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Optimal Nitrogen Rates for Soybean Yields

Soybeans, much like corn, are one of the most popular crops to grow worldwide. It’s no surprise then that multiple studies are carried out each year to find out how we can boost yields and profit as soybean farmers. With an ever-growing population of hungry mouths, a shortage of space, man power and funds, farmers need all the help they can get.

Did you know that soybeans require up to 5 pounds of nitrogen per bushel? That’s a lot of nitrogen and in most fields, natural nitrogen is already lacking after years of crop rotations removing said nitrogen faster than it can be produced. Sure, we can add fertilizer but that can get costly and run-off can seriously damage the environment.

Furthermore, the majority of soybeans will only fix enough nitrogen to produce 50 to 60 bushels even when nitrogen is applied to already established plants. To really boost the yield, you need to remove all other limiting factors too. Aim for optimal irrigation, sunlight, soil quality… the list goes on.

So, is there a way we can reduce the cost of nitrogen fertilizing and reduce the effects it has on the environment? This is exactly what Laila Puntel set out to find as lead author of a study issued by the Iowa State University.

The Study of Soybean Management and Yield Improvement

By predicting optimal rates of nitrogen needed in corn, we hope that the amazing results that Puntel’s study had can soon be applied to soybeans too. Using over 16 years of data plus some state of the art simulators, Puntel aimed to put an exact figure on how much nitrogen is needed for corn to grow at optimum.

This was a massive undertaking, but if successful Puntel could provide the solutions farmers have been looking for; reducing costs and use of nitrogen fertilizer while still boosting yields, profits and saving the environment.

Before this study there had certainly been attempts to work out the optimal rates of nitrogen, but the technology just wasn’t there. Now however, with the advance of precision agriculture and the wealth of tools available to researchers, success is within reach. So, using the data set covering 16 years of farming, plus very specific, accurate data on the field used in the study (achieved by precision agriculture tech), Puntel ran this through a simulator to find the optimal.

The researchers use APSIM (Agriculture Productions System sIMulator) and found that the more long-term data you have to input, the more accurate the results would be. They also found that the specific features of your fields have a huge impact on the resulting yield of corn (and the same can be said for soybeans). So, while these results proved a success in the simulator for the specific field they were targeting, you can’t really apply these results to your farm as the specific factors (soil type, climate etc.) are really what’s needed to provide accurate results…

…but we don’t want to leave you feeling disheartened! This really is a huge leap forward, especially in the area of precision agriculture. Here are 3 tips for growing soybeans that should help you to boost your own yields until the technology is available for you to run your own simulations.

3 tips for growing soybeans

  1. “You can’t improve on things you don’t measure,” says Marion Calmer, an independent on-farm researcher. We couldn’t agree more. To start making improvements to your crops, start measuring. You don’t need to be a scientist to do this. For example, start recording rainfall amount and soil moisture levels, then track growth of your soybeans and see what moisture level they grow best in. Suddenly, you know exactly how much irrigation is needed!
  2. Try reducing the number of soybeans sown. It sounds like it will reduce your yield, but you may actually be surprised at how much improvement you see in soybean bushels when there’s less competition for nutrients.
  3. Finally, start managing residue better. With heavy rains and soil erosion, you can really start to see your nitrogen fertilizer spreading to areas you really wish it wasn’t. To combat this, try planting cover crops around the edges of your field to act somewhat as a nitrogen barrier, absorbing the nutrients before they run off and damage the environment.

Keep an eye on this page, check the comments for further tips and come back next week to see if any precision agriculture advances have finally found some results that can help your soybean yield improvement goals.

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