Hanna Broderson
Precision Agronomist

Achieving even maturity is an important crop management factor. When you have an even crop stand, it can help alleviate the issues of lodging and green depressions that delays harvest. This often results in less shatter loss, better harvest fuel efficiency, and higher grain quality.

There are several factors that may cause uneven maturity. Poor germination and uneven emergence is a common cause. This typically happens when seeds that are sitting in drier areas of the field take longer to emerge. Saline depressions can also cause poor conditions for germination and emergence due to high levels of salts. The soil may crust over, causing high mortality. Non-saline depressions can have excessive moisture levels, crop residue, and colder soil, causing a delay in germination. Variable fertility and available water can also cause uneven or slower maturity in the field. It is important to have a good nutrient balance and suitable plant populations to avoid lodged crops later in the growing season.

When forced to manage uneven maturity, a pre-harvest desiccant application allows for a more efficient harvest. Using a pre-harvest tool allows for more even dry down of your crop, reducing the time from maturity to harvest. It can also reduce problems associated with late season weed growth. Pre-harvest desiccants can be used in many crops but are particularly common in pulse crops and canola. Choosing a product depends on crop type and reason for its use, such as weed control or quick dry down. Because desiccants are relatively expensive, considering a cost-savings method such as SWAT MAPS variable rate desiccation could be a great fit on your farm.

Just like variable rate fertilizer or seed, similar principles can be applied to a variable rate desiccation. VR desiccation uses varying rates of water (with chemical in solution) or using on/off prescriptions depending on your pre-harvest product of choice and goals. Cost savings could come from using less zero desiccant on more mature areas of the field. Areas with late weed growth or immature crop can often benefit from the higher water volumes that provide more coverage with contact desiccants like diquat. It is important to first define your goal, which could change your approach to VR desiccation. Are your hilltops thin and ripe and your depressions thick and green? Are you trying to target areas of your field with high weed populations?

Using your SWAT MAP or the latest NDVI imagery paired with some ground-truthing helps determine the highest green biomass areas versus low biomass areas as well as the high weed biomass areas. Prescriptions created using NDVI imagery are based on high green biomass versus low biomass areas, zone 1 being the highest biomass and zone 10 being the lowest. One approach shown in figure 1 is based on applying a pre harvest application of diquat (i.e. Reglone) throughout all zones in the field at different rates. Zones 1-3 have the highest rates of Reglone at 14 gal/ac, applying higher product rates to the greenest area in the field. Zones 5-10 have the lowest rates of Reglone on the more mature mid-slopes and hilltops.

A second approach shown in figure 2 for a more extreme situation takes advantage of turning off the sprayer in the lower biomass areas (typically mature hilltops) where a pre-harvest application would have no benefit, while still applying labelled rates in areas that will benefit. In these situations, cost savings can be substantial.

If you would like to learn more about our VR program which uses SWAT MAPS technology, or any of our new innovations, please connect with us at sales@swatmaps.com. Or you can find more information on our website at SWATMAPS.com.