Update on AirJection Irrigation Research

Transcription

1 Update on AirJection Irrigation Research By Dave Goorahoo, Diganta D. Adhikari, David Zoldoske, & Florence Cassel S. California State University Fresno, Center for Irrigation Technology Plant Science Department

2 OUTLINE Rationale Objectives Related Work from 2000 to Present- Some Results Conclusions and Future Research

3 Factors that will affect California Agriculture in the FUTURE Water People Environment Land

4 Research at CIT on Water Use Efficiency Basic e.g. Moisture Sensor Testing Applied- e.g. Optimizing Irrigation Efficiency

5 Plants Depend on Soil ANCHORAGE MOISTURE NUTRIENTS SUFFICIENT AIR AND OXYGEN FOR ROOT SYSTEM

6 Rationale for Air Injection Studies Significance of root zone air Well aerated soil favors root respiration O 2 essential for microbial activity Sufficient O 2 Nitrification and Ammonification Shortage of O 2 Denitrification O 2 also needed for large groups of soil fauna e.g. insects and earthworms Hence, adding air to the root zone could result in less stress overall on the plants.

7 Air versus Water in Root zone Plants need water and dissolved nutrients Respiration in plants depends on soil oxygen Roots need at least 10% by volume air space in soil Hence, some compromise of a mix between air and water in the root zone is essential for optimum plant growth.

8 Need to Deliver O 2 to Root Zone Over sixty five years ago, Durell (1941) wrote, a study of suitable oxygen carriers, which could be applied as fertilizer, and which would release oxygen slowly to the soil during the growing season, may be worthwhile Durell, W. D. (1941). The effect of aeration on growth of the tomato in nutrient solution. Plant Physiol. 16,

9 How to have adequately water-aerated root zone? Consider a system that combines sub surface drip irrigation (SDI) tape and an air injection system that mixes air with the water delivered within the root zone- AirJection Irrigation Thefluidmixturedeliveredtotherootzoneof the plant is best characterized as an air-water slurry.

10 Water under pressure enters the injector inlet and is constricted in the injection chamber (throat) => velocity increase. Increased velocity results in a decrease in pressure below atmospheric in the chamber. Air is drawn through the suction port and be entrained into the water stream.

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12 OVERALL OBJECTIVES Major goal is to evaluate the feasibility of injection of ambient air into a subsurface drip tape irrigation system, (AirJection Irrigation), as a best management practice for crop production. Test technology on many crops as possible.

13 Related Work from 2000 to Present 2000: Pilot study at CIT with peppers- findings from the 2000 CSU-Fresno study justified follow-up fieldwork on larger plots approaching commercial scale.

14 Current Research CIT researchers have been funded as part of the Governor s Buy California s Initiative, to work with commercial vegetable growers in evaluating the feasibility of the air-injection system in crop production systems utilizing SDI. Crops examined in : honeydews, cantaloupes, tomatoes, peppers, sweet corn, broccoli and strawberry.

15 Specific Objectives of Recent Studies Determine the impact of air injected into water delivered through SDI on yield and quality of crops Determine if any increased growth of plants and root masses occurred Evaluate the SDI- air system for the soil types where crops are grown

16 Procedures Experimental subplots on commercial production, with alternating rows of SDIair and SDI no air (Control). Pre-Plant Soil sampling Crop Growth and Irrigation Monitoring Harvest and Yield Data Collection Photosynthesis and transpiration Plant Height and width measurements Root and Shoot Post Harvest

17 Pilot Study Design

18 Single injector for each drip line.

19 Relatively larger injector servicing 24 drip lines.

20 There was a 14% increase due to Air injection in the number of Honeydews harvested in 2003 Figure 1:Total Number of Melons in Air vs Water Plots Number Of M elons Air Water (South) (North) Replicates

21 There was a 16% increase due to Air injection in the weight of Honeydews harvested in 2003 Figure 2: Total Weights of Melons in Air vs Water Plots W e ight O f M e lons (K gs.) Air Water (South) (North) Replicates

22 2003 Honeydews Result No significant difference in Brix level of melons Yield data projected increase of $260 to $350 per acre for the farmer depending on the wholesale price of melons which can range from $3 to $4 per box.

23 Tomatoes In tomatoes grown on 20 acre plots with drip tape run lengths of approximately 300m, we have observed that for the air treated plants there were greater yields from the plants located at the head of the drip line versus the plants down at the tail. For tomato crop, there may have been earlier fruit maturity for the air treated plants.

24 Strawberries Results 18.3% increase in #1 Grade fruit in the Aerated plot vs. the Control plot. 6.9% increase in #2 Grade fruit in the Aerated plot vs. the Control plot. 33.7% increase in Freezer Grade fruit in the Aerated plot vs. the Control plot.

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27 Root Dry Weights (2005) Avg. Weight (g) Sweet corn Broccoli AirJection Water Only % Difference 16% 12%

28 Photosynthetic rate in Pepper 18 Photosynthesis rate in Air vs. Water Treatments( 2004 SDI-CIT double run). Pepper Trial. PN ( umol m^-2 s^ Air Water DAT

29 Transpiration rate Soil Respiration

30 Optimize water and nutrient use in vegetables Others Conventional Farming Others Fertilizer and Sub-surface Drip Irrigation AirJection Organic Farming Crops N Rates

31 Cost Benefits The extra costs involved with venturi based system are simply the cost of an air injection units. Coupling of air injection into an SDI system attracts a capital cost of approximately US$ per hectare (Bhattarai et al., 2005)

32 Environmental Benefits Besides the monetary benefits, the ecological benefits associated with AirJection include improvements in nitrogen use effciency, increased activity of soil microbes, and reduced deep drainage of irrigation water. The conservation of scarce water resources will gain favor for sustainable irrigated agriculture

33 Conclusions Air Jection Irrigation systems can increase root zone aeration and add value to grower investments in SDI. The increase in yields and potential improvement in soil quality associated with the root zone aeration implies that the adoption of the SDI-air injection technology primarily as tool for increasing crop productivity.

34 Future Work Because the air injection system with the venturi devices uses ambient air, there exists the potential to use this system on organic farms. Establish long term research plots (LTRP) to investigate the effect of AirJection irrigation on soil physical, chemical and biological properties.

35 Future Work Cont d In addition to yield and fruit quality, future studies would focus on the impact of air injection on water and fertilizer use efficiency, soil respiration, soil salinity, soil microbial activity, insect/pest resistance and rooting characteristics of the various crops.

36 THANK YOU! Any Questions? Dave Goorahoo Plant Science Department Center for Irrigation Technology California State University, Fresno E. San Ramon Ave MS AS 72 Fresno CA Phone: ; Fax: