Researchers Examine the Impact of Nitrogen Levels Under Limited Irrigation Conditions
As farmers face increasing drought conditions, limited irrigation has emerged as a critical strategy to grow crops with less water. This approach, however, raises the question of how other inputs, particularly nitrogen, should be adjusted to optimize crop health and yield. A team of scientists from the Agricultural Research Service (ARS) has delved into this issue to provide guidance to farmers on managing nitrogen levels under limited water conditions.
The Importance of Nitrogen in Crop Growth
Nitrogen is essential for plant growth, playing a pivotal role in photosynthesis and overall plant development. Traditionally, farmers apply nitrogen fertilizers based on the assumption that more fertilizer will compensate for reduced water availability. However, recent research by ARS scientists suggests that this strategy may be flawed.
Research Findings on Nitrogen and Water Interaction
In their study, ARS researchers conducted multiple experiments to understand the effects of varying water and nitrogen levels on crop yields, nitrogen runoff, and greenhouse gas emissions. Surprisingly, the findings indicated that even a slight excess of nitrogen could negatively impact yield. This revelation led researchers to recommend using only the minimum necessary amount of nitrogen when water is limited, particularly given the rising costs of fertilizers.
“You are basically leaving a pool of nitrogen behind that will get into the environment one way or another,” explained Louise Comas, a research plant physiologist at the Water Management and Systems Research Unit in Fort Collins, CO. “It’s a double negative for the producer. They are paying for nitrogen, and as those costs go up, they’re paying for something that’s actually hurting their bottom line.”
Efficient Nitrogen Application Strategies
To minimize nitrogen loss, the researchers experimented with split nitrogen applications—applying fertilizer in multiple small installments over time. This method aligns nitrogen availability with plant demand, reducing the risk of nitrogen loss compared to traditional broadcasting methods, which apply fertilizer early in the growing season when plants are less capable of absorbing it.
“The advantage of doing a split application is that you’re matching to plant demand. Broadcasting typically goes on fairly early, either before planting or when the plants are pretty small, so there’s less ability for the plant to take up the nitrogen, and a larger risk of loss,” noted Catherine Stewart, a research soil scientist at the Soil Management and Sugarbeet Research Unit in Fort Collins, CO.
Environmental and Economic Benefits
The research also highlighted the environmental benefits of appropriately managed nitrogen levels under reduced water conditions. The team observed lower greenhouse gas emissions with deficit irrigation and drip irrigation systems compared to other methods.
Furthermore, the study found a significant increase in nitrogen deep in the soil profile (30-90 cm) under limited water availability. This result emphasizes the importance of accurate fertilizer application to minimize nitrogen losses to the environment and suggests potential revisions to current nitrogen recommendations.
Future Research Directions
Looking ahead, the ARS team aims to better understand the natural soil processes that supply nitrogen to plants. They are particularly interested in how plant root systems, soil microbes, and the interaction of nitrogen and water with carbon contribute to nitrogen availability.
“How plants interact through their root systems, how they support microbes, and how the nitrogen and water interact with the carbon coming in from plants in these processes, is a very important part of this equation,” said Comas. “What we’d like in the end is to fertilize less and to be able to harness those natural processes more.”
Collaborating with researchers at Colorado State University, the team continues to explore these complex interactions to develop more sustainable farming practices.
