Trials conducted as part of the Iowa Nitrogen Initiative have revealed that there is a relatively narrow range of yield that farmers can achieve at the optimum rate of fertilizer. However, the amount of nitrogen required to reach that optimum rate can vary significantly, making it difficult for farmers to predict how much they will get from their soil. Led by Research Team Leader Michael Castellano and Sotirios Archontoulis, the Iowa Nitrogen Initiative aims to determine the best amount of nitrogen for each corn field by collecting data from farms across Iowa. This data will enable growers to improve the precision of fertilizer application rates.
As the leading state in corn production in the United States, Iowa plays a crucial role in the agricultural industry. According to the USDA, corn for grain production in Iowa for 2022 was estimated at 2.48 billion bushels. Castellano highlights the significance of Iowa’s agricultural prowess and emphasizes the need to enhance fertilizer application precision.
To participate in the project, farmers must have access to two common precision agriculture technologies: variable rate fertilizer application and GPS-based yield monitoring. By utilizing historical yield data and identifying areas expected to perform differently, small-scale trials are conducted in specific sections of fields. However, farmers often lack evidence-based guidance on how fertilizer rates should vary when using variable rate application equipment.
Currently, official recommendations for fertilizer rates are broad, leading to wide variations from field to field and year to year. The research team aims to develop models that provide more specific guidance. However, there are challenges in using satellite images and soil sampling to achieve this. Satellite images rely on the genetics and hybrid variety of the crop, making it difficult to calibrate tests for individual hybrids. Soil sampling is also problematic, as the nitrogen supply from the soil is significant and varies each year. Additionally, the increasing use of narrow strip fertilizer applications makes it challenging to obtain accurate and representative soil samples.
Castellano and his team are working to bridge the gap between the advancements made by engineers in precision agriculture and the scientific understanding of agronomists. The Iowa Nitrogen Initiative is currently conducting 270 on-farm trials across 72 different private farming operations. Each trial consists of five different fertilizer rates on replicated plots, providing scientifically robust data from real-world farming conditions.
The trials have confirmed that optimum fertilizer rates can range from 0 to over 300 kilograms per hectare. However, the yields at the optimum rate have a relatively narrow range, ranging from plus 1 ton per hectare to minus 1 ton per hectare. This variability in nitrogen requirements poses a challenge for farmers in determining the optimal amount of fertilizer to apply.
The Iowa Nitrogen Initiative aims to address this issue and reduce nitrogen usage by helping farmers understand when they can apply less fertilizer. Castellano estimates that farmers can reduce fertilizer application by around 30% of the time with the information provided by the initiative. Farmers recognize the importance of this problem, as evidenced by a 400% increase in trials since the project’s inception in 2022.
The initiative has the potential to provide farmers with the tools and information needed to make more informed decisions about fertilizer management. The team is developing three specific tools: updated and dynamic benchmark recommendations for nitrogen rates, anonymized trial data for real-world outcomes, and forecasting and hindcasting tools to estimate ideal rates based on current and past conditions.
These tools will be accessible to farmers through applications on their phones and computers, allowing them to make data-driven decisions about their operations. The initiative is also collaborating with Google, with a team of 10 employees volunteering their time to support the design and engineering of the tools.
Castellano hopes that other states will adopt the Iowa Nitrogen Initiative’s approach, but there are currently no concrete plans for expansion. The potential to save money and reduce environmental nitrogen losses by using the tools is significant. By helping farmers apply the optimal fertilizer rate, the initiative aims to improve nutrient management, increase profitability, and protect natural resources.