I. J. Yule

Rapid identification of soil textural and management zones using electromagnetic induction sensing of soils

Three surveys of a pastoral–cropping farming system were carried out over a period of 1 year, using an electromagnetic sensor and real-time-kinematic (RTK)-GPS. The maps produced delineated areas of different apparent soil electrical conductivity (ECa). These delineated areas were compared with soil units of a conventional soil map and results showed the ECa map related well to soil-particle-size classes. In addition ECa could be used to predict groupings of soil phases accurately within one soil type. Soil coring to depths of 1 m, to determine soil physical and chemical properties, showed ECa values were moderately well correlated (R2 = 0.72) to soil clay percentage, weighted for the soil profile. Soil fertility indicators, Olsen P (R2 = 0.61), cation exchange capacity (R2 = 0.59), and exchangeable magnesium (R2 = 0.76) also related well. The linear regression (R2 = 0.76) of ECa with exchangeable magnesium is thought to reflect the dominant clay mineralogy of the study area, i.e. chlorites weathering to illites and releasing magnesium to the soil solution. Discriminant statistical analysis of results showed point ECa values could be used to predict 2 major groupings of the mapped soil phases with 100% accuracy. More precise prediction of these mapped soil units is constrained by localised management effects. Elevated ECa values occur at areas of soil compaction, which have been deduced from measurements of soil strength, aggregate size distribution and visual soil assessment.

A tractor performance monitor with DGPS capability

A data acquisition system was developed to monitor in-field performance of an agricultural tractor. Transducers were mounted to measure operational parameters such as the engine, wheel and ground speed with further devices to measure fuel consumption and field slope. The system also measured, displayed and recorded the forces acting on the three point linkage through a dynamometer system. The force measurement was effected through the lower links and top link, combining with angular position to give the total horizontal and vertical components of the forces acting on the tractor. The signals from the transducers were recorded and displayed on-line through Signal Centre Professional™ software. Thus, the operator was continually provided with useful information regarding the tractor’s performance. In combination with a real time DGPS link, each parameter was attributed to a geographical location and a number of performance parameters were subsequently mapped. Results from field work indicate that significant savings can be made through having appropriate information that allows machine set up to be improved. In this study, a saving of £4.70 ha−1 was demonstrated while using a tined cultivator in stubble.

Key Performance Indicators for Simulated Variable-Rate Irrigation of Variable Soils in Humid Regions

Decision support tools for precise irrigation scheduling are required to improve the efficiency of irrigation water use globally. This article presents a method for mapping soil variability and relating it to soil hydraulic properties so that soil management zones for variable-rate irrigation can be defined. A soil-water balance is used to schedule hypothetical irrigation events based on one blanket application of water to eliminate plant stress (uniform rate irrigation, or URI) and compares this to variable-rate irrigation (VRI), where irrigation is tailored to specific soil zone available water-holding capacity (TAWC) values. The key performance indicators, i.e., irrigation water use, drainage water loss, nitrogen leaching, energy use, irrigation water use efficiency (IWUE), and virtual water content, are used to compare URI and VRI at three contrasting sites using four years of climate data for a dairy pasture and maize crop and two years of climate data for a potato crop. Our research found that VRI saved 9% to 19% irrigation water, with accompanying energy saving. Loss of water by drainage, during the period of irrigation, was also reduced by 25% to 45% using VRI, which reduced the risk of nitrogen leaching. Virtual water content of these three primary products further illustrates potential benefits of VRI and shows that virtual water content of potato production used the least water per unit of dry matter production.

A spatial inventory approach to farm planning

Abstract In order to make more economic use of inputs and improve environmental protection by reduced leakage of nutrients and pesticides from agricultural land, it is necessary to target these inputs in relation to the demands of crops and livestock. In the near to medium term, we are unlikely to attain a tightly closed feed-back loop in the crop production process where the needs of the crop can be sensed and the deficiencies made good in real time. An alternative approach is the tactical one which integrates data from many sources over space and time and makes informed predictions about the probability of outcomes. Geographical Information Systems (GIS) provide a method of storing, managing, analysing and displaying information concerning processes and properties related to geographical location. An on-farm system has the potential to provide data to a high resolution which is of practical use in the control and application of production inputs. GIS would allow the farm planner to break down the constraints of field boundaries to consider areas enclosing land of similar crop production capabilities. The planning inventory is built up in the cell structure of the database by locating data on altitude, aspect, slope, existing cover, soil properties such as depth of soil horizons, organic matter, N.P.K. levels, rainfall, temperature, drainage patterns, weed counts, point sources of pollution, etc. This paper describes a system which will meet the planning requirements and provides an initial analysis on the financial benefits of such a system.

precision dairy farming in Australasia: adoption, risks and opportunities

Dairy farm management has historically been based on the experiential learning and intuitive decision-making skills of the owner-operator. Larger herds and increasingly complex farming systems, combined with the availability of new information technologies, are prompting an evolution to an increasingly data-driven ‘precision dairy’ (PD) management approach. Automation and the collection of fine-scale data on animals and farm resources via precision technologies can facilitate enhanced efficiency and decision making on dairy farms. The proportion of dairy farmers using this approach is relatively small (between 10 and 20% of farmers); however, industry trends suggest a continual increase in the use of precision technologies. Australasian PD farms have reported both positive and negative stories regarding the approach but to date there has been little industry attention or co-ordination in Australia or New Zealand. A series of workshops was held in late 2011 between industry-good representatives, researchers and farmers, from Australia and New Zealand, to discuss the opportunities and risks associated with PD. To take advantage of the emerging PD opportunity the trans-Tasman workshop group suggested five focus areas including: industry-good co-ordination and leadership in precision dairy; working to define the on- and off-farm value of PD; improving the technology available to farmers; integration of PD within farming systems for improved management; and developing learning and training initiatives for farmers and service providers. Action in these focus areas will enable future dairy farmers to implement the PD approach with enhanced confidence and effectiveness.

Developing variable rate application technology: Modelling annual pasture production on hill country

Abstract A great deal of modelling work has been completed in New Zealand and overseas on factors contributing to variations in pasture production. Although there are many factors that affect this, some have far greater influence than others. This paper discusses some of the important governing factors that previous researchers have identified, and also comments on the modelling techniques used by others in attempting to model annual pasture production. One of the more adaptable techniques, commonly called decision tree modelling, has been selected and applied to a large sheep and beef, hill‐country farm. The resulting annual pasture production was compared with an animal intake model. Both approaches were in very close agreement. This indicates that the decision tree method could be a very useful tool in the management of hill country properties when linked with a geographical information system. Embedding a pasture production model within a geographical information system is useful as it helps to identify strategic opportunities for either increased production or greater efficiency of inputs, particularly if within‐field variation is scrutinised.

Estimation of the in-field variation in fertiliser application

Abstract Variation in field application from a centrifugal fertiliser spreader has, in the past, been difficult to assess due to the intensive field testing required. However, with the application of current technologies such as Global Positioning Systems and Geographic Information Systems, the assessment of field application variation is now possible. The aim of this research was to develop a method to assess field application variation using basic transverse spread pattern test and vehicle tracking data. The information was used to measure and compare the effect of spread pattern, driving accuracy, driving method and paddock shape. Two differently shaped paddocks were used for analysis, one rectangular, the other triangular. A simple analysis method was initially used to calculate which areas of the paddock received nil, single, or double application. An advanced assessment method was also developed to measure application variation within the paddock and to calculate field application variation. Transverse spread pattern data was averaged at 2 m increments and linked to GPS tracking data from the spreading vehicle using ArcGIS 9.1©. The dataset was then analysed and a field application map produced. The field coefficient of variation (CV) was then calculated from the application map. Three simulations of perfect driving width and perfect application pattern were also conducted as a means of comparison to the actual field data. Simple analysis results showed, in both paddocks, the area receiving the correct application rate was between 70 and 80%, with 5–15% of the area receiving nil application. Using the advanced analysis method, the calculated field CV was 32.9 and 43.0% for the triangular and rectangular paddocks, respectively. However, when simulated “perfect driving” tracking data were used, the average field CV was reduced to 24.8 and 23.5%, respectively. When both perfect driving and a perfect spread pattern were used field application variation could be reduced to less than 20% for either shaped paddock. The results concluded that there is far greater variation in field application of fertiliser than that measured from a single transverse test, with the single biggest gain in calculated field CV being from driver accuracy and driving method.

Developing variable rate application technology: Economic impact for farm owners and topdressing operators

Abstract The use of variable rate application technology on topdressing aircraft is now technically possible. Its uptake will be determined by the economic benefit to the farmers and pricing structure for aerial operators. The economic impact of six fertiliser spreading scenarios were examined at a case study farm. Farm operating costs were considered under each of the scenarios and the economic consequences calculated. Variable rate application was found to be financially viable, both in terms of maximising return per hectare and increasing fertiliser use efficiency. Under the most productive scenario, the farm was modelled to provide a 26% higher cash surplus per hectare than it is currently modelled to achieve. This was due to the systems ability to match the supply of nutrient to the pastures nutrient demand across varying topography, resulting in an increased economic output for the farm. The cost of implementing such a system was not prohibitive and would provide aircraft operators the opportunity to add value to the services they provide, while improving their own business sustainability.

Developing variable rate application technology: scenario development and agronomic evaluation

Abstract Six fertiliser application scenarios were considered on a hill‐country case study farm. The scenarios were developed for input into a decision tree model and were compared to a base line scenario that uses the farms current blanket application techniques. A further blanket application was considered along with several variable rate application scenarios. Throughout this study, variable rate application technology outperformed the fixed rate applications in terms of pasture production and fertiliser utilisation. One scenario, which used full variable rate application and a model optimised prescription map, produced the highest annual pasture yield across the 2518 ha Limestone Downs property, North Island, New Zealand, with 24 789 t DM, some 4854 t DM more than the property is currently modelled to produce. The blanket application techniques which are currently employed on this property produced the lowest annual pasture production with 19 935 t DM yr–1. Variable rate techniques were predicted to increase annual production considerably, from 19 935 t DM yr–1 to between 21 239 and 24 798 t DM yr–1; in these cases, an increase in the production variability is also expected. Increased annual production from targeting additional fertiliser resources at more productive areas was identified through the decision tree modelling. Some areas were identified as having poor response to fertiliser, and fertiliser application to those areas was considered uneconomic.

Accessing Spreader Performance for Variable Rate Fertiliser Application

A spreading test program was developed to evaluate the ability of obtaining an accurate spread from a groundspread machine under different testing protocols operated throughout the world. The test program involved laying out an array of 1400 0.5 x 0.5m trays edge to edge which allowed a full measurement of the spread pattern occurring from a single spreader to be measured. Results showed that measured certifiable bout width differed by 14.8m at 15% Coefficient of Variation and 2.3m at 25% Coefficient of Variation. The ability of a spreader to be adapted to perform variable rate application was also investigated. A Nitrogen application map was created based on pasture growth and soil information. Test data collected from the spreader was used to simulate the ability to perform variable rate application using a geographical information system. It was concluded that overlap spread pattern was a major limiting factor of accurately applying fertilizer in the correct application zone. The investigation gave the ability to observe firstly, what the adequate requirements are for a spreader testing program, and secondly, how the collected information can be used to assess potential for variable rate application.