J. N. Tullberg

Traffic and residue cover effects on infiltration

Wheel traffic can lead to compaction and degradation of soil physical properties. This study, as part of a study of controlled traffic farming, assessed the impact of compaction from wheel traffic on soil that had not been trafficked for 5 years. A tractor of 40 kN rear axle weight was used to apply traffic at varying wheelslip on a clay soil with varying residue cover to simulate effects of traffic typical of grain production operations in the northern Australian grain belt. A rainfall simulator was used to determine infiltration characteristics. Wheel traffic significantly reduced time to ponding, steady infiltration rate, and total infiltration compared with non-wheeled soil, with or without residue cover. Non-wheeled soil had 4-5 times greater steady infiltration rate than wheeled soil, irrespective of residue cover. Wheelslip greater than 10% further reduced steady infiltration rate and total infiltration compared with that measured for self-propulsion wheeling (3% wheelslip) under residue-protected conditions. Where there was no compaction from wheel traffic, residue cover had a greater effect on infiltration capacity, with steady infiltration rate increasing proportionally with residue cover (R-2 = 0.98). Residue cover, however, had much less effect on infiltration when wheeling was imposed. These results demonstrated that the infiltration rate for the non-wheeled soil under a controlled traffic zero-till system was similar to that of virgin soil. However, when the soil was wheeled by a medium tractor wheel, infiltration rate was reduced to that of long-term cropped soil. These results suggest that wheel traffic, rather than tillage and cropping, might be the major factor governing infiltration. The exclusion of wheel traffic under a controlled traffic farming system, combined with conservation tillage, provides a way to enhance the sustainability of cropping this soil for improved infiltration, increased plant-available water, and reduced runoff-driven soil erosion.

Tillage and traffic effects on runoff

Traffic and tillage effects on runoff and crop performance on a heavy clay soil were investigated over a period of 4 years. Tillage treatments and the cropping program were representative of broadacre grain production practice in northern Australia, and a split-plot design used to isolate traffic effects. Treatments subject to zero, minimum, and stubble mulch tillage each comprised pairs of 90-m 2 plots, from which runoff was recorded. A 3-m-wide controlled traffic system allowed one of each pair to be maintained as a non-wheeled plot, while the total surface area of the other received a single annual wheeling treatment from a working 100-kW tractor. Rainfall/runoff hydrographs demonstrate that wheeling produced a large and consistent increase in runoff, whereas tillage produced a smaller increase. Treatment effects were greater on dry soil, but were still maintained in large and intense rainfall events on wet soil. Mean annual runoff from wheeled plots was 63 mm (44%) greater than that from controlled traffic plots, whereas runoff from stubble mulch tillage plots was 38 mm (24%) greater than that from zero tillage plots. Traffic and tillage effects appeared to be cumulative, so the mean annual runoff from wheeled stubble mulch tilled plots, representing conventional cropping practice, was more than 100 mm greater than that from controlled traffic zero tilled plots, representing best practice. This increased infiltration was reflected in an increased yield of 16% compared with wheeled stubble mulch. Minimum tilled plots demonstrated a characteristic midway between that of zero and stubble mulch tillage. The results confirm that unnecessary energy dissipation in the soil during the traction process that normally accompanies tillage has a major negative effect on infiltration and crop productivity. Controlled traffic farming systems appear to be the only practicable solution to this problem.

Traffic and tillage effects on wheat production on the Loess Plateau of China: 1. Crop yield and SOM

Challenges for dryland farming on the Loess Plateau of China are continuous nutrient loss, low soil organic matter and crop yield, and soil degradation. Controlled traffic, combined with zero or minimum tillage and residue cover, has been proposed to improve soil structure and crop yield. From 1998 to 2006, we conducted a field experiment comparing soil organic matter and wheat productivity between controlled traffic and conventional tillage farming systems. The field experiment was conducted using 2 controlled traffic treatments (zero tillage with residue cover and no compaction, shallow tillage with residue cover and no compaction) and a conventional tillage treatment. Results showed that controlled traffic treatments significantly increased soil organic matter and microbial biomass in the 0–0.30 m soil profile. Controlled traffic with zero tillage significantly increased total N in the 0–0.05 m soil profile. The mean yield over 8 years of controlled traffic treatments was >10% greater than that of conventional tillage. Controlled traffic farming appears to be a solution to the cropping problems faced on the Loess Plateau of China.

Traffic and tillage effects on runoff and soil loss on the Loess Plateau of northern China

This paper reports the outcome of 5 years of field plot runoff monitoring, 2 years of water erosion measurement, and a rainfall simulation experiment on moderately sloping farmland on the loess plateau of north-west China. The objective was to test different conservation tillage systems compared with the control treatment, conventional mouldboard plough practice (CK). Tillage, residue cover, and compaction effects were assessed in terms of runoff and soil erosion. Results from the runoff plots showed that conservation tillage, with more residue cover, less compaction, and less soil disturbance, could substantially reduce runoff and soil erosion compared with the control. No tillage with residue cover and no compaction produced the least runoff and soil erosion. Compared with the control, it reduced runoff and soil erosion by about 40% and 80%, respectively. At the start of the experiment, residue cover appeared to be the most important factor affecting soil and water conservation, particularly when antecedent soil moisture was limited. With the accumulation of tractor wheeling effects over the course of the experiment, soil compaction appeared to become a more important factor affecting runoff. Rainfall simulation was then used to assess the effect of non-inverting surface tillage and different levels of residue cover and wheel compaction on infiltration and runoff. This confirmed that wheel compaction effects could be greater than those of tillage and residue cover, at least under the 82.5 mm/h rainfall rate produced by the simulator. The wheeling effect was particularly large when the treatment was applied to wet soil, and severe even after wheeling by small tractors.

Controlled Traffic Farming

The cycle of traffic-induced soil compaction and tillage is a major inefficiency of current mechanised agriculture, where random field traffic wastes energy, damages soil structure and imposes other negative consequences. Controlled traffic farming (CTF) restricts compaction to precise traffic lanes, where it improves wheel performance, allowing natural, uncompromised soil processes and productivity over most of the field. The principles and practices of controlled traffic in Australia, UK and the Netherlands are explained and an overview of worldwide CTF research is provided. Immediate benefits of CTF include reduced fossil energy use and improved field efficiency, with better infiltration and drainage reducing run-off and erosion. Indirect effects include timeliness benefits with more workable days, reduced waterlogging, denitrification and greenhouse gas emissions, and enhanced soil biological activity with improved organic matter levels. Equipment and system changes are necessary to achieve controlled traffic, but adoption reduces costs, increases yields and provides better financial and environmental performance.

Traffic and tillage effects on wheat production on the Loess Plateau of China: 2. Soil physical properties

Controlled traffic zero and minimum tillage management with residue cover has been proposed as a solution to erosion and other soil degradation challenges to the sustainability of dryland farming on the Loess Plateau of China. This was assessed between 1998 and 2007 in a field experiment involving a conventional tillage treatment, and 2 controlled traffic treatments, no tillage and shallow tillage, with full straw cover in both cases. This paper reports the soil physical properties after 9 years of dryland wheat production under these treatments, and the substantial improvements seen in soils under controlled traffic. Compared with conventional tillage, controlled traffic significantly reduced soil bulk density in the 0–0.15 m soil layer, and increased total porosity in the 0–0.60 m soil layer, where macroporosity (>60 µm) and mesoporosity (0.2–60 µm) increased at the expense of microporosity (<0.2 µm). Readily available water content and saturated hydraulic conductivity were greater in controlled traffic treatments. Controlled traffic farming appears to be an improvement on current farming systems on the Loess Plateau, and valuable for the sustainable development agriculture in this region.

Soil physical properties and infiltration after long‐term no‐tillage and ploughing on the Chinese Loess Plateau

Abstract Water is the most limiting factor for crop production in dryland farming. A better understanding of the long‐term impact of tillage and residue management systems on soil structure and water infiltration is necessary for the further development of conservation tillage practice to improve water use efficiency. The objectives of this study were to assess the influence of no‐till with residue retention (NT) and conventional (plough) tillage with residue removal (CT) on soil properties and soil water transmission characteristics in a winter wheat (Triticum aestivum) monoculture system in Shanxi, on the Chinese Loess Plateau. Soil physical parameter measurements were made in the top 30 cm depth in September 2007 after 16 years under the two tillage treatments. Compared with CT treatment, NT significantly (P < 0.05) reduced soil bulk density (7.1%) in the 20–30 cm soil layer, and increased macroporosity (>60 μm, 17.0%) and saturated hydraulic conductivity (249%) in the 15–30 cm soil layer. There were no significant differences in these soil physical properties between tillage systems in the 0–15 cm layer. In addition, plant available water and water infiltration rate were greater in the NT treatment. The improved soil quality parameters and water infiltration from this long‐term experiment indicate that no‐tillage with residue retention is a promising farming system for the dryland farming areas of northern China.

Potential to increase productivity and sustainability in Argentinean agriculture with controlled traffic farming: a short discussion

Abstract Drivers for and potential barriers against adoption of controlled traffic farming (CTF) systems in Argentina are reviewed. Traffic compaction is one of the main factors affecting crop productivity within Argentinean agriculture, and has significant although less quantified impacts on the whole-of-farm system. This suggests that the benefits of no-tillage (NT), which represents the dominant form of cropping in Argentina, are not fully realised. Conservative estimates indicate that crop yields could be improved by at least 15% if NT is used in conjunction with CTF. Cost-benefit analyses of available options for compaction management are required. Despite this, and based on reported evidence internationally, a shift toward increased uptake of CTF within Argentinean agriculture is likely to: (1) improve productivity and farm profitability, (2) enhance environmental performance, and (3) maintain competitiveness of the agricultural sector. Appropriate technical advice and support is a key requirement to drive adoption of CTF. Therefore, the adoption process will benefit from collaboration developed with well-established research and extension organisations in Australia and the United Kingdom, and active engagement of machinery manufacturers.

Agronomic performance of wheat (Triticum aestivum L.) and fertiliser use efficiency as affected by controlled and non-controlled traffic of farm machinery

Controlled traffic farming (CTF) is a mechanization system that confines all load-bearing wheels to permanent traffic lanes, thus optimizing productivity of non-compacted crop beds for given energy, fertilizer and water inputs. This study investigated the agronomic and economic performance of winter wheat (Triticum aestivum L.) grown in compacted and non-compacted soils to represent the conditions of non-CTF and CTF systems, respectively. Yield-to-nitrogen (N) responses were obtained by applying urea (46% N), urea treated with 3,4-dimethyl pyrazole phosphate (DMPP), commercially known as ENTEC® urea (46% N), and urea ammonium nitrate (solution, 30%N) at rates between 0 (control) and 300 kg ha-1 N at regular increments of 100 kg ha-1 N. The results showed that the CTF system increased grain yield, total aboveground biomass, and harvest index by 12%, 9%, and 4%, respectively compared to the crop grown under the non-CTF system (P<0.05). Overall, the agronomic efficiency was approximately 35% higher in CTF compared with non-CTF (≈4 vs. 3 kg kg-1, respectively). Nitrogen use efficiency (NUE) was approximately 50% higher in CTF compared with non-CTF; however, there was not fertilizer type effect on NUE. On average, the optimal economic nitrogen application rates and corresponding grain yields were 122 kg ha-1 and 3337 kg ha-1, and 175 and 3150 kg ha-1 in the CTF and non-CTF systems, respectively. This work demonstrated that significant improvements in fertilizer-N recoveries may not be realized with enhanced nitrogen formulations alone and that avoidance of (random) traffic compaction is a pre-requisite for improved fertilizer use efficiency.