Cover Crops in the Production System

Changes in soil pH and phosphorus availability during decomposition of cover crop residues

The aim of this study was to determine the effect of winter cover crops (CC) residues on soil pH and phosphorus (P) availability. Three incubation assays were performed in pots using two CC: vetch (V) (Vicia villosa Roth.) and oats (Oa) (Avena sativa L.). Soil samples were taken from ten sites at 0-20 cm depth. The rate of residues were 0 (D0), 10 (D1), 20 (D2), 30 (D3) and 40 (D4) g dry matter kg-1 soil and the soil sampling was after 10, 20, 30, 60, 90 and 120 days of incubation. Soil pH, extractable P (Pe), and soil organic matter (SOM) and its fractions were determined. The pH increase was correlated with the rate applied (D1< D2< D3< D4). No differences were found for pH comparing V and Oa residues with low residue rates. Soil pH changes were dependent from initial pH and SOM fractions in different soils across the incubation period. The multiple regression models showed that the pH changes were dependent on initial pH level and SOM fractions with a high R2 (0.81). Cover crops residues and its quantities produced different changes on pH - especially at the beginning of the incubation- which influenced the P availability.

Vicia villosa, Avena sativa

Vanzolini J.I., J.A. Galantini, J.M. Martínez, L. Suñer. 2017. Changes in soil pH and phosphorus availability during decomposition of cover crop residues. Archives of Agronomy and Soil Science 63 (13) 1864-1874. http://dx.doi.org/10.1080/03650340.2017.1308493

Download   ResearchGate  Journal Web   Google Drive  (in ENGLISH)

Cover Crops in the Production System

Quality of cover crops in Southwest Bonaerense under no tillage systems

No-tillage system with fall/winter cover crop (CC) ensures that large amounts of different types of organic residue are supplied to the soil. The biochemical composition of each residue, especially its C:N ratio and lignin, plays an important role in nitrogen (N) and carbon (C) soil dynamics, as well as the availability of nutrients for the next crop. The objective of this study was to evaluate the quality parameters of CC based on the quantity and quality of the residue contributed. The experiments were carried out on Argiudioles typical of the Coronel Suárez (Pcia. de Bs. As.) Species used as cover crops were: Oats (Avena sativa L.), Hairy vetch (Vicia sativa L. Thell.), Clover persia ‘‘grazing’’ (Trifolium resupinatum L var. ‘‘Lightning’’), Clover Persia ‘‘coverage’’ (Trifolium resupinatum L. var. ‘‘Laser’’). The determinations were: a) Production of forage (Mg MS ha^-1), b) N, c) neutral detergent fiber (NDF) and acid (FDA), nonstructural carbohydrates (CNES), carbon (C%) and Lignin. The aerial biomass of Hairy vetch presented the highest concentrations of N in the dry matter (MS) produced. When the oats were fertilized they were able to increase the contributions of N to the soil present in the aerial biomass of the residue to 50%. The aerial biomass of Hairy vetch presented the highest yields and concentrations of lignin. The different CC presented C:N and LIG:N ratios that were based on the amount of MS produced by the aerial biomass of the crop and its phonological state at the time of drying. The temperature and the moment of evaluation modified quantity and quality of the residues. The parameters evaluated were sensitive to these changes.

Cover crops, cellulose, hemicellulose, lignin.

Sá Pereira E., J.A. Galantini, A. Quiroga. 2017. Calidad de cultivos de cobertura en sistemas de siembra directa del sudoeste bonaerense. Ciencia del Suelo 35(2) 337-350

Download   ResearchGate  Journal Web Google Drive  (in SPANISH)

Cover Crops in the Production System

Decomposition from legume and non-legume crop residues: effects on soil organic carbon fractions under controlled conditions

Cover crop (CC) residues protect the soil from erosion and their permanence on the surface is largely influenced by their biochemical constituents. We performed a study under controlled conditions to investigate the dynamics of legume and non-legume CC residues decomposition and the transformations of the soil labile organic carbon fractions in the surface layer (0-15 cm). The experiment was carried out on a Typic Argiudoll (clay loam, 27.4 g kg⁻¹ soil organic matter, 14 mg kg⁻¹ extractable phosphorus and 6.5 pH) placed in undisturbed pots (1570 cm³) in a greenhouse under controlled conditions of temperature (25 ± 1 °C). We evaluated three CC species (oat, Avena sativa L.; vetch, Vicia sativa L.; Persian clover, Trifolium resupinatum L.) and a no-CC control (fallow). Shoot residues were applied on the soil surface at 5.4, 5.4 and 2.7 g dry matter (equivalent to 6, 6 and 3 Mg ha⁻¹ for oat, vetch and clover, respectively) and incubated for 362-days (eight sampling times). The water content in the pots was maintained periodically by weight at 60% of soil water-holding capacity. The soil samples were analyzed for particulate organic carbon (POC), and total and soluble carbohydrates (CHt and CHs, respectively). Oat and vetch residues decomposed faster than clover, with the decomposition rate constant (k) values of 1.3, 1.4 and 1.9 year⁻¹, respectively. At the end of the experiment, POC concentration was lower in vetch (1.83 g kg⁻¹) and clover (1.96 g kg⁻¹) than in oat (2.21 g kg⁻¹) and fallow (3.00 g kg⁻¹), indicating a loss of 45-64% from their initial values. Soil CHt was influenced by residue quality, where the periods of greatest residue decay (vetch 21-59 days and oat 93-130 days) corresponded to higher soil CHt. Hence, this organic carbon fraction is sensitive to residue decomposition and can be indicators of changes in soil organic matter over short periods of time.

Organic quality changes during residue decomposition

Sa Pereira E, M. Duval, J.A. Galantini. 2017. Decomposition from legume and non-legume crop residues: effects on soil organic carbon fractions under controlled conditions. Spanish Journal of Soil Science 7(2) 86-96 https://doi.org/10.3232/SJSS.2017.V7.N2.06

Cover Crops in the Production System

Use of a three-compartment model to evaluate the dynamics of cover crop residues

Cover crop (CC) residues protect the soil from erosion and their permanence on the surface is largely influenced by their biochemical constituents. In this study the dynamics of CC residue decomposition by applying mathematical models was described. The kinetics of decomposition of residues was obtained from a laboratory incubation experiment. Three CC shoot residues were applied on the soil surface and incubated for 362-days (with eight sampling times). Oats and vetch residues decomposed the most than clover, which k values were 3.6 × 10⁻³, 3.7 × 10⁻³ and 5.3 × 10⁻³ day⁻¹, respectively. The three-compartment model (non-structural carbohydrates, cellulose-hemicellulose and lignin) to simulate residue decomposition, presented a close fit between simulated and measured data. The decomposition rate constant (k) of CC can be used to estimate how long residues will remain in the field and how they could affect soil organic carbon.

Residue decomposition model

Sa Pereira E, J.A. Galantini, M. Duval. 2017. Use of a three-compartment model to evaluate the dynamics of cover crop residues. Archives of Agronomy and Soil Science 63(11)1623-1629. http://dx.doi.org/10.1080/03650340.2017.1296137

Cover Crops in the Production System

Production and quality of cover crops in soybean monoculture

Cover crops (CC) are an alternative to improve soil organic matter, capture labile nutrients and minimizing its leaching losses during long-term fallows, typical of agricultural systems with high frequency soybean (Glycine max L. Merr.). The objective was to evaluate the production and nutrient content of different CC in simplified system (soybean monoculture) under no-tillage. CC used were: (T) bread wheat (Triticum aestivum L.), (A) oat (Avena sativa L.), (V) vetch (Vicia sativa L.) and (A+V) oat + vetch. Upon drying the CC was determined: production of total aerial dry matter (MS), biochemical composition (cellulose, hemicellulose and lignin), macro- and micronutrients. Dry matter production in T and A ranged between 7.2 and 11.1 Mg ha^-1, differing significantly from V with values between 4.1 and 4.6 Mg ha^-1. Carbon concentration did not differ between CC (43-45% C). The amount of N accumulated in aboveground biomass ranged between 102 and 212 kg N ha^-1, showing differences only between years. The concentration of structural polymers clearly differ between CC species, where T and A showed higher concentrations of cellulose and hemicellulose regarding V. Conversely, V showed higher concentrations of nonstructural carbohydrates and lignin than grasses. Winter grasses as CC were more efficient in producing MS and therefore more effectives to contribute to increased soil organic matter, promoting the recycling of macro- and micronutrients, preventing the leaching of those most labile.

Wheat-vetch, Biochemical composition

Duval, Matías E.; Galantini, Juan A.; Capurro, Julia E.; Beltrán, Marcelo J. 2017. Producción y calidad de diferentes cultivos de cobertura en monocultivo de soja. Ciencias Agronómicas (FCA-UNR) XXIX 7-13.
(View more....)

Morpho-structural evaluation of various soils subjected to different use intensity under no-tillage

According to many evidences, in Argentina, no-tillage (NT) coupled with soybean monoculture leads to adverse soil structure features. While some farmers have simplified the production system through soybean monoculture others have intensified the land-use by increasing the number and diversity in the crop sequence. The effects of this intensification, in terms of soil structural quality, are contradictory, possibly caused by the increase of machinery traffic. In order to assess soil structural quality and the performance of selected morpho-structural variables with different levels of intensification, we analyzed plots under NT with high and low crop sequence intensification (Good −GAP- and Poor −PAP-, agricultural practices respectively) and reference plots in four soils (two Argiudolls, an Haplustoll and an Hapludert) of the Argentinian Pampean region. The morpho-structural variables assessed were Visual Evaluation of Soil Structure at field scale (VESS), visible porosity (Vp), roundness (Rd), eccentricity (Ecc) and 3-D aggregate features (faces, corners and edges). Plots with higher frequency of cereals in the sequence (GAP) presented on average higher VESS scores, higher Vp values and less rounded aggregates with more faces and corners, suggesting that crop sequence intensification induces favorable structural features. VESS, Vp, number of faces and corners were strongly correlated with aggregate stability tests mainly with the fast and fast10s test (r: −0.56, −0.74; 0.48, 0.52; 0.46, 0.49 and 0.42, 0.50, respectively) and with the more labile organic carbon fractions −POCc and POCf- (r: −0.49, −0.5; 0.5, ns; 0.38, 0.48 and 0.31, 0.43, respectively). These observations suggest that the variables examined, concerning aggregates and pores were sensitive to changes in crop sequence and are useful soil quality indicators. However, the occurrence of platy structures also under GAP shows the need to adjust the VESS method to the NT system. Besides, the effect of agricultural intensification on soil morphology was modulated by soil type. In consequence, this last factor has also to be considered for the definition of a quality indicator to track the effect of crop sequences intensification under no-till management.

Palabras clave

Behrends K.F., M.A. Soria, M.G. Castiglioni, M. Duval, J. Galantini, H. Morrás. 2017. Morpho-structural evaluation of various soils subjected to different use intensity under no-tillage. Soil & Tillage Research 169: 124-137.

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.