Recycling Of Plant Nutrients Research Articles

Recycling plant nutrients in mixing several organic to serve hydroponic cultivation of vegetables and herbs, enhancing circulatory economy

Abstract Urine, rich in Nitrogen (N), Phosphorus (P), and Potassium (K), shows promise as a nutrient solution for cultivation, benefiting both nutrition and waste management. This study focuses on producing plant nutrients from human urine using biochar to absorb urine, soybeans meal residue, biogas waste, and fish heads & bones. These nutrients were evaluated against Vietnamese standards (TCVN). The nutrient solutions were tested on green mustard and Gynostemma pentaphyllum in a hydroponic system. Results indicated that the nutrient solution from desorbed human urine reached a maximum solute concentration of 2343.3 ppm after 15 days, surpassing other materials. Though slightly lower in total nitrogen compared to fish heads & bones (68.2 mg/l vs 69.5 mg/l), urine nutrients had higher total P2O5 and available potassium (171.8 mg/l and 592.5 mg/l, respectively). The urine solution performed comparably to soybeans meal residue and the inorganic Hoagland solution. Green mustard treated with urine solution had the best dry content, vitamin C, and low heavy metals. For Gynostemma pentaphyllum, the urine solution yielded the highest saponins, flavonoids, and minerals. Economic analysis of hydroponic models using urine solution showed significant promise, indicating its viability in hydroponics.

Replacing All Fossil Fuels With Nuclear-Enabled Hydrogen, Cellulosic Hydrocarbon Biofuels, and Dispatchable Electricity

Abstract We describe a roadmap using three sets of technologies to enable base-load nuclear reactors to replace all fossil fuels in a low-carbon world. The technologies integrate nuclear, wind, solar, hydroelectricity and biomass energy sources. Base-load nuclear reactors with large-scale heat storage enable dispatchable electricity to the grid. The low-cost heat storage enables buying excess wind and solar electricity to charge heat storage for later electricity production while providing assured generating capacity. Nuclear hydrogen production facilities at the scale of global oil refineries produce hydrogen to replace natural gas (gaseous fuel) as a chemical feedstock and heat source. Single sites may have tens of modular reactors produced in a local factory to lower costs by converting to a manufacturing model for reactor construction. Nuclear heat and hydrogen convert cellulosic biomass into drop-in liquid hydrocarbon biofuels to replace fossil-fuel gasoline, diesel, jet fuel, and hydrocarbon feed stocks for the chemical industry. External heat and hydrogen inputs increase the quantities of biofuels that can be produced per unit of cellulosic feedstock, thus assuring sufficient biomass feed stocks to replace all crude oil without major impacts on food and fiber prices. The biofuel production system enables the removal of large quantities of carbon dioxide from the atmosphere that is sequestered as carbon char in the soil while recycling plant nutrients (potassium, phosphorous, etc.) to assure agricultural and forest sustainability.

Isolation and characterization of salt-tolerant bacteria with plant growth-promoting activities from saline agricultural fields of Haryana, India

BackgroundSoil salinity has been one of the biggest hurdles in achieving better crop yield and quality. Plant growth-promoting rhizobacteria (PGPR) are the symbiotic heterogeneous bacteria that play an important role in the recycling of plant nutrients through phytostimulation and phytoremediation. In this study, bacterial isolates were isolated from salt-polluted soil of Jhajjar and Panipat districts of Haryana, India. The potential salt-tolerant bacteria were screened for their PGPR activities such as phosphate solubilization, hydrogen cyanide (HCN), indole acetic acid (IAA) and ammonia production. The molecular characterization of potent isolates with salt tolerance and PGPR activity was done by 16S rDNA sequencing. ResultsEighteen soil samples from saline soils of Haryana state were screened for salt-tolerant bacteria. The bacterial isolates were analyzed for salt tolerance ranging from 2 to 10%. Thirteen isolates were found salt tolerant at varied salt concentrations. Isolates HB6P2 and HB6J2 showed maximum tolerance to salts at 10% followed by HB4A1, HB4N3 and HB8P1. All the salt-tolerant bacterial isolates showed HCN production with maximum production by HB6J2. Phosphate solubilization was demonstrated by three isolates viz., HB4N3, HB6P2 and HB6J2. IAA production was maximum in HB4A1 (15.89) and HB6P2 (14.01) and least in HB4N3 (8.91). Ammonia production was maximum in HB6P2 (12.3) and least in HB8P1 (6.2). Three isolates HB6J2, HB8P1 and HB4N3 with significant salt tolerance, and PGPR ability were identified through sequencing of amplified 16SrRNA gene and were found to be Bacillus paramycoides, Bacillus amyloliquefaciens and Bacillus pumilus, respectively. ConclusionsThe salt-tolerant plant growth-promoting rhizobacteria (PGPR) isolated from saline soil can be used to overcome the detrimental effects of salt stress on plants, with beneficial effects of physiological functions of plants such as growth and yield, and overcome disease resistance. Therefore, application of microbial inoculants to alleviate stresses and enhance yield in plants could be a low cost and environmental friendly option for the management of saline soil for better crop productivity.

Circular economy fertilization: Phycoremediated algal biomass as biofertilizers for sustainable crop production

There is an urgent need to meet the demand of water and nutrients by their reuse and recycling to gratify sustainable food production system and resource conservation. Chlorella minutissima was found to be very effective in the removal of electrical conductivity (EC), total dissolved solids, phosphorous (P), potassium (K), ammonium, nitrate, biological oxygen demand (BOD5) and chemical oxygen demand (COD) of sewage wastewater. We tested the effects of phycoremediated algal biomass addition to soil in field plots of baby corn and spinach, on plant growth, yield and soil chemical properties. The application of 100% nitrogen (N) fertilizer by algal biomass lead to higher economic yield of spinach and baby corn than recommended dose of mineral fertilizers. The available N and P content in experimental plots applied with algae biomass as biofertilizers were significantly higher than other treatments. The soil enzymes, such as urease, nitrate reductase, and dehydrogenase were analysed during the cropping season of baby corn and spinach. The soil supplied with 100% N by algae biomass (C. minutissima) significantly (P < 0.05) increased the dehydrogenase activity in spinach grown soil. While the nitrate reductase activity in soil supplied with algal manure was maximum (0.13 mg NO2–N produced g−1 soil 24 h−1) and significantly higher than other treatments in baby corn grown soil. This study revealed that phycoremediation coupled with biofertilizers production from algae biomass is a recycling and resource conservation exercise to reduce eutrophication, recycling of wastewater, recycling of plant nutrients and improvement of the soil quality in circular economy fertilization.

Genetic Divergence in Sunnhemp [Crotalaria juncea (L.)

Background: Sunnhemp is a very important green manuring crop. The crop is utilized for various purposes like reducing soil erosion, improving soil properties and recycling plant nutrients. The knowledge regarding the crop is still not exploited, due to lack of research in this crop. So, the present study was conducted to know the extent of genetic diversity present in the crop. From the divergence analysis, it may be concluded that the genotypes belonging to different clusters separated by high estimated statistical distance may be used in the hybridization programme for developing high green biomass yielding sunnhemp varieties. Methods: A field experiment was conducted at the research farm of Department of Genetics and Plant Breeding, Navsari Agricultural University, Navsari, Gujarat with thirty sunnhemp genotypes to know the extent of genetic diversity by D2 analysis in a randomized block design during late Kharif 2017.Result: The analysis was conducted for D2 analysis and was concluded from D2 analysis that, the characters viz., days to 50% flowering, fresh weight of root nodules per plant, fresh weight of plant, root nodules per plant, leaf length, root length, dry weight of root nodules per plant, C: N ratio, internodes per plant, plant height and stem diameter contributed towards the genetic divergence. Traits like primary branches per plant and leaf area didn’t contribute towards genetic divergence. The thirty genotypes were grouped into seven clusters following Tocher’s method (Rao, 1952). The cluster III was largest having eleven genotypes. Cluster IV and cluster II was second largest which contained seven and five genotypes respectively. Cluster I and cluster V contained three and two genotypes respectively Cluster VI and VII had only one genotype. The intra cluster distance was more in cluster III and the inter cluster distance was maximum between cluster V and cluster VII.

Temporal Dynamics of Bacterial Communities in Soil and Leachate Water After Swine Manure Application.

Application of swine manure to agricultural land allows recycling of plant nutrients, but excess nitrate, phosphorus and fecal bacteria impact surface and drainage water quality. While agronomic and water quality impacts are well studied, little is known about the impact of swine manure slurry on soil microbial communities. We applied swine manure to intact soil columns collected from plots maintained under chisel plow or no-till with corn and soybean rotation. Targeted 16S-rRNA gene sequencing was used to characterize and to identify shifts in bacterial communities in soil over 108 days after swine manure application. In addition, six simulated rainfalls were applied during this time. Drainage water from the columns and surface soil were sampled, and DNA was extracted and sequenced. Unique DNA sequences (OTU) associated with 12 orders of bacteria were responsible for the majority of OTUs stimulated by manure application. Proteobacteria were most prevalent, followed by Bacteroidetes, Firmicutes, Actinobacteria, and Spirochaetes. While the majority of the 12 orders decreased after day 59, relative abundances of genes associated with Rhizobiales and Actinomycetales in soil increased. Bacterial orders which were stimulated by manure application in soil had varied responses in drainage waters over the course of the experiment. We also identified a “manure-specific core” of five genera who comprised 13% of the manure community and were not significantly abundant in non-manured control soils. Of these five genera, Clostridium sensu stricto was the only genus which did not return to pre-manure relative abundance in soil by day 108. Our results show that enrichment responses after manure amendment could result from displacement of native soil bacteria by manure-borne bacteria during the application process or growth of native bacteria using manure-derived available nutrients.

No‐Tillage had Warmer Over‐Winter Soil Temperatures than Conventional Tillage in a Brookston Clay Loam Soils in Southwestern Ontario

Core Ideas Tillage practices on surface soil temperature in the winter months were tested. No‐till soil responses slowly to changes of air temperature than tilled soil. Soil temperatures in winter were significantly greater in no‐till than tilled soils. Soil temperature affects soil microbial activity and hence impacts soil greenhouse gas (CO2, N2O, CH4) emissions and plant nutrient recycling. However, there is a lack of information on the effects of tillage practices on soil temperature in the surface soil layers in the winter months. Soil temperature and moisture in no‐tillage (NT) and fall moldboard plow (MP) of a Brookston clay loam in southwestern Ontario were measured on an hourly basis over the winter months (December to April) at soil depths (25, 75, and 150 mm) during 2012 to 2013, 2013 to 2014 and 2014 to 2015, respectively. Both soil temperature and moisture significantly varied with tillage practices over the winter months. The tillage and depth interaction occurred for soil moisture, but not soil temperature. Soil temperatures in December and January were significantly greater (+0.7°C) in NT than MP soil with a maximum divergence of 2 to 4°C in the 25‐mm depth for 4 to 5 d in January. In March and April, the soil temperature was about 0.7°C cooler for the NT than the MP soil. The soils were generally wetter in the NT than the MP plots and the difference was statistically significant from December to February. In general, the soil was warmer and wetter under NT than MP management in winter months for this clay loam soil whereas soils were cooler and wetter under no‐tillage in the spring.

Assessment of by-products of bioenergy systems (anaerobic digestion and gasification) as potential crop nutrient

Alternative fertilizer resources have drawn attention in recent times in order to cope up with ever increasing demand for fertilizer. By-products of bioenergy system are considered favourable as organic fertilizer due to their ability to recycle plant nutrients. Present study evaluates fertilizer suitability of by-products of two bioenergy systems viz. 3 types of anaerobic digestion by-products (digestate) from local surplus biomass such as cowdung, Ipomoea carnea:cowdung (60:40) and ricestraw:green gram stover:cowdung (30:30:40) and one gasification by-product (biochar) from rice husk. Digestates were assessed considering 4 different application options of each viz. whole, solid, liquid and ash from solid digestates. Digestate characteristics (organic matter, macronutrients, micronutrients and heavy metal content) were found to be a function of feedstock and processing (solid liquid separation and ashing). Ipomoea carnea based digestates in all application options showed comparatively higher N, P, K, NH4+-N, Ca, Mg, S and micro nutrient content than other digestates. Separation concentrated plant nutrients and organic matter in solid digestates, making these suitable both as organic amendments and fertilizer. Separated liquid digestate shared larger fraction of ammonium nitrogen (61–91% of total content), indicating their suitability as readily available N source. However, fertilizer application of liquid digestate may not match crop requirements due to lower total nutrient concentration. Higher electrical conductivity of the liquid digestates (3.4–9.3mScm−1) than solid digestates (1.5–2mScm−1) may impart phyto–toxic effect upon fertilization due to salinity. In case of by-products with unstable organic fraction i.e. whole and solid digestates of rice straw:green gram stover:cowdung digestates (Humification index 0.7), further processing (stabilization, composting) may be required to maximize their fertilizer benefit. Heavy metal contents of the by-products were found to be within the permitted range specified for organic fertilizer (vermicompost) in India. However, higher Al content of the digestates in whole, solid and ash phase (0.06–16.97gkg−1 fresh matter) can be a concern in acid soil which may cause Al toxicity.Understanding on agrochemical characteristics of bioenergy by–products with varying feedstock and application option is expected to promote their valorization opportunities considering user specific requirements. In the context of agriculturally dominant but energy deficient rural Indian scenario, integrated production of bioenergy and by-product based fertilizer could be very significant to meet the critical additional requirement of both energy and fertilizer.

Path Analyses of Grain P, Zn, Cu, Fe, and Ni in a Biosolids-Amended Dryland Wheat Agroecosystem.

Land application of biosolids is an effective means of recycling plant nutrients and is the primary method of biosolids reuse endorsed by the USEPA. One issue concerning biosolids application is the extent of the contribution of biosolids-borne plant nutrients to the overall crop concentration and uptake or removal of these nutrients. We studied the effects of biosolids application on wheat ( L.) grain P, Zn, Cu, Fe, and Ni concentrations and uptake (removal) at two dryland agroecosystem sites from 1993 to 2014. We hypothesized that biosolids would have the greatest impact on wheat grain and uptake compared with ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA)-extractable nutrient levels, soil pH, or soil organic C concentrations. We used path analyses in combination with multiple linear regression to differentiate the direct, indirect, and total effects of cumulative biosolids applications, soil AB-DTPA, soil pH, and organic C. Biosolids rates, applied biennially from 1993 to 2014 at the beginning of a wheat-fallow rotation, were 0, 2.24, 4.48, 6.72, 8.96, and 11.2 Mg ha. None of the parameters had significant direct, indirect, or total effects on grain concentrations. Biosolids applications had the greatest positive direct impact compared with AB-DTPA levels, soil pH, or soil organic C on P, Zn, Fe, and Ni uptake (removal), whereas AB-DTPA had the greatest positive direct impact on Cu uptake. Soil AB-DTPA, pH, and organic C directly affected some grain concentrations and cumulative uptake, but no consistent trends were noted. This pathway approach allowed differentiation between causation and simple correlation for the effects of cumulative biosolids applications on wheat P, Zn, Cu, Fe, and Ni cumulative uptake but did not provide these same results for grain concentrations.

Sanitizing Fecal Sludge for Reuse Using Wood Ash as an Additive

Wood ash has been widely used as an additive for excreta from dry compost toilets to sanitize it for reuse. However, there is dearth of quantitative information about its efficiency in sanitizing partially digested sludge from wet onsite sanitation systems. This paper presents findings of a series of two experimental studies to assess optimum wood ash dosages required to raise the pH of partially digested fecal sludge to sanitizing levels (pH &gt; 11) in a tropical climate. The study monitored the variation of pH of the sludge containing between 0 (control) and 180 g of ash per litre of sludge. Average initial pH and total solids of the sludge were 7.79 and 72 g/L respectively. Generally, the magnitude and rapidity of pH spike was correlated with the ash dosage (r = 0.988) and was statistically significant (p = 0.0015; Fcrit = 2.3157) among all dosages. Drastic increase in pH (from 7.81 to 11.60 ± 0.07) was recorded in the first 24 h for ash dosages between 140 g/L and 180 g/L, whereas dosages below 140 g/L had pH values less than 10. The difference in variation of pH between the first 24 h and the successive 24 h was statistically significant (P(T ≤ t)two-tail = 0.00; tcrit = 2.09). On the average, 97% of the overall pH increment within a 48-h monitoring period occurred in the first 24 h for the 140–180 g/L ash dosages. The optimum ash dosages are 7–15 times higher than reported lime dosages but ash provides a cheaper alternative than lime for recycling plant nutrients. Further studies on pathogen inactivation efficiency are ongoing.

Comparison between fertilizers and untreated sewage effluent as sources for nutrient recovery by wheat (Triticum aestivum)-soybean (Glycine max) cropping system

ABSTRACTRecovery and recycling of plant nutrients from municipal sewage effluent (SE) can reduce consumption of costly chemical fertilizers, besides reducing eutrophication of water bodies. Field experiment was conducted on Vertisol of central India for six years with the objective of quantifying recovery of major plant nutrients by aboveground biomass of wheat-soybean cropping system from untreated SE. Wheat crop was grown with irrigation (groundwater and sewage effluent) and fertilizer treatments; while soybean was grown without any treatments. Recoveries of nitrogen (N), phosphorus P) and potassium (K) by the aboveground biomass were considerably more from SE than from fertilizers and manures. Recovery of nutrients from SE was the highest by wheat grain for N and by soybean straw for P and K. Straw biomass of both the crops recovered about 31% N, 22% P and 69% K from SE, which can be recycled back into agricultural land of groundwater (GW) irrigated as well as rainfed area.

Agronomic Efficiency of Biosolid as Source of Nitrogen to Banana Plants

Sewage sludge (SS) or biosolid has been studied as source of nutrient for several different plant species. It also contributes to soil fertility recycling organic matter and plant nutrients. This followup work examines a three-year (2001–2004) field experiment designed to evaluate the response of banana plants (Cavendish subgroup) to the application of biosolid as source of nitrogen. The treatments consisted of control (mineral PK, no N), three rates of sludge, and two rates of mineral NPK fertilizer. Plant and soil N concentration, fruit yield, plant height, stem diameter, and foliar endurance index were measured. Fruit yield with mineral fertilization or sludge applications did not differ statistically(P&gt;0.05). Application of biosolid resulted in statistically significant higher agronomic efficiency(P&lt;0.05)in comparison to mineral fertilizers. The concentration of soil mineral nitrogen increased using mineral fertilizer or sludge until 0.80 m after three years of application. The effect of the source of N was smaller than the effect of the rate. Biosolid can be used as source of N for banana growers.

Effects of digestate from anaerobically digested cattle slurry and plant materials on soil microbial community and emission of CO2 and N2O

Anaerobic digestion of animal manure and crop residues may be employed to produce biogas as a climate-neutral source of energy and to recycle plant nutrients as fertilizers. However, especially organic farmers are concerned that fertilizing with the digestates may impact the soil microbiota and fertility because they contain more mineral nitrogen (N) and less organic carbon (C) than the non-digested input materials (e.g. raw animal slurry or fresh plant residues). Hence, an incubation study was performed where (1) water, (2) raw cattle slurry, (3) anaerobically digested cattle slurry/maize, (4) anaerobically digested cattle slurry/grass-clover, or (5) fresh grass-clover was applied to soil at arable realistic rates. Experimental unites were sequentially sampled destructively after 1, 3 and 9 days of incubation and the soil assayed for content of mineral N, available organic C, emission of CO2 and N2O, microbial phospholipid fatty acids (biomass and community composition) and catabolic response profiling (functional diversity). Fertilizing with the anaerobically digested materials increased the soil concentration of NO3− ca. 30–40% compared to when raw cattle slurry was applied. Grass-clover contributed with four times more readily degradable organic C than the other materials, causing an increased microbial biomass which depleted the soil for mineral N and probably also O2. Consequently, grass-clover also caused a ∼10 times increase in emissions of CO2 and N2O greenhouse gasses compared to any of the other treatments during the 9 days. Regarding microbial community composition, grass-clover induced the largest changes in microbial diversity measures compared to the controls, where raw cattle slurry and the two anaerobically digested materials (cattle slurry/maize, cattle slurry/grass-clover) only induced minor and transient changes.

What place for livestock on a re-greening earth?

Humanity is quickly encroaching upon the finite limits of the biosphere. As our numbers and appetites grow, food supplies become less secure, reserves of clean energy dwindle, pools of freshwater evaporate, the atmosphere's capacity to absorb our emissions diminishes and space for human and biotic habitat grows scarce. In response, some are now asking whether the biosphere can support our growing herds of domesticated livestock, notably ruminants. My aim in this review is to contemplate the place of these animals in a world in need of re-greening, in more ways than one. In addressing this objective, I advance the premise that the place of livestock is examined best from the vantage of ‘land’, broadly defined. Livestock have been implicated in many injurious processes: land use change, excess water use, nutrient excretion, fossil energy use, competition for food and emission of greenhouse gases. At the same time, they offer numerous benefits: producing food from human inedible sources, preserving ecosystem services, promoting perennials on croplands, recycling plant nutrients and providing social benefits. Thus livestock can be both stressors and benefactors to land and the aim of researchers should be to shift the net effect from stress to beneficence. To advance this goal, I offer seven questions, seen through the lenses of ‘systems’, ‘place’, ‘time’ and ‘community’, mostly to foster discourse. How do we better study whole systems? How do we better tune the systems to local land? How can we know long term consequences? How do we measure progress? How do we choose among trade-offs? How do we engage society? What will (or should) our successors’ livestock systems look like? Humans and their livestock are intertwined to such an extent that their symbiosis will not likely soon be severed. Livestock offer many benefits to human society and often their place in ecosystems can be ecologically justified. But that does not mean that all ways of raising them are beneficial, nor that they necessarily fit everywhere. In coming decades, researchers, in concert with practitioners, consumers and policymakers, will need to show creativity, foresight and courage to envision new ways of melding animals into our ecosystems, not only to minimize harm, but to advance their re-greening.This paper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors; K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.

Enzymatic activity and microbial biomass in soil amended with biofuel production byproducts

This study examined the effect of addition of byproducts generated from the biofuel industry on soil quality as measured by response of soil enzyme activity, microbial biomass C (MBC) and N (MBN) content and microbial quotient (MQ) to the addition of these materials over a short period of incubation. Byproducts of ethanol manufacture utilized included: wet distillers grain (WDG) and thin stillage (TS) that were applied at 3 rates of N (100, 200, and 400kgNha−1), whereas glycerol, a byproduct of biodiesel production, was applied at 3 rates of C (40, 400 and 4000kgCha−1) alone (G–N) or combined with 300kgNha−1 as urea (G+N). Urea and dehydrated alfalfa (DA) were applied at the same N rates as WDG and TS, as reference amendments. With the exception of TS and G–N, alkaline phosphatase activity was significantly enhanced by WDG, G+N, urea and DA addition, especially with low and medium rates. All amendments significantly increased dehydrogenase activity, but the rate effect was variable among all treatments. Protease activity was also enhanced by all amendment additions, with TS being less effective than others. All amendments with exception of TS significantly increased MBC, MBN and MQ. TS had no effect on these parameters, which is attributed to less organic carbon added relative to nitrogen in this amendment. Overall, addition of biofuel processing byproducts to soil stimulated microbial growth and enzyme activity; supporting their potential use as soil amendments to recycle plant nutrients and enhance soil biological activity.

Biosecurity and arable use of manure and biowaste — Treatment alternatives

The potential negative environmental impact of manure and biological waste (BW) can be minimised at a profit by recycling plant nutrients in the food chain. Current large-scale livestock production, epizootic diseases and increasing globalisation increase the need for biosecurity, to minimise the risk of disease transmission to the food chain. Arable use of manure and BW can inadvertently spread infectious diseases; opinion differs concerning the risk levels. To obtain general acceptance for arable use, a hygienically safe end-product is needed. This paper provides a detailed discussion of treatment alternatives for co-treatment, i.e., mixture before treatment of manure and BW. Composting, anaerobic digestion and ammonia treatment are the three options given. A decision support tool is also presented and discussed. Suitable treatment methods must combine biosecurity aspects with environmental, economic and nutrient recycling aspects to create a beneficial whole-farm approach.

Nutrient Assessment of a Dryland Wheat Agroecosystem after 12 Years of Biosolids Applications

Biosolids beneficial‐use programs effectively recycle plant nutrients when these waste materials are applied at an agronomic rate. Plant‐nutrient availability questions have arisen relating to Littleton and Englewood (L/E), Colorado Wastewater Treatment Plant bio‐solids applications to dryland wheat (Triticum aestivum L.)‐fallow agroecosystems. What is the long‐term estimated nitrogen equivalency (NE) of the biosolids? Can we estimate long‐term micronutrient distribution with continuous biosolids application? How does plant‐nutrient availability change with continuous application? Before each growing season we added biosolids at rates of 0 to 11.2 dry Mg ha−1 to plots arranged in randomized complete blocks with four replications per treatment. We found 12 years of application (6 applications to two sites in a 2‐yr wheat–fallow rotation) produced N equivalencies, based on wheat‐grain N uptake, of about 9 kg N Mg−1 biosolids. Estimated first‐year mineralization rates were ≈21 to 33%. Since P, Cu, Ni, and Zn grain removal were &lt;1% of biosolids‐applied concentrations, we estimated that tillage‐layer (top 20 cm of soil) concentrations could be predicted within 5% of actual total soil contents based on biosolids additions of these nutrients. Biosolids additions produced linear increases in NH4HCO3‐diethylenetriaminepentaacetic acid (AB‐DTPA) soil extract concentrations of P, Cu, Ni, and Zn. Soils initially were Zn deficient; biosolids application provided plant‐available Zn for dryland wheat. If biosolids agronomic rates were based on P instead of N availability, these soils could not receive biosolids. Also, if the Colorado Phosphorus Index was utilized, agronomic rates would continue to be based on N. Biosolids addition to dryland winter wheat according to N agronomic rates is a feasible method of recycling plant nutrients.

Cultural preferences in designing ecological sanitation systems in North West Frontier Province, Pakistan

Ecological sanitation has been shown to be economically feasible and environmentally sustainable. However, cultural factors affecting the choice of sanitation solutions have not yet been sufficiently investigated, particularly not in Muslim communities. To understand the perceptions of rural Muslim communities regarding alternative sanitation systems, members of households, key informants and women and men's focus groups in Machaki village in the district of Karak, North West Frontier Province (NWFP), were interviewed. A menu of both ecological and conventional sanitation options was put forward for consideration. All respondents were strongly opposed to the urine-separating latrines and in favor of flush toilets. They see any form of latrines as an age-old fashion, backwards and a matter of taboo, while flush toilets are considered prestigious and desirable. Muslim practices of anal cleansing together with the strict religious prohibition of contact with urine and faeces are factors influencing the reluctance towards latrines. The physical appearance of faeces and urine in latrines is repulsive to people. However, the material is less objectionable once it has disappeared in water and relocated to a treatment site. The rural community showed interest in the construction of improved sanitation consisting of flush toilets and an underground sewerage system and recycling of plant nutrients from urine and faeces through treatment in constructed wetlands. The study underlines the importance of incorporating cultural preferences in the planning of improved sanitation, particularly when designing low-cost ecological systems.

Wastewater management integrated with farming –an environmental systems analysis of a Swedish country town

Recycling of plant nutrients in sewage products to arable land is considered to be a step towards a more sustainable society. Sewage sludge is the predominant sewage fertiliser product available today, but the use of sewage sludge in agriculture has been questioned as regards hazardous substances. In this respect, blackwater from separating systems seems to better fulfil agricultural requirements regarding fertiliser products. The objective of this paper was to analyse the environmental impact and resource use in a life cycle perspective for three systems, each including both wastewater handling and agricultural production. In the reference system, food waste disposers were installed in houses. Milled food waste and wastewater were treated in a wastewater treatment plant and the sewage sludge was used for producing a soil conditioner. In the sludge utilisation system, food waste from households was composted, wastewater was treated conventionally and sewage sludge was used in oat production. In the blackwater system, toilet water from low-flush toilets and milled organic waste were digested together and spread in growing oats. Data on the wastewater system were derived from simulations by the substance-flow model URWARE/ORWARE. The blackwater system required slightly more primary energy than the other two systems. In particular, construction of storage facilities contributed considerably to energy use. The emissions of greenhouse gases and SO 2 were of the same magnitude for all three systems, while the eutrophying emissions were reduced significantly in the blackwater system. As regards NH 3 and NO X , the emissions were highest for the blackwater system. High substitution of mineral fertiliser, optimal spreading technique and well-designed collection and storage facilities were important factors for the environmental outcome in the blackwater system.

Growth response of &lt;i&gt;Amaranthus caudatus&lt;/i&gt; to earthworm casts and poultry manure application

The effect of earth worm cast on the physiomorphological differences of Amaranthus caudatus was studied in the green house of the Department of Agronomy, University of Ibadan for seven weeks in 1998. Earthworm casts were collected from soils cultivated with maize, cassava and oil palm fields and secondary forest. The result showed that performance of A. caudatus depended to some extent on earthworm casts rate (r=0.977) and casts produced from maize, oil palm crop fields and undisturbed forest, gave a yield advantage over control by 54.8, 19.4 and 64.5% respectively, while that from cassava fields gave yield disadvantage of 22.6%. In addition, growth performance was low on soils treated with cast, which also had a dry matter yield of 0.4 g pot-1 compared to 2.64 and 5.78 g pot-1 obtained from inorganic fertilizer and poultry manure respectively. It can therefore be concluded that application of earthworm casts from fields can play a good role in plant nutrient recycling and not at best solely in soil fertility amendment of degraded soils and as the only source of fertilizer for maximum A. caudatus production.Keywords: earthworm casts, poultry manure, Amaranthus caudatus, Ibadan, NigeriaGlobal Journal of Pure and Applied Sciences Vol. 11(4) 2005: 445-447