Evaluating automated precision fertigation effect on

Evaluating automated precision fertigation effect on tomato yield and quality

Isaya Kisekka Assistant Professor Irrigation Engineering and Agricultural Water Management Departments of LAWR and BAE

Outline • Justification

• Objectives

• Methods

• Results from 2018 growing season

• Proposed research for 2019 season

Justification of Proposed Research

• Constrained water supplies (Policy [SGMA] or Hydrology).

• Irrigated Lands Regulatory Program (ILRP) : Nitrate leaching.

• There is a need among growers to optimize yield and quality to enhance net profitability while minimizing nitrate leaching to groundwater.

• Can precision fertigation help processing tomato growers to improve yields and quality by applying precise amounts of fertilizers at the right time and right place?

Presenter

Presentation Notes

Can precision irrigation and fertigation help us to achieve: Higher yields Higher soluble solids Conc Minimize environmental impact/nitrate leaching Enhance overall net profitability

Objectives 1.Evaluate the effect of high frequency low concentration (HFLC)

fertigation and low frequency high concentration (LFHC) fertigation on yield and quality of processing tomatoes.

2.Evaluate the effect of different deficit irrigation strategies (Regulated deficit- 75% after ripening, Sustained deficit- 75%ET) on yield and fruit quality.

Presenter

Presentation Notes

OH LORD JESUS!�We can use precision fertigation to implement HF fertigation?

Precision irrigation and fertigation treatments

• T1: Full irrigation-HFLC fertigation 100% ET • T2: Full irrigation-LFHC fertigation 100% ET • T3: Regulated deficit-HFLC fertigation 100%ET before ripening –

75% after ripening • T4: Regulated deficit-LFHC fertigation 100%ET before ripening –

75% after ripening • T5: Sustained deficit-HFLC fertigation 75%ET • T6: Sustained deficit-LFHC fertigation 75%ET

Estimating fertigation injection rates

Start water

Start solute

End solute

1 0 2 3 4 5 6

Time (h)

Implementation of automated precision fertigation

Strategy A Strategy B

End water

Start Water +solute

End solute

1 0 2 3 4 5 6

Time (h)

Which one of the two is a better fertigation management strategy?

End water

Before Fertigation

End Fertigation

Precision flow meter connected to irrigation controller can be monitored remotely

Monitor when flow is outside of expected range: Could mean clogging or leakage

Optimum flow

HFLC Fertigation

LFHC Fertigation

Fertigation Implementation

Date HFLC

N (lbs/acre) LFHC

N (lbs/acres) 01-May 07-May 10 14-May 10 30 21-May 10 28-May 10 30 01-Jun 10 07-Jun 10 14-Jun 10 30 21-Jun 10 28-Jun 10 30 01-Jul 10 07-Jul 10 14-Jul 10 30 21-Jul 10 28-Jul 10

01-Aug 10 30 07-Aug 10 14-Aug 10 21-Aug 10

Total 180 180

Presenter

Presentation Notes

Nutrient uptake is slow until fruit set begins, and then accelerates significantly; from early fruit set until fruit begin to ripen nutrient uptake remains relatively constant at approximately 5 lb N, 0.5 lb P and 6 lb K per acre per day.

Block 1 Block 2 Block 3 Block 4

4 1 5

6 3 2

5 2 3

4

3 5 6

2 4 1 1 6

2 1 5

4 3 6

Head control fertigation and pressure control

Evapotranspiration measurement

Brix measurement

Yields from the 2018 processing tomato season

Treatment Yield (ton/acre) SSC ( Brix o )

T1: HFLC 100% ET 71.8 a* 3.70 b

69.2 ab 3.85 ab

73.1 a 3.95 ab

64.2 abc 3.85 ab

59.5 bc 4.55 a

57.4 c 4.58 a

T2: LFHC 100% ET

T3: HFLC 100 - 75% ET

T4: LFHC 100 - 75% ET

T5: HFLC 75% ET

T6: LFHC 75% ET

Soil moisture (40 -50 cbar) monitoring and brix measurement of ripening fruit could help guide end-ofseason irrigation management

Presenter

Presentation Notes

Recent research has documented that after a tomato fruit reaches the ‘pink’ stage of maturity (color change on 30% of the fruit surface), its SSC is essentially unaffected by irrigation management; regardless of subsequent soil moisture stress, SSC of that fruit will slowly decline (typically about 0.2o brix by harvest). Therefore, in order to have a significant influence on overall SSC, some moisture stress must be imposed while the majority of fruits are still green.

Evapotranspiration (Crop water use)

ET measured using Tule ET sensor

0.00

5.00

10.00

15.00

20.00

25.00

4/30/18 5/20/18 6/9/18 6/29/18 7/19/18 8/8/18 8/28/18

Cum

ulat

ive

ET (i

n)

Tule ET

ET and Applied Irrigation

0.00

5.00

10.00

15.00

20.00

25.00

4/30/18 5/20/18 6/9/18 6/29/18 7/19/18 8/8/18 8/28/18

Cum

ulat

ive

ET/A

pplie

d Irr

igat

ion

(in)

Tule ET

Applied Irr

Effect of deficit irrigation and fertigation frequency on canopy cover

0

10

20

30

40

50

60

70

80

90

100

0 20 40 60 80 100 120

CC

(%)

DAP

T1 T2 T3 T4 T5 T6

Most of the effects of deficit irrigation on canopy cover occurred in the last quarter of the season. Probably explains lack of significant difference between full irrigation and regulated deficit irrigation (100 – 75 % ET) Effect of sustained deficits on CC is substantial should be avoided.

Effect of deficit irrigation and fertigation frequency on LAI

Sustained deficit irrigation affected LAI. Even under sustained deficit irrigation, high frequency fertigation appeared to have maintained high LAI.

0

2

4

6

8

10

12

0 20 40 60 80 100 120

LAI

DAP

HFLC,100ET LFHC,100ET LFHC HFLC LFHC,75ET HFLC,75ET

Remote sensing of canopy nitrogen content using red edge

Block 1 Block 2 Block 3 Block 4

4 1 5

6 3 2

5 2 3

4

3 5 6

2 4 1 1 6

2 1 5

4 3 6

Nitrate leaching was measured using pore samplers at 6.7 ft

Thank you!

Isaya Kisekka Assistant Professor Irrigation Engineering and Agricultural Water Management University of California Davis Phone: 530-379-9549 E-mail: [email protected]

mailto:[email protected]�

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Evaluating automated precision fertigation effect on