Controlled traffic farming effects on productivity of grain sorghum, rainfall and fertiliser nitrogen use efficiency

Controlled traffic farming (CTF) is a mechanisation system in which all machinery has the same (or modular) working and track width so that field traffic can be confined to the least possible area of permanent traffic lanes. CTF enables productivity of non-compacted crop beds to be optimised for given energy, fertiliser and water (rainfall) inputs. This study investigated the agronomic response and economic return of grain sorghum grown in compacted and non-compacted soils to represent the conditions of non-CTF and CTF systems, respectively. Yield-to-nitrogen (N) responses were derived following application of urea, 3,4-dimethyl pyrazole phosphate-treated urea (DMPP), and urea ammonium nitrate (UAN, 32% N) at rates between 0 and 300 kg ha−1 N. Selected soil properties were measured to guide parametrisation of the Agricultural Production Systems Simulator (APSIM), which was used to assess long-term (55 years) effects of CTF and non-CTF soil conditions on crop productivity, rainfall use efficiency (RUE) and develop rainfall-runoff relationships. Grain yield and yield components (harvest Index, grain thousand-grain weight, number of grains) were significantly higher in CTF compared with non-CTF. On average, the most economic N rates, and corresponding grain yields, were 144 and 3428 kg ha−1, and 100 and 1796 kg ha−1 for CTF and non-CTF, respectively. When N inputs were optimised, agronomic efficiency calculations showed 18% increase in CTF compared with non-CTF. Nitrogen use efficiency (NUE) was 1.75 times higher in CTF than in non-CTF. Rainfall-use efficiency was about 65% higher in CTF, which concurrently reduced the amount of runoff compared with non-CTF. Average rainfall season (330–450 mm in-crop) grain yield was 30% lower in non-CTF compared with CTF. For subtropical conditions of Australia, long-term APSIM simulations showed that increased productivity and inter-season yield stability can increase gross margin of grain sorghum by AUD74 ha−1 or greater depending on the adopted tillage system and in-crop rainfall. In non-CTF systems, improvements in NUE and RUE are constrained by soil compaction. Enhanced efficiency fertilisers, such as DMPP-treated urea, cannot compensate for other stresses caused by soil compaction and therefore cannot achieve the same NUE and RUE as the CTF system. Adoption of CTF delivers improved resource-use efficiency and profitability in rainfall-limited environments

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

Improved prediction of farm nitrous oxide emission through an understanding of the interaction among climate extremes, soil nitrogen dynamics and irrigation water

Reducing nitrous oxide (N2O) emissions from agriculture soils is crucial, as it accounts for 5.6-6.8% of global anthropogenic emissions. This study aims to understand the interaction among climate, soil nitrogen (N) and applied N on N2O emissions from the irrigated cotton farming system and its implications on farm economics. We conducted simulations for 116 years (1900-2015) and assessed the effect of different N-fertiliser application rates, initial soil nitrate (NO3) N levels and rainfall conditions on N2O emissions, N2O emission factors (EFs) and financial returns (with and without N2O costs). Results showed the following. 1) The proportional impact of higher N fertiliser rates on soil N2O emissions was greater when initial soil N level was lower (5 mg NO3 kg(-1)) than higher (35 mg NO3 kg(-1)). However, the volume of impact was greater under higher initial soil N levels. 2) The relationship between N fertiliser rates and the EFs (range 0.03-7.2%) was not linear but bell-shaped. 3) Fertiliser N requirements increased with rainfall and decreased with initial soil N. Accordingly, the cotton returns for the driest rainfall condition ( 90th percentile), these rates were 50 kg ha(-1) higher across the initial soil N conditions. Any additional application of N-fertiliser above these rates was counterproductive. 4) Inclusion of N2O cost into farm economics reduced the annual returns by up to $39 ha(-1), but the optimal fertiliser application rates remain the same. 5) Optimising N fertiliser rates to soil N and rainfall conditions increased the annual returns by up to$303 ha(-1), with a further increase of $15 ha(-1) from fertiliser use efficiency when the Australian Government incentives under the$2.55 billion dollar Emission Reduction Fund program was considered. These findings suggest that N-fertiliser application rates and N2O emission mitigation strategies need further refinements specific to prevailing soil and climate variabilities

Environmental and economic impacts and trade-offs from simultaneous management of soil constraints, nitrogen and water

Nitrogen loss and soil salinity are two key global issues for sustainable farming systems. Simultaneous mitigation of these issues requires contrasting nitrogen and water management practices, warranting a holistic understanding of the resulting nitrogen losses. This research aims to understand the i) interactive effects of salinity management, soil conditions and rainfall variability on nitrogen leaching, and ii) general trends in economic and environmental trade-off from reduced leaching fraction and nitrogen applications to minimise nitrogen loss. Simulations were run for 116 years (1900–2015) taking irrigated Australian cotton as a reference. Results showed that nitrogen leaching increased with leaching fraction, from 1 to 4 kg ha−1 for a soil comprising of high plant available water capacity + low initial soil nitrogen to as high as 46 kg ha−1 for its counterpart condition. Leaching increased with in-crop rainfall, the wettest conditions (679 mm) contributing for, up to 75% additional leaching. Depending on soil salinity, trade-off involving leaching fraction reduction by 0.05 units (from typical 0.20) resulted in lower drainage (up to 6%) and lower leaching (up to 5%) but also reduced the net returns (up to 50%). In contrast, nitrogen fertiliser reduction by 25 kg ha−1 (from typical 250 kg ha−1) showed little benefit to leaching reduction, but led to lower economic losses, higher nitrogen use efficiency and lower nitrous oxide emission. The study suggests that nitrogen losses under salinity can be alleviated through avoiding over-irrigation but without compromising the critical leaching requirements, applying fertiliser according to the soil spatial variability, and maximising rainwater use to meet leaching needs

Controlled traffic farming delivers improved agronomic performance of wheat as a result of enhanced rainfall and fertiliser nitrogen use efficiency

This study investigated the agronomic response and economic return of wheat grown in compacted and non-compacted soils to represent the conditions of non-controlled (non-CTF) and controlled traffic (CTF) systems, respectively. Yield-to-nitrogen responses were derived after application of urea, DMPP-treated urea, and UAN at rates between 0 and 300 kg ha−1 N. Soil properties were measured to guide parametrisation of APSIM, which was used to assess longterm (50 years) effects of CTF and non-CTF soil conditions on crop productivity, rainfall-use efficiency (RUE) and surface runoff. Grain yield and yield components were significantly higher in CTF compared with non-CTF. When N inputs were optimised, N use efficiency (NUE) was more than double in CTF (≈23%) compared with non-CTF (≈9%). RUE was about 15% higher in CTF, which concurrently reduced the amount of surface runoff compared with non-CTF. For years with average rainfall (240-mm in-crop), yield penalties of up 12% may be expected in non-CTF. APSIM simulations showed that increased productivity, and inter-annual yield stability, can increase gross margin of wheat by AUD30-50 ha−1 depending on in-crop rainfall and the tillage method used. In non-CTF systems, improvements in NUE and RUE are constrained by soil compaction. Enhanced efficiency fertilizers cannot compensate for other stresses caused by compaction and therefore cannot achieve the same NUE and RUE as the CTF system. Adoption of CTF in water-constrained environments improves profitability and resource-use efficiency

Agronomic performance of sorghum (Sorghum bicolor (L.) Moench) and fertilizer use efficiency as affected by controlled and non-controlled traffic of farm machinery

Compaction adversely affects the physical properties of soils and the ability of crops to efficiently use water (rainfall, irrigation) and nutrients, and therefore reduces the amount of fertilizer recovered in grain. This study was conducted to investigate the effect of traffic compaction on sorghum response to nitrogen (N) fertilization. Soil conditions (density) representative of controlled (CTF) and non-controlled traffic (non-CTF) farming systems were achieved by removing compaction through subsoiling to a depth of approximately 300 mm and by performing six passes of a medium-sized tractor, respectively. The soil type used in the study was a Red Ferrosol (69% clay, 11% silt, and 20% sand), which is commonly used in Australia for grain production. Sorghum was grown during the 2015-2016 season and fertilizer was applied at rates between 0 (control) and 300 kg ha-1 N at regular increments of 100 kg ha-1 N using urea (46% N), urea-ammonium nitrate (UAN, solution, 32% N) and ENTEC® urea (46% N). Grain yield was approximately 40% higher in the traffic treatment representative of CTF compared with that of the non-CTF, and consistent with differences (P<0.05) in all measurements of crop yield components (total aboveground biomass, harvest index, and thousand-grain weight). Fertilizer type had no effect on grain yield, which confirmed that traffic compaction was the main factor affecting crop performance and N recovery in grain and biomass. The optimum N application rates were 145 kg ha-1 N for CTF and 100 kg ha-1 N non-CTF, which corresponded with grain yields of 3430 and 1795 kg ha-1, and agronomic efficiencies of 24 and 17 kg kg-1, respectively. Given current price ratios (nitrogen-to-grain) and fertilizer type used, gross margin penalties of up to AUD75 per ha may be incurred in non-CTF systems compared with CTF when zero-tillage is practised, and about double when shallow tillage is practised. This study also showed that, regardless of the N formulation used, N use efficiency cannot be significantly increased if the mechanization system does not allow for avoidance of traffic compaction. Therefore, the benefits of enhanced efficiency fertilizers may not be fully realized if soil compaction is not appropriately managed. Improved soil structural conditions are a pre-requisite for increased fertilizer use efficiency

Value of seasonal climate forecasts in reducing economic losses for grazing enterprises: Charters Towers case study

Seasonal climate forecasts (SCFs) have the potential to improve productivity and profitability in agricultural industries, but are often underutilised due to insufficient evidence of the economic value of forecasts and uncertainty about their reliability. In this study we developed a bio-economic model of forecast use, explicitly incorporating forecast uncertainty. Using agricultural systems (ag-systems) production simulation software calibrated with case study information, we simulated pasture growth, herd dynamics and annual economic returns under different climatic conditions. We then employed a regret and value function approach to quantify the potential economic value of using SCFs (at both current and improved accuracy levels) in decision making for a grazing enterprise in north-eastern Queensland, Australia – a region subject to significant seasonal and intra-decadal climate variability. Applying an expected utility economic modelling approach, we show that skilled SCF systems can contribute considerable value to farm level decision making. At the current SCF skill of 62% (derived by correlating the El Niño Southern Oscillation (ENSO) signal and historical climate data) at Charters Towers, an average annual forecast value of AU$4420 (4.25$104 000, while a perfect (no regret) forecast system could result in an increased return of AU$13 475 per annum (13% of the case study average annual net profit). Continued improvements in the skill and reliability of SCFs is likely to both increase the value of SCFs to agriculture and drive wider uptake of climate forecasts in on-farm decision making. We also anticipate that an integrated framework, such as that developed in this study, may provide a pathway for better communication with end users to support improved understanding and use of forecasts in agricultural decision making and enhanced sustainability of agricultural enterprises

Insights into the value of seasonal climate forecasts to agriculture

Seasonal climate forecasts (forecasts) aim to reduce climate-related productivity risk by helping farmers make decisions that minimise losses in poor years and maximise profits in good years. Most Australian forecast valuations have focused on fertiliser decisions to wheat operations, and few assessments have evaluated the benefit of incremental improvements of forecast skill. These gaps have limited our understanding of forecast value to the broader agriculture sector and the benefit of investments to improve forecast skill. To address these gaps, we consistently assessed forecast value for seven Australian case studies (southern grains, northern grains, southern beef, northern beef, lamb, cotton, and sugar). We implemented a three-stage methodology which consisted of engagement with industry practitioners; modelling production under different climatic and environmental conditions; and economic modelling to evaluate forecast value for eleven levels of forecast skill. Our results show that forecast value was often low and highly variable. Value was found to vary based on forecast attributes (forecast skill, resolution and state), industry application and prevailing conditions (environmental and market). This is the first Australian valuation study where the same methodological approach was applied across multiple industries, incremental improvements in skill were valued, and prevailing conditions were explicitly evaluated for impact on value