1. Multi-year Experience with Yield Monitoring
Forrest Taylor
Barron Collier Partnership
Immokalee, Fl

2. Why Yield Mapping? Help identify problem areas.
Aid in identifying yield-limiting factors.
Use to make VRT prescription maps.
Facilitate data collection for yield trials.

3. Identifying Problem Areas
Yield is not uniform throughout a management unit, despite shared commonalities including rootstock and scion, planting date, and cultural methods. Maps of yield over several seasons will help determine if significant variation exists. If areas with significantly lower productivity can be be identified over several harvests these can be closely examined in the field for visual verification and to identify any obvious problems. A decline in yield can be an indicator of a problem.

4. Block with little variation
Valencia
20.21 acres

5. Block with marked variation
Pineapple
134 acres

6. Identifying yield-limiting factors
Most of the low-yield areas have inadequate drainage in very wet years. The yield map gives the extent and location. Further investigation involving soil coring will allow assessment of corrective cost and feasibility. Resets are on Swingle in this Carrizo block.

7. Low-yield area

8. Variable rate application
A uniform application based on the mean yield figure of 590 boxes per acre would be 236-lbs. of N per year, following the 200-lb. limit (because the average per acre yield is less than 700 boxes), would result in a total of 13.4 tons N. Use of a VRT prescription map that follows the 200-lb. limit for under 700 box acreage, and the 240-lb. limit for 700 boxes and above, would result in block total of 11.1 tons, for an average of 166-lbs. N per acre for the entire block. This would equal a savings in material of 15.3 tons of fertilizer at 15% N, which at $200 per ton would equal $3,600, or $22.84 per acre.
The real goal of VRT is better allocation of fertilizer, with higher-producing acreage receiving rates above the 200-lb. limit indicated by the block per acre average. At the same time inputs are reduced in areas of low production. The per acre limit of 200-lbs. could be exceeded to some extent for areas producing less than 700 boxes, while staying within the 200-lb/acre limit for the entire block. If a VRT map based solely on the 0.4-lb. N per box rule was used, the average per acre would be 203-lbs. of N.

9. Trial data collection
Harvest point files are overlaid with plot boundaries.

10. Extent of Coverage
7 units the first year; year two, switched to new hardware, 15 units – Geomax, more reliable, data downloaded automatically.

11. Success rate
Collected data must be within 5% of actual harvest. Rely on goat operator for accurate data entry. Data has operator ID stamp. We monitor data collection to look for operator problems.

12. Goals Identify problem areas – reveal them early
Better allocation of fertilizer – more in high-yield areas, less in low yielding ones
Ability to closely and more easily monitor yield effects of inputs – trials.