Nitrogen management in annual vegetable crops

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1 University of California Nitrogen Management Training for Certified Crop Advisers Nitrogen management in annual vegetable crops

2 The Water Quality Control Board will: institute nitrogen use reporting for agriculture use that information to estimate potential environmental N loading through the use of mass balance calculations Basic assumption of a nitrogen mass balance approach: N applied to a field but not removed in harvested products is at risk of eventually leaving the field in gaseous or liquid form

3 Volatilization Denitrification Fertilizer Organic amendments Irrigation water NO 3 -N Harvested products Leaching Or runoff

4 Volatilization losses can be significant for: Anhydrous ammonia, especially water-run Topdressed urea Animal manure Losses up to 30% of applied N are possible Volatilization losses to the atmosphere are environmentally damaging when N is deposited in wild lands

5 Denitrification losses can be significant with: Frequent, saturating irrigation High soil nitrate level Denitrification is usually a minor part of an N balance in San Joaquin Valley cropping, although nitrous oxide (N 2 O) loss is an air quality concern

6 What about long-term soil N storage? Short-term root zone NO 3 -N carryover is common Significant long-term soil N sequestration is uncommon, and probably limited to conservation tillage management

7 Nitrate leaching losses are likely to be significant where N loading (from all sources) substantially exceeds crop N removal

8 Bottom line: Within some level of uncertainty, evaluating agricultural N management on a mass balance basis (inputs outputs) does estimate potential environmental N loading

9 Bottom line: Within some level of uncertainty, evaluating agricultural N management on a mass balance basis (inputs outputs) does estimate potential environmental N loading At similar yield levels, a grower applying substantially more N than his neighbor is probably releasing more N to the environment over time

10 N management in a more regulated world: Some crops, and some production systems, will get more scrutiny than others To keep under the regulatory radar, strategic N management will be needed - evaluate N requirement on a field-specific basis, making use of non- fertilizer N sources

11 Nitrogen planning exercise:

12 Nitrogen planning exercise:

13 N fertilization scenarios There is not one right answer!!!

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15 Annual vegetable crops show a characteristic growth pattern

16 N uptake follows the same pattern N uptake by processing tomato: Data from four high-yield fields

17 N uptake follows the same pattern N uptake by cantaloupe: 3 high-yield hybrid cantaloupe fields

18 Fruiting crops have a characteristic pattern of N partitioning N partitioning by processing tomato: General rule: In fruiting crops, fruit typically represents 50-70% of total crop N uptake

19 Vegetative crops typically harvest near peak N uptake rate Fruiting crops typically harvest after peak N uptake rate

20 Typical peak N uptake rates for vegetable crops: 3-4 lb / acre / day in cool conditions 4-6 lb / acre / day in warm conditions

21 Individual fields can differ widely in nutrient uptake High yield tomato fields: Crop uptake (lb/acre) N P 2 O 5 K 2 O Field Field Field Luxury uptake - nutrient uptake that neither increases yield nor product quality - often 10-20% of the total crop N uptake

22 Accounting for yield effects: lb N / ton Crop type of fresh weight Fruiting Cantaloupe 3.0 Honeydew 2.1 Pepper 3.2 Tomato 3.1 watermelon 2.0 Vegetative Broccoli 11.6 Lettuce 4.0 Source: USDA nutrient removal calculator ( )

23 In a more regulated world, we need think strategically about N management Strategic N management requires attention to field-specific characteristics

24 Field-specific N management : Develop a reasonable N fertilization template, then modify it for: Residual soil NO 3 -N Soil N mineralization potential Irrigation water NO 3 -N In-season plant analysis???

25 What is a reasonable N template? N management in lettuce fields: Ave N application Ave N uptake Since N deficiency in commercial fields is very uncommon, seasonal N rates coastal lettuce field survey on the lower end of the normal range should be sufficient in most cases

26 Field-specific N management : Post-establishment soil NO 3 -N - often called Pre-sidedress Soil Nitrate Testing (PSNT) Often the most important field-specific modification

27 Why is post-establishment soil NO 3 -N sampling so important? It integrates the main factors influencing soil N mineralization (rapid N mineralization from residues and amendments has already taken place) The measurement is taken after crop establishment, when additional leaching should be controllable (given good irrigation management)

28 How variable is post-establishment soil NO 3 -N? Processing tomato fields, sampled post-transplanting: Differences among fields are large (PPM x 3.8 = approximate lb NO 3 -N/acre in each foot of depth) NO 3 -N in the top foot typically correlates well with 2 nd foot

29 How variable is post-establishment soil NO 3 -N? Processing tomato fields, sampled post-establishment: 35 lb N/acre 192 lb N/acre 110 lb N/acre

30 How to calculate a fertilizer credit for residual soil NO 3 -N? There is no right answer for all situations to what depth? what about spatial variability? Possible approaches: Credit a fraction of residual N (50-75%?) Credit all residual N above a threshold (5 PPM?)

31 Contribution of soil N mineralization: Between 5-6% of soil organic matter is organic N You can generally count on net mineralization of at least 1-2% of soil organic N content during a vegetable crop season Example: Top 12 inches of soil weighs 3,800,000 lb/acre 2,000 lb organic N per % organic matter lb N/acre per % soil organic matter Caution: N mineralization behavior of very high organic matter soils may be different

32 Contribution of prior crop residue: wheat tomato broccoli Typical residue N content (kg/ha) Residue %N In general, more than 90 days after soil incorporation, crop residue N behaves similarly to that of existing soil organic N

33 Field-specific N management : Irrigation water NO 3 -N 2013 irrigation water NO 3 -N uptake efficiency trial continuously injected varying levels of NO 3 -N from 0-40 PPM measured lettuce biomass N at harvest

34 Results: Fertilized control Levels of irrigation water NO 3 -N Bottom line: NO 3 -N in irrigation water behaves like fertilizer

35 Tissue N monitoring for annual crops: Leaf total N overall crop N status Petiole NO 3 -N NO 3 -N taken up but not yet assimilated into organic compounds

36 Leaf total N monitoring : provides a reliable indicator of plant N status changes relatively slowly over time is poorly correlated with soil NO 3 -N availability early in the season when N uptake is slow, so it has limited value in early season fertilization decisions

37 Advantages of leaf total N : changes slowly 2007 UCD processing tomato trial lb N/acre Growth stage Total plant N content N uptake/day Daily uptake as % of biomass N Early bloom Mid fruit set First red fruit Leaf total N substantially above the sufficiency level indicates sufficient biomass N to accommodate 7+ days of crop growth

38 Limitation of leaf total N: leaf N doesn t reflect soil N availability until the high N uptake period, so it is a flawed guide to early season N fertilizer need Leaf N data from 20 processing tomato fields : Red symbols from fields in which N availability limited yield Green symbols from fields with adequate N to maximize yield Sufficiency level Early flowering Full bloom First red fruit

39 Advantages of petiole NO 3 -N : easily / quickly measured Disadvantages of petiole NO 3 -N : Environmental factors can affect results more than soil N availability

40 Limitations of petiole NO 3 -N : Much more variable than leaf total N 2009 Lettuce N trials, cupping stage: Average C.V = 13% Average C.V. = 46%

41 How much can environmental factors influence petiole NO 3 -N? Six sprinkler-irrigated coastal broccoli and cauliflower fields, sampled every 2 days over a sprinkler irrigation cycle :

42 Bottom line on plant tissue testing : whole leaf sampling gives a good snapshot of current crop N status but, if it is in the adequate range, does not project forward more than 7-10 days to predict whether additional N application is required maintaining high petiole NO 3 -N throughout the season should ensure crop nitrogen sufficiency; however, because environmental conditions can cause low petiole NO 3 -N even when soil NO 3 -N is adequate, using petiole analysis to determine fertigation requirements often leads to unnecessary fertilization

43 Nitrogen management: Agronomy vs. regulatory reporting The regulatory interest in N use reporting is to estimate the potential for environmental N loading The role of a CCA will be to help clients maintain productivity while minimizing unnecessary N application

44 Example N reporting form: CROP NITROGEN DEMAND Crop Expected yield (lbs of production/ acre) Crop nitrogen 'need' to meet expected yield (lbs of Nitrogen per acre)??? PROTOTYPE NITROGEN BUDGET WORKSHEET Total N applied to field (lbs/ac) Dry & Liquid Fertilizers Foliar N fertilizers Other N fertilizers Available N from recent organic amendments TOTAL N APPLIED (per acre) Soil Nitrogen Credits Residual soil NO3-N In-season soil organic N mineralization NO3-N in irrigation water TOTAL N CREDITS (per acre) Total N Credits and Applications: Crop N needs: Balance Ratio Recommended N

45 CROP NITROGEN DEMAND Crop PROTOTYPE NITROGEN BUDGET WORKSHEET Recommended N Expected yield (lbs of production/ acre) Crop nitrogen 'need' to meet expected yield (lbs of Nitrogen per acre) Total N applied to field (lbs/ac) Dry & Liquid Fertilizers Foliar N fertilizers Other N fertilizers Available N from recent organic amendments TOTAL N APPLIED (per acre) Soil Nitrogen Credits Residual soil NO3-N In-season soil organic N mineralization NO3-N in irrigation water TOTAL N CREDITS (per acre) Total N Credits and Applications: Crop N needs: Balance Ratio???

46 CROP NITROGEN DEMAND Crop Expected yield (lbs of production/ acre) Crop nitrogen 'need' to meet expected yield (lbs of Nitrogen per acre) PROTOTYPE NITROGEN BUDGET WORKSHEET Total N applied to field (lbs/ac) Dry & Liquid Fertilizers Foliar N fertilizers Other N fertilizers Available N from recent organic amendments TOTAL N APPLIED (per acre) Recommended N Soil Nitrogen Credits Residual soil NO3-N??? In-season soil organic N mineralization??? NO3-N in irrigation water??? TOTAL N CREDITS (per acre) Total N Credits and Applications: Crop N needs: Balance Ratio

47 CROP NITROGEN DEMAND Crop Expected yield (lbs of production/ acre) Crop nitrogen 'need' to meet expected yield (lbs of Nitrogen per acre) PROTOTYPE NITROGEN BUDGET WORKSHEET Total N applied to field (lbs/ac) Dry & Liquid Fertilizers Foliar N fertilizers Other N fertilizers Available N from recent organic amendments TOTAL N APPLIED (per acre) Recommended N Soil Nitrogen Credits Residual soil NO3-N In-season soil organic N mineralization NO3-N in irrigation water TOTAL N CREDITS (per acre) Total N Credits and Applications: Crop N needs: Balance Ratio

48 Crop example: Lettuce CROP NITROGEN DEMAND PROTOTYPE NITROGEN BUDGET WORKSHEET Crop lettuce Expected yield (lbs of production/ acre) 48,000 Crop nitrogen 'need' to meet expected yield (lbs of Nitrogen per acre) 140 Total N applied to field (lbs/ac) Dry & Liquid Fertilizers Foliar N fertilizers Other N fertilizers Available N from recent organic amendments TOTAL N APPLIED (per acre) Soil Nitrogen Credits Residual soil NO3-N In-season soil organic N mineralization NO3-N in irrigation water TOTAL N CREDITS (per acre) Total N Credits and Applications: Crop N needs: Balance Ratio Recommended N

49 Crop example: Lettuce CROP NITROGEN DEMAND PROTOTYPE NITROGEN BUDGET WORKSHEET Crop lettuce Expected yield (lbs of production/ acre) 48,000 Crop nitrogen 'need' to meet expected yield (lbs of Nitrogen per acre) 140 Total N applied to field (lbs/ac) Dry & Liquid Fertilizers 180 Foliar N fertilizers Other N fertilizers Available N from recent organic amendments TOTAL N APPLIED (per acre) 180 Soil Nitrogen Credits Residual soil NO3-N In-season soil organic N mineralization NO3-N in irrigation water TOTAL N CREDITS (per acre) Total N Credits and Applications: Crop N needs: Balance Ratio Recommended N

50 Crop example: Lettuce CROP NITROGEN DEMAND PROTOTYPE NITROGEN BUDGET WORKSHEET Crop lettuce Expected yield (lbs of production/ acre) 48,000 Crop nitrogen 'need' to meet expected yield (lbs of Nitrogen per acre) 140 Total N applied to field (lbs/ac) Dry & Liquid Fertilizers 180 Foliar N fertilizers Other N fertilizers Available N from recent organic amendments TOTAL N APPLIED (per acre) 180 Soil Nitrogen Credits Recommended N Residual soil NO3-N 40 In-season soil organic N mineralization 20 NO3-N in irrigation water 10 TOTAL N CREDITS (per acre) 70 Total N Credits and Applications: Crop N needs: Balance Ratio

51 Crop example: Lettuce CROP NITROGEN DEMAND PROTOTYPE NITROGEN BUDGET WORKSHEET Crop lettuce Expected yield (lbs of production/ acre) 48,000 Crop nitrogen 'need' to meet expected yield (lbs of Nitrogen per acre) 140 Total N applied to field (lbs/ac) Dry & Liquid Fertilizers 180 Foliar N fertilizers Other N fertilizers Available N from recent organic amendments TOTAL N APPLIED (per acre) 180 Soil Nitrogen Credits Recommended N Residual soil NO3-N 40 In-season soil organic N mineralization 20 NO3-N in irrigation water 10 TOTAL N CREDITS (per acre) 70 Total N Credits and Applications: 250 Crop N needs: 140 Balance 110 Ratio 1.80

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53 N fertilization scenarios

54 Processing tomato scenario: Smith Block lb N/acre is typical N uptake at this yield level, not the critical N uptake

55 Processing tomato scenario: Smith Block 5 Current fertilization practices recognize that there are significant nonfertilizer contributions

56 Processing tomato scenario: Smith Block 5 25 * 0.23 * 6PPM = 35 lb NO 3 -N

57 Processing tomato scenario: Smith Block 5 Crop residue effects probably minor, but not fully reflected in the soil test

58 Processing tomato scenario: Smith Block lb N applied; soil test will not reflect all the N mineralized by spring. During the tomato season N release likely to be minor

59 Processing tomato scenario: Smith Block 5 Olsen P is high, therefore P fertilizer need is minimal Soil NO 3 -N test probably underestimates residual NO 3 -N after dry winter Higher than normal soil organic matter suggests significant N contribution ( 1.3% OM * 30 lb N/% OM = 39 lb N )

60 Processing tomato scenario: Smith Block 5 From P fertilizer in transplant water Fertigation amount could be adjusted (probably downward) depending on post-transplant residual soil NO 3 -N lb N/acre Preplant N At-transplanting N 10 Sidedress N Fertigated N 180 Foliar N Total seasonal N application (lb/acre) 190 In-season monitoring? Residual soil NO 3 -N could be very useful in this situation (substantial fall soil NO 3 -N, fall amendment application) Full bloom stage leaf total N??

61 Processing tomato scenario: Smith Block 5 CROP NITROGEN DEMAND PROTOTYPE NITROGEN BUDGET WORKSHEET Crop tomato Expected yield (lbs of production/ acre) 120,000 Crop nitrogen 'need' to meet expected yield (lbs of Nitrogen per acre) 280 Total N applied to field (lbs/ac) Dry & Liquid Fertilizers 190 Foliar N fertilizers Other N fertilizers Available N from recent organic amendments TOTAL N APPLIED (per acre) 190 Soil Nitrogen Credits Recommended N Residual soil NO3-N 40 In-season soil organic N mineralization 40 NO3-N in irrigation water 35 TOTAL N CREDITS (per acre) 115 Total N Credits and Applications: 305 Crop N needs: 280 Balance 25 Ratio 1.09???

62 Processing tomato scenario: Smith Block 5 CCA respondents at the Fresno meeting : lb N/acre Low 25% Mean High 25% Preplant N At-transplanting N Sidedress N Fertigated N Foliar N Total seasonal N application N balance N ratio

63 Cantaloupe scenario: Jones Block B-3 Planting date May 10, 2014 Planting method Seeding Irrigation technique drip Realistic yield goal 1,100 cartons/acre (22 tons/acre) Crop N uptake requirement (lb N/acre) 170 Seasonal transpiration (inches) 12 Irrigation water NO 3 -N (PPM) 1 Typical seasonal N fertilization rates in the area Background information : Field location Merced County Prior crop broccoli Residue N left by prior crop (lb/acre) 200 Residue %N (dry weight basis) 3.5 Date of residue incorporation March 10, 2014 Date of soil sample April 15, 2014 Soil amendments applied none Soil analysis: Organic matter NO 3 -N Phosphorus (PPM) Exchangeable K Sample ID ph (%) (PPM) Bray Olsen PPM Soil texture Jones Block B clay loam

64 Cantaloupe scenario: Jones Block B-3 Planting date May 10, 2014 Planting method Seeding Irrigation technique drip Realistic yield goal 1,100 cartons/acre (22 tons/acre) Crop N uptake requirement (lb N/acre) 170 Seasonal transpiration (inches) 12 Irrigation water NO 3 -N (PPM) 1 Typical seasonal N fertilization rates in the area Minimal irrigation N credit Background information : Field location Merced County Prior crop broccoli Residue N left by prior crop (lb/acre) 200 Residue %N (dry weight basis) 3.5 Date of residue incorporation March 10, 2014 Date of soil sample April 15, 2014 Soil amendments applied none Soil analysis: Organic matter NO 3 -N Phosphorus (PPM) Exchangeable K Sample ID ph (%) (PPM) Bray Olsen PPM Soil texture Jones Block B clay loam

65 Cantaloupe scenario: Jones Block B-3 Planting date May 10, 2014 Planting method Seeding Irrigation technique drip Realistic yield goal 1,100 cartons/acre (22 tons/acre) Crop N uptake requirement (lb N/acre) 170 Seasonal transpiration (inches) 12 Irrigation water NO 3 -N (PPM) 1 Typical seasonal N fertilization rates in the area Background information : Field location Merced County Prior crop broccoli Residue N left by prior crop (lb/acre) 200 Residue %N (dry weight basis) 3.5 Date of residue incorporation March 10, 2014 Date of soil sample April 15, 2014 Soil amendments applied none Soil analysis: High-N broccoli residue will mineralize quickly; much of the contribution is reflected in the soil sample Organic matter NO 3 -N Phosphorus (PPM) Exchangeable K Sample ID ph (%) (PPM) Bray Olsen PPM Soil texture Jones Block B clay loam

66 Cantaloupe scenario: Jones Block B-3 Planting date May 10, 2014 Planting method Seeding Irrigation technique drip Realistic yield goal 1,100 cartons/acre (22 tons/acre) Crop N uptake requirement (lb N/acre) 170 Seasonal transpiration (inches) 12 Irrigation water NO 3 -N (PPM) 1 Typical seasonal N fertilization rates in the area Background information : Field location Merced County Prior crop broccoli Residue N left by prior crop (lb/acre) 200 Residue %N (dry weight basis) 3.5 Date of residue incorporation March 10, 2014 Date of soil sample April 15, 2014 Soil amendments applied none Soil analysis: No preplant N needed, but some may come with preplant P Low soil organic matter limits its contribution ( 0.7% OM * 30 lb/% OM = 21 lb N ) but some additional mineralization likely from crop residue Organic matter NO 3 -N Phosphorus (PPM) Exchangeable K Sample ID ph (%) (PPM) Bray Olsen PPM Soil texture Jones Block B clay loam

67 Cantaloupe scenario: Jones Block B-3 From preplant P fertilizer lb N/acre Preplant N 15 Sidedress N Fertigated N 50 Foliar N Total seasonal N application 65 High soil residual NO 3 -N minimizes fertigation requirement In-season monitoring? Residual soil NO 3 -N?? Early fruiting stage leaf total N??

68 Cantaloupe scenario: Jones Block B-3 CROP NITROGEN DEMAND PROTOTYPE NITROGEN BUDGET WORKSHEET Crop cantaloupe Expected yield (lbs of production/ acre) 44,000 Crop nitrogen 'need' to meet expected yield (lbs of Nitrogen per acre) 170 Total N applied to field (lbs/ac) Dry & Liquid Fertilizers 65 Foliar N fertilizers Other N fertilizers Available N from recent organic amendments TOTAL N APPLIED (per acre) 65 Soil Nitrogen Credits Recommended N Residual soil NO3-N 100 In-season soil organic N mineralization 20 NO3-N in irrigation water 0 TOTAL N CREDITS (per acre) 120 Total N Credits and Applications: 185 Crop N needs: 170 Balance 15 Ratio 1.09???

69 Cantaloupe scenario: Jones Block B-3 CCA respondents at the Fresno meeting : lb N/acre Low 25% Mean High 25% Preplant N Sidedress N Fertigated N Foliar N Total seasonal N application N balance N ratio

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