Listed nitrate from agriculture as key source. of local surface and ground waters

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1 Practical Soil Nit trate t Testing and Fertilizer Management Richard Smith Farm Advisor, University of California Cooperative Extension Monterey County, CA

2 New Reality of Growing Cool Season Vegeta ables in Salinas Global fluctuations in fertilizer prices Less public understa anding and sympathy to grower s issues More public pressure e pushing for tighter restrictions in growin ng crops: RWQCB Staff recomm mendations for the Conditional Waiver

3 Listed nitrate from agriculture as key source of pollution of local surface and ground waters

4 Monterey County Crop Notes July/August, 2009

5 Issues Affecting Strategies t to Farm the Adoption of Closer to the Edge May Slow Adoption High value of lettuce Relatively l low cost of nitrogen fertilizer Traditional fertilizer programs (tried and true) May Increase Adoption 2008 Spike in fertilizer prices 2010 Draft Recommendations to the Regional Water Quality Control Board

6 Fertilizer Costs for Romaine Lettuce Six row 80-inch beds * Application At listing in fall lbs N/A Anti crustant 20 lbs N/A Sidedress UN lbs N/A Total Costs/A $424 <3% of production costs *2009 Sample Costs to Produce Romaine Hearts

7 Fertilizer Urea, NH 4+, NO - 3 Crop Residue NH H 4 + NO - 3 Crop Growth Organic Matter lbs N/A Nitrate Losses Runoff Ground Nitrous Water Oxide

8 Other Issues Lettuce is a relatively shallow rooted crop that can be an ineffic cient user of fertilizer N High nitrogen uptake over 30 days (post thinning to harvest) Nitrate t is highly hl leach hable Irrigation efficiency is key for reducing nitrate leaching Lack of good deep ro ooted winter rotations that can utilize residu ual nitrogen

9 Conducted five com mmercial scale trials with Mike Cahn over the last two years We measured the im mpact of irrigation and fertilizer application on nitrate-n nutrition of the crop Through these trials I became a grower and struggled with many of the issues that you might deal with in making fertilizer decisions based on measurements of residual soil nitrate

10 Accounting for Residual Nitrogen

11 Residual Nitrate-Nit trogen in Soil Over Growing Season (tw wo crops of lettuce) Beginning of winter fallow period Plant 2 nd crop Harvest Harvest 0 ppm hreshold Plant 1 st crop Months Smith and Schulbach, 1996

12 Nitrogen Upt take Patterns Lettuce at thinning (a app. 30 days after planting) contained only 5-8 lbs N/A Relying on the nitrate quick test gave good confidence in the need for fertilizer needs at that growth stage We were able to redu uce and delay initial nitrogen applications without jeopardizing yields

13 2008 Trial No. 1 Second Crop lbs N acre Delayed and 150 reduced first 100 sidedress N application 50 Fertilizer applied Standard Fertilizer applied BMP N Uptake Standard N uptake BMP Given levels of residual nitrate, we probably could have eliminated all NEED ENGLISH UNITS sidedress applications but I chose the cautious route of simply cutting back on nitrogen applications Days After Plan nting

14 Cored Head Lettuce Yield lbs s/a ,649 55,506 58, inch beds x length of field Standard BMP Untreated

15 2009 Trial No. 1 First Crop N applied Standard N applied BMP Biomass N Standa ard Biomass N BMP lb N Acre Reduced the rate of the fist sidedress application Days After G erm ination W ater

16 2009 Tri ial No. 1 Treatment Fertilizer N lbs/a Total N Commercial Applied Yield CFR Thinningi Early Heading Lbs/A Lbs/A Rosette Grower BMP , ,999

17 Struggling with Whether to or Not to Fertilizer Trial No. 2 in 2009 ha ad lower N levels in one part of the field May have been due to irrigation uniformity issues (more water being applied closer to the valve and possib bly more leaching as a result)

18 2009 Trial No. 2 - Second Crop Nitra ate (mg N/kg soil) Red Grower Blue - BMP /10 8/21 8/26 9/ /3 9/8 9/11 9/16 9/21 Date

19 Getting Started with Managing N Fertilization Bas sed on the Quick Tes sts Pick fields and do so ome trials in 2010 Start with a 12 or 16 bed wide strip so that you can get har rvest data Get someone that is conscientious about taking good sample s and that can get the information to the d ecision make in a timely fashion

20 Getting Started with Managing N Fertilization Bas sed on the Quick Tes sts The key will be build ding a decision making structure int to your operation so that the information can be efficiently incorporated into yo our daily operations It may be that the cu urrent pest management model (PCA/Grower/Forma an) may be the way to effectively handle th hese big decisions

21 Other Low Hanging Fruit Fall applied nitrog en to fallow beds

22 Fate of Fall Ap plied Nitrogen to Fallow wbeds Mineral Nitrogen in Top Foot of Soil Winter Winter Storm >2.0 inches in 5 days 60 (mg N/kg soil) NO3+NH

23 Fall applied nitrog gen to fallow beds Applying nitrogen in the fall is waste of money and should me minimized as much as possible

24 Loss of Nitrate- N by Leaching During the Irrig gation Season One Irrigation Event 2 7D Days After Planting Treatment Applied water inch Percolation inch Standard BMP Nitrate-N Concentration in Leachate - ppm Nitrogen loss Lbs N/A Value of leached nitrogen $ $8

25 How to Pay for th e Expense of Soil Testing and Management Over five trials we saved an average of $32/crop in reduce ed sidedress nitrogen fertilizer applicatio ons Fall applied fertiliz zer can be expensive Reductions in leac ching can save $$ The AWEP Progra am may provide a means to get start ted in nitrate testing

26 Sum mary Over five commercia al trials we reduced nitrogen fertilizer ap plications by 55 lbs/crop In four of five trials t he yields of the BMP treatments were com mparable with the standard practice These trials point to ways that growers can farm with a leane er nitrogen budget without jeopardizing gy yield