Relationship Between Irrigation Thresholds and Potato Tuber Depth in Sandy Soil

Soil disturbance resulting from tuber crop harvesting is a major threat to soil health. The depth of soil intervention is a critical factor that further strengthens the effects of such disturbance and makes harvest one of the most harmful cropping operations. In the case of potato, soil moisture is a determining factor for root and stolon development, hence, a deeper soil intervention may be required at harvest. While potato ranks as the fourth most cultivated crop worldwide, the impact of soil moisture on potato tuber vertical and horizontal distribution has received very little attention. The objective of this study was to evaluate the effects of four soil matric potential thresholds (SMPTs; –10, –20, –30, and –45 kPa) on the spatial (vertical and horizontal) distribution of potato tubers grown in plastic containers filled with sandy soil using an X-ray computed tomography scanner. The results of the experiments conducted in a greenhouse environment suggest that the horizontal distribution of the tubers did not differ significantly across the irrigation treatments. However, a linear relationship between SMPT, and therefore irrigation threshold, and potato tuber depth was observed. In addition, the deepest tuber position was observed under the –10 kPa SMPT, while the tubers were closer to the soil surface under the –45 kPa SMPT, which could lead to a greater preponderance of tuber diseases such as late blight or greening. Thus, potato irrigation events implementing a SMPT between –20 and –30 kPa could reduce the harvest depth, hence, decreasing the negative impacts of soil disturbance on soil structural stability and soil organic carbon degradation while mitigating the impacts of disease as well as reducing fuel costs, greenhouse gas emissions, soil loss and erosion

Soil Bacterial Community Associated With High Potato Production and Minimal Water Use

In agriculture, water consumption for crop production represents 69% of all water use. Precision irrigation systems based on available soil water have been developed to improve crop production, reducing water use. Besides the improvements in irrigation management, a better resolution of the optimal water level is required, and revealing the impact of soil matric potential on the soil microbial community may help. Here, the effect of four soil matric potential treatments (−15 kPa, −25 kPa, −30 kPa, and −45 kPa) was evaluated on the soil microbial community across three potato cultivars and two soil types (silt and sand). The results confirmed the soil matric potential with −25 kPa as the optimal irrigation level, which promoted high potato production using the minimal water use. The irrigation levels affected the composition, predicted functionality, and the ecological network of soil bacterial community. Water excess (−15 kPa) and deficit (−30 and −45 kPa) promoted an increase in microbial interaction and alpha-diversity. The results suggested higher Positive/Negative ratio for phyla Proteobacteria, Actinobacteria, and Acidobacteria in optimal irrigation level (−25 kPa) than other irrigation levels. Also, correlation analyses revealed an interesting association between the irrigation levels, potato production, and bacterial functionality, especially in the carbon cycle (fixation and emission). Therefore, this study proposed important associations between the soil bacterial community and water management, focusing on high potato production and minimal water use. The advancement of this knowledge may lead to a more comprehensive assessment of the optimal irrigation levels of others crop production systems. Furthermore, the inclusion of biological mechanisms, especially microbial interactions, in agriculture studies has the potential to contribute to the development of water management practices conducive to both increasing crop yield and maintaining a sustainable soil environment

Dinâmica espaço-temporal da comunidade microbiana de solos cultivados com cana-de-açúcar

The environmental conditions driving the microbial community dynamics in crop soils remain unclear. Here, we focused on the spatial and temporal dynamics of microbial communities in soils cultivated with sugarcane under different soil managements, during two years. Our work was divided into three essential parts, where i) we discuss ecological models and theories for the microbial exploration in crop soils, arguing that those ecological models, which partitioned the microbial communities, may increase the resolution of the environmental and the microbial interactions; ii) we developed a probabilistic model based on the occurrence frequency of microorganisms across systems identifying the core microbial community. The model is based on the Poisson distribution, and it was tested in four datasets available in the Earth Microbiome Project; iii) we identified the core bacterial and fungal communities across soils cultivated with sugarcane, verifying which abiotic components could drive the composition of groups. We increased the resolution of the environmental and the microbial interactions, showing that the core and the variable microbial communities are driven by distinct abiotic components. We also observed that the core and variable microbial communities harbor distinct potential functionality, as nitrogen fixation being more predicted to the core bacterial commmunity, and nitrification process for the variable bacterial community. Our finds increase the knowledge of microbial dynamics and functionality, helping to reveal and explore the crop system microbiome.As condições ambientais que podem modular a dinâmica da comunidade microbiana em solos de culturas são pouco conhecidas. O presente trabalho foi dividido em três partes essenciais, onde i) discutiu-se modelos e teorias ecológicas para a exploração microbiana em solo agrícolas, argumentando-se que os modelos ecológicos que particionam as comunidades microbianas, poderiam aumentar a resolução entre interações microbianas e o ambiente, ii) desenvolveu-se um modelo probabilístico baseado na freqüência de ocorrência de microorganismos através de sistema identificando a comunidade microbiana \"core\". O modelo baseou-se na distribuição de Poisson, sendo este testado em quatro conjuntos de dados disponíveis no Projeto \"Earth Microbiome\", e iii) identificou-se as comunidades bacterianas e fúngicas core em solos cultivados com cana-de-açúcar, verificando-se quais componentes abióticos poderiam modular a composição dos grupos. Com isso, elevou-se a resolução das interações ambiental e microbiana, indicando que o core microbiano e as comunidades microbianas variáveis são moduladas por componentes abióticos distintos. Observou-se também que as comunidades core e variável possuem funcionalidade potencial distinta, como fixação de nitrogênio mais predita para o core bacteriano e processo de nitrificação para a comunidade variável de bactérias. Os resultados do presente trabalho elevam o conhecimento da dinâmica e funcionalidade microbiana, ajudando a revelar e explorar o microbioma do sistema de cultivo

Biogeography of fungal communities in sugarcane fields

A cana-de-açúcar é atualmente a cultura de maior importância agrícola do Estado de São Paulo, a partir da qual são gerados açúcar e etanol, além de vários outros subprodutos. No entanto, com a expansão das fronteiras agrícolas e alterações nas práticas de manejo, ocorre atualmente um momento de adequação de tal cultivo, que visa uma maior produtividade e sustentabilidade de produção. Para isto, dentre outros fatores, o papel da comunidade microbiana presente nos solos pode ter fundamental importância, auxiliando no melhor desenvolvimento da planta. No entanto, pouco se sabe sobre a comunidade microbiana existente nos solos cultivados com cana-de-açúcar. Dessa forma, este trabalho teve como objetivo avaliar a diversidade e a abundância de fungos em solos de cultivo de cana-deaçúcar no estado de São Paulo, em áreas sob diferentes atributos químicos, físicos e de manejo. Objetivou-se também, verificar a ocorrência de padrões biogeográficos na estruturação de tais comunidades. Para isso, foi realizada a análise da estrutura das comunidades fúngicas por polimorfismo de comprimento de fragmentos de restrição terminal (T-RFLP), juntamente com a quantificação destas comunidades por meio da PCR em tempo real (qPCR) em 476 amostras de solo, obtidas de 11 áreas de cultivo (usinas). Dentro deste conjunto de dados, temos que os atributos químicos, físicos e manejo explicam maiores valores de variância dentro de cada área amostra, mas pouco explicam da variância geral dos dados, sugerindo a ocorrência de padrões biogeográficos das comunidades de fungos neste ambiente. Tal ocorrência foi confirmada pela significância estatística da correlação entre distância e dissimilaridade das comunidades de fungos, dando suporte a geração dos primeiros mapas biogeográficos de fungos em tais solos. Adicionalmente, a abundância de fungos mostrou-se relacionada com a produtividade da cultura, indicando este ser um dos fatores que modulam a produtividade de cana-de-açúcar nas áreas avaliadas.The sugarcane is nowadays, the most important crop in the State of São Paulo, serving as the raw material for the production of sugar and ethanol, besides many others by-products. Considering the expansion of agricultural barriers, and shifts in fields management, such cultivation is under a re-arrangement process, aiming to a higher productivity and sustainability. In order to achieve that, among other factors, the role of microbial communities present in soils can be essential to support plant development. However, a few is known about the microbial community under sugarcane crop production soils. Hence, this work intended to evaluate the fungi diversity and abundance in soils cultivated with sugarcane in the State of São Paulo, exploring areas under distinct chemical and physical attributes and also distinct management practices. It was also aimed to determine the occurrence of biogeographically patterns in the structure of such communities. Indeed, it was made the analysis of the fungal community structure by terminal restriction fragment length polymorphism (T-RFLP), together with the quantification of these communities by real time PCR (qPCR) in 476 soils samples, collected in 11 areas cultivated with sugarcane (mills). Within this dataset, it was found that chemical, physical and management attributes explain higher values of variance within each sampled area, but explain little about the total variance of data, suggesting the occurrence of biogeographically patterns in fungal communities in this environment. It was confirmed by the statistical significance of the correlation between distance and dissimilarity of fungal communities, supporting the generation of very first biogeographically maps in such soils. Additionally, the abundance of fungi revealed to be related with sugarcane productivity, indicating this issue as one of the factors modulating the sugarcane productivity in the evaluated areas

Exploring interactions of plant microbiomes

A plethora of microbial cells is present in every gram of soil, and microbes are found extensively in plant and animal tissues. The mechanisms governed by microorganisms in the regulation of physiological processes of their hosts have been extensively studied in the light of recent findings on microbiomes. In plants, the components of these microbiomes may form distinct communities, such as those inhabiting the plant rhizosphere, the endosphere and the phyllosphere. In each of these niches, the "microbial tissue" is established by, and responds to, specific selective pressures. Although there is no clear picture of the overall role of the plant microbiome, there is substantial evidence that these communities are involved in disease control, enhance nutrient acquisition, and affect stress tolerance. In this review, we first summarize features of microbial communities that compose the plant microbiome and further present a series of studies describing the underpinning factors that shape the phylogenetic and functional plant-associated communities. We advocate the idea that understanding the mechanisms by which plants select and interact with their microbiomes may have a direct effect on plant development and health, and further lead to the establishment of novel microbiome-driven strategies, that can cope with the development of a more sustainable agriculture

Exploring interactions of plant microbiomes

A plethora of microbial cells is present in every gram of soil, and microbes are found extensively in plant and animal tissues. The mechanisms governed by microorganisms in the regulation of physiological processes of their hosts have been extensively studied in the light of recent findings on microbiomes. In plants, the components of these microbiomes may form distinct communities, such as those inhabiting the plant rhizosphere, the endosphere and the phyllosphere. In each of these niches, the "microbial tissue" is established by, and responds to, specific selective pressures. Although there is no clear picture of the overall role of the plant microbiome, there is substantial evidence that these communities are involved in disease control, enhance nutrient acquisition, and affect stress tolerance. In this review, we first summarize features of microbial communities that compose the plant microbiome and further present a series of studies describing the underpinning factors that shape the phylogenetic and functional plant-associated communities. We advocate the idea that understanding the mechanisms by which plants select and interact with their microbiomes may have a direct effect on plant development and health, and further lead to the establishment of novel microbiome-driven strategies, that can cope with the development of a more sustainable agriculture

Spatiotemporal variability of soil hydraulic properties under drainage and recharge cycles

Abstract. The installation of drainage systems can cause anthropic evolution of the soil profile. Natural consolidation, filtration and clogging of soil pores by colloidal particles may be accelerated by water management practices, such as irrigation, drainage and flooding, and could reduce the drainage capacity of the soil. X-ray tomography can be used to describe soil hydraulic properties at the small scale and to study several physical soil processes, especially those related to the migration of colloidal particles and consolidation. Wavelet analyses can decompose an observed time series of soil matric potential into various components that can be used to determine the temporal periodicity of drainage and recharge. The main objective of this study was to analyze the spatiotemporal variability in the hydraulic properties of a sandy soil and the time series of matric potential during repeated cycles of drainage and recharge from the bottom of a soil profile using a medical X-ray computerized tomography (CT) scanner and wavelet transforms. A soil column laboratory experiment was set up to monitor the pressure head, water inflow and outflow, and the movement of the tracers KBr and ZrO2. Tomographic scans have been used to analyze the spatiotemporal variability in the soil hydraulic properties. The results show that repeated drainage and recharge cycles greatly affect the evolution of soil hydraulic properties by reducing drainage and capillary capacities. Knowledge of the mechanisms responsible for this human-induced soil genesis is important for water management in agricultural systems. This information may allow prediction of soil evolution according to soil texture, drainage system design and water management, thereby anticipating and possibly controlling problems related to soil hydrodynamics

Potato Varieties Response to Soil Matric Potential Based Irrigation

Potato is one of the most cropped plants worldwide. Hundreds of different varieties are cultivated only in North America. Potato growers usually crop multiple varieties on their farms to answer the market demands for potato’s specific physical properties. However, few pieces of information are available regarding the optimal management of irrigation across potato varieties. Knowing that modern potatoes share genetics similarities, the optimal irrigation comfort zone for the potato crop might be the same for different groups of varieties. This study evaluates the effect of precision irrigation thresholds on the potato yields of three varieties (Envol: very early, Kalmia: early, and Red Maria: mid-late) with different maturity classes. In a greenhouse, a soil matric potential sensor network used in combination with a precise irrigation system allows the identification of a common optimal precision irrigation threshold, allowing optimal yields for the three varieties. This paper presents the first identification of an optimal irrigation threshold, −15 kPa, shared by different potato varieties. The optimal irrigation threshold identified in this study is not dependent on the maturity class, plant height or tuber potential production. The determination of an optimal precision irrigation threshold will allow potato growers to adapt their farm management processes to integrate more sustainable water management practices as they will be able to irrigate a field with multiple varieties with the same threshold