Management of Lettuce. UCCE, Monterey County Tim Hartz and Tom Bottoms, Plant Sciences, UC Davis

Transcription

1 Irrigation effects on Nitrogen Management of Lettuce Michael Cahn Richard Smith Barry Farrara Aaron Heinrich Michael Cahn, Richard Smith, Barry Farrara, Aaron Heinrich UCCE, Monterey County Tim Hartz and Tom Bottoms, Plant Sciences, UC Davis

2 Quick Nitrate Test: Soil nitrate status (2 ppm NO 3 N = 7 to 8 lbs of N/acre)

3 21 Nitrogen Fertilizer Trials 3 Standard BMP lbs N/A Lbs N/A Difference 66 N =$4/A Ave Field

4 Commercial Yield % of Grower Box xes/acre e GR BMP Avg Field

5 How much does irrigation management matter for optimizing nitrogen fertilizer?

6 Lbs of N lost by leaching depends on soil nitrate concentration and drainage Soil Nitrate N N Drainage Nitrate N leached content (ppm) (inches) (lbs of N/acre)

7 Total Water Applied to Lettuce 3 Applied Water (in nches) Avg = 12.6 inches Field Number

8 29 DAP 41 DAP 8 Ca anopy Cov ver (%) DAP Crop ET = Crop ET = 65 DAP 1to35inches to 7.5 inches Days after Planting

9 Applied Water as Percentage of 35 Crop ET Ap pplied Wa ater (% Crop ET) Avg Applied Water = 176% of Crop ET Field Number

10 Applied Water and Crop ET (site 1) 8 7 Cumulative Applied Water (inches) Cumulative Crop ET (inches) Applied Water Crop ET DAP

11 Applied N and soil nitrate (site 1) 8 m Soil NO 3 -N pp Grower practice 6 BMP 4 2 lbs N/A DAP

12 Applied Water and Crop ET (site 3) plied Wat er (inches s) Cumu ulative Ap Applied Water Crop ET DAP Crop ET (inches) Cu umulative

13 Applied N and soil nitrate (site 3) (ppm) NO3-N soil Grower practice BMP 3 32 N/A lbs DAP

14 Pre-thinning Water Applied to Lettuce 3 Water (in nches) Applied 25 Total Applied Water Pre-Thinning Water Avg prethinning water = 5.5 inches Field Number

15 Potential N losses during crop establishment: Evaporation and transpiration losses during first 2 weeks of a lettuce crop < 2 inches Crop and Germination Evaporation water Management losses amount N loss inches lb/acre Reduced irrigation Normal irrigation

16 First irrigation after thinning can contribute to N losses Crop ET is low Soil nitrate levels are often high Roots are concentrated in upper foot Irrigations amounts are often in excess of water holding capacity of soil

17 Amount of water applied during a single irrigation can contribute to nitrate losses establishment post thinning Irrigation method avg max avg max inches per irrigation sprinkler drip furrow

18 Factoring in Soil Water Holding Capacity in Irrigation Scheduling Available Water Holding Capacity for Various Soil Textures Soil Texture Field Capacity (3 cbar) Wilting Point (15 cbar) Available Moisture inches of water per foot of soil Sand Loamy Sand Sandy Loam Loamy Sand Silt Loam Sandy Clay Loam Sandy Clay Loam Clay Loam Silty Clay Loam Silty Clay Clay Problematic for irrigation scheduling of cool season vegetables

19 Soil Moisture Tensions > 3 cbars slows lettuce growth

20 Soil Texture, Water Holding Capacity, and Available Moisture Tension 3 kpa Tension 8 kpa Saturated Soil Soil Texture Saturated tension Volumetric Moisture Available Moisture Available Moisture kpa % % inches/foot % inches/foot 1 Silty clay Silty clay loam Loam

21 Low Distribution Uniformity increases Irrigation Requirement and Drainage

22 Average irrigation intervals in Lettuce average irrigation interval crop stage sprinkler drip furrow days pre thinning post thinning

23 Effect of irrigation interval on N management Treatment Irrigation interval (days) % Crop ET N fertilizer management 4 day 4 114% Quick N test 7day 7 154% Quick N test Grower Grower decision i Grower decision i Grower (7 days) (15%) decision

24 Soil Nitrate and Applied N of Irrigation Treatments So oil Nitrate- -N (ppm of N) Cumulative N fertiliz zer (lbs N/acre) 1 4-day interval 7-day interval Grower standard Days after planting

25 Did the irrigation treatments affect nitrate leaching? Suction Lysimeter

26 Estimated Drainage of Irrigation i Treatments Draina ge (Applied water - ET T) inches day 7 day grower Irrigation Interval

27 25 Estimated Nitrate Leaching Losses Nitrate-N N loss (lb/ /acre) day 7 day grower Irrigation Interval

28 Yield Summary of Irrigation Treatments Head Weight Plant population Yield Treatment Untrimmed Trimmed Marketable Diseased Marketable Biomass lb/head plants/acre lbs/acre 4 day day grower LSD.5 ns ns ns ns ns ns

29 What about leaching for salinity management? Adequate leaching usually occurs during preirrigation and stand establishment Leach Fraction > 3%, ECwater = ECsoil Irrigating more frequently (with drip) can offset some of the salinity effects on growth Do not apply N fertilizer before leaching events

30 Irrigation strategies for using nitrogen fertilizer efficently in lettuce Match irrigation schedule with crop ET to minimize nitrate leaching Assure that irrigation system has a high DU Minimize irrigation water for germination (< 3 inches) Avoid applying high amounts of water during a single irrigation (>.5 inch during prethinning, > 1 inch during post thinning) Avoid heavy irrigations after fertilizing