Síntesis del análisis de La Profecía 83

The protocol for applying the traffic and tillage treatments was changed in 2015 from that used by the previous researcher due to equipment availability. The protocol described

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here is applicable to years 2015-2017 but differences applicable to the previous research is highlighted.

A Massey Ferguson 8480 tractor (Figure 3.6) was used for applying all the traffic and tillage treatments and drilling the crops each year. Total vehicle weight was 12.55 tonnes (weight distribution: front axle 5.55 tonnes, rear axle 7.00 tonnes) with a track width of 2.05 metres. Previous research had used the Massey Ferguson 8480 tractor to apply the additional compaction treatments (detailed in 3.5.1) but a Cat Challenger MT765C (Figure 3.7) tracked tractor was used to apply the tillage treatments and the crop drilling

operations (Smith, E., 2016). An investigation by Smith, E. (2016) found that the Cat Challenger MT765C produced consistently lower soil pressures compared to using MachXBib and AxioBib tyres and concluded that the use of Cat Challenger MT765C tracked vehicle would complement the low inflation pressure tyres. The Cat Challenger MT765C was not available to use for this research. The use of the tracked tractor before 2015 meant that the primary wheelways in all traffic treatment plots (CTF, LTP and STP) had benefitted from low ground pressure running gear (Smith et al., 2014). The use of the Massey Ferguson 8480 tractor to apply the tillage treatments and the crop drilling

operations from 2015 onwards would allow the standard inflation pressure to be used for all compaction applied to the STP to better represent a Random Traffic standard tyre pressure farming system. As Controlled Traffic Farming is a management strategy intended to minimise compaction of soil (Gasso et al., 2014) it was decided to leave the CTF plots with a low ground pressure treatment for the wheelways. This would enable comparisons to be made with the findings of the previous researcher and between

Controlled Traffic Farming low inflation tyre pressure and Random Traffic low inflation tyre pressure to measure the effect on soil properties and crop growth by controlling traffic. Similarly a comparison could be made between Random Traffic low inflation tyre pressure and Random Traffic standard inflation tyre pressure to measure differences due to tyre inflation pressure. The trial design would not allow the CTF plots to have both low inflation tyre pressure and standard tyre inflation pressure treatments which is recommended for future studies. The Massey Ferguson 8480 was fitted with Michelin Axiobib tyres (IF 650/85 R38 TL 179D, rear and IF 600/70 R30TL 159D, front). Tyre pressures were set to 1.2 bar front, 1.5 bar rear for STP plots and 0.7 bar front and rear for LTP and CTF plots. Prior to 2015 the tyres used were Michelin MachXbib tyres (600/70 R28 front and 650/85 R38 rear) with the same tyre pressures as used with the Axiobib tyres. (Smith et al., 2014). In 2015 the navigation of the tractor was provided by a Trimble FmX integrated display unit (Trimble, 2018a) connected to a Trimble EZ-Steer steering system (Trimble, 2018b). The EZ-Steer was replaced in autumn 2015 by an in-vehicle auto-steer system.

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Figure 3.6 - Massey Ferguson 8480 (216.3 kW [290 HP]; 12.5 tonne) tractor

Figure 3.7 - Caterpillar Challenger MT765C tractor

(Source adapted from: Misiewicz, unpublished, 2012)

3.4.1 Traffic treatments

Traffic treatments (compaction) were applied with the Massey Ferguson 8480 tractor. The number of vehicle passes applied and plot area covered simulated real farm traffic

systems (Smith et al., 2013; Smith, E., 2016) based on the findings of Kroulik et al. (2009) and were designed to represent the total area and intensity of field trafficking that could reasonably be expected on a field due to the operations of agricultural vehicles associated with cereal production in a growing season. The constraints of the trial plot sizes led to 30% of the CTF plots being wheeled. It is expected that a farm using a CTF system could reasonably expect a lower percentage wheeled area. Chamen (2015) reported that the usual maximum width for CTF systems is 12 metres, restricting soil wheeled area to 13%.

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The application of traffic treatments in the trial plots is shown diagrammatically at Figure 3.8. Table 3.1 shows the areas of traffic treatment per vehicle pass. The front and rear tractor tyre from one side of the tractor created each compaction treatment pass. The area of the random traffic plots (both standard and low inflation pressure) subjected to wheeling was 75% for deep, 60% for shallow and 45% for zero tillage plots. As the controlled traffic plots only had wheeling from the tillage and drilling applications and no extra traffic

treatments applied, the area wheeled was 30% of the plot.

Figure 3.8 - Trial plot compaction plan showing percentage area and widths of traffic treatments for the nine treatments plots.

Coloured strips represent traffic wheelings; central numbers the nominal tractor passes; letter P the primary wheelways

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Table 3.1 - Area of plot covered by traffic treatments (%)

STP and LTP CTF

Tillage/Passes 1 2 3 Total 1 2 3 Total

Deep 30 30 15 75 0 30 0 30

Shallow 30 30 0 60 0 30 0 30

Zero 15 30 0 45 0 30 0 30

The desired level of traffic treatment detailed by Figure 3.8 and Table 3.1 was achieved in two parts. Each treatment plot has a pair of 'primary' wheelways (indicated by the letter P in Figure 3.8 which received compaction from the tractor when carrying out tillage and drilling operations. This accounts for all the traffic treatment in the CTF plots (Table 3.1). In order to simulate the extra traffic due to random traffic farming expected in real world farming, extra traffic treatments were applied to the STP and LTP traffic plots using the protocol given in Appendix A. For winter crops this was carried out in the autumn after the previous harvest. The autumn traffic treatments were applied in August 2014 (previous researcher) for the 2015 crop and 20th August 2015. As a cover crop was drilled in autumn 2015 (Section 6.3.3) it was decided to add a smaller additional traffic treatment in Spring 2016 to simulate the extra operations likely to be associated with the establishment of a cover crop. The protocol used is given in Appendix A. In 2016 the crop rotation

dictated a move to spring crops and hence the compaction treatment was applied 28th March 2017. The estimated soil moisture (using the method in Section 3.9) at the time of the traffic and tillage treatments was 20th August 2015 (13%), 5th April 2016 (21%) and 28th March 2017 (21%) (National Rivers Flow Archive, 2019).

3.4.2 Cultivation equipment and settings

The deep and shallow tillage treatments were applied using a 4 m wide Väderstad Topdown, a high intensity multipurpose cultivator (Väderstad, Not dated a), pulled by the Massey Ferguson 8480 tractor along the primary wheel ways (Figure 3.9). A Caterpillar Challenger MT765C tractor was used prior to 2015. The tillage tines were set to 250 mm (deep tillage) and 100 mm (shallow tillage) depth on “spare 1” and “spare 2” plots

respectively. Implement depths were set using packers on the hydraulic rams and depth markers (Figure 3.10). Tillage depths were checked using a wooden rule pushed into the tine slots in the soil and the equipment settings were adjusted as necessary prior to carrying out the cultivation treatments. The 14 standard tines had 270 mm spacing and the front discs were set to 50 mm depth. The protocol used is given in Appendix A.

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Figure 3.9 - Väderstad 4 metre wide Topdown cultivator pulled by the Massey Ferguson 8480 tractor

Figure 3.10 - Implement depth settings on the Väderstad Topdown left: indicators and right: packers