Scielo RSS <![CDATA[Journal of soil science and plant nutrition]]> vol. 11 num. 4 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<b>Selenium uptake and its antioxidant role in ryegrass cultivars as affected by selenite seed pelletization</b>]]> A greenhouse study was carried out to evaluate the effect of seed pelletization with increasing selenite doses (from 0 to 60 g Se ha-1) on the yield, Se uptake and the antioxidant responses of three ryegrass cultivars (Aries, Nui and Quartet) cultivated on an Andisol during two consecutive growth periods. In addition, a second assay was conducted to determine the residual effect of Se in the shoots during four consecutive plant cuts. Results showed that selenite-pelleted seeds at rates up to 60 g Se ha-1 did not influence the yield of shoots and roots of the three ryegrass cultivars. Selenium concentration in shoots and roots steadily increased as a consequence of increased Se supply, and it was accumulated mainly in the roots. Plants of the different cultivars accumulated similar amounts of Se in their shoots, but Quartet roots built up greater Se concentration than those of Aries or Nui at rates of application above 35 g Se ha-1. Whereas Se doses above 10 g ha-1 increased the shoot Se concentration in the two yields of the three ryegrass cultivars to suitable levels according to the minimum dietary requirement of beef and dairy cattle, the residual effect of Se was maintained through four cuts at Se supply of 30 and 60 g ha-1. Likewise, the different cultivars displayed differential patterns of lipid peroxidation in response to the added Se. During the growth period, reductions of the oxidative damage of membranes were accompanied by inhibition of SOD in Aries and Nui and by the activation of GSH-Px antioxidant enzymes in the three ryegrass cultivars. Thus, in our study the benefits of Se on the plant health were closely related to an enhancement of the antioxidant system in the ryegrass cultivars. In summary, our results indicate that selenite-pelleted ryegrass seeds seem to be a promissory tool to increase both the Se content and the antioxidant ability of pastures. Its potential use requires, however, to be evaluated under field conditions in Se deficient soils. <![CDATA[<b>Soil properties and grape yield affected by rock biofertilisers with earthworm compound</b>]]> Grapes are an important crop in several countries, including Brazil. This study was conducted to evaluate the potential of PK rock biofertilisers on grapes (Vitis vinif-era) grown in the San Francisco Valley of the Brazilian semi-arid region. Three sources of PK fertilisers, PK soluble fertilisers, PK rock biofertilisers, and powdered PK rocks, which were all mixed with earthworm compound, and a control treatment consisting only of earthworm compound were tested at three rates. The soil pH, available P and K, exchangeable Ca+2 and Mg+2, soluble S-SO4-2, total Fe and organic carbon were analysed, and the grape yield was evaluated. The soil pH was affected by the fertilisation treatments and was reduced by the application of PK biofertiliser. The available P and K, soluble S-SO4-2, exchangeable Ca and Mg, total Fe and organic carbon in the soil increased with the application of the PK biofertilisers. The soluble fertiliser had a significant effect (p=0.01) on the recommended rate of the grape yield, but no significant difference was observed between the PK soluble fertiliser and biofertiliser at 150% of the recommended rate. Rock biofertilisers may be used as a source of P, K, S-SO4-2 and Fe for grape production in soil with low available P and K, especially if applied at a 150% recommended rate. <![CDATA[<b>Effects of grazing on the soil properties and C and N storage in relation to biomass allocation in an alpine meadow</b>]]> Livestock grazing is one of the most important factors influencing the above-ground community composition and structure in a natural grassland ecosystem. Different grazing intensities also have the potential to alter soil C and N storage substantially in grasslands. We conducted a field community study and soil analyses to determine the effects of different grazing intensities on the above-ground community and soil properties in an alpine meadow on the Tibetan Plateau. Our results showed the following: (i) the vegetation height, coverage, and above-ground biomass significantly declined with increased grazing intensity, but the species richness reached the highest level in a moderate grazing intensity meadow; (ii) grazing had a significant positive effect on soil properties in that the soil moisture content, soil organic carbon concentration, soil total nitrogen concentration, soil available nitrogen, soil total phosphorus, and soil available phosphorus significantly increased with increased grazing pressure; and (iii) soil C and N storage also significantly increased with increased grazing pressure; altogether, these increases had a significant positive correlation with the increase of below-ground biomass allocation. Our results indicated that higher grazing intensity might have a potentially positive effect to increase the soil C and N storage in alpine meadows. However, from a long-term perspective, moderate grazing may help to achieve a balance between species diversity protection, livestock production and soil C and N management. <![CDATA[<b>Organic matter distribution in aggregate sizes of a mollisol under contrasting management</b>]]> Total and particulate organic matter content in different aggregate sizes can be used as an indicator of land use effect. We hypothesized that tillage reduction increases total (SOC) and particulate soil organic C (POC) contents and the stability of larger aggregates of high-SOC-content Mollisols. Three management systems (continuous pasture (Pp), and continuous cropping under conventional tillage (CT) and no-tillage (NT)) were evaluated. Oven dried soil samples (0-5 and 5-20 cm), were wet sieved through 2000, 250 and 50 |im sieves after immersion (IW) and capillary (CW) wetting. Particulate organic matter (>50 |im) was separated in both the whole soil and in each aggregate fraction, SOC and mineral associated organic C contents were determined, and POC was calculated by subtraction. Reduced soil disturbance (Pp and NT) yielded more SOC and POC in the whole soil and macroaggregates with higher stability (Pp>NT>CT). Under Pp, macroaggregates showed the highest SOC and POC. Under NT, macroaggregates showed higher SOC and POC and aggregate stability than CT though lower than Pp. Less tillage-induced disruption (Pp and NT) led to higher SOC and POC contents in more stable macroaggregates but continuous no-tillage appeared not to be enough to reverse the effects of long lasting conventional management practices on these Mollisols. <![CDATA[<b>Calcium sulfate ameliorates the effect of aluminum toxicity differentially in genotypes of highbush blueberry <i>(Vaccinium corymbosum </i>L.)</b>]]> The effect of gypsum (CaSO4) amendment in the reduction of Al phytotoxicity of blueberry cultivars differing in Al resistance (Legacy and Brigitta, Al-resistant and Bluegold, Al-sensitive) was studied in a Hoagland's nutrient solution under acidic conditions for 2 weeks. Treatments were: Control (Hoagland solution), 2.5 mM CaSO4, 5 mM CaSO4, 100 &mu;M Al (AlCl3), 100 &mu;M Al + 2.5 &mu;M CaSO4, 100 M Al + 5 mM CaSO4. Physiological, biochemical and chemical features of leaves and roots were determined to establish the amendment efficiency in the reduction of Al toxicity in these cultivars. Results showed that under Al toxicity the three investigated cultivars accumulated high Al concentrations in leaves and roots. These concentrations decreased with CaSO4 application. Statistically significant interactions among Al in leaves but not in roots (p=0.719) and cultivars (p<0.001), were found. The lowest Ca concentration was found in the most Al-sensitive cultivar (Bluegold) and the highest in the more Al-resistant cultivars (Legacy and Brigitta). Among the underlying processes affected by Al stress in these blueberry cultivars the most evident changes were exhibited by the Al-sensitive cultivar Bluegold, where the photosynthetic performance decreased showing a slight recovery in presence of gypsum amendment at the end of experiment. Instead, the more Al-resistant cultivar (Legacy) did not change its photosynthetic parameters in presence of the gypsum amendments during the treatment, whereas in Brigitta, only a slight recovery at the end of treatment was evidenced by the gypsum application. Thus, in relation to these parameters the gypsum amendment was efficient in complete recovery from the toxic Al effect in the Al-resistant cultivar Brigitta and a slight recovery of the toxic Al effect in the Al-sensitive cultivar Bluegold. Nonetheless, this amendment is a good alternative to ameliorate Al toxicity in Al-sensitive cultivars and additionally provides a good source of Ca and S. <![CDATA[<b>Nutrient uptake by grape in a Brazilian soil affected by rock biofertilizer</b>]]> PK rock biofertilizers made from rocks and elemental sulphur inoculated with Acidithiobacillus improve yield of many short cycle plants similarly to soluble fertilizers. This study aims to evaluate the potential of PK rock biofertilizers for grape cultivation in the Brazilian San Francisco Valley. Three sources of P and K were compared: (a) soluble fertilizers, (b) biofertilizers plus elemental sulphur inoculated with Acidithiobacillus, and (c) ground phosphate and potash rocks, all at three application rates. A control treatment without P and K fertilization was added. Earthworm compound was applied as N source in all treatments. Grape (Vitis vinifera cv. Italia Pirovano) was cultivated in a dystrophic Planossol (medium texture) at the San Francisco River in the Brazilian Semiarid. P, K, Ca, Mg, S-SO4(2-) and Fe concentrations were analyzed in grape leaves and fruits. The results showed adequate leaf contents of S-SO4(2-), K, and Fe with PK biofertilizer application plus earthworm compound, which indicates this may be alternative to soluble fertilizer for grape in soils with low available P and K. <![CDATA[<b>Screening, evaluation and selection ofphosphate-solubilising fungi as potential biofertiliser</b>]]> Phosphate-solubilising saprophytic fungi have a potential application in plant nutrition; therefore, the aim of this study was 1) to perform a screening and isolation of native phosphofungi from volcanic soils of southern Chile, 2) to select a liquid medium for the evaluation of these phosphofungi and 3) to test a selected phospho fungus as a biofertiliser in a volcanic soil. The phosphofungi were screened using Martin medium (rose bengal-streptomycin agar) with calcium phosphate (Ca3(PO4)2) or calcium phytate as the phosphorus source. Six promising strains (Penicillium sp., Penicillium albidum, Penicillium thomii, Penicillium restrictum, Penicillium frequentans and Gliocladium roseum) were evaluated in the liquid media of Agnihotri, Asea-Wakelin, Pikovskaya and Nahas. The soluble phosphorus, acid phosphatase activity, pH and fungal biomass were determined. In most soils, the greatest proportion of phosphofungi solubilised organic P. The Asea-Wakelin medium appears to be the medium of choice for the quantitative evaluation of phosphofungi isolated from the volcanic soils tested. Penicillium albidum was selected as a potential biofertiliser due to its capacity to solubilise both inorganic and organic P via its specific solubilising activity (64 mg P/g fungus), phosphatase secretion and enhancement of the growth and mineral nutrition of lettuce plants growing in a volcanic soil. <![CDATA[<b>Comparative effects of organic and conventional apple orchard management on soil chemical properties and plant mineral content under Mediterranean climate conditions</b>]]> The effects of conventional and organic management systems on soil chemical properties and leaf nutrients under Mediterranean conditions were studied over a 2-year period on adjacent commercial apple orchards in Southern Greece. The soil in both orchards was characterised as a clay loam-clay and was uniform in morphological and physical properties. The results indicated no significant differences in soil chemical properties between the different management systems, including soil organic matter (SOM), pH, cation exchange capacity (CEC) and C/N ratio. However, soil samples from the conventional orchard exhibited significantly higher values (p< 0.01) of electrical conductivity (EC) and higher concentrations of K, Ca, Na, Cu and Zn, which were likely the result of chemical fertiliser application. Despite the fact that organic systems promote the accumulation of soil organic matter and fertility over time through the use of organic sources, in our study, the SOM values declined, suggesting that the type and the rate of organic matter input in the organic orchard were insufficient. The leaf nutrients, with the exception of P and Ca, were within the sufficiency range in both management systems. The present findings did not provide evidence of major differences in the leaf macronutrient content between conventionally and organically grown apple trees. Nevertheless, our leaf analysis revealed higher concentrations of Zn in the conventionally grown trees and opposite results for Cu, probably due to the extensive use of copper-containing fungicides in organic orchards in Greece. <![CDATA[<b>Tolerance to iron chlorosis in non-grafted quince seedlings and in pear grafted onto quince plants</b>]]> Grafting is a technique that may affect plant tolerance to iron chlorosis in plants cultivated for their fruit. Therefore, the objective of this study was to evaluate the tolerance of non-grafted quince seedlings and pear grafted onto quince plants cultivated in pots with alkaline soil. The experiment was conducted in a greenhouse at the University of Cordoba, Spain, in pots (3 L) filled with alkaline soil, with one plant per pot. The treatments consisted of two genotypes, quince (Cydonia oblonga Mill) semi-woody rooted cuttings, cultivar BA29, and pear (Pyrus Communis L.), cultivar Ercolini, grafted onto quince cultivar BA29 (rootstock), and two nutrient solutions with and without iron (80 &mu;M Fe-EDDHA) arranged in a completely random design with eight repetitions. Each pot received 250 mL of the nutrient solution on June 3rd, 2010. Chlorophyll indirect measurements and the main stem length were evaluated for six weeks after the commencement of the treatments. During the last week, the main stem dry matter weight and the leaf total iron content were determined. It was found that grafting pear seedlings onto quince rootstock resulted in a higher tolerance to iron deficiency than when quince was not grafted. Non-grafted quince plants without iron in the nutrient solution, compared to the results with its application, showed low SPAD (Soil-Plant Analyses Development) values and resulted in plants with a lower leaf iron content and lower dry matter production; however, decreased seedling stem growth was observed only in the last week of cultivation. <![CDATA[<b>Effects of topsoil loss on wheat productivity in dryland zones of Chile</b>]]> Considering that the most important processes of biogeochemical cycles occur in the upper first centimetres of the soil, minor degrees of erosion may affect crop productivity, especially in the case of low input dryfarming production systems, which dominate the central coastal areas of Chile. The purpose of this study was to evaluate the effect of topsoil loss on wheat productivity in dryfarming areas with Mediterranean climates in Central Chile. The experiment was conducted on a Chilean Alfisol (Pencahue; 35°18'53"S and 71°53'40"W), and the topsoil of this soil was progressively removed from a depth of 2 to 18 cm (2, 6, 10, 14 and 18 cm). Once the plots (25 m²) were prepared, winter wheat (Triticum aestivum L.; cultivar Pandora-INIA) was sown by applying the traditional techniques of the zone. A design was established on randomised blocks with six treatments and three replications. After one growing season, the results showed significant differences (p<0.05) in grain yield (kg ha-1) between the control treatment (T0) and the treatment with 18 cm of soil removed (T18) with productivity decreasing by 35%. Furthermore, most of the considered productivity parameters were negatively correlated with the depth of soil removed. The results highlighted the importance of topsoil fertility and depth in crop yield.