"Site-Specific" - What Does It Mean?
Site-specific is a term that refers to treating the smallest possible area as a single element.For instance, rather than treating a whole field with herbicide because of a few isolated weed infestations, site-specific management calls for treatment of only those areas.A site is simply the smallest unit the farmer can manage with the tools available, whether that is a 100 square foot area or an individual plant.The treatment of each site is specific to the needs of each site, as determined by soil test data and crop scouting reports.The implementation of the GPS has enabled farmers to accurately map their fields and narrow down their site size to only a few meters' area.With current computing capabilities, a field could be broken up into a grid of hundreds of separately manageable units.However, depending on field size and testing budget considerations, grid squares of an acre or two are common these days.
Steps in the Precision Ag Process
Precision agriculture is a cyclic process, of course, but a farmer can get started on site-specific farming at just about any time of the year.Generally, farmers need to perform annual planning, data collection, and analyzing steps to complete the precision ag cycle.
- Before Planting - perform soil testing, then data analysis to determine spatial variations in soil conditions that call for a variety of treatments or planting methods.
- In the Growing Season - begin by planting with variable seeding rates across the field, and use variable rate application (VRA) of fertilizers as determined by soil test data.Crop scouting is done to search for problems such as weeds, pests, or diseases.Findings determine whether further VRA of chemical treatments or other actions are warranted.
- During the Harvest - as the crop is harvested, a yield monitor in the combine logs geo-referenced yield data to be analyzed and mapped across the field.Variable yield results across the field can help the farmer discover if his management methods have been successful, and determine how to proceed in the next season.
Today's farmer depends on outside sources for some information, such as soil data.Testing laboratories can run soil assays for nitrogen, phosphorus, potassium, and other nutrients.There are various methods of sample point selection available to the farmer, and a sampling grid can be obtained from a GIS.The main point is that if more samples are taken in a field, the data will be more site-specific.This provides an initial base of information for developing VRA plans.
Planting - How and What
In precision agriculture, crops are planted at variable rates as determined from prior knowledge about field conditions and soil test data.Today's planting equipment can be programmed to deliver variable seeding rates; rate changes are determined and programmed by the farmer.What is planted is also of critical importance, and the explosion in development of genetically enhanced crops offers farmers an impressive advantage in choosing hardy, high-yield varieties.
As crops grow, observations must be carefully documented about any developing problems in the field.Although crop scouting is nothing new, today's crop scouts can enter their observations into a GIS, linked to the precise location of the problem via GPS data, and the information can be analyzed by comparison to other data in the GIS.
Traditionally, knowledgeable individuals able to identify numerous problems have done crop scouting.Among the modern crop scout's field tools are the GPS receiver and a laptop computer.With the advent of video mapping, any untrained person can record field conditions to be reviewed by experts later.Other methods of identifying problems in a field include aerial or satellite remote sensing.Presently these methods can be cost-prohibitive and have a high turnaround time.Improvements in satellite data availability are necessary, but eventually this may be a commonly used source of agricultural information.
Variable Rate Chemical Application
VRT (variable rate technology) and VRA (variable rate application) refers to the development of automated variable rate sprayers, which are an extremely important tool in precision agriculture.Where the practice of whole-field application of chemicals has been replaced by site-specific treatments, sprayers capable of variable rate applications are essential.These machines are programmed to deliver precisely the right amount of chemicals necessary across a field, after input from crop scouting and analyzing the variability of field conditions.This element in the precision agricultural system is greatly responsible for lowering cost of input and decreasing environmental impact, through the automated application of the least amount of chemicals necessary.
Yield monitoring is probably the most important cornerstone of precision agriculture.The traditional method of monitoring yield by weighing harvested batches of crops is giving way to the precision agriculture method of instantaneous yield monitoring.The modern yield monitor utilizes sensors in the combine to continuously log grain flow rate during harvesting, and the combine's speed.This data, combined with the GPS location for each data point, allows the creation of a yield map within a GIS.The yield map is a visual tool farmers and crop consultants can compare to maps of soil test data, chemical application maps, and other information, resulting in a recommendation for the next year's site-specific management plan.When layered in a GIS with associated maps, a yield map displays evidence of relationships between crop yield and field condition variables.