of fundamental importance for evaluating the sustainability of different cropping systems in terms of SOC dynamics.     

Single season effects of mixed-species cover crops on tomato health (cultivar Celebrity) in multi-state field trials

Cover crop use can help mitigate the deleterious effects of common cropping practices (e.g., tillage) and is, therefore, an important component of soil health maintenance. While known to be beneficial in the long-term, the short-term effects of cover crops, specifically mixed-species cover crops in organic systems are less clear. Cover crop effects on tomato productivity and disease severity were recorded over three field seasons (2010, 2011 and 2012) at sixteen field sites in three states, Maryland, New York and Ohio (MD, NY and OH), each with distinct soilborne disease pressure. Plots of five state-specific cover crop treatments were established the season prior to tomato production; the resulting plant residue was incorporated the following spring approximately four weeks before tomato planting. Total fruit yields along with early-season shoot height and fresh weight were used to compare treatment effects on productivity. Treatment disease severity ratings relied on natural inoculum. Interestingly, the effect of a single season of cover cropping on total yield was significant in no more than 25% of all site years. Similarly, cover crop effects on tomato disease levels were significant in 0–44% of the sixteen field sites. However, significant field-specific patterns were observed in every state across multiple years for some treatments. For example, in New York in 2010, tomato yields following all mixed cover crops were greater than the single rye cover crop in one field, but this pattern was reversed in the adjacent field. Thus, no general recommendation of a specific cover crop mixture can be made for near-term enhancement of tomato productivity or for reduction of disease. Therefore, growers should focus on location and operation-specific variables when choosing cover crops.     

我国有机水稻发展对策探析

阐述了我国发展有机水稻的积极意义，分析了有机水稻发展的制约因素，并提出了我国政府提高对有机水稻生产的支撑、扶持龙头企业的壮大发展、加强市场监管、采用合理的方式组织规模生产、实行科学种田等措施促进有机水稻良性发展。     

优质油菜施硫效应研究

试验表明,在土壤偏碱性,有效58.75mg/kg条件下,玉米作物施硫具有显著的增产、增值效果。施硫对提高单位面积有效穗数、平均穗籽粒数、千粒质量、叶色深度具有显著的影响,对生育时段影响较小,增产、增值效应随用量不同而异,增产9.33～26.83kg/667m~2,平均产量19.29kg/667m~2,增产率5.76%～16.59%,投产比10.17～4.32,合理用量为纯硫。2.00～4.00kg/667m~2,做底肥施用。     

The Humus Content and Soil Biological Properties as a Function of Organic and Mineral Fertilization

There is a growing recognition for the need to develop sensitive indicators of soil quality that reflect the effects of land management on soil and assist land users in promoting sustainability of agro-ecosystems. Three soil enzymes (dehydrogenase, phosphatase and invertase) microbial biomass as biological variables and soil organic matter content (SOM) were investigated relative to fertilization and soil fertility (estimated by crop yield) at a long-term fertilization trial (Keszthely, Hungary). 0-34.7-69.4-104.1t farmyard manure (FYM) ha m 1 5 yr m 1 and the corresponding amount of mineral fertilizers (NPK) were applied in two different crop rotation systems. There were four straw and/or stalk incorporating treatments in the second crop rotation 'B'. Enzyme activities, microbial biomass and the amount of SOM were generally higher in the fertilized soils than in the unfertilized soils. The type of amendments (mineral, FYM or mixed) had significant effects only on the amount of SOM. The correlations among the biological variables and the crop yield were generally low (r < 0.250. The differences in field management resulted only in the invertase activity.     

Soybean yield and yield components as influenced by the single and repeated flaming

Field experiments were conducted to study the impact of single and multiple flaming on crop injury, yield components, and yield of soybean. The goal of this experiment was to determine the number of the maximum flaming treatments which soybean could tolerate without any yield loss. The treatments consisted of a non-flamed control, and broadcast flaming conducted one time (at VC-unfolded cotyledon, V2-second trifoliate, and V5-fifth trifoliate), two times (each at VC and V2, VC and V5, and V2 and V5 stages), and three times (at VC, V2, and V5 stages) resulting in a total of eight treatments. All plots were kept weed-free for the entire growing season by hand hoeing. A propane dose of 50 kg ha⁻¹ was applied with torches parallel to the crop row and at an operating speed of 4.8 km h⁻¹ for all treatments. The response of soybean was measured as visual injury ratings (at 7 and 28 days after treatment – DAT) as well as effects on yield components and yield. Broadcast flaming conducted once (at VC or V5 stage), as well as twice (at VC and V5 stages) exhibited the lowest injury of about 8% at 28 DAT. Any treatment that contained flaming at V2 stage resulted in more than 70% injury at 28 DAT. The highest crop yields were obtained from the non-flamed control (3.45 t ha⁻¹) and the plots flamed once at VC (3.35 t ha⁻¹), V5 (3.32 t ha⁻¹), and two times at VC and V5 (3.24 t ha⁻¹), which were all statistically similar. Soybean flamed at V2 stage had lower yields (1.03 t ha⁻¹ at V2, 0.46 t ha⁻¹ at VC and V2, and 0.38 t ha⁻¹ at V2 and V5). The lowest yields were in soybean flamed three times (VC, V2, and V5 stages), which yielded only 0.36 t ha⁻¹. These results indicate that soybean could tolerate a maximum of two flaming treatments at VC and V5 growth stages per season without any yield reduction.     

有机无机肥料对小麦的肥效及其交互作用

在京郊大同肥力水平土壤上,有机肥和化肥配合施用小麦增产量最高,其增量在中、高肥力试验点上大于低肥力试验点.有机肥和化肥配合施用时的增产作用是它们各自增产效应之和,它们之间的交互效应不显著.在高肥力土壤上甚至有负的交互效应,即配台施用时的增产量小于分施时各自增产量之和.根据肥料试验,本文提出了京郊不同肥力水平土壤上小麦有机无机肥料配合施用量,并发现在低肥力土壤上随着有机肥的施用,化肥氮的用量增加,化肥磷用量可减少;在高肥力土壤上随有机肥的施用,化肥氮用量减少,化肥磷用量增加;在中等肥力土壤上配合有机肥的施用,氮磷化肥用量均个应减少,应略为增加.     

厌氧生物水处理技术研究进展

在原有脱碳技术基础上,废水厌氧处理在其他领域的研究与应用被不断拓展.本文介绍了近年来厌氧生物处理技术的新发展,从理论和工艺两个方面,综述了厌氧生物脱硫、生物制氢、厌氧氨氧化、厌氧反硝化的原理、研究、技术开发与应用.     

Conversion to organic arable farming in The Netherlands: A dynamic linear programming analysis

Several studies show that organic farming is more profitable than conventional farming. However, in reality not many farmers convert to organic farming. Policy makers and farmers do not have clear insight into factors which hamper or stimulate the conversion to organic farming. The objective of this paper is to develop a dynamic linear programming model to analyse the effects of different limiting factors on the conversion process of farms over time. The model is developed for a typical arable farm in The Netherlands central clay region, and is based on two static liner programming models (conventional and organic). The objective of the model is to maximise the net present value over a 10-year planning horizon. The results of the analysis of a basic scenario show that conversion to organic farming is more profitable than staying conventional. In order to arrive at the actual profitable phase of organic farming, the farmer has to pass through the economically difficult 2-year conversion period. Sensitivity analysis shows that if depreciation is 25% higher than conventional fixed costs due to machinery made superfluous by conversion, conversion is less profitable than staying conventional. Also the availability of hired labour, which can be constrained in peak periods, has a strong effect on the cropping plan and the amount of area converted. Further analysis shows that a slight drop (2%) in organic prices lowers the labour income of the farmer and makes conversion less profitable than conventional farming. For farmers, a minimum labour income can be required to ‘survive’. The analysis shows that constraint on minimum labour income makes stepwise conversion the best way for farmers to overcome economic difficulties during conversion.