Mário de Carvalho

Evaluation of spatial and temporal variability of pasture based on topography and the quality of the rainy season

Yield and botanical composition of a given dry-land pasture are heavily influenced by rainfall distribution, and vary according to topography. Through analyzing these parameters, it is possible to identify patterns of spatial distribution, related to topographic characteristics, which can be used to improve spatial management of pasture. The main objective of this project was to assess the role of rainfall, temperature and topography in the spatial and temporal variability of pasture and establish models for predicting the spatial distribution and yield of certain plant species, based on its topographic characteristics. This study was carried out over three years, 2004 to 2006, in a dry-land pasture located in Southern Portugal. The data obtained were analyzed as a function of distance to flow lines and the results demonstrate that certain topographical characteristics, associated with agronomic information, can be very useful in explaining the spatial and temporal variability of yield and the botanical composition of the pasture. The slope of the linear regression of the variables mentioned can be used to estimate the spatial variation of yield and the botanical composition as a function of distance to flow lines. The regression coefficient can be estimated from the annual rainfall, given the strong correlation between the two.

Socioeconomic Evaluation of Drought Effects. Main Principles and Application to Guadiana and Algarve Case Studies

Drought situations can have significant impacts, affecting large areas and imposing relevant restrictions on multiple economic activities. The severity of those impacts is, normally, assessed through meteorological, agricultural and/or hydrological indices or even through estimation of water deficits or reduction of production yields (for agriculture). However, those assessments usually do not represent the socioeconomic importance of the impacts and the results are not comparable for different types of impacts or distinct regions. In this context, the present work enunciates the main principles to be considered and a methodological approach for socioeconomic evaluation of drought effects, regarding the main supply and demand characteristics of a region (water sources and associated uses), and the hydrological interlinked effects of drought situations. Moreover it describes the methodology process application to Portuguese reality and existing data as the basis of drought’s severity assessment, focusing on two drought prone areas in Portugal: the Guadiana and the Ribeiras do Algarve river basin case studies. Regarding the main specificities of the referred case studies, the economic activities (and water dependent sectors) considered for this methodology were the agricultural and the urban water supply sectors. For each of those sectors, specific assessment procedures where developed in order to estimate the respective economic impacts caused by the drought situation in the area of analysis. A global assessment of the socioeconomic relevance of drought impacts in a region is ensured through comparison of the estimated total economic impacts to the region’s annual average of the Gross Domestic Product (GDP), that enabling the comparison of results for different regions of analysis. The methodology may be applicable to any region with common hydrological and water use data and was developed to be of support for drought management and application on a drought early warning system.

Techniques for Arbuscular Mycorrhiza Inoculum Reduction

Given the ubiquous presence of AM fungi, a major constraint to the evaluation of the activity of AM colonization has been the need to account for the indigenous soil native inoculum. This has to be controlled (i.e., reduced or eliminated) if we are to obtain a true control treatment for analysis of arbuscular mycorrhizas in natural substrates. There are various procedures possible for achieving such an objective, and the purpose of this chapter is to provide details of a number of techniques and present some evaluation of their advantages and disadvantages.

Tree influence on soil and pasture: contribution of proximal sensing to pasture productivity and quality estimation in montado ecosystems

ABSTRACT Montado is a silvo-pastoral ecosystem of the Mediterranean region, a mixed system of trees and pasture, subject to animal grazing. Farmers need information on pasture production and quality in order to assess the direct effect of tree presence on the productivity of their pastoral system, and to devise management that balances farm production and profitability with sustainable soil management. The main objectives of this work were (1) to evaluate tree influence on soil and pasture parameters and (2) to evaluate the use of proximal sensing techniques that have potential for monitoring aspects related to spatial and temporal variability of pasture productivity and quality in montado ecosystems. Both objectives can support the decision-making process of the farmer. The study field is located in Mitra farm, in Southern Portugal. During October 2015, 24 geo-referenced composite soil samples (12 under tree canopy and 12 outside tree canopy) were collected from the 0.0–0.3 m soil layer. The soil samples were analysed for texture (sand, silt, and clay content), moisture content, pH, organic matter, total nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), and manganese (Mn). The evolution of the pasture was recorded in the 24 sampling points at five monitoring dates: at the end of autumn (December 2015), at the end of winter (March 2016), and then monthly during spring 2016 (April, May, and June). The following pasture parameters were measured: normalized difference vegetation index (NDVI), capacitance, temperature, green and dry matter, ash, crude protein (CP), and neutral detergent fibre. Soil under tree canopy had significantly higher levels of organic matter, N, P, K, and Mg, and better pasture quality while the pasture productivity was higher outside tree canopy. The correlation between pasture direct measurements and sensor parameters was more consistent between capacitance and pasture productivity and between NDVI and CP. The use of fast and efficient tools associated with geo-referenced systems can greatly simplify the pasture monitoring process, which is the basis for estimating feed availability in the field. The knowledge of biomass quality and quantity is fundamental to support decision-making regarding animal stocking rates and rotation among grazing parcels.

Efficient use of water in the southern region of Portugal: agronomic aspects

The present paper analyses several aspects of agricultural production techniques and their relationship with an efficient water use paying special attention to the conditions prevailing in the Mediterranean environment. The agronomic aspects discussed are the following: crop rotation, seeding date and nitrogen fertilisation. With regard to the crop rotation in the effect of the preceding crop on the yield of the following wheat crop is analysed for different precipitation regimes as they frequently occur under Mediterranean conditions. What the concerned seeding date is and its effect on the water availability is studied for both the autumn and spring sown annual crops. Finally the importance of the quantity and distribution of the nitrogen fertilisation for reasonable crop yields in wet years is discussed.

A Holistic Approach to the Evaluation of the Montado Ecosystem Using Proximal Sensors

The Montado is a silvo-pastoral system characterized by open canopy woodlands with natural or cultivated grassland in the undercover and grazing animals. The aims of this study were to present several proximal sensors with potential to monitor relevant variables in the complex montado ecosystem and demonstrate their application in a case study designed to evaluate the effect of trees on the pasture. This work uses data collected between March and June 2016, at peak of dryland pasture production under typical Mediterranean conditions, in twenty four sampling points, half under tree canopy (UTC) and half outside tree canopy (OTC). Correlations were established between pasture biomass and capacitance measured by a commercial probe and between pasture quality and normalized difference vegetation index (NDVI) measured by a commercial active optical sensor. The interest of altimetric and apparent soil electrical conductivity maps as the first step in the implementation of precision agriculture projects was demonstrated. The use of proximal sensors to monitor soil moisture content, pasture photosynthetically active radiation and temperature helped to explain the influence of trees on pasture productivity and quality. The significant and strong correlations obtained between capacitance and pasture biomass and between NDVI and pasture nutritive value (in terms of crude protein, CP and neutral detergent fibre, NDF) can make an important contribution to determination of key components of pasture productivity and quality and implementation of site-specific pasture management. Animal tracking demonstrated its potential to be an important tool for understanding the interaction between various factors and components that interrelate in the montado ecosystem and to support grazing management decisions.

New Tools to Investigate Biological Diversity and Functional Consequences

To exploit the opportunities offered by our increased understanding of arbuscular mycorrhiza (AM) diversity and the potential to manage it requires greater knowledge of the indigenous AM fungi (AMF) involved in the symbiosis with target plants. Our ability to fully describe AMF diversity is still at early stage in terms of the taxonomic units present, despite recent developments in DNA sequencing capacity. The information required is the number of species or taxonomic groups present, the number of individuals that can be identified as belonging to the same group, and the level of variability there is within such a group in terms of their capability to enhance growth. With the techniques available it is possible to be precise over the molecular makeup of individuals but it is more difficult to be certain as to which species they may belong, particularly if that species has been mainly been identified through its morphological characteristics, especially those of its spores, rather than from DNA sequencing. Consequently it is operational taxonomic units (OTUs) or virtual taxa that are used to describe taxonomic groups, which are identified solely through molecular techniques. Nevertheless variability exists in both species and OTUs. Effectiveness of a mycorrhizal symbiosis depends on environmental conditions, but is also influenced by the community of higher plants as well as the local soil biota. Establishing linkages between genetic and the functional diversity under field conditions with biotic and abiotic stresses is more challenging. Successful assemblages of AMF combine the ability to acquire P and to protect host plants against pathogens or abiotic stresses, consistent with greater diversity being associated with greater ecosystem functioning through enhanced trait richness. To capitalize on the potential benefits from managing AMF diversity, appropriate solutions are needed for different agroecosystems and applicable on a site-by-site basis. Identifying genetic and molecular markers that allows quantitative assessment of the potential to exploit indigenous AMF is crucial. Within AMF hyphae two markers have been identified in the ribosomal DNA that can be used to identify OTUs. Similarly mitochondrial large ribosomal subunit sequences have also been used. Short-term considerations suggest that more effort is needed to identify key markers in major crops for AMF assemblages that function effectively to offset major biotic and abiotic stresses.To exploit the opportunities offered by our increased understanding of arbuscular mycorrhiza (AM) diversity and the potential to manage it requires greater knowledge of the indigenous AM fungi (AMF) involved in the symbiosis with target plants. Our ability to fully describe AMF diversity is still at early stage in terms of the taxonomic units present, despite recent developments in DNA sequencing capacity. The information required is the number of species or taxonomic groups present, the number of individuals that can be identified as belonging to the same group, and the level of variability there is within such a group in terms of their capability to enhance growth. With the techniques available it is possible to be precise over the molecular makeup of individuals but it is more difficult to be certain as to which species they may belong, particularly if that species has been mainly been identified through its morphological characteristics, especially those of its spores, rather than from DNA sequencing. Consequently it is operational taxonomic units (OTUs) or virtual taxa that are used to describe taxonomic groups, which are identified solely through molecular techniques. Nevertheless variability exists in both species and OTUs. Effectiveness of a mycorrhizal symbiosis depends on environmental conditions, but is also influenced by the community of higher plants as well as the local soil biota. Establishing linkages between genetic and the functional diversity under field conditions with biotic and abiotic stresses is more challenging. Successful assemblages of AMF combine the ability to acquire P and to protect host plants against pathogens or abiotic stresses, consistent with greater diversity being associated with greater ecosystem functioning through enhanced trait richness. To capitalize on the potential benefits from managing AMF diversity, appropriate solutions are needed for different agroecosystems and applicable on a site-by-site basis. Identifying genetic and molecular markers that allows quantitative assessment of the potential to exploit indigenous AMF is crucial. Within AMF hyphae two markers have been identified in the ribosomal DNA that can be used to identify OTUs. Similarly mitochondrial large ribosomal subunit sequences have also been used. Short-term considerations suggest that more effort is needed to identify key markers in major crops for AMF assemblages that function effectively to offset major biotic and abiotic stresses.

Agronomic Opportunities to Modify Cropping Systems and Soil Conditions Considered Supportive of an Abundant, Diverse AMF Population

There is a great functional diversity within and between different species of arbuscular mycorrhizal fungi (AMF) in terms of the benefits they may confer to host plants, such as the acquisition of nutrients or protection from biotic and abiotic stresses. It is critical to understand how the various practices available for use within production systems, particularly those compatible with the sustainable intensification of agriculture, impact AMF, and their diversity. In commercial crop production farmers need to prepare the land for seeding, protect the developing and maturing plants from pests and diseases, provide a suitable supply of nutrients and water, and ensure a timely harvest. Tillage systems vary greatly in the extent of their disturbance of soil in terms of the depth and fragmentation, affecting AMF abundance and diversity. In contrast to inversion tillage, the AMF colonization rate of crops under no-till starts earlier and develops faster due to the presence in the soil of an intact extraradical mycelium, which enhances the role of AMF in the uptake of nutrients and the protection against stresses. Rational use of applied nutrients, supplied either through the application of organic amendments or inorganic fertilizers, which is essential to maintain soil productivity, is compatible with maintaining an abundant and diverse AMF population, especially in association with no-till systems. Crop rotation has been the traditional approach to ensure that neither pests nor diseases of a particular crop build up to epidemic proportions in the soil or field environment. There is a relationship between the diversity of plant material above ground and the AMF present below the soil surface. Reducing soil disturbance by tillage, adding organic amendments, keeping harvest residues and use of cover crops all help to increase soil organic matter, which in turn plays an important role in reducing application of mineral fertilizer and the need for herbicides. By employing cropping practices that achieve these goals, it might be possible to improve AMF diversity to levels identical to that in natural ecosystems. There is an urgent need to use the new generation of molecular tools for the evaluation of effects of cropping systems on biodiversity of AMF associated with field crops, especially for AMF from different functional groups.

Chapter 5 - Impacts on Host Plants of Interactions Between AMF and Other Soil Organisms in the Rhizosphere*

There is a considerable evidence of both cooperation and synergism between groups of organisms concentrated around mycorrhiza rather than the rhizosphere of plants being inhabited by a very diverse population of competing organisms. A huge increase has taken place in the detailed understanding of the microbial environment surrounding plant root systems and of the processes involved in the establishment of the mycorrhiza symbiosis. It seems that if the interaction between microbes and plants is of particular interest to the development of a sustainable agriculture, the relationship is carefully choreographed through complex signaling systems. This development has also allowed a more holistic approach to the investigation of mycorrhiza and the possibility for optimizing the beneficial aspects of the symbiosis. Much of our detailed knowledge of the interaction between arbuscular mycorrhizal fungi (AMF), bacteria, and plants comes from legumes, members of the Fabaceae, which form symbiotic relationships with both AMF and nitrogen fixing “rhizobia.” The three groups of organisms establish a tripartite interaction that may also involve additional endophytic partners. There is considerable similarity in the development of the symbiosis between the contrasting microbial symbionts – fungi and bacteria – and the host legume. Although there is no competition for infection sites between AMF and rhizobia, there can be resources from the host plant. The benefits from mycorrhiza in the tripartite interaction are enhanced when the host plant is colonized early, especially from an intact extraradical mycelium (ERM). Such AMF colonization can also stimulate more rapid formation of root nodules by rhizobia. An increased rate of photosynthesis or greater green leaf area can be triggered in the host plant in response to AMF colonization, which enhances the available carbon resources within the tripartite symbiosis. The interactions between AMF and other bacteria is less well understood but some of the species that are found in close association with AMF have been shown to enhance the formation of mycorrhiza on receptive hosts and most of the “mycorrhiza helper bacteria” have some beneficial effects on the development of the mycorrhizal host plant. The interactions with soil fauna, particularly grazing arthropods, do not suggest that AMF or their host plants are adversely affected by these activities.

Management of Biological and Functional Diversity in Arbuscular Mycorrhizal Fungi Within Cropping Systems

The potential benefits of arbuscular mycorrhizal fungi (AMF) are crucial aspects for the sustainable intensification of agriculture. However, in industrialized regions injudicious use of both manure and excessive application of fertilizers and pesticides are imposing unacceptable environmental impacts and in regions where there is already an urgent need to improve land productivity, the resources required to enhance productivity are scarce. The intentional use of AMF within agricultural cropping systems has received little attention, especially for large-scale production. Three key aspects prevent the full exploitation of AMF in agricultural ecosystems: the benefits of arbuscular mycorrhiza symbiosis (AM) are dependent on the biological diversity of both partners; the time required to achieve an effective colonization may restrict the benefits when protection against stresses are a major role of AM; the large cost of commercial inoculum coupled with its lack of biological diversity. These concerns clearly establish that the need to develop strategies for the management of indigenous AMF within different cropping system, specifically focusing on how to control the AMF biological diversity in the roots of the crops and to enhance early colonization. The answer to the latter is well-established in the literature and is the maintenance in the soil of an intact extraradical mycelium (ERM) to act as preferential AMF propagule. Under these conditions, colonization starts earlier and develops faster, enhancing the role of AMF in bioprotection of host plants. The management of AMF diversity present in the roots of a crop is still the major difficulty within the cropping systems. However, in a plant succession it appears possible to manage the AMF biological diversity present in the roots of the second plant if intact ERM developed by the first is the preferential initiator of colonization. This approach significantly improves the role of AMF in the protection of plants against biotic and abiotic stresses. Therefore the right choice of crop rotation, including cover crops or even the weeds that germinate before the seeding of the crop, and the adoption of appropriate tillage techniques that maintain the integrity of ERM, provide the potential to overcome the two major limitations to the intentional use of indigenous AMF within cropping systems. Criteria to select the plants to be included in a succession must be developed considering their different functional groups, which can be identified at least at the family level. For example, the Fabaceae and Poacea, harbor distinct AMF communities. These two plant families include many cultivated plants and, depending on the prevailing stresses, they can certainly provide useful candidates for this strategy. Numerous research requirements are identified but modern genomics technology brings the possibility closer that compatible assemblages of AMF and helper bacteria will be discovered.