Scielo RSS <![CDATA[Revista de la ciencia del suelo y nutrición vegetal]]> vol. 9 num. 2 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<strong>EFFECT OF ARBUSCULAR MYCORRHIZAL FUNGAL INOCULATION ON <i>Eucalyptus globulus </i>SEEDLINGS AND SOME SOIL ENZYME ACTIVITIES UNDER APPLICATION OF SEWAGE SLUDGE AMENDMENT</strong>]]> The sewage sludge (SS) represents a source of organic matter although its increasing accumulation need a suitable environmental treatment. Our study analyzed the effect of the interaction between sewage sludge (doses 0, 2, 4, 6 and 8 g per 100 g of soil) and Eucalyptus globulus nursery seedlings inoculated with arbuscular mycorrhizal (AM) fungi as a fertilizers alternative and evaluate its effect on some soil enzyme activities. The seedlings were inoculated with Glomus claroideum, Glomus viscosum, Glomus intraradices and Glomus constrictum, establishing a uninoculated control. The sewage sludge application increased the shoot dry weight and the inoculation with G. viscosum was more effective at 6 g of SS in 100 g soil. The root colonization and succinate dehydrogenase activity was decreased by all doses of SS used. The Fluorescein diacetate activity was increased by the AM inoculation but not by sewage sludge. The (β-glucosidase activity was increased in presence of SS at 6 g 100 g-1. The N and P uptake by the E. globulus plants was higher in presence of sewage sludge and more effective with G. viscosum plant inoculation. In conclusion the application of these amounts of SS promoted the plant growth and can be regarded as a successful biotechnological tool for the greenhouse plant production. <![CDATA[<strong>DEVELOPMENT OF ARBUSCULAR MYCORRHIZAL FUNGI IN THE PRESENCE OF DIFFERENT PATTERNS OF <i>Trifolium repens </i>SHOOT FLAVONOIDS</strong>]]> We tested the effects of the flavonoid 3-methoxi-5,6,7,8-hydroxy-4'hydroxy flavone (NMHTV) isolated from shoots of non arbuscular mycorrhizal (AM) inoculated clover, and of the flavonoids 5,6,7,8-hydroxy-3-methoxy flavone (MH-1); 5,6,7,8-hydroxy-4'-hydroxy flavone (MH-2); and 5,7-hydroxy-3,4'-methoxy flavone (MH-3); isolated from AM clover {Trifolium repens) shoots, on spore germination, hyphal length, hyphal branches and the number of cluster of auxiliary cells or the number of secondary spores (Presymbiotic stage) and on the number of entry points and the percentage of AM colonized root of tomato (Lycopersicum esculentum) by the AM fungi Gigaspora rosea, Giaspora margarita, Glomus mosseae and Glomus intraradices (Symbiotic stage). Non significant effects of the flavonoids isolated from the shoot of mycorrhizal colonized clover on the presymbiotic and symbiotic stages of Gigaspora and Glomus endophytes were found. The flavonoid NMHTV isolated from non AM clover shoot, did not affect the percentage of germination of spores but significantly increased (P < 0.05) the other steps of the presymbiotic stage of Gi. margarita spores when 2 µM concentration was used. The symbiotic stage of Gi. margarita was also significantly increased when 2 µM of the flavonoid NMHTV was applied. This flavonoid had no effect on the presymbiotic development of G. mosseae, G. intraradices and Gi. rosea except when 8 uM concentration was used, which inhibited the hyphal length of Gi. rosea. These results suggest the possible implication of the flavonoid NMHTV in the susceptibility of tomato roots to the AM formation by Gi. margarita. The absence of stimulation of the AM presymbiotic and symbiotic stages in tomato by exogenous application of the newly synthesized flavonoids MH-1, MH-2, and MH-3, in clover shoots after AM colonization, indicated that the autorregulation of the AM symbiosis can be, at least partially, due to the disappearance of flavonoids in AM colonized plants that stimulated the AM symbiosis. <![CDATA[<strong>CATALYTIC POTENTIAL OF SOIL HYDROLASES IN NORTHEAST CHINA UNDER DIFFERENT SOIL MOISTURE CONDITIONS</strong>]]> An incubation test with black soil (Phaeozem), Albic soil (Albic Luvisols), brown soil (Cambisols), and cinnamon soil (Chromic Luvisol) from Northeast China was conducted under the conditions of 10%, 20% and30 % field capacity, and the kinetic parameters of soil urease, phosphatase, and arylsulphatase were determined, aimed to study the changes in the catalytic potential of these enzymes under different soil moisture conditions. All test enzymes exhibited typical Michaelis-Menten kinetic behaviors. The test enzymes exhibited the highest enzyme-substrate affinity (l/Km) at 20% or 30% field capacity. With increasing soil moisture content, the Fmax of test soil urease decreased, while that of soil phosphatase and arylsulphatase increased, with the maximum Vmax/Km of urease at 20% field capacity and that of phosphatases and arylsulphatase at 30% field capacity. To control soil moisture condition could be a feasible way in regulating the biochemical transformation processes of soil nutrients catalyzed by soil hydrolases. <![CDATA[<strong>KINETICS OF SOIL UREASE AFFECTED BY UREASE INHIBITORS AT CONTRASTING MOISTURE REGIMES</strong>]]> With black soil (Pachic Udic Argiboroll) of Northeastern China as the test object, an incubation test was conducted to investigate the effects of urease inhibitors, hydroquinone (HQ), phenyl phosphorodiamidate (PPD) and N-(n-Butyl) thiophosphoric triamide (NBPT), on the kinetic characteristics of soil urease under normal moisture and waterlogged conditions, aimed to study the changes of catalytic potential of soil urease and the inhibition mechanisms. The results showed that test urease exhibited typical Michaelis-Menten kinetic behaviors, and all test inhibitors increased the Km and decreased the Vmax of soil urease, behaving as mixed inhibitors to soil urease. Under both normal and waterlogged conditions, compared with HQ, PPD and NBPT made Km increase and Vmax and Vmax and Vmax/Km decrease more greatly, and the duration of these effects was longer (ca. 30 days vs. 10 days). Under water-logging, PPD made more increment of Km and more decrement of Vmax and Vmax/Km than NBPT, compared with that under normal soil moisture condition, suggesting that NBPT was more available under normal soil moisture condition, while PPD was promising under water-logging condition. To apply urease inhibitors and to control soil moisture condition could be a feasible way in increasing fertilizer N use efficiency affected by soil urease. <![CDATA[<strong>THE IMPACT OF USING LEAFCUTTING BEES<i> (Megachilidae hymenoptera) </i>WITH DIFFERENT FERTILIZATION TREATMENTS ON ALFALFA SEED PRODUCTION</strong>]]> Alfalfa, Medicago sativa (L, 1753), one of the most important forage crops in the world; leafcutting bees which belong to Family Megachilidae are very promising pollinator of Alfalfa is USA and Canada. Different lefacutting natural nests were discovered in Ismailia (east part of Egypt). Artificial polystyrene foam nests were used for bees nesting; it is easy to manage and handle it in alfalfa fields. Different fertilization treatments were carried out for testing their impact on alfalfa seed production in the presence of artificial nests. The seed production depends basically on the pollination of leafcutting bees (tripping mechanism) more than fertilization treatment; we found no significant differences between different fertilization treatments. It is highly recommended to use phosphorus and potassium fertilizers during the blooming season synchronized with leafcutting bees. <![CDATA[<strong>BENTAZON-MCPA EFFECT ON <i>Fusarium oxysporum </i>ROOT ROT ON <i>Trifolium pratense </i>IN GREENHOUSE CONDITIONS</strong>]]> In Chile, the main factor in red clover {Trifolium pretense L.) stand decline is fusarium-root rot, which results in a reduction in yield. Fusarium oxysporum (Schlect.) is the most prevalent pathogen recovered from diseased red clover roots plants. Agronomical management of red clover includes application of broadleaf herbicides such as MCPA and bentazon. This study was conducted to evaluate the effects of bentazon and bentazon/MCPA mixture on phytotoxicity and root rot as caused by F. oxysporum on red clover, under greenhouse conditions. In addition, in vitro mycelial growth and conidial germination of F. oxysporum was studied. A reduction of 40% in crown diameter and 57% shoot dry weight was observed 30 days after treatment with a high rate of bentazon/MCPA and F. oxysporum inoculum. The bentazon - F. oxysporum interaction reduced root dry weight by 57% at IX rate and 42% with 2X rate at 20 and 30 of evaluation. Bentazon caused a significant increase in phytotoxicity at the high rate and the mixture bentazon/MCPA increased root rot severity and phytotoxicity at the high rate. The conidial germination and mycelial growth were significantly reduced by bentazon/MCPA. These results suggest that red clover growth and persistence could be adversely affected by F. oxysporum after bentazon and bentazon/MCPA application.