Global Navigation Satellite Systems (GNSS) allow the determination of the 3D position of a point on the Earth’s surface by measuring the distance from the receiver antenna to the orbital position of at least four satellites. Selecting and buying a GNSS receiver, depending on farm needs, is the first step for implementing precision agriculture. The aim of this work is to compare the positioning accuracy of four GNSS receivers, different for technical features and working modes: L1/L2 frequency survey-grade Real-Time Kinematic (RTK)-capable Stonex S7-G (S7); L1 frequency RTK-capable Stonex S5 (S5); L1 frequency Thales MobileMapper Pro (TMMP); low-cost L1 frequency Quanum GPS Logger V2 (QLV2). In order to evaluate the positioning accuracy of these receivers, i.e., the distance of the determined points from a reference trajectory, different tests, distinguished by the use or not of Real-Time Kinematic (RTK) differential correction data and/or an external antenna, were carried out. The results show that all satellite receivers tested carried out with the external antenna had an improvement in positioning accuracy. The Thales MobileMapper Pro satellite receiver showed the worst positioning accuracy. The low-cost Quanum GPS Logger V2 receiver surprisingly showed an average positioning error of only 0.550 m. The positioning accuracy of the above-mentioned receiver was slightly worse than that obtained using Stonex S7-G without the external antenna and differential correction (maximum positioning error 0.749 m). However, this accuracy was even better than that recorded using Stonex S5 without differential correction, both with and without the external antenna (average positioning error of 0.962 m and 1.368 m).

The traffic of agricultural machines can cause soil compaction and high variability of soil structure, both along normal lines and along those parallel to the field plane. The aim of this work was to investigate the potential of an electronic penetrometer, a GPS, a GIS and geostatistical techniques for mapping soil compaction.In July 2003 soil cone penetrometer resistance was measured using a semi-automatic electronic penetrometer in a sandy-silt soil (Vertic Xerochrept) of inland Sicily where a three-year rotation wheat (Triticum durum Desf.)-wheat-tomato (Solanum lycopersicum L.) was practiced. The measurements were carried out along three parallel 3-m long transects, from the soil surface to a depth of 0.70 m.A multivariate geostatistical approach, including exploratory analysis, variography, stochastic simulation and post-processing of simulations, was applied to produce thematic maps of penetrometer resistance and probability exceeding a critical value, in correspondence of a different number of tractor passes. Penetrometer resistance variation resulted erratic at the surface but showed high spatial correlation between data measured at different depths. The probabilistic maps of compaction risk showed that the soil volume, exceeding the penetrometer resistance of 2.5 MPa, critical for root growth, at the probability level of p N 0.40 increased from 20% to 40% after five tractor passes.

Using the conventional farming system, durum wheat requires high rates of herbicide spraying. Herbicide residues can cause pollution of soil and ground water and, therefore, of the entire environment.In order to minimise the environmental impact of herbicides, a home-made system for spatially variable rate crop input application was designed and developed. This system consists of a differential global positioning system (DGPS), a portable computer, specifically developed software and a device for applying rates proportionally related to the machine forward speed.Tests of spatially variable rate herbicide application were carried out in inland Sicily, on a field of 8.4 ha (where a 3-yr crop rotation of broad bean/vetch, durum wheat and durum wheat was practised), using a sprayer modified for applying variable rates and equipped with the above-mentioned system.The results are promising. The spatially variable rate herbicide application allowed an almost even grain yield over the entire field and a saving of 29% of herbicides with respect to the amounts normally used with the conventional farming system.

Human exposure to mechanical vibration may represent a significant risk factor for exposed workers in the agricultural sector. Also, noise in agriculture is one of the risk factors to be taken into account in the evaluation of workers’ health and safety. One of the major sources of discomfort for the workers operating a tractors is the noise to which they are exposed during work. The aim of this study was to evaluate the risk of exposure to whole-body vibration for the operator driving track-laying tractors in vineyard orchard and the noise level. The experimental tests were performed with six different track-laying tractors coupled with the same rototilling machine. The results showed that the vibration values of track-laying tractors coupled to rototilling machine, referred to the 8-hour working day, were always higher than 0.5 m s-2, the daily exposure action value established by Directive 2002/44/EC of the European Parliament. The daily noise exposure levels always exceeded the exposure limit value of 87 dB(A) established by Directive 2003/10/EC of the European Parliament. The ANOVA repeated measures model showed that the factor ‘site’, namely, the soil characteristics, did not influence the vibration level on the X and Y-axes of the tractors measured, regardless of their age. In the Z-axis, the vibration level was enhanced as the soil structure increased. As tractor age increased, the influence of soil characteristics was less important. In term of the age of the tractor and the number of hours worked, it was possible to identify three risk classes, which were up to 3,000 hours worked and offered a low risk; from 3,000 – 6,000 hours worked with a medium risk, and over 6,000 hours with a high risk level

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