When it comes to understanding the right time to apply nutrients, it is important to know when it is the wrong time.
Several years ago it had been a wet and frustrating fall for getting any field work done in the Lost Creek Watershed in northwest Ohio. It was followed by a fairly cold winter and there was an extended period of frozen conditions in February that provided a great opportunity to catch up for lost time.
“We got a nice window and pretty much every dealer in the area was working on spreading fertilizer on frozen ground. There was about four inches of snow cover. Less than a week later we received a three-plus-inch rain event that melted the snow and allowed for major surface runoff on the frozen ground. There was rain/snow in the forecast, but no one was forecasting a three-inch rain. So the farmers and dealers that were spreading weren’t really in the wrong. However, those conditions create a high risk for nutrients to leave the field and in this case that happened. It warmed up and we got a big rain and the toilet flushed,” said Clint Nester, with Nester Ag, LLC in Williams County. “It was the one of the biggest phosphorus levels Heidelberg University has ever recorded in the water monitoring of the watershed. Those applications were made at the wrong time — everything else was right — and we lost nutrients big time.”
In many ways, the right time is the easiest of the 4Rs to understand, but one of the hardest to actually do. Hindsight can make the wrong times to apply fertilizer seem very obvious, but the process of determining the right time can be quickly convoluted by weather uncertainties, changing soil conditions, farm work logistics, and just plain old bad luck.
“If you are a really good weatherman you can avoid a lot of those spikes you see with phosphorus loss from fields, but we know how well that works. That big rain event in the Lost Creek Watershed really opened some eyes in the area, including for our business,” Nester said. “Until that time we still had customers that took that opportunity to spread on frozen ground because it worked well for the logistics of getting things done. After that, guys backed off of doing that. Farmers don’t want their money floating down the river. And when that happens you never know what you really lost and don’t know how much to re-apply. In many cases, you have to assume you lost it all and you end up re-applying the whole rate. That gets expensive.”
Senate Bill 1 sets some fairly clear, common sense guidelines for applying nutrients at the right time in the Western Lake Erie Basin watershed. Specifically, for applications of granular fertilizer (defined as nitrogen or phosphorous) in the Western Lake Erie Basin, a person may not apply:
1. On snow-covered or frozen soil;
2. When the top two inches of soil are saturated from precipitation;
3. When the local weather forecast prediction for the application area contains greater than a 50% chance of precipitation exceeding: one inch in a 12-hour period for granular fertilizer or one-half inch in a 24-hour period for manure.
These requirements can be exempted if the fertilizer/nutrient is injected into the ground, incorporated within 24 hours of surface application or applied to a growing crop. This is the law for all or part of 24 counties in northwest Ohio.
For businesses certified through Ohio’s 4R Nutrient Stewardship Certification Program, these SB 1 rules are a good common-sense start to avoiding costly nutrient loss by applying at the right time, said Chris Horning, the North Data Operational Lead for Sunrise Cooperative. Sunrise was among the first 4R Certified businesses.
“We have a yearly applicator training that covers the 4Rs and usually the auditors will be out talking to the nutrient applicators when they are doing the audit. They incorporate a lot of the 4Rs into the two-day training session,” Horning said. “The applicators know that if they are in the field, 95% of the time the weather forecast is not going to tell you about a three- or four-inch gully washer. If they are sitting there and the sky is black, they know they need to check back with the office and make sure they are still on track with the operation manager and the grower as far as the timing goes. If there are any questions on field conditions or the way the weather looks, they need to check back in. We do a lot of things ahead of time to try and not get in that position sitting in the fields in the spring waiting to putting fertilizer on, but rainfall is one of the biggest issues that creates challenges. Most guys don’t want you out there in saturated soils anyway and the frozen ground we know to avoid.”
Sunrise has seen a big shift to spring application away from putting on nutrients in the fall. The cooperative also works on more applications of smaller amounts of nutrients.
“We are geared up with equipment to split those applications up with in-crop dry applications and we are working with farmers with Y-Drops, using different nitrogen models to determine the right rate for the growing season. And for the fall applications, we are putting down just a one-year supply of nutrients and not two or three,” Horning said. “We have been working closely with the 4R guidelines and if we are spreading in the fall, it is incorporated within 24 hours and that takes a lot of pressure off.”
Horning said another very useful tool for nutrient applicators is the Ohio Nutrient Management Record Keeper (ONMRK) app. The app was developed with input from Ohio State University Extension in Knox County, Ohio Farm Bureau, and Knox County Soil and Water Conservation District to meet the new state recordkeeping requirements for both SB 1 and Senate Bill 150. ONMRK helps farmers comply with state laws by recording their fertilizer or manure application as well as the current weather conditions and forecast for the next 24 hours.
“That is really handy. It gives you the 12-hour and 24-hour forecast for the spot you are sitting and really helps you meet the guidelines. It also helps with documenting it as well. You can get that app for free on your phone. It will even tell you if an application is recommended or not,” Horning said. “It really helps us to be compliant.”
The requirements of SB1 create a base to further refine nutrient application recommendations from Nester Ag that has also been certified through 4R Nutrient Stewardship Certification Program.
“Guys are paying big dollars to put those nutrients out on the land and when we make recommendations we don’t put a fudge factor on there for what is going to the ditch. We want the nutrients they apply to the field to stay in the field. Those laws are in place but it also makes sense with economics to keep those nutrients in the field,” Nester said. “Those laws are only for nitrogen and phosphorus, so if you wanted to spread potash when a rain is coming there is no law to say you can’t do that, but we tell guys it is a high risk time to apply those and that they need to avoid any potential for the nutrients to leave the field. That just makes sense economically and environmentally.”
Beyond those basics outlined in SB 1, there are still many right (and wrong) times to apply nutrients to fields. There are clear advantages to minimizing nutrient loss by applying the right rates of nutrients as close to the time when the plants need them as possible during the growing season.
“If a guy can apply in the spring I would say that probably reduces the risk of losing those nutrients because you don’t have them out there during the winter months when you can get those two- or three-inch rains on frozen ground and soil is moving,” Nester said. “But, on the acres that some guys cover, they just can’t do it all in the spring. In some cases, they will do some of their acres in the fall and leave their leakier fields — the fields that are more prone to leaching — to get to in the spring. With nitrogen we still tell our guys to break that total nitrogen up if possible so maybe they’ll be putting a little on with their broadcast fertilizer, maybe some ammonium sulfate. Then they could come in with some starter on the planter and then come back with some weed and feed either before or after the planter, based on their program. Then we can come back with sidedress and some guys are now coming back with the Y-Drops for a fifth trip.”
But even with the extensive effort to put nitrogen on at the right time for the plant, loss is still possible.
“Nitrogen loss is very weather dependent. This year there was not much loss in this area. In 2015, though, we saw an example of too much rain and definite nitrogen loss in the corn crop,” Nester said. “We have seen instances when you get early spring rains and if you have put everything out up front, you get problems. Having it split up reduces the risk of losing huge amounts of nitrogen. If you lose 10% of 10% it is a big difference compared to losing 10% of your total nitrogen.”
The right time for phosphorous applications involves considering an entirely different set of factors. There are plenty of wrong times to apply phosphorous, but there are some things that can be done to expand the windows of “right time” opportunities.
“Phosphorus is a whole different animal and it is hard to pinpoint because we have such a large pool of phosphorus available in the soil that is not available to the plant. It is always cycling. We have tried to put out phosphorus plots to learn more. You can not spread phosphorus one year and you won’t see a yield decrease unless you have critically low P levels. We can’t show much data about timing of phosphorus applications making a difference one way or another,” Nester said. “We do know if we can avoid putting it on the surface in the fall it reduces the chance to lose that dissolved reactive phosphorus over the surface or though the tile. Incorporating it can be a viable solution to try and keep it in the field.
“No-till situations can lead to bigger pores and more pathways for it to get to the tile. Strip-tilling phosphorus in the fall can work too as a pretty safe way to apply. You put it right in the soil at the root zone where the crop will need it. We work with guys who strip-till and we have been able to reduce rates by about 20% and we checked it with strips in the field and we are not taking any yield hit with that 20% reduction. Strip-tilling it in in the fall is very efficient. You are getting it incorporated in the soil and we can apply less fertilizer and keep yields up. It saves money and doesn’t allow for much runoff to the streams.”
Cover crops are also a great tool for making more opportunities to apply at the right time.
“We preach cover crops to our customers for a multitude of reasons. Hopefully they get a yield gain, they reduce erosion and they help keep nutrients in the field,” he said. “The ideal situation in the fall is to apply to a cover crop — something that is going to overwinter. Some guys plant radishes or oats and as soon as we get the first freeze they are done. There was some research that showed radishes alone as a cover crop were bringing nutrients to the surface and really concentrating them there to the point that it was more of a detriment to planting radishes only than getting a benefit. If you are going to run one cover crop it should be something that will stay green all winter. And, if you are going to apply when conditions are a little iffy, a cover crop definitely reduces that risk factor.”
Ultimately, the right rate of the right product at the right place does little good if applied at the wrong time.
“You can do three things right with the 4Rs and still be wrong,” Nester said. “You have to do them all and follow those four key principles. You can’t just do one.”
For more, visit 4rcertified.org.