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Silage yield mapping


Grass silage electronic yield and quality sensing

In the utilisation of grass for grassing, grass measurement and budgeting technology has been is use for over 20 years with increasing numbers of farmers measuring grass covers weekly using electronic plate meters and customised software packages to make improved management decisions based.

Until recent years there has not been the equivalent opportunity to measure and manage grass silage swards. Most major silage harvester manufacturers are now providing electronic yield and quality sensing equipment. CAFRE have taken the opportunity to work with John Deere and Cairns Contracting to evaluate the data provided by the John Deere HarvestLab system while harvesting the 3rd cut silage at the CAFRE dairy centre in August 2018.

John Deere Harvest Lab

The John Deere HarvestLab 3000 system with Carl Zeiss near infrared reflectance spectroscopy (NIRS) analysis technology is marketed as ‘one sensor, three applications’ with the equipment designed for use in the following crop and nutrient sensing applications:

  1. Grass and forage maize quality and yield assessment during the harvesting operation
  2. Slurry nutrient content sensing during application
  3. Forage quality analysis on-farm

The HarvestLab uses a combination of global positioning satellite (GPS), mass flow sensors and an NIR sensor to document the area harvested, site specific yield of forage harvested and forage dry matter and constituent levels respectively. John Deere company literature indicates that the NIR sensor equipment provides for more than 4,000 measurement points per second.

Third cut grass silage harvest 2018

During the harvesting operation at Greenmount, all trailers were weighed over the farm weighbridge and representative grass samples taken from each load of grass for dry matter analysis on campus and quality analysis at the laboratory at AFBI, Hillsborough.

The results from the HarvestLab 3000 system were compared against the weighbridge measurements and the laboratory analysis results. The results were very promising, with correlations for many of the parameters above 0.90, despite the harvest only taking place across a small number of fields (nine) and a relatively small area of 28 hectares (68 acres).

Table 1. Correlation between Harvest Lab, weighbridge records and laboratory samples

Parameter measuredR2 Correlation*
Field area (ha)0.97
Fresh weight yield per field (tonnes)0.96
Grass oven dry matter (%)0.95
Dry matter yield per field (tonnes)0.95
Fresh weight yield per hectare (tonnes)0.48
Dry matter yield per hectare (tonnes)0.43
Laboratory dry matter (%)0.81
Laboratory grass sugar (% DM)0.62
*An R2 of 1.0 indicates a complete correlation with all variation accounted for. An R2 of 0.0 indicates no relationship between the data sets