Turn Irrigation into a Nitrogen-Saving Advantage

As we’ve discussed in previous articles, having the ability to supply water to your crop through irrigation is a blessing in semi-arid environments.  It also comes with a lot of work and responsibility.  Irrigating can me the difference between a thriving crop and at the very least, a stressed one, and at worst, no crop. 

Irrigation and nitrogen management go hand in hand.  Water can have effects on nitrogen availability to the crop: Too much moisture and N can be lost through denitrification and leaching if it is in the nitrate form.  Too little moisture and it becomes difficult to move nitrate to the roots for uptake. 

The “goldilocks” soil moisture is at Field Capacity, a situation where the soil is moist but not dripping water freely.  This is a soil moisture at which mineralization (conversion of organic nitrogen to inorganic ammonium nitrogen) and nitrification (conversion of ammonium to nitrate) is maximized, and risk of nitrogen loss is minimized.  There is a sufficient amount of air in the soil, allowing aerobic bacteria and fungi to do their work. 

Irrigation enables farmers to keep their soil in that “goldilocks” range longer.  In between irrigation events the soil moisture may start to drop; this isn’t necessarily a bad thing, especially during vegetative growth; roots will start going deeper in search of more moisture and end up picking up lost nutrients along the way.  But timely irrigation (or rain) is needed to keep things on track. 

Irrigation also allows for later-season delivery of nitrogen through fertigation.  By injecting metered quantities of UAN fertilizer, nitrogen can soak into the soil with the water and become quickly available to the plant.  This spoon-feeding effect allows for smaller quantities of nitrogen to be applied and taken up by the plant in short time.  Irrigation water may often contain nitrates as well, unfortunately often from over-applications of nitrogen in the past.  However, this nitrate can be credited and used by the plant during the growing season. 

The main concern with nitrogen and irrigation, especially during crucial periods of mid-late vegetative growth and grain fill, is a situation where too much water is applied, leaching nitrogen deeper into the soil profile and beyond the ability of roots to take it up.  This could occur with overwatering, either from irrigation or through unexpected high intensity rain storms.  While these can be a blessing to reduce the load on irrigation, they can cause leaching of nitrate-nitrogen unexpectedly. 

What can be done about this?  Of course, seasoned irrigation farmers watch the weather forecast, estimate evapotranspiration potential, and monitor soil moisture, either through traditional soil probe methods or newer satellite-based approaches.  Either way, knowing how much the crop needs, how much is available, and when and how much can be delivered to it is crucial to balancing the water and nitrogen needs of the crop during the growing season. 

Sentinel Weather Information Graphs

By utilizing Sentinel All-N, powered by powerful soil moisture insights from Nave Analytics, today’s irrigation farmer can control their nitrogen and water inputs better than any time before.  These tools help the farmer apply the right amount of both crucial inputs to maximize net profit and reduce overapplication. 

To learn more, see your local Sentinel Certified Service Provider today.