Surface Strategies on Alfalfa for Recharge Alfalfa and Forage Virtual Field Day September 23, 2020

Khaled Bali*, Brady Holder*, Luke Paloutzian*, Dong Wang**, Sultan Begna**, Umair Gull***, Helen Dahlke***, and Dan Putnam*** *[email protected] http://kare.ucanr.edu/ *UCANR- UC Kearney Agricultural Research and Extension Center, Parlier, CA ** USDA-ARS, Parlier, CA *** UC Davis, Davis, CA Irrigation: Controlled amount of water is applied to plants at specific intervals Irrigation Methods in California: 1- Surface irrigation (flood or gravity): - Border strip (flat) irrigation (slope 0.1-0.2%) - Furrow irrigation (slope) - Basin irrigation (zero slope) 2- Sprinkler Irrigation (various types) 3- Low volume/ (various types) - Surface drip and Subsurface drip Source: California Department of Top field crops in California

Alfalfa 1,020,000 acres in 2009 670,000 acres in 2018 About 34% decline

Source: CDFA : California Agricultural Statistics Review 2018-2019 TRENDS IN CALIFORNIA IRRIGATED AGRICULTURE California Agriculture Challenges Gravity Sprinkler Drip Subsurface 90 81 Regulations, water, labor, high 80 production costs, etc 70 Approximately 30% decline in 60 field crops between 2009 and 2018 49 and increase in permanent crops 50 43

40 Field Crops Vegetables Orchards Vineyards 38 30 80

30 Irrigated Area (%) Area Irrigated 70 67 18 20 15 13 60

10 7 50 3 0 1 41 37 0 40 30 30 1970 1973 1976 1979 1982 1985 1988 1991 1994 1997 2000 2003 2006 2009 2012 2015 2018 30 Time (year) 21 20 15 15 Percent Irrigated Area (%) AreaIrrigated Percent 12 11 14 Source: Irrigation Survey 2018, (DWR-UCD) 10 6 0 1972 1980 1991 2001 2010 2016 Time (Year) Typical 80-160 acre alfalfa field in CA - Flow rate, Q: 4- 20 cfs (1cfs ~449 gpm) - Border length: 1,200-2,500 ft - Border width: 60-300 ft - Slope: ~ 1-2 ft/1000 ft - Average depth applied per irrigation 3-6 in

- Goal with surface irrigation: refill profile - Minimize losses (runoff and deep percolation) Surface Irrigation Efficiency Applied water = Root zone storage + runoff + deep percolation

Root zone storage (A)

d L Subsurface z (B)

Deep percolation (C) Application Efficiency (AE)= A/(A+B+C)

To achieve higher efficiency, reduce B and/or C Intermittent on Alfalfa One low flow (Q) and long (T) surface irrigation event per week (Jan- April) Applied water = Root zone storage + runoff + deep percolation Root zone storage (A) ~ ETo d (between recharging events) L z Surface runoff (B) = 0 Subsurface Deep percolation (C)

Groundwater Recharge Efficiency = C/(A+B+C)

To achieve high GW recharge efficiency, eliminate B and minimize A Intermittent Groundwater Recharge on Alfalfa UC Kearney Agricultural Research and Extension Center, Parlier, CA 2019 feasibility study on selected borders 3rd year alfalfa stand

2020 replicated study on 24 borders 2nd year alfalfa stand 2019 Soil: Hanford sandy loam

Drainage class: Well drained Capacity of the most limiting layer to transmit water Ksat: High (1.98 to 5.95 in/hr) 2020 Surface Irrigation and Groundwater Recharge on alfalfa (2019- 3rd year stand)

- Utilization of existing surface irrigation systems on alfalfa for GW recharge. - Up to 16”/week recharge with intermittent flooding with no significant impact on alfalfa yield

- O2 levels in rootzone above the critical 5% needed to maintain healthy root system Data from UC Kearney Research and Extension Center (2019; ~53 inches of recharge in 6 irrigation events)

%O2 level

Applied water (in)

5% O2 level Surface Irrigation and Groundwater Recharge on alfalfa (2020- 2nd year stand) - Irrigation treatments during the growing season (April-November): - Full irrigation and after August cutting - GW recharge treatment: Intermittent winter flooding and no flooding - Replicated three times (yield, O2 level in soil, moisture content, ETa, etc) Surface Irrigation and Groundwater Recharge on alfalfa (2020- 2nd year stand)

- Utilization of existing surface irrigation systems on alfalfa for GW recharge. - Up to 14”/week recharge with intermittent flooding with no significant impact on alfalfa yield - Data from UC Kearney Research and Extension Center (2020; ~80 inches of recharge in 10 irrigation events)

2020 KARE Alfalfa Flooding Events 16.00

14.00

12.00

10.00 Applied water (in)

8.00

6.00

Water Applied (in) 4.00

2.00

0.00 2/20/2020 2/27/2020 3/5/2020 3/12/2020 3/17/2020 3/19/2020 3/23/2020 3/26/2020 3/30/2020 4/2/2020 Surface Irrigation and Groundwater Recharge on alfalfa (2020- 2nd year stand)

- Utilization of existing surface irrigation systems on alfalfa for GW recharge. - Up to 14”/week recharge with intermittent flooding with no significant impact on alfalfa yield

- O2 levels in rootzone above the critical 5% needed to maintain healthy root system Data from UC Kearney Research and Extension Center (2020; ~80 inches of recharge in 10 irrigation events) Average of O2 Sensors Across Treatments Flood Event East Flood 2/9/2020Applied 0:00 2/19/2020 water 0:00 (in)2/29/2020 0:00 3/10/2020 0:00 3/20/2020 0:00 3/30/2020 0:00 4/9/2020 0:00 4/19/2020%O 0:002 level Middle Flood 16.00 25 West Flood 14.00 East Dry 20 Middle Dry 12.00 West Dry

10.00 15

8.00 %O2 6.00 10

Water Applied (in) 4.00 55% 2.00 5% O2 O2 level 0.00 0

level

2/9/2020 3/2/2020 3/4/2020 3/6/2020 3/8/2020 4/1/2020 4/3/2020 4/5/2020 4/7/2020 4/9/2020

2/11/2020 2/13/2020 2/15/2020 2/17/2020 2/19/2020 2/21/2020 2/23/2020 2/25/2020 2/27/2020 2/29/2020 3/10/2020 3/12/2020 3/14/2020 3/16/2020 3/18/2020 3/20/2020 3/22/2020 3/24/2020 3/26/2020 3/28/2020 3/30/2020 4/11/2020 4/13/2020 4/15/2020 4/17/2020 4/19/2020 4/21/2020 4/23/2020 Axis Title Surface Irrigation and Groundwater Recharge on alfalfa (2020- 2nd year stand)

- Continuous flooding: reached 5% O2 level in 5-7 days

%O2 level control (no flooding) %O2 level continuous flooding

25 %O2 for Continuous Flooding Sensors S e n… 20

15 %O2 10 5% O2 level 5

0 3/12/2020 3/17/2020 3/22/2020 3/27/2020 4/1/2020 4/6/2020 4/11/2020 4/16/2020 4/21/2020 Surface Irrigation and Groundwater Recharge on alfalfa (2020- 2nd year stand) Deficit irrigation on selected borders after Aug. 2019 cutting Flooding events on selected borders Summary

Practical options for groundwater recharge (alfalfa) - Deficit irrigation on alfalfa to address water shortages is feasible (Water transfer, drought, SGMA, and limited water supplies, etc) with minimal impact on alfalfa stand KARE - Great potential for utilizing existing surface irrigation infrastructure for groundwater recharge (to address SGMA) on alfalfa - Alfalfa fields with the proper soil type (medium to high rates) are ideal locations for GW recharge in California (less potential issues with nitrate as compared to other crops) - Very little modification is needed to the existing surface irrigation system and no need for dual irrigation systems (for irrigation and surface system for GW recharge) - Modernization of irrigation districts or flood water delivery to farms is needed (SSJID- Pressurized, Turlock ID- Active control, Oakdale ID- Storage and automated control, CVWD- GW recharge) Thank You