Journal of soil science and plant nutrition

Reduced dry olive residue phytotoxicity in the field by the combination of physical and biological treatments

Olive oil extraction generates large amounts of olive mill residues (DOR) which may be used as organic fertilizer. The influence of a combination of physical fractionation and saprobe fungal incubation on the phytotoxicity of DOR was studied. The physical fractions of DOR, obtained following extraction using ethyl acetate (EDOR) and water (ADOR) were less phytotoxic than DOR with respect to the shoot dry weight of tomato. There was no relationship between the total phenol content of the different DOR physical fractions and their phytotoxicity. The saprophytic fungus Coriolopsis rigida reduced DOR and ADOR phytotoxicity and eliminated the phytotoxicity of EDOR. However, unlike the physical treatments of DOR, the decrease in the phenol content of EDOR and ADOR caused by C. rigida was closely paralleled to the decrease in their phytotoxicity. After 30 days of incubation, C. rigida was able to eliminate the phytotoxicity of EDOR on tomato plants grown in the field.

Carbon stock and mineral factors controlling soil organic carbon in a climatic gradient, Golestan province

Organic matter content of the many soils is less than 5% by weight; nevertheless this small amount of organic matter (OM) has a significant impact on soil properties. A study to evaluate the role of climate in distribution of organic carbon (OC) and mineral factors (such as soil composition, soil stability and clay minerals) controlling OC was performed. Seven surface soils were collected (0-20 cm depth) with three replications in a climate gradient (200 to 800 mm of rainfall). The results showed that aggregates < 0.053 mm in most of the soils had the lowest organic matter content (Figure 2), and carbon stock increased with increasing in the aggregates size in most soils. There was no significant relationship between OC content and clay mineral content, but there was significant relationship for illite and chlorite. It can therefore be deduced that OC stock is probably controlled mainly by climate factor than clay minerals. Oxalate iron was positively related to OC content, but this relationship does not apply for dithionite iron. The relationship between soil OC content and specific surface area (SSA, g m-2) of the soil was positive and significantly correlated. Labile soil OC content had a positive relationship with the climate index (P/ET°). As the index increased the potential loss of OC content increased, as well. Labile OC content was estimated between 0.49 to 16.64 g kg-1 and a potential loss of OC was between 1.28 to 46.12 Mg of carbon per hectare on the soil surface horizon.

Requirement of nitrogen, phosphorus and potassium fertilizers for wheat cultivation under irrigation by municipal wastewater

This study quantified the optimum doses of nitrogen (N), phosphorus (P) and potassium (K) fertilizers for wheat (Triticum aestivum L. cv Shatabdi) cultivation under irrigation by municipal wastewater (here after called wastewater). Separate experiments were conducted with the three nutrients, applying each at five different doses and the other two at the recommended doses. An equal amount of irrigation by wastewater was provided to each experiment. The spike length, spikelets per spike, grain yield and harvest index of wheat increased with the increase in N dose up to 100 kg ha-1, but decreased with further doses. Most of the growth and yield attributes improved significantly (p = 0.05) with the increase in P dose up to 20 kg ha-1, beyond which the P exerted negative, but insignificant, effect on the crop attributes. The omission of N or P significantly reduced the yield attributes and yield of wheat, with the dominant effect of N. Either the omission or the higher than the recommended dose of K had no significant suppressing effect on the grain yield of wheat. The crop most effectively utilized the nutrients when supplied at the lower doses. The omission of N or P or K minimally reduced the 1000-grain weight. The negative effects of the excess nutrient doses were the greatest for N and least for K, implying that N was the most limiting and K was the least limiting factors for wheat production.

Biosurfactants are useful tools for the bioremediation of contaminated soil: a review

Bioremediation processes are negatively affected by the low aqueous solubility of some contaminants; therefore their bioavailability may be enhanced by the addition of surfactants. These compounds are organic molecules that can be chemically and biologically produced. Surfactants contain both hydrophilic and hydrophobic groups, therefore reducing surface and interfacial tensions of immiscible fluids and increasing the solubility and sorption of hydrophobic organic and inorganic compounds. This article provides an overview of characteristics of natural and synthetic surfactants and the effects of biosurfactants on solubility, sorption and biodegradation of hydrophobic organic contaminants; as well as the effects of biosurfactants on degrader microorganisms as white-rot fungi. Finally, some examples of application of natural surfactants for bioremediation of contaminated soils are shown. In general, this overview indicates the great potential of biosurfactants on the remediation of contaminated sites.

Soil dry aggregate size distribution: effects of soil type and land use

Soil structure is an important physical property of soil and has a great impact on the environment and agriculture. Dry aggregate size distribution and related soil structure indices are essential parameters in understanding the structural state of the soil. This study was conducted to determine the effects of different soil types and land uses on structure parameters and to relate them to selected soil properties. The investigation was performed on five soil types (Arenosols, Fluvisols, Chernozems, Gleysols and Solonetz), each from three different locations and under three different land uses (cropland, meadow and forest), so that a total of 135 undisturbed soil samples were collected. Dry sieving analysis was performed to obtain eight aggregate size classes (ASCs) (>10, 10-5, 5-3, 3-2, 2-1, 1-0.5, 0.5-0.25 and <0.25mm). The results suggest a highly significant impact of soil type on all ASCs and structure indices. Land use has a highly significant impact on the >10, 5-3 and 3-2 mm ASCs. Chernozems and Gleysols have more favorable structure than Arenosols, Fluvisols and Solonetz. Long term cultivation leads to the deterioration of soil structure and the formation of clods. Forest soils have a significantly better structure than soils under meadows and croplands. The application of principal component analysis and regression models identifies water retention at -33 kPa, bulk density and pH value as for the most important factors in predicting dMWD and dGMD.

Effect of compost and animal manure with phosphorus and zinc fertilizer on yield of seed potatoes

This study was carried out to investigate the effect of compost and manure with phosphorus and zinc on potato yield (Solanum tuberosum L.). The experiment was conducted in the Kerman agricultural and natural resources research centre (Iran) by using a factorial design in randomized complete block in two independent experiments with three replications. In the first experiments compost with phosphorus and zinc were used, and in second experiment animal manure with phosphorus and zinc were used. The three levels of compost (0, 10 and 20 ton ha-1) and same level of animal manure were used as main. Four levels of phosphorus (0, 75, 150 and 225 kg ha-1) and two levels of zinc (0 and 50 kg ha-1) used as the sub factors. Results showed that the main factors of compost and animal manure application had no significant effect on any of the all evaluated traits in the experiments. Effect of zinc on number of small tubers was significant in the first experiment. The highest number of large tubers were found in 20 ton ha-1 compost + 225 kg ha-1 phosphorus + 50 kg ha-1 zinc in first experiment and 20 ton ha-1 animal manure + 75 kg ha-1 phosphorus + no zinc in second experiment. Tubers dry matter was significantly affected by the interaction effect of zinc and phosphorus, the maximum dry matter being obtained with the application of 225 kg ha-1 phosphorus +50 kg ha-1 zinc.

Effect of tillage, rotation and crop residues on wheat crop productivity, fertilizer nitrogen and water use efficiency and soil organic carbon status in dry area (rainfed) of north-west Pakistan

Crop productivity, soil organic carbon (SOC), fertilizer nitrogen and water use efficiency (WUE) in rainfed dry area is influenced by tillage, rotation and crop residues management. Field experiments were conducted during 2004-09 to study the effect of tillage, rotation and crop residues on wheat yield, nitrogen fertilizer and water use efficiency and SOC under semi-arid condition in north-west Pakistan. The treatments consisted of three rotations: i) Wheat-fallow-wheat (farmers' practice) ii) Wheat- summer legume-wheat and iii) Wheat-summer cereal-wheat with two tillage and crop residues management treatments: i) Tillage (crop residues removed) and Tillage (crop residues retained) and ii) No-tillage (crop residues removed) and No-tillage (crop residues retained). Basal doses of N60: P60 (kg ha-1) to wheat, N90: P60 and N20: P60 (kg ha-1) to summer cereals and legumes rotation crops were applied respectively. Labeled urea having 1% 15N atom excess at 60 kg N ha-1 was applied to wheat as an aqueous solution in micro plot within each treatment plot. Changes in soil water storage were monitored with neutron moisture probe for calculation of WUE. The results revealed that the wheat grain and straw yield was not increased by the tillage treatment. Crop residues retention significantly enhanced the wheat grain and straw yield. Crop residues with no-tillage resulted in 520 kg ha-1 greater wheat grain yield than residues removed treatment. Similarly WUE, N yield and fertilizer N utilization by wheat was increased significantly by crop residues under no-tillage compared to the tillage treatment. Maximum N fertilizer utilization 24.1 %, 62.7 % and 38.0 % in wheat were obtained under no-tillage + residues treatment during 2006, 2007 and 2008 respectively. The SOC in surface soil (0-15 cm) was higher in wheat-fallow-wheat and wheat-legume-wheat rotation under no-tillage + residues treatment. The results showed that no-tillage + crop residues and legume based rotation treatment were beneficial under the rainfed (dry) conditions.

Polygenetic saline gypsiferous soils of the Bam region, Southeast Iran

Gypsiferous and saline soils are among the major soils of arid and semi-arid regions of the world. Although numerous studies on salic, gypsic and petrogypsic horizons have been carried out, the co-occurrence of gypsum and halite and their morphological expression are still poorly documented. Eight pedons located on a co-alluvial fan (Bam area, southeast Iran) were described, sampled and analyzed for physico-chemical and micromorphological characteristics based on standard methods. The highest amounts of gypsum (~ 60 %) comprising xenotopic gypsum and/or fibrous bassanite pseudomorph remaining behind after xenotopic gypsum dehydration were determined in the surface crust and in the underlying 2Byz horizon. At a depth of 15 cm, a horizon cemented by gypsum and halite was observed. The highest amount of gypsum was determined at the upper part of this horizon followed by a sharp decreasing trend towards the lower depth. The amount of halite increases with increasing depth towards the bottom of 3Byzm horizon. Deeper, in the 5Byz horizon the quantity of gypsum increases drastically and coarse elongated gypsum pendants dominate. Micromorphological observations demonstrate that the dominant cementing agent is halite rather than gypsum. However, due to inexistence of petrosalic diagnostic horizon in Keys to Soil Taxonomy, these soils are to be classified as Petrogypsic Haplosalids at subgroup level in Soil Taxonomy. In WRB Taxonomy, they are classified as Petrosalic Solonchaks. Co-occurrence of gypsum and halite in the same horizon, their specific layering and vertical distribution patterns in the studied pedons might be considered as indicators for polygenetic soils in this area.

Effects of clay mineralogy and physico-chemical properties on potassium availability under soil aquic conditions

Aquic conditions performed for paddy cultivation may cause many nutritional problems. Clay mineralogical composition plays an important role in this relation by affecting many physico-chemical and biological characteristics of soils. Three forms of K including unavailable, slowly available and readily available K, exist in equilibrium in the soil system. Relationships between soil potassium forms with the clay mineralogical suite and physico-chemical properties were determined in 33 soil samples collected from five from paddy soils, two from kiwi fruit and one from citrus land pedons in the North of Iran. Mineralogical analyses showed that smectite, illite and vermiculite were the most abundant clay minerals in the studied soils. Mean soluble and exchangeable potassium in paddy soils were rather low compared to non-paddy soils due to potassium fertilization in non-paddy soils. Non-exchangeable potassium in the samples containing smectite as dominant clay mineral was lower than the samples dominated by vermiculite, hydroxy-interlayer vermiculite (HIV) and illite. Inability of the studied soils for potassium fixation was related to prevailed montmorillonitic type of smectite, which its layer charge originates from octahedral sheet. Significant correlations (0.56**, 0.54**, 0.56**) were obtained between exchangeable potassium and clay content, organic carbon and cation exchange capacity respectively. Therefore, taking into account both exchangeable and non-exchangeable K beside clay mineralogy and physico-chemical properties gives better indications for K potential and soil-quality management, compared to exchangeable form of K alone.

**Dynamics of soil organic carbon and dissolved organic carbon in Robina pseudoacacia forests**

We investigated the variation patterns of organic carbon in soil and soil solution of four selected Robiniapseudoacacia forests aged 10a, 25a, 31a, and 35a, as well as a contrastive tillage site in a similar topography condition in Loess Plateau, China. The purpose was to explore the dynamics of soil organic carbon (SOC) and dissolved organic carbon (DOC) in R. pseudoacacia forests. On average depths of 20, 40, and 60 cm, SOC, active organic carbon (AOC), and DOC gradually increase with increased forest age. After forest restoration, the AOC/SOC ratio and resistant organic carbon/SOC ratio increase, whereas the slow organic carbon/SOC ratio decreases. The soil solutions in the subsoil layer have low DOC:DON ratio and high UV absorption at 280 nm. At 40 and 60 cm, the depth distribution is indicated as special low values for DOC concentration in the C99 site (10a site), as well as for soil water content, SOC, and AOC in the 25a forest site. Our results provide evidence that during forest restoration, SOC does not consistently increase linearly. The change points of different SOC proportions and DOC concentrations at various depths are not same, i.e., asynchronous changes exist.

**Influence of phosphorus on the arsenic uptake by tomato (Solanum lycopersicum L) irrigated with arsenic solutions at four different concentrations**

We have studied the uptake and distribution of arsenic (As) and phosphorus (P) in roots, shoots and berries of tomato plants, grown on uncontaminated soil, irrigated with As-contaminated solutions at four concentrations (0, 0.5, 2 and 4 mg L-1), in presence or absence of P fertilization. The biomass of tomato plants decreased with increasing As concentration in irrigation water, especially tomato berries. In addition, the reduction of biomasses was significantly greater in plants non-fertilized with P. The beneficial effect generated with the P addition indicated that this nutrient played an important role in alleviating As toxicity in tomato plants. The higher the As concentration in irrigation water the higher the As concentration in plant tissues; most of the As absorbed by plants was accumulated in their roots. Phosphorus application has allowed to reduce As translocation toward tomato berries, enhancing plant P status. These observations may be useful for certain areas of the World, in which As-contaminated waters are used for agricultural purposes.

Chlorpyrifos degradation in a Biomix: Effect of pre-incubation and water holding capacity

Biobed system is a simple method to minimize point source contamination during manipulation of pesticides and is based on the adsorption and degradation potential of a biomix composed by top soil, peat, and straw and covered with a grass layer. In our study, the biomix was prepared with Andisol, peat and straw in a volumetric proportion of 1:1:2, and adsorption and degradation studies were done. Degradation of chlorpyrifos (160 mg a.i. kg-1) and formation of TCP (3, 5, 6-trichloro-2-pyrinidol) at different pre-incubation times (0, 15 and 30 days) and with different moisture contents (40, 60 and 80 % of water holding capacity) were evaluated, ligninolytic enzyme activity and microbial respiration in the biomix were periodically analyzed. Adsorption isotherms were fitted using Freundlich and linear models for Andisol and the biomix. The adsorption assays demonstrated that biomix has a higher capacity to retain chlorpyrifos than top soil. The pre-incubation period, WHC and the concentration of the chlorpyrifos of the biomix influenced the degradation of the contaminant and TCP formation as well as the biological activities in the biomix. The TCP was formed during the first steps of chlorpyrifos degradation and was later degraded in the biomix under all studied conditions. In conclusion, biomix with Andisol, peat and straw (1:1:2), pre-incubated by 15 days and incubated with 60% of WHC is capable to degrade chlorpyrifos efficiently.

**Bio-diesel waste as tailored organic fertilizer for improving yields and nutritive values of Lycopercicum esculatum (tomato) crop**

The present study focused on utilization of the de-oiled Jatropha cake, a bio-waste from the bio diesel extraction process, as organic fertilizer. Tomato crop was subjected to different treatments comprising varying composition of the Jatropha cake fertilizer, applied at varying age of plant life-cycle. The impact on yield, morphological and nutritional parameters was studied. Results revealed that an optimal (2-3 % by weight) dose applied on the soil at the time of onset of flowering (around 45 days), significantly enhanced the yield along with improvements in morphological parameters. There were significant improvements in key nutrients viz. protein, vitamin C and reducing sugars. High value of key nutrients like TSS (total soluble solid), vitamin C, proteins, reducing sugar and tomato fruit yield were obtained with soil + 3% cake mixed in 60 day transplant. These results indicate that composted de-oiled Jatropha cake has tremendous potential of being utilized in a cost effective way as tailored organic fertilizer, as a replacement of chemical fertilizers.

Bacillus subtilis NRRL B-30408: A potential inoculant for crops grown under rainfed conditions in the mountains

On-farm inoculation trials have been conducted to evaluate the potential of Bacillus subtilis NRRL B-30408 in respect of plant growth promotion, for two consecutive years, under rainfed conditions at a mountain location in the Indian Himalayan Region (IHR). For this, one cereal (Oryza sativa) and two millets (Eleusine coracana and Echinochloa frumentacea), were used as test crops. Observations were recorded in terms of plant growth, yield, chlorophyll content, and root colonization by various groups of microorganisms. Positive influence of bacterial inoculation on all the three crops, statistically significant in case of most parameters examined as compared to untreated controls, was recorded in both the years. There was a significant increase in chlorophyll concentration in leaves of inoculated plants. While the bacterial inoculation stimulated the free living bacterial and actinomycetes populations in the rhizosphere, the fungal population was somewhat suppressed; indicative of the antifungal property of the inoculant. The treatment also enhanced the colonization of arbuscular mycorrhizae (AM), and the endophytes associated with the roots. In conclusion, the plant growth promotion, recorded as a result of microbial inoculation, is attributed to the microbial shift in the native microflora of the rhizosphere. Based on the results of this field study, B. subtilis NRRL B-30408 can be proposed as an efficient bioinoculant for the hill crops, grown under rainfed conditions of the mountain ecosystem. The main aim of this study was on farm demonstration of the microbe based technology with peoples' participation, with a view of adoption of the technology by the farmers.

The effect of minerals changing the sorption on non-ionic compound sorption by capacity of soil organic matter

For non-ionic compounds, the preliminary role in the sorption process is played by soil organic matter (SOM). However, it is necessary to determine the relative contribution of soil minerals, in particular, soil clay minerals and SOM constituents, to improve prediction of the sorption process. Here, the results show that sorption capacity of SOM can be affected by mineral-SOM interaction. The organic carbon-normalized sorption coefficient (Koc) after hydrofluoric acid (HF) treatment increased an average of 124% and 98% for A11 horizons and 185% and 162% for A12 horizons for diuron and phenanthrene, respectively. We propose that the increased Koc values in the A12 horizons are due to a higher percentage of clay in A12 horizons as well as a loose connection of SOM with clay minerals in A11 horizons. We suggest that the mineral components of soil contribute greatly to sorption of even non-ionic compounds with alteration of the sorption properties of SOM, which need to be considered in determining the fate and availability of non-ionic compounds in the soil environment.

Soil and starter fertilizer and its effect on yield and protein composition of malting barley

Fertilizer application and growing locations are known to influence yield and protein concentration of malting barley. The aim of the present investigation was to evaluate the influence of soil and starter fertilizer on yield and protein composition in mature and maltedbarley. The cultivar Prestige was grown in two different soils (Lunnarp and LaxmansÅkarp) in combination with the use/non-use of starter fertilizer in climate chambers. Yield parameters, protein concentration and composition was measured. Effect of soil on plant emergence, yield and protein composition was significant while the effect of starter fertilizer was not. More nitrogen rich and low humus content soil (Lunnarp) resulted in higher grain yield and polymerization of proteins and lower protein concentration than the other soil. Combination of soil and starter fertilizer influenced protein composition in mature and malted barley. Breakdown of proteins were significantly higher at certain combination of soil and starter fertilizer than with other combinations. The Lunnarp soil combined with starter fertilizer was preferable to obtain high yield, low protein concentration and large grain size in mature grains. When breakdown of proteins at malting was taken into consideration as well, Lunnarp soil together with no starter fertilizer might be the best option.

Ions uptake, yield and yield attributes of rapeseed exposed to salinity stress

Soil salinity is a serious constrain to crop production in many areas of the world. A pot experiment was carried out with rapeseed genotypes in order to investigate the effects of salinity stress on yield associated traits and shoot ions composition. Eight rapeseed genotypes were evaluated in three salinity levels of irrigation water including 0, 6 and 12 dsm-1. A factorial experiment based on completely randomized design with 4 replications was considered for evaluation of 24 treatments. Significant mean square of the salinity levels, genotypes and salinity xgenotypes interaction effects were exhibited for seeds per pod, pods per plant, seed yield, Ca, K and Na, indicating significant differences of salinity levels and genetic differences for these traits. Due to significant correlation of seed yield with seeds per pod and pods per plant these traits can be considered as indirect selection criteria for seed yield improving. Among shoot ions compositions, K had significant positive correlation with seed yield, therefore this ion can be considered as good indicator for seed yield improving at saline environment. The genotypes including Hyola401, LRT1 and DSM12 had high amounts of seed yield at 12 dsm-1 of salinity level and were considered as tolerant genotypes.

**Statistical optimization for improved indole-3-acetic acid (iaa) production by Pseudomonas aeruginosa and demonstration of enhanced plant growth promotion**

The present study was undertaken to study the statistical optimization of medium components for improved Indole-3- acetic acid (IAA) production by Pseudomonas aeruginosa. Colorimetric analysis showed maximum IAA (132 ìg mL-1) in the medium supplemented with tryptophan (0.5 g L-1). The maximum production was achieved after 96 h of incubation. Yeast extract, tryptophan and EDTA were identified as significant components influencing IAA production by Pseudomonas aeruginosa, using the Plackett- Burman method. The statistical optimization approach led to the production of 318 ìg mL-1 of IAA within 24 h of incubation. Statistical approach was found to be very effective in optimizing the medium components in a manageable number of experimental runs with overall 2.4 fold increase in IAA production. TLC and GC- MS analysis further confirmed the IAA production in the cell filtrates of the strain. GC-MS analysis and tryptophan side chain oxidase confirmed the existence of atleast 2 possible pathways for IAA by this strain. Inoculation of P. aeruginosa culture filtrate enhanced seed germination (82.4%) and increase in root length and shoot length (~ 2.6 and ~ 1.1 folds over the control) of cowpea seeds over the control treatment under pot culture conditions.

Characterization of humic acids derived from rabbit manure treated by composting-vermicomposting process

The aim of this work was to evaluate, through different analytical techniques, the evolution of some chemical and physicochemical properties of humic acid (HA)-like fraction extracted from an organic amendment, like rabbit manure, handle with composting followed by vermicomposting process, in comparison with soil HA, in order to reach an appropriate criterion to evaluate the maturity of an organic amendment. The raw material used was rabbit manure treated with composting followed by vermicomposting process. Soil and organic amendments were analyzed by chemical properties. The HA was extracted from the amendments samples and from an Entic Haplustol and analyzed the chemical and physicochemical characteristics by several analytical methods. Through these analytical techniques was possible to follow the evolution of the HA-like fraction during this stabilization-maturation process Through the composting followed by vermicomposting process the HA-like fraction are evolving toward more stable and complex macromolecule resembling native soil HA.

Induced plant secondary metabolites for phytopatogenic fungi control: a review

Pathogenic fungi constitute one of the main infectious agents in plants, causing alterations during developmental stages including post-harvest. Phytopathogenic fungi are controlled by synthetic fungicides; however, the use of these is progressively restricted due to both, the harmful effects of pesticides on the environment and human health and the appearance of highly resistant fungal strains. Therefore, there is a great demand for novel natural fungicides. Higher plants are rich source of bioactive secondary metabolites of wide variety such as tannins, terpenoids, saponins, alkaloids, flavonoids, and other compounds, reported to have in vitro antifungal properties. Thus, secondary metabolites with antifungal activity represent an alternative for achieving a sustainable control of phytopathogenic fungi and to reduce the heavy reliance of synthetic pesticides used to control them. Plant antifungal metabolites may be preformed inhibitors that are present constitutively in healthy plants (phytoanticipins), or they may be synthesized de novo in response to pathogen attack or another stress conditions (phytoalexins). These molecules may be used directly or considered as a precursor for developing better fungicidal molecules. This review presents a selection of antifungal agents induced in plants during fungal attack that can be potentially used for phytopathogenic fungi control in crops.