Spanish Journal of Agricultural Research

Commercial maps of the main Latin American countries in the international olive oil market

Willmer GUEVARA-RAMÍREZ — 2023-01-26

Aim of study: World trade in olive oil is undergoing structural changes, with the emergence of new relevant actors, notably South American countries. The objective of this study was to analyze the performance of emerging Latin American countries in the world olive oil market during the period 2010–2019.

Area of study: Major Latin American countries within an international context.

Material and methods: The study was conducted through an analysis of trade networks, the application of the export growth decomposition method, the index of import dependence, and competitiveness matrices developed from the statistical evolution of import share and market share indicators.

Main results: European countries continue to dominate international trade in olive oil, however, Chile and Argentina have managed to widen their role. Chile was the country with the highest growth rate in olive oil exports in terms of value and volume in the period analyzed, whereas Argentina was below the world average. Prices in general have been stagnant, although price variability between countries can be distinguished. This may be due to the re-export policy of some countries, the qualities, the format, and some intrinsic characteristics of the markets.

Research highlights: Chile and Argentina figure prominently for their commercial capacity, with the former focusing mainly on the USA and Brazilian markets, and the latter on the Spanish.

Sustainability labels in the Spanish coffee market: A hedonic price approach

Nesrine MERBAH — 2023-02-09

Aim of study: Focused on the coffee sector, the purpose of this paper was to determine the implicit price paid for the main sustainability certifications (Fairtrade, Organic, Rainforest Alliance and UTZ certifications) using the hedonic price approach.

Area of study: Spain.

Material and methods: The total sample included 645 coffees. The characteristics were collected between the months of September and October 2021 from coffee packs sold in the main five supermarkets of retail chains in Spain. A log-log price/attribute function was used to estimate the hedonic price function.

Main results: The attributes UTZ certification, origin, and coffee intensity received significant positive effects leading to higher premium prices of 28.51%, 25.50% and 26.50%, respectively. In contrast, Fairtrade certifications had a negative impact on the average price of coffee.

Research highlights: The proposed model could be considered as a first approximation of a hedonic pricing model estimation for sustainable coffee in Spain. The results provide useful information for the coffee sector in developing effective marketing strategies that support the sustainability of food.

Pistachio nut diffusion in Spain: Growth models

Francisco CÁRDENAS-POLONIO — 2023-02-15

Aim of study: To analyse the diffusion of the crop by producing forecast models, that intend to help farmers in their decision-making.

Area of study: Spain. The area dedicated to pistachio cultivation in Spain has multiplied by 36 in the period 2010 to 2020, reaching 44,244 ha.

Material and methods: This study brings together data on the evolution of pistachio cultivation based on the following parameters: cultivated area, yield, and price. Methods are based on internal, external influence models and on an influence-price-crop yield pattern.

Main results: The results indicate that given a constant crop yield, raising pistachio prices, will bring a production increase that generate the saturation level of the system. Similarly, with a constant pistachio price and an increment of the crop yield, the saturation level of the system increases. Regarding the pattern of influence, it is shown that in a context of suitable market prices for pistachio and an optimal synergy of the production factors that favour the crop yield not only increases the level of saturation of the system but also the duration of the diffusion process.

Research highlights: The diffusion curve is sigmoidal with a well-defined inflection point and three well-defined phases. The adoption of pistachio in Spain responds to a model of internal influence (logistic) and never to models of external influence. According to the results, the process has a zero-innovation effect, while the dynamics of the process is completely determined by an imitation effect.

A hydroponic greenhouse fuzzy control system: design, development and optimization using the genetic algorithm

Hamid KHAFAJEH — 2023-02-23

Aim of study: The design and development of a hydroponic greenhouse fuzzy control system.

Area of study: The evaluation was performed using experimental data obtained from the literature. The construction and evaluation of the fuzzy control hydroponic greenhouse system was carried out in a greenhouse in Tehran, Iran.

Material and methods: The greenhouse environmental conditions, including temperature, humidity, and carbon dioxide, were controlled. The design of a fuzzy controller begun with the selection of linguistic variables, process status, and input and output variables. The fuzzy control system consisted of three modules: 1) fuzzy module, 2) cost function, and 3) genetic algorithm for the adjustment of the greenhouse environmental conditions.The next step was to select a set of linguistic rules and the type of fuzzy inference process. The rules were set once, and the fuzzy set and output value needed to be specified after the inference, along with the development of a non-fuzzy strategy.

Main results: The mean temperatures provided by the fuzzy control system during the day and night were 34.25°C and 23.22°C, respectively, which were improved to 31.17°C and 21.96°C after optimization. The mean humidity was 39.4% and 56.5% during the day and the night, respectively, which turned 60.22% and 74.59% after optimization. The control system also achieved desirable conditions in terms of CO₂ amount.

Research highlights: The results showed that the measured values of temperature and relative humidity of the greenhouse were improved after optimization with genetic algorithm.

Innovations in designing microwave electro-technological units with hybrid chambers

Midhat TUHVATULLIN — 2023-02-23

Aim of study: Microwave (MW) electro-technological units based on electromagnetic radiation of ultrahigh-frequency can involve thermal MW modification of dielectrics and non-thermal MW modification of polymers.

Area of study: Russian Federation.

Material and methods: The paper considers a method for making a unit with a hybrid chamber, where thermal and non-thermal MW modifications were carried out simultaneously, and the remaining energy after non-thermal MW modification of polymers was used for heating the dielectric.

Main results: A microwave electro-technological unit with a hybrid chamber replaced two separate devices that implemented these MW modifications. It was cheaper and required one MW generator. The unit took up less space than two separate apparatuses, and upgraded the existing microwave dryer to perform thermal MW modification of a lumber pile and non-thermal MW modification of polymer materials. The existing microwave dryer was redeveloped by solving the boundary value problem in electrodynamics and heat and mass transfer.

Research highlights: The research presents a microwave electro-technological unit with a hybrid chamber, combining thermal and non-thermal MW modifications of dielectric and polymer materials. As a result of upgrading the existing microwave dryer, it was possible to carry out both thermal and non-thermal MW modifications, namely, microwave drying of timber and microwave drying of up to seven different polymer objects.

Development of a laboratory setup simulating cabbage harvesting mechanism and optimization of torque requirement for harvesting cabbage

Pranay SARKAR — 2023-02-27

Aim of study: To develop a new type of cabbage (Brassica oleracea L.) harvesting mechanism in the laboratory that can be used in small-scale cabbage harvester in Indian conditions with minimum power requirement.

Area of study: Indian Institute of Technology, Kharagpur, India

Material and methods: The mechanism consisted of a cutting unit, a pushing unit and a conveying unit. Two counter-rotating disc cutters were used as cutting devices. Cutting speed, forward speed and cutting position were considered as influential parameters for torque required to carry out the harvesting of cabbage. A full factorial design was followed for the experiment and response surface methodology was used to optimize these parameters for minimizing torque requirement for cutting and pushing the cabbage.

Main results Torque decreased when cutting speed increased and when cutting height from the cabbage head decreased. Statistical analysis showed that cutting speed and cutting position affected the total torque significantly. The optimized cutting speed, forward speed and cutting position were found as 590 rpm, 0.25 m s^-1 and 0 cm, respectively with a desirability of 0.995. A regression model was developed to predict the total torque for cutting the cabbage stem and it was validated against 10 datasets with a percentage of bias within 10%.

Research highlights: The mechanism developed for cabbage harvesting could successfully cut and lift the cabbage heads in the laboratory. These optimized parameters are to be followed in the field prototype cabbage harvester for its successful operation in the field.

The effect of corn grain micronization on diet digestibility and blood biochemical parameters in weaned Holstein calves

Bojan STOJANOVIC — 2023-01-24

Aim of study: To evaluate corn grain micronization for calves fed a grower diet.

Area of study: Padinska Skela – Belgrade, Serbia.

Material and methods: Thirty weaned Holstein dairy calves (65–74 days of age) were randomly assigned to one of two treatments with growers containing micronized (MCG) or untreated corn grain (UCG). The experimental period lasted for 60 days.

Main results: The values of total tract apparent digestibility of dry matter (DM), organic matter (OM), crude protein (CP), and nonfiber carbohydrates (NFC) were higher for calves fed MCG versus those within the UCG treatment by 3.9% (p<0.05), 7.0% (p<0.01), 7.1% (p<0.01) and 7.5% (p<0.05), respectively, for the days 25–30 of the experimental period. In addition, the values of digestibility of OM, CP, and NFC were higher by 4.9% (p<0.05), 5.7% (p<0.05), and 6.0% (p<0.05), respectively, for the days 55–60 of the experimental period. The density of metabolizable energy, net energy for maintenance and gain in consumed dietary DM was higher (p<0.001) by 4.7, 5.5, and 7.2%, respectively for calves fed on the grower containing micronized corn grain (MCG), during the first digestibility period, and by 3.0, 3.6, and 4.6%, respectively, during the second digestibility period. Energy intake was lower (p<0.05) during the second digestibility period, for calves fed a diet with micronized corn. Blood urea N was affected (p<0.001) by dietary treatments. Lower values (10.2%) were observed for calves fed the grower containing MCG.

Research highlights: The micronization of corn grain is a useful tool for optimizing weaned calf production due to the improvement in the digestibility and energy content of the ration.

Performance and meat quality characteristics of male quails (Coturnix coturnix japonica) fed diets supplemented with pomegranate seed oil

Ainhoa SARMIENTO-GARCÍA — 2023-01-27

Aim of study: Pomegranate seed oil (PSO) is a nutritive, antioxidant-rich by-product, and it has been tested as a feed ingredient for livestock. However, studies on quails are scarce. The current study investigated that the effect of PSO on the performance and meat instrumental quality of quails.

Area of study: Türkiye.

Material and methods: A total of 60 seventy-day-old male quails were equally subjected to 3 dietary treatments consisting of 20 birds (5 replicates with 4 birds each). The quails were fed a diet supplemented with 0, 100, and 200 mg kg^-1 pomegranate seed oil (PSO). After 10 weeks, two birds per subgroup were randomly selected and slaughtered.

Main results: Supplementation of PSO reduced (p<0.05) feed intake and body weight gain linearly. However, there was no significant effect of PSO on carcass traits. For color parameters, the L* and b* values of breast and thigh meat increased with the addition of PSO to the diet (p<0.05). Cooking losses were highest in the thigh of quails fed 200 mg kg^-1 PSO. On the other hand, in the breast, the lowest values for this parameter were observed in the groups that had received 100 mg kg^-1 of PSO.

Research highlights: Including 100 mg kg^-1 of PSO can improve some meat quality characteristics without affecting performance parameters. There is a possibility that meat quality could be negatively affected by values higher than this. Nevertheless, further research is needed to determine the optimal dose of PSO to improve quail meat quality and its performance.

Prediction of growth performance parameters in the growing and free-range finishing phases of the Iberian pig via meta-analysis

Fernando SÁNCHEZ-ESQUILICHE — 2023-02-16

Aim of study: To describe and predict mathematically the growth parameters of Iberian pigs.

Area of study: Iberian dehesa agroforestry system. Southwest of Iberian Peninsula.

Material and methods: A quantitative and systematic review was carried out to find all studies with valid data of growth and finishing in the Iberian swine breed published up to May 2020. For the analysis of the data, a mathematical fitting model was obtained and a function was postulated to describe the relation between the variables age and body weight.

Main results: 112 publications were found, and after applying several quality filters, 18 with age and weight matched data were used. The database was composed of 76 different tests and 22,558 animals. The clasical growth phases were independently evaluated for data analysis.It was necessary to separate the finishing trials into three groups according to the starting age. Seven mathematical models were obtained for lactation,post-weaning, and montanera finishing. However, no valid test data were found during the growth and prefinishing phases. Besides that, a single model was obtained combining lactation and post-weaning, and another surface model including the variables age and weight to compare average daily weight gain in montanera finishing phase.

Research highlights: After systematic review of the studies that provide information on the growth of Iberian pigs, and a quantitative analysis, some mathematical linear and nonlinear models have been developed for the prediction of the production ratios at different phases.

Use of multivariate analysis and machine learning methods to characterize traits contributing to wheat yield diversity

Ali BEHPOURI — 2023-02-01

Aim of study: Regarding the third largest staple food crop in the world, determining the factors affecting wheat yield is of great importance. This study aimed to determine useful subsets of agronomic traits and evaluate the order of importance of traits in grain yield.

Area of study: Fars province, Iran.

Material and methods: In total, the data corresponding to 22 agronomic traits was collected from six different regions (Darab, Kavar, Marvdasht, Fasa, Lar, and Khonj) of 90 farms of Fars province, Iran as the most important wheat-growing regions. Multivariate statistical analysis (correlation, stepwise regression, and principal component analysis (PCA)) and machine learning modeling approaches, such as partial least squares regression (PLSR) and support vector regression (SVR) models, were applied to agronomic traits.

Main results: The findings, based on integrated approaches such as correlation, stepwise regression, and PCA, highlighted that number of spikes m^-2, grain number spike^-1, and thousand-grain weight had a major impact on the yield followed by awn length, spike length, narrow leaf herbicide, broadleaf herbicide, time to plant maturity (month), and soil salinity. Besides, PLSR with nine inputs (nine selected traits) displayed better prediction capability (R²=85 %, RMSE=0.32, MSE=0.10, and BIAS=-0.05) than that with all twenty-two input traits.

Research highlights: Integrated multivariate statistical analyses and machine learning regression methods could be a powerful tool in determining traits that have a significant impact on yield. These achievements can be considered for future breeding programs.

Methodology of stem water potential measurement on hedgerow olive orchards

Antonio HUESO — 2023-02-22

Aim of study:To evaluate the effect of leaf covering, leaf position, leaf age, time and sample size in measurements of stem water potential (Ψstem) in olive hedgerow orchards.

Area of study: The experimental orchards were located in the Centre of Spain (Toledo)

Material and methods: Midday Ψstem was measured using a pressure chamber in two super-intensive olive hedgerow orchards subjected to various water status.

Main results: Measurements were taken at solar noon on shaded leaves at mid canopy height following at least 1 hour of covering. Such measurements on 5 trees were sufficient to define the water status of individual homogeneous irrigation blocks. This combination of techniques is essential for repeatable measurements of Ψstem required to establish critical irrigation points and manage deficit irrigation strategies seeking to control vegetative growth and reduce water use with minimal effect on oil yield in olive hedgerow orchards and maximum oil quality. Part of our results weren’t previously reported: 1) Covering leaves with aluminium doesn’t completely stop transpiration and leaves must be covered and located in the shaded part of the canopy. 2) Ψstem depends on leaf height on olive hedgerow. 3) Ψstem of young leaves was less variable than in older ones. 4) Ψstem at solar noon presented larger differences with previous hours than later.

Research highlights: Leaves for measurements of stem water potential must be previously covered and located in the middle height of the shaded part of the canopy.