H. G. Lawrence

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.

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.

Development of an Image-Processing Method to Assess Spreader Performance

Fertilizer spreader testing plays an important part in achieving accurate, uniform application of nutrients to the land; however, current testing methods are often laborious, with high levels of manual input required to obtain specific spread characteristic information. This study aimed to review and identify potential techniques and test one that could be incorporated into a spreader testing program. A review of available spreader tests throughout the world showed varying results. Measurement systems requiring a mathematical algorithm to calculate the landing position of individual particles were found to be quick interpolators, but inaccurate. Tray collection, used extensively by quality assurance programs throughout the world, is accurate in producing distribution pattern results; however, it is a laborious task, especially when analyzing multiple spread patterns for variable-rate application. An image-processing method showed the greatest potential as a rapid analysis and interpretation tool of spread pattern data. A computer program was written to analyze and extract individual particle information from urea fertilizer contained on collector trays during a spreader test. Results indicated that there was a strong relationship between two-dimensional particle area and particle mass under laboratory (R2 = 0.991) and field (R2 = 0.988) test conditions. Measurements taken within ±4 m of the spreading vehicle had a higher expected error when predicting particle mass, which was attributed to a high proportion of particles with a cross-sectional area less than 1 mm2. High levels of expected error in field results indicated that particles need to be greater than 1 mm2 after spreading if the method was to accurately predict an entire distribution pattern of a fertilizer spreader. However, the method was found to accurately calculate the size guide number and uniformity index of the collected sample.

A GIS Methodology to Calculate In-Field Dispersion of Fertilizer from a Spinning-Disc Spreader

A model was developed within a GIS environment using the transverse spread pattern and GPS driving track during spreading to map actual fertilizer application at any point in a paddock. The spreading vehicle required a GPS of sufficient accuracy in order to provide proof of placement and guidance assistance to the driver. The method was used to assess the effect of field size and shape on actual application rate and application variation. At a target application rate of 80 kg ha-1, measured application rates ranged from 51.8 to 106.7 kg ha-1 of urea (46% N) fertilizer over 102 paddocks on four farms. Average field variation calculated over all paddocks was 37.9%. Irregular-shaped paddocks were found to have higher application variation (40.8%) compared to regular-shaped paddocks (35.9%). Hot spot analysis was performed to identify areas receiving statistically significant high and low application rates (s < 2.0). Over all paddocks, 7.4% of the total area received significantly high application rates, while 10.2 % received significantly low application rates. This information, collected over a number of applications, could be incorporated into subsequent variable-rate application maps whereby rates could be adjusted on areas that have received incorrect quantities of fertilizer in previous applications. This system will improve sustainability for a farm by ensuring that nutrient management plans can be followed, as well as providing a means of traceability and proof of placement.

A statistical analysis of international test methods used for analysing spreader performance

Abstract There are a number of tray testing methods used throughout the world to assess the distribution accuracy of fertiliser spreaders, all of which calculate differences in distribution pattern. The main objective of this work was to perform a statistical analysis of the differences between methods. The effect of variations in calculated bout width due to change in distribution pattern was investigated. Six international test methods were compared simultaneously using a matrix of 1400 trays, each 0.5 × 0.5 m. Each test method was able to be extracted from the tray matrix. Urea fertiliser (46% N) was used for all tests at three application rates, 80, 100, and 150 kg ha–1. A simulation model created in @RISK was used to predict certifiable bout widths from each test method using overall spread pattern characteristics and statistics. Results indicated that there were major variations in calculated certifiable bout width using the different methods. Tray layout within ±5 m of the spread line had the biggest effect on calculated bout width. Method designs that incorporated trays in the longitudinal direction were more accurate in predicting the average variation than when a single transverse test was used. In conclusion, if comparison is required between two or more spreaders, the same test method and tray layout should be used. Having a sufficient concentration of trays within ±5 m of the centre of the distribution pattern will describe the behaviour of a spreader with greater accuracy.

A method of calculating the economic impact of poor fertiliser spreading

The testing of broadcast spreaders is important in determining levels of machine performance, however, levels of field performance, although harder to ascertain, are required to fully understand the agronomic and economic efficiency of fertiliser application. This paper presents an “as-applied” application model that uses both pre tested and real-time parameters to measure field application variation. The model also allowed the agronomic and economic performance of each fertiliser application over a 12 month period on a New Zealand dairy farm to be evaluated. Results indicated that field variation was between 23.5 and 80.0% over all applied products, this resulted in an economic loss of NZ

Economic and Environmental Opportunities from Utilizing VRAT from Aircraft for Improved Placement of Fertilizer

66.18 ha-1 per annum. For a typical New Zealand dairy farm results would indicate that poor spreading could be costing between NZ

Accuracy and Confidence Issues Around Broadcast Spreaders Transverse Pattern Testing Methods.

52 – 72 ha-1 per annum.

A statistical comparison of international fertiliser spreader test methods — Confidence in bout width calculations

Large parts of New Zealand have been in agricultural production for less than one hundred years. In many cases farmers are still trying to develop their properties. The ability to top-dress fertilizer from aircraft has been an important part of that development as access is impossible with wheeled vehicles and because of the large areas that need to be covered. Recognition of the variability of the pastoral country gives an opportunity to further target development expenditure. Poor economic utilization of fertilizer usually means greater opportunity for nutrient leakage and adverse environmental impacts. Further developments in VRAT cause us to examine the levels of precision in existing systems and their effect on economics of operation. A method of system analysis is presented both in terms of the basic ability of blanket application systems, followed by the impacts of implementing variable rate. The flowability of material from the aircraft is an important factor in determining the uniformity of spread. Further studies are being performed to achieve a better understanding of the environment within the aircraft and the properties of the material being spread that affect the spread characteristics. Environmental agencies are also placing restrictions on the physical and chemical properties of material that can be spread from an aircraft as a permitted activity. Much more emphasis is placed on proof of placement and in a number of quality assurance programs it is a requirement.

Testing the viability of existing ground spread fertiliser spreaders to perform variable rate fertilisation.

A number of test methods are used throughout the world to ascertain the transverse spread pattern of spinning disc spreaders. All testing procedures are used to certify bout width of these spreaders, which are then used as part of quality assurance programs. Two main issues are considered in this paper; firstly, how comparable are tests with different tray configurations? This is considered using a number of scenarios where different tray configurations are used to identify the transverse spread pattern and the results are compared. Second; should multiple rows of trays be used to reduce the variation in results and increase the confidence level of the test?