Scielo RSS <![CDATA[Journal of soil science and plant nutrition]]> http://www.scielo.cl/rss.php?pid=0718-951620170003&lang=en vol. 17 num. 3 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.cl/img/en/fbpelogp.gif http://www.scielo.cl <![CDATA[<b>Role of</b> <b>Exogenous 24-Epibrassinolide in</b> <b>Enhancing</b> <b>the</b> <b>Salt</b> <b>Tolerance of</b> <b>Wheat</b> <b>Seedlings</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000300001&lng=en&nrm=iso&tlng=en To understand the functions of exogenous 24-Epibrassinolide (EBR) in enhancing the salt tolerance of wheat (T. aestivum L.) seedlings to salt stress, a hydroponic experiment was performed to investigate the effects of EBRon chlorophylls,root activity, H+-ATPase, malondialdehyde (MDA), electrolyte leakage, free proline, soluble protein, reactive oxygen species (ROS), antioxidant enzymes and minerals content in wheat plants subjected to non-stress conditions or salt stress (120 mM NaCl) with foliar application of EBR (1, 10 and 100 nM). Results showed that spray of low concentrations EBR (1 and 10 nM) under non-stress conditions could promote wheat plant growth. 120 mM NaCl induced osmotic stress, oxidative stress and imbalance in mineral nutrients absorption. However, EBR enhanced the ability of resistance to osmotic stress by increasing free proline and soluble protein content, and enhanced the ability of resistance to oxidative stress by increasing antioxidant enzymes activities. As a result of increase of chlorophyll content, root activity and H+-ATPase activity, the inhibition of K, Ca, Mg, Fe and Zn uptake was ameliorated and consequently, decline in plant growth induced by NaCl stress was alleviated. Based on these results, we conclude that EBR had a positive role in regulating wheat growth and development under salt stress, and spray of 10 nM EBR had the most significant alleviating effect against NaCl toxicity. <![CDATA[<b>Contribution of mineral N to young grapevine in the presence or absence of cover crops</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000300002&lng=en&nrm=iso&tlng=en The presence of cover crops in vineyards may decrease the availability of nitrogen (N) derived from fertilizer to grapevines. The present study aimed to evaluate the recovery of urea-15N and growth of young grapevines with and without natural vegetation in plant rows. The study was conducted in southern Brazil on one-year-old Chardonnay grapevines grown in soils with and without cover crops. The grapevines were subjected to the application of 40 kg N ha-1 in the form of urea-15N at 3% 15N atom excess. Dry matter yield, total N and fertilizer N were assessed in grapevines and soil layers. A small amount of N that is applied during the growing season of the grapevines is readily assimilated by the plants. The maintenance of cover crops in young vineyards may favor the maintenance of higher levels of N in the subsurface layers of the soil, contributing to the nutrition of the grapevines in the following growth cycles. The presence of cover crops reduced the importance of nitrogen fertilization in the growth cycle of grapevines because a large part of N absorbed by grapevines was derived from other sources. Nitrogen derived from the fertilizer applied to the soil in the presence or absence of cover crops was mainly concentrated in the newly-formed vegetative grapevine organs (leaves and shoots). <![CDATA[<strong>Possible use of struvite as an alternative phosphate fertilizer</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000300003&lng=en&nrm=iso&tlng=en Struvite, from human urine, is an alternative phosphorus (P) fertilizer. This study evaluated P release from struvite and its effectiveness for maize in Inanda (Ia), Sepane (Se) and Cartref (Cf) soils. Phosphorus sorption isotherms were determined, an incubation study determined the release pattern of P from struvite, and a pot trial compared struvite with single superphosphate (SSP) on maize P uptake. The amount of P at equilibrium (where Q = 0) in the Cf was 1.39 mg L-1, followed by Ia and Se with values of 0.17 and 0.13 mg L-1, respectively. Buffer coefficients were in the order Ia > Se > Cf with values of 454, 71 and 50 mg kg-1/mg L-1, respectively. The extractable P in all three soils increased with time, with evidence of declining P release after Day 8. Struvite was most effective as a P source in the Cf followed by Se and Ia. Compared to SSP, there was significant improvement in maize grown on the Cf, while the reverse occurred in the Se. Maize grown in the Ia did not respond to either struvite or SSP. It was concluded that the phosphorus sorption was the main limiting factor that governed struvite effectiveness as a P source. <![CDATA[<b>Soil amendment with high and low C/N residue -influence of low soil water content between first and second residue addition on soil respiration, microbial biomass and nutrient availability</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000300004&lng=en&nrm=iso&tlng=en Soil water content is a major factor influencing organic matter decomposition. In our previous study, we showed that microbial biomass and nutrient availability after the second residue addition is influenced by the C/N ratio of both the first and the second residue (referred to as legacy effect). Different constant soil water content between the first and second residue addition may influence soil respiration, microbial biomass and nutrient availability and also the legacy effect. A loamy soil was unamended (C), or amended with plant residues with either high (mature wheat straw, H) or low C/N ratio (young faba bean, L) on day (d) 0 and d10, giving treatments CH, CL, HH, HL, LL and LH. Between d0 and d10, the soil was maintained at 10, 30 or 50% of water holding capacity (WHC), on d10, before residue addition, soil water content was adjusted to 50% WHC and maintained at this water content until d20. Cumulative respiration from d1 to d10, MBC and MBN on d1 and available N and P on both d1 and d10 were lower at 10% than at 50% WHC. When L was added on d10, cumulative respiration from d11 to d20, microbial biomass C and N on d11 and available N on d20 were higher in soil kept at 10% WHC in the first 10 days than in that maintained at 50% WHC. The previous water content had little effect on respiration and nutrient availability when H was added on d10. Differences in MBC, MBN, MBP and available N on d11 between HL and LL and between LH and HH were greater when the water content in the first period was 10% WHC compared to 50% WHC. It can be concluded that water content between residue additions influences soil respiration and nutrient availability not only directly, but also after rewetting and residue addition. <![CDATA[<b>Extractability and bioavailability of phosphorus in soils amended with poultry manure co-composted with crop wastes</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000300005&lng=en&nrm=iso&tlng=en Intensive livestock production and poor agricultural management have resulted to excessive loading of soil with phosphors (P), thereby contributing to environmental pollution and impairment of water quality. A study was carried out to determine the extractability and bioavailability of P in soils treated with poultry litter (PL) co-composted with sugarcane and cabbage wastes. The manure was applied based on total P contents at 200 and 400 kg P ha-1, with maize (Zea mays L.) as the test crop. The co-composted PL increased maize growth relative to PL alone with the best growth occurring at the treatment rate of 400 kg P ha-1. Maize biomass and available P in soil varied in the order PL co-composted with sugarcane waste and cabbage waste (%) 50 > 33 > 25 > 0. Phosphorus contents in maize shoot were higher in sandy clay than silt loam soil and its recovery was higher in soil treated with PL co-composted sugarcane waste than co-composted with cabbage waste. An amendment with co-composted PL increased the extractable P fractions and P availability in the soils. The P fractions in the post-harvest soils varied in the order HCl-P > H2O-P > NaHCO3-P > NaOH-P and the fractions were significantly higher in the sandy clay than the silt loam soil. Also, the PL co-composted with sugarcane waste exhibited higher levels of P fractions in soils than co-composted with cabbage waste. Thus, co-composting poultry manure with crop wastes would better improve plant growth and P nutrition than sole-composted manure. <![CDATA[<strong>Carbon mineralization in acidic soils amended with an organo-mineral bentonite waste</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000300006&lng=en&nrm=iso&tlng=en Bentonite based organic-mineral wastes contains high concentrations of organic matter and plant nutrients and hence presents a high potential as a soil amendment. However, it also can have high salinity and high copper concentrations that may cause negative effects on microorganisms when the soil is amended with this type of wastes. In this work, the effect of soil amendment with a bentonite based winery waste on soil carbon mineralization was studied in acidic vineyard soils as an indicator of soil quality. The carbon mineralization in the waste is significantly lower and slower than that in the studied vineyard soils despite its significantly higher amount of organic carbon. However, when the bentonite winery waste was added to the soils, the carbon mineralization showed positive priming effects (increased between 78 and 337%). Therefore, reductions in the carbon mineralization, and hence changes on short-term organic matter turnover are not expected after bentonite waste amendment in acid soils. <![CDATA[<b>Environmental risk of trace elements in P-containing fertilizers marketed in Brazil</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000300007&lng=en&nrm=iso&tlng=en The input of trace elements (TEs) into agricultural soils from phosphate fertilizers may compromise the sustainability of agroecosystems and pose a risk to human health. We evaluated 53 sources of P marketed in Brazil in regard to As, Cd, Cr, Hg, and Pb concentrations in order to assess the risks associated with their application to soils. Based on the concentrations of TEs and the consumption of different sources, we estimated the amounts of TEs added annually to agricultural soils. As, Cr, Pb, and Hg concentrations did not exceed those found in fertilizers sold in other regions of the world. Phosphate rocks had Cd concentrations that were twice as high as any other source. The potential risk of Cd affecting soil quality is at least nine times higher than that of the other TEs assessed. Due to high consumption, monoammonium phosphates and single superphosphates are the main sources of TEs to Brazilian soils. In general, TEs in P-containing fertilizers sold in Brazil did not pose a high human health risk in a medium time frame. Nevertheless, intensive application of fertilizers with high concentrations of TEs requires monitoring of the TE accumulation in soils to ensure the sustainability of agroecosystems. <![CDATA[<b>Pepper crop residues and chemical fertilizers effect on soil fertility, yield and nutritional status in a crop of <i>Brassica oleracea</i></b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000300008&lng=en&nrm=iso&tlng=en Effects of pepper crop residues as amendment and their optimal application rates on an agricultural soil have been sparsely studied. A comparative study of the development of a broccoli crop has been conducted using chemical fertilizers (CF) and fresh pepper crop residues (CR) at different application rates during two crop cycles. We measured soil chemical and biochemical properties and broccoli yield, quality parameters and nutritional status. We found that CR at highest application rate increased total N (Nt), potentially mineralizable N (Nmin), microbial biomass N, Nmin/Nt, Nmin/Nsol and urease and alkaline phosphatase activities compared to CF treatment and control (CT). The maximum broccoli yields were obtained in CF3 (383 kg N ha-1 applied as CF) and all CR application rates, especially CR3 (383 kg N ha-1); this corresponded with season available N (initial available N plus available N applied as CF or CR) of 545 - 598 kg N ha-1. Results demonstrated that pepper CR applied at the highest rate (16.7 - 19.2 t ha-1), with a minimum chemical fertilization enhances crop yield and quality, with significant increments in soil quality and fertility compared to chemical fertilization. <![CDATA[<b>Screening of sunflower (<em>Helianthus annus </em>L.) accessions under drought stress conditions, an experimental assay</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000300009&lng=en&nrm=iso&tlng=en Drought is the major abiotic stress that limits the crop production at drastic level. Screening of tolerant accessions from available germplasm is the basic step in plant breeding. Sunflower is becoming popular and major oilseed crop in world but unfortunately it is drought sensitive. Screening in field has uncertainties due to the uncontrolled conditions, interaction of biotic and abiotic stresses and variability in environmental factors. Response of the sixty sunflower accessions to drought stress at germination and seedling stage was examined by using polyethylene glycol (PEG-6000) as drought simulator under laboratory. Normal and drought stress treatments i.e. T1= zero (control), T2= -1.33 MPa and T3= -1.62 MPa were developed by dissolving 0, 15g and 20g Polyethylene Glycol (PEG-6000) in 100 mL distilled water and a completely randomized design with three replications were used. Promptness, germination, seedling height, fresh weight, dry weight and stress indexes were determined to evaluate the response of sunflower accessions under normal and PEG simulated drought stress treatments. Principal component analysis was used to select the drought tolerant and sensitive accessions. The accessions 017583, A-75, A-79, 017592, G-33, A-48, A-23, G-61, HBRS-1 and 017566 were selected as drought tolerant while, CM-621, 017577, HA-124, HA-133, HA-342 and HA-341 were as drought sensitive. This study may be helpful for the comparison of drought indexes in a controlled experimental assay and for the identification of drought tolerant sunflower cultivars to be used in further breeding programs. <![CDATA[<strong>Soil fertility changes in vineyards of a semiarid region in Brazil</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000300010&lng=en&nrm=iso&tlng=en Cultivation can substantially change soil quality through improvement or degradation of the physical and chemical characteristics. Vineyard soils are sensitive to soil changes due to the intensive chemical input. This study assesses the soil fertility changes in vineyard soils of the São Francisco valley in Northeastern Brazil during different cultivation time spans (5, 6, 8, 10, 12, 15, and 16 years). An area with natural vegetation (Caatinga) was used as a reference area. We analyzed pH, exchangeable contents of Ca, Mg, Na, K, and Al, potential acidity (H+Al), available P, total organic matter, sum of bases, CEC, Al saturation, and base saturation at depths of 0-20 and 20-40 cm. Univariate and multivariate analyses were used for data evaluation. The results showed that soil fertility changes were closely related to cultivation time spans. Contents of organic matter, Ca, Mg, and K were increased in most of the vineyard soils. The management of P fertilization deserves attention as the very high concentrations in soil are prone to leach and can contribute to triggering eutrophication. Discriminant and factor analyses proved to be useful tools for distinguishing the effects of management in the cultivated areas and helping to achieve sustainable land use in such fragile agro-ecosystems. <![CDATA[<strong>Yield and nitrogen use efficiency of rice-wheat cropping system in gypsum amended saline-sodic soil</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000300011&lng=en&nrm=iso&tlng=en It is critical to determine nitrogen use efficiency (NUE) to find to which extent higher rates of nitrogen can improve crop yield with effective management practices. Two-year field experiments were conducted to investigate yield and NUE of rice-wheat cropping system on saline-sodic soil. Treatments included were two nitrogen (N) application rates, i.e. 15% (N115)and 30% (N130) higher than the recommended rates for normal soil, along with gypsum at the rates of 50% (SGR50) and 100% (SGR100) of soil gypsum requirement. Results revealed relatively highest NO3- leaching for rice (161 and 145 mg L-1) and for wheat (97 and 93 mg L-1) during 2011-12 and 2012-13, respectively in N130 + SGR100. In this treatment, crop yield and NUE were the highest as compared to the other combinations. This resulted in reduction of yield gap by two-fold (53% to 26%) between saline-sodic and normal soils for rice-wheat. Interestingly, N130 + SGR100 proved most effective during the first year, however, N100 + SGR100 became more profitable in the subsequent year. Pearson correlation coefficients predicted significant positive correlation (p < 0.01) of yield and NUE with soil organic matter, cation exchange capacity and infiltration rate while inverse relationship was observed with electrical conductivity, pH, CaCO3, and bulk density. Based on data, it is concluded that the recommended N application together with SGR100 would be environmental-friendly and economically viable option for rice-wheat cropping system in saline-sodic soils. <![CDATA[<strong>Soil water content during and after plant growth influence nutrient availability and microbial biomass</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000300012&lng=en&nrm=iso&tlng=en Two experiments were conducted to study the effect of soil water content on soil respiration, microbial biomass and nutrient availability in planted and unplanted soil. In the first experiment, wheat was grown in pots for four weeks in soil that was kept dry between one and four weeks. In the second experiment, soil was maintained at 50% of water-holding capacity (WHC) for four weeks and either planted with wheat or left unplanted. After removal from the pots, soil was kept at 50% WHC or quickly dried to 40, 30, 20 or 10% of WHC. The soils were incubated four weeks during which soil respiration, microbial biomass and nutrient availability were measured. In the first experiment, shoot and root biomass and microbial biomass carbon were higher in constantly moist than constantly dry soil, but the reverse was true for available N. In the second experiment, cumulative respiration was two-fold higher in planted than unplanted soil and decreased with water content, with a smaller decrease in planted soil. Microbial biomass carbon on days 5 and 10 was higher at 10% than at 50% WHC in planted soil, but not affected by water content in unplanted soil. We conclude that soil microbes can maintain higher respiration at low water content despite low biomass because activity per unit biomass is high. <![CDATA[<b>Diverse salinity responses in <i>Crithmum maritimum</i> tissues at different salinities over time</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000300013&lng=en&nrm=iso&tlng=en Crithmum maritimum (sea fennel) withstands high salinity, and to better understand how different protective mechanisms against salinity are activated, young seedlings were exposed to increasing concentrations of NaCl (0 to 512 mM) over six weeks. Plant survival and chlorophyll content were reduced at >85 mM NaCl and growth was affected at > 341 mM NaCl. Relative water content fell and Na+ accumulated more in leaves than in roots. Induction of Na+/H+ antiporter expression reached a maximum at 427 mM NaCl in both tissues. Salinity induced the accumulation of proline, soluble sugars and glycine betaine. All three accumulated to higher levels in leaves than roots and greatest accumulation was after 6 weeks and the highest salt concentrations. Hydrogen peroxide levels fell with increasing salinity in leaves, while ascorbic acid and catalase activity rose. Overall, the most dramatic changes occurred after six weeks of saline stress but different mechanisms were activated at different salinity thresholds and in the two tissues. Key salinity thresholds in the response of Crithmum maritimum to salinity stress are identified activating different mechanisms. At 85 mM NaCl roots reach osmotic adjustment, at 171 mM further osmolyte protection mechanisms are activated, at 256 mM NaCl leaves reach osmotic adjustment, at 341 mM plant growth is affected and at the highest salinity tested, 512 mM, protective mechanisms are affected in leaves but not in roots. <![CDATA[<strong>Assessment of methods to determine soil characteristics for management and design of irrigation systems</strong>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000300014&lng=en&nrm=iso&tlng=en Irrigation system design and irrigation management require appropriate classification of the soil and type of crop match. In Chile, agrological reports are currently being used to determine the homogeneity of soil units and land capability classes: fruit tree production vs orchard design. Agrological studies use a number of soil characteristics, but these do not include hydrophysical properties, which are essential when zoning for irrigation. Therefore, it is necessary to establish a methodology to objectively evaluate soils, based on a quantitative analysis that includes hydrophysical parameters. In this study, different methodologies are proposed for classifying homogenous soil units based on extensive field sampling. The field data was evaluated using two methodologies: 1) the SAG-USDA Manual and 2) in situ sampling of soil’s hydrophysical properties and pedotransfer models. There were differences between the methodologies regarding the zoning soil properties for irrigation system design and management. The methodology based on the SAG-USDA Manual requires auxiliary data in order to provide useful maps for design and management of irrigation systems. Published pedotransfer functions should be carefully assess before their use in large-scale design, as the quality the estimations depends on the data used to derive the equations. Therefore, if field data is available, we recommend calibrating equations using well-known statistical methods such as least square. In this study, the functions obtained describe the properties of interest properly, such as the field capacity for design of micro-irrigation systems. However, predicting wilting point did not give reliable results. <![CDATA[<b>Green manure and compost effects on N-P dynamics in Mediterranean organic stockless systems</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000300015&lng=en&nrm=iso&tlng=en Stockless systems, where plant and animal production are uncoupled, represent a common condition in Mediterranean areas. In organic systems, soil fertility is mainly managed by green manures, whereas composts of plant origin represent suitable soil conditioners. The low P content of these materials, together with the shortage of animal waste availability, determine potential nutrient depletion overtime and, in calcareous soils, P mining conditions. In a two-year field experiment in Central Italy, the effect of green manure vetch (Vicia villosa) (GM+) was compared with a control left fallow (GM-), combined with P-based fertilizers (F) on organic maize (Zea mays). Yields and N-P dynamics were evaluated by direct measurements, nutrient balance and efficiency index. N balance was higher than in GM+ GM- (+71.8 and -23.6 kg N ha-1, respectively). P enriched compost with RP (rock-phosphate) (EP), showed significant improvement in P use efficiency (meanly +34%) than other treatments (unfertilized control (RP), not P enriched compost (NEP)) and P equilibrium in the short run. On the other hand, P-fertilizers and maize residues soil incorporation determined P surplus in a long perspective (up to +10 kg P ha-1). Results emphasize the possibility of P reintegration in stockless organic systems without animal wastes. <![CDATA[<b>The effect of <i>Ecklonia maxima</i> extract on <i>Medicago</i> X <i>Varia</i> T. Martyn biomass</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000300016&lng=en&nrm=iso&tlng=en In 2013 a field experiment was set up in order to determine the effect of Ecklonia maxima extract on the development of the aboveground biomass of alfalfa (Medicago X Varia T. Martyn). The main experimental factor was a biostimulant based on the extract containing plant hormones. The extract was applied to the experimental units in the form of spraying. The following features were determined in the experiment: plant density, the number of shoots per square meter, dry matter weight per square meter, and the ratio of leaves to the entire biomass. The results were processed statistically with the analysis of variance, while differences between means were verified with Tukey's test (p ≤ 0.05). Furthermore, the Pearson linear correlation coefficient and the coefficient of determination were calculated in order to determine the relationship between the number of plants and shoots per area unit and biomass weight. Extract application led to an increase in shoot length and density, and the weight of dry matter in individual harvest, but it did not affect plant density and the ratio of alfalfa leaves. However, a decrease of plant density in consecutive years was observed. <![CDATA[<b>The effects of rainfall intensity and rock fragment cover on soil hydrological responses in Central Chile</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000300017&lng=en&nrm=iso&tlng=en In Chile, 60% of the usable land is affected by erosion and the effects of rock fragment cover, however protecting the soil against these degradation processes have been sparsely studied. Understanding the effects of rainfall intensity and rock fragment cover on soil hydrological processes is a major challenge for the formulation and implementation of proper soil conservation plans. The effects of rock fragment cover on soil erosion rate, surface runoff, sediment concentration and infiltration rate were studied on a Cambisol in Central Chile using the CAZALAC rainfall simulator. Nine rainfall simulations consisting of different combinations of rainfall intensities (70 mm h-1, 90 mm h-1, and 120 mm h-1) and rock fragment cover (0%, 40%, and 70%) were carried out. Rock fragment cover contributed to delay the time to start surface runoff and the amount surface runoff was in most of the cases directly proportional to rainfall intensity and inversely proportional to rock fragment cover percentage. Rock fragment cover reduced surface runoff in up to 72.06% in the case of the highest rainfall intensity. Final infiltration rate increased directly proportional to the percentage of rock fragment cover for each of the studied rainfall intensities. Erosion rate tended to be reduced by rock fragments (82.2% of reduction in the case of the highest rainfall intensity and rock fragment cover), but this positive effects were not always proportional to rock fragment cover percentage. In general, lower sediment concentrations were found in covered soils (more than a tenfold reduction in the case of 120 mm h-1 rainfall intensity). <![CDATA[<b>The biological activities of </b><b>β</b><b>-glucosidase, phosphatase and urease as soil quality indicators</b>: <b>a review</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000300018&lng=en&nrm=iso&tlng=en Soil is a fundamental resource and it is crucial to manage its quality in order to enhance agricultural productivity and environmental quality. Soil enzymes catalyze several biochemical reactions which result in the transformation of organic matter, and the release of inorganic nutrients for plant growth and nutrient cycling. Soil enzyme activities are useful biological soil quality indicators since they are operationally practical, very sensitive, integrative, easy to measure and more responsive to soil tillage and structure than other soil variables. There are several enzymes in soil, but those involved in hydrolases and the degradation of main litter components are used most often for evaluating soil quality. This paper reviews the roles of soil enzymes such as β-glucosidase, phosphatase and urease, as well as the implications of their activities for soil quality. <![CDATA[<b>Impact of wheat straw biochar on yield of rice and some properties of Psammaquent and Plinthudult</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000300019&lng=en&nrm=iso&tlng=en Agricultural organic matter is a major component of organic waste on earth that significantly contributes in environmental pollution. The conversion of organic waste into biochar and addition to soil is the recommended strategy to reduce the negative environmental effects of organic waste and to increase the soil fertility. Therefore, in this study, we evaluated the changes in nutrient concentrations, rice yield and microbial community structure in a Psammaquent and Plinthudult at harvest following incorporation of biochar derived from wheat straw. Wheat straw biochar generated at 300-500˚C under oxygen limited conditions was applied, in a greenhouse experiment to a Psammaquent and Plinthudult at a rate of 3% weight/weight (w/w). The biochar addition to both types of soil significantly increased the soil pH from 4.2 to 6.2 and 4.7 to 6.7, total nitrogen by 135 and 37%, and organic carbon by 90 and 80%, in the Psammaquent and Plinthudult, respectively as compared to the respective controls. The dissolved organic nitrogen (DON) was decreased by 24 and 15% and dissolved organic carbon (DOC) by 40 and 44% in Psammaquent and Plinthudult, respectively. The biochar decreased the concentrations of K leached by 24%, B by 25%, Cu by 80%, Mn by 37% and Zn by 33% in the Psammaquent and B by 50%, Cu by 60%, Fe by 43%, Mn by 69% and Zn by 83% in the Plinthudult as compared to the controls. The wheat straw biochar addition to two soils increased the accumulation of Mn, Mo, Na and Zn in both rice straw and grain and decreased the leaching of nutrients, organic carbon and nitrogen at rice harvest and increased the leaching of Ca, Na, and Mg in both Psammaquent and Plinthudult. The biochar increased the pH, TOC and nitrogen in both soils. The biochar significantly changed the PLFA concentration indicating different microbial community pattern in soils growing rice compared to their controls. Thus, the results indicated that wheat straw biochar increased the productivity of rice in the Plinthudult and Psammaquent. <![CDATA[<b>Phosphorus fractions depletion in the rhizosphere of young and adult maize and oilseed rape plants</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-95162017000300020&lng=en&nrm=iso&tlng=en In alkaline soils, where most of the P is acid soluble, we hypothesize that species that acidify the rhizosphere such as oilseed rape, are more efficient to use soil P than for example maize. In field experiments, adult maize plants extracted more P per unit of root than young plants. Here we hypothesize that older plants access P fractions that younger plants were not able to. Thus, the aim of this research was to study the P fractions used by maize and oilseed rape growing in an acid sandy and a neutral loamy soil and how plant age might affect it. A special pot system was developed in which P uptake by the plants came from roots that grew freely in soil. To obtain rhizosphere soil, a portion of the roots was concentrated to form a root mat on a planar soil surface covered by a fine nylon mesh. Cutting the soil on the other side of the mesh into slices gave rhizosphere soil at different distances from the root surface. We examined the P fractions used by maize and oilseed rape at three growth stages by measuring the depletion of three inorganic (Pi) and two organic (Po) P fractions in the rhizosphere. Oilseed rape did not affect the Po fractions in any of the two soils, and maize only in the acid soil. Both species in both soils depleted only the alkali soluble Pi fraction. The degree of depletion was between 12-26 %. The acid soluble Pi was not depleted by neither oilseed rape nor maize. Plant age had no effect on P fraction depleted or on the degree of depletion.