Uses Of Yield Mapping And Monitoring And Associated Benefits

Yield Monitoring and Mapping

With respect to agricultural practices, crop yield or ‘agricultural output’ is a measure of the amount of produce of a given crop per unit area of land that is cultivated. Crop management strategies shouldn’t be formulated with the assumption that the crop yield will be uniform-unless the yield potential is known to be such that. Variation in soil attributes such as soil texture, structure, depth, pH, nutrients, organic matter and water density all have a significant impact on crop yield variability. Whilst soil testing would seemingly be the most explicit method to measure these attributes, yield monitoring and mapping can serve as an indirect method. If it is understood what soil conditions result in the optimum yield of a given crop, yield mapping can spatially indicate how these conditions vary to some extent-they cannot be directly quantified using such a method however. Yield monitoring systems were first introduced in the 1990’s and allow yield variations to be measured whilst a paddock is being harvested. Such systems are increasingly becoming a conventional practice in modern agriculture.

Mapping of spatial variability in agricultural output typically is achieved through a system devised of:

• flow sensor: measures crop volume harvested
• moisture sensor: measures moisture content of harvested material
• data logger: records position of machine and crop ‘measurements’ at such a location
• GNSS receiver: determines position of machine
• machine guidance system: can automatically direct combine harvester using attached GNSS receiver (this is optional).

With these measurements, a geographic information system (GIS) can be optimised to display the yield of the harvested crop at specific locations across the terrain in focus.

With a raw yield map at the user’s disposal, the causes of spatial variability in output can be further investigated. A common practice undertaken with such data is to convert yield inconsistency into fluctuations of a range of ‘categories’ with the input of a collection of elementary parameters. Such fluctuations include

• profit: gross margins can be estimated. This information can often be considerably more informative to the user as it can be visualised where parts of the property are performing well and where other parts aren’t-potentially losing money
• quality: with ongoing development in technology, real time protein content measurements of harvested crop are becoming a possibility. This information could potentially be used to allow the user to segregate material collected from specific parts of the paddock if it does/n’t conform to a required standard/grade.

In conjunction with this, a GIS can also be used to compare yield maps of the same area from successive harvests to determine if yield is improving or declining. Indirectly, the collected data can also be utilised to determine if the need for variable rate application (VRA) of pesticides/herbicides etc. will be necessary in the future for a given area.

Relevance to Site-Specific Crop Management

Yield monitoring and mapping is an example of a collection of the core components of site-specific crop management:

• spatial referencing: use of GNSS
• crop monitoring: measurement of yield volumes and other variables such as protein (developing technology)
• attribute mapping: visual display of collected data (typically in a geographic information system).

Yield maps represent one of the most valuable sources of spatial data for PA. Analysis of this information can allow one to investigate the array of factors that may catalyse fluctuation in crop output throughout a given area. A common method that is employed to address such a matter is variable rate applications of agricultural resources.