Nitrogen (N) is part of a balanced, natural cycle in the environment among the atmosphere, soil, plants, animals, and water. Nitrogen is the most important element needed by crops, and we often add nitrogen fertilizer to optimize crop productivity. Nitrogen use in agricultural systems must be reported for regulatory compliance under the Irrigated Lands Regulatory Program and the Dairy Order to help ensure that a greater fraction of the applied N is recovered in the harvested crop and not lost to the environment. Nitrogen management gives consideration to the four R's:

• Right source: selecting the fertilizer source that matches the crop need and minimizes losses,
• Right rate: applying the right amount based on crop need and nutrient availability through other sources,
• Right time: applying the nutrient when the crop can use it,
• Right place: fertilizer placement that optimizes the crop's ability to use it.

The four R's address management considerations (e.g. fertilizer program, irrigation), but site characteristics (e.g. soil, cropping system, weather conditions) also influence N recovery in the crop. Also important to improving crop N recovery is understanding barriers to adopting best management practices, such as costs or risks to crop quality or yield.

While the four R's articulate four principles for N management, the N cycle in cropping systems is complicated. Nitrogen can be introduced and lost by various paths. We generally add N with organic matter amendments – such as crop residues, compost, or manure – or with fertilizer. While organic matter amendments must be mineralized before the N is available for plant uptake, fertilizer N is readily available for plants to use. That said, plants generally take up N at different stages during their life cycle, and there is a risk for N loss if the N is applied or becomes available when the plants do not need it.

Technologies have been developed to mitigate N losses from cropping systems. These technologies are collectively known as enhanced efficiency fertilizers (EFF) and include additives, physical barriers, and chemical formulations that stop, slow down, or decrease fertilizer losses. Nitrogen stabilizers are one example and are fertilizer additives intended to improve crop N use efficiency and reduce N losses to the environment by interrupting the microbial processes that change N to its plant-available forms. We developed a trial to evaluate two N stabilizer products with the objective of determining whether the treatments improved corn silage yield or plant N status compared to fertilizer alone. We did not attempt to measure N losses from the system (e.g. leaching, denitrification), as these are very challenging to quantify.

The trial took place in San Joaquin County on a DeVries sandy loam soil. A description of the methods can be found in the full report. Sidedress fertilizer application occurred on June 21, 2018 and provided approximately 105 lbs N per acre (UAN 32). Four treatments were applied at sidedress, when plants were at V3-4 stage of development (Figure 1). The N stabilizers were applied at the label rates, and the treatments were: 1) Vindicate (Corteva Agriscience) at 35 fluid ounces per acre, 2) Agrotain Plus (Koch Agronomic Services) at 3 pounds per acre, 3) combination of Vindicate and Agrotain Plus at aforementioned rates, and 4) fertilizer-only, no stabilizer product (“untreated”). Treatments were randomly applied in three replicate blocks. Aside from the treatments, the trial was managed by the grower in the same manner as the field.

We evaluated soil N status, plant N status, and silage yield. Soil results are available in the full report. There were no statistically significant differences in plant N status or yield (Table 1). Mid-season (i.e. silking, R1) leaf N averaged 2.88 percent across treatments, and aboveground biomass N at harvest averaged 1.12 percent. At mid-season, leaf N from 2.7 to 3.5 percent indicates that the plant had sufficient N to carry the crop to harvest, and at harvest, aboveground biomass N from 1.0 to 1.2 percent indicates that the N fertilization program was adequate for maximizing yield. Thus, it appears that the trial was not deficient in N. Calculated to 30 percent dry matter, average yield across treatments was 38.8 tons/acre, and dry matter was 35 percent. There was a trend for the two treatments with Vindicate to have higher N removed than the two treatments without it, but the difference was not statistically significant.

In summary, N is part of a balanced, natural cycle in the environment and is the most important nutrient in cropping systems. Giving consideration to N management will help ensure that a greater fraction of the applied N is recovered in the harvested crop and not lost to the environment, and keeps growers in regulatory compliance. Enhanced Efficiency Fertilizers, such as N stabilizers, have been shown to improve crop yield in regions like the Midwest and the Northeast, and may help to mitigate N losses to the environment. In our trial, we evaluated the efficacy of N stabilizer products for improvements in corn silage yield or plant N status compared to fertilizer alone. Under the management and environmental conditions of this trial, we found no differences in yield or plant N status; however, plant and soil tests indicated that N was not limiting in the trial. If N was lost from the system, the loss was not large enough to result in N limitation in the control. Future study should test these products using different N sources and N rates (e.g. grower rate versus grower rate minus 50 lbs N/acre). It may be possible to reduce the fertilizer N rate without sacrificing yield.

This trial was made possible with the generous cooperation of Hank Van Exel and Van Exel Farms; Carl Bannon and Steven Colbert (Corteva Agriscience); Brad Schrenk (Simplot); Eric Ellison (Koch Agronomic Services); Nick Clark and Daniel Geisseler (UCCE); and Shirley Alvarez, Cheryl Gartner, and Dan Rivers (UCCE technicians). An in-depth report is available from my website. Please don't hesitate to contact me with comments or questions.

On Thursday, January 17th, I hosted the annual SJC and Delta Field Crops Meeting in Stockton, CA. I want to thank everyone who attended and provided feedback on the meeting. Your evaluations are critical and inform Cooperative Extension outreach efforts! The presentations from that meeting have now been posted to my website. I encourage you to reach out to the presenters with questions. Also available from my website are full reports of local research trials, including the Delta field corn variety trial. I will make an announcement here on the blog when new reports are available.

UC statewide specialists make their research results available through the Agronomy Research and Information Center (RIC) website. Please check the RIC for information on statewide trials in small grains, alfalfa, dry beans, and other field crops. 

We hope you will find this information useful, and we hope you will share your feedback with us so that we may best serve your interests for research and outreach.

Happy New Year! We are entering "meeting season". The new year brings several opportunities for continuing education, including UC Cooperative Extension grower meetings and the California Plant and Soil Conference. Please see below for more information. 

1. UC Cooperative Extension will host the SJC and Delta Field Crops Meeting on Thursday, January 17, 2019 from 8:00am to 12:00pm. The meeting location is the Cabral Agricultural Center in Stockton (2101 E. Earhart Ave., Stockton, CA 95206). Please see this previous post for the agenda or open the attachment below. We will offer continuing education credits for DPR licensing (2), CCA certification (3), and nitrogen management (1.5). Light refreshments will be provided.

2. UC Cooperative Extension will host five meetings for rice growers. The meeting details are as follows:

Richvale: Thursday, January 17, 8:30am, Evangelical Church, 5219 Church St., Richvale

Glenn: Thursday, January 17, 1:30pm, Glenn Pheasant Hall, 1522 Hwy. 45, south of Glenn

Colusa: Friday, January 18, 8:30am, Colusa Casino Resort, 3770 Hwy 45, Colusa

Marysville: Friday, January 18, 1:30pm, Yuba County Government Center, 915 8th St., Marysville

Woodland: Tuesday, January 22, 8:30am, Cracchiolos Banquet Hall, 1320 E. Main Street, Woodland

Time: Doors open at 8:00am, and meetings start at 8:30am at Richvale, Colusa, and Woodland. Doors open at 1:00pm, and meetings start at 1:30 pm at Glenn and Marysville. DPR and CCA continuing education credits will be offered. For the program, please visit the UC Rice Blog.

3. The California Chapter of the American Society of Agronomy will hold its annual Plant and Soil Conference on February 6-7 in Fresno, California. Program information and registration are available from the conference website. Session topics include water management, climate smart agriculture, irrigation efficiency, and pest management. DPR licensing, CCA certification, and nitrogen management continuing education credits will be offered.

UC Cooperative Extension will host the SJC and Delta Field Crops Meeting on Thursday, January 17, 2019 from 8:00am to 12:00pm. The meeting location is the Cabral Agricultural Center in Stockton (2101 E. Earhart Ave., Stockton, CA 95206). Coffee and light refreshments will be provided.

The agenda is attached at the bottom of this post, and is as follows:

8:00am     Doors Open and Sign In

8:15am     Nitrogen Stabilizers in Silage Corn, Michelle Leinfelder-Miles, UCCE San Joaquin/Delta Counties

8:45am     Measuring the Interaction between N Demand and Water Use in Irrigated Corn, Mark Lundy, UC Davis

9:15am     Regulatory Update, Tim Pelican, San Joaquin County Agricultural Commissioner

9:30am     Fish Friendly Farming Program for the Delta, Laurel Marcus, California Land Stewardship Institute

9:45am     Break

10:00am   Agronomic Strategies to Improve Alfalfa Pest Management, Dan Putnam, UC Davis

10:30am   Opportunities for Automation and Optimization of Surface Irrigation Systems, Khaled Bali, UCCE, Kearney Research and Extension Center

11:00am   Italian Ryegrass Management in California Wheat Cropping Systems, Mariano Galla, UCCE, Glenn/Butte/Tehama Counties

11:30am   Managing for Soil Health and Soil Salinity, Michelle Leinfelder-Miles, UCCE, San Joaquin/Delta Counties

12:00pm   Evaluations and Adjourn

We have submitted applications for continuing education for pesticide licensing and certified crop advisors. We have also submitted an application for nitrogen management continuing education, which would help to satisfy growers' continuing education requirement for the Irrigated Lands Program. Applications are pending.

Our programs are open to all potential participants. If you require special accommodations, please contact UCCE San Joaquin County at 209-953-6100. Thank you, and hope to see you at the meeting.