Scielo RSS <![CDATA[Journal of soil science and plant nutrition]]> vol. 14 num. 4 lang. <![CDATA[SciELO Logo]]> <![CDATA[<b>Nitrate accumulation in leafy vegetables and its relationship with water</b>]]> Present studies show that nitrate accumulation is the major factor influencing the water uptake by vegetables, but there is lack of knowledge on how the relationship between nitrate and water concentrations in different vegetable tissues. We determined nitrate accumulation and water content in vegetables of rape, Chinese cabbage, and spinach under different nitrogen levels (experiment I), 29 spinach cultivars (experiment II), and 27 rape cultivars (experiment III). The results from experiments I-III showed a highly linear relationship between nitrate accumulation and water content, and the levels thereof in different organs of the vegetables revealed that the petiole exhibited the best correlation between them compared with the root and leaf blade. These suggest that (1) vegetables with high water content have high nitrate content, (2) water content in the petiole can be used to screen cultivars with low levels of nitrate accumulation, and (3) increasing soil water content in agronomic practice is essential to decreasing nitrate accumulation in vegetables. <![CDATA[Effect of phosphorus on the composition and accumulation of 7S and 11S globulin subunits during seed development of three soybean varieties]]> Three soybean varieties (Dongnong 42, high-protein cultivar; Hefeng 25, medium-protein; and Dongnong 46, low-protein cultivar) grown under different P conditions were investigated in order to evaluate the effect of P on the composition and accumulation of 7S and 11S globulin subunits. The soybean seeds were planted in pots and fertilized with 0.033 g of N and K2O per kg soil. Four levels of P treatment were designed, which were P1, P2, P3 and P4 (i.e., 0, 0.033, 0.067, and 0.100 g of phosphorus pentoxide (P2O5) per kilogram of soil). The composition of extractable proteins was determined by conducting SDS-PAGE. No significant differences were observed between the varieties with regard to the molecular weights of the globulin subunits. After the subunits were formed, their concentrations gradually increased under different P treatments, reached a peak at 70 d post-anthesis (DPA), and then declined during maturity. The concentrations of the 7S and 11S globulins and other subunits in Dongnong 42 and Hefeng 25 were the highest under the P3 treatment, while they were the highest in Dongnong 46 under the P2 treatment. Under the same P treatment, the concentrations were high in Dongnong 42 and low in Dongnong 46 and Hefeng 25. Significant differences were observed in the concentrations of 7S and 11S globulin subunits between the varieties and levels of P treatments, especially under the P3 treatment. Alpha subunit was mainly in relation with the P-nutrition in the three varieties. These findings suggested that the; optimal combination of cultivarsand P treatment; levels could contribute to the increased concentrations of both soybean globulins and their subunits. <![CDATA[<b>Availability and accumulation of lead for forage grasses in contaminated soil</b>]]> The forage grasses are explored for the phytoremediation of heavy metals from contaminated areas. The present study evaluates the tolerance of forages grasses to Pb and the availability of Pb for the Mehlich 1, DTPA, and USEPA 3051 and 3052 extraction methods. The forage grasses cultivars Panicum maximum cultivars Aruana and Tanzânia, Brachiaria decumbens cultivar Basilisk, Brachiaria brizantha cultivar Xaraés and Marandu were assessed. Each cultivar was grown in a greenhouse in Diamantina, Brazil, in Typic Hapludox (Oxisol). The Pb was applied to the soil at doses of 0, 45, 90 and 270 mg kg-1 soil in a randomized design with four replications. The experiment was conducted over a 90-day trial period. Increasing Pb doses in the soil caused a reduction of growth in all varieties studied, and the "Basilisk" forage was generally more tolerant to Pb, while the Xaraés forage was generally more susceptible to the addition of Pb. The lower transfer coefficient of the cultivar "Basilisk", due to the high Pb content and accumulation in its roots, makes it the most suitable for phytoremediation programs, with possible uses in pasture areas. None of the varieties can be considered a Pb hyperaccumulator. The Mehlich 1, DTPA, USEPA 3051 and USEPA 3052 extraction methods indicated different doses of Pb in the soil, and the Mehlich 1 method demonstrated the lowest level of metal extraction from the soil. No correlation was observed between the forage grasses growth and the measurement of Pb in soil by the studied extraction methods, especially for the Mehlich 1 and DTPA methods, suggesting the inefficiency of these techniques for determining the phytoavailability of Pb. <![CDATA[<b>Exogenous labile C application enhances Fe-P utilization for mycorrhizal plants through iron-reducing bacteria in subtropical soil</b>]]> In a greenhouse experiment, Medicago sativa was grown in iron-rich soil inoculated with arbuscular mycorrhizal fungi (Funelliformis mosseae, FM) and/or iron (Fe) -reducing bacteria (IRB, Klebsiella pneumoniae strain L17) with three exogenous labile C input forms (no C source, as a single dose, and as a pulse) at rates of P0 and P5 (0 and 5 mg P2O5 kg-1, KH2PO4), which is to understand the role of IRB in enhancing the Fe-P utilization with exogenous labile C in subtropical soil. The results showed when inoculated with IRB, labile C as a pulsed input significantly improved the mycorrhiza colonization and hyphal length density, and increased the shoot P content, microbial biomass C and glomalin content at P5 rate; meanwhile, the labile C input also promoted the Fe (II) production, when inoculated with IRB, labile C as a pulsed input increased the C/A extractable Fe (II), oxalate-extractable P and microbial biomass P content. These facts suggested that application of labile C as a pulsed input enhanced the ability of IRB in improving the Fe reduction and Fe-P utilization in subtropical soil. <![CDATA[<b>Inoculation of maize with phosphate solubilizing bacteria</b>: <b>effect on plant growth and yield</b>]]> Phosphate-Solubilizing Bacteria (PSB) improve plant growth, yield and phosphorus content of several crops, and may be used as bioinoculant to enhance sustainable production. We evaluated the response of maize (Zea mays L.) to PSB inoculation under controlled and field conditions in Tucumán, Argentina. A pot culture experiment was conducted to investigate the effects of seven previously isolated PSB on early development of plants. Seeds were treated with each bacterial strain, and seedlings were harvested 30 days after inoculation. All strains showed a positive effect on plant growth. A significant increment in plant height (45%), shoot dry weight (40%) was determined in plants treated with Pseudomonas tolaasii IEXb, while Pseudomonas koreensis SP28 has remarkably increased P content compared to the uninoculated control. IEXb strain was selected and evaluated under field conditions in combination with triple superphosphate (TSP) as P fertilizer. The presence of IEXb strain stimulated seedling emergence (8%), shoot length (19%), grain yield (44%), 1000-grain weight (18%), total dry biomass (32%) and P content (56%) of maize plants. In general, P. tolaasii IEXb inoculation was more efficient as bioinoculant without P fertilizer than with TSP. These results provide baseline information for future studies of P. tolaasii IEXb as bioinoculant to promote an eco-friendly and sustainable agriculture. <![CDATA[<b>Effects of water and potassium stresses on potassium utilization efficiency of two cotton genotypes</b>]]> Potassium utilization efficiency (KUE) for plants is related to genotype difference, soil characteristics, application of fertilizer and irrigation. Up to now, the KUE of different genotypes worldwide has been extensively studied, but the influence of environment stress on KUE of cotton is infrequently reported. Thus, we selected a high K utilization efficiency cotton genotype (HEG) and a low K utilization efficiency cotton genotype (LEG) as indicator plants. The results showed that both soil water stress and K stress limited the growth of cotton genotypes. The change of soil water levels had significant influence on yield, KUE, rates of fallen leaves and bolls (RF), biomass and potassium accumulation in cotton. Deficient of soil water restricted the uptake and translocation of K. The absence of soil K greatly increased the proportion of biomass of reproductive organs and K distribution to reproductive organs in this experiment. The HEG exhibited higher physiological compared with LEG under the stress conditions, especially under low K treatment. <![CDATA[<b>Drought impact on Pb/Cd toxicity remediated by biochar in <i>Brassica campestris</i></b>]]> Heavy metals toxicity in the human being is creating an alarming condition in the world. Not only are these metals largely effecting the growth of many plants but also the consumer’s health. In sector of agriculture for many years Pakistan is facing the reduction in availability of edible oil. The demand is fulfilled by importation by spending huge cost. Brassica campestris L. is very important oil seed crop of Pakistan that is providing 31% of total oil seed production in Pakistan. But due to toxicity of metals like Cd and Pb its growth and yield is decreasing. Keeping in view the importance of Brassica campestris L. in Pakistan an experiment was conducted using Pollutary manure biochar as a reclaiming agent for heavy metals and an amendment as drought stress reducer to check the improvement in yield of Brassica campestris L. It is found that biochar application not only gave positive correlation in immobilization of Pb and Cd but also improves the plants growth and yield. Enhancements in the Photosynthetic and Accessory pigments are observed regarding good vegetative growth. Thus biochar can be utilized in reducing the metals uptake as well as growth promoter. <![CDATA[<b>Pruning severity affects yield, fruit load and fruit and leaf traits of 'Brigitta' blueberry</b>]]> Pruning is crucial to balance productivity and fruit quality in blueberry orchards. Slight, conventional and severe pruning treatments were applied on 4- and 5-year old bluberry plants cultivar 'Brigitta' to evaluate their effect on yield, leaf area, gas exchange and fruit load as driver of fruit quality traits. Yield and berries per plant decreased with increasing pruning severity, whereas canopy leaf area increased. The resulting fruit load ranged from 0.2 to 1.4 fruit per cm² leaf area. Fruit weight, dry matter, glucose and fructose were negatively related to fruit load, with fruit fresh weight decreasing to greater extent than sugars. Berry weight was restricted by source limitation during the initial cell division and initial cell enlargement fruit growth phases as indicated by decreased relative growth rate. Light-saturated photosynthetic rate diminished with increasing pruning severity indicating a sink limitation of photosynthesis. The strong association between photosynthesis and stomatal conductance shows a high corregulation in the response of carbon and water exchange to sink demand. Our results underline agronomic and physiological factors determining blueberry yield and fruit quality and can be useful for agro-technical management. <![CDATA[Combined microbiological test to assess changes in an organic matrix used to avoid agricultural soil contamination, exposed to an insecticide]]> Combined microbiological and molecular test (BiologEcoplateTM, denaturing gradient gel electrophoresis (DGGE) and Real Time PCR (qPCR)) were carried out to evaluate the impact of repeated diazinon (DZN) applications at high concentration (40 mg kg-1) on microbial communities in a microcosm simulating the organic matrix (straw (50%): peat (25%): soil (25%) vv-1) of a pesticide biopurification system (PBS). Pesticide dissipation was also evaluated. After three successive exposures with DZN the dissipation efficiency was high; DZN dissipation clearly accelerated in the organic matrix, achieving 87%, 93% and 96% respectively after the three applications. The results obtained with BiologEcoplateTM showed that the physiological profiles of the community were not affected by the addition of DZN. On the other hand, molecular assays (DGGE and qPCR) demonstrated that the microbial structure (bacteria and fungi) remained relatively stable over time with high DZN doses compared to control. The results of the present study clearly demonstrate the high dissipation capacity of this biomixture and highlight the microbiological robustness of this biological system. <![CDATA[<b>Respiration in mixes of sandy and clay soils</b>: <b>influence of clay type and addition rate</b>]]> In an incubation experiment, a sandy top soil was mixed with kaolinite- or smectite-rich clay soil at 15, 22.5 and 30% clay addition rates. Compared to sandy soil alone, smectite clay soil addition at 22.5 and 30% reduced cumulative respiration per g organic C whereas kaolinite clay soil addition had no effect. This can be explained by the higher surface area and cation exchange capacity of the smectite compared to kaolinite clay soil which protects native organic C from decomposition by binding. <![CDATA[<b>Effect of zn solubilizing bacteria on growth promotion and zn nutrition of rice</b>]]> A comparison study between the isolated indigenous bacteria and chemical Zn fertilizer (ZnSO4.7H2O) was conducted to evaluate their potential to augment Zn nutrition of Zn responsive (NDR 359) and Zn non responsive (PD 16) varieties of rice under the green house. Three bacterial strains namely; BC, AX and AB isolated from a Zn-deficient rice-wheat field belonging to the genera Burkholderia and Acinetobacter were investigated for the growth promotion and Zn uptake in rice plants. The plant growth promotory properties such as Zn solubilization and IAA production of the isolates was checked in a previous study. These three isolates when used individually or in combination were found effective in significantly increasing the mean dry matter yield/pot (12.9%), productive tillers/plant (15.1%), number of panicles/plant (13.3%), number of grains/panicle (12.8%), grain yield (17.0%) and straw yield (12.4%) over the control and Zn fertilizer treatment, respectively. Bacterial inoculations also significantly enhanced the total Zn uptake/pot (52.5%) as well as grain methionine concentration (38.8%). Effect of bacterial treatments on the bioavailability of Zn was assessed by estimating the levels of phytic acid in grains. A reduction of nearly 38.4% in phytate: Zn ratio in grains was observed under bacterial inoculations. <![CDATA[<b>Use of biochar on two volcanic soils</b>: <b>effects on soil properties and barley yield</b>]]> The use of biochar in agricultural soils appears to be promising because it is known to improve soil properties and increase crop production. However, few studies have been conducted with biochar on volcanic soils. Two field experiments were conducted simultaneously to evaluate the effect of oat hull biochar (OBC) on various physical-chemical properties of two volcanic soils, an ‘Inceptisol’ and an ‘Ultisol’, and to evaluate the resulting effects on the yields of barley (Hordeum vulgare) grown on these soils. The OBC doses applied to field microplots were equivalent to 0, 5, 10 and 20 Mg ha-1. The results showed that pH, total exchangeable bases, and electrical conductivity increased at the highest dose of OBC in both soils. Glomalin-related soil protein (GRSP) was significantly high in the Ultisol at a rate of 20 Mg OBC ha-1. Water-stable aggregates (WSA) and mean weight diameter (MWD) were enhanced at the highest doses of OBC in both soils. However, water-holding capacity (WHC) only increased in the Ultisol when amended with OBC at rates of 10 and 20 Mg ha-1. Barley yield (grain weight m-2) significantly increased at the highest OBC dose by 31.3% and 21.9% for crops grown on the Inceptisol and Ultisol, respectively. Significant relationships were observed between WHC and glomalin fractions (r = 0.81, p < 0.01 for easily extractable-GRSP and r = 0.62, p < 0.01 for Total-GRSP) as well as between organic C and WSA and both glomalin fractions. According to this study, biochar may be used effectively to improve the quality of these two volcanic soils and promote sustainable grain production. <![CDATA[<b>Impact of land protection in soil quality properties and in earthworm biomass in Venezuelan savannas</b>]]> We studied soil parameters and the earthworm biomass and density in a protected savanna (PS) from fire and cattle raising for more than forty years located at Estación Biológica de los Llanos, Venezuela (EBLL), and an adjacent non-protected savanna (NS) under frequent burning and agricultural activities, located less than 1 km apart. Earthworm sampling was carried out at the end of the dry season (April), and at the peak of the wet season (July-August) using a hand sorting extraction method. In each plot, five to seven sampling units were selected corresponding to soil monoliths of 25x25x30 cm. The main physical, chemical, microbial (biomass) and enzymatic activities of soils in both systems were estimated. Thepresence of an abundant litter layer under the tree canopies in the PS have increased the soil water retention capacity, the organic-C, C-microbial biomass, dehydrogenase activity and fertility levels respect NS. This may allow for an increase in the density and biomass of earthworms in the PS compared with the adjacent NS. The systems were characterized by abundance in juvenile individuals belonging to the Glossoscolecidae family; two different morphotypes of the genus Aicodrilus were registered. Earthworms found were located in an endo-anecic ecological category. Results suggest that, agricultural management in savannas by modification of physical and biochemical soil properties can decrease an important fraction of pedofauna, particularly their earthworm communities. However, earthworm populations and soil quality indicators can be restored after long-term protection. <![CDATA[Spatial distribution of copper and pH in soils affected by intensive industrial activities in Puchuncaví and Quintero, central Chile]]> The soils of Puchuncaví and Quintero, in the coastal area of central Chile, have been exposed to atmospheric deposition of sulfur dioxide (SO2) and metal-rich particles from the Ventanas Industrial Complex. The objective of this study was to determine, using geostatistical tools, the spatial distribution of copper and pH in these soils. Using Universal Kriging tool for geostatistical interpolation, we generated maps of continuous distribution of Cu and pH in the soils. The distribution of these variables was related to the distance from the industrial complex and to the direction of the winds. The concentrations of Cu and acidity were higher in the surroundings to the industrial complex and in the direction of the dominant winds. Although the distributions of both variables were similar, there was no correlation between the distribution of Cu and pH, which could be due to the distinct aerial dispersion dynamics of the compounds, which causes a divergence in their deposition on the soil. Specifically, this could be due to the fact that SO2 is smaller than the particulate matter that contains copper, so that it is capable of being dispersed over greater distances without being deposited on the soil. <![CDATA[<b>Effect of arbuscular mycorrhizal fungi (<i>Glomus</i> spp.) on growth and arsenic uptake of vetiver grass (<i>Chrysopogon zizanioides</i></b> <b>L.) from contaminated soil and water systems</b>]]> Phytoremediation technology is emerging as a promising environment-friendly method for large-scale cleanup of arsenic (As) contaminated water and soil. In this study we investigated the effect of arbuscular mycorrhizal fungi (AMF - Glomus spp.) on the growth of the vetiver grass (Chrysopogon zizanioides L.) and its As uptake from contaminated hydroponic and soil systems. An ameliorative effect of the AMF inoculation in enhancing plants growth was found, mainly by stimulating the development of their root system. In addition, AMF-inoculated plants also took up more As from both contaminated systems compared to non-inoculated plants, although the differences were not always statistically significant (p < 0.05). Nevertheless, more efficient As uptake by vetiver grass from contaminated hydroponic solutions than spiked soils was observed, essentially because of the higher phytoavailability in the former contaminated system. Furthermore, plants grown hydroponically also translocated higher amounts of As from their roots to shoots. Therefore, the findings of this study reveals that the use of vetiver grass technology in conjunction with AMF would be more appropriate to decontaminate As-contaminated water than soils. <![CDATA[<b>Grain yield and phosphorus use efficiency of wheat and pea in a high yielding environment</b>]]> The aim of the present study was to evaluate the response of grain yield, phosphorus (P) use efficiency (PUE, g yield g-1 P available) and related root traits of wheat and pea to different P availabilities in a high yielding environment (e.g.: yield higher than 10 Mg ha-1 for wheat). Two experiments were conducted in southern Chile. Treatments consisted of the combination of (i) two crops (spring-bred wheat and pea) and (ii) three rates of P fertilization (0 (P0), 100 (P1) and 250 (P2) kg P ha-1). Grain yield of wheat was more sensitive to P deficiency than pea. Wheat showed consistently higher (P < 0.01) PUE than pea, averaging 195 and 125 g yield g-1 P available, respectively. This was principally ascribed to the highest (P < 0.01) P utilization efficiency of wheat (430 vs. 249 g yield g-1 P uptake for wheat and pea, respectively). On the contrary, the P uptake efficiency was slightly different for these crops (0.44 and 0.49 g P g-1 P available, respectively). However, these crops presented different strategies for P acquisition. Wheat had a higher (P < 0.01) soil exploratory capacity than pea, while pea showed a higher (P < 0.01) P uptake per unit of root length than wheat. Wheat showed higher PUE than pea; however, crop differences are ascribed to differences in phosphorus utilization rather than to phosphorus uptake efficiency. This information could contribute to optimized soil P use and improved crop fertilization management. <![CDATA[<b>Determining soil indicators for soil sustainability assessment using principal component analysis of astan quds- east of mashhad- Iran</b>]]> Soil quality indicators are measurable soil attributes that reveal the soil productivity response or soil-environment functionality that are used to know whether soil quality is improving, remain constant, or declining. These characteristics could be assessed by different indices such as sustainability index approach (SI) based on the threshold levels of soil indicators and cumulative rating approach (CR) based on crop production limitations, which show the sustainability of soil ecosystem in terms of soil degradation. Since Iran is situated in arid and semi-arid climatic conditions, this research was conducted in agriculture fields of southeast of Mashhad, Iran for comparing these two approaches. Sixty three soil samples (0-30 cm) were collected and nine soil properties such as pH, electrical conductivity (EC), soil organic carbon (SOC), soil particle-size distribution, available water holding capacity (AWHC), bulk density (BD), air capacity (AC), relative field capacity (RFC) and sodium adsorption ratio (SAR) were measured. All these measurements were considered as total data set (TDS). Principal component analysis (PCA) was used to select more effective indicators to conform the minimum data set (MDS). There was a strong correlation between SI and CR (R²=0.69, p <0.05). Only six soil indicators selected as MDS (pH, SOC, AWC, BD and SAR) were correlated (p<0.01) significantly with SI and CR. These SI and CR results showed more promising effects on soil sustainability. PCA was found a suitable method for selecting the more effective indicators having R²= 0.77 (p <0.05) (CR-MDS versus CR-TDS) comparable with R²= 0.80 (p <0.05) (CR-MDS versus SI) to use less soil data input in assessing soil quality in arid zone. <![CDATA[<b>Characterization of humic acids extracted from biosolid amended soils</b>]]> The aim of this study was to evaluate the changes produced in the chemical, acid-base and structural properties of soil amended (biosolids) and HAs incubated at different times. In the current work the amendments were conducted with biosolids at different doses (30, 90 and 180 t ha-1) on Colina (CLN) soil for 1, 2, 4 and 6 months. The acid-base characterization of extracted humic acids (HAs) showed a slight impact on Atotal (total acidity, mEq g-1), at 30 and 90 t ha-1 while at 180 t ha-1 the greatest increase was observed [from 10.5±1.61 (control) to 17.9±0.30 (6 months of incubation)], without evolution over the incubation time. The Aphenolic (phenolic acidity, mEq g-1) acidity behaves similarly while Acarboxylic (carboxylic acidity) remains constant over time and applied doses. The application of 13C solid state NMR technique revealed higher abundance of aromatic C (CLN 43.5%) over alkyl C (21.4%) compounds. Aromatic C presents a decrease at high biosolid doses, which occurs simultaneously with alkyl C increase when using the same surveyed doses. Therefore, it might be considered that through the addition of biosolids, components such as fatty acids, amino acids or paraffinic structures are incorporated. As a result of biosolids addition, carboxylic C content remains steady, which agrees with the A COOH behavior previously determined. <![CDATA[<b>Effects of late defoliations on chemical and sensory characteristics of cv.</b> <b>uva longanesi wines</b>]]> In this study we investigated the effects of late leaf removal on the berry and wine composition and on wine sensory characteristics of Uva Longanesi, a late maturing red Italian grape variety, which wines are characterized by high levels of alcohol and excessive astringency, the latter apparently intensified by late defoliation practices. During 2008 season, spur-pruned trained vines were submitted to manual defoliation (4 basal leaves) at the onset (DEF I, 210 DOY) or at the end (DEF II, 231 DOY) of veraison and compared with non-defoliated plants (CON). On every DEF II vine, since defoliation until harvest, a cluster was shaded (DEF II + shading). A decrease of the berry soluble solids and skin anthocyanins was found in DEF I vines. Defoliation modified composition and sensory characteristics of wine with DEF II having higher alcohol strength and astringency compared to DEF I, whereas CON wines displayed intermediate values. The practice and timing of partial late defoliation greatly affected the chemical and sensory attributes of wine. <![CDATA[<b>Sorption and mobility of dimethenamid in a volcanic soil amended with liquid cow manure</b>]]> This work studied the sorption and mobility of dimethenamid (2-chloro-N-(2,4-dimethyl-3-thienyl)-N-(2-methoxy-1-methylethyl)-acetamide) in soil amended with liquid cow manure (LCM) at doses equivalent to 0, 100, 200 and 300 thousand L ha-1 (D0, D100, D200 and D300 respectively). For the batch sorption study the amended soils were previously incubated for 30 days under controlled conditions. The mobility was evaluated under field conditions, determining the herbicide retained in different soil profiles and its concentration in soil solutions sampled with ceramic suction cups. Application of LCM at the two lowest doses (D100 and D200) did not modify dimethenamid adsorption, however adsorption increased at D300 (Kfoc = 62.1) as compared with D0 (Kfoc = 42.3). This result could be explained by the higher content of dissolved organic matter in D300, since the addition of LCM does not change the organic matter content in the soil. The results of the field trials showed that D300 adsorbed the highest amount of dimethenamid in the upper layer of soil, and that the amount of dimethenamid in leachates was lower than that of D0. The results showed that high doses of amendment contribute to higher herbicide retention in the topsoil, reducing leaching.