What is the Value of SWAT MAPS?
There is no single answer to the value of SWAT MAPS because there are often multiple objectives, which vary from farm to farm. It is a cumulative effect of multiple actions that lead to positive value, both short-term and long-term. Yield, quality, harvestability, and harvest timing are common benefits. Regardless of farm location or specific goals, the objective is proper allocation of resources for better return on investment.
This page details agronomic/environmental and economic benefits of using SWAT MAPS.
Agronomic & Environmental Benefits of SWAT MAPS:
ROI ON APPLIED NUTRIENTS
The goal is to allocate nutrients across the farm to where there is the highest chance of return. Nutrients can be allocated from field to field as well, not just within a field. Applying nutrients where the probability of response is the highest and lower rates whether the soil nutrient supply is sufficient or excessive is a strategy SWAT MAPS consultants often engage in and see value.
EVEN CROP STAGING
Achieving a proper plant stand will help to even maturity and crop staging throughout the season.
Balanced nutrition adds additional value in minimizing lodging and delayed maturity. This significantly helps to control disease and hasten maturity in low areas that are normally too delayed to harvest while the rest of the field is ready.
Crop lodging is typically predictable and occurs in lower slope positions and high yielding depressions. The cause is often nutrient imbalance combined with high water driven yield potential and excess vegetative growth. This can be managed by addressing specific nutrient balances in each zone and achieving target plant stands with VR seed.
SWAT MAPS are the best way to delineate areas of salinity, even if a field has a mix of saline and non-saline depressions. Often the opportunity with salinity, if these soils can’t be drained and improved, is to cut nutrient applications based on their limited yield potential and increase seeding rate to try and get better crop establishment to use soil water and compete with saline tolerant weeds.
Ripping and/or treatment of sodic soils with gypsum can be better directed using SWAT zones for a better ROI, since these activities are rarely needed in a whole field and are expensive. SWAT MAPS are particularly effective at delineating solonetzic soils with high sodium (Na).
The combination of layers that go into SWAT MAPS often provides a strong trend in soil pH and correlation
to zones in areas with acid soils. Acidification is the result of crop removal, lower CEC soil (more sand), and high nitrogen loss. This provides the ability to only lime zones where it is necessary for a much better ROI than a flat rate, blanket application.
SWAT MAPS are very effective at identifying areas that will be prone to nitrogen loss from leaching or denitrification (water-logging). This enables the use of nitrogen stabilizers or specific nitrogen sources in the areas where loss is expected, reducing the overall cost compared to a flat rate application, but still getting most of the benefit.
VR seed rates are commonly used to take advantage of differences in available water holding capacity and yield potential, for using multiple hybrids that are suited to specific soil types or conditions. Having water as a layer in SWAT MAPS allows us to tailor planting rates or hybrids by moisture environment.
SOIL APPLIED HERBICIDE
Depending on the extent of variability and distribution of target weed species, SWAT MAPS can be used for VR soil-applied herbicides. Most herbicides applied to the soil as a pre-emergent have rate ranges based on soil properties that are mapped and measured with SWAT MAPS and soil sampling. This enables use of VR to apply the correct rate of herbicide in each zone to avoid poor weed control in some areas, and potential carryover in other areas. Also, some weed species are highly adapted and problematic in only certain areas of the field, such as foxtail barley or kochia in saline areas, or wild oats in higher moisture areas.
While it is hard to put a monetary value on environmental stewardship, almost all of the above value statements have a strong environmental value component. Whether it is managing excessive water, reducing over-application of nutrients and nutrient loss, or even reducing pesticide use, these are all goals that farms should be striving for to improve long-term sustainability.
Economic Benefits of SWAT MAPS: Quill Lakes Case Study
In 2018, a study of 66,178 SWAT mapped acres in around the Quill Lakes in Saskatchewan revealed farmers are over-fertilizing depressions and saline areas. 19.2% of acres were affected annually due to excess water (poor drainage and high water table; see table on left). 16.6% of acres were affected annually from light to severe salinity (see table on right).
Benefits of SWAT MAPS demonstrated by the Quill Lakes Study:
1. Measureable reductions in costs with no reductions in yields
The 16.6% and the 19.2% acres are in the same spots; the water problems and the salinity problems are one and the same.
Thus, it could be said that on average, 18% of the acres in this watershed have low yields due to these issues and we have them mapped out perfectly. A typical farmer applies $100/ac fertilizer to canola and $80/ac fertilizer to wheat (our most common crops). It is common to have $90/ac fertilizer usage as an average. Reductions of fertilizer use in these areas have gone from 100% rates to approximately 50% of rates (zero rates not really possible with todays low resolution equipment application). Only a Cleanseed drill or Precision Planting planter could apply high resolution prescriptions.
$90/ac fertilizer use * 18% acres * 50% reduction = $8.10/ac reduction in costs to the farmers using SWAT based prescriptions
Note: a typical farmer pays $3.50/ac for full farm agdata software, SWAT soil sampling, prescriptions, fertility plans and two trips to the farm for ground truthing.
2. Yield increases and other intangible benefits
This is the largest value proposition to the farmer. Depressions are typically late maturing, have increased disease, and more lodging. This leads to harvest inefficiencies and lost yields. Midslopes and well drained depressions are typically underfertilized. Fertilizing to the field average limits yield potential in the best soils in the field. Sandy areas and eroded knolls are typically over-fertilized. They are not high production areas. Reallocation of nutrients in the field to reduce applications in poor production areas and increase the fertilization to the best soils in the field leads to improved yields and more ven harvestability.
This benefit has been measured in previous studies to be approximately $9/ac on Nitrogen, $6/ac on Sulphur, and $10/ac on phosphorus. Seed rate studies have proven value but we have no economic numbers at this time. Some years are higher and some years are lower value, some fields have higher and some have lower value. This is very difficult to quantify without trials on every farm every year. We are claiming an average annual ROI on SWAT prescriptions to be approximately $25/ac plus intangible benefits such as harvestability and improved crop quality.
3. Measurable impact to the environment
These same spots in the fields always test the highest in residual nitrates, phosphates, chlorides and sulfates (N,P,Cl, S). They are high organic matter areas, areas that accumulate water and have high water tables, and have higher concentrations of salts (typically sulfate or chloride based). Mobile nutrients such as N, Cl, S accumulate in water collection areas.P accumulates due to historical erosion of topsoil accumulations, leachate of P from crop residues that accumulates during spring runoff. All nutrients mentioned also accumulate because farmers continue to apply fertilizer at a constant rate throughout the field. The low yield potentials cannot use it, therefore they accumulate in the soil.
This combination of issues means that in the watershed all of these excess nutrients end up in the overflow that runs off fields and into creeks, rivers and ultimately lakes. It increases salinization of water bodies and also leads to eutrophication and algal blooms.
Farmers using our system save themselves money plus are better environmental stewards, even though there is zero recognition or payback from the practice.
4. Water management
Major battles have ensued in the watershed over drainage. Farmers are obviously losing 18% of their land to poor yield due to high water tables and water accumulations in potholes in the fields. Rising water levels in local lakes such as Fishing Lake and the Quill Lakes has flooded out farmers downstream. If these areas were drained or ultimately tiled, they could all be brought into production and the higher yields from crops would then start utilizing much more water within the field. Farmers would get higher yields, there would be less runoff than their currently is. More nutrients could be used up in these areas.
In the Quill Lakes watershed study, SWAT MAPS reduce a farmers' costs by $8.10/ac on average in high risk flooding and salinity areas.
This reduction in fertilizer use in high risk of runoff areas that already have excess nutrients reduces salinization and eutrophication, reducing downstream impacts. Often, the $8.10/ac is reallocated to more productive soils that are low in nutrients due to high annual production, leading to potential ROI of $25/ac for fertilizer.