Shakib Shahidian

Hargreaves and Other Reduced-Set Methods for Calculating Evapotranspiration

Globally, irrigation is the main user of fresh water, and with the growing scarcity of this essential natural resource, it is becoming increasingly important to maximize efficiency of water usage. This implies proper management of irrigation and control of application depths in order to apply water effectively according to crop needs. Daily calculation of the Reference Potential Evapotranspiration (ETo) is an important tool in determining the water needs of different crops. The United Nations Food and Agriculture Organization (FAO) has adopted the Penman-Monteith method as a global standard for estimating ETo from four meteorological data (temperature, wind speed, radiation and relative humidity), with details presented in the Irrigation and Drainage Paper no. 56 (Allen et al., 1998), referred to hereafter as PM:

Spatial and Temporal Patterns of Apparent Electrical Conductivity: DUALEM vs. Veris Sensors for Monitoring Soil Properties

The main objective of this study was to compare two apparent soil electrical conductivity (ECa) sensors (Veris 2000 XA and DUALEM 1S) for mapping variability of soil properties in a Mediterranean shallow soil. This study also aims at studying the effect of soil cover vegetation on the ECa measurement by the two types of sensors. The study was based on two surveys carried out under two very different situations: in February of 2012, with low soil moisture content (SMC) and with high and differentiated vegetation development (non grazed pasture), and in February of 2013, with high SMC and with short and relatively homogeneous vegetation development (grazed pasture). The greater temporal stability of Veris sensor, despite the wide variation in the SMC and vegetation ground cover indicates the suitability of using this sensor for monitoring soil properties in permanent pastures. The survey carried out with the DUALEM sensor in 2012 might have been affected by the presence of a 0.20 m vegetation layer at the soil surface, masking the soil properties. These differences should be considered in the selection of ECa sensing systems for a particular application.

Calibration of GrassMaster II to estimate green and dry matter yield in Mediterranean pastures: effect of pasture moisture content

Abstract. Accurate assessment of standing pasture biomass in livestock production systems is a major factor for improving feed planning. Several tools are available to achieve this, including the GrassMaster II capacitance meter. This tool relies on an electrical signal, which is modified by the surrounding pasture. There is limited knowledge on how this capacitance meter performs in Mediterranean pastures. Therefore, we evaluated the GrassMaster II under Mediterranean conditions to determine (i) the effect of pasture moisture content (PMC) on the meter’s ability to estimate pasture green matter (GM) and dry matter (DM) yields, and (ii) the spatial variability and temporal stability of corrected meter readings (CMR) and DM in a bio-diverse pasture. Field tests were carried out with typical pastures of the southern region of Portugal (grasses, legumes, mixture and volunteer annual species) and at different phenological stages (and different PMC). There were significant positive linear relations between CMR and GM (r2 = 0.60, P < 0.01) and CMR and DM (r2 = 0.35, P < 0.05) for all locations (n = 347). Weak relationships were found for PMC (%) v. slope and coefficient of determination for both GM and DM. A significant linear relation existed for CMR v. GM and DM for PMC >80% (r2 = 0.57, P < 0.01, RMSE = 2856.7 kg ha–1, CVRMSE = 17.1% to GM; and r2 = 0.51, P < 0.01, RMSE = 353.7 kg ha–1, CVRMSE = 14.3% to DM). Therefore, under the conditions of this current study there exists an optimum PMC (%) for estimating both GM and DM with the GrassMaster II. Repeated-measurements taken at the same location on different dates and conditions in a bio-diverse pasture showed similar and stable patterns between CMR and DM (r2 = 0.67, P < 0.01, RMSE = 136.1 kg ha–1, CVRMSE = 6.5%). The results indicate that the GrassMaster II in-situ technique could play a crucial role in assessing pasture mass to improve feed planning under Mediterranean conditions.

The importance of sports performance factors and training contents from the perspective of futsal coaches.

Abstract The aim of this study was to identify the importance assigned by futsal coaches with different education levels to the sports performance factors (technical, tactical, physical and psychological) and to the training contents. The sample was divided into three groups (novice: n=35, intermediate: n=42; and elite coaches: n=15) depending on the degree of specific education, coaching experience and the level of the teams trained. To achieve this goal, the coaches answered a questionnaire previously validated by specialists in sport sciences. The results showed significant differences between the novice and elite group in small-sided games, inferiority games, opposition and execution timing of the training and drill items. The analyses also showed significant differences between the novice and intermediate group in inferiority games and opposition of the training and drill items. Although, no differences were identified between groups for the remaining performance factors and training and drill items considered, the identified trends provide a baseline related to the knowledge that contributes to the development of expertise of futsal coaches.

Incidência e fatores de risco de lesões em jogadores de futsal portugueses

INTRODUCTION: The reduced number of studies published on the occurrence of injuries in futsal in Portugal motivated this study. OBJECTIVE: This study aimed to identify potential causes for injuries in this sport, which can be a reference for the designing of specific protocols for injury prevention. METHODS: The sample was composed of 411 Portuguese male and female futsal players, of diverse competitive levels. All the participants filled out a previously validated questionnaire, based on retrospective information. Statistical inference consisted of inferential analysis using the Kruskal-Wallis test and the Mann-Whitney test for nonparametric data (significance level of 5%). RESULTS: The results confirm the ankle sprain injury as the injury with the highest incidence (48.8% of total) in futsal. The injuries with recovery period between 8 and 28 days were the most frequent (52.7% of total). This study did not show gender or the position of the player on the field to cause significant differences on the frequency of the injuries, or on the type or anatomical region of the injury. However, there were significant differences between training and competition, with greater occurrence of sprains and contractures in the case of training and higher incidence of muscle tears and fractures in competition, with a longer recovery period resulting from injuries suffered during competition. Moroever, significant differences were found for the mechanism of injury, with higher incidence of bone or joint injuries, sprains and fractures as a result of contact with opponents and higher incidence of muscle or ligament injuries without contact with opponents. The results did not show any significant differences in the laterality of injuries. CONCLUSION: The results highlight the importance of specific programmes for ankle sprain injury prevention, specially in early stages, regardless of their position on the field of play, especially in situations of contact with opponents.

Monitoring pasture variability: optical OptRx® crop sensor versus Grassmaster II capacitance probe

Estimation of pasture productivity is an important step for the farmer in terms of planning animal stocking, organizing animal lots, and determining supplementary feeding needs throughout the year. The main objective of this work was to evaluate technologies which have potential for monitoring aspects related to spatial and temporal variability of pasture green and dry matter yield (respectively, GM and DM, in kg/ha) and support to decision making for the farmer. Two types of sensors were evaluated: an active optical sensor (“OptRx®,” which measures the NDVI, “Normalized Difference Vegetation Index”) and a capacitance probe (“GrassMaster II” which estimates plant mass). The results showed the potential of NDVI for monitoring the evolution of spatial and temporal patterns of vegetative growth of biodiverse pasture. Higher NDVI values were registered as pasture approached its greatest vegetative vigor, with a significant fall in the measured NDVI at the end of Spring, when the pasture began to dry due to the combination of higher temperatures and lower soil moisture content. This index was also effective for identifying different plant species (grasses/legumes) and variability in pasture yield. Furthermore, it was possible to develop calibration equations between the capacitance and the NDVI (R2 = 0.757; p < 0.01), between capacitance and GM (R2 = 0.799; p < 0.01), between capacitance and DM (R2 = 0.630; p < 0.01), between NDVI and GM (R2 = 0.745; p < 0.01), and between capacitance and DM (R2 = 0.524; p < 0.01). Finally, a direct relationship was obtained between NDVI and pasture moisture content (PMC, in %) and between capacitance and PMC (respectively, R2 = 0.615; p < 0.01 and R2 = 0.561; p < 0.01) in Alentejo dryland farming systems.

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.

Long-term effect of super phosphate fertilizer on accumulation of soil phosphorus on a pasture

The purpose of the present work was to clarify some aspects of the complexity of phosphorus (P) dynamics under specific soil and climate conditions and a particular type of agro ecosystem: the Mediterranean pasture. The deviation between measured and estimated soil P content was evaluated over 12 years, in a 6 ha permanent bio-diverse pasture field in Southern Portugal. A simple dynamic model found good agreement for estimating the soil P content where P fertilizer had been regularly applied, but was not nearly as effective for the period during which the field did not receive P fertilizer. The dynamic of transformation between diverse P pools in Mediterranean shallow soils make the estimation of P balance very complex and justify more experiments.

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.

Seasonal climate patterns and their influence on calibration of the Hargreaves-Samani equation

Abstract Annual patterns in climate parameters were studied to evaluate how these influence the quality of reference evapotranspiration (ETo) estimates obtained from the Hargreaves-Samani (HS) equation, since the method only uses the measured temperature directly. The work evaluates how these patterns can be used to improve the HS ETo estimates. Ten-year moving averages from a set of California Irrigation Management Information System (CIMIS) stations were used to evaluate the relationships between solar radiation (Rs), temperature (T) and ETo. The results indicate that T treads behind solar radiation and its value peaks some 25 days later. Thus, the main irrigation season in the Mediterranean climate (1 May–30 September) can be divided into three phases: increasing Rs and T; decreasing Rs with increasing T; and decreasing Rs and T. Non-univocal annual cycles were observed between Rs and T, ETo and Rs, and ETo and T. These annual patterns result in important seasonal changes in the ratio between the HS and Penman-Monteith (FAO PM) ETo estimates. The changes are particularly important during the irrigation season, where the FAO PM initially calculates greater ETo values than the HS methodology, and from the end of May to early September, where the HS equation overestimates the ETo values (by 17 mm, or 3%). These patterns obtained from 2000–2009 data were used to calibrate and improve HS ETo estimates at new sites for the 2010–2011 period. Calibration based on the proposed seasonal region-wide FAO PM/HS ETo ratios improved both the bias (decreased from 0.40 to 0.36 mm d-1) and r2 (increased from 0.67 to 0.87) of the ETo estimates for the irrigation season. The proposed methodology can be easily applied to other regions, even when the existing weather stations are sparse. Editor Z.W. Kundzewicz