Mineral N-fertilization Research Articles

Effect of Soil Amendments on Growth, Seed Yield and NPK Content of Bottle Gourd (Lagenaria siceraria) Grown in Clayey Soil

The application of bio-fertilizers and organic fertilizer is considered a promising alternative for mineral fertilizers to decrease the production costs and environmental pollution with good yield. Hence, the present study aimed to evaluate the benefits of rice straw compost, humic acid and effective microorganism alone or in combination as an alternative to mineral-N fertilizer on the growth, foliar NPK content and yield of the local variety of bottle gourd. The study was carried out at Barramoon experimental farm, Dakahlia Governorate, Egypt, during the two summer seasons of 2012 and 2013. The experiment consisted of eight treatments of soil amendments and NPK fertilizers arranged in a complete randomized blocks design with three replicates. The study's treatments had significant effects on all studied traits in both seasons. The lowest values of these traits were recorded with the 75% recommended dose of NPK fertilizers with humic acid treatment. Whereas, the treatment of 75% recommended dose of NPK fertilizers in combination with rice straw compost, humic acid and effective microorganism had the highest values of foliage dry weight, number of leaves, stem length and number of fruits per plant as well as seeds weight per fruit, 100 seed weight and seed yield per plant and per hectare. So, this treatment could be recommended as an alternative method for bottle gourd fertilization. It might give the chance for increasing NPK-use efficiency and producing satisfactory and good seed yield with keeping the health and safety of human and environment.

Nitrogen dynamics and nitrous oxide emissions in a long-term trial on integrated soil fertility management in Western Kenya

Integrated soil fertility management (ISFM) is a concept that includes the management of organic matter in smallholder farming systems for sustainable intensification. To determine whether ISFM is also eco-efficient, we measured and simulated nitrogen (N)-dynamics and nitrous oxide (N2O) emissions in an ISFM long-term maize trial in Western Kenya. The total annual N-balance averaged over 10.5 years was negative for all continuous maize treatments that received only inorganic N-fertilizer. The N-balance was zero or positive when maize was grown in rotation with the green manure cover crop, Tephrosia candid, and/or to which 4 Mg ha−1 season−1 farm yard manure (FYM) added. These results thus substantiate the importance of organic matter management in tropical ecosystems. They also underpin that mineral N-fertilizer application alone does not guarantee agro-ecosystem sustainability, which should be considered in fertilizer (subsidy) policies. Treatments that included Tephrosia and FYM application emitted the largest amounts of N2O. Highest emissions (12.0 kg N2O–N ha−1) were simulated for the maize–Tephrosia rotation to which FYM and 30 kg ha−1 of mineral fertilizer N was added and 2 Mg ha−1 maize stovers retained. Such treatments had the highest N-emission intensity. The slope of the linear regression equation describing the N2O emission–N-input relationship of all considered treatments (0.023) was twice as high as the IPCC-Tier-1 emission factor. Maize–Tephrosia treatments had the highest seasonal maize yields. These were, however, not high enough to compensate for the inclusion of Tephrosia into the system as compared to growing maize continuously, compromising adoption by smallholder farmers.

Control of NO3 − and N2O emissions in agroecosystems: A review

Energized electron flows through biological systems sustain nature’s complexity. They drive bacterial, archaeal, and fungal oxidation–reduction processes and enable to introduce CO2 and N2 from the atmospheric pool. Electron flux-based food webs convert soil organic matter (SOM) in virgin forest and permafrost soils, over-fertilized agricultural land, grassland systems, compost/wastewater treatment plants, oceans, rain forests, savannahs, and forests of the temperate climate zones, and have their strategy adapted on the system in which they are active. Thus, the electron driving power is responsible in our industrializing world that carbon and nitrogen returns to the atmosphere presently with an annual N2O-N proportion of 0.5 to 4.2 terragrams (Tg) or an annual atmospheric N2O-N increase of 0.25 %. N2O is a 300-times more potent greenhouse gas than CO2. Nature’s water-soluble soil carbon (CH2O)/NO3 − ratio balancing is seen as a model of how N2O emissions could be kept in a tolerable range. Sub strategies beyond are (a) an annual 400–800 terragrams (Tg) photosynthate-C (90–95 % sugars) release into plant rhizospheres, (b) spot-wise N enriching animal excrement and wide C/N ratio litter fall distributions, (c) viral shunts or life shortcuts to supporting O2 consuming, N supplying, and denitrifying recycler communities, (d) subterranean organic–inorganic soil components mixing and O2 diffusion promoting NO3 − formation, and (e) the release of nitrification inhibiting compounds as neem, karanjin, or specific humic acids which help in controlling nitrate formation and denitrification. Soil microbial transport vehicles are fungal hyphae, plant roots, and subterranean animals. Through their activities, aerobic–anaerobic gradients in the soil crumb mosaics emerge. Plant root intertissue spaces, animal guts, and co-transported soil crumbs where under carbon-dominated CH2O/NO3 − ratios preferred microbes reside are mobile locations in well-aerated soils. In such reduction-equivalent surplus environments, denitrifying communities are forced to use during anaerobic respiration available nitrate-, nitrite ions, NO, and N2O economically. Though at carbon-dominated CH2O/NO3 − ratios more N2O is reduced to N2 than in nitrate surplus environments, a complete prevention of N2O emissions is not a reality and even not desirable from the climate point of view. After describing N2O formation and emissions from a compost pile, a municipal wastewater treatment plant, a constructed wetland, and mineral N-fertilizer, sewage sludge or nitrification inhibitor-stabilized N-fertilizer amended soils with their aerobic-anaerobic mosaics, this review tries to deduce exercisable CN (CH2O/NO3) ratio shaping and N2O emission lowering strategies for ecologists, agriculturists, and waste managers in our industrializing world.

EFFECT OF COMPOST FROM BY-PRODUCT OF THE FISHING INDUSTRY ON CROP YIELD AND MICROELEMENT CONTENT IN MAIZE

A pot experiment was conducted to compare the effects of compost from fish waste with mineral and manure fertilization on the yield and chemical composition of the overground parts of maize (Zea mays L.). The experiment comprised two series: I – composts at a dose of 1 g of compost per pot, and II – composts with 0.5 g of urea. The treatments were conducted on the following types of composts: compost 1: fish waste (80% d.m.), sawdust (20% d.m.); compost 2: fish waste (80% d.m.), straw (20% d.m.); compost 3: fish waste (80% d.m.), bark (20% d.m.); compost 4: fish waste (79.3% d.m.), sawdust (19.7% d.m.), lignite (1% d.m.); compost 5: fish waste (79.3% d.m.), straw (19.7% d.m.); lignite (1% d.m.); compost 6: fish waste (79.3% d.m.), bark (19.7% d.m), lignite (1% d.m). The contents of Ni, Zn, Cr, Cu and Cd were determined in an air-acetylene flame using the flame atomic absorption spectrophotometric method. The average crop yield of the overground parts of maize in the series without additional mineral fertilization and with mineral N-fertilization was higher compared to objects without mineral N-fertilization. The highest crop yield was noted in the case of compost containing fish waste and straw with addition of lignite and with bark and lignite. The addition of lignite to the compost mass in the series with mineral Nfertilization had stronger influence on the content of cadmium, chromium, nickel and zinc in the overground parts of maize.

Determination of Biological Nitrogen Fixation Induced N2O Emission from Arable Soil by Using a Closed Chamber Technique

Intensive use of mineral N fertilizers and organic amendments has resulted in higher N2O emissions. A growing worldwide concern for these problems has motivated researchers, environmentalists, and policy makers to find alternatives to overcome such losses. Biological nitrogen fixation is one of many natural biological approaches to minimize the use of fertilizers and to possibly reduce N2O emissions. A greenhouse study was performed by growing inoculated and noninoculated soybean seeds (Glycine max (L.) Merr.) in PVC columns. The objective was to measure the contribution ofBradyrhizobium Japonicumand mineral-N fertilizer to promoting N2O emission. A closed chamber technique was used for gas sampling. N2O measurements were carried out shortly after nodulation.Bradyrhizobium Jopanicuminduced N2O cumulative (121.8 μg kg−1) fluxes of inoculated seeds was significantly (α= 0.05) higher than those of mineral N fertilized treatment (NIS) and the control (bare soil). Total nitrogen content of the roots and seeds was not affected by inoculation. Total carbon ( 42.1 ± 0.1%), total nitrogen (3.1 ± 0.1%), and crude protein (19.9 ± 0.7%) contents of leaves of the inoculated seeds were significantly higher than those of noninoculated seed treatments. N2O fluxes significantly increased with high dissolved organic carbon content (70.77 ± 3.99 mg L−1) at R3 and at R8 stages whenNO3-(39.60 ± 0.94 mg L−1) concentrations were high.

Effect of application timing and grass height on the nitrogen fertilizer replacement value of cattle slurry applied with a trailing-shoe application system

This study investigated the effect of using a trailing-shoe system to apply cattle slurry, under different conditions of grass height (low [LG]: freshly cut sward [4–5 cm height] vs. high [HG]: application delayed by 7–19 d and applied to taller grass sward [4–11 cm] height) and month of application (June vs. April), on the nitrogen fertilizer replacement value (NFRV) and apparent N recovery (ANRS) of cattle slurry applied to grassland. NFRV was calculated using two methods: (i) NFRVN based on the apparent recovery of slurry-N relative to that of mineral-N fertilizer; and (ii) NFRVDM based on DM yield. The effect of applying slurry into HG swards, relative to LG swards, decreased the DM yield by 0·47 t ha−1 (P ≤ 0·001), N uptake by 5 kg ha−1 (P = 0·05), ANRS by 0·05 kg kg−1 (P = 0·036), NFRVN by 0·05 kg kg−1 (P = 0·090) and NFRVDM by 0·11 kg kg−1 (P < 0·001). It was concluded that the main factor causing these decreases with HG, compared with LG applications, was wheel damage affecting subsequent N uptake and growth of the taller grass sward.

Recoveries of 15N-labelled fertilizers (chicken manure, mushroom compost and potassium nitrate) in arable topsoil after autumn application to winter cover crops

Frequently, organic fertilizers are applied to maintain or to increase soil fertility and plant yields. However, as the N availability of organic fertilizers is difficult to calculate, applied fertilizer N may be subject to loss, particularly through leaching. The objective of this study was to evaluate the fate of fertilizer N from two common organic manures (chicken manure, mushroom compost) in arable topsoil during one winter cover cropping and cropping season. For this purpose, 15N-labelled fertilizers were produced by feeding chicken with 15N-labelled maize pellets and by incubating a mushroom substrate with 15N-labelled mineral fertilizer, respectively. Thereafter, the 15N uptake by a mustard winter cover crop, its release to the main crop (sugar beet), and its retention in soil were investigated in two differently textured soils under otherwise identical conditions during a period of 400 days. Mineral K15NO3 fertilizer served as control. In the surface soil (0–10cm), only 20–40% of the applied 15N was recovered after the first 50–60 days, which was the period of mustard growth. Thereafter, the amount of 15N recovered in the soil increased again until day 259, reflecting the re-release of the fertilizer N from the winter cover crop in all treatments. The fertilizer N recovery in the winter cover crop itself was highest for mushroom compost (60%), followed by mineral fertilizer (50%) whereas it was almost not detectable for chicken manure (3%). Soil texture did not affect the overall retention of the fertilizer N in soil, and even after 400 days we recovered 67% of the fertilizer N from mushroom compost, 37% from chicken manure and 28% from the mineral fertilizer (0–30cm). The following main crop, sugar beet, still utilized between 7 and 13% of the initial fertilizer addition from the previous summer. We conclude that mustard winter cover cropping after organic fertilization is efficient in retaining available N during winter time, and mushroom compost is better than mineral N-fertilizer and chicken manure in respect of being a slow and sustainable N fertilizer source for the plants at reduced N losses.

Partitioning of N in growing plants, microbial biomass and soil organic matter after amendment of N-ammonoxidized lignins

Nitrogen (N) availability is a crucial factor for maintaining soil productivity, but application of mineral N-fertilizer raises environmental concerns. Based on earlier humification models, ammonoxidized technical lignins were suggested as potential slow N-release fertilizers. In order to obtain first insights on their efficiency as plant fertilizer, their impact on soil organic matter composition and stability, and its role within the N cycle in soils, pot experiments were performed in which perennial ryegrass (Lolium perenne L.) was grown on a typical Andalusian soil (Luvisol, chromic) after amendment of N-lignins highly enriched in 15N (Sarkanda and Indulin ammonoxidized lignins) for 75 days. For comparison, the incubation study was also carried out with soils with and without 15NO3 fertilization. Among these experiments, the addition of K15NO3 resulted in the greatest aboveground plant production. However, most of the growth occurred during the first 28 days. Thereafter, a fast decrease of the bioavailable N pool occurred. The application of ammonoxidized lignins altered the pH and electrical conductivity of the soil. At higher concentrations a retardation of seed germination was evidenced. After 75 days, the plant shoots from the pots amended with 15N-Indulin and 15N-Sarkanda accumulated 8% and 20% of the initial 15N present in the amended soils at the beginning of the experiment (15N0). In the 15N-Indulin pots the N was efficiently sequestered from fast release or leaching and most of 15N0 remained in the soil (64%). In contrast, the 15N-Sarkanda pots showed a lower efficiency in N retention. After 28 days of incubation only 42% of 15N0 was retained in the 15N-Sarkanda amended soil, but more than 17% was recovered within the soil microbial biomass. Until the end of the incubation time, the 15N0 detected in the soil microbial biomass decreased to less than 3%, whereas the amount associated with the soil matrix maintained around 37%. The notable increase of 15N in the above-ground plant production (20%) evidences an efficient use of 15N released from the 15N-Sarkanda for plant production. Solid-state nuclear magnetic resonance (NMR) spectroscopy revealed that the 15N of the added 15N-lignins was quickly transformed into peptide-type N, most tentatively of microbial origin, without major alteration of the lignin backbone. This indicates that in soils the competition for nutrients favors N immobilization into biomass with its subsequent sequestration within recalcitrant biopolymers rather than its stabilization via covalent binding to lignins.

N2O emission from a loamy sand Spodosol as related to soil fertility and N-fertilizer application for barley and cabbage

The aim of this field study was to compare N2O emission from loamy sand Spodosol of North-Western Russia with two levels of soil fertility. Plots with soils of low fertility (LF) and high fertility (HF) were divided into two subplots receiving high and zero inputs of mineral N-fertilizer. Barley and cabbage were grown on the subplots. Direct N2O fluxes were measured and cumulative N2O fluxes calculated for each crop grown on different subplots during the growing season of 2006. The differences in cumulative N2O fluxes from the LF and HF soils were significant for barley and insignificant for cabbage when no mineral N-fertilizer was added. The application of mineral N-fertilizer resulted in a significant increase in cumulative N2O flux from both soils with barley but not with cabbage. The amount of N2O emitted from the soil per crop yield unit was significantly higher for the LF soil than for the HF soil for both of the studied crops. The results showed that in relatively dry growing seasons it would be better to use the HF Spodosol rather than the LF one to grow crops as the HF soil, in spite of the higher cumulative N2O flux, produced less N2O per yield unit.

Carbon and nitrogen dynamics in a Brazilian soil-pasture system irrigated with treated sewage effluent

The use of treated sewage effluents for agricultural irrigation represents a promising agronomic-environmental-economic practice; however, little is known about its effects on chemical attributes of tropical soils. This research project aimed at evaluating the effects of irrigation with secondary-treated sewage effluent (STSE) and various application rates of mineral-N fertilizer (MNF) on total carbon (TC) and nitrogen (TN) contents, and ammonium (NH4 +-N) and nitrate (NO3 --N) concentrations in a tropical soil-pasture system. The experimental field was cropped with Tifton 85 bermudagrass, over two years. The treatments were: T1 (control), irrigation with potable water and addition of MNF, 520 kg ha-1 year-1; T2-T5, irrigation with STSE (31.9 mg L-1 of total-N) and addition of MNF: 0, 171.6, 343.2, and 520 kg ha-1 year-1, respectively. Soil TC and TN concentrations normally decreased over the experimental period. In general, higher NO3 --N concentrations in the soil solution were found for treatments rece...

RESPONSE OF CANOLA PRODUCTIVITY AND QUALITY TO BIO- ORGANIC AND INORGANIC N – FERTILIZERS

A field experiment was conducted at the Ismailia Agricultural Research Station during the two growing seasons of 2008-09 and 2009-10, to study the separate application of biofertilizers, organic manure (0, 5, and 10 tons/fed) and mineral N-fertilizer (0, 40, 60, and 80 kg N/fed) and their combined application on plant growth, yield and its components, seed quality (oil and protein content) of canola plants (c.v. Serw 4). Split-spilt plot design with three replicates was used. Results indicated that the individual application of biofertilizer, organic manure (10 ton/fed) and N-fertilizer at rate 80 kg N/fed caused 5.1 and 4.9 %, 18.5 and 16.6% and 40 and 40.3 % in seed yield during two seasons, respectively over control. Likewise, the interaction among the used levels of mineral N-fertilizer and bio-organic fertilizer revealed significant effect in both studied seasons for all investigated characters of canola plants. In this respect, it is worthy to note that the treatment of 80 kg N/fed of the recommended dose of N did not statistically differ from that of 40 kg N/fed of N fertilizer plus biofertilizer and 10 tons/fed compost manure. As for seed quality of canola, it was also found that protein content was increased by application of bio, organic, and inorganic N-fertilizer. However oil content was decreased by nitrogen application but it was increased with addition of biofertilizer and compost manure. Seed protein and oil content were significantly increased by the integrated fertilizers applications. This mean that inoculated seed of canola plant with biofertilizer containing nitrogen fixer bacteria plus addition of compost manure at 10 ton/fed., substitute half of the recommended dose from the used mineral nitrogen fertilizer.

RESPONSE OF WHEAT GROWN ON SANDY CALCAREOUS SOILS TO ORGANIC MANURES AND SULFUR APPLICATION

The aim of the present investigation was to improve the productivity of wheat grown on the sandy calcareous soil of Arab El-Awammer Experimental Station, Assiut governorate through using organic matter, elemental Sulphur application, and the suitable level of mineral N-fertilization. Three field experiments were conducted for this purpose; two in the winter season 2004/2005 and the third in season of 2005/2006. The experiments tested different forms of organic manures: Farm yard manure (FYM), chicken manure (CM) and Town wastes (TW) at rate of 100 kg N/fed and liquid Vinasse at 5 ton/fed), different levels of mineral N-fertilization (60, 90, 120, 150 kg N/fed), and Sulphur application at different rates (200, 300, 400, 600 kg/fed). Plant growth, and wheat yields (grain, straw, total) and N, P plant uptake were determined, also soil pH, EC, and available P after 30 and 60 days from sowing and at harvest of crop were measured. The obtained results showed that supplementation of organic matter, in any form, improved plant growth and induced significant or highly significant increases in wheat grain yield, 39.0, 36.1, 32.0 and 14.3 % with (TW), (FYM), (CM) and Vinasse, respectively. Sulphur application in the range of 300-400 kg/fed, alone or with organic manures had significant beneficial effects on increasing wheat growth, N and P plant uptake, and yields obtained (between 11.50 to 12.99 % increases in grain yields), and induced significant reductions in soil pH and increases in available P. The application of S with organic manures, especially (TW), had a synergetic effect on increasing grain yield. The optimum economic rate of mineral N fertilization for wheat grown on this sandy calcareous soil is 90 kg N/fed. This is in addition to an amount of TW as a soil conditioner equal to 100 kg N/fed.

Effects of organic and mineral fertilizer nitrogen on greenhouse gas emissions and plant-captured carbon under maize cropping in Zimbabwe

Optimizing a three-way pact comprising crop yields, fertility inputs and greenhouse gases may minimize the contribution of croplands to global warming. Fluxes of N2O, CO2 and CH4 from soil were measured under maize (Zea mays L.) grown using 0, 60 and 120 kg N hm-2 as NH4NO3-N and composted manure-N in three seasons on clay (Chromic luvisol) and sandy loam (Haplic lixisol) soils in Zimbabwe. The fluxes were measured using the static chamber methodology involving gas chromatography for ample air analysis. Over an average of 122 days we estimated emissions of 0.1 to 0.5 kg N2O-N hm−2, 711 to 1574 kg CO2-C hm−2 and−2.6 to 5.8 kg CH4-C hm−2 from six treatments during season II with the highest fluxes. The posed hypothesis that composted manure-N may be better placed as a mitigation option against soil emissions of GHG than mineral fertilizer-N was largely supported by N2O fluxes during the wet period of the year, but with high level of uncertainty. Nitrogen addition might have stimulated both emissions and consumption of CH4 but the sink or source strength depended highly on soil water content. We concluded that the application of mineral-N and manure input may play an important role with reference to global warming provided the season can support substantial crop productivity that may reduce the amount of N2O loss per unit yield. Confidence in fluxes response to agricultural management is still low due to sporadic measurements and limited observations from the southern African region.

Residual effects of pig slurry and mineral nitrogen fertilizer on irrigated wheat

The residual effects of pig slurry beyond the year of application have yet to be clearly quantified to determine if it is possible to reduce N fertilizer rates for the subsequent crops. The objective of this study was to assess the residual effects of pig slurry (PSRE) and mineral N fertilizer (MRE) applied to maize ( Zea mays L.) with respect to the subsequent wheat ( Triticum aestivum L.). A wheat crop was established in the Ebro valley (Northeast Spain) following a 6-year maize monoculture (2002–2007). The maize crops had been annually fertilized with a combination of three pig slurry rates (0, 30, and 50 m 3 ha −1) and three mineral N rates (0, 100, and 200 kg N ha −1) commonly applied by farmers in the region. The soil mineral N levels before wheat sowing ranged from 94 to 609 kg N ha −1 and increased as pig slurry and mineral N applications to maize increased. The PSRE were high and ranged from 2287 to 3796 kg ha −1 for wheat grain yield and from 36 to 84 kg N ha −1 for grain-N uptake. Results suggested that the PSRE would mainly originate from the carry-over of unused mineral N. Mineralization of the organic N applied with pig slurry, at rates based on European Union Nitrates Directive, contributed with further residual N effects and would allow farmers to reduce N fertilization of wheat about 30 kg N ha −1. A reduction in the typical N rates applied to maize along with additional N fertilization of wheat is necessary to maximize crop profitability and reduce the risk of water pollution with nitrates.

EFFECT OF GRAIN BIOINOCULATION ON WHEAT YIELD AND ITS COMPONENTS UNDER APPLYING DIFFERENT LEVELS OF NITROGEN FERTILIZATION

A field experiment was conducted at El-Wanysa village, Itsadistrict, El-Fayoum Governorate, during the two successive winterseasons of 2008/2009 and 2009/2010 to investigate the influence ofapplied different mineral nitrogen levels and grain bio-inoculationwith, Azotobacter and /or Azospirillum and their interactions on wheatgrowth, yield and its attributes as well as N-uptake of either wheatgrain or straw and grain protein content. A split plot design with threereplicates was used. The obtained results could be summarized asfollows:The results showed significant increases in plant dry weight,plant height, spike length, 1000-grain weight, grain or straw yield/fed.N-uptake by straw or grain and of grain protein content either byincreasing the rate of mineral nitrogen or with grain inoculation by thetested N2-fixers. In addition, the dual grain inoculation withAzotobacter and Azospirillum performed significantly greater followedby single inoculation with either Azospirillum or Azotobacter. At anylevel of N-fertilizer, the inoculated treatments gave much higher strawand grain yields than the uninoculated one.From the economical point of view, it could be concluded that,the amount of mineral N-fertilizer could be reduced by using grain bioinoculation, which in turn increases soil fertility as well as, minimizesthe production cost and environmental pollution, which can occur bythe excess use of chemical fertilizers.

SOIL AND PLANT NITROGEN DYNAMICS OF A TOMATO CROP UNDER DIFFERENT FERTILIZATION STRATEGIES

A field experiment was conducted in 2007 to investigate the effects of the N fertilizer source on the soil and plant N dynamics of a tomato crop grown in a sandy loam soil. The fertilization treatments were: mineral N-fertilization applied by fertigation (TM); organic N-fertilization (TO) with compost obtained from the organic fraction of urban waste (OFUW); and a combined treatment (TC) with half organic and half mineral N. Compost was incorporated in November 2006. Plants were drip irrigated with well water. The nitrate concentrations in the irrigation solutions were determined on a weekly basis. Soil samples were taken before planting and at harvest from depths of up to 90 cm in order to determine moisture and N-NO 3 levels. The estimated amounts of total N-NO 3 - available in the different treatments, including the initial content in the 0-90 cm soil layer, were 560 (TC), 570 (TO) and 610 (TM) kg N ha -1 . The N contents of plants sampled on three occasions during the growing period and those of marketable fruits were also analyzed. Total marketable yield was determined at the end of the harvest period. The EU-Rotate_N model was used to predict the effects of the applied treatments. The model was calibrated using data from a previous experiment. No differences between treatments were observed with respect to yield or N content in marketable fruits. The amount of N left in the field at the end of the cropping period was significantly lower in TO than in TC and TM. Simulated plant growth, marketable yield and N uptake were similar to observed data. N leaching predicted by the model for the TM treatment was 50% higher than in the TC and TO treatments. However, an underestimation of residual N contents was found in all treatments. It was concluded that tomato fertilization with compost obtained from the OFUW could offer a suitable strategy for reducing N leaching without affecting yield when there is sufficient mineral N available throughout the growing period. The EU-Rotate_N model may be a valuable tool for evaluating N fertilizer practices for tomato crops.

Soil exchangeable cations, sugarcane production and nutrient uptake after wastewater irrigation

Wastewater irrigation may benefit agricultural crops with water and essential nutrients (mainly nitrogen), also affecting soil chemistry. The effects of effluent irrigation on yield, stalk nutrient uptake and on soil chemistry over 16 months were studied in a sugarcane (Saccharum spp.) crop growing on an Oxisol in Lins, State of São Paulo, Brazil. Irrigated plots received 50% of the recommended mineral-N fertilization and 100, 125, 150 or 200% of the crop water demand, while control plots received neither additional N nor water. The high sodium content of effluent resulted in Na inputs as high as 6.2 t ha-1, along with 1497 kg N ha-1 and 628 kg K ha-1. All the effluent plots except the T125 treatment had higher yields (up to 247 t ha-1) than the control (153 t ha-1). Significant amounts of N (up to 597 kg ha-1) and K (up to 546 kg ha-1) were exported by the plant harvest. Additions of nutrients and Na via irrigation were not compensated by stalk growth, causing a low recovery of N, P, Ca, Na, and showing the relative over N fertilization of the crop. Changes in soil pH, H + Al, Ca, Mg and K were small, whereas Na accumulated over time with irrigation. The treated wastewater irrigation is expected to gain increased importance, requiring careful considerations involving the adequate balance between nutritional inputs via irrigation and optimal plant productivity requirements.

USE OF SOME ORGANIC MATERIALS AS A FOLIAR APPLICATIONS IN RICE PRODUCTION AND REDUCTION OF MINERAL N-FERTILIZERS

Two field experiments were conducted at Sakha Agriculture Research Station in two successive seasons of 2005 and 2006 to evaluate the effect of some organic compounds as a foliar applications (2000 ppm citric acid and 10% methanol) separately or together with adding three nitrogen rates to the soil (30, 45 and 60 kg N fed-1) on rice production and reduction of mineral N-fertilizers. The obtained data generally showed that the addition of such organic compounds with 60 or 45 kg N fed.-1 produced significantly higher yield and yield components. Also data indicated that using these organic compounds with 45 kg N fed.-1 significant increased N, P and K content in rice plants. The percentage of protein content in rice grains increased by using these organic compounds. Using these organic compounds leads to decreased of mineral N-fertilizer applications about 25% thus reducing pollution of the environment.

RESPONSE OF WHEAT (Triticum aestivum L.) TO DIFFERENT MINERAL NITROGEN LEVELS AND INOCULATION WITH N2-FIXING BACTERIA

Two field experiments were carried out on a sandy loam soil at El-Tahrir Province Sector during two successive winter-growing seasons of 2005/2006 and 2006/2007 to study the response of wheat growth, yield and some yield components to inoculation with N2-fixing bacteria under different levels of mineral N-fertilization using sprinkler irrigation system. Wheat seeds (Triticum aestivum L., cv. Sids 1) were inoculated shortly before planting by Azorhizobium caulinodans, Gluconacetobacter diazotrophicus, Bacillus polymyxa as a single treatment or seeds inoculated with mixture of such strains. The tested bacterial strains were interacted with different levels of mineral N fertilizer (zero, 25, 50, 75 and 100 kg N/fed). Nitrogen fertilizer was added in the form of ammonium sulphate (20.5% N). Superphosphate (15.5% P2O5) and potassium sulphate (48% K2O) were added at rates of 200 kg/fed and 100 kg/fed, respectively as a recommended dose. The experimental design was a split plot design with three replications and the plot size was 6 m2. Regarding the response to inoculation with N2-fixing bacteria, results of both tested seasons showed that there are significant increases in all wheat vegetative growth, yield and some yield components due to inoculation with any tested diaztotrophs. However, using mixture strains followed by Bacillus polymyxa treatments surpassed other inoculated treatments or uninoculated ones. As general, a comparison between inoculants on all wheat growth aspects as well as wheat yield and its yield components showed the order: Mixture> Bacillus polymyxa> Gluconacetobacter diazotrophicus> Azorhizobium caulinodans> uninoculated treatment. The response of wheat growth, yields and yield components to increasing application rate of mineral N fertilizer was significant. Using higher rates of mineral N-fertilizer (100 kg N/fed) showed higher values of all tested parameters under investigation in both seasons. Taking the interaction between inoculation and different N fertilizer levels into consideration, the best results of wheat growth, yield and its components were achieved when wheat plants inoculated with mixture strains followed by Bacillus polymyxa in combination with 50 kg N/fed, which showed a positive response and gave values nearly similar to or higher than using the full dose of mineral N-fertilizer (100 kg N/fed). This trend was true in both tested seasons. From these results it could be concluded that the inoculation with N2-fixing bacteria, particularly in a mixture form, may be acting as a good practice for enhancing wheat growth aspects and improving the crop yield and yield components. Also, it could compensate 50% of the recommended inorganic-N used in sandy loam soil with no decrease in wheat quantity or quality.

Assessment of multi-strain PGPRs biofertilization as compared to sole-strain or mineral n-fertilization on wheat plants grown in clayey soil in Egypt

A field experiment was performed at Malawi Station, Agric. Res. Center (ARC), Minia, Egypt during 2004-2005 and 2005-2006 winter seasons, to investigate the response of bread wheat (Triticum aestivum L.) cv. Sids 1, grown in clayey soil to inoculation with plant-growth promoting rhizobacteria (PGPRs) such as cyanobacteria spp; Serratia sp; Rhizobium leguminosarum bv. viciae and Bacillus polymyxa either solely or in combinations in comparison to mineral N-fertilization, Full N-dose; 75 Kg N/fed. Results revealed the superiority of Bacillus polymyxa for increasing wheat growth and productivity followed by Serratia, Cyanobacteria, and Rhizobium inoculation. Concerning combined inoculations, tetras combination treatment caused the highest increases in wheat parameters, triple combinations were the second, dual combinations were the third and the sole inoculation caused lower increases but still higher than control treatment. On the other hand, full dose of N-fertilizers recorded increases ranged between those of tetras and those of triple combinations. Also, results confirmed the necessity of combined applications with N2-fixers and its superiority on mineral N-fertilizations for wheat productivity.Egyptian Journal of Biotechnology Vol. 25 (1) 2007: pp. 27-44