Tuesday, May 17, 2016

Texture influence on soil phosphorus content and distribution in semiarid Pampean grasslands

Suñer L., J.A. Galantini. 2015. Texture influence on soil phosphorus content and distribution in semiarid Pampean grasslands. InternationalJournal of Plant & Soil Science (ISSN: 2320-7035) Vol.: 7, Issue.: 2 109-120, no.IJPSS.2015.136, PDF

Extended Abstract
Soil texture affects the soil environment and the mineralization of soil organic matter (SOM) in several ways. It has been reported that a rich clay content in the topsoil results in high levels of soil organic matter; at the same time, it enhances nitrogen, phosphorus and sulphur availability (Galantini et al., 2004; Duval et al., 2016). Soil P (phosphorus) equilibrium and availability can be modified by soil texture as a consequence of changes in physicochemical properties, in phosphate adsorption-desorption-diffusion processes, and in SOM mineralization-immobilization processes.
Physical fractionation methods based on SOM particle size have been developed to separate organic fractions with different characteristics and dynamics (Andriulo et al., 1990; Galantini et al., 1997). It is therefore now possible to distinguish between SOM associated with the fine and with the coarse fractions, which have different structures and roles. The fine soil fraction (clay, silt) corresponds to a more humidified or mineral-associated organic matter (MOM), and the coarse fraction (different sizes of sand) to less transformed, labile, light or particulate organic matter (POM). Considering that both fractions are crucial to soil fertility, it is important to determine the organic (Po) and inorganic (Pi) phosphorus contents in each size fraction and to relate them to soil texture. Differences in P content are expected to be found in both particle size fractions: the fine fraction is likely to contain the more stable Po (Po-MOM) and the more available Pi (Pi-clay and silt sizes); the coarse fraction, instead, is assumed to contain the more labile Po (Po-POM) and Pi (Pi-sand size) with low availability in the short term.
The hypothesis is that soil texture affects the equilibrium of the different P-forms in soils of the semiarid Pampas region, mainly through stabilization in the resistant organic forms of fine-textured soils and accumulation in the labile organic forms of sandy soils. The aim of the study is to determine the content and distribution of the main P-forms in texturally different soils and to relate them to the available P-index.
Soil samples (0-0.15 m) were collected from 27 sites with different textures in a 25-year-old pasture located in the Experimental Station of Bordenave, Argentina (63°01’20”W; 37°51’55”S). Soil particle size fractions were obtained through wet sieving by separating the fine (0-100 µm) and coarse (100-2000 µm) fractions. Soil organic matter was determined in both fractions, and thus mineral-associated (MOM) and particulate organic matter (POM) were obtained, respectively. Extractable (Pe), organic (Po), inorganic (Pi) and total extractable (Pt) phosphorus were determined. Occluded P (Pocl) was calculated as the difference of [Pt - (Po+Pi)] applied to the whole soil and the particle fractions.
In these soils, texture determines P content and the equilibrium of its different forms. Available P-forms (estimated by Pe) were related to the inorganic form present in the fine fraction of the soil. Phosphorus content in its different forms was closely associated with soil fractions. The level of Po was higher in the coarse fraction of the soils containing more fine fractions. All the studied P-forms were higher in fine-textured soils than in coarse ones. However, P-forms in particle size fractions showed different tendencies. In coarse-textured soils, Po in MOM was lower than in fine-textured ones, whereas P-content was higher in MOM and lower in POM compared with fine-textured soils (Rosell et al., 2000).
Based on these results as well as previous ones, we propose a conceptual model to identify P changes in soils of different textures (Galantini et al.2005, 2007; Rosell et al., 2000; Suñer & Galantini, 2012; Suñer et al., 1998, 2002, 2013, 2014; Zalba & Galantini, 2007).
Soil organic fractions and their P-content within the sand fraction are inside the labile pool, whereas those within the silt and clay fractions are inside the intermediate and passive pools. Inorganic minerals of the coarse fraction can be considered a passive pool of P, while P in the fine fraction represents an active pool. According to this finding, a conceptual model can be proposed where P could be linked to SOM fractionation schemes. The principal flows in this model are a) weathering and physico-chemical processes, which reduce the size of coarse minerals until mineral particles reach a size below 50 µm and are then included in the fine fraction; b) humification, by which organic inputs are transformed into more complex molecules with a lower size; c) mineralization of SOM fractions, which produce nutrient release and make P available for plants; d) physico-chemical equilibrium, e) P-uptake by plants; f) recycled P, by which crop residue returned to the soil can improve Po by a POM increase.
Andriulo A., J.A. Galantini, C. Pecorari, E. Torioni. 1990. Materia orgánica del suelo en la región pampeana. I. Un método de fraccionamiento por tamizado. Agrochimica (Italia) XXXIV (5-6) 475-489.
Duval M.E., J.A. Galantini, J.M. Martinez, F.M. López, L. Wall. 2016. Sensitivity of different soil quality indicators to assess sustainable land management: Influence of site features and seasonality. Soil & Tillage Research 159: 9-22.
Galantini J.A., R.A. Rosell. 1997. Organic fractions, N, P, and S changes in a semiarid Haplustoll of Argentine under different crop sequences. Soil & Tillage Research 42: 221-228. ISSN: 0167-1987  ELSEVIER
Galantini J.A., L. Suñer, H. Krüger. 2005. Dinámica de las formas de P en un Haplustol de la región semiárida pampeana durante 13 años de trigo continuo. Revista Investigaciones Agropecuarias (RIA – INTA) 34 (2): 13-31.
Galantini J.A., L. Suñer, J.O. Iglesias. 2007. Sistemas de labranza en el sudoeste bonaerense: efectos de largo plazo sobre las formas de fósforo en el suelo. Revista Investigaciones Agropecuarias (RIA – INTA) 36 (1): 63-81.
Galantini J.A., N. Senesi, G. Brunetti, R. Rosell. 2004. Influence of texture on the nitrogen and sulphur status and organic matter quality and distribution in semiarid Pampean grassland soils. Geoderma 123: 143-152  PDF
Rosell R.A., J.A. Galantini, L.G. Suñer. 2000. Long-term crop rotation effects on organic carbon, nitrogen and phosphorus in Haplustoll soil fractions. Arid Soil Research and Rehabilitation 14 (4) 309-316.
Suñer L., J.A. Galantini, G. Minoldo. 2014. Soil phosphorus dynamics of wheat-based cropping systems in the semi-arid region of Argentina. Applied and Environmental Soil Science Volume 2014 (2014), 6 págs. Article ID 532807, http://www.hindawi.com/journals/aess/2014/532807/  PDF
Suñer L., J.A. Galantini. 2013. Dinámica de las formas del P en suelos de la región sudoeste pampeana: Estudio de la incubación con fertilizante fosfatado. Ciencia del Suelo 31: 33-44.
Suñer L.G., J.A. Galantini, R.A. Rosell, M.D. Chamadoira. 2002. Cambios en el contenido de las formas de fósforo en suelos de la región semiárida pampeana cultivados con trigo (Triticum aestivum). Rev. Fac. Agron., La Plata 104(2): 105-111.
Suñer L.G., J.A. Galantini, R.A. Rosell. 1998. Comparación de métodos para la determinación de fósforo orgánico de suelos de la Región Semiárida Pampeana Argentina. Información Tecnológica (Chile) 9 (6) 51-54.
Suñer L.G., J.A. Galantini. 2012. Fertilización fosforada en suelos cultivados con trigo de la región pampeana. Ciencia del Suelo 30(1) 57-66.
Zalba P., J.A. Galantini. 2007. Improved soil tests methods for available phosphorus in acid, neutral and alkaline soils. Communications in Soil Science and Plant Analysis 38: 1579-1587.

Wednesday, April 20, 2016

Soil organic matter quality, quantity and distribution under different tillage systems

Galantini, J.A.; M. Duval; J.M. Martinez; V. Mora; R. Baigorri & J.M. García-Mina. 2016. Quality and quantity of organic fractions as affected by soil depth in an argiudoll under till and no-till systems. International Journal of Plant & Soil Science 10 (5) - doi:10.9734/IJPSS/2016/25205

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Sunday, April 17, 2016

Crop rotation and fertilization in Argentine semiarid region: Wheat productivity (quality and yield)

Galantini J.A., J.O. Iglesias, A.M. Miglierina, R.A. Rosell, A. Glave. 1992. Rotación y fertilización en sistemas de producción de la región semiárida argentina. I. Productividad (calidad y rendimiento) del trigo. Rev. Fac. Agronomía (U.B.A.) 13 (1) 67-75. (in Spanish)

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In the semi-arid region of the Buenos Aires province the effect of 12 years of different crop rotations with wheat (Triticum aestivum) on crop productivity was studied. The rotations were: TV, wheat-winter and summer grasses; TI, wheat-winter grasses; TPa wheat-alfalfa (Medicago sativa) pasture; TPc, wheat-mixed pasture. All divided into treatments without (nf) and with (f) fertilizer (N and P every year) application. Wheat-grazing, the typical of the region included rotation. production of total dry matter aerial (MSTA), grain, straw, protein and N content in grain and straw were evaluated. The inclusion of annual grasses into crop rotation produced a initial positive effect on crop performance and increased grain yield, however, grain quality were not modified. Fertilization increased wheat grain yields,  but in TV only quality was improved. Pasture in rotation with grain yield was similar, but the response to fertilization was significant only in TPc. Alfalfa as predecessor improved wheat dry matter quality, however, grain yield was not increased.

Key words: Crop-rotation, wheat productivity, semi-arid region

Saturday, March 5, 2016

Soil cover under no till systems in Southwestern Buenos Aires Province


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

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


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


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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