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  • Open access
  • 75 Reads
Application of dairy manure amended with mineral nitrogen fertilizer on stubble-covered soil: effects on ammonia emissions.

Mineral fertilizers are the major nitrogen source to crops. However, manure application contributes to the increase of soil organic matter and the addition of beneficial microbes, besides also delivering nutrients to plants. The transport costs within and between farms and higher application rates needed relative to mineral fertilizers are some of the limitations associated with manure application. The mixture of manure and mineral fertilizer might be an alternative to decrease manure application rates, enabling to cover more agricultural lands, improving application efficiency and also to reduce over-fertilization with phosphorus as generally occurred when using manure. The present work aimed to evaluate the effects of mineral nitrogen fertilizer amendment to manure, right before application, on ammonia (NH3) emissions. A pot experiment using soil covered by wheat stubble was performed at Instituto Superior de Agronomia, Lisbon, Portugal. The treatments considered were: Control (unfertilized treatment), Urea (U), Ammonium nitrate (AN), Manure (MAN), Urea + Manure (UMAN), Ammonium nitrate + Manure (ANMAN). An equivalent amount of total-N was applied in all fertilized treatments. The ammonia emissions were collected through a dynamic chamber system for seven days. The manure amended with mineral fertilizers led to higher NH3 emissions than each isolated component. This might be motivated by the slightly alkaline pH of the manure. UMAN presented the highest cumulative NH3 emission, 357% and 87% more than U and MAN, respectively. ANMAN emitted 1,552% more than AN and 54% more than MAN. Thus, it can be concluded that the application of dairy manure mixed with urea or ammonium nitrate on stubble-covered soil stimulates NH3 emissions relative to isolated application of manure or mineral fertilizer. More studies over raw manure/mineral fertilizer combinations and management strategies that may reduce ammonia emissions from organic-mineral fertilizers are required to allow efficient use of this fertilizing strategy in no-tillage agriculture.

  • Open access
  • 79 Reads
Calibration methodology of a remote PRI sensor for photosynthesis rate assessment in greenhouses

Early detection of different types of crop stress under greenhouse cultivations is critical in order to optimize yield and resource use efficiency. Objective of the present work is to develop a system which, based on remote sensing, will recognize plant stress by combining microclimate and crop physiology data. The innovation of the platform is based on the integration of a remote PRI sensor that is used to correlate PRI measurements and photosynthesis rate (Ps). In this work, the methodology used for the PRI sensor calibration and acquisition is presented. The values recorded by means of the PRI sensor were correlated with the Ps rate obtained with handheld photosynthesis system. Data of PRI and Ps values were collected under different lighting, temperature and plant water status conditions of a greenhouse tomato crop. The basic statistical parameters of mean and standard deviation values are used to estimate spectral correlation at 530 nm and 570 nm on the interested leaf area. The determination coefficient (R2) of the linear regression obtained between the PRI and Ps data was about 0.9. The obtained equation will be integrated in the sensing system and the data will be used to train a machine learning model in order to detect different type of crop stress under greenhouse conditions. This research is co-financed by Greece and the European Union (European Social Fund- ESF) through the Operational Programme «Human Resources Development, Education and Lifelong Learning» in the context of the project “Reinforcement of Postdoctoral Researchers - 2nd Cycle” (MIS-5033021), implemented by the State Scholarships Foundation (ΙΚΥ).

  • Open access
  • 74 Reads
Precision Agriculture as input for the Rice Grain (Oryza sativa L.) Biofortification with Selenium

With population growth worldwide, the production of quality and quantity food is increasingly pressing. As such, it becomes essential to develop new agricultural technologies to increase productivity. Under this assumption, an agronomic workflow for Se biofortification of two genotypes resulting from genetic breeding (OP1505 and OP1509) were selected for evaluation through foliar fertilization with sodium selenate (Na2SeO4) and sodium selenite (Na2SeO3) with different concentrations (300 and 500 g Se.ha−1). Aiming to characterize, through precision agriculture, the experimental fields production and monitor the state of the culture (slope, surface drainage, water lines and normalized differences vegetation index - NDVI), an Unmanned Aerial Vehicles (UAVs) synchronized by global positioning system (GPS) was used. It was found that after sown, the water drainage pattern became profoundly altered, following the artificial pattern, created by the grooves between plots. NDVI values, compared to the control, did not show significant differences. These data were correlated with physiological monitoring during biofortification. In fact, as shown by the eco-physiological data obtained through leaf gas exchanges, the application of 300 g Se.ha−1 did not show any toxicity effects in the biofortified plants. In a context of innovation, it was concluded that the use of precision agriculture techniques in conjunction with leaf gas exchanges measurements allowed an efficient monitoring of the field conditions and culture to implement a rice biofortification itinerary.

  • Open access
  • 43 Reads
Unravelling impact of Na+, Cl- and their respective transporter in detrimental effects of salt stress on the African rice species (Oryza glaberrima Steud.)

Salinity resistance of the African rice species (Oryza glaberrima) is poorly documented and the specific responses of the plant to Na+ and Cl- toxic ions remain unknown. Moreover, the roles of Na+/H+ antiport and cation-chloride-cotransporter in salt stresses still remain unclear. In 1st experiment, two distinct cultivars TOG5307 and TOG5949 were maintained for 15 days on iso-osmotic nutrient solutions containing 50 mM NaCl, or a combination of Cl- salts (Cl- - dominant) or Na+ salts (Na+ - dominant). Plant water status, ion accumulation, gas exchange and fluorescence related parameters; carbon (∆13C) and nitrogen (δ15N) isotope discrimination were analyzed. TOG5307 exhibited a higher level of resistance than TOG5949 in terms of growth and photosynthesis maintenance and control of Cl- and Na+ accumulation. NaCl was the most detrimental treatment, followed by Na+ -dominant treatment while Cl- -treatment had the lowest effect. Impact of Na+ and Cl- on considered parameters are additive. In 2nd experiment, the two contrasted cultivars (TOG5307 and TOG5949) were exposed during 3 days in nutrient solutions to 75 mM NaCl containing 100 µM amiloride (inhibitor of Na+-H+ antiporters) or 200 µM bumetanide (inhibitor cation-chloride-cotransporters). Amiloride increased Na+ accumulation in roots and leaves to a higher extent in salt-resistant TOG5307 than in salt-sensitive TOG5949. Bumetanide reduced Cl- accumulation in both cultivars as well as K+ accumulation in TOG5307 and Na+ accumulation in TOG5949. Cultivars exhibiting contrasting levels of salinity resistance are available in Oryza glaberrima and salt-tolerant genotypes may constitute a valuable source of gene for classical rice improvement.

  • Open access
  • 72 Reads
Using apparent soil electrical conductivity (ECap) and remote sensing to delineate soil sampling for precision fertilization in a vineyard

The intensification of agriculture has greatly enhanced crop productivity. However, it has also caused greater risk of environmental impacts, such as soil erosion and groundwater pollution. To maintain high crop productivity and reduce environmental emissions, natural resources use efficiency and nutrients recycling must be promoted. The present work aims to provide new insight on the spatial variability of soil chemical properties, particularly in a vineyard, in hopes of attaining site-specific management within a precision fertilization framework. This goal was achieved by establishing three different zones in a 6,77 ha parcel, according to remote sensing of apparent soil electrical conductivity (ECap) and normalized difference vegetation index (NDVI). In each zone, soil samples were collected in the row of vines, at different distances from the plant, and in the inter-row, at different distances from the row. Samples were later chemically described, and the resulting data was statistically analyzed. Using ECap and NDVI as tools in the design of distinct zones within a vineyard was highly effective, with most of the soil chemical properties varying at the highest significance level, as seen in the ANOVA test (p<0,001). The relationships between ECap and soil salinity (laboratory electrical conductivity - EC1:2,5), ECap and exchangeable cations, and between NDVI and soil nitrogen (N) were evident in this case study. Further results showed that when the sample was collected directly in the row, the distance from the plant had no impact on the soil’s selected properties. However, when the sample was collected in the inter-row, the distance to the row significantly affected the selected soil properties. Overall, the results revealed potential for the implementation of site-specific crop fertilization and soil quality management.

  • Open access
  • 109 Reads
Salt-affected soils at the farm scale: successful experiences and innovation needs

Climate change, land use and management malpractices are increasing the areas of salt-affected soils, threatening soil health and the economical sustainability of farms. Salt-affected soils are mainly characterized by an excess of soluble salts, in which case they are classified as saline, or by an excess of sodium ions, sodic soils, or a combination of these conditions. Causes and processes are manifold and variable in space and time. There is the need to continuously update strategies to tackle salt-affected soils, finding solutions tailored at different scales.

In this paper we present existing case studies to prevent, reduce, or adapt to soil salinity at the farm level, identifying their sustainability and innovation potential. The reviewed case studies show the prevention of soil salinity and sodicity by leaching, scheduled irrigation to avoid the rise of groundwater table, and cycling irrigation for allowing the use of brackish waters, where freshwater is a scarce resource. The remediation of sodicity by making calcium available for exchange with the sodium in the soil’s exchange complex, either by the use of chemical amendments such as gypsum or phytoremediation and bioremediation, in which plant growth increases CO2 in the root zone, leading to the dissolution of calcite, a process that can be further enhanced by the activity of microorganisms. Finally, adaptation cases are presented involving agronomical practices, such as plant selection, crop rotation, nutrient management and microbial management, as well as cases where the land-use changes were the chosen option for maintaining the soil’s health and its vital functions.

The reviewed cases show the successful application of innovative practices, but also point out the need for further research and innovation projects to counter salt-affected soils, particularly in the fields of irrigation and crop management, phyto and bioremediation, and microbial ecology of saline soils.

  • Open access
  • 65 Reads
Spatial prediction of the properties of chernozem soils on a field scale using machine learning methods based on data from Landsat 8 OLI and Sentinel 2 images for precision farming
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Remote sensing and machine learning methods are gaining popularity in studies of the spatial distribution of soil indicators. The use of approaches based on these methods improves the accuracy of digital maps of soil properties. Using the example of a field with developed erosion located in the chernozem zone of the Republic of Tatarstan (Russia), we studied the use of remote sensing and machine learning to obtain, on a scale of one field, digital maps of the organic carbon content, available forms of nitrogen, phosphorus and potassium, silt and clay fractions for precision farming purposes. Spectral parameters of bare soil obtained from the Landsat 8 OLI and Sentinel 2 satellites were used as predictors. Linear models (MLR), support vector regression (SVM) and random forest (RF) were used as models. Model performance was assessed based on RMSE, MAE and R2 after bootstrap. It is shown that the SVM and RF models outperform the MLR models. The best were the RF models for organic carbon (R2 = 0.91), available nitrogen (R2 = 0.83), potassium (R2 = 0.81), and clay (R2 = 0.67). SVM models were more accurate for available phosphorus (R2 = 0.91) and silt content (R2 = 0.93).

This work was supported in part by the Russian Foundation for Basic Research, research project № 19-29-05061-mk

  • Open access
  • 94 Reads
Influence of plant part and age on phytochemical constituents of Monkey Kola (Cola millenii K. Schum.); an important agroforestry species
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The current available economic tree species in natural and urban forests are rapidly decreasing at the rate that needs urgent attention. This is mostly occurring because many natural plant potentials are yet to be discovered while food insecurity is heightening daily in many developing countries. Cola millenii K. Schum. is an important agroforestry plant which has been utilized in traditional medicines for various sickness remedies in different parts of Nigeria. Often time, parts such as leaves, barks and fruit components are utilized as a conglomerate for the treatment of diseases without the adequate knowledge of their phytochemical concentration, which is a measure of the medicinal efficacy. Plant growth stage has been reported to affect the phytochemical component in some medicinal plants, however, such information is scarce for C. millenii. This study, therefore, evaluated the phytochemical constituents of Cola millenii to provide the information required for its utilization and sustainability.

Samples were collected from different parts of mother and young C. millenii found in the University of Ibadan, Nigeria. Plant samples were analyzed for saponin, flavonoid, tannin, alkaloid, anthraquinone, terpenoid and steroid following a standard method. Data were subjected to descriptive statistics, t-test and analysis of variance (ANOVA).

Results show that age and plant part significantly (p<0.05) influenced the presence of some analyzed phytochemicals. Flavonoid was the most concentrated phytochemical in the fruit of C. millenii with the highest value in epicarp (1.54 mg/100kg). None of the phytochemicals was found in the leaves of the plant.

Plant parts and age play important role in the concentration of phytochemicals in C. Millenii. Therefore, with the multipurpose benefits derived from C. millenii, incorporating it in agroforestry systems, where there will be limited deforestation by the farmers as tree component would be an alternative way to conserve it for posterity purpose.

  • Open access
  • 71 Reads
Innovation with lagoon sediments for soil conservation and sustainable intensification in the Ecuadorian Andes.

Agricultural production outlines the constant antagonism between the quest to achieve the highest yields and the need to preserve the physical / chemical properties of soils. The constantly increasing global demand for food prompts producers to apply more agrochemicals to increase their production; generating soil degradation, which is a costly and complex problem to repair. On this basis, the following objectives: a) evaluate the effectiveness of lagoon sediments in soil recovery, b) analyze the effect of sediment on the yield of the coriander crop, c) determine soil reclamation costs. The experiment was developed in the province of Imbabura, located in the north of Ecuador, had a surface area per plot of 3 m2 and used a completely randomized block experimental design. Four doses of sediment were applied mixed with the soil. The benefits of the use of lagoon sediments are evidenced in the nutritional quality of the soil after its application, determined by the physical and chemical analysis that reveals an increase of 3.9 ppm of the initial N, even after vegetative consumption, as well as a best C.E. of 0.85 mS/cm that promote a higher crop yield compared to the control treatment, becoming an innovative alternative for soil recovery, allowing to reconcile the intensive agriculture with soil conservation.

  • Open access
  • 73 Reads
The concept of accountability through good practices in agricultural production farms

This paper presents an analysis on the application of a new concept in agricultural production farms of responsibility in relation to the environment. The global demand for consumption and the dynamics of development have led to multiple debates on natural resources, these topics being a real concern in the case of agricultural production affected by climate change. The development of a more responsible conceptual framework in agricultural systems meant to mitigate the impact of undesirable results can be an element of responsibility as a stage in the evolution of a sustainable production farm. The relevance of this study lies in the interdependence of the application of good practice models in soil treatment to reduce greenhouse gas emissions alternatively with maintaining agricultural productivity in development regions at the national level. The analysis will represent a source of important information and data in compiling important statistical data at the level of development regions. Risk management in the case of soil treatment at the level of small and large farms should in our opinion confirm the same standard, the integration in the local rural environment presents the same risks of pollution or degradation. This study aims to further investigate the field of sustainable agricultural production models in developing regions, researching the integration of new concepts of responsibility in agricultural systems in terms of improving soil performance.