The immunoglobulin-like genetic predetermination of the brain: the protocadherins, blueprint of the neuronal network

The morphogenesis of the brain is governed by synaptogenesis. Synaptogenesis in turn is determined by cell adhesion molecules, which bridge the synaptic cleft and, by homophilic contact, decide which neurons are connected and which are not. Because of their enormous diversification in specificities, protocadherins (pcdh!, pcdh#, pcdh%), a new class of cadherins, play a decisive role. Surprisingly, the genetic control of the protocadherins is very similar to that of the immunoglobulins. There are three sets of variable (V) genes followed by a corresponding constant (C) gene. Applying the rules of the immunoglobulin genes to the protocadherin genes leads, despite of this similarity, to quite different results in the central nervous system. The lymphocyte expresses one single receptor molecule specifically directed against an outside stimulus. In contrast, there are three specific recognition sites in each neuron, each expressing a different protocadherin. In this way, 4,950 different neurons arising from one stem cell form a neuronal network, in which homophilic contacts can be formed in 52 layers, permitting an enormous number of different connections and restraints between neurons. This network is one module of the central computer of the brain. Since the V-genes are generated during evolution and V-gene translocation during embryogenesis, outside stimuli have no influence on this network. The network is an inborn property of the protocadherin genes. Every circuit produced, as well as learning and memory, has to be based on this genetically predetermined network. This network is so universal that it can cope with everything, even the unexpected. In this respect the neuronal network resembles the recognition sites of the immunoglobulins.     

Bioreactor systems for thermophilic fermentative hydrogen production: evaluation and comparison of appropriate systems

Numerous different bioreactor systems are applied for hydrogen production by dark fermentation. Thermophilic fermentations are gaining an increased interest due to the high hydrogen yields associated with them. In order to reach the best thermophilic fermentation system, 2 types of bioreactors, a trickling bed and a fluidized bed system, were constructed and operated under similar conditions. Both systems were designed to meet the requirements of thermophilic fermentations, such as reduction of hydrogen partial pressure, system immanence as its best as well as increasing cell densities. For comparing the 2 systems, the extreme thermophilic organism Caldicellulosiruptor owensensis OL^T and a glucose-containing medium were employed. Parameters like hydraulic retention time, glucose concentration and stripping gas amount were varied. Each bioreactor system exhibited certain advantages; the trickling bed system enabled yields close to 3 mol-H₂ (mol-glucose)^?1 and productivities of 0.2 L L^?1 h^?1, but the application of stripping gas seemed to be obligatory. The fermentations in the fluidized bed system were characterized by slightly higher productivities (0.25 L L^?1 h^?1), but generally lower yields. However, operation of this system without stripping gas was possible.     

Initial Homotypic Cell Pair Adhesion in Regenerating Hydra Facilitates Subsequent Adhesion of Homotypic Cells

 In Hydra vulgaris at the level of dissociated single cells endodermal cells adhere to each other more readily than to ectodermal cells at the initial adhesion. The time required for adhesion to occur between two adjacent cells is shorter for both endodermal and ectodermal homotypic cell adhesions once the initial adhesion of the first pair of cells has been established. It is confirmed that contact of an aggregated pair with additional homotypic cells facilitates the occurrence of homotypic adhesions; heterotypic adhesions are discouraged. This suggests that adhesion of homotypic cells contributes to an increased readiness for subsequent homotypic cells to adhere. Received: 25 August 1999 / Accepted in revised form: 11 January 2000     

Long-term impact of a gliricidia-maize intercropping system on carbon sequestration in southern Malawi

Tree/crop systems under agroforestry practice are capable of sequestering carbon (C) in the standing biomass and soil. Although studies have been conducted to understand soil organic C increases in some agroforestry technologies, little is known about C sequestered in simultaneous tree/crop intercropping systems. The main objective of this study was to determine the effect of agroforestry practice on C sequestration and CO₂-C efflux in a gliricidia-maize intercropping system. The experiment was conducted at an experimental site located at the Makoka Agricultural Research Station, in Malawi. The studies involved two field plots, 7-year (MZ21) and 10-year (MZ12), two production systems (sole-maize and gliricidia-maize simultaneous intercropping systems). A 7-year-old grass fallow (Grass-F) was also included. Gliricidia prunings were incorporated at each time of tree pruning in the gliricidia-maize. The amount of organic C recycled varied from 0.8 to 4.8 Mg C ha⁻¹ in gliricidia-maize and from 0.4 to 1.0 Mg C ha⁻¹ in sole-maize. In sole-maize, net decreases of soil carbon of 6 Mg C ha⁻¹ at MZ12 and 7 Mg C ha⁻¹ at MZ21 in the topsoil (0–20 cm) relative to the initial soil C were observed. After 10 years of continuous application of tree prunings C was sequestered in the topsoil (0–20 cm) in gliricidia-maize was 1.6 times more than in sole-maize. A total of 123–149 Mg C ha⁻¹ were sequestered in the soil (0–200 cm depth), through root turnover and pruning application in the gliricidia-maize system. Carbon dioxide evolution varied from 10 to 28 kg ha⁻¹ day⁻¹ in sole-maize and 23 to 83 kg ha⁻¹ day⁻¹ in gliricidia-maize. We concluded that gliricidia-maize intercropping system could sequester more C in the soil than sole-maize.     

Greenhouse gas emissions from rice based cropping systems: Economic and technologic challenges and opportunities

Recent market slump in rice, less rainfall during monsoon, high temperature and scarcity of water during dry season leads to lower grain yield and less profit from rice cultivation in India. Farmers’ grow upland crops like chickpea (Cicer arietinum), greengram (Vigna radiate), mustard (Brassica nigra), corn (Zea maize), pigeonpea (Cajanus cajan), potato (Solanum tuberosum), sunflower (Helianthus annuus) etc. along with rice (Oryza sativa) during the dry season. However, knowledge of greenhouse gas (GHG) emission from these rice based cropping systems is very limited. In the present study four rice based cropping systems was studied along with rice-rice rotation system as control in respect of GHG emission, yield potential and economic feasibility. Conventional plantation and fertilizer application methodology was followed for each crop. Methane (CH₄) and nitrous oxide (N₂O) flux from field plots were studied with conventional closed chamber method using gas chromatograph. CH₄ flux was recorded highest from rice-rice rotation plots (304.25 kg ha⁻¹). N₂O flux was recorded 1.02 kg ha⁻¹ from rice-rice rotation system during wet season. However, during wet season, higher N₂O flux (1.93 kg ha⁻¹) was recorded from rice-potato-sesame rotation plots. Annual N₂O flux was also recorded significantly low (3.42 kg ha⁻¹) from rice-rice rotation plots and high (6.19 kg ha⁻¹) from rice-chickpea-greengram rotation plots. Significantly lower annual grain yield was recorded from rice-rice rotation plots (9.25 Mg ha⁻¹) whereas it was 18.84 Mg rice eq ha⁻¹ from rice-potato-sesame rotation system. The global warming potential (GWP) of rice-rice rotation system was recorded significantly high (8.62 Mg CO₂ ha⁻¹) compare to plots with different rice based cropping systems. Computing all C-emission from cradle-to-grave, highest total C-cost was recorded from the rice-rice rotation system ($62.00 ha⁻¹). We have made an attempt to calculate the C-credit of different rice based cropping systems by considering the difference of C-cost with control. The study suggests that the rice-potato-sesame is most sustainable among different cropping system studied in terms of economic profit ($62.00 ha⁻¹). We have made an attempt to calculate the C-credit of different rice based cropping systems by considering the difference of C-cost with control. The study suggests that the rice-potato-sesame is most sustainable among different cropping system studied in terms of economic profit (1248.21 ha⁻¹) and C-credit ($38.60 ha⁻¹). The result of the study may be limited to the study region; however, the study has potential use in respect to the development of agriculture practice for adaptation to climate change.     

Modelling nitrogen cycles of farming systems as basis of site- and farm-specific nitrogen management

The paper describes a model designed for analysing interrelated nitrogen (N) fluxes in farming systems. It combines the partial N balance, farm gate balance, barn balance and soil surface balance, in order to analyse all relevant N fluxes between the subsystems soil–plant–animal–environment and to reflect conclusive and consistent management systems. Such a system approach allows identifying the causes of varying N surplus and N utilisation.The REPRO model has been applied in the experimental farm Scheyern in southern Germany, which had been subdivided into an organic (org) and a conventional (con) farming system in 1992. Detailed series of long-term measuring data are available for the experimental farm, which have been used for evaluating the software for its efficiency and applicability under very different management, yet nearly equal site conditions.The organic farm is multi-structured with a legume-based crop rotation (N₂ fixation: 83 kg ha⁻¹ yr⁻¹). The livestock density is 1.4 LSU ha⁻¹. The farm is oriented on closed mass cycles.The conventional farm is a simple-structured cash crop system based on mineral N (N input 145 kg ha⁻¹ yr⁻¹). Averaging the years 1999–2002, the organic crop rotation reached, with regard to the harvested products, about 81% (6.9 Mg ha⁻¹ yr⁻¹) of the DM yield and about 93% (140 kg ha⁻¹ yr⁻¹) of the N removal of the conventional rotation. Related to the cropped area, the N surplus calculated for the organic rotation was 38 kg ha⁻¹ yr⁻¹ versus 44 kg ha⁻¹ yr⁻¹ for the conventional rotation. The N utilisation reached 0.77 (org) and 0.79 (con), respectively. The different structure of the farms favoured an enhancement of the soil organic nitrogen stock (35 kg ha⁻¹ yr⁻¹) in the organic crop rotation and caused a decline in the conventional system (−24 kg ha⁻¹ yr⁻¹). Taking account of these changes, which were substantiated by measurements, N surplus in the organic rotation decreased to 3 kg ha⁻¹ yr⁻¹, while it increased to 68 kg ha⁻¹ yr⁻¹ in the conventional system. The adjusted N utilisation value amounted to 0.98 (org) and 0.69 (con), respectively.     

Triple tracks in CR-39 as the result of Pd–D Co-deposition: evidence of energetic neutrons

Since the announcement by Fleischmann and Pons that the excess enthalpy generated in the negatively polarized Pd–D-D₂O system was attributable to nuclear reactions occurring inside the Pd lattice, there have been reports of other manifestations of nuclear activities in this system. In particular, there have been reports of tritium and helium-4 production; emission of energetic particles, gamma or X-rays, and neutrons; as well as the transmutation of elements. In this communication, the results of Pd–D co-deposition experiments conducted with the cathode in close contact with CR-39, a solid-state nuclear etch detector, are reported. Among the solitary tracks due to individual energetic particles, triple tracks are observed. Microscopic examination of the bottom of the triple track pit shows that the three lobes of the track are splitting apart from a center point. The presence of three α-particle tracks outgoing from a single point is diagnostic of the ¹²C(n,n′)3α carbon breakup reaction and suggests that DT reactions that produce ≥9.6 MeV neutrons are occurring inside the Pd lattice. To our knowledge, this is the first report of the production of energetic (≥9.6 MeV) neutrons in the Pd–D system. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Origin of Metazoa: Sponges as Living Fossils

Geodia cydonium  , which code for proteins. The analyses of their deduced amino acid sequences allowed a molecular biological approach to solve the problem of monophyly of Metazoa. Molecules of the extracellular matrix/basal lamina, with the integrin receptor, fibronectin, and galectin as prominent examples, cell-surface receptors (tyrosine kinase receptor), elements of sensory systems (crystallin, metabotropic glutamate receptor), and homologs/modules of an immune system (immunoglobulin like molecules, scavenger receptor cysteine-rich, and short consensus repeats, rhesus system) classify the Porifera as true Metazoa. As living fossils, provided with simple, primordial molecules allowing cell-cell and cell-matrix adhesion as well as processes of signal transduction as known in a more complex manner from higher Metazoa, they also show peculiarities not known in other metazoan phyla. Tissues of sponges are rich in telomerase activity, suggesting a high plasticity in the determination of cell lineages. It is concluded that molecular biological studies with sponges as model will not only help to understand the evolution of Protoctista to Metazoa but also the complex, hierarchial regulatory network of cells in higher Metazoa.     

Molecular organization of excitatory chemical synapses in the mammalian brain

 Chemical synapses are highly specialized cell–cell junctions designed for efficient signaling between nerve cells. Distinct cytoskeletal matrices are assembled at either side of the synaptic junction. The presynaptic cytomatrix at the active zone (CAZ) defines and organizes the site of neurotransmitter release from presynaptic nerve terminals. The postsynaptic density (PSD) tethers neurotransmitter receptors and the postsynaptic signal transduction machinery. Recent progress in the identification and characterization of novel CAZ and PSD components has revealed new insights into the molecular organization and assembly mechanisms of the synaptic neurotransmission apparatus. On the presynaptic side, Bassoon and Piccolo, two related giant proteins, are crucially involved in scaffolding the CAZ. On the postsynaptic side, two families of multi-domain adaptor proteins, the MAGuKs (membrane-associated guanylate kinase homologs) and the ProSAP (proline-rich synapse-associated protein, also termed Shank) family members are thought to be major organizing molecules of the PSD.     

Fine tuning water quality regulations in agriculture to soil differences

Groundwater quality has been defined in terms of threshold values for nitrate (50 mg l⁻¹) and pesticides (0.1 μg l⁻¹ active substance). Variability in space and time, and cost and safety considerations have made it unattractive to verify water quality by repeated measurements. Proxy values have, therefore, been defined to characterise water quality. For nitrate, maximum allowable fertilisation rates have been specified and farmers have to apply the MINAS book-keeping system to keep track of their N-flows. For pesticides, listing of allowed pesticides functions as another proxy quality measure. Field tests and simulations on a Dutch farm demonstrated that water quality assessment using these proxy values does not correspond with direct assessment based on measurements and a comparison with the threshold values, which represent the true standard. A second problem is the generic character of the proxy methods, which do not reflect quite different nitrate and pesticide dynamics in different types of soil. These problems make the proxy approach quite problematic. We, therefore, propose the systematic introduction of information technology to be used for deriving soil-specific management practices that do not lead to an increase of the thresholds. Existing techniques for precision agriculture can be used, and the current registration of all parcels in The Netherlands in a geographical information system, including occurrence of different soil types, will be quite helpful. Such an information system on internet will allow better control than the current generic proxy systems and is likely to be quite motivating to farmers.     

Reconnecting crop and cattle farming to reduce nitrogen losses to river water of an intensive agricultural catchment (Seine basin,France): past,present and future

Nitrate and pesticide contamination of surface and groundwater has become a major problem in intensive farming regions in Europe, with nitrate concentrations reaching values above the standard defined in 2000 by the European Water Framework Directive. In the Seine basin, a major issue is the closure and abandonment of drinking-water wells, which force water managers and drinking-water producers to explore solutions for water resource protection. Organic farming has appeared as a credible alternative to conventional farming, and this study explores the potential of organic farming to reconcile agricultural production and water quality. On the basis of agricultural statistics, survey questionnaires and experimental data, the nitrogen soil surface balance (N-SSB) has been established at the scale of a small 104-km² catchment (The Orgeval sub-basin), representative of the intensive cash crop farming in the Seine basin. The N-surplus for arable land in specialized organic cash crop systems has been found to be half that of current conventional systems (15 kg N ha⁻¹ yr⁻¹ versus 30 kg N ha⁻¹ yr⁻¹, respectively). The N-yield in organic systems is 21% lower than in conventional systems, but total fertilization (mostly symbiotic N fixation) is also 26% lower. Whereas 2–3 years of forage legume (e.g., alfalfa) as a starter crop of the typical 7- to 10-year diversified rotation builds up N soil fertility and helps prevent weeds without pesticides, the existence of an outlet for this fodder production is a limiting factor for the economic sustainability and the environmental benefits of these farming systems. Therefore, we explored the possibility of a reconnection of livestock and crop farming systems in the Orgeval catchment, a traditional dairy farming and Brie cheese production region. We calculated the N-SSB for this type of a reconnected livestock and cropping system and found a value very close to the specialized organic cash crop system with full utilization of fodder production, leading to profitable animal production, essentially as milk in this farm design. This reconnected system is compared with the estimated situation in 1955 before separation of plant and livestock production. Furthermore, the N-SSB values were converted into infiltrating sub-root concentrations and used as a boundary condition to a biogeochemical model. Organic cropping and organic reconnected livestock cropping systems result in a 50% reduction of surface water nitrate concentrations, a surface water quality 20% better than that reconstructed for 1955, with an overall higher protein production.     

Disaggregated greenhouse gas emission inventories from agriculture via a coupled economic-ecosystem model

Estimates of regional greenhouse gas emissions from agricultural systems are needed to evaluate possible mitigation strategies with respect to environmental effectiveness and economic feasibility. Therefore, in this study, we used the GIS-coupled economic-ecosystem model EFEM–DNDC to assess disaggregated regional greenhouse gas (GHG) emissions from typical livestock and crop production systems in the federal state of Baden-Württemberg, Southwest Germany. EFEM is an economic farm production model based on linear programming of typical agricultural production systems and simulates all relevant farm management processes and GHG emissions. DNDC is a process-oriented ecosystem model that describes the complete biogeochemical C and N cycle of agricultural soils, including all trace gases.Direct soil emissions were mainly related to N₂O, whereas CH₄ uptake had marginal influence (net soil C uptake or release was not considered). The simulated N₂O emissions appeared to be highly correlated to N fertilizer application (R² = 0.79). The emission factor for Baden-Württemberg was 0.97% of the applied N after excluding background emissions.Analysis of the production systems showed that total GHG emissions from crop based production systems were considerably lower (2.6–3.4 Mg CO₂ eq ha⁻¹) than from livestock based systems (5.2–5.3 Mg CO₂ eq ha⁻¹). Average production system GHG emissions for Baden-Württemberg were 4.5 Mg CO₂ eq ha⁻¹. Of the total 38% were derived from N₂O (direct and indirect soil emissions, and manure storage), 40% were from CH₄ (enteric fermentation and manure storage), and 22% were from CO₂ (mainly fertilizer production, gasoline, heating, and additional feed). The stocking rate was highly correlated (R² = 0.85) to the total production system GHG emissions and appears to be a useful indicator of regional emission levels.     

Quantification and valuation of ecosystem services in diverse production systems for informed decision-making

The empirical evidence of decline in ecosystem services (ES) over the last century has reinforced the call for ES quantification, monitoring and valuation. Usually, only provisioning ES are marketable and accounted for, whereas regulating, supporting and cultural ES are typically non-marketable and overlooked in connection with land-use or management decisions. The objective of this study was to quantify and value total ES (marketable and non-marketable) of diverse production systems and management intensities in Denmark to provide a basis for decisions based on economic values. The production systems were conventional wheat (Cwheat), a combined food and energy (CFE) production system and beech forest. Marketable (provisioning ES) and non-marketable ES (supporting, regulating and cultural) ES were quantified by dedicated on-site field measurements supplemented by literature data. The value of total ES was highest in CFE (US$ 3142 ha⁻¹ yr⁻¹) followed by Cwheat (US$ 2767 ha⁻¹ yr⁻¹) and beech forest (US$ 2328 ha⁻¹ yr⁻¹). As the production system shifted from Cwheat - CFE–beech, the marketable ES share decreased from 88% to 75% in CFE and 55% in beech whereas the non-marketable ES share increased to 12%, 25% and 45% of total ES in Cwheat, CFE and beech respectively, demonstrating production system and management effects on ES values. Total ES valuation, disintegrated into marketable and non-marketable share is a potential way forward to value ES and ‘tune’ our production systems for enhanced ES provision. Such monetary valuation can be used by policy makers and land managers as a tool to assess ES value and monitor the sustained flow of ES. The application of ES-based valuation for land management can enhance ES provision for maintaining the productive capacity of the land without depending on the external fossil-based fertilizer and chemical input.     

Nutrient flows in small-scale peri-urban vegetable farming systems in Southeast Asia—A case study in Hanoi

In many peri-urban areas of Southeast Asia, land use has been transformed from rice-based to more profitable vegetable-based systems in order to meet the increasing market demand. The major management related flows of nitrogen (N), phosphorus (P), potassium (K), copper (Cu) and zinc (Zn) were quantified over a 1-year period for intensive small-scale aquatic and terrestrial vegetable systems situated in two peri-urban areas of Hanoi City, Vietnam. The two areas have different sources of irrigation water; wastewater from Hanoi City and water from the Red River upstream of Hanoi. The first nutrient balances for this region and farming systems are presented. The main sources of individual elements were quantified and the nutrient use efficiency estimated. The environmental risks for losses and/or soil accumulation were also assessed and discussed in relation to long-term sustainability and health aspects.The primary source of nutrient input involved a combination of chemical fertilisers, manure (chicken) and irrigation water. A variable composition and availability of the latter two sources greatly influenced the relative magnitude of the final total loads for individual elements. Despite relatively good nutrient use efficiencies being demonstrated for N (46–86%) and K (66–94%), and to some extent also for P (19–46%), high inputs still resulted in substantial annual surpluses causing risks for losses to surface and ground waters. The surplus for N ranged from 85 to 882 kg ha⁻¹ year⁻¹, compared to P and K which were 109–196 and 20–306 kg ha⁻¹ year⁻¹, respectively. Those for Cu and Zn varied from 0.2 to 2.7 and from 0.6 to 7.7 kg ha⁻¹ year⁻¹, respectively, indicating high risk for soil accumulation and associated transfers through the food chain.Wastewater irrigation contributed to high inputs, and excess use of organic and chemical fertilisers represent a major threat to the soil and water environment. Management options that improve nutrient use efficiency represent an important objective that will help reduce annual surpluses. A sustainable reuse of wastewater for irrigation in peri-urban farming systems can contribute significantly to the nutrient supply (assuming low concentrations of potential toxic or hazardous substances in the water). Nutrient inputs need to be better related to the crop need, e.g. through better knowledge about the nutrient concentrations in the wastewater and improved management of the amount of irrigation water being applied.     

Evaluation of the sustainability of swine manure fertilization in orchard through Ecological Footprint Analysis: results from a case study in Italy

Ecological Footprint Analysis (EFA) is an environmental accounting system, in physical unit, able to quantify the total amount of ecosystem resources required by a region or by a production process. This methodology is both scientifically robust and widely diffused for territorial and productive analysis. The application of EFA to agricultural systems are still uncommon and examples in the fruit sector rare.In this work a detailed application of EFA to an experimental trial in a commercial nectarine orchard in Piedmont (Italy) is presented. The field trial is focused on the evaluation of agronomical benefit of various kinds of swine manure for fertilizing orchards. Four productive systems were established from 2008: liquid slurry (LS), covered slurry (CS), solid fraction (SF), mineral nutrition (MN). All the environmental impacts of the four systems were quantified both directly on field and with extrapolations from farmer knowledge. As previous studies suggested, we considered not only the one-year field operations, but also the whole lifetime of the orchard. The environmental costs of each system are presented and related to each other on the basis of their relative footprint value.Results highlight almost the same ecological footprint for the three manure fertilized systems (LS, CS and SF) with average of 0.96 gha t⁻¹) and the highest ecological footprint can be found in the MN system (1.14 gha t⁻¹). Interesting remarks can be done comparing the contributions to the ecological footprint of the field operations related to fertilization in the four systems. In the manure fertilized systems the fertilizer contribution goes from 0.9% to 1.2% of the total ecological footprint; but in the MN system the fertilizer contribution is 6.6% of the total ecological footprint. Results support the hypothesis that internal recycle and connections among different systems increasingly resulted in high system benefit and sustainability.     

Decomposition of and nutrient release from ruminant manure on acid sandy soils in the Sahelian zone of Niger,West Africa

In ago-pastoral systems of the semi-arid West African Sahel, targeted applications of ruminant manure to the cropland is a widespread practice to maintain soil productivity. However, studies exploring the decomposition and mineralisation processes of manure under farmers’ conditions are scarce. The present research in south-west Niger was undertaken to examine the role of micro-organisms and meso-fauna on in situ release rates of nitrogen (N), phosphorus (P) and potassium (K) from cattle and sheep–goat manure collected from village corrals during the rainy season. The results show that (1) macro-organisms played a dominant role in the initial phase of manure decomposition; (2) manure decomposition was faster on crusted than on sandy soils; (3) throughout the study N and P release rates closely followed the dry matter decomposition; (4) during the first 6 weeks after application the K concentration in the manure declined much faster than N or P. At the applied dry matter rate of 18.8 Mg ha⁻¹, the quantities of N, P and K released from the manure during the rainy season were up to 10-fold larger than the annual nutrient uptake of pearl millet (Pennisetum glaucum L.), the dominant crop in the traditional agro-pastoral systems. The results indicate considerable nutrient losses with the scarce but heavy rainfalls which could be alleviated by smaller rates of manure application. Those, however, would require a more labour intensive system of corralling or manure distribution.     

Comparison of soil N availability and leaching potential,crop yields and weeds in organic,low-input and conventional farming systems in northern California

Increasing dependence on off-farm inputs including, fertilizers, pesticides and energy for food and fiber production in the United States and elsewhere is of questionable sustainability resulting in environmental degradation and human health risks. The organic (no synthetic fertilizer or pesticide use), and low-input (reduced amount of synthetic fertilizer and pesticide use), farming systems are considered to be an alternative to conventional farming systems, to enhance agricultural sustainability and environmental quality. Soil N availability and leaching potential, crop yields and weeds are important factors related to agricultural sustainability and environmental quality, yet information on long-term farming system effects on these factors, especially in the organic and low-input farming systems is limited. Four farming systems: organic, low-input, conventional (synthetic fertilizer and pesticides applied at recommended rates) 4-year rotation (conv-4) and a conventional 2-year rotation (conv-2) were evaluated for soil mineral N, potentially mineralizable N (PMN), crop yields and weed biomass in irrigated processing tomatoes (Lycopersicon esculentum L.) and corn (Zea mays L.) from 1994 to 1998 in California’s Sacramento Valley. Soil mineral N levels during the cropping season varied by crop, farming system, and the amount and source of N fertilization. The organic and low-input systems showed 112 and 36% greater PMN pools than the conventional systems, respectively. However, N mineralization rates of the conventional systems were 100% greater than in the organic and 28% greater than in the low-input system. Average tomato fruit yield for the 5-year period (1994–1998) was 71.0 Mg ha⁻¹ and average corn grain yield was 11.6 Mg ha⁻¹ and both were not significantly different among farming systems. The organic system had a greater aboveground weed biomass at harvest compared to other systems. The lower potential risk of N leaching from lower N mineralization rates in the organic and low-input farming systems appear to improve agricultural sustainability and environmental quality while maintaining similar crop yields.     

Soil carbon sequestration in tropical agroforestry systems: a feasibility appraisal

Agroforestry is recognized as a strategy for soil carbon sequestration (SCS) under the afforestation/reforestation activities, but our understanding of soil carbon (C) dynamics under agroforestry systems (AFS) is not adequate. Although some SCS estimates are available, many of them lack scientific rigor. Several interrelated and site-specific factors ranging from agroecological conditions to system management practices influence the rate and extent of SCS under AFS, so that generalizations tend to become unrealistic. Furthermore, widely and easily adoptable methodologies are not available for estimating the SCS potential under different conditions. In spite of these, there is an increasing demand for developing “best-bet estimates” based on the current level of knowledge and experience. This document presents an attempt in that direction. The appraisal validates the conjecture that AFS can contribute to SCS, and presents indicative ranges of SCS under different AFS in the major agroecological regions of the tropics. The suggested values range from 5 to 10 kg C ha^?1 in about 25 years in extensive tree-intercropping systems of arid and semiarid lands to 100–250 kg C ha^?1 in about 10 years in species-intensive multistrata shaded perennial systems and homegardens of humid tropics.     

Micro-flood (MF) technology for sustainable manufacturing operations that are coolant less and occupationally friendly

This paper presents a new technology for minimizing the use of metalworking fluids (MWFs) during the machining process that is atomization-less and occupational friendly. Micro-flood (MF) technology utilizes direct contact between the cutting tool and the MWF without the interaction of a gas medium. Experiments were conducted in high volume mass production environment turning HSLA (high strength low alloy) SAE 070Y steel. Machining performance and total air mass particulates were investigated in dry machining, Near dry machining (NDM) via atomized spray mist and MF technology. Open-atmosphere air monitoring indicated that total mass particulates behaved in an almost linear fashion with respect to gas atomization pressure, whereas the MWF flow rate demonstrated logarithmic trends in NDM applications using an atomized spray. Nozzle orientations directed upward into the air also produced higher mg/m³ concentrations (such as flank) than chip and rake face orientations that were directed down. Greater separation existed at higher gas atomization pressures, MWF flow rates and by changing the MWF type. At extreme limits, nozzle orientation affected mg/m³ concentration as much as 4–5 mg/m³ for water-miscible MWFs and 15–22 mg/m³ for non-water-miscible MWFs. Tool-life performance varied greatly among MWF type and flow rate, and in all cases MF technology performed better than NDM using an atomized spray mist. Direct and consistent MWF penetration to cutting zone using MF technology lowered tool-wear on the average of 12–75% compared to NDM at the same MWF flow rate. Compared to dry machining, NDM improved tool-wear on the average by 20–243%. In one case, tool-wear performance was improved by 616% at 0.15 mm using MF technology compared to dry machining at a nominal 0.925 mm tool-wear. Overall, a large mass reduction of particulates can be achieved employing MF technology that would have been unrealistic for an open-atmosphere machining environment employing an atomized spray mist. On the average, MF technology can maintain a total air mass particulate of less than 0.4 mg/m³ in the occupational work zone using MWF flow rates up to 1260 ml/h, regardless of the MWF classification. Atomized spray mist applications are capable meeting the 5 mg/m³ OSHA limit if MWF flow rates are less than 160 ml/h, air pressures are less than 0.137 MPa (20 psi) using water-miscible MWFs and air pressures are less than 0.0344 MPa (5 psi) using non-water-miscible MWFs.