Irrigation Management Effects on Soil Fertility and Environmental Impacts

Mike Cahn, Irrigation and Water Resources Advisor, UCCE Monterey Water Management Needs to be Factored into Soil Fertility Management ƒCostly to build up soil fertility in organic systems ƒPoor water management can lead to loss of nutrients (mostly N and P) ƒPotential water quality impairments from sediment and nutrients in run-off and leachate from organic fields Organic Liquid Fertilizers* (0.1 – 7% N)

Activate, Micronized Fertall Liquid Iron Aqua Power Liquid Fish Fertall Liquid MB Azomite Fertall Liquid Zinc Biolink Organic 0/5/5 HFPC Hydrolyzed Fish Powder Biolink Organic 5/5/5 Maxicrop Kelp Extract Biolink•5-1-1 Organic liquidMicronutrients costs $9.6Micro Hume per lb of N Cranford's Micronized Compost Micro Phos Diamond•13-0-0 K Solution dry grade Gypsumcosts $4 Multi-Ke-Min per lb of N Earth Juice Bloom 0/3/1 Neptune's Harvest Liquid Fish Earth Juice Catalyst Nutra Min Earth Juice Grow 2/1/1 Omega 1/5/5 Eco-Hydro•A substantial fish Liquid amountOmega 6/6/6of the N Eco-Nereo Kelp and Humic Acids Phytamin 800 Eco-Polycould 21 mciro be Shrimp in mineralSolubor form Boron (12-50%) Feather Tea Sulfate of Potash, Diamond K Soluble Fertall Liquid Chelate Calcium *Organic Material Research Institute, National Organic Program Compost sources of Nitrogen

• $1.5 - $2 per lb of N (1.4% N product) Cover Crops as a Source of Nitrogen

•100 – 150 lb of N/acre in above ground Biomass •Production costs of $150 – $200/acre for a winter cover crop •$1-2 per lb of Nitrogen •Roughly 30% of cover crop N becomes available for subsequent crop Comparison of Organic and Conventional Onions (Hollister, 1996)

80

70

60 Conventional 50

40

30 20 ppm 20 Soil ppm NO3-N Organic PSNT 10 threshold 0

May May Jun Jun Jul Jul Jul Aug Smith, 1996 Mineral Nitrogen in an Organic Processing Tomato Field (Sutter Co, 2001) 16 14 12 10

8 6 4 2 Mineral Nitrogen (ppm) Nitrogen Mineral 0 3/1/01 4/1/01 5/1/01 6/1/01 7/1/01 8/1/01 Date Winter Grain/Legume Cover Crop Winter Legume Cover Crop Winter Fallow Suction Lysimeter

How susceptible is nitrate to leaching? Estimated Nitrogen Losses due to Leaching (King City July 25-July 29)

Soil NO3‐N Nitrogen Management Applied Moisture concentration loss by Treatment Water1 Crop ET Storage Percolation in leachate leaching ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ inches ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ ppm lb/acre BMP 0.8 0.6 0.0 0.3 173.9 11.2 Grower 1.4 0.6 ‐0.1 0.9 178.4 37.3 Irrigation Management is Key to Maintaining N in the Rootzone

ƒHigh Distribution Uniformity ƒSchedule irrigations to match water requirements of crop ƒMinimize scheduling and operational errors Is drip irrigation the answer to minimizing nitrogen losses?

•Possible to irrigate more frequent and less per irrigation •Possible to fertigate some liquid fertilizer materials Potential Leaching of Nitrate Under Drip Irrigation

Seed line Seed line Drip Tape

2 %H O 4 2 24 6 28 32 8 36 40 44 10 48

Depth (inches) 12

14

16

0 2 4 6 8 10121416 Bed Width (inches) Residual Nitrate in Soil Profile of a Conventional Vegetable Field before and after 3 irrigations

0 168 lb of N/acre 45 lb of N/acre

10 120 lb of N/acre Initial Nitrate Level 0.75 inches of applied water 1.5 inches of applied water 20 2.25 inches of applied water Depth (inches) Depth

30

0 10203040

Soil NO3-N (ppm) Management of Drip in Romaine Lettuce

14 18 n = 66 n = 59 12 16 14 10 12 8 10 6 8 6 4 4 Number of Irrigations Number of Irrigations 2 2 0 0 0.0 0.5 1.0 1.5 2.0 2.5 01234567 Amount of Applied Water (inches) Irrigation Interval (days) Additional Challenge with Drip: Dry bed shoulders and furrows may reduce N mineralization and crop use of nutrients

Depends on: •Bed width •Number and depth of drip lines •Soil type •Irrigation scheduling Environmental Impacts of Water Management Run-off Carries Sediment and Nutrients into Surface Water Eutrophication of Surface Water

Possible TMDL Concentration targets: P < 0.1 ppm

NO3-N < 10 ppm Total P concentration in Run-off is linked to the Sediment concentration

10 R2=0.77 8 Mocho silt loam Metz complex 6 Rincon clay loam Salinas clay loam 4 Chualar loam Chualar sandy loam Total P (mg/L) P Total 2 Regression Line

0 0 1000 2000 3000 4000 Total Suspended Solids (mg/L) Soil P can be at high levels in Organic Fields

160 Organic Fields 140 Conventional Fields 120 100 50 ppm threshold 80 for lettuce 60 Olsen P (ppm) Olsen 40 20

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Organic Matter (%)

Hartz 2008 Phosphate loss by run-off and leaching

0.5 4 Organic Fields Organic Fields Conventional Fields Conventional Fields 0.4 3

0.3 2 0.2 1 0.1 Phosphate in Run-off (ppm) Phosphate in Leachate (ppm) Leachate in Phosphate 0 0.0 0 20 40 60 80 100 120 140 160 0 20 40 60 80 100 120 140 160 Olsen-P (ppm) Olsen-P (ppm)

Hartz 2008 Irrigation management is critical to minimizing surface water impairments

Minimize run-off in sprinkler and furrow systems

Drip irrigation is ideal for minimizing surface run-off Other measures to treat irrigation run-off

Vegetated Ditches Retention Ponds

Vegetated Treatment Systems Managing Storm Water Run-off Cover Crops Reduced Biomass Cover Crops Nutrient and Sediment Concentration in Storm Run-off

Total Suspended Total

Winter Treatment Solids Turbidity Total-P Kjeldahl N NO3-N ppm NTUx ------ppm ------bare (control) 1419 4449 4.4 8.0 7.48 full cover crop 342 917 1.9 3.0 0.37 furrow bottom cover crop 841 2377 3.3 5.7 2.29 x. low NTU (Nephelometric turbidity units) indicate less turbidity Summary Water management is critical to maintaining soil fertility and minimizing water quality impacts from organic farms

9Nitrogen is often a limiting and a costly nutrient that can be lost through leaching

9Sediment, phosphorus, and nitrogen carried in irrigation run-off can impair the quality of surface water

9Controlling storm run-off is a more difficult challenge than reducing irrigation run-off, but cover crops and vegetation can be effective strategies for minimizing impacts to water quality Thank you!