Soil cover under no till systems in Southwestern Buenos Aires Province

Abstract

No tillage (NT) is generally associated with high levels of crop residues on soil surface, which has positive effects on physical and chemical fertility, soil biology and erosion control. However, the absence of soil cover may have a worse effect on soil quality in the long term than conventional tillage. In this study we determined the presence of surface residues and soil cover in fields for winter crops in the years 2011, 2012 and 2013.The study area included the southwest of Buenos Aires province (SOB), Argentina, where over 120 fields under NT were sampled. Our objectives were: i) to establish a simple methodology for surface residues sampling; ii) to determine the current status of surface residues and soil cover in cropped fields under NT in the SOB; iii) to establish the relationship between amount of surface residues and soil cover for the predominant crops of the SOB.A large proportion of fields in the subhumid-semiarid region of SOB had lower soil cover than the required by the literature to be considered conservation agriculture, which would provide adequate protection against erosion. In the studied area, most of winter crops (56%) left adequate soil cover while, in average, summer crops did not leave the minimum of 30% soil cover. The analyzed data show the difficulty in the region for the production of dry matter and its permanence as soil cover, even in agricultural fields with continuous no-tillage.

López F.M., M.E. Duval, J.M. Martínez, J.A. Galantini. 2015. Cobertura en el Sudoeste Bonaerense en suelos bajo siembra directa. Ciencia del Suelo 32 (2) 273-281.

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Use of cover crops in soybean monoculture: effects on water and carbon balance

Abstract

The cover crops (CC) is a good alternative to improve the lack of coverage and carbon balance in soils under no tillage with soybean (Glycine max L. Merr.) monoculture, predominant in the Pampean Region. In this study (2006-2011) the effect of winter cover crops -wheat (T), oats (A), vetch (V) and oats+vetch (A+V)- on water consumption, dry matter production and its impact on the of soil organic carbon contents (TOC) was evaluated. Biomass production of the CC was closely related to rainfall recorded between the months of June and October. In general, T and A treatments contributed greater amount of soil cover, on average, these grasses biomass were 24 and 91% higher compared with A+V and V. The water cost of including CC was 13-93 mm compared to traditional fallow (Ct). At the time of sowing of soybean, in general, Ct presented the highest water content. However, this treatment showed a loss of moisture by evaporation without biomass production, which is used by the CC to fix carbon between 18 and 303 kg C ha^-1 depending on the year conditions. The use of CC -T, A and A+V- increased the TOC at 0-20 cm depth at rates of 597 to 98 kg C ha^-1yr^-1, while it decreased at 824 and 289 kg C ha^-1 yr^-1 without CC or using legumes (V), respectively. For conservation or increase the TOC, use of CC such as A, A+V and T would be a feasible option given that exceeds the minimum source C input of4,5 Mg C ha^-1 necessary to maintain the TOC in soils south of Santa Fe.

Key words: Argiudoll; winter cover crops; available water; organic carbon

Duval M.E., J.E. Capurro, J.A. Galantini, J.M. Andriani. 2015. Utilización de cultivos de cobertura en monocultivo de soja: Efectos sobre el balance de carbono. Ciencia del Suelo 32 (2) 247-261.

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Foliar nitrogen fertilization of wheat in the Southwestern Pampas

Abstract

In the semiarid and subhumid Pampean region, foliar nitrogen (N) application to wheat at anthesis stage coincides with an erratic rainfall period, which defines yield and quality. The objectives of the study were to evaluate the effect of foliar N application at anthesis on wheat grain yield and quality in the Southwestern of Buenos Aires Province, an area characterized by variations in climate and soil fertility, and to apply the principal component analysis (ACP) in all variables. A total of 30 experiments were conducted from 2004 to 2012 in the Southwestern. Nitrogen rates of 0, 25, 50 and 100 kg N ha^-1 were applied at sowing and 25 kg ha^-1 at anthesis. Water availability to the crop was variable in the study period, which caused significant yield variations. The ANOVA for all the experiments, showed no significant differences for N at sowing or at anthesis, but it indicated a protein increase in 25 of the 30 experiments. In all trials yield from the control treatment ranged from 1784 to 2600 kg ha^-1 and N foliar application response from 145 to 1273 kg ha^-1. The grain protein content, which averaged 132 g kg^-1, increased 11% with N fertilization at anthesis. Low and poorly distributed rainfall limited yield and foliar N response. Nitrogen rates at sowing that produced the maximum response to foliar application ranged from 0 to 100 kg N ha^-1. The most influential variables in ACP were the rainfall of September, October and November, dry matter at Z60,soil water content at sowing and N availability. The yield was estimated with 72% confidence and protein with 59%. In these environments, foliar N application resulted in variable grain yield buy it proved to be a useful practice for enhancing protein content. 

Landriscini M.R., J.M. Martínez, J.A. Galantini. 2015. Fertilización foliar en trigo en el sudoeste bonaerense. Ciencia del Suelo 32 (2) 183-196. ISSN 0326-3169 (versión impresa)  ISSN 1850-2067 (versión electrónica)

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Evaluation of the physical quality of soils in the pampas region: effect of management practices

Abstract

The adoption of no tillage (SD) has increased worldwide in recent decades and particularly in Argentina, although sometimes doubts have been raised about its effect on soil physical properties. The objective of this work was to evaluate changes due to management systems on some soil parameters associated with porosity and water storage. They were compared to those proposed as "ideal" or "critical", according to the literature, and with reference levels obtained under pristine conditions. The study sites are located in Bengolea, Monte Buey, Pergamino and Viale. At each site, two agricultural situations with different intensities of management (Good Practices and Poor Practices), and a natural situation (Natural Environment) were evaluated. Bulk density, total porosity, volume of different pore sizes (macropores, mesopores and micropores), and total organic carbon and its fractions were determined in soil samples (0-10 cm). The lower levels of total organic carbon due to agricultural practices caused a decrease in total porosity, mainly reflected by the lower volume of macropores, which decreased up to 23%. Agricultural use resulted in soil compaction, although not critical, due to a decrease of the macropores. Bulk density values were within the optimal range, although problems of compaction can occur when the values of index of structural stability are below 6.13. Total organic carbon and the index of structural stability were the only variables with values lower than optimal in agricultural soils, allowing to differentiate, at some sites, between good and poor practices.

Duval M.E., J.A. Galantini, J.M. Martínez. F.M. López, L.G. Wall. 2015. Evaluación de la calidad física de los suelos de la región pampeana: efecto de las prácticas de manejo. Ciencias Agronómicas RIFCA-UNR 25: 33-43.         ISSN Impreso: 1853-4333  ISSN On-Line: 2250-8872

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Nitrogen use efficiency for wheat in semiarid region of Buenos Aires (Argentina): effects of the dose and timing application

Abstract

In semiarid regions optimal fertilization is difficult due to erratic rainfall. The aim of this study was to analyze the influence of climate variability on the response to different rates and timing of fertilization on wheat productivity and on efficiencies in the use of nitrogen in a site of the semiarid region of the province of Buenos Aires, Argentina. For five years, fertilization trials were conducted in wheat combining N rates (0, 25, 50 y 100 kg ha^-1) and times of fertilization: Seeding (Ns) and tillering (Nm). Agronomic efficiency (EUF) for dry matter (MS) and grain, and apparent recovery of nitrogen (RAN) were evaluated. Interactions between variables (year, rates and times) and efficiencies were found. In Nm, significant correlations of all parameters were found with October rainfall. Protein for Ns and Nm was significantly and inversely correlated with full cycle rainfall. Significant correlations were found in EUF of MS and grain in this order; Full cycle rainfall> Spring rainfall> Oct rainfall> Set rainfall. Interannual climate variability showed the greatest influence on the nitrogen use efficiencies, regardless the application timing.

Key words Fertilization timing; tillering application; erratic rainfalls

Martínez J.M., J.A. Galantini, M.R. Landriscini. 2015. Eficiencia en el uso del nitrógeno del trigo en la región semiárida de la provincia de Buenos Aires (Argentina): efectos del momento de aplicación. Agriscientia 32 (1) 15-27.

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Assessing nitrogen requirements of wheat crops with a chlorophyll meter in the Southwestern Pampas

Abstract

A chlorophyll meter is a promising tool for monitoring the status of N through the green index (IV). The hypothesis was that estimates from the use of a chlorophyll meter would be more closely linked to the N harvested from dry matter than to wheat (Triticum aestivum L.) grain yield, which is affected by climate variability. The objective was i) to determine IV sensitivity to predict total dry matter (MST) and grain yield, protein content and N-uptake, and ii) to evaluate N-availability at planting to establish reference plots without N deficiencies by using a chlorophyll meter at different stages of wheat cultivation and comparing field tests with a pot experiment. In 2010, a nitrogen fertilization trial was conducted in pots, while in 2011 and 2012 the trials were conducted on two sites in SOB under no-tillage. In two (Z22 y Z40) and three (Z22, Z40 y Z70) stages of the crop, chlorophyll meter readings were taken for the field and pot trials, respectively. The field prediction of MST and grain yield , protein content and N uptake with chlorophyll meter readings showed significant regressions with low settings (R² = 0.11 to 0.29). In the pot experiment, the prediction of N-uptake for the three sampled stages increased, without differences in slopes and with a high setting (R²=0.79). The chlorophyll meter would be a promising indicator of N-uptake by the crop; in sub-humid regions, however, it would not be an accurate tool to predict grain yield or protein content in wheat crops. Also, a chlorophyll meter would be useful to estimate the available N needed by the wheat crop and to determine the nutritional status of the plant.

Key words Green index; ACA 303; Sub-humid Region

Martínez J.M., J.A. Galantini, M.R. Landriscini. 2015. Diagnóstico de fertilidad nitrogenada en trigo con la utilización de un clorofilómetro en el Sudoeste Bonaerense. Ciencia del Suelo 33(1) 31-43.

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