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Quantitative knowledge of the factors and interactions affecting yield is essential for site-specific crop management. One of the factors that frequently affects yield is topography. The aims of this study were to compare elevation data obtained from a combine harvester yield monitor and a hand RTK-GPS, and to evaluate the relationships between the spatial variation of cereal yield, selected crop nutrient concentration and topographic attributes derived from the two sources of elevation data. Simple models of elevation, slope and flow accumulation were created from the data of an experimental field in the Czech Republic, and the relations between yield and soil nitrogen and organic carbon contents and topography were determined over a four-year period. The models of elevation, slope and flow accumulation were compared with the yield, and soil nitrogen and organic carbon contents during the growing seasons of 2004, 2005, 2006 and 2007 in relation to total precipitation and temperature. The relationship between yield and topographic attributes was evaluated with the help of geostatistical methods. The results of correlation analysis among the variables were evaluated statistically by forward stepwise linear regression. No significant differences between elevation data from the combine harvester yield monitor and RTK-GPS were found. There was a significant relation between yield and crop nutrient concentration with topography. The correlation coefficients between flow accumulation and yield were weak for the wetter years and strong for the drier years.

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Evaluation of new technologies using guidance systems is very important and can help producers with choosing the right equipment for their applications. Without using satellite navigation during field operations, there is a tendency for passes to overlap. That results in waste of fuel and pesticides, longer working times and also environmental damage. When utilising satellite guidance for field operations, there is a close connection with controlled traffic farming (CTF) as well. CTF is currently a quite quickly developing farming system based on fixed layout of machinery passes across a field. Tracks precisely set out for a machine's tyres in the field could be a tool for minimising soil compaction risk which is another threat to the environment. The purpose of this paper was to evaluate the accuracy of currently available guidance systems for agricultural machines. Real passto-pass errors (omissions and overlaps) in a field were measured. Consequently, comparison between observed guidance systems was made regarding final working accuracy. Further, intensity of machinery passes, percentage of wheeled area and repeated passes in fields were monitored. These measurements were made in fields under real operating conditions using a conventional tillage system with ploughing and also a conservation tillage system, both systems with randomly organized traffic. Finally, the same parameters were monitored in fields where fixed machinery tracks were used for all operations and passes but only under a conservation tillage system. Pass-to-pass accuracy was measured for the evaluation of different guidance systems. Size of missed areas or overlaps was evaluated statistically. Concerning intensity of machinery passes and total field area affected by machinery passes, the following facts were found out. The experiments with randomized traffic showed a significant difference of the parameters mentioned above between a conventional tillage system with ploughing and a conservation tillage system. Wheeled area was 86 and 64%, respectively which proves benefits of conservation tillage. The experiments with a fixed track system showed that the total run-over area by machinery tyres decreased even more (up to 31%) in comparison to randomized traffic in a field (only fields under conservation tillage system were monitored and evaluated).The following statements based on our results can be made. The navigation and therefore possibility for better accuracy of machinery passes in fields together with permanent machinery tracks utilization could help with soil condition improvement and also energy savings which would result from that. The CTF system will help with further development of a system for soil compaction protection which is currently a real necessity.

Brant V., Kroulík M., Pivec J., Zábranský P., Hakl J., Holec J., Kvíz Z., Procházka L. (2017): Splash erosion in maize crops under conservation management in combination with shallow strip-tillage before sowing. Soil & Water Res., 12: 106−116.Soil under maize cropping is among the most endangered by erosion. The effect of conservation tillage management on values of splash erosion when using shallow strip tillage before sowing maize was evaluated in the Central Bohemian region (Czech Republic) during the period 2010-2012. The following types of tillage management using conventional technology and shallow tillage were evaluated: ploughed plots with mulch formed by weed biomass (PL W ), ploughed plots with mulch from perennial ryegrass plants (PL PR ), ploughed plots without mulch (PL) and shallow tillage (ST) where the mulch was formed by cereals straw. Furthermore, values of the splash erosion, plants and plant residues coverage ratio of soil by image analysis and the stability of soil aggregates were monitored during the whole experiment. The average value of splash erosion (MSR) was higher by 18.7% in the variant of PL W , lower by 35.9% in PL PR , and lower by 39.5% in ST, than in the control treatment PL (MSR value for PL = 100%) for the whole evaluated period (2010)(2011)(2012). The average values of the soil surface plant coverage ratio in the plots with mulch ranged from 1.5 to 43.0% at the beginning of the vegetation period, and from 4.9 to 85.5% in the second half of the vegetation period. A positive correlation was observed between the average values of the stability of soil aggregates and the plant coverage ratio of the soil surface in 2010 and 2011.

Soil infiltration capacity is one of the key factors in the soil protection against unfavourable effects of water erosion. The purpose of its measuring was to compare and evaluate the changes of the soil physical properties and of water infiltration into soil caused by different intensity of soil cultivation at two individual sites. The ploughing (PL), shallow tillage (ST), and direct drilling (NT) effects on the soil physical properties, water infiltration into soil, and soil surface coverage with the crop residua under the soil condition loamy Haplic in soil. The variant with ploughing showed water saturation in the top layer, the variants with reduced tillage were characterised by vertical macropores and crack effects with the water drain into deeper layers. Ploughing proved its advantage for the short-term rainfall retention. Similar results were also brought in the evaluation on the plot with clay soil (Klapý). The loosening effect was evident during coloured water infiltration in the period of snow thawing. The loosed soil layer showed a significantly higher soil water holding capacity as compared with variants with reduced soil tillage. The result showed major differences in the water infiltration rate into soil and different characters of water infiltration into soil at different soil tillage.

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While the existing research provides a wealth of information about the static properties of RTK receivers, less is known about their dynamic properties, although it is clear that the vast majority of field operations take place when the machine is moving. A new method using a MRA for the evaluation of RTK receivers in movement with a precise circular reference trajectory (r = 3 m) was proposed. This reference method was developed with the greatest possible emphasis on the positional, time and repeatable accuracy of ground truth. Four phases of the measurement scenario (static, acceleration, uniform movement and deceleration) were used in order to compare four different types of RTK receiver horizontal operation accuracy over three measurement days. The worst result of one of the receivers was measured at SSR = 13.767% in dynamic movement. Since the same “low-cost” receiver without an INS unit had SSR = 98.14% in previous static measurements, so it can be assumed that the motion had a very significant effect on the dynamic properties of this receiver. On the other hand, the best “high-end” receiver with an INS unit had SSR = 96.938% during the dynamic testing scenarios. The median values of the deviations were always better during uniform movements than during acceleration or braking. In general, the positioning accuracy was worse in the dynamic mode than in the static one for all the receivers. Error indicators (RMSerr and Me) were found several times higher in the dynamic mode than in the static one. These facts should be considered in the future development of modern agricultural machinery and technology.