Harnessing Residual Soil Nitrogen Following a Dry Season
Amy Timmerman, Extension Educator
Author
11/22/2024
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2
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Description
The 2024 growing season brought drier-than-average conditions to much of Nebraska, impacting crop yields and altering soil nutrient dynamics, especially for rainfed crops.
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- [00:00:00.000]Today's Extension Update is from Amy Timmerman,
- [00:00:03.297]Cropping and Water Extension Educator covering Holt, Boyd,
- [00:00:06.557]Brown, Rock, Keya Paha, and Cherry counties.
- [00:00:09.857]The 2024 growing season brought drier-than-average
- [00:00:12.860]conditions to much of Nebraska, impacting crop yields and
- [00:00:16.067]altering soil nutrient dynamics, especially for rainfed crops.
- [00:00:20.840]During drought, crop growth is reduced, hence nitrogen movement and uptake
- [00:00:25.297]are often restricted, leading to higher-than-normal levels of residual soil nitrogen.
- [00:00:30.302]This can be beneficial for the next growing season as it provides
- [00:00:33.440]readily available nitrogen for the new crop, but it's important to monitor
- [00:00:37.883]soil tests to determine the actual amount of residual nitrogen present.
- [00:00:41.740]As we look toward the 2025 season, this residual nitrogen might offer a
- [00:00:47.240]valuable opportunity to optimize fertilizer planning, enabling cost reductions,
- [00:00:53.120]improved crop yields, and enhanced environmental stewardship.
- [00:00:57.280]Here’s how if your in a dry-affected areas can effectively
- [00:01:01.460]harnessing residual nitrogen for the coming season.
- [00:01:04.200]So why does residual soil nitrogen increases after a dry year?
- [00:01:09.058]Dry conditions limit nitrogen uptake in crops,
- [00:01:12.478]as water is essential for nutrient transport and absorption.
- [00:01:16.278]Without adequate moisture, nitrogen applied through fertilizers
- [00:01:19.206]or naturally present in the soil often remains unused.
- [00:01:23.420]Additionally, drought potentially reduces nitrogen losses from
- [00:01:27.104]leaching and denitrification, allowing residual nitrogen or particularly nitrate
- [00:01:32.844]to accumulate in the soil profile, especially within the root zone.
- [00:01:36.824]Harnessing this residual nitrogen can provide a natural nutrient source for
- [00:01:40.824]crops in the 2025 season, helping reduce the need for additional
- [00:01:44.824]fertilizers, lowering costs, and preserving soil and water quality.
- [00:01:49.200]Thus it is important to soil sample for residual
- [00:01:52.160]nitrogen through various assessments.
- [00:01:55.140]To accurately gauge residual nitrogen levels, soil sampling is essential.
- [00:02:00.120]Sampling the soil allows for a comprehensive
- [00:02:02.860]view of nitrate levels across the soil profile.
- [00:02:05.720]Here’s how soil sampling can help in optimizing nitrogen applications.
- [00:02:10.214]1. Timing of Soil Sample.
- [00:02:13.314]After a dry season, soil sampling is ideally conducted in the spring before planting.
- [00:02:18.900]This timing accounts for any winter nitrogen loss from leaching,
- [00:02:22.914]ensuring a more accurate picture of available nitrogen.
- [00:02:26.540]However, if conditions allow and you prefer a preliminary view,
- [00:02:30.360]fall sampling can be useful — particularly in low-leaching fields.
- [00:02:34.820]2. Depth of Sampling.
- [00:02:37.940]Sampling to 2 or 3 feet is critical, as nitrate can accumulate
- [00:02:41.620]in lower soil layers after leaching from the surface.
- [00:02:45.220]This comprehensive sampling depth provides
- [00:02:48.240]the data needed to calculate an accurate nitrogen credit.
- [00:02:51.380]And finally 3. Using Test Results for Fertilizer Adjustments.
- [00:02:56.080]Soil test results will reveal the available nitrate concentration,
- [00:02:59.547]allowing you to adjust their nitrogen applications accordingly.
- [00:03:03.320]For example, if residual nitrogen levels are high,
- [00:03:06.834]we can reduce the spring nitrogen applications,
- [00:03:09.740]minimizing both costs and potential for nitrate leaching.
- [00:03:14.000]How do we plan for spring nitrogen needs?
- [00:03:17.060]While residual nitrogen after a dry year provides a valuable resource,
- [00:03:20.980]we should approach nitrogen management for the new season with flexibility.
- [00:03:24.809]Use the following guidelines to ensure nitrogen
- [00:03:26.520]applications meet crop needs without excess.
- [00:03:30.220]1. Conduct Spring Soil Sampling.
- [00:03:32.960]Even if you sampled in fall, a spring follow-up test is beneficial.
- [00:03:37.301]This accounts for any nitrogen movement or loss that occurred over winter.
- [00:03:41.740]2. Limit Early-Season Applications.
- [00:03:44.760]Apply only enough nitrogen at planting to meet initial growth needs,
- [00:03:48.500]then follow up with side-dress applications as the crop grows.
- [00:03:52.100]This approach minimizes early nitrogen losses and
- [00:03:55.140]provides nutrients when plants can most efficiently use them.
- [00:03:58.640]And finally 3. Use Decision Support Nitrogen Recommendation Tools.
- [00:04:03.520]The UNL nitrogen calculator, variable rate application,
- [00:04:07.520]the sensor-based technologies can further refine nitrogen applications.
- [00:04:12.700]These tools help distribute nitrogen only where needed,
- [00:04:15.720]maximizing efficiency across variable field conditions.
- [00:04:20.080]So in summary, following a dry season,
- [00:04:22.300]residual soil nitrogen becomes a key resource
- [00:04:25.300]for improving both economic and
- [00:04:26.960]environmental outcomes in the next growing season.
- [00:04:29.460]By measuring and crediting residual nitrogen through soil sampling, adjusting
- [00:04:33.620]fertilizer applications, and adopting strategic nitrogen management practices,
- [00:04:38.100]we can achieve a balanced approach that supports
- [00:04:40.840]crop productivity and minimizes unnecessary fertilizer use.
- [00:04:45.160]Harnessing residual nitrogen is a powerful tool for smarter
- [00:04:48.960]fertilizer planning, ensuring each application maximizes
- [00:04:52.280]benefit while protecting valuable soil and water resources.
- [00:04:56.260]This has been Amy Timmerman with Nebraska Extension.
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