Scielo RSS <![CDATA[Journal of soil science and plant nutrition]]> vol. 14 num. 1 lang. <![CDATA[SciELO Logo]]> <![CDATA[<b>Effects of exogenous nitric oxide on growth of cotton seedlings under NaCl stress</b>]]> In the present investigation, the role of sodium nitroprusside (SNP, a donor of NO) in inducing salinity tolerance (100 mM NaCl) in cotton was studied. Salt stress reduced the values of photosynthetic attributes and total chlorophyll content and inhibited the activities of nitrate reductase. Furthermore, salt stress also induced oxidative stress as indicated by the elevated levels of lipid peroxidation compared to CK. The application of SNP at 1.00 mM promoted the growth and restrained superoxide anions (O2.-) generation rate. And activities of antioxidant enzymes, namely, catalase (CAT) and superoxide dismutase (SOD), were enhanced by SNP treatment. On the other hand, an increase in the K+ content, antioxidant enzyme activities, along with a decrease in the Na+/K+ ratio, the contents of thiobarbituric acid reactive substances (TBARS) and malondialdehyde (MDA) were observed in the NaCl-stressed seedlings subjected to the low level (0.1 mM) SNP. These results indicated that the application of moderate SNP can be used to protect plants growth and induce its antioxidant defense system under salt stress. <![CDATA[<b>Carbon and nitrogen mineralization potential of biofuel crop <i>(Jatropha curcas</i> L.) residues in soil</b>]]> Use and management ofjatropha residue is currently an important global issue for attaining sustainability in biofuel production from Jatropha curcas on wastelands. Perhaps, knowledge about the decomposition characteristics and nutrient release pattern from jatropha residues amended soils are lacking. Thus, the objective of present research was to characterize the carbon (C) and nitrogen (N) mineralization of jatropha residues during decomposition in soil. The chemical composition of the residues, in terms of C, N, cellulose, hemicelluloses, lignin and phenolics contents were determined. Laboratory incubation studies were carried out with two soils (inside and outside-canopy soil ofjatropha shrub) and four jatropha residues (1% w/w) amendments (cake, leaf, fruit shell or control soil only). The cumulative CO2 evolution of the added residues was in the magnitude of fruit shell>leaf>cake>control soil. Net C mineralized in soils were in the range of 46-50, 66-67 and 75-77% of C added by cake, leaf and fruit shell, respectively at the end of incubation study. Soils amended with leaf immobilized N during the first 64 days but subsequently released inorganic N. The addition of cake and fruit shell resulted in net N mineralization and net N immobilization, respectively throughout the incubation period. Cumulative N released by the end of incubation was in the order of cake>leaf>control>fruit shell. Net N mineralization in soils during the study was 75-92 and 21-27% of N added by cake and leaf, respectively whereas there was net N immobilization in fruit shell amended soil. Cumulative CO2 evolution as well as N mineralization during incubation were higher in inside-canopy soil compared with that of outside-canopy soil. Jatropha cake and leaf proved to be a potential source of mineral N, however leaf will take about 60-70 days as gestation period to mineralize the nitrogen. Similarly, leaf and fruit shell also exhibited a good potential of C mineralization. <![CDATA[<b>Litter Decomposition and Microbial Biomass in Temperate Forests in Northwestern Turkey</b>]]> The purpose of this study was to investigate the influence of microbial biomass on the litter decomposition in relation to litter quality, litterfall, canopy leaf area and soil characteristics. The mean values for litterfall were 4245, 3510 and 2935 kg ha-1 year-1 for beech, fir-beech and fir stands, respectively. In the research area, beech stand has higher litterfall than fir, this may be attributed to high allocation of biomass to leaves, thus, makes them fall as litter more easily. One-year mass loss of litter decreased in this order: fir (23.6%) > fir-beech (17.2%) > beech (13.16%). Annual decay constant was significantly lower for beech (k=0.159) than fir litter (k=0.254), reflecting differences in nitrogen and lignin content between litter types (beech, 0.63% and 36.15%; fir, 1.40% and 28.10%). Fir litters have greater microbial biomass C content during the sampling period compared with beech and fir-beech litters. Microbial communities in fir litter were energetically more efficient (had a lower gCO2) with a higher Cmic/Corg compared to those in beech leaf litter. The results of this study indicate that admixed fir needles tended to speed up decomposition of beech foliage in these types of forest ecosystems. <![CDATA[<b>Managementof <i>orobanche</i> in field crops</b>: <b><i>A review</i></b>]]> Broomrapes (Orobanche sp.) are a root holoparasitic plant devoid of chlorophyll and entirely depending on the host for nutritional requirements. They cause considerable yield losses (5-100 %) in the crops, especially in the drier and warmer areas of Europe, Africa and Asia where it is reported to mainly parasitize species of leguminous, oilseeds, solanaceous, cruciferous and medicinal plants. It is a serious root parasite threatening the livelihood of the farmers with its devastating effect on the some of aforementioned crops. The long-term impact of the broomrapes is even more serious: their seeds may easily spread to other fields, and can persist in soil up to 20 years, leading to an accelerated increase in the infested areas in which susceptible crops are under danger. Orobanche seed dispersal is facilitated by man, agricultural tools, crop seeds, propagules and also by animals through their excreta. This review will discuss and summarize alternative methods viz preventive, physical, chemical, agronomic, biological, crop resistance and integrated methods which are needed to manage this parasite. However, the main concern is that, up to date, no single cheap method of control proved to be effective, economical and complete in protection against this parasite. For that reason, an integrated approach is needed in which a variety of such techniques are combined, in order to maintain parasite populations below threshold levels of damage. <![CDATA[<b>Interactions between arbuscular mycorrhizal fungi and <i>Meloidogyne incognita </i>in the ornamental plant <i>Impatiens balsamina</i></b>]]> Biocontrol traits of arbuscular mycorrhizal fungi (AMF), in terms of single and mixed species inoculum, against the root knot nematode Meloidogyne incongita in Impatiens balsamina L., were examined with and without mineral fertilization in a greenhouse pot experiment. At harvest, 60 days after sowing, general plant growth parameters and plant defense response in terms of antioxidant activity and content of phenolic compounds in roots and leaves were measured. Also AMF root colonization and abundance ofnematode root-knots were determined. Mineral fertilization increased all plant growth parameters measured, which coincided with an increased disease development caused by M. incognita. Inoculation with AMF mitigated the observed plant growth reduction caused by M.incognita, though, higher abundance of M. incognita root knots was found in mycorrhizal plants. Plant defense responses in terms of antioxidant activity and content of phenolic compounds did not seem to be linked to the observed biocontrol traits of AMF against M. incognita. However, roots inoculated with a consortium of AMF, which presented less nematode root knots than roots with the single species inoculum, had the highest level of phenolic compounds. The results from the present study suggest that AMF induce tolerance in I. balsamina against the root knot nematode M. incognita. <![CDATA[<b>Seasonal dynamics of dissolved organic carbon, nitrogen and other nutrients in soil of <i>Pinus massoniana</i> stands after pine wilt disease disturbance</b>]]> To understand changes in soil nutrients in Pinus massoniana forests affected by pine wilt disease (PWD), we examined the seasonal variation in dissolved organic carbon (DOC), dissolved organic nitrogen (DON) and soil nutrients in Hefei, East China. The results showed a considerable decline in the population density and basal area in both highly disturbed (HD) and moderately disturbed (MD) forest stands and an increase in dead pine trees, causing pronounced changes in the stand structure and soil nutrient status. The concentrations of DOC and NO3-- N were significantly (p < 0.05) higher in every season in the disturbed forests compared to the undisturbed (UD) forest stand. However, during spring and summer, the variation in the DON and NH4+-N values was significantly (p < 0.05) lower in the HD forest stand than in the UD stand; total N concentrations were higher in the disturbed forests in every season. During spring and autumn, the variation in total P values was significantly (p < 0.05) lower in the MD forest stand than in the UD stand, whereas the total P values were significantly (p < 0.05) lower in every season in the HD stand than in the UD stand. In this study, disturbance resulted in a considerable increase in DOC, N and NO3-- N when compared to the UD stand and a pronounced increase in soil nitrate in the HD stand, which may lead to soil acidification, thereby increasing the possibility of soil nutrient leaching. <![CDATA[<b>Influence of nitrate fertilization on Cd uptake and oxidative stress parameters in alfalfa plants cultivated in presence of Cd</b>]]> Plant nutrients might affect the activity and bioavailability of heavy metals in the soil -plant environment thus their accumulation in the plant. Little is known about the effect of nitrogen fertilization on cadmium (Cd) uptake by alfalfa "Medicago sativa". This work aims to characterize the oxidative status, the physiological stress parameters and the Cd uptake in alfalfa + Medicago sativa ; exposed to Cd and supplied with nitrogen fertilizers. The experiment was carried out in a green house with alfalfa grown in Cd-polluted soil (3.6 ppm) and amended with two different fertilizers: without NO3- (PK) or with NO3- (NPK) in a sand:peat (v:v) mixture. The following parameters were monitored: Chlorophyll content, Photosynthesis rate, Catalase (CAT) activity, Thiobarbutiric Acid Reactive Species (TBARS) content and Cd bioaccumulation. It was found that NPK fertilization increased mean Cd uptake as well as plant biomass in Cd-exposed plants. Nitrogen supply was also effective in reduction Cd-induces phytotoxicity (Photosynthetic pigments and rate) and oxidative stress alterations. Our results suggest that nitrogen supply may improve the uptake rate of Cd by alfalfa and provide new insights on the importance of nitrogen fertilization towards future phytoremediation applications using alfalfa. <![CDATA[<b>Characterization of soil properties of Nothofagus spp. forest with and without scarification in the Andean region of Southern Chile</b>]]> Soil scarification has been used as a silvicultura! method to eliminate competition in tree regeneration, but it modifies soil characteristics. In order to evaluate soil changes due to silvicultural management, we characterized a volcanic soil subjected to a mechanized scarification in a Nothofagus spp. forest in the Andean region of southern Chile (390 54' S, 710 56' W; 970 m asl). Scarification removed between 20 and 40 cm of topsoil in forest gaps. Two scarified areas were selected in different periods and in an undisturbed forest area. Physical properties (bulk density, penetration resistance, porosity, texture) and chemical (pH, soil organic matter, total-N, P-Olsen, K, Mg and Ca extractable, Al saturation) were analyzed in both the scarified soil and undisturbed forest. The morphology of the soil was a result of the formation of a stratified soil. Bulk density was higher in the superficial layer of the scarified soil (0.9 to 1.2 g cm-3) when compared to the undisturbed forest (0.3 g cm-3). With regards to the undisturbed forest, soil scarification exposed a superficial soil of coarser texture, lower total porosity (50-60% vs. 80%) and it decreased the soil nutrient supply. There were no large variations in soil properties when comparing the oldest scarified soil with the most recent one. There were important changes in morphology, physical and chemical properties of the scarified soil. <![CDATA[<b>Effect of scarification on soil change and establishment of and artificial forest regeneration under Nothofagus spp. in Southern Chile</b>]]> Soil scarification has been used as a silvicultura method to facilitate the regeneration of some forests, but it may have a negative impact on the properties of the soil. We evaluated the effect of a mechanized scarification on a volcanic soil after a shelterwood cutting in a Nothofagus spp. forest, located in the Andean region of southern Chile (39° 54 'S, 71° 56' 5 W, 970 m asl). A plantation of Nothofagus nervosa was established after scarification, and its physical (moisture content, bulk density, penetration resistance) and chemical (pH, organic matter, macro and microelements; saturation Al) soil properties were analyzed in scarified gaps and undisturbed forest. The size of N. nervosa planted trees was measured eleven months after their establishment (June 2010). The volumetric water content of the soil was similar with and without scarification (30-50%), regardless of the time of year. The bulk density was higher in the scarified soil when compared to the undisturbed forest. The soil nutrient supply in the gaps (0-20 cm) decreased when compared to the undisturbed forest (0-10 cm), but showed little difference between gaps and between locations within them. The N. nervosa plantation developed properly, with similar growth in gaps of different size. Scarification decreased soil quality; the effects on regeneration will need further evaluation throughout a longer period. <![CDATA[Evaluation of chañar seed cake from biodiesel production as a soil amendment]]> One of the major problems for biodiesel producers is the disposal of the seed cake after expelling oil from seeds. Every ton of biodiesel results in 2.5 to 3 tons of seed cake as byproduct. The physicochemical characteristics of this residue indicate that it could be converted into valuable organic fertilizer. In order to evaluate the feasibility of using chañar seed cake from biodiesel production as a soil amendment, a greenhouse pot experiment was conducted. Seed cake was applied mixed with soil, at rates of 0, 6, 12 and 24%. A single seedling of chañar per pot was transplanted and after six months, plants were harvested for foliar analyses as well as some physiological characteristics. Seed cake application increased dry biomass production and the shoot concentrations of N and chlorophyll. There were no evident symptoms of phytotoxicity. The application of seed cake at 12% proved superior to the 6% treatment and the control; ahigher dose of seed cake (24%) was not significantly different from the treatment with 12% in terms of dry biomass production of chañar, foliar contents of N, P, Kor total chlorophyll. However, plant aerial biomass was significantly correlated with soil microbial respiration and soil C biomass. <![CDATA[<b>Changes of soil microbial characteristics in saline-sodic soils under drip irrigation</b>]]> A field experiment was carried out to study the changes of soil bacteria, fungi and actinomycetes in saline-sodic soils for different numbers of cultivated years under drip irrigation. The drip irrigation had substantial effects on levels of bacteria, fungi and actinomycetes. With increased number of cultivated years under drip irrigation, the soil biological properties were greatly improved. After three years of cultivation, the respective increases in the levels of bacteria, fungi and actinomycetes were 103.7, 72.7 and 58.2 times those of uncultivated land. In the vertical direction, the colony forming units of bacteria, fungi and actinomycetes all decreased with increased soil depth. We forecast that the soil microbial characteristics in drip-irrigated saline-sodic soils should match those of natural Leymus chinensis grassland after 6-7 years of cultivation. <![CDATA[<b>Effects of napropamide on microbiological characteristics of tobacco rhizosphere soil and its dissipation</b>]]> Knowledge of microbiological characteristics in the plant rhizosphere is essential for understanding the fate and transport of agricultural chemicals in soils. The present study was conducted to investigate the effects of an acetanilide herbicide napropamide on microbiological characteristics of tobacco (Nicotiana tabacum K326) rhizosphere soil and its dissipation behaviors under controlled conditions. The results showed that both microbial populations and enzymatic activities in rhizosphere soil were higher than those in non-rhizosphere soil. The populations of bacteria and actinomycetes decreased with napropamide addition in rhizosphere soil, while the populations of fungi displayed the decreasing, recovering and increasing trend throughout the incubation period. The activities of dehydrogenase and catalase were stimulated firstly, owing to napropamide addition, then were inhibited, and recovered to the control level, whereas the activities of urease were inhibited obviously during the testing stage. Napropamide rapidly dissipated in vegetated soil suggests that rhizosphere soil is a useful pathway to rapidly remove or detoxify herbicide residues. <![CDATA[<b>Pedological characteristics of open-pit Cu wastes and post-flotation tailings (Bor, Serbia)</b>]]> To gain a better knowledge of mining areas and potential remediation processes, some characteristics (morphological, physical, chemical and microbiological) of soils formed on open-pit Cu mine waste (OPW) and Cu post-flotation tailings (PFT) dumps were investigated. Soil profiles and surface samples were studied. In general, the investigated soils are characterized by large proportion of coarse soil particles, degraded structure, low humus content, low pH, high As and Cu concentrations, and low soil microbial activity. In all investigated profiles there is no recognizable topsoil layer containing in situ formed humus probably due to soil age, lack of plant cover and organic litter, as well as other unfavorable soil conditions. The specificity of investigated soils is an irregular distribution of some soil characteristics (porosity, humus content, microbiological activity) over depth, which is a result of their technogenic origin. By establishing correlations between the studied surface sample parameters, using principal component analysis (PCA), poorer aggregate properties of PFT than of OPW soils were found, resulting most likely from aggressive mining, i.e., flotation processes. Both OPW and PFT soils compared with control natural soils are characterized by lower clay and humus content, and poorer aggregate properties. <![CDATA[<b>Bean production and fusarium root rot in diverse soil environments in Iran</b>]]> The associations of Fusarium root rot (FRR) and yield variables with a number of soil characteristics were determined at pod maturity in 122 commercial bean fields in Zanjan, Iran. Mean pod and seed numbers per plant at a sand content level of 45-65% were lower than those at a level of 25-45%. Higher FRR index and fewer pods were detected in field soils with 30-48% silt content compared to 15-30% level. FRR index was higher in field soils treated with fungicides compared to non-treated soils. The lowest FRR index and highest yields occurred in the soils with the highest level of organic matter, 1.2-1.8%. The greatest FRR index and lowest yield levels were observed in non-nodulated beans compared to low- and high-nodulated beans. Soil pH and organic matter were negatively correlated with FRR variables. According to loadings for second principal component, the most relevant soil characteristic to FRR was pH, followed by organic matter, clay and sand content. There were spatial FRR correlations among bean fields. Organic matter was the most effective factor among the soil properties surveyed to improve bean productivity. This new information extends our knowledge over interactions between FRR, yield and various soil variables in commercial bean fields. <![CDATA[<b>Degradation of</b> <strong>S</strong><b>-metolachlor in soil as affected by environmental factors</b>]]> <![CDATA[<b>Effects of arbuscular mycorrhizal inoculation and phosphorus fertilization on the growth of escarole <i>(Cichorium endivia</i> L.) in an arsenic polluted soil</b>]]> We have studied the effects of P fertilization and AMF inoculation on the growth of escarole (Chicorium endivia L.) plants ,grown in both As-non-contaminated (Padula) and As-contaminated (La Botte) soils and As and P uptake by these plants. Our study demonstrated that the combined use of AMF inoculation and P fertilization can significantly increase the production of biomass of escarole plants, even if grown in highly As-contaminated soils. In addition, this dual agricultural practice has also allowed to reduce the translocation of the harmful element from roots to leaves minimizing, hence, the accumulation of highly toxic levels of As in the edible part of the escarole. Therefore, the combined use of AMF inoculation and P fertilization may alleviate the As toxicity to sensitive plants as Cichorium endivia, by promoting their growth, limiting As assimilation and improving P nutrition. <![CDATA[<b>Effects of substrate and salinity in hydroponically grown <i>Cichorium spinosum</i></b>]]> The present work, examined the effect of salinity (5, 40 and 120 mmol L-1 NaCl) in the growth and the quality of hydroponic culture of stamnagathi (Cichorium spinosum L.). Plants were developed in perlite, pumice, rockwool and sand respectively. High salinity decreased leaf number, leaf size and plant biomass in plants grown in perlite, pumice and sand. Reduced plant biomass also observed in plant grown in rockwool, although an increased number of leaves were produced. Leaf area reduced in plants grown in rockwool and sand under 120 mmol L-1 NaCl. Low salinity maintained almost similar status as the control treatments. Symptoms of tip burn appeared in 120 mmol L-1 NaCl treated stamnagathi for perlite and pumice. No differences observed in leaf chlorophyll content, leaf fluorescence and in symptoms of discoloration. When the perlite was used as substrate, salinity increased total phenols and decreased protein content. Finally, the low concentration of salinity improved some plant quality parameters as recorded by panelists, following organoleptic test. Thus, stamnagathi proved to successfully tolerate low salinity concentration in hydroponically grown plants. <![CDATA[<b>Effect of vermicompost tea on yield and nitrate reductase enzyme activity in saladette tomato</b>]]> In conventional agriculture, heavy doses of chemical fertilizers and pesticides are often used to improve the yield of various horticultural crops. These chemical fertilizers and pesticides cause health problems among consumers. Due to the adverse effects of chemical fertilizers, there is interest in the use of organic fertilizers. It has long been recognized that the rate-limiting step for nitrogen assimilation, the reduction of NO3- to NO2- catalyzed by nitrate reductase (NR), is highly regulated. An increase in the amount and activity of NR leads to a corresponding increase in the potential for nitrate reduction and confers a greater capacity for general amino-acid synthesis, protein synthesis or total nitrogen assimilation. The aim of the current experiment was to determine the effect of organic and conventional fertilizers on yield and nitrate reductase activity in saladette tomato.Tomato plants were grown under controlled greenhouse conditions and treated with either organic or conventional fertilizer. We evaluated five treatments: F1, sand + inorganic fertilizer; F2, sand + vermicompost tea; F3, a 1:1 mixture of sand: compost + vermicompost tea; F4, a 1:1 mixture of sand: vermicompost + vermicompost tea; and F5, a 2:1:1 mixture of sand: compost: vermicompost + vermicompost tea. The evaluated variables were yield, fruit size, number of fruits, fruit quality, chlorophyll content, and in vivo nitrate reductase enzyme activity. Fertilizer type strongly influenced the yield, fruit size, and fruit quality. The best organic fertilizer for tomatoes was sand + vermicompost tea. Tomatoes in this treatment group produced the second highest yield, the best NO3- assimilation, the greatest nitrate reductase enzyme activity, and the second highest organic foliar nitrogen content. <![CDATA[<b>Detection of drought tolerant sugarcane genotypes (Saccharum officinarum) using lipid peroxidation, antioxidant activity, glycine-betaine and proline contents</b>]]> Thirteen genotypes of sugarcane were exposed to different drought stress intensities followed by a period of stress relief. Different biomarkers were used to analyze the stress tolerance in leaves which include DPPH activity, proline, glycine betaine, lipid peroxidation and phenolic contents against different doses of Polyethylene glycol. Relatively the concentrations of all biochemical markers were increased when PEG concentration was increased. On the basis of lipid peroxidation, glycine betaine and proline contents, HSF-242, Lho-83, HSF-240, CP-77-400, CPF-198, NSG-45, NSG-60 and NSG-555 were found to be drought tolerant genotypes. In conclusion the drought stress-induced changes are reversible, at the cellular level in sugarcane. <![CDATA[<b>Improving pasture growth and urea efficiency using N inhibitor, molybdenum and elemental sulphur</b>]]> A one year field experiment was conducted to assess the efficiency of urea fertilizer applied to pasture near Lincoln University, New Zealand. Urea with or without () molybdenum (Mo) were applied to field plot, with a urease inhibitor [N-(n-butyl) thiophosphoric triamide (nBTPT), nBTPT + elemental sulphur (S), and nitrification inhibitor dicyandiamide (DCD) + nBTPT defined as a double inhibitor (DI) in spring 2005. Mo was sprayed at the rate of 50 g Mo/ha/yr once. Urea various inhibitor and S treatments were broadcast at a rate of 30 kg N/ha 5 times over one year. The Mo alone treatment increased pasture dry matter (PDM) yield by 8.9%. Molybdenum, when applied together with urea+nBTPT+S, urea+nBTPT and urea alone, caused an initial depression in PDM yield by 14.2, 13 and 5.6% respectively. However, these depressions in yield disappeared from the second pasture cut. Over a one year period, Mo applied with urea+nBTPT, urea+DI and urea+nBTPT+S produced 18179, 16716 and 18253 kg DM ha-1 respectively, compared to 16171 kg ha-1 for urea+Mo. Pastures which received no Mo, but were treated with urea+nBTPT+S, or urea+nBTPT produced 18982 and 18276 kg DM ha-1 respectively, compared to 16363 kg ha-1 for urea alone, giving an increase of 16% and 12% over urea alone. Pastures receiving Mo, together with urea+nBTPT or urea+nBTPT+S, also showed improvement in N uptake and N recovery, compared to urea alone. Applying urea with nBTPT and S have the most potential to improve urea efficiency.