Volumen 17, Número 2 (Diciembre, 1999)
Uso de distintas plantas de referencia en la estimación de la fijación de nitrógeno en alfalfa por el método de dilución isotópica
Use of different reference plants on the estimation of nitrogen fixation in alfalfa by the isotopic dilution technique
G Sierra, A Lazzari & M Gomez
Pág. 1-8
We investigated the effect of using different reference plants (Dactylis glomerata L., Lolium perenne L. and Eragrostis curvula L.) to quantify the proportion of nitrogen in alfalfa derived from biologi- cal N2 fixation (%NDDA) by the isotope dilution technique, using soil with ammonium sulfate at 9,811 atom % 15N excess provided in split applications. The soil used was a Typic Haplustoll, pH 6.5. Plants were grown in a pot experiment and five harvests were achieved. We have compared the partitioning of fixed N2 among herbage and roots of alfalfa at the last harvest. The %NDDA as- sessed by the different reference plants avereged 70 % at the first harvest. During the second and third harvest intervals, alfalfa derived 80 % of its N from fixation, and then declined in the fourth and fifth harvests, with Dactylis glomerata and Lolium perenne as reference plant. Eragrostis curvula presented lower estimates of %NDDA in the second, third and fourth harvests. During the tudyperiod, the total amount o fN fixed averaged 114mg Nplant-1.In the last harvest the herbage
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Nutrición nitrogenada del trigo bajo siembra directa y labranza convencional
Spring wheat nitrogen nutrition under conventional and no tillage
JL Falotico, GA Studdert & HE Echeverría
Pág. 9-20
No-till (SD) spring wheat (Triticum aestivum L) in the southeastern Buenos Aires Province has become very important in the last years. This tillage system cause different soil-plant-environment relationships than those associated to conventional tillage (LC). Our objective was to evaluate the behavior of spring wheat under SD and LC at Balcarce, Argentina (37° 45’ S; 58° 18’ W) on a soil that had been under continuous cropping for 20 yr and under SD for only 3 yr. The experiment was carried out during the 1996/97 growing season with a randomized complete block experimental design and a split-plot treatment arrangement. Tillage system (SD and LC) was assigned to the main plots and nitrogen rate (0, 60, 120, and 180 kg N ha-1) was assigned to the sub-plots. There were no statistical differences in NO3-N and soil water contents between tillage systems, although NO3-N was higher under LC and water content, was higher under SD. Mechanical impedance was also higher under SD and could have affected initial crop growth. Light interception, aboveground biomass and total nitrogen accumulated were higher under LC, but differences were reduced when nitrogen fertilizer was applied. Stem NO3-N and leaf chlorophyll contents indicated greater nitro- gen deficiency under SD. Grain yield was relatively low for both tillage systems and the yield obtained under SD was 92% of that under LC. Besides, grain protein content was also higher under LC. These results were attributed to the lower soil nitrogen supply ability under SD confirmed by a lower estimated mineralized nitrogen along the crop growing season. Nitrogen fertilization dimin- ished differences in crop growing and yield between tillage systems.
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Aplicación de distintas dosis de yeso a un Natracuol de la Pampa Deprimida
Gypsum application to a Natraquoll of the argentine flooding Pampas
JL Costa & P Lodz
Pág. 21-27
Sodic soils produce a poor soil-water-air relationship, which affects plant growth and makes tillage difficult in both humid and dry environments. Gypsum is the calcium source most widely used in sodic soils reclamation. The application of gypsum to a Natraquoll (Guido series, fine, illitic ther- mic) under pasture was evaluated in the humid Flooding Pamas of Argentina in a field experiment carried out with a complete randomized block design. Treatments included gypsum application of 0, 15, 35, and 60 Mg ha-1. Gypsum applications of 35 and 60 Tn ha-1 reduced significantly the sodium content in the underlying horizons, where the gypsum was not mixed with the soil. Depth of soil reclamation was higher with higher gypsum applications. Dry matter yields were higher in all gypsum treatments than in the control. This results, associated with a better pasture implantation, makes of gypsum application a possible practice for sodic soil in the flooding Pampas. The use of this technology by farmers will mainly depend on gypsum costs, which are directly linked to the existence of natural sources of gypsum near the application place.
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Influencia de la adición de diversas especies de algas sobre algunas propiedades químicas de un suelo ácido y el crecimiento de Hordeum vulgare l.
Effect of various algal species on some chemical properties of an acid soil and Hordeum vulgare l. production
MJ Montero Vilariño, P Marcet Miramontes, ML Andrade Couce & J Estevez Sio
Pág. 28-38
The effect of twelve algal species on some soil properties and Hordeum vulgare L. production was studied. Results showed that almost all species had nitrogen contents higher than 1%, and high P, Ca, Mg, K, and Na concentrations Ulva rígida Agardh was the specie with the highest Mn and Zn concentration and Desmarestia aculeata (Lightfoot) Lamour of Fe. Acidity and exchangeable Al decreased after seaweed addition. Most of the studied species, and specially Gymnogongrus norvegicus (Gunner) Agardh, increased the contents of exchangeable cations and the effective cat- ionic exchange capacity.as well as the contents of available Fe, Mn, and Zn.. Barley dry weight production after soil treatment with all algal species was higher than in the control.
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Temperatura y contenido hídrico del suelo en superficie durante el cultivo de trigo bajo dos sistemas de labranza
Surface soil temperature and water content during wheat crop under two tillage systems
LA Ferreras, JL Costa & FO García
Pág. 39-45
Soils under different tillage systems have a distinctive behavior as refered to water retention and thermal regimen and these factors may have influence on crop development. This experiment was carried out on two Petrocalcic Palleudolls in southern Buenos Aires province. Two tillage systems, direct drilling (SD) and conventional tillage (LC) were studied in a wheat crop (Triticum aestivum, L.). Soil temperature at a depth of 3-8 cm occurred at 9 am and the daily maximum, were measured at different crop growth stages. Simultaneously to temperature records, soil water content was gravimetrically determined. Conventional tillage showed lower records of temperature measured at 9 am with respect to SD for the first stages of wheat crop, while SD had the lower records for maximum temperatures. There was a direct relationship between global radiation and soil maxi- mum temperature (R2 =0.61) being LC which presented the higher values (P≤0,05). For the 9 am records it was determined that at a lower temperature, differences between treatments were higher having LC the lowest values (R2 = 0.62, P≤0,05). There was a higher water content in the topsoil in SD during the first stage of the crop. The smallest daily thermal amplitude in SD may be due to higher soil water content and to the presence of surface stubble.
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Movimiento superficial de fósforo en suelos de Pampa Ondulada
Superficial movement of phosphorus in soils from the Rolling Pampas
CI Chagas, RS Lavado, CA Revilla & GJ Macias
Pág. 46-53
There is a lack of local information on overland movement of phosphorus fractions associated with the effects of rainfall and/or irrigation. The aim of the present investigation was to quantify the particulated and dissolved fractions generated and transported by drop impacts and runoff. Simu- lated high energy rainfall was applied to microplots containing disturbed and fertilized bare top- soils from a Arroyo Dulce Series silty loam Typic Argiudoll. Treatments were a soil under continu- ous agriculture (plowed) and a soil devoted to pasture (unplowed). The organic carbon content was significantly lower in the plowed soil whereas the extractable phosphorus content and the soil texture were similar in both treatments. Soil organic carbon content influenced the dynamics of the dissolved and particulated fractions of phosphorus in the runoff. The unplowed soil showed a high initial concentration of reactive dissolved phosphorus followed by a considerable declination of this concentration during rainfall application. This behaviour differed from the plowed treatment and consequently it led to differences in the fit of linear regression models between treatments. The plowed soil delivered more extractable particulated phosphorus to runoff than the unplowed soil. This was related to differences in sediment quantity rather than quality. Organic carbon and clay but not extractable particulated phosphorus, were enriched in runoff sediments compared to source soil . Some of these results differed from those that were obtained abroad employing low energy simulated rainfall.
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Fósforo retenido por suelos y por sus fracciones granulométricas en relación con la materia orgánica
Phosphorus retention by soils and by their granulometric fractions in relation with the organic matter
S G de Bussetti, E A Ferreiro, I M Natale, M E Mandolesi
Pág. 54-57
The effect of organic matter (OM) on release of surface OH− (OHsup) and P retention on samples from surface and subsurface horizons of seven soils and their granulometric fractions were studied. The soils were located in the southwest of Buenos Aires province (Argentina). The study also included samples with organic matter elimination by ignition. The amount of OHsup and the P retention was inversely dependent on particle size. Ignition produced an increase in OHsup and P retention for soil samples and for their granulometric fractions. No significant differences were found between horizons in OHsup and P retention. The increase in OHsup was significantly correlated (P less than 0,01) to increase in P retention after ignition. It is concluded that OM blocks the active reten- tion sites of P.
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Erosividad de las precipitaciones en Tandil, Provincia de Buenos Aires
Erosivity of precipitations in Tandil, Province of Buenos Aires
CM Di Leo, A Aragón, R Marlats & JE Bruno
Pág. 58-61
The objective of this paper was to evaluate the utility of a short period pluviografic data for the estimation of the monthly and annual erosivity in Dique Seco, Tandil, Buenos Aires, Argentina. The methodology used by the Universal Soil Loss Equation (USLE) for calculation of the R factor was applied to a 1972-1977 serie, and the results compared with other published data. A close relationship between the product of the total volume of a storm by the maximum intensity in 30 minutes and the R factor was confirmed. The coefficients of adjustment Bi was applied. A higher rain erosivity was confirmed for the spring and summer months.
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Efectos de la ubicación de un fertilizante nitrógeno-fosfatado sobre la nodulación y la producción de soja en siembra directa en la región de la pampa arenosa, Argentina
Effect of the placement of N-P fertilizer for soybean nodulation and grain production in no-tillage systems in the sandy pampas region, Argentina
M Díaz-Zorita, G Grosso, MV Fernández-Canigia & G Duarte
Pág. 62-65
No-till (NT) soybean production is an important practice in the sandy Pampas region (Argentina). Soybean crops have high nutritional requirements but few research has been conducted on soybean N-P fertilization for NT systems. Our objective was to evaluate the effects on soybean nodulation and yields, of N-P fertilizer pre-plant placements in a non-P deficient sandy Typic Haplustoll. The soybean crop followed corn in a continuous NT system since 1993. Five fertilization treatments with diammonic phosphate (FDA) were applied before seeding: 0, 50 and 100 kg ha-1 of FDA broadcasted and banded (0.05 m below the seeding line). The aerial dry matter, total P and N in top trifoliate leaves and nodulation were evaluated in the full-bloom stage. Grain yields were deter- mined at physiological maturity. Fertilizer placement x FDA rate interaction was not significant for any measured parameter. The nodules’ number and weight increased when the FDA rate increased. No differences in nodulation were observed between the fertilizers placement treatments. In this conditions there are not differences in soybean production between banded or broadcast fertilizer placement.
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