Abstract:

In the Southeastern region of Buenos Aires province, soybean monoculture has led to a decline in soil organic matter (SOM) levels in soil, mostly the labile fractions. The reduction of SOM has a negative impact on the soil environment. Cover crops (CC) constitute an alternative to maintain or improve SOM levels. The aim of this study was to determine the effect of oat as CC on (a) the SOM dynamics and (b) the availability of macro- and micronutrients in a representative soil of the Southeastern region of Buenos Aires province. Total organic carbon (TOC) and nitrogen (TON), as well as their labile and mineral-associated fractions, and macro- and micronutrient availability were determined. The treatments were soybean monoculture with and without oat as cover crop. The increases in SOC and TON were 22.7% and 11%, respectively, when CC was included to the soybean monoculture. These increases were observed mostly in the labile fractions, with increases of 61.3 and 38.7% for the particulate coarse organic carbon (PCOf) and particulate fine organic carbon (PCOf), respectively, and 79.2% for the particulate coarse organic nitrogen (NOPg). Regarding the nutrients, an increase of 47.6% was observed in manganese (Mn) in the first 5 cm of soil depth, and a decrease in phosphorous (P) availability in the same soil layer due to its consumption and retention by CC. It can be conclude that CC presented a surface soil effect on the dynamic of SOM, increasing C, N, and available Mn contents, but decreasing soil P availability.

Instituto de Suelos

Author affiliation: Beltran, Marcelo Javier. INTA. Instituto de Suelos; Argentina

Author affiliation: Sainz Rozas, Hernan Rene. INTA. Estación Experimental Agropecuaria Balcarce; Argentina

Author affiliation: Galantini, Juan Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina

Author affiliation: Romaniuk, Romina Ingrid. INTA. Instituto de Suelos; Argentina

Author affiliation: Barbieri, Pablo. INTA. Estación Experimental Agropecuaria Balcarce; Argentina

Abstract:

La mayor participación de la soja entre los cultivos de verano sumada a los largos períodos de barbecho otoño-invernales han dado como resultado una importante reducción en el aporte de residuos y consecuentemente del contenido de materia orgánica edáfica y nutrientes asociados. La intensificación de la secuencia de cultivos a través de la incorporación de cultivos de cobertura (CC) invernales surge como una estrategia sustentable para generar un mayor y más eficiente uso de los recursos. El objetivo del presente trabajo fue evaluar el efecto a corto plazo de la inclusión de trigo y vicia como cultivos de cobertura antecesores a cultivos de maíz y soja, sobre la disponibilidad de macro y micronutrientes, y sobre las distintas fracciones de la materia orgánica y nutrientes asociados en un Argiudol típico. Se trabajó sobre un ensayo en bloques completamente aleatorizados en la localidad de San Antonio de Areco, provincia de Buenos Aires. Los tratamientos fueron: barbecho/soja, CC trigo/soja, CC vicia/soja, y barbecho/maíz, barbecho/maíz fertilizado, CC trigo/maíz, CC trigo/maíz fertilizado, CC vicia/maíz, CC vicia/maíz fertilizado. A la cosecha de los cultivos de grano se realizaron determinaciones de carbono, fósforo y nitrógeno orgánico particulado, macronutrientes (N, P, Ca, Mg y K) y micronutrientes (Zn, Mn, Fe, Cu) disponibles en los primeros 5 cm de suelo. La utilización de CC incrementó en el corto plazo (un ciclo de cultivo) el carbono, nitrógeno y fósforo de la materia orgánica particulada gruesa del suelo (105 a 2000 μm). Estos incrementos fueron en general mayores cuando se utilizó vicia como CC. Las concentraciones de micronutrientes (Zn, Mn, Cu y Fe) en suelo a la cosecha del cultivo de soja fueron mayores en los tratamientos con CC respecto al testigo. Bajo cultivo de maíz, ambos CC incrementaron las concentraciones de Mg y K en el suelo respecto al barbecho, mientras que el tratamiento con vicia presentó las mayores concentraciones Mn y Fe respecto del trigo (p<0.05). Estos resultados muestran el efecto positivo en el corto plazo de la inclusión de CC, no solo sobre los incrementos en el carbono lábil y los nutrientes asociados (N y P), sino también sobre la disponibilidad de los micronutrientes en el suelo.

The use of soybean as the main summer crop followed by the long fall-winter fallow periods, have resulted in a significant reduction of residues contribution and consequently, in the edaphic organic matter and associated nutrients. The intensification of the crop sequence by winter cover crops (CC) inclusion emerges as a sustainable strategy to generate a more efficient use of the resources. The aim of this research was to evaluate the short-term effect of the inclusion of wheat and vetch as cover crops predecessor to maize and soybean crops, on the availability of macro and micronutrients, and on the different organic matter fractions and associated nutrients in a Tipic Argiudoll. The study was carried out in San Antonio de Areco, Buenos Aires province, and consist in a completely randomized block design. The treatments were: fallow / soybean, wheat CC / soybean, vetch CC/ soybean, and fallow / maize, fallow / fertilized maize, wheat CC/ maize, wheat CC / fertilized maize, vetch CC / maize, vetch CC/ maize fertilized. Measurements of available macro (Ca, Mg and K) and micronutrients (Zn, Mn, Fe, Cu) and carbon, phosphorus and nitrogen in different soil fraction were determined in the first 5 cm depth after harvest of the main crops. The inclusion of CC increased the organic carbon, nitrogen and phosphorus in the most labile soil fraction (coarse fraction) in the short term (one crop cycle). These increases were generally higher when vetch was used as CC. After soybean harvest, soil micronutrients concentration (Zn, Mn, Cu and Fe) were higher in the treatments with CC compared to the control. Under maize, both CC increased soil Mg, K in compared to fallow, while the Vetch treatment presented higher Mn and Fe concentrations than the wheat treatment (p <0.05). These results show the positive effect in the short term of the inclusion of CC, not only on the increases in labile carbon and associated nutrients (N and P), but also on the availability of micronutrients in soil.

Instituto de Suelos

Author affiliation: Romaniuk, Romina Ingrid. INTA. Instituto de Suelos; Argentina

Author affiliation: Navarro Padilla, Ricardo. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Conservación y Manejo de Suelos; Argentina

Author affiliation: Beltran, Marcelo Javier. INTA. Instituto de Suelos; Argentina

Author affiliation: Eiza, Maximiliano Joaquin. INTA. Instituto de Suelos; Argentina

Author affiliation: Castiglioni, Mario Guillermo. Universidad de Buenos Aires. Facultad de Agronomía. Cátedra de Conservación y Manejo de Suelos; Argentina

Author affiliation: Mousegne, Fernando Jorge. INTA. Estación Experimental Agropecuaria Pergamino. Agencia De Extensión Rural San Antonio de Areco; Argentina

Abstract:

Soils under no tillage have experienced unfavorable changes, mainly due to current agricultural practices that consist in monocultures that leave little residue cover. The inclusion of grass as cover crops during the winter season could be a sustainable strategy to increase crop intensification in sequences where soybean predominates, helping to maintain soil fertility, organic matter levels and enhance soil physical properties. The aim of this research was to evaluate the effects of 8 years of sustainable crop intensification (by increasing the proportion of cereals in crop rotations) on soil organic carbon, macro- and micronutrients associated with granulometric fractions of different lability in a Typic Argiudoll of the Rolling Pampa, Argentina. The experiment included two crop sequences commonly used in this area: soybean-soybean (S-S) and maize-soybean-wheat/soybean (M-S-W/S) combined with the inclusion of wheat (Triticum aestivum L.) as cover crop (CC) in winter. The intensification sequence indices (ISI) were 0.39, 0.69, 0.55 and 0.64 for S-S, S-CC-S, M-S-W/S and M-CC-S-W/S, respectively. The carbon measured in the coarse particulate fraction (Pcf) in the 0–5 cm soil depth was 3 times larger in S-CC-S than in S-S. Cropping intensity also modified N, S, P, Ca and Mn in the Pcf with no changes in Mg, K, Zn, Fe and Cu contents. Among the carbon fractions studied, only the carbon measured in the Pcf and the easy mineralizable carbon estimated by the soil respiration in the first soil layer (0–5 cm), were positively correlated with the ISI. In the present study, 8 years under sustainable crop intensification were sufficient to show changes in the mineral associated fraction (Maf). Increases in the C in the Maf in maize legume-based rotation, suggest SOC accumulation in more stable carbon pools.

Instituto de Suelos

Author affiliation: Romaniuk, Romina Ingrid. INTA. Instituto de Suelos; Argentina

Author affiliation: Beltran, Marcelo Javier. INTA. Instituto de Suelos; Argentina

Author affiliation: Brutti, Lucrecia Noemi. INTA. Instituto de Suelos; Argentina

Author affiliation: Costantini, Alejandro Oscar. INTA. Instituto de Suelos; Argentina. Universidad de Buenos Aires. Facultad de Agronomía, Cátedra de Edafología; Argentina

Author affiliation: Bacigaluppo, Silvina. INTA. Estación Experimental Agropecuaria Oliveros; Argentina

Author affiliation: Sainz Rozas, Hernan Rene. INTA. Estación Experimental Agropecuaria Balcarce; Argentina

Author affiliation: Salvagiotti, Fernando. INTA. Estación Experimental Agropecuaria Oliveros; Argentina