Next Meeting is Friday, October 31
By Jane Sooby
At its October 22 Working Group Meeting, the Second Statewide Agricultural Expert Panel made progress in assigning each of their “charge questions” to a two-person team, clarified the timeline for completion of their final report, and continued in-depth discussion of questions 1 and 2, which, in sum, ask if there are enough data to set crop-specific nitrogen-related limits and what series of increasingly protective limits could be set now.
Expert Panel Team Assignments
Because of California’s strict public meetings law, known as the Bagley-Keene Act, all work of the Ag Expert Panel must be conducted at “open and noticed” meetings that have been announced to the public in advance. The one exception is for a committee of less than three persons, which may convene without public notice–thus the two-person teams. In addition, Bagley-Keene prohibits “serial meetings” of more than two panelists, therefore the teams cannot be “mixed and matched.”
Expert Panel’s Timeline–Second Plenary Meeting This Friday
The panel reviewed the timeline of upcoming meetings and for completing their final report. The panel’s Second Plenary meeting will be this Friday, October 31, from 10 am – 4 pm at the Cal EPA Building in Sacramento and online. Meetings are presented in both English and Spanish. The meeting will feature a presentation from California Dept. of Food and Agriculture’s Fertilizer Research and Education Program (FREP) and a presentation on the State Water Board’s regulatory processes, as well as panelist discussion and public comment.
Pre-registration is required for remote attendance and to offer public comment: click here for the agenda, which includes information on how to comment, and here to register to participate remotely. Registration for subsequent expert panel meetings has not yet opened.
State Water Board staff noted that a draft report would need to be open for public comment for 30 days before the expert panel finalizes its report. Panelists discussed modifying the timeline and staff offered to present a revised timeline to them at the Oct. 31 meeting.
Expert Panel Deliberations on Questions 1 and 2
Targets and Limits
The majority of the meeting was devoted to continued discussion of nitrogen (N) targets and limits and various nutrient management challenges. Panelists began by commenting on a summary of their initial recommendations on questions 1 and 2 that was prepared by State Water Board staff based on panelists’ input (available through the panel’s Table of Documents).
Richard Smith stated that it’s “premature” to discuss setting hard limits. Smith noted that the amount of N applied will depend on many factors including residual N from the previous crop, N in irrigation water, and mineralized N. He suggested that there should be crop-specific A-R targets for growers to see how close they can get to those targets by using water-protective practices.
Ngodoo Atume requested that staff provide the intended definition of “limits” as used in question 1 and suggested that the panel consider crop fertilization guidelines published by FREP. She also expressed interest in setting crop-specific application limits to prevent over-application of N.
Expert Panel Chair Daniel Geisseler cited an operational benchmark set forth in the 2012 Harter and Lund report that is region-specific and dependent on groundwater recharge and is not crop-specific.
Thomas Harter agreed with Smith that there is no basis for crop-specific limits and that instead limits should be area-based and that, from a hydrological perspective, targets or limits are only meaningful for areas of 40-160 acres.
Michael Cahn noted that one challenge in setting crop-specific application limits is N carryover from the previous crop, which would influence the amount of N needed to grow the subsequent crop. He also noted that the regulations should apply to operations that have surface discharges including nurseries, crops grown on impermeable surfaces, crops grown in substrate, or fields that utilize tile drainage.
Cahn and Harter both acknowledged that crop-specific reporting and perhaps even targets are important at the same time that thresholds should be set for larger physical areas.
Ali Montazar commented that avocado is a crop that takes 1.5 years to produce, so any targets or limits must be based on a minimum 3-year average.
Smith said, “If growers are faced with tougher targets, it will incentivize creativity on their parts.”
Need for Ongoing Outreach and Education
Hannah Waterhouse expressed that more investment in education and outreach will be necessary for agricultural orders to be effective in reducing N contamination of groundwater, a theme echoed by other panel members. Geisseler also noted that stronger incentives to improve nutrient management may be necessary.
Crop Consultant’s Perspective
Eric Morgan of Soil Health Lab joined the meeting at the request of the panelists to describe his approach for making crop fertilization recommendations. Morgan stated that his work is based on the research done by Richard Smith and Tim Hartz of University of California Cooperative Extension (UCCE) and thanked Smith for his guidance and support.
Morgan described his lab’s soil testing regime that uses intensive soil nitrate testing combined with ammonium analysis to “groundtruth” the nitrate readings. For a broccoli or cauliflower crop, he will sample soil from the first foot then from the second foot through the same hole. If 200 lb N/acre is still present from the previous crop, he would advise not to apply N because the broccoli and cauliflower have deep roots that can pick up the residual N.
Morgan observed that he cut a grower’s fertility budget in half, from $7 million to $3.5 million, using this strategy. Morgan stated that the farm he worked with made a lettuce crop on 20 units of applied N. “When you get 300 pounds of broccoli biomass and only remove 80 pounds through harvest, it is plant-available nitrogen,” said Morgan. “Then it’s a matter of irrigation management so you can get it to stay so the next crop can take it up. Rainfall is the wild card in the system.”
Morgan suggested focusing grower education on when crop nutrient takeup actually occurs, stating that the data don’t support the mindset of applying greater levels of N upfront. “Anyone applying 60-80 pounds of nitrogen at first sidedress will lose 80% of that, period,” he said.
He observed that even when soil N levels have been managed well throughout the year, soil N can increase again after working the ground in fall. “That winter wet period, after your last crop in fall, you need to make sure that you’re not carrying over residual N and if you are, that’s when you go with the cover crop,” he said.
Morgan advocated for taking a regenerative approach. “We think about feeding the plant but we need to focus on the soil first,” he said. “Compost and cover crops need to be incentivized. They are soil food and need to be incentivized regardless of regulation.”
Morgan said that he doesn’t think long-term improvements in N management will come from intensive soil sampling but from technology such as the TerraBlaster, a sensor integrated into a planter or toolbar that uses NASA-developed spectroscopy to measure soil nutrients as the tractor drives across the field. Morgan stated, “Growers like to adopt technology that creates ROI [return on investment]. … Once a grower sees a ROI, they will continue to use it.”
N Carryover from Cover Crop
Smith noted that the first agricultural expert panel didn’t place cover crops on the N removed (R) side of the equation because they didn’t think it was a removal. Smith said that he thinks of N from cover crops as a transfer of N from the fall-winter season to the next cropping season and asked Morgan if he picked up a signal of cover crop N mineralization in the subsequent crop. Morgan replied that a minimum of 80 lb N/acre from a fall cover crop can be detected “every time,” often at the second sidedress interval with the exact timing of its appearance depending on many factors including soil temperature and field operations.
Montazar presented data from a trial in the desert showing that ⅔ of the nitrate from the previous winter lettuce crop was lost from fallow fields due to the summer leaching performed by growers in the desert to push salts beneath the root zone. This N loss was reversed by growing a summer sudangrass cover crop. Montazar also commented on the challenge of managing N in sandy soils.
N Leaching Risk from Organic Compared to Conventional Management
Smith referred to the discount factor for organic fertilizers in the Central Coast region’s Ag Order 4.0 and asked Morgan if an organic farm has the same level of N leaching risk as a conventional farm. Morgan replied that because organic fertilizers are so much more expensive than conventional, organic growers are less likely to over-apply.
Utility of the A-R metric
Panelists expressed general consensus that the metric N applied (A) minus N removed (R) is a solid metric that is useful in helping growers comprehend that fertilizer not used by the crop poses a risk of leaching nitrates into groundwater. Harter also advocated that a model such as CV-SWAT (Central Valley-Soil Water Assessment Tool) could be used to estimate leaching risk for township-level analysis, based on reported A and R values combined with other factors in the model such as soil texture. Atume pointed out that from a public health perspective, it may be difficult to reach drinking water standards using A-R but that it’s a better metric than A/R.
Smith commented that the Central Coast region’s Ag Order 4.0 “did an excellent job” by including discount factors in A for compost and organic fertilizer and a credit in R for N-scavenging cover crops. He also noted the RTREAT credit for growers that use a bioreactor to remove nitrates from runoff. He pointed out that nitrous oxide losses from fields are not captured by these factors and suggested that the expert panel process be revisited every few years to take into consideration emerging data.
“We Need an Earnest Effort”
As the discussion was winding down, Harter noted that, while it may now be impossible to achieve an A-R of 50 lb N/acre in the Central Coast region, the panel wants to see an “earnest and judicious effort by growers.” Smith echoed this, saying, “In all honesty, it’s been spotty in that regard. If we can get everybody using the practices we have now, I think we might surprise ourselves. … I don’t know that it would take 15 or 20 years. We want to do it quicker.”
Second Statewide Agricultural Expert Panel Members
- Ngodoo Atume, SGMA Technical Assistance for Small Farms Coordinator, University of California Sustainable Agriculture Research and Education Program
- Michael Cahn, Irrigation and Water Resource Advisor, University of California Cooperative Extension Monterey County
- Ruth Dalquist-Willard, Interim Director, University of California Sustainable Agriculture Research and Education Program
- Daniel Geisseler, Assistant Cooperative Extension Specialist, Department of Land, Air and Water Resources, University of California Davis
- Thomas Harter, Distinguished Professor of Subsurface Hydrology, University of California Davis
- Ali Montazar, Irrigation and Water Management Advisor, University of California Cooperative Extension Imperial County
- Richard Smith, Vegetable Crop Production & Weed Science Farm Advisor, University of California Cooperative Extension Monterey County – Emeritus
- Hannah Waterhouse, Assistant Professor of Agroecology and Watershed Ecology, Environmental Studies Department, University of California Santa Cruz
